A method for assessing ship gas explosion damage based on a gas-solid coupling model

Abstract

This invention provides a method for assessing ship gas explosion damage based on a gas-solid coupling model. The method includes: constructing a numerical solution model for a gas explosion based on computational fluid dynamics theory to calculate the pressure exerted by the gas explosion on the ship hull; calculating the reflected pressure on the hull to assess the damage to the ship structure from the gas explosion; and constructing a numerical solution model for ship damage assessment based on peri-field dynamics methods to evaluate the damage caused to the hull by the gas explosion. This invention utilizes compressible fluid dynamics theory to accurately simulate the hydrodynamic behavior of a gas explosion and combines it with peri-field dynamics methods to simulate the dynamic response of the ship structure. In the scenario of a ship gas explosion, it can quickly and accurately assess the damage to the ship structure under the impact of the explosion. Combined with relevant test data and the calculation results of this model, it provides strong support for ship safety design and accident prevention.

Description

Technical Field

[0001] This invention relates to the field of ship gas explosion damage assessment technology, and more particularly to a ship gas explosion damage assessment method based on a gas-solid coupling model. Background Technology

[0002] Damage assessment for ship gas explosions is crucial for ship safety design and accident prevention. During navigation or anchoring, ships may experience gas explosions due to leaks or external explosions, leading to severe structural damage and safety incidents. In particular, gases emitted from diesel fuel, due to their flammable and explosive properties, can cause explosions in the ship's environment, posing a serious threat to the ship's structure and the safety of personnel.

[0003] Ship gas explosions involve complex gas-solid coupling effects, and the dynamic effects of the blast shock wave on the ship structure require accurate simulation. The dynamic interaction between the high-pressure gas generated by the explosion and the ship structure needs precise simulation, while post-explosion damage assessment requires rapid and accurate results to support emergency response and repair decisions. Furthermore, real-world explosion scenarios may involve multiple explosion sources, irregular explosion shapes, and other complex situations, requiring flexible simulation and assessment. Because ship gas explosions are a complex multiphysics problem involving the dynamic interaction between the gas explosion impact and the ship structure, this gas-solid coupling effect makes the damage assessment of ship structures highly complex. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method for assessing ship gas explosion damage based on a gas-solid coupling model. By coupling a gas explosion model with a ship structural model using near-field dynamics methods, this invention can accurately simulate the dynamic effects of gas explosions on ship structures and rapidly assess the damage to the ship structure.

[0005] The technical means employed in this invention are as follows:

[0006] A method for assessing ship gas explosion damage based on a gas-solid coupling model, comprising:

[0007] S1. Based on computational fluid dynamics theory, a numerical solution model for gas explosion is constructed to calculate the pressure of gas explosion on the ship hull;

[0008] S2. To assess the damage to the ship's structure caused by the gas explosion, calculate the reflected pressure on the hull.

[0009] S3. Based on the near-field dynamics method, construct a numerical solution model for ship damage assessment to evaluate the damage caused to the ship hull by gas explosion.

[0010] Furthermore, step S1 specifically includes:

[0011] S11. Obtain input parameters, including the density, volume fraction, specific internal energy, and specific heat ratio of the gas within a preset range, and discretize the explosion region into a finite element mesh based on the finite volume method.

[0012] S12. Calculate the initial explosion pressure of the explosion point grid by solving the conservation equations and combining them with the state equations.

[0013] S13. Using flux calculation methods, evaluate the flux at the interface between the explosion point grid and adjacent grids to update the conserved variables and obtain the flow field state at the next time step.

[0014] S14. Calculate the pressure of adjacent grids using the state equation based on the updated conserved variables;

[0015] S15. Through gradual iteration of the time step, the process of gas explosion pressure being transmitted to the ship hull is finally simulated.

[0016] Further, step S12 specifically includes:

[0017] S121. Calculate the density ρ0 of the gas mixture z using the following formula:

[0018] ρ0=α1ρ1+α2ρ2

[0019] Where ρ1 represents the density of diesel vapor x; ρ2 represents the density of air y;

[0020] S122. Calculate the specific internal energy e0 of the gas mixture z. The calculation formula is as follows:

[0021]

[0022] Where e1 represents the specific internal energy of diesel vapor x, and e2 represents the specific internal energy of air y;

[0023] S123. Based on the calculated density ρ0 and specific internal energy e0 of the mixed gas z, and according to computational fluid dynamics theory, calculate the pressure generated by the mixture of diesel vapor x and air y at the initial explosion time t0 in the explosion point grid. The calculation formula is as follows:

[0024]

[0025] Where p0 represents the pressure generated by the explosion of the gas mixture z; α1 represents the volume fraction of diesel vapor x; α2 represents the volume fraction of air y; for a gas mixture consisting only of these two gases, α1 + α2 = 1; ξ1 represents the parameter related to diesel vapor x; ξ2 represents the parameter related to air y. Γ iThe Grüneisen parameter represents the i-th phase; Π1 and Π2 represent functions related to the state equations;

[0026] S124. Calculate the specific heat ratio γ0 of the gas mixture z. The calculation formula is as follows:

[0027]

[0028] Among them, c p1 c represents the isobaric specific heat capacity of diesel volatile gas x; p2 c represents the specific heat capacity of air at constant pressure. v1 c represents the specific heat capacity at constant volume of diesel volatile gas x; v2 This represents the specific heat capacity of air at constant volume (y).

