An underwater vehicle corrosion electric field simulation method based on equivalent electric dipoles

Abstract

The application discloses a kind of based on equivalent electric dipole's underwater vehicle corrosion electric field simulation method, belong to underwater electric field measurement technical field, including the following steps: S1.building multilayer seawater model;S2.building underwater vehicle model, and using finite element software COMSOL simulates the corrosion electric field of underwater vehicle, calculates the corrosion simulation electric field intensity at each sampling point;S3.place in seawater layer N Electric dipole, according to current source electric type dyadic Green function, the corrosion simulation electric field intensity of sampling point is used to obtain the electric dipole moment of the electric dipole at the position by inversion, the position and electric dipole moment of the electric dipole are iteratively calculated by combining fitness function, and the optimal position and electric dipole moment of the electric dipole are output.The application provides theoretical support and optimization method for underwater vehicle corrosion electric field analysis and target detection in marine environment.

Description

Technical Field

[0001] This invention relates to a method for simulating the corrosion electric field of underwater vehicles based on equivalent electric dipoles, belonging to the field of underwater electric field measurement technology. Background Technology

[0002] Underwater vehicles are prone to generating corrosion currents and anti-corrosion currents in seawater due to electrochemical corrosion and anti-corrosion measures. These currents create a corrosion electric field in the seawater. This corrosion electric field is an important physical field that poses a serious threat to the electric field stealth performance and safety of underwater vehicles. Specifically, for example... Figure 1 As shown, the steel hull (anode) and copper alloy propeller (cathode) of an underwater vehicle form a macroscopic galvanic corrosion cell in seawater electrolyte. The hull, acting as the anode, undergoes a metal dissolution reaction, while the propeller, acting as the cathode, undergoes an oxygen reduction reaction. This process forms a corrosion current loop with a constant direction: the current flows from the steel hull through the seawater medium to the propeller, and then returns to the hull via the propeller shaft, forming a closed path. In addition, the protective current generated by the corrosion protection system returns to the system through the propeller shaft or the hull, forming another closed loop. Both loops generate corresponding corrosion electric fields. In the above scenario, the charge separation characteristics of the anode and cathode are equivalent to the positive and negative charge pairs of an electric dipole.

[0003] Numerical simulation methods for the corrosion electric field distribution of underwater vehicles have been studied by many researchers, including equivalent electric dipole simulation methods and numerical simulation methods such as the finite element method. The inversion method mainly includes the Tikhonov regularization method. This invention aims to provide a novel method for simulating the corrosion electric field of underwater vehicles. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a method for simulating the corrosion electric field of underwater vehicles based on an equivalent electric dipole. The consistency between the inversion results and the simulation results of the corrosion electric field of underwater vehicles demonstrates that it is feasible to replace the corrosion electric field of underwater vehicles with the equivalent electric dipole electric field.

[0005] The present invention achieves the above objectives by adopting the following technical solutions:

[0006] A method for simulating the corrosion electric field of underwater vehicles based on equivalent electric dipoles includes the following steps:

[0007] S1. Construct a multi-layered seawater model;

[0008] S2. Construct an underwater vehicle model and use the finite element software COMSOL to simulate the corrosion electric field of the underwater vehicle, and calculate the corrosion simulation electric field intensity at each sampling point;

[0009] S3. Place in the seawater layer NThe electric dipole moment of the electric dipole at the position is obtained by inversion according to the current source electric dyadic Green function and by using the corrosion simulation electric field intensity of the sampling points, and the position and the electric dipole moment of the electric dipole are iteratively calculated by combining the fitness function, and the optimal position and the electric dipole moment of the electric dipole are output.

[0010] Further, the step S1 is specifically:

[0011] S1.1.1, an xyz coordinate system is established, so that x the axis and y the axis are parallel to the sea surface, z the positive direction of the axis is perpendicular to the sea surface and points to the sea bottom;

[0012] S1.1.2, the air layer above the seawater is numbered as 0, the seawater is divided into n layers along the Z-axis direction, and the interface between the air layer and the first layer of seawater is located at z 0=0 m; the relative permittivity and conductivity of each layer are , ( l =0,1,…,n).

