Dynamic simulation method of laser ablation based on virtual fluid method

Abstract

The application is a kind of laser ablation dynamic simulation method based on virtual fluid method, and the implementation steps mainly include three steps: first, the laser ablation speed v is obtained according to the material properties, the incoming flow state, the laser to target power and other parameters; then the solid wall forced displacement is calculated, and the displacement size is equal to the time step * laser ablation speed v; finally, after the solid wall state is solved by using the traditional virtual fluid method, the solid wall forced displacement is added, and the solid wall state, position and fluid state at this moment can be obtained. The application has the advantages that the material surface flow condition under the ablation condition at any moment and the unsteady flow phenomenon caused by ablation can be better simulated, and a kind of way is provided so that the calculation method used for single medium can be used in the multi-medium problem of material laser ablation.

Description

Technical Field

[0001] This invention belongs to the field of dynamic numerical simulation of multi-medium flow in laser ablation, and is used to solve complex flow problems of laser irradiation on material surfaces with a certain velocity coupled with the flow. Background Technology

[0002] With the rapid development of aircraft performance, research on dynamic laser ablation models and simulations, as well as studies on the dynamic ablation evolution under laser irradiation, is becoming increasingly important. Existing methods typically use steady or quasi-steady approaches for simulation, which can only calculate the material surface flow under ablation conditions at a specific moment. They struggle to simulate the unsteady flow caused by time-varying material ablation, making it difficult to represent the dynamic process. Summary of the Invention

[0003] This invention proposes a dynamic simulation method for compressible multi-media flow laser ablation based on a virtual fluid approach, addressing processes such as airflow erosion, laser ablation of solid walls, and mixing of ablation products. For complex flow problems involving laser irradiation of material surfaces with a certain velocity-coupled flow, a dynamic simulation method related to flow state, laser parameters, and material properties is established based on the material ablation characteristics, and dynamic simulation software is implemented.

[0004] The technical solution of this invention is:

[0005] A dynamic simulation method for laser ablation based on the virtual fluid approach includes:

[0006] 1) Determine the laser ablation rate;

[0007] 2) Calculate the forced displacement of the solid wall;

[0008] 3) Solve for the solid state and fluid state to obtain the location of the solid-wall interface;

[0009] 4) Determine the position of the solid-wall interface after laser ablation and determine the direction of boundary movement. If the boundary movement direction is towards the solid-wall area, proceed to step 5); otherwise, proceed to step 7.

[0010] 5) Update the fluid state in the ablation zone to obtain the actual fluid state in the ablation zone;

[0011] 6) Update the solid state and fluid state to complete the simulation method.

[0012] 7) Update the solid state in the ablation region to obtain the true solid state in the ablation region;

[0013] 8) Update the solid wall state and fluid state to complete the simulation method.

[0014] Preferably, the method for determining the laser ablation rate is as follows:

[0015] Based on parameters such as material properties, incoming flow state, and laser power to target, the laser ablation velocity is obtained, with the direction being perpendicular to the solid wall and inward.

[0016] Preferably, the forced displacement of the solid wall is equal to the product of the time step dt and the laser ablation rate.

[0017] Preferably, the method for obtaining the solid-wall interface position is as follows: using the solid-wall forced displacement obtained in step 2), the solid-wall interface position is solved and defined as the solid-wall boundary I after ablation.

[0018] Preferably, the method for solving the solid state and the fluid state is as follows:

[0019] Based on the actual fluid state in the fluid region and the actual solid state in the solid wall region, the solution to the interface Riemann problem is obtained as the initial virtual solid state in the fluid region and the initial virtual fluid state in the solid wall region.

[0020] Preferably, the method for determining the location of the solid-wall interface after laser ablation is as follows:

[0021] Based on the solid-wall interface position in step 3), the solid-wall forced displacement in step 2) is added to obtain the solid-wall interface position after laser ablation, which is defined as the solid-wall boundary II after ablation.

[0022] Preferably, the method for obtaining the true fluid state in the ablation region is as follows:

[0023] 51) The ablation virtual fluid state in the ablation region is determined by the real fluid state in the fluid region;

[0024] 52) Using the initial virtual fluid state in the ablation region and the real solid state in the solid wall region, establish the interface Riemann problem of the solid wall boundary II after ablation, thereby obtaining the ablation virtual solid state in the ablation region.

