A method and system for evaluating and optimizing the propulsion performance of medium- and high-speed ship hulls

Abstract

The present invention provides a method and system for evaluating and optimizing the propulsion performance of medium- and high-speed ship types. By gradually initializing the flow field and performing iterative solutions, through multiple steps progressing step by step, a suitable initial flow field is provided for multi-level motion problems. The motions at each level are gradually released, enabling the coupled flow field of the ship and propeller to gradually stabilize and tend towards the final real flow field, ensuring a smooth transition of the flow field, the forces on the ship's hull, and the motion, and enhancing the robustness and convergence efficiency of the numerical calculation model. By establishing a method for adjusting the propeller rotational speed in self-propulsion calculations, a criterion for judging calculation convergence, a method for extracting calculation results, and a method for predicting the self-propulsion performance of a ship. By constructing an optimized method-driven medium- and high-speed ship type transformation, self-propulsion performance evaluation process, and optimization design process method, the problem of manual interaction required in the process and the inability to achieve full-process automation is solved, and the application effect of the optimization theory in the optimization design of medium- and high-speed ship types is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of computer simulation design, and particularly to a method and a system for evaluating and optimizing the propulsion performance of medium- and high-speed ship forms. Background Art

[0002] The ship's speed performance index is one of the core technical indicators that are highly concerned in the design and development of ship forms. At present, with the development of ship CFD technology and parametric modeling technology, in the field of ship form optimization design research, there has emerged a method based on optimization theory and driven by an optimization method for the ship form optimization design process. This method can automate the processes of ship form transformation, CFD solution, and result analysis, can reduce manual operations to a certain extent, and can effectively get rid of the high dependence on engineers in ship form design, realizing in-depth optimization design of ship form performance for the global design space, and has achieved good application effects in the optimization design of the resistance performance of various ship forms.

[0003] However, it is difficult to achieve good engineering applications for the optimization design of the propulsion performance of medium- and high-speed ship forms. The main reason is that when using the viscous flow method to carry out the self-propulsion performance calculation of medium- and high-speed ship forms, it is necessary to consider the coupled numerical simulation of multiple-level motions such as the floating state change during ship navigation and the rotation of the propeller. The physical problems to be solved are complex and the computational workload is large. In order to improve the computational efficiency to a certain extent, a large amount of manual intervention is required during the solution process. At the same time, the self-propulsion calculation results need to obtain self-propulsion points through interpolation of multiple propeller rotation speeds, and the result analysis process requires the combined analysis of multiple cases, and the full process integration and automation have not been realized, resulting in the inability to achieve automatic optimization design of ship form propulsion performance based on optimization algorithms. Summary of the Invention

[0004] To solve the problems existing in the numerical evaluation process of the propulsion performance of medium- and high-speed ship forms by the existing methods, such as a large amount of manual regulation, inability to achieve full-process integration automation, and inability to realize the optimization design of ship form self-propulsion performance driven by optimization algorithms, the present invention provides a method and a system for evaluating and optimizing the propulsion performance of medium- and high-speed ship forms, solves the integrated encapsulation and automation of the ship form self-propulsion performance calculation and evaluation process, and improves the application effect of optimization theory in the optimization design of medium- and high-speed ship forms.

[0005] The technical solution of the present invention is as follows:

[0006] A method for evaluating and optimizing the propulsion performance of medium- and high-speed ship forms, comprising the following steps:

[0007] Step 1: Establish the numerical calculation domain for the self-propulsion performance of medium- and high-speed ship forms: Obtain the three-dimensional geometric model file of the sample ship form, and extract the automated ship form characteristic parameters; construct a coordinate system group based on the automated ship form characteristic parameters and the navigation state parameters; the coordinate system group includes a global coordinate system, a hull motion coordinate system, and a propeller rotation coordinate system; establish the numerical calculation domain for the self-propulsion performance of medium- and high-speed ship forms based on the coordinate system group and the automated ship form characteristic parameters:

[0008] Step 2: Establish an integrated method for the numerical calculation process of the self-propulsion performance of medium- and high-speed ship forms;

[0009] Step 2.1: Establish a CFD numerical calculation model for the self-propulsion performance of medium- and high-speed ship forms by performing condition configuration on the numerical calculation domain for the self-propulsion performance of medium- and high-speed ship forms in Step 1: The condition configuration content includes: Select the Reynolds-averaged viscous flow calculation method as the basic method for model solution, select the SST K-ω turbulence model and the standard wall function to handle the simulation of the propeller-hull coupled flow field, select the VOF method to calculate the free surface of the ship, use the method of alternately using the moving reference coordinate system and the sliding grid to simulate the rotation of the propeller, and select the overlapping grid method to calculate the motion of the ship's longitudinal inclination and heave degrees of freedom;

[0010] Step 2.2: Establish an automatic control method for the CFD numerical calculation model for the self-propulsion performance of medium- and high-speed ship forms described in Step 2.1: 1) Set the numerical solution convergence control process and divide the calculation process: The calculation process includes the flow field initialization stage, the preliminary calculation stage of the hull flow field, the numerical calculation stage of the propeller-hull coupled flow field, the calculation stage of the flow field with the superposition of the hull motion and the propeller rotation, the refined numerical simulation stage, and the calculation stage of the self-propulsion point of the ship and the analysis stage of the self-propulsion performance of the ship; 2) Sequentially formulate the solution control method and the convergence discrimination method for the preliminary calculation stage of the hull flow field, the numerical calculation stage of the propeller-hull coupled flow field, the calculation stage of the flow field with the superposition of the hull motion and the propeller rotation, and the refined numerical simulation stage;

[0011] Step 2.3: Calculate the power received by the propeller: Combine the CFD numerical calculation model for the self-propulsion performance of medium- and high-speed ship forms described in Step 2.1 and the automatic control method for the model calculation process established in Step 2.2 to establish a numerical calculation model for the self-propulsion performance of medium- and high-speed ship forms, input the three-dimensional geometric model file of the sample ship form obtained in Step 1, complete the acquisition of the self-propulsion point of the medium- and high-speed ship form and the calculation and analysis of the self-propulsion performance characteristic parameters of the ship, and output the power received by the propeller as the self-propulsion performance characteristic quantity;

[0012] Step 3: Establish an optimization method for the self-propulsion performance of medium- and high-speed ship forms:

[0013] Step 3.1: Construct a three-dimensional geometric model file of the deformed ship form based on the hull deformation constraint conditions, and input it as the three-dimensional geometric model file of the sample ship form into Step 2 to calculate the power P received by the ship's propeller D, to achieve the numerical calculation of the self-propulsion performance of the variant ship form;

[0014] Step 3.2: Optimize the received power P of the ship's propeller obtained in Step 3.1 using the genetic algorithm D , with the tail variant parameter as the independent variable, the calculated received power of the ship's propeller as the objective function, and the value requirement of the ship form optimization design objective P D as the optimization objective of the ship's self-propulsion performance, that is, the preset termination condition of the genetic algorithm; automatically output the optimized received power P of the ship's propeller D .

[0015] Preferably, the method for extracting the automated ship form characteristic parameters in Step 1 is as follows:

[0016] Step 1.1: Obtain the three-dimensional geometric model file (IGS / IGES format) of the sample ship form. The length unit of the three-dimensional model file is "meter", the origin of the model coordinate system is located at the intersection of the ship's after perpendicular and the ship's baseline, the X-axis direction of the coordinate system is from the ship's stern to the bow, the Y-axis direction is from the ship's starboard to the port side, and the Z-axis direction is vertically upward from the ship's bottom to the deck;

[0017] Step 1.2: Extract the three-dimensional geometric characteristic parameters of the ship form: Based on the three-dimensional geometric model file of the sample ship form described in Step 1.1, extract the three-dimensional geometric characteristic parameters of the ship form, including: the main dimension characteristic parameters of the ship form and the propeller scale characteristic parameters;

[0018] The main dimension parameters of the ship form include: the designed draft of the ship, the length between perpendiculars of the ship, the overall length of the ship, the designed waterline length of the ship, and the molded breadth of the ship;

[0019] The designed draft of the ship (denoted as T d ): Obtained by inputting parameter values, with the unit of "meter";

[0020] The length between perpendiculars of the ship (denoted as L BP ): Obtained by extracting the X-direction distance between the intersection point of the stem and the designed waterline and the after perpendicular of the ship, with the unit of "meter";

[0021] The designed waterline length of the ship (denoted as L WL ): Based on the designed draft of the ship, extract the designed waterline of the ship, and obtain it by reading the distance between the front end and the rear end of the designed waterline in the X direction, with the unit of "meter";

[0022] The molded breadth of the ship (denoted as B): Obtained by extracting the maximum distance in the Y direction of the intersection line of the ship's port and starboard surfaces and the midship plane of the ship, with the unit of "meter";

[0023] The propeller scale characteristic parameters include: propeller diameter, propeller shaft height, distance between the propeller disk and the stern vertical line, distance between the propeller blade tip and the bottom of the ship, maximum X-coordinate of the propeller blade, minimum X-coordinate of the propeller blade, and minimum distance between the propeller blade and the rudder blade in the X direction.

[0024] Among them, the propeller diameter (denoted as D p ), propeller shaft height (i.e. the propeller shaft height from the baseline, expressed as H S ), the distance between the propeller disk and the stern perpendicular (expressed as X P ) and other parameters are obtained by inputting parameter values, and the unit is meter.

[0025] Distance between propeller blade and bottom of ship (D S ): Extract the midship longitudinal section line of the ship and x = X P The Z coordinate value of the intersection point of the plane (expressed as Z P ), D is calculated by the following formula S =Z P -(D p / 2+H S ).

[0026] The maximum X coordinate of the propeller blade (expressed as X Pmax ) and the minimum X coordinate of the propeller blade (denoted as X Pmin ): Establish a section at intervals of 0.01 meters along the Y direction, obtain the intersection line between the section and the propeller series, and extract the maximum X coordinate value of the intersection line to obtain the X Pmax value, the minimum X coordinate value is X Pmin value.

