Paddle-shaft-ship coupling modulation sound signal simulation analysis method

Abstract

The invention relates to a propeller-shaft-ship coupling modulation sound signal simulation analysis method. The invention relates to the technical field of ship vibration and noise reduction, and provides a propeller-shaft-ship coupling structure real-scale analysis model, coupling domain defining and assembling, grid dividing and grid unit type specifying, coupling surface interaction defining, structure connection relation constructing, load and initial condition applying, and Euler domain boundary and material distribution configuring. Vibration signal calculation and data processing are carried out, a paddle-shaft-ship coupling sound signal simulation analysis model is established, a vibration load is mapped, sound signal calculation and data processing are carried out, and the modulation coupling influence of the shaft frequency on the blade frequency in the sound signals is obtained. The method focuses on analyzing the characteristics of the shaft frequency, the leaf frequency and the double leaf frequency, quantifies the modulation coupling of the shaft frequency to the leaf frequency and the double leaf frequency, and fills the blank of frequency coupling analysis in existing simulation.

Description

Technical Field

[0001] This invention relates to the field of ship vibration reduction and noise reduction technology, and is a simulation analysis method for propeller-shaft-ship coupled modulation acoustic signals. Background Technology

[0002] The following problems are commonly found in the dynamic simulation of existing propeller-shaft-ship coupled systems: (1) Ignoring the strong coupling effect between the flow field and the structure (such as the influence of flow field pressure on blade vibration) leads to a large deviation between the simulation results and the actual working conditions; (2) The rotational degree of freedom of the shaft system and the propeller is transmitted using simplified constraints (such as fixed constraints), which cannot truly simulate the torque transmission process; (3) Focusing only on the vibration characteristics of a single frequency (such as blade frequency) without analyzing the modulation coupling of shaft frequency to blade frequency makes it difficult to explain the complex vibration phenomena of the system and cannot provide accurate basis for vibration control and structural optimization of propeller-shaft-ship system. Summary of the Invention

[0003] This invention addresses the shortcomings of existing technologies by disclosing a simulation analysis method for propeller-shaft-ship coupled modulation acoustic signals. This invention converts time-domain data into the frequency domain using FFT, focusing on the analysis of shaft frequency, blade frequency, and double blade frequency, quantifying the modulation coupling of shaft frequency to blade frequency, thus filling the gap in frequency coupling analysis in existing simulations.

[0004] This invention provides the following technical solutions: A method for simulating and analyzing propeller-shaft-ship coupled modulated acoustic signals, the method comprising the following steps: Step 1: Establish a full-scale geometric model of the propeller-shaft-ship coupling. Based on the drawings of the propeller-shaft-ship system, construct a full-scale geometric model that includes the flow field, propeller structure, shaft system structure, bearing structure, and deck bulkhead structure. Step 2: Define and assemble the coupled domains. Based on the coupled Eulerian-Lagrange method, the flow field is defined as an Eulerian domain, and the volume behavior of the Eulerian domain is described by the equation of state. The propeller structure, shaft structure, bearing structure and deck bulkhead structure are defined as Lagrange domains, and the Eulerian domain and Lagrange domain are assembled to the preset relative positions. Step 3: Mesh and specify mesh element type. Mesh the component and specify the Eulerian domain mesh as a three-dimensional eight-node Eulerian reduced integral element. Based on the mechanical properties of each structure in the Lagrange domain, select reduced integral elements or full integral elements as the mesh elements of the Lagrange structure. Step 4: Create an explicit dynamics analysis step, set up the explicit dynamics analysis step, and configure the field output request so that the field output results include velocity, acceleration, and Euler volume fraction; Step 5: Define the interaction between the coupled surfaces, set the contact relationship between the surfaces of all Lagrangian domains and the Eulerian domains, and specify the corresponding contact forms; set the contact relationship between the outer surface of the shaft system and the inner surface of the bearing. Step 6: Establish structural connection relationships. Bind the propeller structure to the shaft structure using MPC-beam to transfer rotational degrees of freedom. Connect the shaft structure to the deck base structure by setting two-point springs / dampers, and define the values ​​of spring stiffness and damper damping. Step 7: Apply load and initial conditions. Apply gravity load to the entire simulation model and set the initial angular velocity at the far propeller end of the shaft system to simulate the driving effect of the coupling on the shaft system and realize the rotation of the shaft system and propeller structure. Step 8: Configure the boundary and material distribution of the Eulerian domain. Define the initial material distribution within the Eulerian domain by specifying the Eulerian volume fraction; set the outer surface of the Eulerian domain as the free inflow boundary and the free outflow boundary. Step 9: Vibration signal calculation and data processing. Submit the simulation calculation. After the calculation is completed, extract the velocity-time curve and acceleration-time curve at the connection point between the deck bulkhead and the spring / damper. Convert the vibration velocity time domain data and vibration acceleration time domain data into frequency domain data through fast Fourier transform. Analyze the characteristic values ​​near the shaft frequency, blade frequency and double blade frequency in the frequency domain data to obtain the modulation coupling effect of the shaft frequency on the blade frequency in the vibration signal. Step 10: Establish a simulation analysis model of the acoustic signal of the propeller-shaft-ship coupling. In Virtual.Lab, based on the boundary element method, import the real-scale geometric model and the calculated vibration data, and assign corresponding material properties. Step 11: Map the load, map the vibration data as a load onto the geometric model, and convert the time domain data into frequency domain data through fast Fourier transform; Step 12: Acoustic signal calculation and data processing. Submit the simulation calculation. After the calculation is completed, extract the frequency domain data of the acoustic signal. Analyze the characteristic values ​​near the shaft frequency, blade frequency and double blade frequency in the frequency domain data to obtain the modulation coupling effect of the shaft frequency on the blade frequency in the acoustic signal.