[0025] 53) The density of the real fluid in the ablation zone is defined as the density ρ of the ablation virtual fluid in the ablation zone. I The velocity of the real fluid in the ablation region is defined as the laser ablation velocity obtained in step 1), and the pressure of the real fluid in the ablation region is defined as the average of the pressure of the ablated virtual fluid and the pressure of the ablated virtual solid in the ablation region.

[0026] Preferably, the method for updating the solid state and the fluid state is as follows:

[0027] 61) Using the real fluid state in the ablation region and the real fluid state in the fluid region obtained in step 5), a Riemann problem is established, and the Riemann solution is used to correct the real fluid state in the fluid region.

[0028] 62) Using the state of the real fluid in the ablation region and the state of the real solid in the solid wall region obtained in step 5), a Riemann problem is established, and the Riemann solution is used to correct the state of the real solid in the solid wall region.

[0029] Preferably, the true solid state in the ablation region is obtained, specifically as follows:

[0030] 71) The ablation virtual solid state in the ablation region is determined by the real solid state in the solid region;

[0031] 72) Using the initial virtual solid state in the ablation region and the real fluid state in the fluid region, establish the interface Riemann problem of the solid-wall boundary II after ablation, thereby obtaining the ablation virtual fluid state in the ablation region.

[0032] 73) The temperature of the real solid in the ablation zone is defined as the temperature of the ablation virtual solid in the ablation zone; the stress and strain of the real solid in the ablation zone are defined as the stress and strain of the ablation virtual solid in the ablation zone.

[0033] Preferably, the method for updating the solid state and the fluid state is as follows:

[0034] 81) Using the real solid state in the ablation region and the real fluid state in the fluid region obtained in step 7), a Riemann problem is established, and the Riemann solution is used to correct the real fluid state in the fluid region.

[0035] 82) Using the state of the real solid in the ablation region and the state of the real solid in the solid wall region obtained in step 7), a Riemann problem is established, and the Riemann solution is used to correct the state of the real solid in the solid wall region.

[0036] The advantages of this invention compared to the prior art are:

[0037] 1) This invention can simulate the flow of material surface under ablation conditions at a certain moment;

[0038] 2) This invention can simulate unsteady flow caused by material ablation over time;

[0039] 3) The present invention is simple to calculate, and after solving the interface state, the traditional method for solving single media can be used to solve multi-media flow. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the calculation area and the location of laser irradiation.

[0041] Figure 2 A schematic diagram of the depressions and solid boundary displacement caused by laser ablation.

[0042] Figure 3 This diagram illustrates the computational domain correction and the updates of interface and fluid states.

[0043] Figure 4 This is a schematic diagram of the solid wall boundary displacement under the action of incoming flow and laser ablation.

[0044] Figure 5 This is a schematic diagram of the dynamic simulation method.

[0045] Figure 6 This is a schematic diagram of the solid wall boundary state before ablation.

[0046] Figure 7 This is a schematic diagram of the status of the three regions.

[0047] Figure 8 This is a schematic diagram of the ablation state. Detailed Implementation

[0048] like Figure 5 As shown, the laser ablation dynamic simulation method based on the virtual fluid method of the present invention includes the following steps:

[0049] 1) Determine the laser ablation rate

[0050] Based on parameters such as material properties, incoming flow state, and laser power to the target, CFD calculations including chemical reactions are used to obtain the laser ablation velocity v, thereby obtaining the corresponding laser ablation velocity distribution matrix v. Figure 4 This is a schematic diagram of the solid wall boundary displacement under the action of incoming flow and laser ablation.

[0051] The laser ablation velocity distribution matrix v represents the laser ablation velocity distribution at all points on the laser-irradiated surface and surrounding area, and includes [x, y, z, v]. Here, x, y, and z represent the spatial coordinates of all points on the laser-irradiated surface and surrounding area, v represents the laser ablation velocity, and the laser ablation direction is perpendicular to the solid wall and inwards.

[0052] 2) Determine the magnitude of the forced displacement of the solid wall

[0053] Based on the laser ablation velocity distribution matrix v and the time step dt calculated by CFD, the forced displacement distribution matrix s = [1, 1, 1, dt] of the laser ablation solid wall is calculated. T *v.