[0027] The minimum distance between the propeller blade and the rudder blade in the X direction (expressed as X RPmin ): Extract the Z direction plane Z=(D p / 2+H S )The maximum X coordinate value of the intersection line between the plane and the rudder (expressed as X Rmax ), X is calculated by the following formula RPmin Value: X RPmin =X Pmin -X RPmin .

[0028] The unit of this parameter is the length unit "meter"

[0029] Step 1.3: Extracting automated ship form characteristic parameters: using the three-dimensional geometric characteristic parameters of the ship form in step 1.2 as automated ship form characteristic parameters; constructing an automated ship form characteristic parameter extraction program based on steps 1.1-1.2, with the input being the sample ship form three-dimensional geometric model file, and the output being the automated ship form characteristic parameters.

[0030] Preferably, the method for establishing the numerical calculation domain of the self-propulsion performance of the medium- and high-speed ship form in Step 1 is as follows:

[0031] Step 1.4: Construct a fixed global coordinate system with the origin of the model coordinates described in Step 1.1 as the input parameter;

[0032] Step 1.5: Obtain the coordinate values (X G , Y G , Z G ) of the ship's center of gravity in the global coordinate system, and construct a hull motion coordinate system that moves with the hull using these as the coordinate origin. The initial directions of its coordinate axes are: the X-axis points forward along the ship's bow, the Y-axis points to the port side of the hull, and the Z-axis points vertically upward. The hull motion coordinate system is rigidly connected to the hull and moves synchronously with the hull;

[0033] Step 1.6: Based on parameters such as the propeller shaft height (i.e., the height of the propeller shaft from the baseline, denoted as H S ), and the distance from the propeller disk plane to the after perpendicular (denoted as X P ), etc., obtain the coordinate values of the propeller center point in the hull motion coordinate system as (X G - X P , 0, H S - Z G ). Construct a propeller rotation coordinate system with the propeller center point as the coordinate origin. The propeller rotation coordinate system is rigidly connected to the hull and moves synchronously with the hull;

[0034] Step 1.7: Based on the automated ship form characteristic parameters, the global coordinate system, the hull motion coordinate system, and the propeller rotation coordinate system, construct an internal calculation domain, an external background calculation domain, and a propeller rotation calculation domain that enclose the hull.

[0035] Preferably, the method for constructing the internal calculation domain, the external background calculation domain, and the propeller rotation calculation domain in Step 1.7 is as follows,

[0036] Step 1.7.1: Establish an internal calculation domain that encloses the hull: Set the scale to parameters related to the hull support. Based on the longitudinal inclination and heave motion of the ship during navigation, open the degrees of freedom of the hull's vertical motion and rotation about the Y-axis for numerical calculation. The internal and external calculation domains use the overlapping grid method for information transfer of flow field data;

[0037] Step 1.7.2: Establish an external background calculation domain: Set the shape of the external background calculation domain to a rectangle to avoid the pool wall interference effect during the calculation process. Set the scale of the external background calculation domain to parameters related to the main dimensions of the hull, and keep it stationary during the calculation process;

[0038] Step 1.7.3: Establish the propeller rotation calculation domain: The propeller rotation calculation domain is arranged at the stern shaft of the ship. A cylinder is used to wrap the propeller, and the axis of the cylinder is aligned with the propeller shaft. The scale of the cylinder is associated with the hull parameters extracted in Step 1.2 and the scale characteristic parameters of the propeller.

[0039] Preferably, in Step 2.2, the steps of establishing the automatic control method include:

[0040] Step 2.2.1: Set the numerical solution convergence control process and divide the calculation process: The numerical solution convergence control process is from the completion of the initialization of the flow field in the calculation domain to the convergence process of the coupled numerical calculation of the ship and propeller under the multi-degree-of-freedom motion of the hull. The calculation process includes: the flow field initialization stage, the preliminary calculation stage of the hull flow field, the numerical calculation stage of the coupled ship-propeller flow field, the calculation stage of the flow field of the hull motion superposed with the propeller rotation, the refined numerical simulation stage, and the calculation of the self-propelled point of the ship and the analysis of the self-propelled performance of the ship.

[0041] Step 2.2.2: Set the solution control method for the flow field initialization stage:

[0042] Set the initial conditions of the CFD numerical calculation model for the self-propelled performance of high-speed ship types in this stage: Given the propeller rotation speed is 0, and at the same time lock the degrees of freedom of the ship's motion, that is, both the hull and the propeller are fixed constraint models. The propeller is actually a fixed component rigidly connected to the hull, and no rotational speed is given.

[0043] Input the ship speed into the CFD numerical calculation model for the self-propelled performance of high-speed ship types in Step 2.1 to solve the initialized flow field. The initialized flow field includes: the initial speed and pressure parameters of the ship.

[0044] Step 2.2.3: Set the solution control method for the preliminary calculation stage of the hull flow field:

[0045] Take the initialized flow field as the initial conditions of the CFD numerical calculation model for the self-propelled performance of high-speed ship types in this stage. Calculate the time step based on the minimum grid size, and at the same time continue to lock the degrees of freedom of the ship's motion and the rotation of the propeller, and perform numerical iterative solution on the flow field near the ship's hull to obtain the preliminary hull flow field. Establish a curve of the hull resistance varying with time, that is, the hull resistance curve, and perform convergence discrimination on this curve. If the convergence discrimination conditions are met, proceed to the next step and output the preliminary hull flow field and the hull resistance curve.

[0046] Step 2.2.4: Solution control method for the numerical calculation stage of the coupled ship-propeller flow field:

[0047] Based on the preliminary hull flow field as the initial conditions of the CFD numerical calculation model for the self-propelled performance of high-speed ship types in this stage, set the propeller rotation speed to solve the coupled ship-propeller flow field and perform convergence discrimination.

[0048] A1: Solve the coupled propeller-flow field: Lock the degrees of freedom of the hull movement, use the moving reference coordinate system method to calculate the influence of the propeller rotation, calculate the time step based on the minimum grid size, and set the propeller rotation speed to the initial rotation speed n o ; Solve the coupled propeller-flow field under the suction effect of the propeller;

[0049] A2: Convergence criterion: Monitor and analyze the time history curves of the hull resistance, propeller thrust, and propeller torque during the numerical calculation stage of the coupled propeller-flow field respectively. Check whether the convergence criterion conditions are met. If so, proceed to step 2.2.5; and output the force conditions of the propeller and hull.

[0050] Step 2.2.5: Solution control method for the calculation stage of the hull movement superposed with the propeller rotation flow field: Based on the coupled propeller-flow field as the initial condition of the self-propulsion performance CFD numerical calculation model of the high-speed ship type in this stage, calculate the hull movement superposed with the propeller rotation flow field, and perform convergence discrimination;

[0051] B1: Solve the hull movement superposed with the propeller rotation flow field: Release the degrees of freedom of the hull, use the moving reference coordinate system method to calculate the influence of the propeller rotation, and use the initial rotation speed n obtained in the calculation of step 2.2.4 for the propeller rotation speed 0 , calculate the time step based on the minimum grid size, and solve the numerical value of the hull movement superposed with the propeller rotation flow field;

[0052] B2: Convergence criterion: Monitor the time history curves of the hull resistance, propeller thrust, propeller torque, hull trim value, and hull sinkage changing with time during the calculation process, analyze and perform convergence discrimination on the time history curves, calculate the change in the ship's navigation attitude and the forces on the propeller and hull under the coupled action of the propeller and hull, and proceed to step 2.2.6 after convergence;

[0053] Step 2.2.6: Solution control method for the refined numerical simulation stage: Based on the satisfaction of the convergence conditions calculated in step 2.2.5, carry out the refined numerical simulation of the coupled multi-degree-of-freedom movement of the propeller and hull;

[0054] C1: Take the hull movement superposed with the propeller rotation flow field as the initial condition of the self-propulsion performance CFD numerical calculation model of the high-speed ship type in this stage, release the degrees of freedom of the hull, and at the same time use the sliding mesh method to calculate the real rotation of the propeller, and set the propeller rotation speed to the initial rotation speed n 0 , calculate the time step using formula (1);

[0055]

[0056] Among them, n in formula (1) is the initial rotation speed n 0 , a is the control parameter for the propeller rotation angle within each time step, and its value ranges from 1 to 2;

[0057] C2: Convergence Criterion: Monitor and analyze the time history curves of the hull resistance, propeller thrust, propeller torque, hull trim value, and hull sinkage during this stage respectively, and conduct convergence criterion. Take the overall mean value of the monitored quantities calculated after the corresponding time history curves meet the convergence criterion as the initial rotational speed n 0 The hull resistance R' corresponding to the working condition 0B , the propeller thrust T 0B and the propeller torque Q 0B , the hull trim value, and the hull sinkage;

[0058] Step 2.2.7: Ship Self-Propulsion Point Calculation and Solution Control Method: Based on the initial rotational speed n calculated in Step 2.2.6 0 The hull resistance R' corresponding to the working condition 0B , the propeller thrust T 0B , the propeller torque Q 0B , the hull trim value, and the hull sinkage; Judge the force balance relationship between the ship and the propeller according to formula (2);

[0059] ΔZ = T 0B - R' 0B (2)

[0060] When ΔZ = 0, the propeller rotational speed n 0 is the self-propulsion point rotational speed n of the ship B , and the corresponding R′ 0B , T 0B , Q 0B are respectively the hull resistance R B , the propeller thrust T B , and the propeller torque T B in the calculation result data at the self-propulsion point; When ΔZ ≠ 0, reselect the propeller rotational speed and return to Step 2.2.6 for calculation until ΔZ = 0;

[0061] Step 2.2.8: Ship Self-Propulsion Performance Prediction Method: Calculate the power P received by the actual ship's propeller D ;

[0062] P D = 2 * π * n B * Q B (3)

[0063] The self-propulsion point rotational speed n of the ship B , and the propeller torque Q B .

