Control method and system of ship bottom porous slot gas-liquid dual-purpose composite drag reduction device, electronic equipment and readable storage medium

Abstract

The present application provides a control method and system for a ship bottom porous slot gas-liquid dual-purpose composite drag reduction device, an electronic device and a storage medium, which solves the problems of large test interference, difficult parameter optimization and not deep mechanism analysis in the existing blowing and suction drag reduction control method. The present application uses direct numerical simulation technology to establish a flat plate physical model, sets up a coordinate system and velocity components, and generates a structured calculation grid; based on the grid, input the fluid physical parameters and the blowing and suction disturbance controlled by the disturbance amplitude, frequency and region number, construct the initial flow field; use the finite difference method to solve the continuity equation, momentum equation and pressure Poisson equation, and output the transient flow field data iteratively; monitor the average friction velocity to determine the convergence; post-processing generates the velocity distribution curve, drag evolution curve and vortex structure cloud chart, analyzes the regulation and control mechanism and determines the optimal control parameters, and realizes the precise control of the blowing and suction mode of the drag reduction device.

Description

Technical Field

[0001] This invention relates to the field of control technology, and in particular to active control and drag reduction technology for ship turbulent boundary layers. Background Technology

[0002] When a ship navigates in water, the viscous interaction between the hull and the water creates a turbulent boundary layer. The frictional drag generated by this layer accounts for 60%-80% of the ship's total drag, making it a core factor affecting navigation efficiency and increasing energy consumption. Active flow control technology is a research hotspot in the field of ship drag reduction. Among these technologies, wall-blowing / suction control, by arranging microslits or micropore arrays on the hull bottom to inject or pump fluid into the near-wall region, reconstructs the coherent structure of the turbulent boundary layer (such as suppressing sudden events and breaking up flow-direction vortices), thereby effectively reducing wall frictional drag. It boasts advantages such as significant drag reduction effects and wide applicability, and has become an important development direction for drag reduction technology in large ships.

[0003] Currently, the evaluation of drag reduction effects of hull-side blow-suction systems mainly relies on full-scale ship tests or model tests. These tests require sophisticated instruments such as micro-blowing devices, force balances, hot-wire anemometers, and particle image velocimeters to quantitatively measure the drag reduction effect. However, this approach faces significant technical bottlenecks: firstly, the complex environment of full-scale ship tests, including fluctuations in sea state, the cleanliness of the hull surface, and changes in paint performance, can all interfere with the results, making it difficult to control a single variable; secondly, if the experimental design does not strictly isolate irrelevant variables, the drag reduction effect resulting from hull surface optimization can easily be mistakenly attributed to the blow-suction control device, leading to a false overestimation of the drag reduction technology's performance and severely impacting the scientific validity and engineering application value of the experimental conclusions. Furthermore, full-scale ship tests and model tests also suffer from high costs, lengthy cycles, and significant trial-and-error challenges, making it difficult to quickly optimize the design of blow-suction control parameters.

[0004] Direct numerical simulation, as a high-precision numerical calculation method in the field of fluid mechanics, can accurately solve the Navier-Stokes equations without introducing turbulence model assumptions. It can provide high spatiotemporal resolution flow data for the entire flow field and has been widely used in fields such as turbulent boundary layer control and fluid flow mechanism research. While some studies in the current technology have used numerical simulation methods to explore the drag reduction effect of blowing and suction, most suffer from problems such as insufficiently systematic control methods, imprecise parameter design, and a disconnect between simulation results and engineering realities. This makes it difficult to achieve precise control of the multi-hole slit gas-liquid dual-purpose drag reduction device at the bottom of a ship, and thus cannot provide reliable technical support for the device's engineering application. Furthermore, existing numerical simulation methods mostly focus on the influence analysis of single blowing and suction parameters, lacking a systematic study of the drag reduction mechanism under the synergistic effect of multiple parameters, making it difficult to meet the control requirements of drag reduction devices under different navigation conditions.