[0005] Preferably, the drawings of the propeller-shaft-ship system in step 1 include the propeller's geometric parameters, number of blades, blade chord length, pitch, shaft diameter and length parameters, deck bulkhead thickness and stiffness parameters, and density and viscosity parameters of the flow field medium.

[0006] Preferably, the state equation us-up in step 2 is expressed by the following formula:

[0007]

[0008] in,p For the flow field pressure in the Eulerian domain, p 0 represents the initial pressure. ρ The density of the flow medium, c 0 is the speed of sound of the material in its undeformed state. η It is the volumetric strain of the material. s This is the fitting coefficient, which is usually set to 0 for approximately incompressible water.

[0009] Preferably, the contact form includes tangential behavior and normal behavior. The tangential behavior is set as a penalty function with a friction coefficient of 0.001. The normal behavior is set as hard contact, allowing separation after contact.

[0010] Preferably, the MPC-beam binding is specifically implemented by establishing an MPC-beam unit between the central section of the propeller hub and the end section of the shaft system near the propeller, constraining the translational degrees of freedom in the X, Y, and Z directions and the rotational degrees of freedom around the X, Y, and Z axes, thereby achieving lossless transmission of torque and rotational motion.

[0011] Preferably, the spring stiffness and damper damping are based on the Sommerfield number. So and bearing length-to-diameter ratio The Sommerfield number is estimated using the following formula:

[0012] in, Oil film viscosity, For rotational speed, For the bearing width, For the bearing diameter, For load, Radial clearance Where is the journal radius; Based on the calculated Sommerfield number So and bearing length-to-diameter ratio The corresponding dimensionless stiffness can be obtained by referring to the dimensionless coefficient curve of the corresponding bearing. and dimensionless damping And convert them into actual spring stiffness and damper damping through the following formulas;

[0013] in, The journal's rotational angular velocity; the spring stiffness ranges from 1e7 to 1e8 N / m, and the damper damping ranges from 1e3 to 1e5 N. s / m.

[0014] Preferably, the initial material distribution within the Eulerian domain is defined as follows: The region occupied by the flow medium within the Eulerian domain is set to have an Eulerian volume fraction of 1, while the air or vacuum region is set to have an Eulerian volume fraction of 0. The transition region between the flow medium and the Lagrange structure surface is set with an Eulerian volume fraction using linear interpolation to simulate the gradual characteristics of the fluid-solid interface.