[0013] Further, the step S2 is specifically:

[0014] S2.1, a simulation model of the underwater vehicle is constructed;

[0015] S2.2, the simulation model is imported into COMSOL Multiphysics to simulate the corrosion electric field caused by the macro galvanic corrosion and the corrosion protection system of the ship body;

[0016] S2.3, a plurality of sampling points are taken above and below the underwater vehicle, and the corrosion simulation electric field intensity M at each sampling point is simulated and calculated. E

[0017] Further, the step S2.1 is specifically: the coordinate origin is set at the center of the ship body, the ship body includes a cylindrical main body, a surrounding shell is arranged at the top of the ship body, the base of the propeller is composed of a cylinder and a hemisphere shell, propeller blades are arranged on the base, the propeller shaft connecting the base and the ship body is a cylinder, the bow is a hemisphere shell, and two auxiliary anodes are arranged at the stern to simulate the impressed current cathodic protection system.

[0018] Further, in the step S2.2, the simulation method of the corrosion electric field caused by the macro galvanic corrosion is: the current distribution in the seawater and the corrosion reaction on the surface of the simulation model are simulated by using the “cathodic protection” module, the material of the ship body is set in the “material” option, and the surfaces of the propeller and the propeller shaft are set as electrode surfaces in the “boundary condition” option, and the electrode reaction occurring on the surfaces of the propeller and the propeller shaft is set as the oxygen reduction process.

[0019] ​The simulation method of the corrosion electric field caused by the corrosion protection system is: adding a "reference electrode" potential in the "model" option, setting the potential of the auxiliary anode relative to the potential of the reference electrode, and using the potential to simulate the cathodic protection system.

[0020] Further, step S3 is specifically:

[0021] S3.1 placing an electric dipole at any position in the seawater layer in any direction N based on the size of the ship body shape, limiting the distribution range of the electric dipole in a rotating ellipsoid; wherein, I is the current of the electric dipole, each electric dipole is divided into multiple segments, each segment is Δl, I Δ l is the current element;

[0022] S3.2 using the current source electric type dyadic Green function to simulate the electric field intensity generated by the electric dipole at the field point is:

[0023] (1)

[0024] S3.3 according to the electric dipole moment of the electric dipole and formula (1), obtains:

[0025] (2)

[0026] E corresponding M to the simulation electric field intensity of the sampling point, is a 3 M ×1 order matrix; P corresponding N to the electric dipole moment of the electric dipole, is a 3 N ×1 order matrix; G is a 3 M ×3 N order matrix;

[0027] S3.4 each electric dipole obtains a matrix G according to the current position, and the simulation electric field intensity E at the position is known, and the electric dipole moment P is solved by using the least square method according to formula (2), and the solution is represented as:

[0028] (3)

[0029] wherein, is the generalized inverse matrix of G ;

[0030] S3.5 updating the position and electric dipole moment of the electric dipole according to the fitness function to solve the optimal position and electric dipole moment of the electric dipole.

[0031] Further, step S3.5 is specifically:

[0032] S3.5.1 giving the initial position of each electric dipole , initial velocity , initial individual optimal solution , ;

[0033] Each electric dipole obtains a coefficient matrix G according to the current position, and the electric dipole moment corresponding to the current position of the electric dipole is calculated by using formula (3) P , the fitting electric field intensity is calculated according to the product of the coefficient matrix G and the electric dipole moment P ;

[0034] The fitness value is calculated by using the fitness function, and the position of the electric dipole with the minimum fitness value is taken as the initial global optimal solution , wherein the fitness function is the relative error between the corrosion simulation electric field intensity and the fitting electric field intensity, that is:

[0035] (4)

[0036] S3.5.2 updating the velocity and position of the electric dipole, and calculating the fitness value by using formula (4) after each updating is completed ;

[0037] S3.5.3 comparing and , if < , then ; otherwise, the previous value is still retained, and the updating of the individual optimal solution is completed in this way;

[0038] The individual optimal solution with the minimum fitness value is selected from all electric dipoles, and is taken as the global optimal solution of this updating ;

[0039] After the updating is completed, the next round of iteration is implemented until the maximum number of iterations is reached, and the position of the electric dipole and the electric dipole moment are output.