[0054] The forced displacement distribution matrix 's' of laser ablation on a solid wall represents the interface displacement distribution caused by laser ablation at all points on the laser-irradiated surface and surrounding area, and includes [x, y, z, s]. Here, x, y, and z represent spatial coordinates, and s represents the interface displacement caused by laser ablation at the corresponding spatial coordinate location, with the displacement direction perpendicular to the solid wall and inwards.

[0055] 3) Solve for the solid state and fluid state to obtain the location of the solid-wall interface.

[0056] 31) Solve the interface Riemann problem using fluid states such as pressure, temperature, density, and velocity, and solid state states such as temperature, stress, and strain. Use the solution to the interface Riemann problem to define the state of the virtual fluid / virtual solid, such as... Figure 6 As shown, subscript I denotes "the solution to the interface Riemann problem constructed on the solid wall boundary before ablation," hollow grid points represent virtual media, i.e., virtual fluid / solid, and solid grid points represent real media, i.e., real fluid / solid. That is, based on the real fluid state in the fluid region and the real solid state in the solid wall region, the solution to the interface Riemann problem is obtained as the initial virtual solid state in the fluid region and the initial virtual fluid state in the solid wall region.

[0057] 32) Based on the flow field information, the position of the solid wall interface can be obtained by solving the Level-Set function, which is defined as the solid wall boundary I before ablation.

[0058] Fluid states include: pressure, temperature, density, and velocity;

[0059] Solid states include: temperature, stress, and strain.

[0060] 4) Update the position of the solidified wall boundary

[0061] Based on the solid-wall interface position obtained in step 3), and the forced displacement distribution matrix s of the laser ablation solid wall obtained in step 2), the solid-wall interface position after laser ablation (the interface position between the solid wall region and the ablation region) is obtained, defined as the solid-wall boundary II after ablation. Figure 7 As shown, based on the forced displacement s of the solid wall, the direction of boundary movement is determined. If the boundary movement direction is towards the solid wall region, then grid points appear in the ablation region where "the medium type is fluid but the medium state is not clearly defined," such as... Figure 8 As shown, proceed to step 5). Conversely, if grid points appear in the ablation region at this time where "the medium type is solid but the medium state is not clearly defined", proceed to step 7). The region between the solid wall boundary I before ablation and the solid wall boundary II after ablation is taken as the ablation region.

[0062] 5) Update the fluid state in the ablation zone to obtain the true fluid state in the ablation zone.

[0063] like Figure 8 As shown, three regions exist near the solid wall: a fluid region, a solid wall region, and an ablation region (i.e., the region where the solid wall transforms into a fluid). The fluid state in the fluid region is known, and the solid state in the solid wall region is known.

[0064] 51) The ablation virtual fluid state in the ablation region is determined by the real fluid state in the fluid region; the initial virtual fluid state in the ablation region is known, i.e., what is required in step 3).

[0065] 52) Using the initial virtual fluid state in the ablation region and the real solid state in the solid wall region, establish the interface Riemann problem at the solid wall boundary II after ablation. Solving this interface Riemann problem yields the solution to the interface Riemann problem constructed on the solid wall boundary after ablation, i.e., subscript II. Thus, the ablation virtual solid state in the ablation region is obtained.

[0066] 53) Determine the actual fluid state in the ablation zone.

[0067] The density of the real fluid in the ablation zone is defined as the density ρ of the ablation virtual fluid in the ablation zone. I The velocity is defined as the laser ablation velocity v obtained in (1), and the pressure is defined as the average of the pressure of the ablation virtual fluid and the pressure of the ablation virtual solid in the ablation region, i.e., (p I +p II ) / 2. Where, p I p represents the pressure of the ablation virtual fluid in the ablation region. II Let p be the pressure of the ablated virtual solid in the ablation region. I p represents the pressure of the ablation virtual fluid in the ablation region. II This represents the pressure of the ablation of the virtual solid within the ablation region.

[0068] 6) Update the solid state and fluid state to complete the simulation method.

[0069] 61) For example Figure 8 As shown, the Riemann problem is established using the real fluid state in the ablation region and the real fluid state in the fluid region obtained in step 5), and the Riemann solution is used to correct the real fluid state in the fluid region.

[0070] 62) Using the state of the real fluid in the ablation region and the state of the real solid in the solid wall region obtained in step 5), a Riemann problem is established, and the Riemann solution is used to correct the state of the real solid in the solid wall region.