[0029] S125. Treating diesel vapor x, air y, and mixed gas z as ideal gases, according to the ideal gas law in computational fluid dynamics, for an ideal gas Γ... i =γ i Π i =0, calculate the pressure generated by the gas mixture z at the initial explosion moment. The calculation formula is as follows:

[0030] p0=(γ0-1)ρ0e0.

[0031] Further, step S13 specifically includes:

[0032] S131. Calculate the wave velocity S of the exploded mesh. own The calculation formula is as follows:

[0033]

[0034] Where, N own =u own *n own , representing the normal velocity component of the exploded mesh, u own n represents the mixing velocity of the gas within the explosion grid. own Represents the surface normal vector of the exploded mesh; p represents the speed of sound in the exploding grid. own γ represents the pressure of the gas within the explosion grid. own ρ represents the specific heat ratio of the gas within the explosion grid. own Indicates the density of the gas within the explosion grid; This represents the normal weighted average velocity component between two exploded grids. This represents the weighted average sound velocity across the exploded grid.

[0035] S132. Calculate the wave velocity S of adjacent grids. nei The calculation formula is as follows:

[0036]

[0037] Where, N nei =u nei *n nei , representing the normal velocity component of adjacent grids, u nei n represents the mixing rate of gases within adjacent grid cells. nei Represents the surface normal vector of adjacent meshes; p represents the speed of sound in adjacent grids. nei γ represents the pressure of the gas within adjacent grid cells. nei ρ represents the specific heat ratio of gases in adjacent grids. nei This indicates the density of gas within adjacent grid cells; This represents the normal weighted average velocity component between two adjacent grid cells. This represents the weighted average sound velocity between adjacent grid cells;

[0038] S133. Using the HLL method, calculate the flux between the exploded grid and adjacent grids. The calculation formula is as follows:

[0039]

[0040] Among them, S own S represents the wave velocity of the exploding mesh; nei F represents the wave velocity of adjacent grids; own F represents the flux of the exploded grid. nei U represents the flux between adjacent grid cells; own U represents the conserved quantity of the exploded mesh; nei Represents the conserved quantity between adjacent grids;

[0041] S134. Calculate the conserved quantity U between the exploded mesh and adjacent meshes at the current time step. The calculation formula is as follows:

[0042]

[0043] Where ρ represents the mixing density of the gas in the current time step explosion grid and the adjacent grid; E represents the total energy of the gas in the current time step explosion grid and the adjacent grid.

[0044] S135. Calculate the flux F between the exploded grid and adjacent grids at the current time step. The calculation formula is as follows:

[0045]

[0046] Where I represents the identity matrix between the current time step's exploded grid and its adjacent grids;

[0047] S136. Flux is used to update conserved quantities. Based on the first-order Euler time integral method in computational fluid dynamics theory, the conserved quantity U for the next time step is calculated. n+1 The calculation formula is as follows:

[0048]

[0049] Among them, U n Δt represents the conserved quantity at the current time step; Δt represents the time step size. ΔV represents the flux divergence at the current time step, and ΔV represents the grid volume.

[0050] Further, step S14 specifically includes:

[0051] S141. In the process of numerical simulation of gas explosion using compressible computational fluid dynamics theory, since the density, volume fraction, specific internal energy, and specific heat ratio of various gases at the initial state (t=0) are known, the initial explosion pressure is calculated using the formula in step S125.

[0052] S142. Since the gas velocity of the explosion grid in the initial state is known, and the adjacent grids are not affected by the explosion, the weighted average velocity between the two grids is calculated. The sound velocity of the current grid can be obtained by using the specific heat ratio, density and initial explosion pressure of the gas. Then the weighted average sound velocity between the two grids is calculated. The grid interface flux is then calculated by using the formula in step S133.

[0053] S143. After obtaining the flux between the mesh interfaces, calculate the flux divergence. Then, the conserved quantity U is updated using the first-order Euler time integral method in step S136.

[0054] S144. The conserved quantity U includes the density, volume fraction, mixing rate, and total energy parameters of various gases. Based on the new conserved quantity, the explosion pressure and interfacial flux at the next time step are calculated.