[0064] Preferably, the convergence criterion method is:

[0065] S1: Calculate the amplitudes, mean amplitudes, and overall mean values of the monitored quantities of the time history curves of hull resistance, propeller thrust, propeller torque, hull trim value, and hull sinkage within the set oscillation period based on formulas (4) to (7).

[0066] A i =R Pi -R Ti (4)

[0067]

[0068] Where A i , R Pi , R Ti represent the amplitude, peak, and trough of the curve in the i-th oscillation period respectively, represents the mean amplitude of the 10 selected oscillation periods;

[0069] Calculate the mean values using formulas (6) and (7);

[0070]

[0071] Where R 0i , R 0 represent the mean value of the curve in the i-th oscillation period and the overall mean value of the monitored quantity within all 10 oscillation periods respectively;

[0072] S2: Calculate the convergence discrimination conditions for the time history curves of hull resistance, propeller thrust, propeller torque, hull trim value, and hull sinkage based on formulas (8) to (9),

[0073]

[0074] Formula (8) is that the ratio of the mean amplitude of the latest 10 change periods of the time history curve to the overall mean value of the monitored quantity is less than ε 1 , ε 1 takes a value of 5%;

[0075]

[0076] Formula (9) is that the percentage of the difference between the maximum value of the mean value of the monitored quantity in each period of the time history curve and the overall mean value to the overall mean value is less than ε 2 , ε 2 takes a value of 1% - 2%;

[0077] When all the time history curves obtained at this stage of the calculation simultaneously satisfy the convergence discrimination conditions, it is determined that the calculation has converged, and after the time history curves of hull resistance, propeller thrust, propeller torque, hull trim value, and hull sinkage satisfy the convergence discrimination conditions, the overall mean value of the monitored quantity calculated is used as the initial rotational speed n 0The hull resistance R′ corresponding to the working condition 0B , the propeller thrust T 0B and the propeller torque Q 0B , the hull trim value, the hull sinkage; the calculation process proceeds to the next step.

[0078] Preferably, the method for calculating the time step based on the minimum grid size is:

[0079]

[0080] where Δt is the time step; is the reference speed, and its value is the incoming flow speed of the computational domain; Δx is the minimum grid scale in the flow direction, i.e., the x - direction; C MAX is the Courant number, and its set value is 10.

[0081] Preferably, for the initial rotational speed n described in A1 o the calculation method is:

[0082] A11: Estimate the initial thrust T of the ship according to formula (11) 0 ;

[0083]

[0084] where R 0 is the overall mean value of the monitored quantity calculated based on the time - history curve of the hull resistance, i.e., the mean value of the ship resistance; t is the thrust deduction fraction, and its value range is 0.15 - 0.25 according to different ship types;

[0085] A12: Obtain the open - water characteristic data of the corresponding type based on the ship type: The open - water characteristic data of the propeller includes: the thrust coefficient K corresponding to the series advance coefficient J T , the torque coefficient K Q and the open - water efficiency η 0 data;

[0086] A121: Obtain the thrust coefficient K T0 : Interpolate on the open - water characteristic data curve of the propeller with 75% of the maximum open - water efficiency as the input to obtain the thrust coefficient K T0 ;

[0087] A13: Estimate the initial rotational speed n of the propeller according to formula (12) o :

[0088]

[0089] where ρ is the density of seawater and D is the diameter of the propeller.

[0090] Preferably, in step 2.2.7, when ΔZ≠0, the processing method is:

[0091] 1) If ΔZ < 0, it means that the thrust generated by the propeller cannot overcome the hull resistance, and the propeller speed needs to be increased. The new speed n is calculated using formulas (13) to (16). 1 、n 2 、n 3 ,where K T0B The propeller speed n 0 corresponding propeller thrust coefficient, ρ is the density of seawater, and D is the propeller diameter;

[0092]

[0093] n 2 =n 1 +(n 1 -n 0 ) (15)

[0094] n 3 =n 2 +(n 1 -n 0 ) (16)

[0095] Return to step 2.2.6, and adjust the propeller speeds to n 1 、n 2 、n 3 respectively, perform convergence discrimination, and obtain the corresponding hull resistance, propeller thrust, and propeller torque when the propeller speeds are n 1 、n 2 、n 3 respectively. At the same time, calculate the corresponding ΔZ at the three speeds based on formula (2). 1 、ΔZ 2 、ΔZ 3 ; Using the hull resistance, propeller thrust, and propeller torque data at the four speeds of n 0 、n 1 、n 2 、n 3 as input conditions, perform cubic spline interpolation with ΔZ = 0 to obtain the propeller speed n B 、hull resistance R B 、propeller thrust T B 、propeller torque Q B ;

[0096] 2) If ΔZ > 0, it means that the thrust generated by the propeller is too large, and the propeller speed needs to be decreased. The new speed n is calculated using formulas (13), (17) to (19). 1 、n 2 、n 3 ,where K T0B The propeller speed n0 The corresponding propeller thrust coefficient, ρ is the density of fresh water, and D is the propeller diameter;

[0097]

[0098] n 2 = n 1 -(n 0 - n 1 )(18)

[0099] n 3 = n 2 -(n 0 - n 1 )(19)

[0100] Adjust the propeller speed to n 1 , n 2 , n 3 respectively, and carry out the refined numerical simulation of ship self-propulsion step by step according to Step 2.2.6 until the convergence condition is reached. Obtain the hull resistance, propeller thrust and torque corresponding to the propeller speeds n 1 , n 2 , n 3 respectively. At the same time, calculate the corresponding ΔZ 1 , ΔZ 2 , ΔZ 3 at the three speeds based on formula (2); Use the series of data corresponding to the four speeds of n 0 , n 1 , n 2 , n 3 as input conditions for cubic spline interpolation to obtain the propeller speed n B , hull resistance R B , propeller thrust T B , and propeller torque Q B that satisfy the condition of ΔZ = 0.

[0101] Preferably, the method for obtaining the three-dimensional geometric model file after the ship form is deformed in Step 3.1 is as follows: Use parametric modeling software to establish a parametric variant model of the ship's tail. Based on the hull deformation constraint conditions, change the variant parameters of the ship's tail to realize the transformation of the three-dimensional geometric model of the ship's tail and obtain the three-dimensional geometric model file after the ship form is deformed.

[0102] A system for evaluating and optimizing the propulsion performance of medium- and high-speed ship forms,

[0103] Ship form transformation subsystem: including: a ship tail deformation unit for establishing a parametric variant model of the ship tail based on parametric modeling software; a ship form deformation parameter acquisition unit for changing the variant parameters of the ship hull tail to realize the transformation of the three-dimensional geometric model of the ship tail and obtain the three-dimensional geometric model file after ship form transformation as the sample ship form three-dimensional geometric model file.

[0104] Self-propulsion performance evaluation subsystem: including: a computational domain unit for establishing a numerical computational domain for the self-propulsion performance of medium- and high-speed ship forms; a CFD numerical computational model unit for medium- and high-speed ship forms' self-propulsion performance to configure the conditions of the numerical computational domain for the self-propulsion performance of medium- and high-speed ship forms and establish a CFD numerical computational model for the self-propulsion performance of medium- and high-speed ship forms; a model control unit for establishing an automatic control method for the CFD numerical computational model of the self-propulsion performance of medium- and high-speed ship forms; a numerical computational model unit for the self-propulsion performance of ships of medium- and high-speed ship forms to establish a numerical computational model for the self-propulsion performance of ships of medium- and high-speed ship forms by combining the CFD numerical computational model for the self-propulsion performance of medium- and high-speed ship forms and the automatic control method; a model calculation unit for inputting the sample ship form three-dimensional geometric model file obtained by the ship form transformation subsystem into the numerical computational model for the self-propulsion performance of ships of medium- and high-speed ship forms and calculating the power received by the ship's propeller.

[0105] Self-propulsion performance optimization subsystem for medium- and high-speed ship forms: including: a condition preset unit for setting the optimization target of the ship's self-propulsion performance as the termination condition of the genetic algorithm; a self-propulsion performance optimization unit for optimizing the power received by the ship's propeller obtained by the self-propulsion performance evaluation subsystem based on the genetic algorithm.

[0106] The beneficial effects of the present invention are as follows:

[0107] The present invention provides a method and system for evaluating and optimizing the propulsion performance of medium- and high-speed ship forms. Specifically including: a method for constructing a numerical computational model for the self-propulsion performance of high-speed ships, a method for controlling and integrating the numerical computational process of the propulsion performance of medium- and high-speed ships. Through ship form feature extraction and analysis, automatic construction of the numerical computational model for ship self-propulsion is realized. The numerical computational process of the self-propulsion is divided according to the evolution process of the flow field. The numerical calculation process adopts a step-by-step progressive manner at each stage. Computational control methods for each stage and a quantitative standard method for judging computational convergence are established, gradually approaching the real flow field conditions to achieve computational convergence, and a computational integration system is developed for computational process integration and encapsulation. On the one hand, it avoids the problems of increased computational iteration times caused by using multi-level coupled motion and too small time steps from the beginning of the calculation and slow computational oscillation convergence caused by too large a difference between the initial flow field and the actual flow field. On the other hand, through the establishment of the integration method and the development of the integration system, the automation of the computational process is realized, eliminating the requirement for manual control during the computational process and improving the computational efficiency.

[0108] An integrated method and system for optimizing the self-propulsion performance of high-speed ship types provided by the present invention establish a method for adjusting the propeller at multiple rotational speeds in self-propulsion calculations, a calculation convergence criterion, a method for extracting calculation results and predicting the self-propulsion performance of ships, establish a method for automating the analysis process of ship self-propulsion performance, construct an optimized method-driven medium- and high-speed ship type transformation, self-propulsion performance evaluation process, and optimization design process method, solve the problem that manual interaction is required in the process and full-process automation cannot be achieved, and improve the application effect of optimization theory in the optimization design of medium- and high-speed ship types. BRIEF DESCRIPTION OF THE DRAWINGS

[0109] Figure 1 It is a flow chart of the method for evaluating and optimizing the propulsion performance of medium- and high-speed ship types in the present invention.