[0015] A simulation and analysis system for propeller-shaft-ship coupled modulated acoustic signals, the system comprising: Model building module: Used to build a geometric scale model of the propeller-shaft-ship system based on the relevant parameters of the propeller-shaft-ship system, including the flow field, propeller structure, shafting structure and deck bulkhead structure; CEL Field Definition and Assembly Module: Used in Abaqus software to define Eulerian and Lagrange fields based on the CEL method and complete their assembly; Analysis Step Creation Module: Used to create explicit dynamic analysis steps, set the time step to 5e-4s, and configure field output requests including velocity, acceleration, and Euler volume fraction; Interaction definition module: Used to set the contact relationship and contact form between the Lagrange surface and the Eulerian domain; Structural connection module: used to bind the propeller to the shafting via MPC-beam, connect the shafting to the deck bulkhead via springs / dampers, and define the spring stiffness and damping value; Load and Initial Conditions module: Used to apply gravitational loads to the model and set the initial angular velocity at the propeller end of the shaft system; Euler Domain Configuration Module: Used to define the initial material distribution by Euler volume fraction and set the outer surface of the Euler domain as a free inflow / outflow boundary; Mesh specification module: Used to set the Eulerian domain mesh to EC3D8R and specify reduced / fully integrated elements for the Lagrangian structure; The calculation and data processing module is used to submit calculations, extract the velocity / acceleration time-domain curves of the connection points, convert them into frequency-domain data through FFT, and analyze the effects of shaft frequency, blade frequency, double blade frequency, and modulation coupling.

[0016] A computer-readable storage medium having a computer program stored thereon, which is executed by a processor to implement a simulation analysis method for propeller-shaft-ship coupled modulated acoustic signals.

[0017] A computer device includes a memory and a processor, the memory storing a computer program, and the processor executing the computer program to implement a simulation analysis method for propeller-shaft-ship coupled modulation acoustic signals.

[0018] The present invention has the following beneficial effects: The present invention has high coupling accuracy. The present invention achieves strong coupling between the flow field (Eulerian domain) and the structure (Lagrange domain) through the CEL method. The state equation (us-up) accurately describes the volumetric behavior of the flow field, avoiding the errors caused by the simplification of fluid-structure interaction. The motion transmission of this invention is realistic. This invention ensures lossless transmission of rotational degrees of freedom and torque between the propeller and shaft through MPC-beam binding. Springs / dampers simulate the elastic constraints of the shaft system and deck bulkheads, which conforms to the mechanical characteristics of the actual structure. This invention provides comprehensive frequency analysis. It converts time-domain data into frequency-domain data using FFT, focusing on the analysis of shaft frequency, blade frequency, and double blade frequency, quantifying the modulation coupling of shaft frequency to blade frequency, and filling the gap in frequency coupling analysis in existing simulations. The parameters of this invention are highly controllable. This invention clearly defines the value range and determination basis of key parameters such as spring stiffness, damping, and initial angular velocity, which facilitates the adjustment of simulation schemes according to different ship types and propeller types, and has strong versatility. Attached Figure Description

[0019] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 The diagram shown is a simulated structural diagram of the present invention. Figure 2 The diagram shown is a flow field simulation diagram of the present invention. Figure 3 The image shown is a vibration signal diagram calculated by this invention. Figure 4 The image shown is a diagram of the acoustic signal calculated by this invention. Detailed Implementation

[0021] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0022] The present invention will be described in detail below with reference to specific embodiments. Specific Implementation Example 1: according to Figures 1 to 4As shown, the specific optimized technical solution adopted by the present invention to solve the above-mentioned technical problems is: The present invention relates to a simulation analysis method for propeller-shaft-ship coupled modulation acoustic signals.

[0024] This invention provides a method for simulating and analyzing propeller-shaft-ship coupled modulated acoustic signals, the method comprising the following steps: Step 1: Establish a full-scale geometric model of the propeller-shaft-ship coupling. Based on the drawings of the propeller-shaft-ship system, construct a full-scale geometric model that includes the flow field, propeller structure, shaft system structure, bearing structure, and deck bulkhead structure. The drawings for the propeller-shaft-ship system in step 1 include the propeller's geometric parameters, number of blades, blade chord length, pitch, shaft diameter and length parameters, deck bulkhead thickness and stiffness parameters, as well as the density and viscosity parameters of the flow field medium.

[0025] Step 2: Define and assemble the coupled domains. Based on the coupled Eulerian-Lagrange method, the flow field is defined as an Eulerian domain, and the volume behavior of the Eulerian domain is described by the equation of state. The propeller structure, shaft structure, bearing structure and deck bulkhead structure are defined as Lagrange domains, and the Eulerian domain and Lagrange domain are assembled to the preset relative positions. The state equation us-up in step 2 is expressed by the following equation:

[0026]

[0027] in, p For the flow field pressure in the Eulerian domain, p 0 represents the initial pressure. ρ The density of the flow medium, c 0 is the speed of sound of the material in its undeformed state. η It is the volumetric strain of the material. s This is the fitting coefficient, which is usually set to 0 for approximately incompressible water.