[0055] S145. Continue iterating to obtain the explosion pressure at each time step until the preset time step is reached, at which point the calculated explosion pressure F is obtained. e This refers to the pressure exerted on the ship's hull by a gas explosion.

[0056] Further, step S2 specifically includes:

[0057] S21. For an ideal gas, under the condition of normal reflection, the incident overpressure is calculated using the following formula:

[0058]

[0059] in, The Mach number of the shock wave is represented by γ, the wave speed by S, and the speed of sound by c; γ represents the specific heat ratio; p a Indicates environmental pressure;

[0060] S22. Based on the calculated incident overpressure, calculate the reflected overpressure using the following formula:

[0061]

[0062] Where, Δp f Indicates reflected overpressure;

[0063] S23. Based on the calculated reflected overpressure, calculate the reflected pressure on the hull, using the following formula:

[0064] F s =Δp f *A

[0065] Where A represents the unit area.

[0066] Further, step S3 specifically includes:

[0067] S31. Obtain input parameters, including the ship's geometry, ship density, and pressure generated by the gas explosion within a preset range;

[0068] S32. Discretize the hull into a certain number of hull structural units with finite volume and finite mass. Before performing the calculation, discretize the hull within the preset range into hull structural units.

[0069] S33. Calculate and determine the neighborhood of each hull structural unit and other hull structural units within that neighborhood.

[0070] S34. Calculate the various forces of the hull structural units that are not in direct contact with the explosive fluid and explosion wave at the current time step;

[0071] S35. Based on the principles of near-field dynamics and Newton's second law, calculate the movement of the hull structural unit s, which is in direct contact with the explosive fluid and explosion wave, at the current time step t, as follows:

[0072]

[0073] Where, ρ s This represents the density of structural unit s; This represents the acceleration of structural unit s;

[0074] S36. In the next time step after the initial state, the quantities of the hull structural units that are not in direct contact with the explosive fluid and explosion wave can be obtained from the right side of the formula in step S35, and the density ρ of all hull structural units is... sSince this is known, the acceleration of the hull structural units that are not in direct contact with the explosive fluid and blast wave can be directly calculated using the formula in step S35. Their speeds can then be calculated. Displacement and spatial position vector

[0075] S37. Calculate the bond elongation s of all structural elements and other structural elements in their neighborhood at the current time step, and use the function μ, which characterizes whether the bond is broken, to obtain the bond breakage status. The specific formula is as follows:

[0076]

[0077] Among them, s c Indicates the critical elongation of the bond;

[0078] S38. Output the position, displacement, velocity, and key fracture status of each hull structural unit at the current time step to assess hull damage from gas explosion.

[0079] S39. Check if the preset time step has been reached. If it has, stop the calculation. If it has not been reached, repeat steps S34-S38.

[0080] Further, step S35 specifically includes:

[0081] S351. Calculate the resultant force of the peri-field dynamic bond forces of other structural elements on structural element s within its neighborhood N. The calculation formula is as follows:

[0082]

[0083] in, This represents the resultant force of the peri-field dynamic bond forces of other structural units acting on structural unit s within its neighborhood N; This represents the relative spatial position vector of structural unit s with respect to other structural units s′ within its neighborhood N. This represents the spatial position vector of structural unit s′. This represents the spatial position vector of structural unit s. This represents the relative displacement vector of structural element s with respect to other structural elements s′ within its neighborhood N. This represents the displacement of structural element s. This represents the displacement of structural element s′;

[0084] In the above formula, It can be expressed by the following formula:

[0085]

[0086] in, Let γ represent the microscopic bond function, γ represent the radius of the neighborhood N, s represent the bond elongation, and μ represent the function used to characterize whether the bond breaks. c Indicates the critical elongation of the bond;

[0087] S352, Calculate the gas explosion and pressure experienced by structural element s. The calculation formula is as follows:

[0088]

[0089] For hull particles that are not in direct contact with the explosive fluid and blast wave, this force is 0;

[0090] S353. Obtain the volume force acting on structural element s. These are known terms.

[0091] Compared with the prior art, the present invention has the following advantages:

[0092] 1. This invention provides a ship gas explosion damage assessment method based on a gas-solid coupling model. It uses compressible fluid dynamics theory to accurately simulate the fluid dynamics behavior of gas explosions and combines it with near-field dynamics methods to simulate the dynamic response of ship structures. In the scenario of ship gas explosions, it can quickly and accurately assess the damage to ship structures under explosion impact. Combined with relevant test data and the calculation results of this model, it provides strong support for ship safety design and accident prevention.

[0093] 2. The present invention provides a ship gas explosion damage assessment method based on a gas-solid coupling model. Through high-precision numerical simulation, it can significantly reduce the dependence on large-scale physical tests, and effectively reduce R&D costs and project economic expenditures while ensuring the reliability of the assessment.