[0110] Figure 2 It is a flow chart of the method for constructing the numerical calculation domain of the self-propulsion performance of medium- and high-speed ship types established by the present invention.

[0111] Figure 3 It is a flow chart for controlling the numerical solution process of medium- and high-speed ships established by the present invention.

[0112] Figure 4 It is a structural diagram of the system for evaluating and optimizing the propulsion performance of medium- and high-speed ship types in the present invention. SPECIFIC IMPLEMENTATION METHOD

[0113] The present invention will be described below with reference to the accompanying drawings.

[0114] As Figure 1 shown, a method for evaluating and optimizing the propulsion performance of medium- and high-speed ship types includes the following steps:

[0115] Step 1: Establish a numerical calculation domain for the self-propulsion performance of medium- and high-speed ship types: Obtain the three-dimensional geometric model file of the sample ship type, and extract the automatic ship type characteristic parameters; construct a coordinate system group based on the automatic ship type characteristic parameters and the navigation state parameters; the coordinate system group includes a global coordinate system, a ship hull motion coordinate system, and a propeller rotation coordinate system; establish a numerical calculation domain for the self-propulsion performance of medium- and high-speed ship types based on the coordinate system group and the automatic ship type characteristic parameters:

[0116] Step 2: Establish an integrated method for the numerical calculation process of the self-propulsion performance of medium- and high-speed ship types;

[0117] Step 2.1: Establish a CFD numerical calculation model for the self-propulsion performance of a medium- and high-speed ship type by configuring the conditions for the numerical calculation domain of the self-propulsion performance of the medium- and high-speed ship type in Step 1. The content of the condition configuration includes: selecting the Reynolds-averaged viscous flow calculation method as the basic method for model solution, selecting the SST K-ω turbulence model and the standard wall function to handle the simulation of the propeller-fluid coupling flow field, selecting the VOF method to calculate the free surface of the ship, using the method of alternately using the moving reference coordinate system and the sliding grid to simulate the rotation of the propeller, and selecting the overlapping grid method to calculate the longitudinal pitch and heave degrees of freedom motion of the ship hull;

[0118] Step 2.2: Establish an automatic control method for the CFD numerical calculation model of the self-propulsion performance of the medium- and high-speed ship type described in Step 2.1: 1) Set the numerical solution convergence control process and divide the calculation process. The calculation process includes the flow field initialization stage, the preliminary calculation stage of the ship hull flow field, the numerical calculation stage of the propeller-fluid coupling flow field, the calculation stage of the ship hull motion superposed with the propeller rotation flow field, the refined numerical simulation stage, and the calculation of the self-propulsion point of the ship and the analysis of the self-propulsion performance of the ship; 2) Successively formulate the solution control method and the convergence discrimination method for the preliminary calculation stage of the ship hull flow field, the numerical calculation stage of the propeller-fluid coupling flow field, the calculation stage of the ship hull motion superposed with the propeller rotation flow field, and the refined numerical simulation stage;

[0119] Step 2.3: Calculate the power received by the propeller. Combine the CFD numerical calculation model for the self-propulsion performance of the medium- and high-speed ship type described in Step 2.1 and the automatic control method of the model calculation process established in Step 2.2 to establish a numerical calculation model for the self-propulsion performance of the medium- and high-speed ship type. Input the three-dimensional geometric model file of the sample ship type obtained in Step 1, complete the acquisition of the self-propulsion point of the medium- and high-speed ship type and the calculation and analysis of the self-propulsion performance characteristic parameters, and output the power received by the propeller as the self-propulsion performance characteristic quantity;

[0120] Step 3: Establish an optimization method for the self-propulsion performance of the medium- and high-speed ship type:

[0121] Step 3.1: Construct a three-dimensional geometric model file of the ship type after deformation based on the hull deformation constraint conditions, and use it as the three-dimensional geometric model file of the sample ship type to input to Step 2 to calculate the power P received by the ship's propeller D , and realize the numerical calculation of the self-propulsion performance of the variant ship type;

[0122] Step 3.2: Use the genetic algorithm to optimize the power P received by the ship's propeller obtained in Step 3.1 D , with the tail variant parameter as the independent variable, the calculated power received by the ship's propeller as the objective function, and the value requirement of the ship type optimization design target P D as the self-propulsion performance optimization target of the ship, that is, the preset termination condition of the genetic algorithm; automatically output the optimized power P received by the ship's propeller D .

[0123] As shown Figure 2 in the following, the specific steps for establishing the numerical calculation domain of the self-propulsion performance of a medium-high speed ship form in Step 1 are as follows:

[0124] Preferably, the method for extracting the characteristic parameters of the automated ship form in Step 1 is as follows:

[0125] Step 1.1: Obtain the three-dimensional geometric model file (IGS / IGES format) of the sample ship form. The length unit of the three-dimensional model file is "meter", and the origin of the model coordinate system is located at the intersection of the after perpendicular of the ship and the baseline of the ship. The X-axis direction of the coordinate system is from the stern to the bow of the ship, the Y-axis direction is from the starboard side to the port side of the ship, and the Z-axis direction is vertically upward from the bottom of the ship to the deck;

[0126] Step 1.2: Extract the three-dimensional geometric characteristic parameters of the ship form: Based on the three-dimensional geometric model file of the sample ship form described in Step 1.1, extract the three-dimensional geometric characteristic parameters of the ship form, including: the main dimension characteristic parameters of the ship form and the scale characteristic parameters of the propeller;

[0127] The main dimension parameters of the ship form include: the designed draft of the ship, the length between perpendiculars of the ship, the overall length of the ship, the length of the designed waterline of the ship, and the molded breadth of the ship;

[0128] The designed draft of the ship (denoted as T d ): Obtained by inputting parameter values, with the unit of meter;

[0129] The length between perpendiculars of the ship (denoted as L BP ): Obtained by extracting the X-direction distance between the intersection point of the stem and the designed waterline and the after perpendicular of the ship, with the unit of meter;

[0130] The length of the designed waterline of the ship (denoted as L WL ): Based on the designed draft of the ship, extract the designed waterline of the ship, and obtain it by reading the distance between the front end and the rear end of the designed waterline in the X direction, with the unit of meter;

[0131] The molded breadth of the ship (denoted as B): Obtained by extracting the maximum distance in the Y direction of the intersection line between the left and right hull surfaces of the ship and the midship plane, with the unit of meter;

[0132] The scale characteristic parameters of the propeller include: the diameter of the propeller, the height of the propeller shaft, the distance between the propeller disk and the after perpendicular, the distance between the tip of the propeller blade and the bottom of the ship, the maximum X coordinate of the propeller blade, the minimum X coordinate of the propeller blade, and the minimum X-direction distance between the propeller blade and the rudder blade.

[0133] Among them, the diameter of the propeller (denoted as D p ), the height of the propeller shaft (i.e., the height of the propeller shaft from the baseline, denoted as H S ), the distance between the propeller disk and the after perpendicular (denoted as X P ) and other parameters are obtained by inputting parameter values, and the unit of all of them is meter.

[0134] Distance from the tip of the propeller blade to the bottom of the ship (D S ): Extract the Z coordinate value (denoted as Z P ) of the intersection point of the midship longitudinal section of the ship and the plane x = X P . Calculate D through the following formula S = Z P - (D p / 2 + H S ).

[0135] Maximum X coordinate of the propeller blade (denoted as X Pmax ) and minimum X coordinate of the propeller blade (denoted as X Pmin ): Establish cross-sections at intervals of 0.01 m in the Y direction, obtain the intersection lines of the cross-sections and the propeller series, and extract the maximum X coordinate value of the intersection line to obtain the X Pmax value, and the minimum X coordinate value is the X Pmin value.

[0136] Minimum distance in the X direction between the propeller blade and the rudder blade (denoted as X RPmin ): Extract the maximum X coordinate value (denoted as X p / 2 + H S ) of the intersection line of the plane Z = (D Rmax ) in the Z direction and the rudder. Calculate the X RPmin value through the following formula: X RPmin = X Pmin - X RPmin .

[0137] The unit of such parameters is the length unit "meter".

[0138] Step 1.3: Extract the automated ship form characteristic parameters: Use the ship form three-dimensional geometric characteristic parameters in Step 1.2 as the automated ship form characteristic parameters; Based on Steps 1.1 - 1.2, construct an automated ship form characteristic parameter extraction program, with the input being the sample ship form three-dimensional geometric model file and the output being the automated ship form characteristic parameters.

[0139] Preferably, the method for establishing the self-propelled performance numerical calculation domain of the medium and high-speed ship form in Step 1 is as follows:

[0140] Step 1.4: Construct a fixed global coordinate system with the model coordinate origin in Step 1.1 as the input parameter;

[0141] Step 1.5: Obtain the coordinate values (X G , Y G , Z G of the ship's center of gravity in the global coordinate system), and taking this as the coordinate origin, a hull motion coordinate system that moves with the hull is constructed. The initial directions of its coordinate axes are as follows: the X-axis points towards the bow of the ship, the Y-axis points towards the port side of the hull, and the Z-axis is vertically upward. The hull motion coordinate system is rigidly connected to the hull and moves synchronously with the hull;

[0142] Step 1.6: Based on the propeller shaft height (i.e., the height of the propeller shaft from the baseline, denoted as H S ), the distance from the propeller disk plane to the stern perpendicular (denoted as X P ), etc. parameters, the coordinate value of the propeller center point in the hull motion coordinate system is obtained as (X G - X P , 0, H S - Z G ). Taking the propeller center point as the coordinate origin, a propeller rotation coordinate system is constructed. The propeller rotation coordinate system is rigidly connected to the hull and moves synchronously with the hull;

[0143] Step 1.7: Based on the described automated ship form characteristic parameters and the global coordinate system, hull motion coordinate system, and propeller rotation coordinate system, an internal calculation domain, an external background calculation domain, and a propeller rotation calculation domain that enclose the hull are constructed.