[0071] 7) Update the solid state in the ablation region to obtain the true solid state in the ablation region.

[0072] The vicinity of the solid wall presents three regions: the fluid region, the solid wall region, and the ablation region (i.e., the region where the fluid transforms into a solid wall). Among them, the fluid state in the fluid region is known, and the solid state in the solid wall region is known.

[0073] 71) The ablation virtual solid state in the ablation region is determined by the real solid state in the solid region; the initial virtual solid state in the ablation region is known, i.e., what is required in step 3).

[0074] 72) Using the initial virtual solid state in the ablation region and the real fluid state in the fluid region, establish the interface Riemann problem at the solid-wall boundary II after ablation. Solving this interface Riemann problem yields the solution to the interface Riemann problem constructed on the solid-wall boundary after ablation, i.e., subscript II. This allows us to obtain the ablation virtual fluid state in the ablation region.

[0075] 73) Determine the true solid state in the ablation zone.

[0076] The temperature of the real solid in the ablation zone is defined as the temperature of the ablated virtual solid in the ablation zone.

[0077] The stress and strain of the real solid in the ablation zone are defined as the stress and strain of the ablation virtual solid in the ablation zone.

[0078] 8) Update the solid state and fluid state to complete the simulation method.

[0079] 81) such as Figure 8 As shown, the Riemann problem is established using the real solid state in the ablation region and the real fluid state in the fluid region obtained in step 7), and the Riemann solution is used to correct the real fluid state in the fluid region.

[0080] 82) Using the state of the real solid in the ablation region and the state of the real solid in the solid wall region obtained in step 7), a Riemann problem is established, and the Riemann solution is used to correct the state of the real solid in the solid wall region.

[0081] Figure 1 This is a schematic diagram of the calculation area and the location of laser irradiation. Figure 2 A schematic diagram of the depressions and solid boundary displacement caused by laser ablation. Figure 3 This diagram illustrates the computational domain correction and the updates of interface and fluid states.

[0082] Example

[0083] Taking common carbon / phenolic materials as an example, assuming the incoming flow parameters are [H15km, Ma6], and the laser power density to the target is 15kW / cm². 2 .

[0084] 1) Determine the laser ablation rate

[0085] Based on parameters such as material properties, incoming flow state, and laser power to target, the laser ablation rate is approximately 4 mm / s, with the direction being perpendicular to the solid wall and inward.

[0086] 2) Determine the magnitude of the forced displacement of the solid wall

[0087] Assuming the CFL number is 0.5, the forced displacement of the solid wall is calculated to be 7.19E-002s*4mm / s, which is approximately 0.28mm.

[0088] 3) Solve for the solid state and fluid state.

[0089] The fluid state and solid wall state are solved using the traditional virtual fluid method. After the solid wall boundary is determined, a forced displacement of the solid wall is added. After the boundary is moved, the state of the newly added fluid domain A is the same as the state of the nearby grid point B. The fluid state is then solved using the traditional virtual fluid method.

[0090] This invention utilizes a virtual fluid method, which facilitates the solution of multi-medium Riemannian problems, to address the interaction between the fluid and solid domains. The laser ablation velocity is expressed as a function of a series of parameters, multiplied by the time step to obtain the wall ablation displacement. By forcibly shifting the two-phase boundary, the effect of laser ablation on the wall surface is simulated. This method enables dynamic simulation of laser ablation of walls under the influence of flow, providing a powerful tool for tightly coupled dynamic calculations of flow / laser ablation / solid processes.

[0091] This invention is not limited to the simulation calculation of flow phenomena such as laser ablation of flat materials, but can be extended to the dynamic simulation calculation of damage to arbitrary shapes and materials.

[0092] The foregoing has provided a detailed description of the dynamic simulation method for compressible multi-medium flow laser ablation based on the virtual fluid approach of this invention. Specific examples have been used to illustrate the principles and implementation methods of this invention; these examples are merely illustrative to aid in understanding the method and its core concepts. It should be noted that any simple modifications made to the above examples without departing from the technical essence of this invention fall within the scope of this invention.

