Numerical calculation method of double-explosion-source underwater explosion impact cavitation load

Abstract

The invention provides a numerical calculation method for double-explosion-source underwater explosion impact cavitation loads, and belongs to the technical field of computer data processing-based explosion impact wave calculation, and the method comprises the following steps: solving a propagation process of far-field underwater double-explosion-source explosion impact waves in a two-dimensional acoustic flow field by using a local discontinuous Galerkin (LDG) method; and the cavitation characteristics of the flow field under the action of the double-explosion-source underwater explosion shock waves are researched. A flow field dynamic pressure result calculated by the method is compared with a result calculated by an acoustic finite element method. The result shows that the flow field dynamic pressure result calculated by the method is well matched with the calculation result data of the acoustic finite element method, and the effectiveness and the accuracy of the method are verified.

Description

Technical Field

[0001] The present invention belongs to the technical field of explosion shock wave calculation based on computer data processing, and particularly relates to a numerical calculation method for double-explosion-source underwater explosion shock cavitation load. Background Art

[0002] Existing research on underwater explosion shock waves, especially numerical simulation research, mostly focuses on single-explosion-source scenarios. However, in actual engineering applications, multi-explosion-source underwater explosions are also very common, such as the series detonation of naval mines and the coordinated attack of multiple ammunitions. The shock waves generated by multi-explosion-source explosions will have a coupling superposition effect, and the propagation characteristics and cavitation effects of the load are significantly different from those of single-explosion-source explosions. The existing technology has not studied the propagation law and cavitation characteristics of multi-explosion-source underwater explosion shock waves deeply and systematically enough. In terms of the interaction between double-explosion sources, the shock wave coupling effect, and the resulting complex cavitation phenomenon, the existing technology is difficult to provide accurate and reliable numerical simulation results. Summary of the Invention

[0003] Aiming at the above problems, the present invention aims to overcome the lack of in-depth research on the propagation and cavitation characteristics of double-explosion-source underwater explosion shock waves in the existing technology, and lacks an in-depth understanding and accurate simulation method. Especially in terms of the interaction between double-explosion sources, the shock wave coupling effect, and the resulting complex cavitation phenomenon, the existing technology is difficult to provide accurate and reliable numerical simulation results. The present invention aims to solve how to provide a numerical calculation method that can accurately simulate the propagation and cavitation characteristics of double-explosion-source underwater explosion shock waves, filling the gap in the research of double-explosion-source scenarios in the existing technology.

[0004] The present invention provides a numerical calculation method for double-explosion-source underwater explosion shock cavitation load, including the following processes: Step 1, based on the working conditions of double-explosion-source underwater explosion shock cavitation load, establish a flow field model by setting the flow field range and its size parameters, and discretize the flow field model into grid cells to obtain relevant information of the discrete element flow field; Step 2, calculate the distance between the explosive source point and the explosion point based on the relevant information of the discrete element flow field, the position of the explosive placement, and the explosion point position of the flow field; Step 3, set the position of the incident wave loading surface of the flow field, and calculate the distance between any point on the incident wave loading surface of the flow field and the explosive source point; Step 4, calculate the gradient of the dynamic pressure at any point x j on the incident wave loading surface of the flow field in the space direction ; Step 5: Based on the results of Steps 1 to 4, characterize the boundary conditions at the incident wave loading surface of the double-explosion source in the computational domain, and construct a numerical model for the propagation of the underwater explosion shock wave of the double-explosion source in the acoustic flow field; Step 6: Based on the discrete element flow field phase information in Step 1 and the control equation for the propagation of the underwater explosion shock wave of the double-explosion source in the discrete element acoustic flow field, calculate the numerical flux at the boundary of the discrete element flow field to obtain the dynamic pressure result of the discrete element flow field; Step 7: Introduce a pressure truncation model to handle the cavitation effect, identify the region where the absolute pressure of the flow field is lower than the cavitation limit, and obtain the position result of the cavitation region in the flow field; Step 8: After calculating the physical quantities of all elements in the discrete element flow field at the initial moment based on the above process, calculate the physical quantities of all elements in the discrete element flow field at the next moment. By continuously looping this step in the time domain, finally obtain the calculation results of the dynamic pressure and total pressure of all discrete elements in the flow field at all calculation time steps.