[0005] Based on this, and combining the research results of numerical simulation of ship turbulent boundary layer and wall blowing and suction control, it is urgent to propose a scientific, rigorous, and systematic control method and control system for a multi-hole slit gas-liquid dual-purpose composite drag reduction device for ship bottom. Direct numerical simulation technology should be used to avoid interference from actual ship tests, so as to achieve accurate quantification of the blowing and suction drag reduction effect and optimized design of control parameters. This will solve the problems of low accuracy, poor adaptability, and disconnect from engineering practice of existing control methods, and promote the engineering application of ship bottom blowing and suction drag reduction technology. Summary of the Invention

[0006] To address the shortcomings of existing technologies, such as reliance on actual ship tests or model tests, which prevent independent quantitative analysis of single blow-suction control variables; the limitations of numerical simulation methods that focus primarily on the influence of single blow-suction parameters and lack systematic research on drag reduction mechanisms under the synergistic effect of multiple parameters; and the problems of high cost, long cycle, and difficulty in trial and error in experimental methods, this invention proposes a control method for a multi-hole slit gas-liquid dual-purpose composite drag reduction device at the bottom of a ship. The method includes: Step 1: Establish a physical model of the flat plate using direct numerical simulation technology, set the coordinate system and velocity components, set the geometric parameters and boundary conditions of the model, and generate a structured computational mesh; Step 2: Based on the structured computational grid, input the fluid property parameters and the blowing and suction disturbance control parameters, where the blowing and suction disturbance is controlled by the disturbance amplitude, disturbance frequency, and number of disturbance regions and satisfies the control equation, and construct the initial flow field and wall boundary condition function; Step 3: Solve the continuity equation, momentum equation and pressure Poisson equation using the finite difference method, iterate using a time-progression scheme, update the wall normal velocity boundary conditions in real time, and output transient flow field data; Step 4: Monitor the evolution of the average friction velocity. When the fluctuation amplitude of the average friction velocity is within the set threshold and the duration exceeds the turbulence integral time scale, the calculation is considered to have converged, and the flow field snapshot and drag time series data are saved. Step 5: Post-process the saved flow field snapshots and drag time series data to generate velocity distribution curves, drag evolution curves, vortex structure cloud maps, and flow field visualization maps. Analyze the control mechanism of blowing and suction disturbances on the coherent structure of the turbulent boundary layer, and then determine the optimal blowing and suction control parameters to achieve precise control of the blowing and suction mode of the multi-hole slit gas-liquid dual-purpose composite drag reduction device at the bottom of the ship.

[0007] Furthermore, in step one, The coordinate system is set as follows: x The axis is along the direction of the ship's flow. y The shaft runs along the ship's span. z The axis runs along the normal direction of the ship's bottom wall. The velocity component is defined as the flow velocity. u Spread speed vnormal velocity of the wall w ; The half-height of the channel in the flat panel model is set to h, and the reference length is L. x =6h, reference width L z =4h; The boundary conditions are set as follows: no-slip boundary conditions are used on the top and bottom walls, and periodic boundary conditions are used in the spanwise and flow directions. The structured computational grid is refined in the near-wall region, and the number of grid cells is adaptively adjusted according to the computational accuracy requirements.

[0008] Furthermore, in step two, The control equations for the blow-suction disturbance are:

[0009] in, The velocity is the normal velocity to the bottom wall of the ship. The time-perturbation function that evolves over time; The amplitude of the blowing and suction disturbance; The number of disturbance regions in the direction of flow; This represents the number of perturbation regions in the spanwise direction; x , z These are spatial coordinates.

[0010] Furthermore, Disturbance time function The form can be a sine function, a trapezoidal function, or a pulse function; Blowing and sucking disturbance amplitude The value ranges from 0.01 to 0.1 times the reference speed; Number of disturbed areas and All are positive integers.

[0011] Furthermore, in step three, The finite difference method employs a semi-implicit time-progression scheme for the momentum equation; The pressure Poisson equation is solved using the conjugate gradient method.

[0012] Furthermore, in step four, The threshold value for the fluctuation range of the average friction speed is set to be no more than 5%. The duration is no less than 10 turbulence integral time scales.

[0013] Furthermore, in step five, The post-processing also outputs Reynolds stress distribution, vorticity field distribution, and boundary layer thickness evolution data; The optimal blowing and suction control parameters are determined by comparing the drag reduction rate and net energy saving rate under different combinations of disturbance amplitude, disturbance time function form and number of disturbance regions.