[0094] Based on the above reasons, this invention can be widely applied in fields such as ship gas explosion damage assessment. Attached Figure Description

[0095] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0096] Figure 1 This is a flowchart of the numerical solution model for gas explosion based on computational fluid dynamics theory, as described in this invention.

[0097] Figure 2This is a flowchart of the numerical solution model for ship damage assessment based on the near-field dynamics method of this invention.

[0098] Figure 3 A flowchart for assessing ship gas explosion damage using the method of the present invention is provided for embodiments of the present invention. Detailed Implementation

[0099] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0100] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0101] This invention provides a method for assessing ship gas explosion damage based on a gas-solid coupling model, comprising:

[0102] S1. Based on computational fluid dynamics theory, a numerical solution model for gas explosion is constructed to calculate the pressure of gas explosion on the ship hull;

[0103] S2. To assess the damage to the ship's structure caused by the gas explosion, calculate the reflected pressure on the hull.

[0104] S3. Based on the near-field dynamics method, construct a numerical solution model for ship damage assessment to evaluate the damage caused to the ship hull by gas explosion.

[0105] In specific implementation, as a preferred embodiment of the present invention, such as Figure 1 As shown, step S1 specifically includes:

[0106] S11. Obtain input parameters, including the density, volume fraction, specific internal energy, and specific heat ratio of the gas within a preset range, and discretize the explosion region into a finite element mesh based on the finite volume method.

[0107] S12. Calculate the initial explosion pressure of the explosion point grid by solving the conservation equations and combining them with the state equations.

[0108] S13. Using flux calculation methods, evaluate the flux at the interface between the explosion point grid and adjacent grids to update the conserved variables and obtain the flow field state at the next time step.

[0109] S14. Calculate the pressure of adjacent grids using the state equation based on the updated conserved variables;

[0110] S15. Through gradual iteration of the time step, the process of gas explosion pressure being transmitted to the ship hull is finally simulated.

[0111] In a specific implementation, as a preferred embodiment of the present invention, step S12 specifically includes:

[0112] S121. Calculate the density ρ0 of the gas mixture z using the following formula:

[0113] ρ0=α1ρ1+α2ρ2

[0114] Where ρ1 represents the density of diesel vapor x; ρ2 represents the density of air y;

[0115] S122. Calculate the specific internal energy e0 of the gas mixture z. The calculation formula is as follows:

[0116]

[0117] Where e1 represents the specific internal energy of diesel vapor x, and e2 represents the specific internal energy of air y;

[0118] S123. Based on the calculated density ρ0 and specific internal energy e0 of the mixed gas z, and according to computational fluid dynamics theory, calculate the pressure generated by the mixture of diesel vapor x and air y at the initial explosion time t0 in the explosion point grid. The calculation formula is as follows:

[0119]

[0120] Where p0 represents the pressure generated by the explosion of the gas mixture z; α1 represents the volume fraction of diesel vapor x; α2 represents the volume fraction of air y; for a gas mixture consisting only of these two gases, α1 + α2 = 1; ξ1 represents the parameter related to diesel vapor x; ξ2 represents the parameter related to air y. Γ i The Grüneisen parameter represents the i-th phase; Π1 and Π2 represent functions related to the state equations;

[0121] S124. Calculate the specific heat ratio γ0 of the gas mixture z. The calculation formula is as follows:

[0122]

[0123] Among them, c p1 c represents the isobaric specific heat capacity of diesel volatile gas x; p2 c represents the specific heat capacity of air at constant pressure. v1 c represents the specific heat capacity at constant volume of diesel volatile gas x; v2 This represents the specific heat capacity of air at constant volume (y).

[0124] S125. Treating diesel vapor x, air y, and mixed gas z as ideal gases, according to the ideal gas law in computational fluid dynamics, for an ideal gas Γ... i =γ i Π i =0, calculate the pressure generated by the gas mixture z at the initial explosion moment. The calculation formula is as follows:

[0125] p0=(γ0-1)ρ0e0.

[0126] In a specific implementation, as a preferred embodiment of the present invention, step S13 specifically includes:

[0127] S131. Calculate the wave velocity S of the exploded mesh. own The calculation formula is as follows:

[0128]

[0129] Where, N own =u own *n own , representing the normal velocity component of the exploded mesh, u own n represents the mixing velocity of the gas within the explosion grid. own Represents the surface normal vector of the exploded mesh; p represents the speed of sound in the exploding grid. own γ represents the pressure of the gas within the explosion grid. own ρ represents the specific heat ratio of the gas within the explosion grid. own Indicates the density of the gas within the explosion grid; This represents the normal weighted average velocity component between two exploded grids. This represents the weighted average sound velocity across the exploded grid.