[0005] Preferably, the relevant information of the discrete element flow field in Step 1 is obtained by a program to read the node numbers, coordinate positions, and node information of each element in the flow field model.

[0006] Preferably, the specific calculation method of Step 2 is as follows: ; In the formula, represents the vector position coordinate of the th explosive source point, represents the vector position coordinate of the th explosive detonation point, R 0i represents the distance between the i th explosive source point and detonation point.

[0007] Preferably, the specific calculation method of Step 3 is as follows: ; In the formula, x ji represents the vector position coordinate of the point on the incident wave loading surface of the i th explosive, represents the vector position coordinate of the th explosive source point, R ji represents the distance between any point on the incident wave loading surface corresponding to the i th explosive and the explosive source point.

[0008] Preferably, Step 4 is specifically as follows: The calculation formula for any point x j on the incident wave loading surface of the underwater explosion incident wave in the discrete element flow field is: ; In the formula, is the delay time, , c is the propagation speed of the shock wave in the flow field, , is the fluid bulk modulus, is the fluid density; is the load amplitude value of the explosive at the detonation point; represents the spatial variation of the pressure field load at any point x j on the incident wave loading surface; The incident wave loading surfaces of the two explosives are the same plane. Using the wave superposition principle, the pressure gradients of the two explosives on the incident wave loading surface are coupled and superimposed to calculate the spatial gradient of the dynamic pressure at any point x j on the incident wave loading surface of the discrete element flow field .

[0009] Preferably, the control equation for the propagation of the underwater explosion shock wave of the double explosion sources in the discrete element acoustic flow field in step 5 is: ; In the formula, is the element in the discrete element flow field e , is the boundary of the element e in the discrete element flow field; ; ; ; where represents the basis function describing the spatial physical quantity in the element, N is the total number of basis functions in an element; j is the index of the basis function, used to identify the j th basis function in the basis function matrix; represents the value of the corresponding physical quantity at the j th basis function of the element; p is the dynamic pressure in the flow field; x and y represent the directions of the two-dimensional Cartesian coordinate system of the flow field; represents the partial derivative of the fluid dynamic pressure with respect to time; represents the second-order partial derivative of the fluid dynamic pressure with respect to time; represents the partial derivative of the fluid dynamic pressure with respect to x direction; represents the partial derivative of the fluid dynamic pressure with respect to y direction; and is the numerical flux of the terms in F and G at the cell boundaries in the matrix; , where , and are test functions; represents the test function with respect to x direction partial derivative; represents the test function with respect to y direction partial derivative.

[0010] Preferably, in step 6, the numerical flux at the boundary of the discrete cell flow field is calculated, and the numerical flux solution expressions under different boundary conditions are as follows: ; ; ; In the formula, + represents the physical quantity located on the cell K , and – represents the physical quantity of another cell adjacent to the edge K of the cell e ; is the unit outer normal vector of the cell boundary, represents the dynamic pressure at the edge K of the cell e , represents the time derivative of the fluid dynamic pressure at the non-reflecting boundary cell; , where is the length of the edge e .

[0011] Preferably, in step 7, the position where the cavitation region appears in the flow field is calculated specifically as follows: ; ; ; In the formula, p is the dynamic pressure in the flow field, is the quasi-dynamic pressure, is the displacement of the fluid particle, is the absolute pressure at the flow field calculation point, is the atmospheric pressure, is the fluid density, is the gravitational acceleration, is the water depth at the calculation point, is the cavitation limit, and the cavitation limit is set to 0, indicating that the fluid cannot transmit negative pressure.

[0012] Preferably, in step 8, the fourth-order Runge-Kutta method is used to calculate the physical quantities of all cells in the discrete element flow field at the next moment. By continuously looping this step in the time domain, the calculation results of the dynamic pressure and total pressure of all discrete elements in the flow field at all calculation time steps are finally obtained, realizing the simulation of the evolution of the propagation characteristics and cavitation characteristics of the underwater explosion shock wave of a double explosion source in the acoustic flow field.

[0013] Compared with the prior art, the present invention has the following beneficial effects: The core inventive point of the present invention is to propose a numerical calculation method for the underwater explosion shock cavitation load of a double explosion source based on the local discontinuous Galerkin (LDG) method and apply it to the underwater double explosion source explosion scenario, effectively solving the deficiencies existing in the prior art in related fields.