[0144] Preferably, the method for constructing the internal calculation domain, external background calculation domain, and propeller rotation calculation domain that enclose the hull in Step 1.7 is as follows:

[0145] Step 1.7.1: Establish the internal calculation domain that encloses the hull: The scale is set to parameters related to the hull support. Based on the longitudinal inclination and heave motion of the ship during navigation, the degrees of freedom of the hull's vertical motion and rotation about the Y-axis are opened for numerical calculation. The internal and external calculation domains use the overlapping grid method for information transfer of flow field data;

[0146] Step 1.7.2: Establish the external background calculation domain: The shape of the external background calculation domain is set as a rectangle to avoid the pool wall interference effect during the calculation process. The scale of the external background calculation domain is set to parameters related to the main dimensions of the hull and remains stationary during the calculation;

[0147] Step 1.7.3: Establish the propeller rotation calculation domain: The propeller rotation calculation domain is arranged at the stern shaft of the ship. A cylinder is used to wrap the propeller, and the axis of the cylinder is aligned with the propeller shaft. The scale of the cylinder is associated with the hull parameter and propeller scale characteristic parameter extracted in Step 1.2.

[0148] Preferably, in Step 2.2, the steps for establishing the automatic control method include:

[0149] Step 2.2.1: Set the numerical solution convergence control process and divide the calculation process: The numerical solution convergence control process is the process from the completion of the initialization of the flow field in the computational domain to the convergence of the coupled numerical calculation of the ship's propeller under multi-degree-of-freedom motion of the hull; The calculation process includes: the flow field initialization stage, the preliminary calculation stage of the hull flow field, the numerical calculation stage of the coupled ship-propeller flow field, the calculation stage of the flow field with the superposition of the hull motion and the rotation of the propeller, the refined numerical simulation stage, and the calculation stage of the ship's self-propelled point and the analysis stage of the ship's self-propelled performance;

[0150] As Figure 3 shown, the specific steps of the calculation process described in Step 2.2.1:

[0151] Step 2.2.2: Set the solution control method for the flow field initialization stage:

[0152] Set the initial conditions for the CFD numerical calculation model of the self-propelled performance of high-speed ship types in this stage: Given the propeller rotation speed is 0, and at the same time lock the degrees of freedom of the ship's body movement, that is, both the hull and the propeller are fixed constraint models. In fact, the propeller is a fixed component rigidly connected to the hull, and no rotation speed is given;

[0153] Input the ship speed into the CFD numerical calculation model of the self-propelled performance of high-speed ship types described in Step 2.1 to solve the initial flow field; The initial flow field includes: the initial speed and pressure parameters of the ship;

[0154] Step 2.2.3: Set the solution control method for the preliminary calculation stage of the hull flow field:

[0155] Take the initialized flow field as the initial condition of the CFD numerical calculation model of the self-propelled performance of high-speed ship types in this stage. Calculate the time step based on the minimum grid size, and at the same time continue to lock the degrees of freedom of the ship's body movement and the rotation of the propeller, and numerically iteratively solve the preliminary hull flow field for the flow field near the hull; Establish a curve of the hull resistance changing with time, that is, the hull resistance curve, and conduct a convergence discrimination on this curve. If the convergence discrimination condition is met, proceed to the next step and output the preliminary hull flow field and the hull resistance curve;

[0156] Step 2.2.4: Solution control method for the numerical calculation stage of the coupled ship-propeller flow field:

[0157] Based on the preliminary hull flow field as the initial condition of the CFD numerical calculation model of the self-propelled performance of high-speed ship types in this stage, set the propeller rotation speed to solve the coupled ship-propeller flow field and conduct a convergence discrimination;

[0158] A1: Solve the coupled ship-propeller flow field: Lock the degrees of freedom of the ship's body movement, use the moving reference coordinate system method to calculate the influence of the propeller rotation, calculate the time step based on the minimum grid size, and set the propeller rotation speed to the initial rotation speed n o ; Solve the coupled ship-propeller flow field under the suction effect of the propeller;

[0159] A2: Convergence Criterion: Monitor and analyze the time history curves of the hull resistance, propeller thrust, and propeller torque during the numerical calculation stage of the propeller-hull coupled flow field respectively to check if they meet the convergence criterion. If they do, proceed to step 2.2.5; and output the forces on the propeller and hull.

[0160] Step 2.2.5: Solution Control Method for the Calculation Stage of Hull Motion Superimposed with Propeller Rotation Flow Field: Based on the propeller-hull coupled flow field as the initial condition of the self-propulsion performance CFD numerical calculation model for high-speed ship forms in this stage, calculate the flow field of hull motion superimposed with propeller rotation and conduct convergence discrimination.

[0161] B1: Solve the Flow Field of Hull Motion Superimposed with Propeller Rotation: Release the degrees of freedom of the hull, and use the moving reference coordinate system method to calculate the influence of propeller rotation. The propeller rotation speed is the initial rotation speed n obtained in step 2.2.4 0 , calculate the time step based on the minimum grid size, and solve the numerical value of the flow field of hull motion superimposed with propeller rotation.

[0162] B2: Convergence Criterion: During the calculation process, monitor the time history curves of the hull resistance, propeller thrust, propeller torque, hull trim value, and hull sinkage varying with time, analyze and conduct convergence discrimination on the time history curves, calculate the change in the ship's navigation attitude and the forces on the propeller and hull under the combined action of the propeller and hull. After convergence, proceed to step 2.2.6.

[0163] Step 2.2.6: Solution Control Method for the Refined Numerical Simulation Stage: Based on the calculation in step 2.2.5 meeting the convergence condition, conduct a refined numerical simulation of the multi-degree-of-freedom motion of the propeller-hull coupling.

[0164] C1: Take the flow field of hull motion superimposed with propeller rotation as the initial condition of the self-propulsion performance CFD numerical calculation model for high-speed ship forms in this stage, release the degrees of freedom of the hull, and at the same time use the sliding mesh method to calculate the actual rotation of the propeller. The propeller rotation speed is set to the initial rotation speed n 0 , and calculate the time step using formula (1);

[0165]

[0166] where n in formula (1) is the initial rotation speed n 0 , a is the control parameter for the propeller rotation angle within each time step, with a value ranging from 1 to 2;

[0167] C2: Convergence Criterion: Monitor and analyze the time history curves of the hull resistance, propeller thrust, propeller torque, hull trim value, and hull sinkage in this stage respectively, and conduct convergence discrimination. Take the overall mean value of the monitored quantities obtained after the corresponding time history curves meet the convergence criterion as the initial rotation speed n 0The hull resistance R′ corresponding to the working condition 0B , the propeller thrust T 0B and the propeller torque Q 0B , the hull trim value, the hull sinkage amount;

[0168] Step 2.2.7: Ship self-propelled point calculation and solution control method: Based on the initial rotational speed n calculated in Step 2.2.6 0 The hull resistance R′ corresponding to the working condition 0B , the propeller thrust T 0B , the propeller torque Q 0B , the hull trim value, the hull sinkage amount; Judge the force balance relationship between the ship and the propeller according to formula (2);

[0169] ΔZ = T 0B -R′ 0B (2)

[0170] When ΔZ = 0, the propeller rotational speed n 0 is the self-propelled point rotational speed n of the ship B , and the corresponding R′ 0B , T 0B , Q 0B are respectively the hull resistance R B under the self-propelled point, the propeller thrust T B , the propeller torque T B Calculation result data; When ΔZ ≠ 0, reselect the propeller rotational speed, return to Step 2.2.6 for calculation until ΔZ = 0;

[0171] Step 2.2.8: Ship self-propelled performance prediction method: Calculate the received power P of the actual ship propeller D ;

[0172] P D = 2 * π * n B *Q B (3)

[0173] The self-propelled point rotational speed n of the ship B , the propeller torque Q B .

[0174] Preferably, the convergence discrimination method is:

[0175] S1: Based on formulas (4) to (7), calculate the amplitudes, amplitude means and overall means of the monitored quantities of the time history curves of the hull resistance, propeller thrust, propeller torque, hull trim value, and hull sinkage amount within the set oscillation period respectively;

[0176] A i = R Pi -R Ti (4)

[0177]

[0178] Among them, A i , R Pi , R Ti respectively represent the amplitude, peak and trough of the i-th oscillation period of the curve, represents the average amplitude of the 10 selected oscillation periods;

[0179] The average value is calculated using formulas (6) and (7);

[0180]

[0181] Among them, R 0i , R 0 respectively represent the average value of the i-th oscillation period of the curve and the overall average value of the monitored quantity within all 10 oscillation periods;

[0182] S2: Calculate the convergence discrimination conditions for the time history curves of hull resistance, propeller thrust, propeller torque, hull trim value, and hull sinkage based on formulas (8) - (9),

[0183]

[0184] Formula (8) is that the ratio of the average amplitude of the latest 10 change periods of the time history curve to the overall average value of the monitored quantity is less than ε 1 , ε 1 takes a value of 5%;

[0185]

[0186] Formula (9) is that the percentage of the difference between the maximum value of the average value of the monitored quantity in each period of the time history curve and the overall average value to the overall average value is less than ε 2 , ε 2 takes a value of 1% - 2%;

[0187] When all the time history curves obtained at this stage of the calculation simultaneously satisfy the convergence discrimination conditions, it is determined that the calculation has converged, and after the time history curves of hull resistance, propeller thrust, propeller torque, hull trim value, and hull sinkage satisfy the convergence discrimination conditions, the overall average value of the monitored quantity calculated is used as the initial rotational speed n 0 under the corresponding hull resistance R′ 0B , propeller thrust T 0B and propeller torque Q 0B , hull trim value, hull sinkage; The calculation process enters the next step.