[0040] Further, in step S3.5.2, the velocity updating formula of the electric dipole is:

[0041] (5)

[0042] In the formula, is the first k iteration of the electric dipole i the first dThe velocity of the flight; For the first k The first i The first d The first a 1, a 2 is a learning factor, b 1, b 2 is a random number in the interval [0, 1]; , For the first k The first d The individual optimal solution and the global optimal solution of the first The inertia weight is;

[0043] The position updating formula of the electric dipole is:

[0044] (6)

[0045] In the formula, For the first k The first i The first d The first

[0046] The beneficial effects of the present application include but are not limited to:

[0047] The underwater vehicle corrosion electric field simulation method based on equivalent electric dipole provided by the present application,

[0048] The present application obtains the corrosion electric field distribution of the underwater vehicle based on COMSOL simulation, uses the dyadic Green function of the layered medium to simulate the corrosion electric field generated by the equivalent direct current power supply, and combines the dyadic Green function with the iterative updating algorithm to obtain the position and strength of the equivalent electric dipole by inversion, thereby providing theoretical support and optimization method for underwater vehicle corrosion electric field analysis and target detection in marine environment.

[0049] It is found through calculation that with the increase of the number of equivalent electric dipoles, the inversion result of the corrosion electric field is more and more accurate. The consistency of the inversion result and the simulation result of the underwater vehicle corrosion electric field shows that it is feasible to replace the underwater vehicle corrosion electric field with the equivalent electric dipole electric field. BRIEF DESCRIPTION OF DRAWINGS

[0050] The drawings described herein are used to provide further understanding of the present application, and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application, and do not constitute an improper limitation on the present application. In the drawings:

[0051] Figure 1 The schematic diagram of the corrosion current and the anticorrosion current is shown in Figure 1;

[0052] Figure 2 Figure 1 is a multi-layer seawater model diagram;

[0053] Figure 3 Figure 2 is a simulation model diagram of an underwater vehicle;

[0054] Figure 4 Figure 3 is a comparison diagram of electric fields of electric dipoles obtained by three algorithms;

[0055] Figure 5 Figure 4 is a comparison diagram of electric fields generated by equivalent electric dipoles on a sampling line 1 and simulation electric fields;

[0056] Figure 6 Figure 5 is a diagram of electric field distribution generated by 10 equivalent electric dipoles on a 40 m profile; y

[0057] Figure 7 Figure 6 is a diagram of corrosion electric field distribution simulated by COMSOL on a 40 m profile. y DETAILED DESCRIPTION

[0058] The present application will be further described in the following. It should be noted that the following detailed description of the present application is only given by way of example to illustrate specific operation examples of the present application, but the protection scope of the present application is not limited thereto. The protection scope of the present application is only defined by the claims. It is obvious to those skilled in the art that various other modifications and replacements of the embodiments described in the present application can be made within the protection scope defined by the claims of the present application, and the same technical effects can still be achieved, and the final technical purpose of the present application can be achieved.

[0059] The underwater vehicle corrosion electric field simulation method based on equivalent electric dipoles provided by the present application comprises the following steps:

[0060] S1. constructing a multi-layer seawater model;

[0061] Further, as shown in the specification, step S1 is specifically: Figure 2

[0062] S1.1.1 establishing an xyz coordinate system, so that the x-axis and the y-axis are parallel to the sea surface, and the z-axis points to the sea bottom in the positive direction; x y z

[0063] S1.1.2 considering the actual marine environment, constructing a multi-layer seawater model to calculate the corrosion electric field of the equivalent electric dipole. The air layer above the seawater is numbered as layer 0, and the seawater is divided into n layers along the z-axis direction. The interface between the air layer and the first layer of seawater is located at 0=0 m; the relative dielectric constant and the electrical conductivity of each layer are respectively z ​​​​​​​, ( l =0,1,…,n); the first n Below the seawater layer is a sedimentary layer.