[0014] 1. The present invention innovatively introduces the LDG method into the numerical simulation study of the underwater explosion shock wave of a double explosion source. By coupling the pressure gradient at the incident wave loading surface of the double explosion source, an accurate characterization of the superposition effect of the underwater explosion shock load of the double explosion source is achieved. This method effectively simulates the spatial distribution characteristics, dynamic interaction mechanism and non-linear attenuation law of the underwater explosion shock load of the double explosion source, and for the first time reveals the influence mechanism of the double explosion source shock wave on the cavitation characteristics of the flow field, overcoming the key technical bottlenecks such as large numerical dissipation and insufficient accuracy existing in the traditional finite element method in shock wave propagation simulation.

[0015] 2. For the underwater double explosion source explosion scenario, the present invention can systematically analyze the influence laws of key parameters such as the explosion distance, mass ratio and initiation time between the two explosives on the cavitation characteristics of the flow field, reveal the interaction process between shock waves and the evolution process of cavitation phenomena under different parameter combinations, and provide important theoretical guidance and design basis for the engineering application of underwater explosion. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following description is only one embodiment of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0017] Figure 1 is the overall calculation process flow chart of the present invention.

[0018] Figure 2 is a schematic diagram of the calculation model of the underwater explosion shock cavitation load of the double explosion source of the present invention.

[0019] Figure 3 is a comparison chart of the results of the LDG method and the acoustic finite element method.

[0020] Figure 4It is a schematic diagram of the propagation of the underwater explosion shock wave of a double explosion source in a flow field.

[0021] Figure 5 It is a schematic diagram of the evolution of the cavitation characteristics of the flow field under the action of the underwater explosion shock wave of a double explosion source. Specific implementation manners

[0022] The present invention proposes a numerical calculation method for the propagation and cavitation characteristics of the underwater explosion shock wave of a double explosion source. This method uses the local discontinuous Galerkin (LDG) method to solve the propagation process of the underwater double explosion source explosion shock wave in a two-dimensional acoustic flow field in the far field, and then studies the cavitation characteristics of the flow field under the action of the underwater explosion shock wave of the double explosion source. The dynamic pressure results of the flow field calculated by using this method are compared with the calculation results of the acoustic finite element method. The results show that the dynamic pressure results of the flow field calculated by this method are in good agreement with the calculation results of the acoustic finite element method, verifying the effectiveness and accuracy of this method.

[0023] Next, the specific implementation manners and the technical difficulties and inventive points of the present invention will be further introduced in combination with the design examples of the present invention.

[0024] The specific implementation steps of the present invention are as follows.

[0025] Step 1: Based on the research conditions of the underwater explosion shock cavitation load of the double explosion source, by setting the flow field range and its size parameters, a flow field calculation model is established, and the node and element information is obtained by discretization. Then, the program reads the relevant information of the discretized flow field model. This provides basic data for further calculations based on the discretized flow field; First, the position and size of the flow field are established in the finite element software, and the entire flow field model is discretized into triangular meshes by using the finite element software. Each triangular mesh forms an element. The discretized flow field file is exported, and the program reads the exported discretized flow field file. The program mainly reads the numbers and coordinate positions of each node and the node composition of each element, and uses to represent the discretized triangular element flow field.

[0026] Step 2: Based on the relevant information of the discretized element flow field obtained in Step 1. Refer to Figure 2 , set the positions of the explosives and the explosion points in the flow field, and calculate the distance between the explosive source point and the explosion point: (1) In the formula, represents the vector position coordinate of the th explosive source point, represents the vector position coordinate of the th explosive explosion point, R 0i represents the distance between the i th explosive source point and the explosion point.

[0027] Step 3: Based on the discrete element flow field related information in Step 1 and the positions of the explosives placed in Step 2, combine Figure 2 , set the position of the incident wave loading surface of the flow field, and calculate the distance between any point on the incident wave loading surface of the flow field and the explosive source point: (2) In the formula, x ji represents the vector position coordinate of the point of the i th explosive on the incident wave loading surface, represents the vector position coordinate of the th explosive source point, R ji represents the distance between any point on the incident wave loading surface corresponding to the i th explosive and the explosive source point.