[0130] S132. Calculate the wave velocity S of adjacent grids. nei The calculation formula is as follows:

[0131]

[0132] Where, N nei =u nei *n nei , representing the normal velocity component of adjacent grids, u nei n represents the mixing rate of gases within adjacent grid cells. nei Represents the surface normal vector of adjacent meshes; p represents the speed of sound in adjacent grids. nei γ represents the pressure of the gas within adjacent grid cells. nei ρ represents the specific heat ratio of gases in adjacent grids. nei This indicates the density of gas within adjacent grid cells; This represents the normal weighted average velocity component between two adjacent grid cells. This represents the weighted average sound velocity between adjacent grid cells;

[0133] S133. Using the HLL method, calculate the flux between the exploded grid and adjacent grids. The calculation formula is as follows:

[0134]

[0135] Among them, S own S represents the wave velocity of the exploding mesh; nei F represents the wave velocity of adjacent grids; own F represents the flux of the exploded grid. nei U represents the flux between adjacent grid cells; own U represents the conserved quantity of the exploded mesh; nei Represents the conserved quantity between adjacent grids;

[0136] S134. Calculate the conserved quantity U between the exploded mesh and adjacent meshes at the current time step. The calculation formula is as follows:

[0137]

[0138] Where ρ represents the mixing density of the gas in the current time step explosion grid and the adjacent grid; E represents the total energy of the gas in the current time step explosion grid and the adjacent grid.

[0139] S135. Calculate the flux F between the exploded grid and adjacent grids at the current time step. The calculation formula is as follows:

[0140]

[0141] Where I represents the identity matrix between the current time step's exploded grid and its adjacent grids;

[0142] S136. Flux is used to update conserved quantities. Based on the first-order Euler time integral method in computational fluid dynamics theory, the conserved quantity U for the next time step is calculated. n+1 The calculation formula is as follows:

[0143]

[0144] Among them, U n Δt represents the conserved quantity at the current time step; Δt represents the time step size. ΔV represents the flux divergence at the current time step, and ΔV represents the grid volume.

[0145] In a specific implementation, as a preferred embodiment of the present invention, step S14 specifically includes:

[0146] S141. In the process of numerical simulation of gas explosion using compressible computational fluid dynamics theory, since the density, volume fraction, specific internal energy, and specific heat ratio of various gases at the initial state (t=0) are known, the initial explosion pressure is calculated using the formula in step S125.

[0147] S142. Since the gas velocity of the explosion grid in the initial state is known, and the adjacent grids are not affected by the explosion, the weighted average velocity between the two grids is calculated. The sound velocity of the current grid can be obtained by using the specific heat ratio, density and initial explosion pressure of the gas. Then the weighted average sound velocity between the two grids is calculated. The grid interface flux is then calculated by using the formula in step S133.

[0148] S143. After obtaining the flux between the mesh interfaces, calculate the flux divergence. Then, the conserved quantity U is updated using the first-order Euler time integral method in step S136.

[0149] S144. The conserved quantity U includes the density, volume fraction, mixing rate, and total energy parameters of various gases. Based on the new conserved quantity, the explosion pressure and interfacial flux at the next time step are calculated.

[0150] S145. Continue iterating to obtain the explosion pressure at each time step until the preset time step is reached, at which point the calculated explosion pressure F is obtained. e This refers to the pressure exerted on the ship's hull by a gas explosion.

[0151] In a specific implementation, as a preferred embodiment of the present invention, step S2 specifically includes:

[0152] S21. For an ideal gas, under the condition of normal reflection, the incident overpressure is calculated using the following formula:

[0153]

[0154] in, The Mach number of the shock wave is represented by γ, the wave speed by S, and the speed of sound by c; γ represents the specific heat ratio; p a Indicates environmental pressure;

[0155] S22. Based on the calculated incident overpressure, calculate the reflected overpressure using the following formula:

[0156]

[0157] Where, Δp f This represents the reflected overpressure. In this embodiment, since the speed of sound is known, the shock wave speed is approximately the wave speed calculated in the HLL method, and the reflected overpressure can be calculated. Furthermore, since the specific heat ratio is also a known quantity, the reflected overpressure can be further calculated.

[0158] S23. Based on the calculated reflected overpressure, calculate the reflected pressure on the hull, using the following formula:

[0159] F s =Δp f *A

[0160] Where A represents the unit area.

[0161] At this point, the fluid pressure and reflected pressure per unit area of ​​the hull have been calculated. The pressure experienced by the hull when in direct contact with the explosive fluid and the explosion wave is actually the sum of the fluid pressure and the reflected pressure (hereinafter referred to as the sum pressure).

[0162] In specific implementation, as a preferred embodiment of the present invention, such as Figure 2 As shown, step S3 specifically includes:

[0163] S31. Obtain input parameters, including the ship's geometry, ship density, and pressure generated by the gas explosion within a preset range;

[0164] S32. The basic principle of using the near-field dynamics method for hull damage assessment is to discretize the hull into a certain number of hull structural units with finite volume and finite mass. Before the calculation, the hull within the preset range is discretized into hull structural units.