[0188] Preferably, the method for calculating the time step based on the minimum grid size is:

[0189]

[0190] Among them, Δt is the time step; is the reference speed, and its value is the incoming flow speed of the computational domain; Δx is the minimum grid scale in the flow direction, i.e., the x direction; C MAX is the Courant number, and the set value is 10.

[0191] Preferably, the initial rotational speed n described in A1 o The calculation method is as follows:

[0192] A11: Estimate the initial thrust T of the ship according to formula (11) 0 ;

[0193]

[0194] where R 0 is the overall mean value of the monitored quantity calculated based on the time history curve of the hull resistance, i.e., the mean value of the ship resistance; t is the thrust deduction fraction, and its value range is 0.15 - 0.25 according to different ship types;

[0195] A12: Obtain the open - water characteristic data of the corresponding type based on the ship type: The open - water characteristic data of the propeller includes: the thrust coefficient K corresponding to the series advance coefficient J T , the torque coefficient K Q and the open - water efficiency η 0 data;

[0196] A121: Obtain the thrust coefficient K T0 : Using 75% of the maximum open - water efficiency as the input, perform interpolation on the open - water characteristic data curve of the propeller to obtain the thrust coefficient K T0 ;

[0197] A13: Estimate the initial rotational speed n of the propeller according to formula (12) o :

[0198]

[0199] where ρ is the density of seawater and D is the diameter of the propeller.

[0200] Preferably, in step 2.2.7, when ΔZ ≠ 0, the processing method is as follows:

[0201] 3) If ΔZ < 0, it means that the thrust generated by the propeller cannot overcome the hull resistance, and the rotational speed of the propeller needs to be increased. Use formulas (13) - (16) to calculate the new rotational speeds n 1 , n 2 , n 3 where K T0B rotational speed n 0The corresponding propeller thrust coefficient, ρ is the density of seawater, and D is the propeller diameter;

[0202]

[0203] n 2 = n 1 +(n 1 - n 0 ) (15)

[0204] n 3 = n 2 +(n 1 - n 0 ) (16)

[0205] Return to step 2.2.6, and adjust the propeller speed to n 1 , n 2 , n 3 respectively, conduct convergence discrimination, and obtain the hull resistance, propeller thrust, and propeller torque corresponding to the propeller speed of n 1 , n 2 , n 3 respectively. At the same time, calculate the corresponding ΔZ 1 , ΔZ 2 , ΔZ 3 based on formula (2); use the hull resistance, propeller thrust, and propeller torque data at the four propeller speeds of n 0 , n 1 , n 2 , n 3 as the input conditions for cubic spline interpolation to obtain the propeller speed n B , hull resistance R B , propeller thrust T B , and propeller torque Q B that satisfy the condition of ΔZ = 0;

[0206] 4) If ΔZ > 0, it means that the thrust generated by the propeller is too large, and the propeller speed needs to be reduced. Use formulas (13), (17) - (19) to calculate the new speeds n 1 , n 2 , n 3 , where K T0B is the propeller thrust coefficient corresponding to the speed n 0 , ρ is the density of fresh water, and D is the propeller diameter;

[0207]

[0208] n 2 = n 1 -(n 0 - n 1) (18)

[0209] n 3 = n 2 -(n 0 -n 1 ) (19)

[0210] Adjust the propeller speed to n 1 , n 2 , n 3 respectively, and carry out the refined numerical simulation of ship self-propulsion step by step according to step 2.2.6 until the convergence condition is reached. Obtain the hull resistance, propeller thrust and torque corresponding to the propeller speeds n 1 , n 2 , n 3 respectively. At the same time, calculate the corresponding ΔZ 1 , ΔZ 2 , ΔZ 3 at the three propeller speeds based on formula (2); Use the series of data corresponding to the four propeller speeds n 0 , n 1 , n 2 , n 3 as input conditions for cubic spline interpolation to obtain the propeller speed n B , hull resistance R B , propeller thrust T B , and propeller torque Q B that satisfy the condition of ΔZ = 0.

[0211] Preferably, the method for obtaining the three-dimensional geometric model file after the ship form transformation in step 3.1 is as follows: Use parametric modeling software to establish a parametric variant model of the ship's tail. Based on the hull deformation constraint conditions, change the variant parameters of the hull tail to realize the transformation of the three-dimensional geometric model of the ship's tail and obtain the three-dimensional geometric model file after the ship form transformation.

[0212] As Figure 4 shown, a system for evaluating and optimizing the propulsion performance of medium and high-speed ship forms

[0213] Ship form transformation subsystem: includes: a ship's tail deformation unit for establishing a parametric variant model of the ship's tail based on parametric modeling software; a ship form deformation parameter acquisition unit for changing the variant parameters of the hull tail to realize the transformation of the three-dimensional geometric model of the ship's tail and obtaining the three-dimensional geometric model file after the ship form transformation as the sample ship form three-dimensional geometric model file.

[0214] Self-propulsion performance evaluation subsystem: including: computational domain cells for establishing a numerical computational domain for the self-propulsion performance of medium- and high-speed ship forms; a CFD numerical calculation model unit for the self-propulsion performance of medium- and high-speed ship forms that configures conditions for the numerical computational domain of the self-propulsion performance of medium- and high-speed ship forms and establishes a CFD numerical calculation model for the self-propulsion performance of medium- and high-speed ship forms; a model control unit for an automatic control method for establishing a CFD numerical calculation model for the self-propulsion performance of medium- and high-speed ship forms; a numerical calculation model unit for the self-propulsion performance of ships of medium- and high-speed ship forms that establishes a numerical calculation model for the self-propulsion performance of ships of medium- and high-speed ship forms by combining the CFD numerical calculation model for the self-propulsion performance of medium- and high-speed ship forms and the automatic control method; a model calculation unit that inputs the sample ship form three-dimensional geometric model file obtained by the ship form transformation subsystem into the numerical calculation model for the self-propulsion performance of ships of medium- and high-speed ship forms and calculates the power received by the ship's propeller.

[0215] Self-propulsion performance optimization subsystem for medium- and high-speed ship forms: including: a condition preset unit that sets the optimization target of the self-propulsion performance of the ship as the termination condition of the genetic algorithm; a self-propulsion performance optimization unit that optimizes the power received by the ship's propeller obtained by the self-propulsion performance evaluation subsystem based on the genetic algorithm.

[0216] It should be noted that the above specific embodiments can enable those skilled in the art to understand the present invention more comprehensively, but do not limit the present invention in any way. Therefore, although this specification has described the present invention in detail with reference to the drawings and embodiments, those skilled in the art should understand that the present invention can still be modified or equivalently replaced. In short, all technical solutions and their improvements that do not depart from the spirit and scope of the present invention should be covered by the protection scope of the patent of the present invention.

Claims

1. A method for evaluating and optimizing the propulsion performance of medium- and high-speed ships, characterized in that: The following steps are involved: Step 1: Establishing the numerical calculation domain of the self-propulsion performance of medium- and high-speed ships: Obtain the sample ship three-dimensional geometric model file, extract the automated ship characteristic parameters; construct a coordinate system group based on the automated ship characteristic parameters and navigation parameters; the coordinate system group includes a global coordinate system, a hull motion coordinate system, and a propeller rotation coordinate system; based on the coordinate system group and the automated ship characteristic parameters, establish the numerical calculation domain of the self-propulsion performance of medium- and high-speed ships: Step 2: Establish an integrated method for the numerical calculation process of medium- and high-speed ship self-propulsion performance; Step 2.1: Establish a CFD numerical calculation model for the self-propulsion performance of medium- and high-speed ships by conditionally configuring the numerical calculation domain of the self-propulsion performance of medium- and high-speed ships in step 1: The conditional configuration includes: selecting the Reynolds average viscous flow calculation method as the basic method for solving the model, selecting the SST Kw turbulence model and the standard wall function to handle the ship-propeller coupled flow field simulation, selecting the VOF method to calculate the free liquid surface of the ship, using the method of alternating the motion reference coordinate system and the sliding grid to simulate the rotation of the propeller, and selecting the overlapping grid method to calculate the hull pitch and heave freedom movement; Step 2.2: Establish an automatic control method for the CFD numerical calculation model of the self-propulsion performance of the medium- and high-speed ship described in step 2.1: 1) Set the numerical solution convergence control process and divide the calculation process: the calculation process includes the flow field initialization stage, the hull flow field preliminary calculation stage, the propeller coupling flow field numerical calculation stage, the hull motion superimposed propeller rotation flow field calculation stage, the refined numerical simulation stage, and the ship self-propulsion point calculation and ship self-propulsion performance analysis stage; 2) Formulate the solution control method and convergence judgment method for the hull flow field preliminary calculation stage, the propeller coupling flow field numerical calculation stage, the hull motion superimposed propeller rotation flow field calculation stage and the refined numerical simulation stage in sequence; Step 2.3: Calculate the propeller received power: Combine the medium-high speed ship self-propulsion performance CFD numerical calculation model described in step 2.1 and the automatic control method of the model calculation process established in step 2.2 to establish a medium-high speed ship self-propulsion performance numerical calculation model, input the sample ship type three-dimensional geometric model file obtained in step 1, complete the medium-high speed ship self-propulsion point acquisition and ship self-propulsion performance characteristic parameter calculation and analysis, and output the propeller received power as the ship self-propulsion performance characteristic quantity; Step 3: Establish a method for optimizing the self-propulsion performance of medium- and high-speed ships: Step 3.1: Construct a 3D geometric model file of the deformed ship based on the hull deformation constraint conditions, and input it as a sample 3D geometric model file into step 2 to calculate the received power P of the ship propeller. D , to realize the numerical calculation of the self-propulsion performance of the modified ship type; Step 3.2: Use genetic algorithm to optimize step 3.1 to obtain the power P received by the ship propeller D , taking the tail deformation parameter as the independent variable, the calculated ship propeller received power as the objective function, and the ship type optimization design target P D The value required is used as the optimization target of the ship's self-propulsion performance, that is, the preset termination condition of the genetic algorithm; the ship propeller receives the power P after automatic output optimization D .