[0028] Step 4: Based on the discrete element flow field related information in Step 1, the distance between the explosive source point and the detonation point in Step 2, and the distance between any point on the incident wave loading surface of the flow field and the explosive source point in Step 3, calculate the gradient j of the dynamic pressure in the spatial direction at any point x on the incident wave loading surface of the flow field; For far - field underwater explosion, the explosion source is located outside the flow field. When the explosion source detonates, the generated shock wave load is applied on the incident wave boundary of the flow field, so as to simulate the propagation process of the underwater explosion shock wave in the flow field. The calculation formula for the underwater explosion incident wave at any point x j on the discrete element flow field incident wave loading surface is: (3) In the formula, is the delay time, , c is the propagation speed of the shock wave in the flow field, , is the fluid bulk modulus, is the fluid density. is the load amplitude value of the explosive at the detonation point. represents the spatial variation of the pressure field load at any point x j on the incident wave loading surface; For the shock wave generated by the explosive in underwater explosion, the present invention adopts the Geers - Hunter model to describe the attenuation characteristics of the cylindrical wave of the underwater explosion shock wave in the flow field. Combine Figure 2 , and calculate the time - load data p t1 and p t2After the calculation is completed, the time-load data at the explosion point p t1 and p t2 are imported into the program. The program reads the time-load data of the explosive explosion at the explosion point in the discrete element flow field p t1 and p t2 . In the present invention, the incident wave loading surfaces of the two explosives are the same plane. Using the wave superposition principle, the pressure gradients of the two explosives on the incident wave loading surface are coupled and superimposed to calculate the spatial gradient of the dynamic pressure at any point x j on the incident wave loading surface of the discrete element flow field : (4) (5) In the formula ṗ ti represents the derivative of the time-load data of the i th explosive with respect to time, and g p ti represents the spatial gradient of the dynamic pressure of the shock wave generated by the explosion of the Ni th explosive on the incident wave loading surface. i

[0029] Step 5: Based on the relevant information of the discrete element flow field in Step 1, the distance between the explosive source point and the explosion point in Step 2, the distance between any point on the incident wave loading surface of the flow field and the explosive source point in Step 3, and the result of the spatial gradient of the dynamic pressure at any point x j on the incident wave loading surface in Step 4, characterize the boundary conditions at the incident wave loading surface of the double-explosion source in the calculation domain, and then construct a numerical model for the propagation of the underwater explosion shock wave of the double-explosion source in the acoustic flow field to study the propagation law of the underwater explosion shock wave in the flow field; The fluid disturbed by the underwater explosion shock wave can be regarded as an inviscid, compressible, and adiabatic fluid. The propagation of the underwater explosion shock wave in the fluid satisfies the second-order wave equation, and the calculation formula of the second-order wave equation in the discrete element flow field Ω is: (6) In the formula, p is the dynamic pressure of the fluid, Δ represents the Laplace operator, represents the second-order derivative of the dynamic pressure of the fluid with respect to time; The flow field is established in the two-dimensional Cartesian coordinate system to study the propagation characteristics of the underwater explosion shock wave in the two-dimensional flow domain. In the Cartesian coordinate system, the calculation formula (6) can be written as: (7) (8) (9) In the formula, represents the symbol of derivative operation, represents the partial derivative of the hydrodynamic pressure with respect to x direction, represents the partial derivative of the hydrodynamic pressure with respect to y direction, represents the second-order partial derivative of the hydrodynamic pressure with respect to x direction, represents the second-order partial derivative of the hydrodynamic pressure with respect to y direction; The LDG method semi-discrete format is adopted to solve the propagation of the underwater explosion shock wave load of a double explosion source in a two-dimensional acoustic flow field. Both ends of the calculation equation are multiplied by the test functions , and , and integrated in the discrete element. The control equation for the propagation of the underwater explosion shock wave of a double explosion source in the discrete element acoustic flow field is: (10) In the formula, is the element e in the discrete element flow field, is the boundary of the element e in the discrete element flow field; U is the matrix composed of the second-order partial derivative of the dynamic pressure in the flow field with respect to time and the partial derivatives of the dynamic pressure in the flow field with respect to the flow field space directions x , y ; ; ; ; Among them represents the basis function describing the spatial physical quantity in the element, N is the total number of basis functions in an element; j is the index of the basis function, used to identify the j th basis function in the basis function matrix; represents the value of the corresponding physical quantity at the j th basis function of the element; p is the dynamic pressure in the flow field; x and y represent the directions of the two-dimensional Cartesian coordinate system of the flow field; represents the partial derivative of the hydrodynamic pressure with respect to time; represents the second-order partial derivative of the hydrodynamic pressure with respect to time. and are the numerical fluxes of each item in F and G on the element boundary. , where , and are test functions. denotes the test function with respect to x direction partial derivative; denotes the test function with respect to y direction partial derivative.