[0028] Step 3: Mesh and specify mesh element type. Mesh the component and specify the Eulerian domain mesh as a three-dimensional eight-node Eulerian reduced integral element. Based on the mechanical properties of each structure in the Lagrange domain, select reduced integral elements or full integral elements as the mesh elements of the Lagrange structure. Step 4: Create an explicit dynamics analysis step, set up the explicit dynamics analysis step, and configure the field output request so that the field output results include velocity, acceleration, and Euler volume fraction; Step 5: Define the interaction between the coupled surfaces, set the contact relationship between the surfaces of all Lagrangian domains and the Eulerian domains, and specify the corresponding contact forms; set the contact relationship between the outer surface of the shaft system and the inner surface of the bearing. The contact forms include tangential behavior and normal behavior. Tangential behavior is set as a penalty function with a friction coefficient of 0.001. Normal behavior is set as hard contact, allowing separation after contact.

[0029] Step 6: Establish structural connection relationships. Bind the propeller structure to the shaft structure using MPC-beam to transfer rotational degrees of freedom. Connect the shaft structure to the deck base structure by setting two-point springs / dampers, and define the values ​​of spring stiffness and damper damping. MPC-beam binding specifically involves establishing an MPC-beam unit between the central section of the propeller hub and the end section of the shaft system near the propeller, constraining their translational degrees of freedom in the X, Y, and Z directions and rotational degrees of freedom around the X, Y, and Z axes, thereby achieving lossless transmission of torque and rotational motion.

[0030] Step 7: Apply load and initial conditions. Apply gravity load to the entire simulation model and set the initial angular velocity at the far propeller end of the shaft system to simulate the driving effect of the coupling on the shaft system and realize the rotation of the shaft system and propeller structure. Step 8: Configure the boundary and material distribution of the Eulerian domain. Define the initial material distribution within the Eulerian domain by specifying the Eulerian volume fraction; set the outer surface of the Eulerian domain as the free inflow boundary and the free outflow boundary. Step 9: Vibration signal calculation and data processing. Submit the simulation calculation. After the calculation is completed, extract the velocity-time curve and acceleration-time curve at the connection point between the deck bulkhead and the spring / damper. Convert the vibration velocity time domain data and vibration acceleration time domain data into frequency domain data through fast Fourier transform. Analyze the characteristic values ​​near the shaft frequency, blade frequency and double blade frequency in the frequency domain data to obtain the modulation coupling effect of the shaft frequency on the blade frequency in the vibration signal. The spring stiffness is determined based on the structural stiffness matching between the shaft system and the deck bulkhead, with a value ranging from 1e5 to 1e7 N / m; the "damper damping" is determined based on the flow field damping characteristics and the structural vibration damping characteristics, with a value ranging from 1e3 to 1e5 N. s / m.

[0031] Spring stiffness and damper damping are based on the Sommerfield number. So and bearing length-to-diameter ratio The Sommerfield number is estimated using the following formula:

[0032] in, Oil film viscosity, For rotational speed, For the bearing width, For the bearing diameter, For load, Radial clearance Where is the journal radius; Based on the calculated Sommerfield number So and bearing length-to-diameter ratio The corresponding dimensionless stiffness can be obtained by referring to the dimensionless coefficient curve of the corresponding bearing. and dimensionless damping And convert them into actual spring stiffness and damper damping through the following formulas;

[0033] in, The journal's rotational angular velocity; the spring stiffness ranges from 1e7 to 1e8 N / m, and the damper damping ranges from 1e3 to 1e5 N. s / m.

[0034] Step 10: Establish a simulation analysis model of the acoustic signal of the propeller-shaft-ship coupling. In VirtualLab, based on the boundary element method, import the real-scale geometric model and the calculated vibration data, and assign corresponding material properties. Step 11: Map the load, map the vibration data as a load onto the boundary element model, and convert the time domain data into frequency domain data through fast Fourier transform; Step 12: Acoustic signal calculation and data processing. Submit the simulation calculation. After the calculation is completed, extract the frequency domain data of the acoustic signal. Analyze the characteristic values ​​near the shaft frequency, blade frequency and double blade frequency in the frequency domain data to obtain the modulation coupling effect of the shaft frequency on the blade frequency in the acoustic signal.