[0014] This invention proposes a control system for a multi-hole slit gas-liquid dual-purpose composite drag reduction device for ship bottoms, comprising: The modeling module is used to establish a physical model of the flat plate using direct numerical simulation technology, set the coordinate system and velocity components, set the geometric parameters and boundary conditions of the model, and generate a structured computational mesh. The parameter initialization module is used to input fluid property parameters and blow-suction disturbance control parameters based on the structured computing grid. The blow-suction disturbance is controlled by the disturbance amplitude, disturbance frequency, and number of disturbance regions and satisfies the control equation. The module constructs the initial flow field and wall boundary condition functions. The governing equation solving module is used to solve the continuity equation, momentum equation and pressure Poisson equation using the finite difference method. It adopts a time-progression format for iterative calculation and updates the wall normal velocity boundary conditions in real time, outputting transient flow field data. The convergence judgment module is used to monitor the evolution of the average friction velocity. When the fluctuation amplitude of the average friction velocity is within a set threshold and the duration exceeds the turbulence integral time scale, the calculation is judged to be converged, and the flow field snapshot and drag time series data are saved. The post-processing module is used to post-process the saved flow field snapshots and drag time series data to generate velocity distribution curves, drag evolution curves, vortex structure cloud maps and flow field visualization maps. It analyzes the regulation mechanism of blowing and suction disturbances on the coherent structure of the turbulent boundary layer, and then determines the optimal blowing and suction control parameters to achieve precise control of the blowing and suction mode of the multi-hole slit gas-liquid dual-purpose composite drag reduction device at the bottom of the ship.

[0015] The present invention proposes an electronic device, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps of the above-described method.

[0016] The present invention proposes a computer-readable storage medium for storing computer instructions, which, when executed by a processor, implement the steps of the above-described method.

[0017] The beneficial effects of this invention are: To address the aforementioned problems, this invention proposes a control method, system, electronic equipment, and readable storage medium for a multi-hole slit gas-liquid dual-purpose drag reduction device for ship bottoms, offering the following improvements: 1. This invention uses direct numerical simulation technology to construct an idealized physical model of a flat plate, accurately fixes irrelevant variables such as wall roughness and fluid properties, and realizes independent quantitative analysis of a single blow-suction control parameter. This effectively avoids environmental interference in actual ship tests, ensures the scientificity and accuracy of drag reduction effect evaluation, and solves the problem of low reliability of existing test methods.

[0018] 2. This invention outputs high spatiotemporal resolution transient data of the entire flow field through direct numerical simulation, and uses post-processing to generate velocity distribution curves, drag evolution curves, vortex structure cloud maps, and flow field visualization maps. It can visualize the evolution process of the coherent structure of the turbulent boundary layer, and deeply reveal the regulation mechanism of blow-suction disturbance on sudden events, flow vortices, and Reynolds stress. It provides a direct theoretical basis for the optimization design of blow-suction control parameters, and makes up for the shortcomings of insufficient mechanism analysis and inaccurate parameter design in the existing technology.

[0019] 3. This method can quickly screen combinations of different disturbance amplitudes, disturbance time function forms, and the number of disturbance regions before conducting time-consuming and expensive physical experiments, identify the optimal control scheme in advance, significantly reduce the trial and error costs and technical risks of subsequent experiments, and shorten the development cycle of drag reduction devices.

[0020] 4. This invention follows the modular design principle to write the control program, and the parameters can be adjusted flexibly. The blowing and suction disturbance parameters can be adjusted according to different ship types and different navigation conditions, such as speed and draft. It is adapted to different working modes of the multi-hole slit gas-liquid dual-purpose composite drag reduction device at the bottom of the ship, which improves the adaptability and versatility of the control method. It can be widely used in large displacement ships such as bulk carriers, oil tankers, and container ships. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0022] Figure 1 A schematic diagram of the physical model structure of the flat plate established for this invention; Figure 2 A schematic diagram of the perturbation region structure added to the bottom of the physical model of the flat plate established in this invention; Figure 3 This is a schematic diagram of the velocity distribution curve of the present invention; Figure 4 This is a schematic diagram of the vortex structure of the present invention. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] This invention uses Direct Numerical Simulation (DNS) as its core, employs a dedicated control program written in Fortran, and compiles and runs it using Visual Studio software. By numerically solving the fluid dynamics control equations consisting of the continuity equation, momentum equation, and pressure Poisson equation, it accurately outputs core parameters such as velocity components and friction drag coefficients in the near-wall region of the ship's bottom. Professional post-processing techniques are used to analyze the simulation data, generating velocity distribution curves, drag evolution curves, vortex structure visualization diagrams, and flow field vector diagrams. This allows for the quantitative analysis of the influence of blowing and suction disturbance parameters on the ship's turbulence drag reduction effect, achieving precise control of the blowing and suction mode of the multi-slit gas-liquid dual-purpose composite drag reduction device at the ship's bottom.