[0030] Step 6. Based on the discrete element flow field related information in Step 1 and the control equation for the propagation of the double-explosion-source underwater explosion shock wave in the discrete element acoustic flow field in Step 5, calculate the numerical flux at the boundary of the discrete element flow field. The expressions for solving the numerical flux under different boundary conditions are as follows: (11) (12) (13) In the formula, + represents the physical quantity located on the element K , and – represents the physical quantity of another element adjacent to the side K of the element e . is the unit outer normal vector of the element boundary, represents the dynamic pressure at the side K of the element e , represents the time derivative of the fluid dynamic pressure at the non-reflecting boundary element. , where is the length of the side e ; is the gradient of the dynamic pressure on the incident wave loading surface with respect to the spatial direction.

[0031] Step 7. Based on the various calculations completed in Steps 1-6, obtain the dynamic pressure result of the discrete element flow field, introduce a pressure truncation model to handle the cavitation effect, and determine the location where the cavitation region appears in the flow field, specifically: (14) (15) (16) In the formula, p is the dynamic pressure in the flow field, is the pseudo-dynamic pressure, is the displacement of the fluid particle, is the absolute pressure at the flow field calculation point, is the atmospheric pressure, is the fluid density, is the gravitational acceleration, is the water depth at the calculation point, is the cavitation limit, and the cavitation limit is set to 0, indicating that the fluid cannot transmit negative pressure.

[0032] Step 8: Based on the data obtained from the relevant calculations and processing completed in Steps 2 - 7, the physical quantities of all units in the discrete element flow field at the initial moment can be obtained. The fourth-order Runge-Kutta method is used to calculate the physical quantities of all units in the discrete element flow field at the next moment. By continuously looping this step in the time domain, the calculation results of the dynamic pressure and total pressure of all discrete elements in the flow field at all calculation time steps are finally obtained, thereby realizing the evolution simulation of the propagation characteristics and cavitation characteristics of the underwater explosion shock wave of a double explosion source in the acoustic flow field.

[0033] Introduce auxiliary variables , , and , formula (10) can be expressed as: (17) Combined with the initial conditions , ; Use the fourth-order Runge-Kutta method to solve the physical quantities at the next time step, and the calculation expression is: (18) (19) (20) (21) (22) where Δ t is the time step increment; is the fluid dynamic pressure at t m moment and the first derivative of the fluid dynamic pressure with respect to time; , , , respectively represent the fluid dynamic pressure calculated under different moments and different conditions and the first derivative of the fluid dynamic pressure with respect to time; is the t m value of and at is the calculation of when the calculated and values, is the calculation of when the calculated and value calculated for when calculating and value; is t m +Δ t the hydrodynamic pressure at time and the first derivative of the hydrodynamic pressure with respect to time.

[0034] The method of the present invention can accurately simulate the propagation characteristics, interaction mechanism and coupling effect of shock waves during the underwater explosion of a double explosion source, and can effectively simulate the resulting complex cavitation phenomenon, providing a more reliable numerical tool for deeply understanding the mechanism of underwater explosion of a double explosion source and evaluating its damage effect. The present invention can more accurately simulate the propagation process of shock waves generated by the explosion of a double explosion source, effectively suppress the numerical oscillation of the pressure curve, and improve the accuracy and credibility of the simulation of shock wave propagation. In addition, the method of the present invention can be used to systematically study the effects of parameters such as the detonation distance, mass ratio between the two explosives, and the detonation time of the two explosives on the cavitation characteristics of the flow field, reveal the evolution law and intensity of cavitation phenomena under different parameter combinations, and provide a theoretical basis and design reference for underwater explosion engineering applications, such as underwater weapon design and optimization of underwater blasting operations.