[0035] The initial material distribution within the Eulerian domain is defined as follows: The region occupied by the flow medium within the Eulerian domain is set to have an Eulerian volume fraction of 1, while the air or vacuum region is set to have an Eulerian volume fraction of 0. The transition region between the flow medium and the Lagrange structure surface is set with an Eulerian volume fraction using linear interpolation to simulate the gradual characteristics of the fluid-solid interface.

[0036] Figure 3 The seven-bladed propeller speed is controlled at 60 r / min to ensure a shaft frequency of 1 Hz and a blade frequency of 7 Hz. Significant peaks are observed at the following frequencies: 2 times blade frequency ± 3 times shaft frequency (11 Hz and 17 Hz), 4 times blade frequency - 2 times shaft frequency (26 Hz), 5 times blade frequency - 1 times shaft frequency (34 Hz), 7 times blade frequency ± 1 times shaft frequency (48 Hz and 50 Hz), 8 times blade frequency ± 1 times shaft frequency (55 Hz and 57 Hz), and 13 times blade frequency ± 1 times shaft frequency (90 Hz and 92 Hz). This phenomenon reflects the coupling modulation effect of shaft frequency on blade frequency in the vibration signal.

[0037] Figure 4The seven-bladed propeller speed is controlled at 60 r / min, thus ensuring a shaft frequency of 1 Hz and a blade frequency of 7 Hz. Significant peaks are observed at 2 times the blade frequency + 2 times the shaft frequency (16 Hz), 4 times the blade frequency - 1 times the shaft frequency (27 Hz), 8 times the blade frequency ± 1 times the shaft frequency (55 Hz and 57 Hz), and 12 times the blade frequency ± 1 times the shaft frequency (83 Hz and 85 Hz). This phenomenon reflects the coupling modulation effect of the shaft frequency on the blade frequency in the acoustic signal.

[0038] The present invention also provides a simulation and analysis system for propeller-shaft-ship coupled modulation acoustic signals, the system comprising: Model building module: Used to build a geometric scale model of the propeller-shaft-ship system based on the relevant parameters of the propeller-shaft-ship system, including the flow field, propeller structure, shafting structure and deck bulkhead structure; CEL Field Definition and Assembly Module: Used in Abaqus software to define Eulerian and Lagrange fields based on the CEL method and complete their assembly; Analysis Step Creation Module: Used to create explicit dynamic analysis steps, set the time step to 5e-4s, and configure field output requests including velocity, acceleration, and Euler volume fraction; Interaction definition module: Used to set the contact relationship and contact form between the Lagrange surface and the Eulerian domain; Structural connection module: used to bind the propeller to the shafting via MPC-beam, connect the shafting to the deck bulkhead via springs / dampers, and define the spring stiffness and damping value; Load and Initial Conditions module: Used to apply gravitational loads to the model and set the initial angular velocity at the propeller end of the shaft system; Euler Domain Configuration Module: Used to define the initial material distribution by Euler volume fraction and set the outer surface of the Euler domain as a free inflow / outflow boundary; Mesh specification module: Used to set the Eulerian domain mesh to EC3D8R and specify reduced / fully integrated elements for the Lagrangian structure; The calculation and data processing module is used to submit calculations, extract the velocity / acceleration time-domain curves of the connection points, convert them into frequency-domain data through FFT, and analyze the effects of shaft frequency, blade frequency, double blade frequency, and modulation coupling.

[0039] The present invention also provides a computer-readable storage medium having a computer program stored thereon, which is executed by a processor to implement a simulation analysis method for propeller-shaft-ship coupled modulated acoustic signals.

[0040] The present invention also provides a computer device, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement a simulation analysis method for propeller-shaft-ship coupled modulation acoustic signals. Specific Implementation Example 2: The only difference between Embodiment 2 and Embodiment 1 of this application is that: This invention addresses the shortcomings of existing technologies by disclosing a dynamic simulation method for a propeller-shaft-ship coupled system. The invention provides the following technical solution: A dynamic simulation method for a propeller-shaft-ship coupled system, the method comprising the following steps: Step 1: Establish a real-scale geometric model of the propeller-shaft-ship coupling: Based on the relevant drawings of the propeller-shaft-ship system, construct a real-scale geometric model that includes the flow field, propeller structure, shaft system structure, bearing structure and deck bulkheads, etc. Step 2: Define and assemble the coupled domains: In Abaqus software, based on the coupled Eulerian-Lagrange method, the flow field is defined as an Eulerian domain, and the volume behavior of the Eulerian domain is described by the equation of state; the propeller structure, shaft structure, bearing structure and deck bulkhead structure are defined as Lagrange domains, and the Eulerian domain and Lagrange domain are assembled to the preset relative positions; Step 3: Mesh generation and specify mesh element type: Mesh the component and specify the mesh of the Eulerian domain as a three-dimensional eight-node Eulerian reduced integral element (EC3D8R); select reduced integral elements or full integral elements as the mesh elements of the Lagrangian structure according to the mechanical properties of each structure in the Lagrangian domain. Step 4: Create an explicit dynamic analysis step; Set the explicit dynamic analysis step, where the time step is set to 5e-4s to meet the analysis frequency band requirements of vibration signals within 1000Hz, and configure the field output request so that the field output results include velocity, acceleration and Euler volume fraction. Step 5: Define the interaction between coupled surfaces: Set the contact relationship between the surfaces of all Lagrangian domains and the Eulerian domains, and specify the corresponding contact forms; set the contact relationship between the outer surface of the shaft system and the inner surface of the bearing.