[0025] Combination Figures 1-4 This invention proposes a control method for a multi-hole slit gas-liquid dual-purpose composite drag reduction device for ship bottoms, the method comprising: Step 1: Establish a physical model of the flat plate using direct numerical simulation technology, set the coordinate system and velocity components, set the geometric parameters and boundary conditions of the model, and generate a structured computational mesh; Furthermore, in step one, The coordinate system is set as follows: x The axis is along the direction of the ship's flow. y The shaft runs along the ship's span. z The axis runs along the normal direction of the ship's bottom wall. The velocity component is defined as the flow velocity. u Spread speed v normal velocity of the wall w ; The half-height of the channel in the flat panel model is set to h, and the reference length is L. x =6h, reference width L z =4h; This size setting balances computational accuracy and efficiency, and can accurately simulate the turbulent boundary layer flow characteristics in the flat area of ​​the ship's bottom. The boundary conditions are set as follows: no-slip boundary conditions are used on the top and bottom walls, and periodic boundary conditions are used in the spanwise and flow directions. The structured computational grid is refined in the near-wall region, and the number of grid cells is adaptively adjusted according to the computational accuracy requirements.

[0026] Specifically, no-slip boundary conditions are applied to the top and bottom walls to closely match the actual flow state on the ship's bottom wall; periodic boundary conditions are used in the spanwise and flow-direction directions to eliminate the interference of boundary effects on the simulation results and ensure the continuity and realism of the simulated flow field. The model uses a structured mesh, with finer meshing in the near-wall region. The number of meshes can be adaptively adjusted according to the accuracy requirements of the numerical calculation, ensuring that the mesh resolution in the near-wall region meets the requirements for fine calculation of the turbulent boundary layer and effectively captures the flow details and coherent structure in the near-wall region.

[0027] Step 2: Based on the structured computational grid, input the fluid property parameters and the blowing and suction disturbance control parameters, where the blowing and suction disturbance is controlled by the disturbance amplitude, disturbance frequency, and number of disturbance regions and satisfies the control equation, and construct the initial flow field and wall boundary condition function; Furthermore, in step two, The control equations for the blow-suction disturbance are:

[0028] in, The velocity is the normal velocity to the bottom wall of the ship. The time-perturbation function that evolves over time; The amplitude of the blowing and suction disturbance; The number of disturbance regions in the direction of flow; This represents the number of perturbation regions in the spanwise direction; x , z These are spatial coordinates.

[0029] Furthermore, Disturbance time function The form can be a sine function, a trapezoidal function, or a pulse function; Blowing and sucking disturbance amplitude The value ranges from 0.01 to 0.1 times the reference speed; Number of disturbed areas and All are positive integers.

[0030] Specifically, the blow-suction disturbance is a periodic wall-normal disturbance, and its motion state is controlled by core parameters such as disturbance amplitude, disturbance frequency, and number of disturbance regions. In the control equations of the blow-suction disturbance, The normal velocity of the ship's bottom wall represents the intensity and direction of the blowing and suction disturbance. The disturbance time function evolves over time and is used to describe the dynamic change of velocity in a single blow-suction cycle. Its function form can be adjusted to a sine function, trapezoidal function, or pulse function according to the actual drag reduction requirements. The sine function form is suitable for smooth blow-suction control, while the pulse function form is suitable for high-intensity instantaneous blow-suction control. The value is the amplitude of the blowing and suction disturbance, ranging from 0.01 to 0.1 times the reference velocity, and is used to control the intensity of the blowing and suction disturbance. , These are the number of disturbance regions in the flow direction and the spanwise direction, respectively, both of which are positive integers, used to define the spatial distribution density of blowing and suction disturbances; x , z These are spatial coordinates, corresponding to the flow direction and wall normal position of the flat plate model.