2. A method for evaluating and optimizing propulsion performance of medium- and high-speed ships according to claim 1, characterized in that: The method for extracting the automated ship type characteristic parameters in step 1 is: Step 1.1: Obtain the sample ship type 3D geometric model file in IGS / IGES format. The length unit of the 3D model file is "meter". The origin of the model coordinate is located at the intersection of the ship's stern perpendicular and the ship's baseline. The X-axis direction of the coordinate system is from the stern to the bow, the Y-axis direction is from the starboard side to the port side, and the Z-axis direction is from the bottom of the ship to the vertical upward direction of the deck; Step 1.2: Extract the three-dimensional geometric feature parameters of the ship type: Based on the sample ship type 3D geometric model file described in step 1.1, extract the ship type 3D geometric characteristic parameters, including: ship type main scale characteristic parameters, propeller scale characteristic parameters; The main characteristic parameters of the ship type include: ship design draft, ship vertical length, ship overall length, ship design waterline length, and ship type width; Ship design draft T d : Get by inputting parameter value; Length between vertical lines of the ship L BP : It is obtained by extracting the X-direction distance between the intersection of the bow and the design waterline and the stern perpendicular of the ship, in meters; Ship design waterline length L WL : Extract the ship design waterline based on the ship design draft, and obtain it by reading the distance between the front and rear ends of the design waterline along the X direction, in meters; Ship breadth B: obtained by extracting the maximum distance between the intersection of the starboard and port surfaces of the ship and the midline surface of the ship in the Y direction, in meters; The propeller scale characteristic parameters include: propeller diameter, propeller shaft height, distance between propeller disk and stern vertical line, distance between propeller blade tip and ship bottom, maximum X coordinate of propeller blade, minimum X coordinate of propeller blade, minimum distance between propeller blade and rudder blade in X direction; The propeller diameter D p 、Propeller shaft height H S , the distance between the propeller disk and the stern perpendicular line X P The parameters are obtained by inputting parameter values; among them, the propeller shaft height is the height of the propeller shaft from the baseline; Distance D between propeller blade and bottom of ship S :Extract the ship's mid-section line and x=X P The Z coordinate value of the intersection point of the plane P , D is calculated by the following formula s =Z p -(D p / 2+H s ); Maximum X coordinate of propeller blade Pmax and the minimum X coordinate of the propeller blade X Pmin : Establish a section at intervals of 0.01 meters along the Y direction, obtain the intersection line between the section and the propeller series, and extract the maximum X coordinate value of the intersection line to obtain the X Pmax value, the minimum X coordinate value is X Pmin value; Minimum distance X between propeller blade and rudder blade in X direction RPmin :Extract Z direction plane Z=(D p / 2+H S )The maximum X coordinate value of the intersection line between the plane and the rudder Rmax , X is calculated by the following formula RPmin Value: X RPmin =X Pmin -X RPmin ; Step 1.3: Extracting automated ship form characteristic parameters: Using the three-dimensional geometric characteristic parameters of the ship form in step 1.2 as automated ship form characteristic parameters; constructing an automated ship form characteristic parameter extraction program based on steps 1.1-1.2, with the input being the sample ship form three-dimensional geometric model file and the output being the automated ship form characteristic parameters.

3. A method for evaluating and optimizing the propulsion performance of a medium- and high-speed ship according to claim 2, characterized in that: The method for establishing the numerical calculation domain of the self-propulsion performance of medium- and high-speed ships in step 1 is: Step 1.4: Construct a fixed global coordinate system based on the model coordinate origin described in step 1.1 as input parameters; Step 1.5: Obtain the coordinates of the ship's center of gravity in the global coordinate system (X G ,Y G ,Z G ), and use this as the coordinate origin to construct a hull motion coordinate system that moves with the hull, with the initial direction of the coordinate axis being that the X-axis direction points to the bow, the Y-axis direction points to the port side of the hull, and the Z-axis direction is vertically upward. The hull motion coordinate system is rigidly connected to the hull and moves synchronously with the hull; Step 1.6: Based on the propeller shaft height H S , the distance between the propeller disk and the stern perpendicular line X P Parameters, obtain the coordinate value of the propeller center point in the hull motion coordinate system (X G -X P ,0,H S -Z G ), a propeller rotating coordinate system is constructed with the propeller center point as the coordinate origin. The propeller rotating coordinate system is rigidly connected to the hull and moves synchronously with the hull; Step 1.7: Based on the automated ship form characteristic parameters and the global coordinate system, the hull motion coordinate system and the propeller rotation coordinate system, an internal calculation domain wrapping the hull, an external background calculation domain and a propeller rotation calculation domain are constructed.

4. A method for evaluating and optimizing propulsion performance of medium- and high-speed ships according to claim 3, characterized in that: Step 1.7 The method for constructing the internal calculation domain that wraps the hull, the external background calculation domain, and the propeller rotation calculation domain is as follows: Step 1.7.1: Establish an internal computational domain that wraps the hull: The scale is set to the parameters associated with the hull support, and the vertical motion and rotational motion around the Y axis of the hull are opened for numerical calculation based on the trim and heave motion of the ship during navigation. The internal and external computational domains use the overlapping grid method to transfer the flow field data information; Step 1.7.2: Establish an external background calculation domain: The shape of the external background calculation domain is set to a rectangle to avoid the interference effect of the pool wall during the calculation process. The scale of the external background calculation domain is set to the parameters associated with the main scale of the hull and remains stationary during the calculation process; Step 1.7.3: Establish propeller rotation calculation domain: The propeller rotation calculation domain is arranged at the stern shaft of the ship, and the propeller is wrapped in a cylinder. The axis of the cylinder is consistent with the propeller axis, and the scale of the cylinder is established in step 1.2 to associate the extracted hull parameters with the propeller scale characteristic parameters.

5. A method for evaluating and optimizing propulsion performance of medium- and high-speed ships according to claim 1, characterized in that: In step 2.2, the steps of establishing the automatic control method include: Step 2.2.1: Set the numerical solution convergence control process and divide the calculation process: the numerical solution convergence control process is the process from the completion of the calculation domain flow field initialization to the convergence of the numerical calculation of the propeller coupling under the multi-degree-of-freedom motion of the hull; the calculation process includes: the flow field initialization stage, the hull flow field preliminary calculation stage, the propeller coupling flow field numerical calculation stage, the hull motion superimposed propeller rotation flow field calculation stage, the refined numerical simulation stage, and the ship self-propulsion point calculation and ship self-propulsion performance analysis stage; Step 2.2.2: Set the flow field initialization stage solution control method: The initial conditions of the CFD numerical calculation model for the self-propulsion performance of high-speed ships in this stage are set as follows: the propeller speed is set to 0, and the freedom of the hull movement is locked, that is, the hull and propeller are both fixed constraint models, and the propeller is actually a fixed component rigidly connected to the hull, and the rotation speed is not given; Input the ship speed into the CFD numerical calculation model of the medium- and high-speed ship self-propulsion performance in step 2.1 to solve the initialization flow field; the initialization flow field includes: the ship's initial speed and pressure parameters; Step 2.2.3: Set the control method for solving the preliminary calculation stage of the hull flow field: The initialized flow field is used as the initial condition of the CFD numerical calculation model of the self-propulsion performance of the high-speed ship in this stage. The time step is calculated based on the minimum grid size. At the same time, the freedom of the hull movement and the propeller rotation are continuously locked. The flow field near the hull is numerically iterated to solve the preliminary hull flow field; a curve for monitoring the change of hull resistance over time, namely the hull resistance curve, is established, and the curve is converged. If the convergence judgment condition is met, the next step is entered, and the preliminary hull flow field and hull resistance curve are output; Step 2.2.4: Control method for numerical calculation of propeller-coupled flow field: Based on the preliminary hull flow field as the initial condition of the CFD numerical calculation model of the self-propulsion performance of the medium- and high-speed ship in this stage, the propeller speed is set to solve the ship-propeller coupled flow field and perform convergence judgment; A1: Solve the propeller coupled flow field: lock the hull motion freedom, use the motion reference coordinate system method to calculate the propeller rotation effect, calculate the time step based on the minimum grid size, and set the propeller speed to the initial speed n o ; Solve the propeller-paddle coupled flow field under the action of propeller suction; A2: Convergence judgment: monitor and analyze the hull resistance, propeller thrust and propeller torque time history curves during the numerical calculation stage of the ship-propeller coupled flow field to see whether the convergence judgment conditions are met. If so, proceed to step 2.2.5; and output the force conditions of the propeller; Step 2.2.5: Solution control method for the stage of calculating the flow field of hull motion superimposed on propeller rotation: Based on the ship-propeller coupled flow field as the initial condition of the CFD numerical calculation model of the self-propulsion performance of high-speed ships in this stage, the hull motion superimposed on the propeller rotation flow field is calculated and convergence judgment is performed; B1: Solve the flow field of hull motion superimposed on propeller rotation: open the hull's degrees of freedom, use the motion reference coordinate system method to calculate the effect of propeller rotation, use the propeller speed to get the initial speed n0 calculated in step 2.2.4, calculate the time step based on the minimum grid size, and solve the flow field value of hull motion superimposed on propeller rotation; B2: Convergence judgment: During the calculation process, monitor the time history curves of the hull resistance, propeller thrust, propeller torque, hull trim value, and hull sinking over time, analyze and judge the convergence of the time history curves, and calculate the changes in the ship's navigation attitude and the force on the propeller under the action of the ship-propeller coupling. After reaching convergence, proceed to step 2.2.6; Step 2.2.6: Solve the control method in the refined numerical simulation stage: Based on the convergence conditions satisfied by the calculation in step 2.2.5, carry out refined numerical simulation of propeller-coupled multi-degree-of-freedom motion; C1: The hull motion superimposed propeller rotation flow field is used as the initial condition of the CFD numerical calculation model of the self-propulsion performance of the high-speed ship in this stage. The hull degree of freedom is opened, and the sliding grid method is used to calculate the real rotation of the propeller. The propeller speed is set to the initial speed n0, and the time step is calculated using formula (1); Wherein, in formula (1), n ​​is the initial speed n0, a is the propeller rotation angle control parameter in each time step, and its value ranges from 1 to 2; C2: Convergence judgment: monitor and analyze the time history curves of hull resistance, propeller thrust, propeller torque, hull trim value and hull sinking value in this stage respectively, and make convergence judgment. The overall mean value of the monitored values ​​calculated after the corresponding time history curve meets the convergence judgment conditions is taken as the corresponding hull resistance R′ under the initial speed n0 condition. 0B , propeller thrust T 0B and propeller torque Q 0B , hull trim value, hull sinking amount; Step 2.2.7: Calculation and solution of the ship's self-propulsion point control method: Based on the initial speed n0 calculated in step 2.2.6, the corresponding hull resistance R′ 0B , propeller thrust T 0B , propeller torque Q 0B , hull trim value, hull sinking amount; according to formula (2), determine the force balance relationship of the oar; ΔZ=T 0B -R’ 0B (2) When ΔZ = 0, the propeller speed n0 is the ship's self-propulsion speed n B , and the corresponding R′ 0B , T 0B , Q 0B are respectively the hull resistance R at the self-propulsion point B , propeller thrust T B , propeller torque T B Calculate the result data; when ΔZ≠0, reselect the propeller speed and return to step 2.2.6 to calculate until ΔZ=0; Step 2.2.8: Ship self-propulsion performance prediction method: Calculate the actual ship propeller received power P D ; P D =2*π*n B *Q B (3) The ship's self-propelled speed n B , propeller torque Q B .

