Method, device and equipment for adjusting time step of vpi simulation and medium

Abstract

The present application relates to the technical field of superconducting magnet manufacturing and insulation impregnation process optimization, and discloses a VPI simulation time step length adjusting method, device, equipment and medium, the method comprising: obtaining a VPI simulation model and a target library number, wherein the VPI simulation model is provided with the rheological property and boundary condition of resin; when the boundary condition is a single injection port based on a constant pressure boundary, determining the first maximum flow rate and the first minimum grid size of the resin at the current time step length according to the VPI simulation model; and determining the next time step length according to the first maximum flow rate, the first minimum grid size and the target library number. The present application dynamically adjusts the time step length through the actual flow rate of the resin at different stages, avoids redundant calculation, and thus significantly shortens the total simulation time.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of superconducting magnet manufacturing and VPI process simulation, and particularly relates to a time step adjustment method, device and equipment for VPI simulation and a medium. BACKGROUND

[0002] Superconducting magnets are widely used in fusion devices, particle accelerators, magnetic resonance imaging and high-field experimental equipment due to their high current carrying capacity and strong magnetic field output characteristics. In order to ensure that the superconducting magnet has good insulation performance and mechanical strength during operation, the vacuum pressure impregnation (VPI) process is usually used for overall impregnation and curing of the coil. The process injects low viscosity epoxy resin into the winding under vacuum, so that it fully penetrates into the coil gap and glass fiber insulation layer, and then completes densification and curing under pressure, thereby improving the reliability and stability of the superconducting magnet.

[0003] When numerically simulating the VPI process, epoxy resin as a non-Newtonian fluid needs to be calculated by using a multiphase flow model combined with the rheological properties of viscosity changing with temperature and time. Since the inlet is usually set as a constant pressure boundary and the outlet is a vacuum pressure boundary in the VPI process, the flow velocity is fast when the resin just enters the fluid domain; as the impregnation progresses, the velocity of the resin in the fluid domain gradually decreases. Such a significant change in velocity gradient puts high requirements on the selection of simulation time step.

[0004] In the explicit calculation method, the time step is subject to the Courant number. If the time step is too large, it will lead to numerical instability or even calculation divergence; if the time step is too small, it will significantly increase the calculation cost and simulation time. In existing Computational Fluid Dynamics (CFD) simulation, a fixed time step strategy is generally used, which cannot automatically adjust the calculation time step according to the dynamic change of resin flow rate, resulting in the need to set a very small time step manually to ensure calculation stability in the initial high-speed flow stage of the resin, while the same small step is still used in the low-speed stage, causing a lot of waste of computing resources and low calculation efficiency. SUMMARY

[0005] Therefore, the present application provides a time step adjustment method, device, equipment and medium for VPI simulation to solve the problem that the calculation time step cannot be automatically adjusted according to the dynamic change of resin flow rate in existing CFD simulation.

[0006] In a first aspect, the present application provides a time step adjustment method for VPI simulation, the method comprising: obtaining a VPI simulation model and a target Knudsen number, wherein the VPI simulation model is provided with rheological properties of resin and boundary conditions; when the boundary conditions are single injection port based on constant pressure boundary, determining a first maximum flow rate of resin and a first minimum grid size at a current time step according to the VPI simulation model; and determining a next time step according to the first maximum flow rate, the first minimum grid size and the target Knudsen number.

[0007] In the embodiment, the time step is dynamically adjusted according to the actual flow rate of resin at different stages. A smaller time step is used when the resin flows at a high speed in the initial stage to ensure stability; and the time step is automatically enlarged in the low-speed stage to avoid redundant calculation, thereby significantly shortening the total simulation time and improving the simulation efficiency. Meanwhile, the Knudsen number constraint is considered when the time step is automatically adjusted, the numerical instability and calculation divergence caused by a fixed step size that is too large are avoided, a convergence judgment mechanism is added, and the calculation convergence is ensured when the speed suddenly changes or the front is unstable.