[0031] Step 3: Solve the continuity equation, momentum equation and pressure Poisson equation using the finite difference method, iterate using a time-progression scheme, update the wall normal velocity boundary conditions in real time, and output transient flow field data; Furthermore, in step three, The finite difference method employs a semi-implicit time-progression scheme for the momentum equation; The pressure Poisson equation is solved using the conjugate gradient method.

[0032] Step 4: Monitor the evolution of the average friction velocity. When the fluctuation amplitude of the average friction velocity is within the set threshold and the duration exceeds the turbulence integral time scale, the calculation is considered to have converged, and the flow field snapshot and drag time series data are saved. Furthermore, in step four, The threshold value for the fluctuation range of the average friction speed is set to be no more than 5%. The duration is no less than 10 turbulence integral time scales.

[0033] Specifically, during the numerical simulation, the average frictional velocity (UTAU) is used as the criterion for judging the convergence of the calculation. When the average frictional velocity fluctuates within a set threshold range, and the fluctuation amplitude does not exceed 5% and lasts for no less than 10 turbulent integral time scales, the numerical calculation is judged to be fully converged, the calculation is stopped, and the calculation results are saved.

[0034] Step 5: Post-process the saved flow field snapshots and drag time series data to generate velocity distribution curves, drag evolution curves, vortex structure cloud maps, and flow field visualization maps. Analyze the control mechanism of blowing and suction disturbances on the coherent structure of the turbulent boundary layer, and then determine the optimal blowing and suction control parameters to achieve precise control of the blowing and suction mode of the multi-hole slit gas-liquid dual-purpose composite drag reduction device at the bottom of the ship.

[0035] Furthermore, in step five, The post-processing also outputs Reynolds stress distribution, vorticity field distribution, and boundary layer thickness evolution data; The optimal blowing and suction control parameters are determined by comparing the drag reduction rate and net energy saving rate under different combinations of disturbance amplitude, disturbance time function form and number of disturbance regions.

[0036] Specifically, the post-processing process uses professional fluid dynamics post-processing tools to process the raw data output from the numerical simulation. In addition to generating velocity curves, drag curves, vortex structures, and flow field diagrams, it can also output key data such as Reynolds stress distribution, vorticity field distribution, and boundary layer thickness evolution, comprehensively revealing the control mechanism of blowing and suction disturbances on the turbulent boundary layer.

[0037] This invention proposes a control system for a multi-hole slit gas-liquid dual-purpose composite drag reduction device for ship bottoms, comprising: The modeling module is used to establish a physical model of the flat plate using direct numerical simulation technology, set the coordinate system and velocity components, set the geometric parameters and boundary conditions of the model, and generate a structured computational mesh. The parameter initialization module is used to input fluid property parameters and blow-suction disturbance control parameters based on the structured computing grid. The blow-suction disturbance is controlled by the disturbance amplitude, disturbance frequency, and number of disturbance regions and satisfies the control equation. The module constructs the initial flow field and wall boundary condition functions. The governing equation solving module is used to solve the continuity equation, momentum equation and pressure Poisson equation using the finite difference method. It adopts a time-progression format for iterative calculation and updates the wall normal velocity boundary conditions in real time, outputting transient flow field data. The convergence judgment module is used to monitor the evolution of the average friction velocity. When the fluctuation amplitude of the average friction velocity is within a set threshold and the duration exceeds the turbulence integral time scale, the calculation is judged to be converged, and the flow field snapshot and drag time series data are saved. The post-processing module is used to post-process the saved flow field snapshots and drag time series data to generate velocity distribution curves, drag evolution curves, vortex structure cloud maps and flow field visualization maps. It analyzes the regulation mechanism of blowing and suction disturbances on the coherent structure of the turbulent boundary layer, and then determines the optimal blowing and suction control parameters to achieve precise control of the blowing and suction mode of the multi-hole slit gas-liquid dual-purpose composite drag reduction device at the bottom of the ship.

[0038] The present invention proposes an electronic device, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps of the above-described method.

[0039] The present invention proposes a computer-readable storage medium for storing computer instructions, which, when executed by a processor, implement the steps of the above-described method.