[0165] S33. Calculate and determine the neighborhood of each hull structural unit and other hull structural units within that neighborhood.

[0166] S34. Calculate the various forces of the hull structural units that are not in direct contact with the explosive fluid and explosion wave at the current time step;

[0167] S35. Based on the principles of near-field dynamics and Newton's second law, calculate the movement of the hull structural unit s, which is in direct contact with the explosive fluid and explosion wave, at the current time step t, as follows:

[0168]

[0169] Where, ρ s This represents the density of structural unit s; The acceleration of structural unit s is represented. In this embodiment, the hull structural units that are in direct contact with the explosive fluid and the explosion wave will be moved to a new position by the gas explosion and pressure. The displacement of these structural units can be calculated based on the changes in their old and new positions. The velocity can be obtained by removing the displacement and dividing it by the time step.

[0170] S36. In the next time step after the initial state, the quantities of the hull structural units that are not in direct contact with the explosive fluid and explosion wave can be obtained from the right side of the formula in step S35, and the density ρ of all hull structural units is... s Since this is known, the acceleration of the hull structural units that are not in direct contact with the explosive fluid and blast wave can be directly calculated using the formula in step S35. Their speeds can then be calculated. Displacement and spatial position vector

[0171] S37. Calculate the bond elongation s of all structural elements and other structural elements in their neighborhood at the current time step, and use the function μ, which characterizes whether the bond is broken, to obtain the bond breakage status. The specific formula is as follows:

[0172]

[0173] Among them, s c Indicates the critical elongation of the bond;

[0174] S38. Output the position, displacement, velocity, and key fracture status of each hull structural unit at the current time step to assess hull damage from gas explosion.

[0175] S39. Check if the preset time step has been reached. If it has, stop the calculation. If it has not been reached, repeat steps S34-S38.

[0176] In a specific implementation, as a preferred embodiment of the present invention, step S35 specifically includes:

[0177] S351. Calculate the resultant force of the peri-field dynamic bond forces of other structural elements on structural element s within its neighborhood N. The calculation formula is as follows:

[0178]

[0179] in, This represents the resultant force of the peri-field dynamic bond forces of other structural units acting on structural unit s within its neighborhood N; This represents the relative spatial position vector of structural unit s with respect to other structural units s′ within its neighborhood N. This represents the spatial position vector of structural unit s′. This represents the spatial position vector of structural unit s. This represents the relative displacement vector of structural element s with respect to other structural elements s′ within its neighborhood N. This represents the displacement of structural element s. This represents the displacement of structural element s′;

[0180] In the above formula, It can be expressed by the following formula:

[0181]

[0182] in, Let γ represent the microscopic bond function, γ represent the radius of the neighborhood N, s represent the bond elongation, and μ represent the function used to characterize whether the bond breaks. c Indicates the critical elongation of the bond;

[0183] S352, Calculate the gas explosion and pressure experienced by structural element s. The calculation formula is as follows:

[0184]

[0185] For hull particles that are not in direct contact with the explosive fluid and blast wave, this force is 0;

[0186] S353. Obtain the volume force acting on structural element s. These are known terms.

[0187] Example

[0188] like Figure 3 As shown, this invention provides a method for assessing ship gas explosion damage based on a gas-solid coupling model, comprising:

[0189] Step 1: Select the ship and gas explosion scenario to be evaluated;

[0190] Step 2: Use specialized equipment to examine the geometric model of the vessel to be evaluated;

[0191] Step 3: Investigate information such as gas volume fraction, density, specific internal energy, and explosion location during a gas explosion;

[0192] Step 4: Input the data obtained in Step 2 and Step 3 into the ship gas explosion damage assessment model based on the gas-solid coupling model proposed in this invention to obtain the ship gas explosion damage at different times.

[0193] Step 5: Based on the ship's gas explosion damage at different times obtained in Step 4, formulate a suitable rescue plan based on the ship damage assessment.