[0008] In an optional embodiment, the rheological properties of the resin are represented by a viscosity-temperature-time relationship, which is as follows:

[0009]

[0010] wherein, is the dynamic viscosity of the resin at an absolute temperature is a reference viscosity constant, is an apparent activation energy, is a universal gas constant, equal to , is an empirical factor varying with time.

[0011] In an optional embodiment, the rheological properties of the resin are represented by a viscosity-temperature-time-curing reaction conversion rate relationship, which is as follows:

[0012]

[0013] wherein, is the curing reaction conversion rate, is an empirical constant representing the degree of viscosity increase with conversion rate.

[0014] In the embodiment, the time step adaptive adjustment method is coupled with the epoxy resin curing kinetics model, and the empirical factor is automatically corrected according to the real-time evolution of the resin conversion rate ​So that the viscosity model is more consistent with the actual process, and the reliability of the simulation result is improved.

[0015] In an optional embodiment, when the boundary condition is based on a plurality of glue injection ports and an asymmetric boundary, the calculation domain of the VPI simulation model includes a plurality of sub-calculation domains corresponding to the plurality of glue injection ports, and the method further includes: determining, according to the VPI simulation model, a second maximum flow rate of the resin corresponding to each sub-calculation domain and a second minimum grid size at a current time step; determining a candidate time step corresponding to each sub-calculation domain according to the second maximum flow rate of the resin corresponding to each sub-calculation domain, the second minimum grid size corresponding to each sub-calculation domain, and a target Knudsen number; and determining the minimum value of the plurality of candidate time steps as a next time step.

[0016] In this embodiment, the zoning monitoring and candidate step aggregation strategy are adopted, the joint adjustment of the global and local time steps is realized when there is a speed difference in different glue injection paths, and the convergence and stability of the calculation under complex working conditions are ensured.

[0017] In an optional embodiment, the calculation domain of the VPI simulation model includes a narrow region and a normal region of the flow channel, the grid size of the narrow region of the flow channel is smaller than the grid size of the normal region, and before determining the first maximum flow rate of the resin and the first minimum grid size at the current time step, the method further includes: detecting the position of the resin front at the current time step; determining whether the resin front enters the narrow region of the flow channel according to the position of the resin front; and determining the first minimum grid size, including: if the resin front enters the narrow region of the flow channel, determining the grid size corresponding to the narrow region of the flow channel as the first minimum grid size; and if the resin front does not enter the narrow region of the flow channel, determining the grid size corresponding to the normal region as the first minimum grid size.

[0018] In this embodiment, the adaptive grid refinement is introduced in the resin flow front region, and is used in cooperation with the time step adaptive adjustment method, so that a higher spatial resolution is maintained in the key region, and the time step is dynamically adjusted, thereby improving the overall calculation efficiency while ensuring the accuracy.

[0019] In an optional embodiment, after determining the next time step, the method further includes: inputting the next time step into a display calculation module, and determining a simulation calculation result according to the output of the display calculation module, wherein the simulation calculation result includes at least one of a pressure field, a velocity field, and a filling rate distribution of the resin in the impregnation process, and a time step change curve.

[0020] In a second aspect, the present application provides a time step adjusting device for VPI simulation, the device comprising: an obtaining module configured to obtain a VPI simulation model and a target Reynolds number, wherein the VPI simulation model is provided with rheological properties of resin and boundary conditions; a parameter determining module configured to determine a first maximum flow rate of resin and a first minimum grid size at a current time step according to the VPI simulation model when the boundary conditions are single injection port based on constant pressure boundary; and a time step adjusting module configured to determine a next time step according to the first maximum flow rate, the first minimum grid size and the target Reynolds number.

[0021] In a third aspect, the present application provides a computer device, comprising: a memory and a processor, which are communicatively connected with each other, and the memory stores computer instructions; the processor executes the computer instructions to perform the time step adjusting method for VPI simulation according to the first aspect or any one of the corresponding embodiments thereof.