[0064] S2. Construct an underwater vehicle model and use the finite element software COMSOL to simulate the corrosion electric field of the underwater vehicle, and calculate the corrosion simulation electric field intensity at each sampling point;

[0065] Furthermore, step S2 specifically includes:

[0066] S2.1 as Figure 3 As shown in the figure, an underwater vehicle simulation model is constructed;

[0067] Furthermore, step S2.1 specifically includes:

[0068] The origin of the coordinate system is set at the center of the hull. The hull consists of a cylindrical main body, a conning tower at the top of the hull, a propeller base consisting of a cylinder and a hemispherical shell, a propeller blade on the base, a propeller shaft connecting the base and the hull that is cylindrical, a hemispherical shell at the bow, and two auxiliary anodes at the stern to simulate an impressed current cathodic protection system.

[0069] S2.2 Import the simulation model into COMSOL Multiphysics to simulate the corrosion electric field caused by macroscopic galvanic corrosion and the anti-corrosion system on the ship hull;

[0070] Furthermore, in step S2.2, the simulation method for the corrosion electric field caused by macroscopic galvanic corrosion is as follows: the current distribution in seawater electrolyte and the corrosion reaction on the simulation model surface are simulated using the "cathode protection" module. The material of the hull is set in the "material" option, and the surfaces of the propeller and propeller shaft are set as electrode surfaces in the "boundary conditions" option. The electrode reaction occurring on the two surfaces is set as the oxygen reduction process.

[0071] The method for simulating the corrosion electric field caused by the anti-corrosion system is as follows: add a "reference electrode" potential in the "Model" option, and set the potential of the auxiliary anode relative to the potential of the reference electrode to simulate the cathodic protection system.

[0072] S2.3 Take samples above and below the underwater vehicle. M The corrosion simulation electric field intensity was calculated at each sampling point. E Typically, along the top and bottom of the underwater vehicle... y Several sampling lines are laid out in different directions, such as Figure 2 As shown, sampling points are taken on each sampling line, and the three-component electric field is obtained by COMSOL simulation.

[0073] S3. In the inversion of the corrosion electric field of underwater vehicles, the optimization of the equivalent electric dipole array model simplifies to an optimization problem of the electric dipole position and electric dipole moment. Therefore, placing [the model] in the seawater layer... N For each electric dipole, the electric dipole moment at its location is obtained by inverting the electric field intensity of the corrosion simulation at the sampling point using the current source electric type dyadic Green's function. The position and electric dipole moment of the electric dipole are then iteratively calculated using the fitness function to output the optimal position and electric dipole moment of the electric dipole.

[0074] Furthermore, step S3 specifically includes:

[0075] S3.1 Placed at any location in the seawater layer in any direction. N A number of electric dipoles are distributed within a rotating ellipsoid based on the shape and dimensions of the ship's hull; among them... I Let be the current in the electric dipole, and divide each electric dipole into multiple segments, each segment being Δl. I Δ l It is a current element;

[0076] S3.2 uses a current source type dyadic Green's function. The electric field strength generated by the simulated electric dipole at the field point is:

[0077] (1)

[0078] The current source type dyadic Green's function is expressed in the following form:

[0079]

[0080] In the formula, , , Let x, y, and z represent the components of the electric field intensity produced by a unit electric dipole in the x-direction in the x, y, and z directions, respectively. , , Let x, y, and z represent the components of the electric field intensity produced by a unit electric dipole in the y direction in the x, y, and z directions, respectively. , , These represent the components of the electric field intensity produced by a unit electric dipole in the z direction in the x, y, and z directions, respectively. The Green's function is determined by the position of the electric dipole and is calculated according to existing formulas.