[0035] To verify the effectiveness of the LDG method of the present invention in simulating the propagation and cavitation characteristics of shock waves in underwater explosion of a double explosion source, the results of the calculation method adopted by the present invention are compared with the results of the acoustic finite element method. The dynamic pressure at a point on the central axis of the two explosives in the flow field is selected for comparison. As Figure 3 shown, the results show that the dynamic pressure results of the calculation method adopted by the present invention are in good agreement with the results of the acoustic finite element method. Compared with the traditional acoustic finite element method, the LDG method of the present invention effectively suppresses the numerical oscillation of the pressure curve and obtains a smoother shock wave pressure time history curve. This characteristic indicates that the LDG method of the present invention can more truly reflect the physical essence during the propagation process of shock waves in underwater explosion of a double explosion source, providing reliable technical support for the numerical simulation of shock wave problems in underwater explosion of a double explosion source.

[0036] Figure 4 shows the propagation process of shock waves generated by two 0.5 kg TNT explosives in a 45 m × 16 m two-dimensional computational domain simulated using the calculation method of the present invention. When t = 1.2 ms, the shock waves generated by the explosion of the two explosives enter the flow field. When t = 7.76 ms, the shock waves generated by the explosion of the two explosives continue to propagate further in the flow field. When t = 11.28 ms, the shock waves generated by the two explosives contact the free surface of the flow field and generate rarefaction waves. When tWhen t = 17.68, the generated rarefaction wave propagates in the flow field in the direction opposite to the shock wave.

[0037] Figure 5 Shows the evolution characteristics of the cavitation region (red region) in the flow field during the propagation of the shock wave of two 0.5 kg TNT explosives simulated using the calculation method of the present invention in a 45 m × 16 m two-dimensional calculation domain.

[0038] Figure 4 and Figure 5 Shows the propagation process (unit: Pa) of the shock wave and the evolution characteristics of the cavitation region (red region) at different times when two 0.5 kg TNT explosives are simulated using the calculation method of the present invention in a 45 m × 16 m two-dimensional calculation domain. This fully demonstrates the ability of the present invention to accurately simulate the interaction, attenuation law, and flow field cavitation characteristics of the underwater explosion shock wave of a double explosion source.

[0039] The above are only the preferred embodiments of the present application and are not used to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

[0040] Although the specific implementation manners of the present invention are described above, it is not a limitation to the protection scope of the present invention. Those skilled in the art should understand that based on the technical solutions of the present invention, various modifications or deformations that can be made without creative labor by those skilled in the art are still within the protection scope of the present invention.

Claims

1. A numerical calculation method for cavitation load of double-explosion source underwater explosion, characterized in that: The process includes: Step 1: Based on the double-explosion source underwater explosion impact cavitation load condition, a flow field model is established by setting the flow field range and its size parameters, and the flow field model is discretized into grid units to obtain discrete unit flow field related information; Step 2, based on the discrete unit flow field related information, the location of the explosive placement and the location of the flow field explosion point, calculate the distance between the explosive source point and the explosion point; Step 3, setting the position of the flow field incident wave loading surface, and calculating the distance between any point on the flow field incident wave loading surface and the explosive source point; Step 4: Calculate the x value of any point on the incident wave loading surface of the flow field based on the information of the discrete unit flow field, the distance between the explosive source point and the explosion point, and the distance between any point on the incident wave loading surface of the flow field and the explosive source point. j The gradient of the dynamic pressure at ; Step 5, based on the results of steps 1 to 4, characterize the boundary conditions at the incident wave loading surface of the double explosion source in the calculation domain, and construct a numerical model of the propagation of the double explosion source underwater explosion shock wave in the acoustic flow field; Step 6, based on the discrete unit flow field phase information of step 1, the numerical flux at the boundary of the discrete unit flow field is calculated using the control equation of the propagation of the double-explosion source underwater explosion shock wave in the discrete unit acoustic flow field to obtain the numerical flux at the boundary of the discrete unit flow field; Step 7, introducing a pressure cutoff model to process the cavitation effect, identifying the area where the absolute pressure of the flow field is lower than the cavitation limit, and obtaining the location result of the cavitation area in the flow field; Step 8, after all the unit physical quantities of the discrete unit flow field at the initial moment are calculated based on the above process, all the unit physical quantities of the discrete unit flow field at the next moment are calculated; by continuously repeating this step in the time domain, the dynamic pressure and total pressure calculation results of all discrete units in the flow field at all calculation time steps are finally obtained.