[0040] The control program of this invention follows a modular design principle and is divided into four core modules. The functions of each module are as follows: Parameter initialization module: used to input the geometric parameters, fluid property parameters (density, dynamic viscosity), boundary condition parameters, blowing and suction disturbance parameters (amplitude, frequency, number of disturbance regions), and calculation convergence criteria of the calculation model, completing the parameter configuration before calculation and ensuring the standardization and consistency of the calculation process; Control equation solving module: uses the finite difference method to discretize and solve the continuity equation, momentum equation, and pressure Poisson equation. The momentum equation adopts a semi-implicit time-progression scheme, and the pressure Poisson equation adopts the conjugate gradient method to ensure the stability and convergence of the calculation and improve the calculation accuracy; Boundary condition loading module: used to load the no-slip boundary conditions, periodic boundary conditions, and blowing and suction disturbance boundary conditions of the model, and update the wall normal velocity in real time to ensure that the boundary conditions are consistent with the actual blowing and suction process; Data output module: used to output the original data such as velocity components, pressure, and friction drag coefficient in real time during the calculation process, and save the data according to the preset time step for subsequent post-processing analysis.

[0041] This invention provides a control method for a multi-hole slit gas-liquid dual-purpose composite drag reduction device for ship bottoms, the specific implementation steps of which are as follows: A flat-plate computational model was established, defining seawater properties, boundary conditions, blow-suction disturbance parameters, and convergence criteria. A near-wall refined structured mesh was used. The fluid control equations were solved using Fortran modular programming, and the solution was debugged in Visual Studio, outputting flow field and drag data at fixed step sizes. The program was run and the average friction velocity was monitored. The calculation stopped and the data was saved after reaching a stable convergence threshold. ParaView was used for data visualization and mechanism analysis, and the optimal blow-suction control scheme was obtained through comparison of multiple sets of parameters.

[0042] Furthermore, the geometric parameters, fluid properties, and bleed / suction disturbance parameters of the flat plate model can be adjusted according to actual drag reduction requirements. For example, the reference length can be adjusted for different ship types. With reference width Adjust the incoming current speed according to different navigation conditions. With the amplitude of blowing and sucking disturbance Adjust the perturbation time function for different blowing and sucking modes. This allows for precise control of drag reduction devices in different scenarios.

[0043] This invention belongs to the field of active control and drag reduction technology for ship turbulent boundary layer, and provides a control method for a multi-slot gas-liquid dual-purpose composite drag reduction device at the ship's bottom. This method uses direct numerical simulation (DNS) as its core technology, employs Fortran programming language to write the control program, compiles and runs it based on the Visual Studio development environment, and accurately obtains key parameters such as the velocity field, pressure field, and drag coefficient in the near-wall region of the ship's bottom by solving fluid dynamics control equations such as the continuity equation, momentum equation, and pressure Poisson equation. Through professional post-processing of the simulation results, data such as velocity distribution curves, drag evolution curves, vortex structure cloud maps, and flow field visualization maps are generated. The method systematically analyzes the regulation mechanism and drag reduction effect of blowing and suction disturbance parameters on the coherent structure of the ship's turbulent boundary layer. This method effectively avoids technical bottlenecks such as environmental interference and difficulties in variable control in actual ship tests, and achieves accurate quantitative evaluation of the blowing and suction drag reduction effect and optimized design of control parameters, providing scientific and reliable theoretical support and technical guidance for the engineering application of multi-slot gas-liquid dual-purpose composite drag reduction devices at the ship's bottom.

[0044] The control method, system, electronic equipment, and readable storage medium of the multi-hole slit gas-liquid dual-purpose composite drag reduction device for ship bottom proposed in this invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this invention. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A control method for a multi-hole slit gas-liquid dual-purpose composite drag reduction device for ship bottom, characterized in that, Includes the following steps: Step 1: Establish a physical model of the flat plate using direct numerical simulation technology, set the coordinate system and velocity components, set the geometric parameters and boundary conditions of the model, and generate a structured computational mesh; Step 2: Based on the structured computational grid, input the fluid property parameters and the blowing and suction disturbance control parameters, where the blowing and suction disturbance is controlled by the disturbance amplitude, disturbance frequency, and number of disturbance regions and satisfies the control equation, and construct the initial flow field and wall boundary condition function; Step 3: Solve the continuity equation, momentum equation and pressure Poisson equation using the finite difference method, iterate using a time-progression scheme, update the wall normal velocity boundary conditions in real time, and output transient flow field data; Step 4: Monitor the evolution of the average friction velocity. When the fluctuation amplitude of the average friction velocity is within the set threshold and the duration exceeds the turbulence integral time scale, the calculation is considered to have converged, and the flow field snapshot and drag time series data are saved. Step 5: Post-process the saved flow field snapshots and drag time series data to generate velocity distribution curves, drag evolution curves, vortex structure cloud maps, and flow field visualization maps. Analyze the control mechanism of blowing and suction disturbances on the coherent structure of the turbulent boundary layer, and then determine the optimal blowing and suction control parameters to achieve precise control of the blowing and suction mode of the multi-hole slit gas-liquid dual-purpose composite drag reduction device at the bottom of the ship.