[0081] S3.3 Based on the electric dipole moment of the electric dipole and equation (1), we obtain:

[0082] (2)

[0083] E corresponding M to the three-component data of the simulated electric field intensity of the sampling point, which is a 3 M ×1 order matrix; P corresponding N to the three-component data of the electric dipole moment of the electric dipole, which is a 3 N ×1 order matrix; G is a 3 M ×3 N order matrix;

[0084] S3.4 Each electric dipole obtains a matrix according to the current position G , and the simulated electric field intensity at the position is known E ; since the number of sampling points M is much larger than the number of electric dipoles N , the electric dipole moment is solved according to the known simulated electric field intensity, which is solving an over-determined equation; therefore, the electric dipole moment is solved according to formula (2) by using the least square method P , and the solution is expressed as:

[0085] (3)

[0086] wherein, is the generalized inverse matrix of G ;

[0087] S3.5 The position and electric dipole moment of the electric dipole are iteratively updated according to the fitness function, so as to solve the optimal position and electric dipole moment of the electric dipole.

[0088] Further, step S3.5 is specifically:

[0089] S3.5.1 The initial position , initial velocity , and initial individual optimal solution of each electric dipole are given ;

[0090] Each electric dipole obtains a coefficient matrix G according to the current position, and the electric dipole moment corresponding to the current position of the electric dipole is solved and calculated by using formula (3) P , and the fitting electric field intensity is calculated according to the product of the coefficient matrix G and the electric dipole moment P . In this step, the electric dipole moment P is solved according to the least square method, so there will be errors between G·P and E , and the error needs to be reduced by updating iteration in the next step.

[0091] Therefore, the fitness value is calculated using a fitness function, and the position of the electric dipole with the smallest fitness value is selected as the initial global optimum. The fitness function is the relative error between the simulated electric field strength and the fitted electric field strength, i.e.:

[0092] (4)

[0093] S3.5.2 Update the velocity and position of the electric dipole. After each update, calculate the fitness value using equation (4). ;

[0094] Furthermore, in step S3.5.2, the velocity update formula for the electric dipole is:

[0095] (5)

[0096] In the formula, For the first k Electric dipole during the next iteration i The d Dimensional flight speed; For the first k -1st iteration electric dipole i The d Dimensional position; a 1. a 2 is the learning factor, and we take... a 1= a 2≈2; b 1. b 2 is a random number in the interval [0,1]. , For the first k The electric dipole at the -1st iteration d The individual optimal solution and the global optimal solution at a specific position; The inertial weight can be a fixed value or dynamically adjusted (e.g., linearly decreasing within a certain upper and lower limit range). This invention uses... , K The maximum number of iterations is 800. In this invention, the total number of electric dipoles is 100, and the maximum number of iterations is 800.

[0097] The position update formula for an electric dipole is:

[0098] (6)

[0099] In the formula, For the first k Electric dipole during the next iteration i The d Dimensional position.

[0100] S3.5.3 Comparison With , if , then ; otherwise, the previous value is still retained, and the update of the individual optimal solution is completed in this way;

[0101] The individual optimal solution with the minimum fitness value is selected from all electric dipoles, and is taken as the global optimal solution of this update ;

[0102] After the update is completed, the next round of iteration is implemented until the maximum number of iterations is reached, and the position and electric dipole moment of the electric dipole are output.

[0103] The update iteration method adopted by the present application is to find the optimal solution through the cooperation and information sharing between individuals in the population. D In the target search space with I dimensions, the total number of populations is D each particle in the population has a position vector and a velocity vector, which represent the search state in the solution space, wherein the position vector represents the current position solution, and the velocity vector represents the direction and speed of the particle movement in the search process, and each particle has a memory function and can remember the best position searched. N The relationship between the dimension of the target search space and D =3 N At each step of the algorithm implementation, each particle searches and obtains an individual optimal solution ( i =1,2,…, I ; d =1,2,…, D ) in the space, and shares the individual optimal solution with other particles in the population, and obtains the current global optimal solution of the entire particle group from the individual optimal solutions of all particles. Each particle in the particle group constantly changes its position and speed according to the current individual optimal solution and global optimal solution, updates the individual optimal solution and global optimal solution, until the maximum number of iterations is reached or the best position is converged.

[0104] The underwater vehicle corrosion electric field simulation method based on the equivalent electric dipole provided by the present application will be further described below through specific embodiments.

[0105] Embodiment 1:

[0106] In order to verify the correctness of the calculation results of the dyadic Green function and COMSOL simulation, the electric field generated by a direct current electric dipole in an infinite deep sea is calculated in this embodiment, and the calculation results are compared with those of the traditional mirror method.