2. The numerical calculation method of the cavitation load of the double-explosion source underwater explosion according to claim 1 is characterized by: The discrete unit flow field related information in step 1 is obtained by reading the node numbers, coordinate positions and node information of each unit in the flow field model through a program.

3. The numerical calculation method of the cavitation load of the double-explosion source underwater explosion according to claim 1 is characterized by: The specific calculation method of step 2 is: In the formula, Indicates The vector position coordinates of the explosive source points, Indicates The vector position coordinates of the explosion point of the explosive, R 0i Indicates i The distance between the source of the explosive and the explosion point.

4. The numerical calculation method of the cavitation load of the double-explosion source underwater explosion according to claim 1 is characterized by: The specific calculation method of step 3 is: In the formula, x ji Indicates i The vector position coordinates of the explosive point on the incident wave loading surface, Indicates The vector position coordinates of the explosive source points, R ji Indicates i The distance between any point on the incident wave loading surface corresponding to an explosive and the explosive source point.

5. The numerical calculation method of the cavitation load of the double-explosion source underwater explosion according to claim 1 is characterized by: The step 4 is specifically as follows: Underwater explosion incident wave at any point x on the incident wave loading surface of the discrete unit flow field j The calculation formula is: In the formula, is the delay time, , c is the propagation speed of the shock wave in the flow field, , is the bulk modulus of the fluid, is the fluid density; is the load amplitude value of the explosive at the explosion point; represents any point x on the incident wave loading surface j Spatial variation of pressure field load at; The incident wave loading surfaces of the two explosives are on the same plane. The pressure gradients of the two explosives on the incident wave loading surface are coupled and superimposed by using the wave superposition principle to calculate the discrete unit flow field at any point x on the incident wave loading surface. j The spatial gradient of dynamic pressure .

6. The numerical calculation method of the cavitation load of the double-explosion source underwater explosion according to claim 1 is characterized by: The control equation for the propagation of the shock wave of the double-explosion source underwater explosion in the discrete unit acoustic flow field in step 5 is: In the formula, is the unit in the discrete unit flow field e , is the unit in the discrete unit flow field e the boundaries of; in represents the basis functions describing the spatial physical quantities in the unit, N is the total number of basis functions in a unit; j is the index of the basis function, used to identify the first j basis functions; Indicates that the corresponding physical quantity is in the unit j The value of the basis function; p is the dynamic pressure in the flow field; x and y Represents the direction of the two-dimensional Cartesian coordinate system of the flow field; represents the partial derivative of the fluid dynamic pressure with respect to time; It represents the second-order partial derivative of the fluid dynamic pressure with respect to time; The dynamic pressure of the fluid x Direction partial derivative; The dynamic pressure of the fluid y Direction partial derivative; and is the numerical flux of each item in the matrix F and G on the unit boundary; ,in , and is the test function; Represents the test function right x Direction partial derivative; Represents the test function right y Direction partial derivative.

7. The numerical calculation method of the cavitation load of the double-explosion source underwater explosion according to claim 6 is characterized by: In step 6, the numerical flux at the boundary of the discrete unit flow field is calculated, and the numerical flux solution expression under different boundary conditions is as follows: Where + represents the unit K Physical quantity on, – represents the unit K Edge e The physical quantity of another adjacent unit; is the unit external normal vector to the cell boundary, Representation unit K Edge e The dynamic pressure at represents the time derivative of the fluid dynamic pressure at the non-reflecting boundary unit; ,in It is the edge e Length.

8. The numerical calculation method of the cavitation load of the double-explosion source underwater explosion according to claim 6 is characterized by: The calculation of the position of the cavitation area in the flow field in step 7 is specifically as follows: In the formula, p is the dynamic pressure in the flow field, is the pseudo-dynamic pressure, is the displacement of the fluid particles, is the absolute pressure at the flow field calculation point, is the atmospheric pressure, is the fluid density, is the acceleration due to gravity, is the water depth at the calculation point, is the cavitation limit. When the cavitation limit is set to 0, it means that the fluid cannot transmit negative pressure.

9. The numerical calculation method of the cavitation load of the double-explosion source underwater explosion according to claim 1 is characterized by: The step 8 is to use the fourth-order Runge-Kutta method to calculate all unit physical quantities of the discrete unit flow field at the next moment.

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