[0042] Step 6: Establish structural connection relationships: Bind the propeller structure to the shaft system structure through MPC-beam to transfer rotational degrees of freedom; connect the shaft system structure to the deck base structure by setting two-point springs / dampers, and define the values ​​of spring stiffness and damper damping; Step 7: Apply load and initial conditions: Apply a gravity load to the entire simulation model; set an initial angular velocity at the far propeller end of the shaft system to simulate the driving effect of the coupling on the shaft system and realize the rotation of the shaft system and propeller structure. Step 8: Configure Eulerian domain boundary and material distribution: Define the initial material distribution within the Eulerian domain by specifying the Eulerian volume fraction; set the outer surface of the Eulerian domain as a free inflow boundary and a free outflow boundary; Step 9: Vibration signal calculation and data processing: Submit the simulation calculation. After the calculation is completed, extract the velocity-time curve and acceleration-time curve at the connection point between the deck bulkhead and the spring / damper. Convert the vibration velocity time-domain data and vibration acceleration time-domain data into frequency-domain data through fast Fourier transform. Analyze the characteristic values ​​near the shaft frequency, blade frequency and double blade frequency in the frequency-domain data to obtain the modulation coupling effect of the shaft frequency on the blade frequency in the vibration signal.

[0043] Step 10: Establish a simulation analysis model of the acoustic signal of the propeller-shaft-ship coupling: In Virtual Lab, based on the boundary element method, import the real-scale geometric model and the calculated vibration data, and assign corresponding material properties.

[0044] Step 11: Mapping the load: Map the vibration data as a load onto the boundary element model, and convert the time domain data into frequency domain data through fast Fourier transform.

[0045] Step 12: Acoustic signal calculation and data processing: Submit the simulation calculation, extract the frequency domain data of the acoustic signal after the calculation is completed, analyze the characteristic values ​​near the shaft frequency, blade frequency and double blade frequency in the frequency domain data, and obtain the modulation coupling effect of the shaft frequency on the blade frequency in the acoustic signal.

[0046] The "relevant parameters of the propeller-shaft-ship system" in step 1 include the propeller geometric parameters (number of blades, blade chord length, pitch), shaft diameter and length parameters, deck bulkhead thickness and stiffness parameters, and density and viscosity parameters of the flow field medium; the scaling factor of the geometric scale model is set to 1:5~1:20 according to the computing power and accuracy requirements of the simulation equipment.

[0047] The expression for the "state equation (us-up)" in step 2 is as follows: ,in ,and p For the flow field pressure in the Eulerian domain, p 0 represents the initial pressure. ρ The density of the flow medium, c 0 is the speed of sound of the material in its undeformed state. η It is the volumetric strain of the material. s This is the fitting coefficient, which is usually set to 0 for approximately incompressible water.

[0048] The "Contact Form" setting includes tangential behavior and normal behavior. Tangential behavior is set as a penalty function with a friction coefficient of 0.001; normal behavior is set as hard contact, allowing separation after contact.

[0049] The “MPC-beam binding” specifically refers to establishing an MPC-beam unit between the central section of the propeller hub and the end section of the shaft system near the propeller, constraining the translational degrees of freedom in the X, Y, and Z directions and the rotational degrees of freedom around the X, Y, and Z axes, thereby achieving lossless transmission of torque and rotational motion.