[0107] ​When using the dyadic Green's function for simulation calculations, the value is taken as... The extremely low frequencies of Hz are treated as equivalent to DC. The model used is a two-layer dielectric model, with the first layer being air and its conductivity being... =0, the second medium is infinitely deep seawater, its conductivity is 0. =4S·m -1 .along x An electric dipole placed along its axis is located at a water depth of 150m, with coordinates (0, 0, 150). The magnitude of the electric dipole moment is... p = I Δ l =100A·m.

[0108] Figure 4 Given y =0m、 z =225m along x Two non-zero components of the electric field intensity in the axial direction within the range of -200m to 200m E x and E z Field point position coordinates x The changing relationship.

[0109] Depend on Figure 4 It can be seen that the calculation results of the dyadic Green's function, COMSOL, and mirror method are completely consistent, demonstrating the correctness of both the dyadic Green's function and COMSOL algorithms. Figure 4 From a, we can know that E x Relative to the field point position coordinates x =0 is symmetrical about left and right, in x Its amplitude reaches its maximum value at =0. (From...) Figure 4 b indicates that E z Relative to the field point position coordinates x =0 is antisymmetric, in x At point =0, its amplitude is 0. As the field point moves further away, E x and E z All are close to 0.

[0110] Example 2:

[0111] (2.1) Model Construction:

[0112] In this example, the corrosion electric field of the underwater vehicle is simulated by the finite element software COMSOL as the measured value to be inverted. The length of the ship body is 50 m, the main body of the ship is cylindrical, and the diameter is 6 m. The surrounding shell is 3.5 m higher than the top of the ship body, the length is 10 m, the thickness is 2 m, and the center of the surrounding shell is located at x =3 m. The propeller base is composed of a cylinder with a length of 1.1 m and a radius of 0.4 m and a hemisphere shell with a radius of 0.4 m, and there are 4 propeller blades on the base. The propeller shaft connecting the base and the ship body is a cylinder with a radius and a length of 0.2 m. The bow part is a hemisphere shell with a radius of 3 m, and two auxiliary anodes are arranged at the tail of the submarine x =-17 m, which is used to simulate the impressed current cathodic protection system.

[0113] The above model is imported into COMSOL Multiphysics, and the "cathodic protection" module is used to simulate the current distribution in the electrolyte and the corrosion reaction on the metal surface. In the "material" option, the propeller is made of nickel aluminum bronze (NAB) alloy, and the propeller shaft is made of 625 alloy. In the "boundary condition" option, the surface of the propeller and the propeller shaft is set as the electrode surface, and the electrode reaction occurring on the surface of the two is set as the oxygen reduction process. In the oxygen reduction process, the limiting current density of the electrode kinetics expression is selected as 5 A·m -2 . In the "model" option, a "reference electrode" node (potential of 0 V) is added, and then the electrode potential of the auxiliary anode relative to the potential of the reference electrode is set to -850 mV, which is used to simulate the cathodic protection system. All the boundaries of the remaining part of the underwater vehicle surface use the default "insulation" condition. To simulate the infinite extension of the sea, the "infinite electrolyte" condition is used for the outer boundary of the electrolyte domain.

[0114] In the simulation, the seawater is uniform and the effects of air layer and deposition layer are ignored, and the conductivity of seawater is taken as 4 S·m -1 . Two sampling lines are arranged above and below the underwater vehicle along the y direction, and the three-component electric field obtained by COMSOL simulation on each sampling line is used as the training set, and the number of sampling points on each sampling line is 41. The position of sampling line 1 is x =-10 m, z =23 m, the position of sampling line 2 is x =-10 m, z =-17 m, the position of sampling line 3 is x =10 m, z =-17 m, and the position of sampling line 4 is x =10 m, z =23 m, and the positions of the sampling lines are yThe sampling range of the direction is -100m-100m.