2. The method according to claim 1, characterized in that, In step one, The coordinate system is set as follows: x The axis is along the direction of the ship's flow. y The shaft runs along the ship's span. z The axis runs along the normal direction of the ship's bottom wall. The velocity component is defined as the flow velocity. u Spread speed v normal velocity of the wall w ; The half-height of the channel in the flat panel model is set to h, and the reference length is L. x =6h, reference width L z =4h; The boundary conditions are set as follows: no-slip boundary conditions are used on the top and bottom walls, and periodic boundary conditions are used in the spanwise and flow directions. The structured computational grid is refined in the near-wall region, and the number of grid cells is adaptively adjusted according to the computational accuracy requirements.

3. The method according to claim 1, characterized in that, In step two, The control equations for the blow-suction disturbance are: in, The velocity is the normal velocity to the bottom wall of the ship. The time-perturbation function that evolves over time; The amplitude of the blowing and suction disturbance; The number of disturbance regions in the direction of flow; This represents the number of perturbation regions in the spanwise direction; x , z These are spatial coordinates.

4. The method according to claim 3, characterized in that, Disturbance time function The form can be a sine function, a trapezoidal function, or a pulse function; Blowing and sucking disturbance amplitude The value ranges from 0.01 to 0.1 times the reference speed; Number of disturbed areas and All are positive integers.

5. The method according to claim 1, characterized in that, In step three, The finite difference method employs a semi-implicit time-progression scheme for the momentum equation; The pressure Poisson equation is solved using the conjugate gradient method.

6. The method according to claim 1, characterized in that, In step four, The threshold value for the fluctuation range of the average friction speed is set to be no more than 5%. The duration is no less than 10 turbulence integral time scales.

7. The method according to claim 1, characterized in that, In step five, The post-processing also outputs Reynolds stress distribution, vorticity field distribution, and boundary layer thickness evolution data; The optimal blowing and suction control parameters are determined by comparing the drag reduction rate and net energy saving rate under different combinations of disturbance amplitude, disturbance time function form and number of disturbance regions.

8. A control system for a multi-hole slit gas-liquid dual-purpose composite drag reduction device for ship bottoms, characterized in that, include: The modeling module is used to establish a physical model of the flat plate using direct numerical simulation technology, set the coordinate system and velocity components, set the geometric parameters and boundary conditions of the model, and generate a structured computational mesh. The parameter initialization module is used to input fluid property parameters and blow-suction disturbance control parameters based on the structured computing grid. The blow-suction disturbance is controlled by the disturbance amplitude, disturbance frequency, and number of disturbance regions and satisfies the control equation. The module constructs the initial flow field and wall boundary condition functions. The governing equation solving module is used to solve the continuity equation, momentum equation and pressure Poisson equation using the finite difference method. It adopts a time-progression format for iterative calculation and updates the wall normal velocity boundary conditions in real time, outputting transient flow field data. The convergence judgment module is used to monitor the evolution of the average friction velocity. When the fluctuation amplitude of the average friction velocity is within a set threshold and the duration exceeds the turbulence integral time scale, the calculation is judged to be converged, and the flow field snapshot and drag time series data are saved. The post-processing module is used to post-process the saved flow field snapshots and drag time series data to generate velocity distribution curves, drag evolution curves, vortex structure cloud maps and flow field visualization maps. It analyzes the regulation mechanism of blowing and suction disturbances on the coherent structure of the turbulent boundary layer, and then determines the optimal blowing and suction control parameters to achieve precise control of the blowing and suction mode of the multi-hole slit gas-liquid dual-purpose composite drag reduction device at the bottom of the ship.

9. An electronic device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1-7.

10. A computer-readable storage medium for storing computer instructions, characterized in that, When the computer instructions are executed by the processor, they implement the steps of the method according to any one of claims 1-7.

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