[0050] The "spring stiffness" is determined based on the structural stiffness matching between the shaft system and the deck bulkhead, with a value ranging from 1e5 to 1e7 N / m; the "damper damping" is determined based on the flow field damping characteristics and structural vibration damping characteristics, with a value ranging from 1e3 to 1e5 N. s / m.

[0051] The definition of "initial material distribution within the Eulerian domain" is as follows: the region occupied by the flow medium within the Eulerian domain is set to Eulerian volume fraction = 1, the air or vacuum region is set to Eulerian volume fraction = 0, and the transition region between the flow medium and the Lagrange structure surface is set to Eulerian volume fraction using linear interpolation to simulate the gradual characteristics of the fluid-solid interface.

[0052] The above description is merely a preferred embodiment of a propeller-shaft-ship coupled modulation acoustic signal simulation and analysis method. The scope of protection for this method is not limited to the above embodiments; all technical solutions falling within this framework are within the scope of protection of this invention. It should be noted that for those skilled in the art, any improvements and variations made without departing from the principles of this invention should also be considered within the scope of protection of this invention.

Claims

1. A simulation analysis method for propeller-shaft-ship coupled modulated acoustic signals, characterized by: The method includes the following steps: Step 1: Establish a full-scale analysis model of the propeller-shaft-ship coupled system. Based on the design data of the propeller-shaft-ship coupled system, construct a full-scale analysis model that includes the flow field, propeller structure, shaft system structure, bearing structure and deck bulkhead structure. Step 2: Define and assemble the coupled domains. Based on the coupled Eulerian-Lagrange method, the flow field is defined as an Eulerian domain, and the volume behavior of the Eulerian domain is described by the equation of state. The propeller structure, shaft structure, bearing structure and deck bulkhead structure are defined as Lagrange domains, and the Eulerian domain and Lagrange domain are assembled to the preset relative positions. Step 3: Mesh the system and specify the mesh element type. Mesh the propeller-shaft-ship coupled system and specify the Eulerian domain mesh as a three-dimensional eight-node Eulerian reduced integral element. Based on the mechanical properties of each structure in the Lagrange domain, select reduced integral elements or full integral elements as the mesh elements for the Lagrange structure. Step 4: Create an explicit dynamic analysis step. Set the explicit dynamic analysis step, with a calculation time of no less than 1 second and a time step of no more than 5e-4 seconds, to meet the analysis frequency band requirements of vibration signals within 1000 Hz; and configure the field output so that the field output results include velocity, acceleration, and Euler volume fraction. Step 5: Define the interaction between the coupled surfaces, set the contact relationship between the surfaces of all Lagrangian domains and the Eulerian domains, and specify the corresponding contact forms; set the contact relationship between the outer surface of the shaft system and the inner surface of the bearing. Step 6: Establish structural connection relationships. Bind the propeller structure to the shaft structure using MPC-beam to transfer rotational degrees of freedom. Connect the shaft structure to the bearing structure by setting two-point springs / dampers, and define the values ​​of spring stiffness and damper damping. Step 7: Apply load and initial conditions. Apply gravity load to the entire simulation model and set the initial angular velocity at the far propeller end of the shaft system to simulate the driving effect of the coupling on the shaft system and realize the rotation of the shaft system and propeller structure. Step 8: Configure the boundary and material distribution of the Eulerian domain. Define the initial material distribution within the Eulerian domain by specifying the Eulerian volume fraction; set the outer surface of the Eulerian domain as the free inflow boundary and the free outflow boundary. Step 9: Vibration signal calculation and data processing. Submit the simulation calculation. After the calculation is completed, extract the velocity-time curve and acceleration-time curve at the connection point between the deck bulkhead and the spring / damper. Convert the vibration velocity time-domain data and vibration acceleration time-domain data into frequency-domain data through fast Fourier transform. Analyze the characteristic values ​​near the shaft frequency, blade frequency and double blade frequency in the frequency-domain data to obtain the modulation coupling effect of the shaft frequency on the blade frequency in the vibration signal. Step 10: Establish a simulation analysis model of the acoustic signal of the propeller-shaft-ship coupling. In Virtual.Lab, based on the boundary element method, import the real-scale geometric model and the calculated vibration data, and assign corresponding material properties. Step 11: Map the load. Map the calculated time-domain vibration data as a load onto the boundary element model, and convert the vibration time-domain data into vibration frequency-domain data through fast Fourier transform. Step 12: Acoustic signal calculation and data processing. Submit the simulation calculation. After the calculation is completed, extract the frequency domain data of the acoustic signal. Analyze the characteristic values ​​near the shaft frequency, blade frequency and double blade frequency in the frequency domain data to obtain the modulation coupling effect of the shaft frequency on the blade frequency in the acoustic signal.