[0194] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for assessing ship gas explosion damage based on a gas-solid coupling model, characterized in that, include: S1. Based on computational fluid dynamics theory, a numerical solution model for gas explosion is constructed to calculate the pressure of the gas explosion on the ship's hull, specifically including: S11. Obtain input parameters, including the density, volume fraction, specific internal energy, and specific heat ratio of the gas within a preset range, and discretize the explosion region into a finite element mesh based on the finite volume method. S12. Calculate the initial explosion pressure of the explosion point grid by solving the conservation equations and combining them with the state equations. S13. Using flux calculation methods, evaluate the flux at the interface between the explosion point grid and adjacent grids to update the conserved variables and obtain the flow field state at the next time step. S14. Calculate the pressure of adjacent grids using the state equation based on the updated conserved variables; S15. Through step-by-step iteration of time steps, the process of gas explosion pressure being transmitted to the hull is finally simulated. S2. To assess the damage to the ship's structure caused by the gas explosion, calculate the reflected pressure on the hull. S3. Based on near-field dynamics methods, construct a numerical solution model for ship damage assessment to evaluate the damage caused to the hull by gas explosions, specifically including: S31. Obtain input parameters, including the ship's geometry, ship density, and pressure generated by the gas explosion within a preset range; S32. Discretize the hull into a certain number of hull structural units with finite volume and finite mass. Before performing the calculation, discretize the hull within the preset range into hull structural units. S33. Calculate and determine the neighborhood of each hull structural unit and other hull structural units within that neighborhood. S34. Calculate the various forces of the hull structural units that are not in direct contact with the explosive fluid and explosion wave at the current time step; S35. Based on the principles of near-field dynamics and Newton's second law, calculate the movement of the hull structural unit s, which is in direct contact with the explosive fluid and explosion wave, at the current time step t, as follows: Where, ρ s This represents the density of structural unit s; This represents the acceleration of structural unit s; S36. In the next time step after the initial state, the quantities of the hull structural units that are not in direct contact with the explosive fluid and explosion wave can be obtained from the right side of the formula in step S35, and the density ρ of all hull structural units is... s Since this is known, the acceleration of the hull structural units that are not in direct contact with the explosive fluid and blast wave can be directly calculated using the formula in step S35. Their speeds can then be calculated. Displacement and spatial position vector S37. Calculate the bond elongation s of all structural elements and other structural elements in their neighborhood at the current time step, and use the function μ, which characterizes whether the bond is broken, to obtain the bond breakage status. The specific formula is as follows: Among them, s c Indicates the critical elongation of the bond; S38. Output the position, displacement, velocity, and key fracture status of each hull structural unit at the current time step to assess hull damage from gas explosion. S39. Check if the preset time step has been reached. If it has, stop the calculation. If it has not been reached, repeat steps S34-S38.

2. The method for assessing ship gas explosion damage based on a gas-solid coupling model according to claim 1, characterized in that, Step S12 specifically includes: S121. Calculate the density ρ0 of the gas mixture z using the following formula: ρ0=α1ρ1+α2ρ2 Where ρ1 represents the density of diesel vapor x; ρ2 represents the density of air y; S122. Calculate the specific internal energy e0 of the gas mixture z. The calculation formula is as follows: Where e1 represents the specific internal energy of diesel vapor x, and e2 represents the specific internal energy of air y; S123. Based on the calculated density ρ0 and specific internal energy e0 of the mixed gas z, and according to computational fluid dynamics theory, calculate the pressure generated by the mixture of diesel vapor x and air y at the initial explosion time t0 in the explosion point grid. The calculation formula is as follows: Where p0 represents the pressure generated by the explosion of the gas mixture z; α1 represents the volume fraction of diesel vapor x; α2 represents the volume fraction of air y; for a gas mixture consisting only of these two gases, α1 + α2 = 1; ξ1 represents the parameter related to diesel vapor x; ξ2 represents the parameter related to air y. Γ i The Grüneisen parameter represents the i-th phase; Π1 and Π2 represent functions related to the state equations; S124. Calculate the specific heat ratio γ0 of the gas mixture z. The calculation formula is as follows: Among them, c p1 c represents the isobaric specific heat capacity of diesel volatile gas x; p2 c represents the specific heat capacity of air at constant pressure y; v1 c represents the specific heat capacity at constant volume of diesel volatile gas x; v2 This represents the specific heat capacity of air at constant volume (y). S125. Treating diesel vapor x, air y, and mixed gas z as ideal gases, according to the ideal gas law in computational fluid dynamics, for an ideal gas Γ... i =γ i Π i =0, calculate the pressure generated by the gas mixture z at the initial explosion moment. The calculation formula is as follows: p0=(γ0-1)ρ0e0.