6. A method for evaluating and optimizing the propulsion performance of a medium- and high-speed ship according to claim 5, characterized in that: The convergence judgment method is: S1: Based on formulas (4) to (7), the amplitude, amplitude mean and overall mean of the monitored values ​​of the ship's resistance, propeller thrust, propeller torque, ship's trim value and ship's sinking time history curve within the set oscillation period are calculated respectively; A i =R Pi -R Ti (4) Among them, A i , R Pi , R Ti They represent the amplitude, peak and trough of the i-th oscillation cycle of the curve respectively. It represents the mean amplitude of the 10 selected oscillation cycles; The mean is calculated using formula (6) and formula (7); Among them, R 0i , R0 represent the mean value of the i-th oscillation period of the curve and the overall mean value of the monitoring quantity in all 10 oscillation periods respectively; S2: Based on formulas (8) to (9), the convergence judgment conditions of the time history curves of hull resistance, propeller thrust, propeller torque, hull trim value and hull sinking value are calculated. Formula (8) is the ratio of the amplitude mean of the latest 10 change cycles of the time history curve to the overall mean of the monitored quantity is less than ε1, and ε1 is 5%; Formula (9) is that the difference between the maximum value of the mean of the monitored quantity in each period of the time history curve and the overall mean accounts for a percentage of the overall mean that is less than ε2, and ε2 is 1% to 2%; When all the time history curves obtained in this stage meet the convergence judgment conditions at the same time, the calculation is judged to have reached convergence, and the overall mean values ​​of the monitored values ​​calculated after the time history curves of hull resistance, propeller thrust, propeller torque, hull trim value, and hull sinking meet the convergence judgment conditions are respectively used as the hull resistance R′ corresponding to the initial speed n0 condition. 0B , propeller thrust T 0B and propeller torque Q 0B , hull trim value, hull sinking amount; the calculation process enters the next step.

7. A method for evaluating and optimizing propulsion performance of medium- and high-speed ships according to claim 5, characterized in that: The method for calculating the time step based on the minimum grid size is: Among them, Δt is the time step; is the reference velocity, which is taken as the incoming flow velocity in the computational domain; Δx is the minimum grid size in the flow direction, i.e., the x direction; C MAX is the Courant number, which is set to 10.

8. A method for evaluating and optimizing propulsion performance of medium- and high-speed ships according to claim 5, characterized in that: The initial speed n described in A1 o The calculation method is: A11: Estimate the initial thrust T0 of the ship according to formula (11); Where R0 is the overall mean value of the monitored quantity calculated based on the time history curve of the hull resistance, that is, the mean value of the ship resistance; t is the thrust reduction fraction, which ranges from 0.15 to 0.25 depending on the ship type; A12: Obtaining corresponding propeller open water characteristic data based on the ship type: the propeller open water characteristic data includes: the thrust coefficient K corresponding to the series advance coefficient J T , Torque coefficient K Q and open water efficiency η0 data; A121: Get thrust coefficient K T0 : Based on 75% of the maximum open water efficiency as input, interpolation is performed on the propeller open water characteristic data curve to obtain the thrust coefficient K T0 ; A13: Estimate the initial propeller speed n according to formula (12) o : Where ρ is the density of seawater and D is the propeller diameter.

9. A method for evaluating and optimizing the propulsion performance of a medium- and high-speed ship according to claim 8, characterized in that: In step 2.2.7, when ΔZ≠0, the processing method is: 1) If ΔZ < 0, it means that the thrust from the propeller cannot overcome the resistance of the hull, and the propeller speed needs to be increased. The new speeds n1, n2, and n3 are calculated using formulas (13) to (16), where K T0B The propeller thrust coefficient corresponding to the speed n0, ρ is the density of seawater, and D is the propeller diameter; n2=n1+(n1-n0) (15) n3=n2+(n1-n0) (16) Return to step 2.2.6, adjust the propeller speed to n1, n2, and n3 respectively, perform convergence judgment, obtain the corresponding hull resistance, propeller thrust, and propeller torque when the propeller speed is n1, n2, and n3 respectively, and calculate the corresponding ΔZ1, ΔZ2, and ΔZ3 at the three speeds based on formula (2); use the hull resistance, propeller thrust, and propeller torque data at the four speeds of n0, n1, n2, and n3, and perform cubic spline interpolation with ΔZ=0 as the input condition to obtain the propeller speed n that satisfies the condition of ΔZ=0. B 、Hull resistance R B , propeller thrust T B , propeller torque Q B ; 2) If ΔZ>0, it means that the thrust of the propeller is too large and the propeller speed needs to be reduced. The new speeds n1, n2, and n3 are calculated using formulas (13), (17) to (19), where K T0B The propeller thrust coefficient corresponding to the speed n0, ρ is the density of fresh water, and D is the propeller diameter; n2=n1-(n0-n1) (18) n3=n2-(n0-n1) (19) The propeller speeds are adjusted to n1, n2, and n3 respectively, and the refined numerical simulation of ship self-propulsion is carried out using step 2.2.6, and the convergence conditions are reached. The corresponding hull resistance, propeller thrust and torque under the propeller speeds n1, n2, and n3 are obtained respectively. At the same time, the corresponding ΔZ1, ΔZ2, and ΔZ3 under the three speeds are calculated based on formula (2); the corresponding series data under the four speeds n0, n1, n2, and n3 are used, and the cubic spline interpolation is performed with ΔZ=0 as the input condition to obtain the propeller speed n that satisfies the condition of ΔZ=0. B 、Hull resistance R B , propeller thrust T B , propeller torque Q B .

10. A method for evaluating and optimizing propulsion performance of medium- and high-speed ships according to claim 1, characterized in that: Step 3.1 is a method for obtaining a three-dimensional geometric model file after the ship is deformed: using parametric modeling software, establishing a parametric deformation model of the ship's stern, changing the deformation parameters of the hull stern based on the hull deformation constraint conditions, realizing the transformation of the stern's three-dimensional geometric model, and obtaining a three-dimensional geometric model file after the ship is deformed.

11. A system for evaluating and optimizing the propulsion performance of a medium- and high-speed ship based on any one of claims 1 to 10, characterized in that: Ship type transformation subsystem: including: a ship tail deformation unit for establishing a ship tail parametric deformation model based on parametric modeling software; a ship type deformation parameter acquisition unit for changing the deformation parameters of the hull tail to achieve the transformation of the stern three-dimensional geometric model, and obtaining the three-dimensional geometric model file after the ship type deformation as the sample ship type three-dimensional geometric model file; The self-propulsion performance evaluation subsystem includes: a calculation domain unit for establishing a numerical calculation domain for the self-propulsion performance of a medium-high-speed ship; a medium-high-speed ship self-propulsion performance CFD numerical calculation model unit for conditionally configuring the medium-high-speed ship self-propulsion performance numerical calculation domain and establishing a medium-high-speed ship self-propulsion performance CFD numerical calculation model; a model control unit for establishing an automatic control method for the medium-high-speed ship self-propulsion performance CFD numerical calculation model; a ship self-propulsion performance numerical calculation model unit for establishing a medium-high-speed ship self-propulsion performance numerical calculation model in combination with the medium-high-speed ship self-propulsion performance CFD numerical calculation model and the automatic control method; a model calculation unit for inputting a sample ship three-dimensional geometric model file obtained by the ship transformation subsystem into the medium-high-speed ship self-propulsion performance numerical calculation model and calculating the power received by the ship propeller; Medium and high-speed ship self-propulsion performance optimization subsystem: including: a condition preset unit for setting the ship self-propulsion performance optimization target as the genetic algorithm termination condition, and a self-propulsion performance optimization unit based on the ship propeller received power obtained by optimizing the self-propulsion performance evaluation subsystem based on the genetic algorithm.

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