[0093] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A dynamic simulation method for laser ablation based on virtual fluid method, characterized in that, include: 1) Determine the laser ablation rate; 2) Calculate the forced displacement of the solid wall; 3) Solve for the solid state and fluid state to obtain the location of the solid-wall interface; 4) Determine the position of the solid-wall interface after laser ablation and determine the direction of boundary movement. If the boundary movement direction is towards the solid-wall area, proceed to step 5); otherwise, proceed to step 7). 5) Update the fluid state in the ablation zone to obtain the true fluid state in the ablation zone; 6) Update the solid state and fluid state to complete the simulation method; 7) Update the solid state in the ablation region to obtain the true solid state in the ablation region; 8) Update the solid state and fluid state to complete the simulation method; The methods for solving the solid state and fluid state are as follows: Based on the actual fluid state in the fluid region and the actual solid state in the solid wall region, the solution to the interface Riemann problem is obtained as the initial virtual solid state in the fluid region and the initial virtual fluid state in the solid wall region. The method for determining the location of the solid-wall interface after laser ablation is as follows: Based on the solid-wall interface position in step 3), the solid-wall forced displacement in step 2) is added to obtain the solid-wall interface position after laser ablation, which is defined as the solid-wall boundary II after ablation. The method for obtaining the actual fluid state in the ablation zone is as follows: 51) The ablation virtual fluid state in the ablation region is determined by the real fluid state in the fluid region; 52) Using the initial virtual fluid state in the ablation region and the real solid state in the solid wall region, establish the interface Riemann problem of the solid wall boundary II after ablation, thereby obtaining the ablation virtual solid state in the ablation region. 53) The density of the real fluid in the ablation zone is defined as the density ρ of the ablation virtual fluid in the ablation zone. I The velocity of the real fluid in the ablation region is defined as the laser ablation velocity obtained in step 1), and the pressure of the real fluid in the ablation region is defined as the average of the pressure of the ablation virtual fluid and the pressure of the ablation virtual solid in the ablation region. To obtain the true solid state in the ablation region, specifically: 71) The ablation virtual solid state in the ablation region is determined by the real solid state in the solid region; 72) Using the initial virtual solid state in the ablation region and the real fluid state in the fluid region, establish the interface Riemann problem of the solid-wall boundary II after ablation, thereby obtaining the ablation virtual fluid state in the ablation region. 73) The temperature of the real solid in the ablation zone is defined as the temperature of the ablated virtual solid in the ablation zone; The stress and strain of the real solid in the ablation zone are defined as the stress and strain of the ablation virtual solid in the ablation zone.

2. The laser ablation dynamic simulation method based on virtual fluid method according to claim 1, characterized in that, The method for determining the laser ablation rate is as follows: Based on parameters such as material properties, incoming flow state, and laser power to target, the laser ablation velocity is obtained, with the direction being perpendicular to the solid wall and inward.

3. The laser ablation dynamic simulation method based on virtual fluid method according to claim 1, characterized in that, The forced displacement of the solid wall is equal to the product of the time step dt and the laser ablation rate.

4. The laser ablation dynamic simulation method based on virtual fluid method according to claim 1, characterized in that, The method for obtaining the solid-wall interface position is as follows: using the solid-wall forced displacement obtained in step 2), the solid-wall interface position is obtained by solving, which is defined as the solid-wall boundary I after ablation.

5. The laser ablation dynamic simulation method based on virtual fluid method according to claim 4, characterized in that, In step 6), the method for updating the solid state and fluid state is as follows: 61) Using the real fluid state in the ablation region and the real fluid state in the fluid region obtained in step 5), a Riemann problem is established, and the Riemann solution is used to correct the real fluid state in the fluid region. 62) Using the state of the real fluid in the ablation region and the state of the real solid in the solid wall region obtained in step 5), a Riemann problem is established, and the Riemann solution is used to correct the state of the real solid in the solid wall region.

6. The laser ablation dynamic simulation method based on virtual fluid method according to claim 1 or 5, characterized in that, In step 8), the method for updating the solid state and fluid state is as follows: 81) Using the real solid state in the ablation region and the real fluid state in the fluid region obtained in step 7), a Riemann problem is established, and the Riemann solution is used to correct the real fluid state in the fluid region. 82) Using the state of the real solid in the ablation region and the state of the real solid in the solid wall region obtained in step 7), a Riemann problem is established, and the Riemann solution is used to correct the state of the real solid in the solid wall region.

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