2. The method according to claim 1, characterized in that: The design data for the propeller-shaft-ship coupling system in step 1 includes propeller geometric parameters, number of blades, blade chord length, pitch, shaft diameter and length parameters, deck bulkhead thickness and stiffness parameters, as well as density and viscosity parameters of the flow field medium.

3. The method according to claim 2, characterized in that: The state equation us-up in step 2 is expressed by the following equation: in, p For the flow field pressure in the Eulerian domain, p 0 represents the initial pressure. ρ The density of the flow medium, c 0 is the speed of sound of the material in its undeformed state. η It is the volumetric strain of the material. s This is the fitting coefficient, which is usually set to 0 for approximately incompressible water.

4. The method according to claim 3, characterized in that: The contact relationship is set to include tangential behavior and normal behavior. Tangential behavior is set as a penalty function with a friction coefficient of 0.

001. Normal behavior is set as hard contact, allowing separation after contact.

5. The method according to claim 4, characterized in that: MPC-beam binding specifically involves establishing an MPC-beam unit between the central section of the propeller hub and the end section of the shaft system near the propeller, constraining their translational degrees of freedom in the X, Y, and Z directions and rotational degrees of freedom around the X, Y, and Z axes, thereby achieving lossless transmission of torque and rotational motion.

6. The method according to claim 5, characterized in that: Spring stiffness and damper damping are based on the Sommerfield number. So and bearing length-to-diameter ratio The Sommerfield number is estimated using the following formula: in, Oil film viscosity, For rotational speed, For the bearing width, For the bearing diameter, For load, Radial clearance Where is the journal radius; Based on the calculated Sommerfield number So and bearing length-to-diameter ratio The corresponding dimensionless stiffness can be obtained by referring to the dimensionless coefficient curve of the corresponding bearing. and dimensionless damping And convert them into actual spring stiffness and damper damping through the following formulas; in, The journal's rotational angular velocity; the spring stiffness ranges from 1e7 to 1e8 N / m, and the damper damping ranges from 1e3 to 1e5 N. s / m.

7. The method according to claim 6, characterized in that: The initial material distribution within the Eulerian domain is defined as follows: The region occupied by the flow medium within the Eulerian domain is set to have an Eulerian volume fraction of 1, and the air region is set to have an Eulerian volume fraction of 0. The transition region between the flow medium and the Lagrange structure surface is set with an Eulerian volume fraction using linear interpolation to simulate the gradual characteristics of the fluid-solid interface.

8. A simulation and analysis system for propeller-shaft-ship coupled modulation acoustic signals, characterized in that: The system includes: Model building module: Used to build a geometric scale model of the propeller-shaft-ship system based on the relevant parameters of the propeller-shaft-ship system, including the flow field, propeller structure, shafting structure and deck bulkhead structure; Coupled Eulerian-Lagrange Domain Definition and Assembly Module: Used in Abaqus software to define the Eulerian and Lagrange domains based on the CEL method and complete their assembly; Analysis Step Creation Module: Used to create explicit dynamic analysis steps, set the calculation time to be no less than 1 second, the time step to be no more than 5e-4 seconds, and configure field output requests that include velocity, acceleration, and Euler volume fraction; Interaction definition module: Used to set the contact relationship and contact form between the Lagrange surface and the Eulerian domain; Structural connection module: used to bind the propeller to the shafting via MPC-beam, connect the shafting to the deck bulkhead via springs / dampers, and define the spring stiffness and damping value; Load and Initial Conditions module: Used to apply gravitational loads to the model and set the initial angular velocity at the propeller end of the shaft system; Euler Domain Configuration Module: Used to define the initial material distribution by Euler volume fraction and set the outer surface of the Euler domain as a free inflow / outflow boundary; Mesh specification module: Used to set the Eulerian domain mesh to EC3D8R and specify reduced / fully integrated elements for the Lagrangian structure; Calculation and Data Processing Module: Used to submit calculations, extract the velocity / acceleration time-domain curves of the connection points, convert them into frequency-domain data through FFT, and analyze shaft frequency, blade frequency, double blade frequency, and modulation coupling effect.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, The program is executed by the processor to implement the method as claimed in any one of claims 1-7.

10. A computer 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 method of any one of claims 1-7.

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