[0115] (2.2) Inversion of corrosion electric field:

[0116] In the inversion of corrosion electric field of underwater vehicle, the distribution range of electric dipole is limited in a rotating ellipsoid with half long axis of 25m and half short axis of 3m based on the size of the hull. Assuming the number of equivalent electric dipoles is 1, 5 and 10 respectively, according to the three-component corrosion electric field data simulated by COMSOL on the above-mentioned 4 sampling lines, the position and electric dipole moment of equivalent electric dipoles in three cases are shown in Table 1, Table 2 and Table 3 respectively by using dyadic Green function method and particle swarm optimization algorithm. Comparing Table 1-Table 3 can be seen that with the increase of the number, the distribution of equivalent electric dipoles is closer to the size and position of underwater vehicle.

[0117]

[0118]

[0119]

[0120] Figure 5 The comparison of three components of corrosion electric field on sampling line 1 calculated by dyadic Green function under three electric dipole number conditions and the original simulation data is given.

[0121] It can be seen that, Figure 5 E x and E z are symmetrical relative to the plane of y =0, and the amplitude value reaches the maximum at y =0, E y is anti-symmetrical relative to the plane of y =0, and y E y =0 at Figure 5 It can be seen that the electric field generated by multiple electric dipoles obtained by inversion based on simulation electric field is consistent with the overall trend of simulation electric field. When the number of equivalent electric dipoles increases to 10, the corrosion electric field generated by electric dipoles is highly consistent with the simulation electric field curve, and the relative error of the maximum amplitude E x is 2.0%, E y is 1.6%, E z ​​The relative error is 0.2%. It can be seen that with the increase of the number of equivalent electric dipoles, the inversion result of the corrosion electric field is more and more accurate. When the number of equivalent electric dipoles increases to a certain number, the relative error will not be obviously improved.

[0122] Figure 6 The distribution of the electric field generated by 10 equivalent electric dipoles calculated by the dyadic Green function is given for the profile of y =40m, Figure 7 The distribution of the corrosion electric field of the underwater vehicle simulated by COMSOL is given for the same profile. Figure 6 Compared with Figure 7 , the distribution of the electric field generated by 10 equivalent electric dipoles is consistent with the actual distribution of the corrosion electric field of the underwater vehicle, which further illustrates the accuracy of the inversion result and the feasibility of replacing the corrosion electric field of the underwater vehicle with the electric field of the equivalent electric dipole.

[0123] The above specific embodiments cannot be regarded as a limitation on the protection scope of the present application, and any alternative improvement or transformation made by the person skilled in the art to the embodiments of the present application falls within the protection scope of the present application.

[0124] The details not described in the present application are the known technology of the person skilled in the art.

Claims

1. An underwater vehicle corrosion electric field simulation method based on equivalent electric dipoles, characterized in that, The method comprises the following steps: S1. Constructing a multi-layer seawater model; S2. Constructing an underwater vehicle model, and simulating the corrosion electric field of the underwater vehicle by using a finite element software COMSOL to calculate the corrosion simulation electric field intensity at each sampling point; S3. Place an electric dipole in the seawater layer N An electric dipole is placed in the seawater layer, the electric dipole moment of the electric dipole is obtained by inversion according to the electric current source electric type dyadic Green function and the simulated electric field intensity of the sampling point, the position and the electric dipole moment of the electric dipole are iteratively calculated by combining the fitness function, and the optimal position and the electric dipole moment of the electric dipole are output. Step S3 is specifically: S3.1 at any position in the seawater layer placed in any direction N electric dipoles, the distribution range of the electric dipoles is limited in a rotating ellipsoid based on the shape and size of the ship body; wherein, I is the electric current of the electric dipole, each electric dipole is divided into multiple segments, each segment is Δl, I Δ l is the current element; S3.2 Current source formulation of dyadic Green's functions The electric field strength produced by an electric dipole at a field point is given by (1) S3.3 Electric dipole moment of the electric dipole and formula (1) gives: (2) E corresponding M to the simulated electric field strength of the sampling point, is a 3 M x 1 matrix; P corresponding N to the electric dipole moment of the electric dipole, is a 3 N x 1 matrix; G is a 3 M x 3 N matrix; S3.4 Each electric dipole obtains a matrix according to the current position G , knowing the simulated electric field intensity at that place E , the electric dipole moment is solved using the least squares method according to equation (2) P whose solution is expressed as: (3) wherein is G the generalized inverse matrix of S3.