3. The method for assessing ship gas explosion damage based on a gas-solid coupling model according to claim 1, characterized in that, Step S13 specifically includes: S131. Calculate the wave velocity S of the exploded mesh. own The calculation formula is as follows: Where, N own =u own *n own , representing the normal velocity component of the exploded mesh, u own n represents the mixing velocity of the gas within the explosion grid. own Represents the surface normal vector of the exploded mesh; p represents the speed of sound in the exploding grid. own γ represents the pressure of the gas within the explosion grid. own ρ represents the specific heat ratio of the gas within the explosion grid. own Indicates the density of the gas within the explosion grid; This represents the normal weighted average velocity component between two exploded grids. This represents the weighted average sound velocity across the exploded grid. S132. Calculate the wave velocity S of adjacent grids. nei The calculation formula is as follows: Where, N nei =u nei *n nei , representing the normal velocity component of adjacent grids, u nei n represents the mixing velocity of gases within adjacent grid cells. nei Represents the surface normal vector of adjacent meshes; p represents the speed of sound in adjacent grids. nei γ represents the gas pressure within adjacent grid cells. nei ρ represents the specific heat ratio of gases in adjacent grids. nei This indicates the density of gas within adjacent grid cells; This represents the normal weighted average velocity component between two adjacent grid cells. This represents the weighted average sound velocity between adjacent grid cells; S133. Using the HLL method, calculate the flux between the exploded grid and adjacent grids. The calculation formula is as follows: Among them, S own S represents the wave velocity of the exploding mesh; nei F represents the wave velocity of adjacent grids. own F represents the flux of the exploded grid; nei U represents the flux between adjacent grid cells; own U represents the conserved quantity of the exploded mesh; nei Represents the conserved quantity between adjacent grids; S134. Calculate the conserved quantity U between the exploded mesh and adjacent meshes at the current time step. The calculation formula is as follows: Where ρ represents the mixing density of the gas in the current time step explosion grid and the adjacent grid; E represents the total energy of the gas in the current time step explosion grid and the adjacent grid. S135. Calculate the flux F between the exploded grid and adjacent grids at the current time step. The calculation formula is as follows: Where I represents the identity matrix between the current time step's exploded grid and its adjacent grids; S136. Flux is used to update conserved quantities. Based on the first-order Euler time integral method in computational fluid dynamics theory, the conserved quantity U for the next time step is calculated. n+1 The calculation formula is as follows: Among them, U n Δt represents the conserved quantity at the current time step; Δt represents the time step size. ΔV represents the flux divergence at the current time step, and ΔV represents the grid volume.

4. The method for assessing ship gas explosion damage based on a gas-solid coupling model according to claim 1, characterized in that, Step S14 specifically includes: S141. In the process of numerical simulation of gas explosion using compressible computational fluid dynamics theory, since the density, volume fraction, specific internal energy, and specific heat ratio of various gases in the initial state are known, the initial explosion pressure is calculated using the formula in step S125. S142. Since the gas velocity of the explosion grid in the initial state is known, and the adjacent grids are not affected by the explosion, the weighted average velocity between the two grids is calculated. The sound velocity of the current grid can be obtained by using the specific heat ratio, density and initial explosion pressure of the gas. Then the weighted average sound velocity between the two grids is calculated. The grid interface flux is then calculated by using the formula in step S133. S143. After obtaining the flux between the mesh interfaces, calculate the flux divergence ▽F. n Then, the first-order Euler time integration method in step S136 is used to update the conserved quantity U. S144. The conserved quantity U includes the density, volume fraction, mixing rate, and total energy parameters of various gases. Based on the new conserved quantity, the explosion pressure and interfacial flux at the next time step are calculated. S145. Continue iterating to obtain the explosion pressure at each time step until the preset time step is reached, at which point the calculated explosion pressure F is obtained. e This refers to the pressure exerted on the ship's hull by a gas explosion.

5. The method for assessing ship gas explosion damage based on a gas-solid coupling model according to claim 1, characterized in that, Step S2 specifically includes: S21. For an ideal gas, under the condition of normal reflection, the incident overpressure is calculated using the following formula: in, The Mach number of the shock wave is represented by γ, the wave speed by S, and the speed of sound by c; γ represents the specific heat ratio; p a Indicates environmental pressure; S22. Based on the calculated incident overpressure, calculate the reflected overpressure using the following formula: Where, Δp f Indicates reflected overpressure; S23. Based on the calculated reflected overpressure, calculate the reflected pressure on the hull, using the following formula: F s =Δp f *A Where A represents the unit area.

6. The method for assessing ship gas explosion damage based on a gas-solid coupling model according to claim 1, characterized in that, Step S35 specifically includes: S351. Calculate the resultant force of the peri-field dynamic bond forces of other structural elements on structural element s within its neighborhood N. The calculation formula is as follows: in, This represents the resultant force of the peri-field dynamic bond forces of other structural units acting on structural unit s within its neighborhood N; x represents the relative spatial position vector of structural unit s with respect to other structural units s′ within its neighborhood N. s′ This represents the spatial position vector of structural unit s′. This represents the spatial position vector of structural unit s. This represents the relative displacement vector of structural element s with respect to other structural elements s′ within its neighborhood N. This represents the displacement of structural element s. This represents the displacement of structural element s′; In the above formula, It can be expressed by the following formula: in, Let γ represent the microscopic bond function, γ represent the radius of the neighborhood N, s represent the bond elongation, and μ represent the function used to characterize whether the bond breaks. c Indicates the critical elongation of the bond; S352, Calculate the gas explosion and pressure experienced by structural element s. The calculation formula is as follows: For hull particles that are not in direct contact with the explosive fluid and blast wave, this force is 0; S353. Obtain the volume force acting on structural element s. These are known terms.

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