5. Iteratively updating the position and electric dipole moment of the electric dipole according to the fitness function, to solve the optimal position and electric dipole moment of the electric dipole.

2. The equivalent electric dipole-based corrosion electric field modeling method for an underwater vehicle of claim 1, wherein, Step S1 is specifically: S1.1.1 Establish an xyz coordinate system such that x the x-axis is parallel to the sea surface, y the y-axis is parallel to the sea surface, z the z-axis points in the positive direction perpendicular to the sea surface towards the sea bottom; S1.1.2 The air layer above the seawater, the layer number is 0, the seawater is divided into n layers along the Z-axis direction, the interface between the air layer and the first layer of seawater is located at 0 = 0 m; the relative permittivity and conductivity of each layer are z , , ( l = 0, 1, …, n).

3. The equivalent electric dipole-based corrosion electric field modeling method for an underwater vehicle of claim 1, wherein, Step S2 is specifically: S2.

1. Constructing an underwater vehicle simulation model; S2.

2. Importing the simulation model into COMSOL Multiphysics to simulate the corrosion electric field caused by macro galvanic corrosion and the corrosion protection system of the ship body; S2.3 Taking sampling points above and below the underwater vehicle, simulating the corrosion simulation electric field intensity at each sampling point M E .​ 4. The equivalent electric dipole-based corrosion electric field modeling method for an underwater vehicle of claim 3, wherein, In step S2.2, the simulation method of the corrosion electric field caused by the macro galvanic corrosion is: the "cathodic protection" module is used to simulate the current distribution in seawater and the corrosion reaction on the surface of the simulation model, the material of the ship body is set in the "material" option, and the surfaces of the propeller and the propeller shaft are set as electrode surfaces in the "boundary condition" option, and the electrode reactions occurring on the surfaces of the propeller and the propeller shaft are set as oxygen reduction processes; The simulation method of the corrosion electric field caused by the corrosion protection system is: a "reference electrode" potential is added in the "model" option, the potential of the auxiliary anode is set relative to the potential of the reference electrode, and the potential of the auxiliary anode is used to simulate the cathodic protection system.

5. The equivalent electric dipole-based corrosion electric field modeling method for an underwater vehicle of claim 1, wherein, Step S3.5 is specifically: S3.5.1 Given the initial position of each electric dipole , initial velocity , initial individual best solution ; Each electric dipole gets a coefficient matrix G according to the current position, and the electric dipole moment corresponding to the current position of the electric dipole is calculated by using formula (3) P , the fitting electric field intensity is calculated according to the product of the coefficient matrix G and the electric dipole moment P ; The fitness value is calculated by using the fitness function, and the electric dipole position with the minimum fitness value is taken as the initial global optimal solution Wherein the fitness function is the relative error of the corrosion simulation electric field intensity and the fitting electric field intensity, that is: (4) S3.5.2 Update the velocity and position of the electric dipole, and calculate the fitness value after each update using equation (4) ; S3.5.3 comparison with , if then ;​ Otherwise, The previous value is still reserved, and the update of the individual optimal solution is completed in this way. The individual optimal solution with the minimum fitness value in all electric dipoles is selected as the global optimal solution of this time update ; After the updating is completed, the next round of iteration is implemented until the maximum number of iterations is reached, and the position and electric dipole moment of the electric dipole are output.

6. The equivalent electric dipole-based corrosion electric field modeling method for an underwater vehicle of claim 5, wherein, In step S3.5.2, the speed updating formula of the electric dipole is: (5) wherein is the k th iteration of the electric dipole i is the d th iteration of the velocity in the th dimension; k is the i th iteration of the position in the d th dimension; a 1, a 2 are learning factors, b 1, b 2 are random numbers in the interval [0, 1]; , is the k th iteration of the position in the d th dimension of the electric dipole is the inertia weight; The position updating formula of the electric dipole is: (6) wherein is the k th iteration of the i th iteration of the d th iteration of the

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