[0022] In a fourth aspect, the present application provides a computer readable storage medium, which stores computer instructions for causing a computer to perform the time step adjusting method for VPI simulation according to the first aspect or any one of the corresponding embodiments thereof.

[0023] In a fifth aspect, the present application provides a computer program product, which comprises computer instructions for causing a computer to perform the time step adjusting method for VPI simulation according to the first aspect or any one of the corresponding embodiments thereof. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the technical solutions in the related art, the drawings needed to be used in the specific embodiments or related art description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can obtain other drawings according to these drawings without creative labor.

[0025] Figure 1 is a flowchart of a time step adjusting method for VPI simulation according to an embodiment of the present application;

[0026] Figure 2 is a flowchart of another time step adjusting method for VPI simulation according to an embodiment of the present application;

[0027] Figure 3 is a flowchart of still another time step adjusting method for VPI simulation according to an embodiment of the present application;

[0028] Figure 4is a flowchart of another time step adjustment method of VPI simulation according to an embodiment of the present application;

[0029] Figure 5 is a structural block diagram of a time step adjustment method device of VPI simulation according to an embodiment of the present application;

[0030] Figure 6 is a hardware structure schematic diagram of a computer device according to an embodiment of the present application. DETAILED DESCRIPTION

[0031] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. All other embodiments obtained by those skilled in the art without creative work on the basis of the embodiments in the present application shall fall within the scope of the present application.

[0032] At present, in the CFD simulation of the VPI process of a superconducting magnet, an explicit calculation method is widely used to process multiphase flow and non-Newtonian fluid characteristics. However, in the time step control aspect, the related art mainly has the following schemes:

[0033] (1) Fixed time step method

[0034] Most CFD software uses a fixed time step for explicit calculation. In order to ensure the stability of the calculation in the initial high-speed flow stage of the resin, a very small time step is usually set to meet the convergence requirement of the Courant number. However, as the impregnation process advances, the flow rate gradually decreases, and at this time, the same very small time step is still used, resulting in a serious decrease in calculation efficiency and a doubling of calculation time.

[0035] (2) Artificially adjusting the time step in stages

[0036] In some engineering practices, a method of setting the time step in stages is used, that is, according to the estimated flow rate change, different time intervals are artificially divided in the simulation process, and different time steps are set for each interval. Although this method improves the calculation efficiency to some extent, it has obvious shortcomings: it needs to rely on experience or prior trial calculation to divide the stages, and lacks automation and universality; the flow rate change has complexity and uncertainty, and the stage boundaries set artificially often cannot accurately match the actual change of the flow field; the operation is tedious and difficult to adapt to large-scale calculation or rapid adjustment of different working conditions.

[0037] (3) Limitations of the self-adaptive grid method

[0038] Some CFD software supports adaptive mesh refinement or time integration method based on local flow field characteristics, but its focus is on the improvement of spatial resolution, not the dynamic adjustment of time step, which cannot solve the problem of time step adaptation under the constraint of Courant number.

[0039] In summary, the related art still has the following defects in time step control: ① unable to automatically adjust according to the real-time maximum resin flow rate and the Courant number constraint; ② low computational efficiency and numerical stability risk; ③ lack of unified time step adaptive adjustment strategy that can be directly embedded in the VPI simulation process.

[0040] Therefore, the present application provides a VPI simulation time step adjustment method, device, equipment and medium, which dynamically and adaptively adjusts the time step based on real-time monitoring of resin flow rate and combined with the Courant number constraint in VPI process simulation, thereby ensuring computational convergence and significantly improving simulation efficiency.

[0041] The VPI simulation time step adjustment method provided by the present application will be described in detail below with reference to the accompanying drawings. It should be noted that the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and although the logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0042] The VPI simulation time step adjustment method provided by the present embodiment can be used in mobile terminals such as electronic devices, servers or tablet computers, etc. Figure 1 The VPI simulation time step adjustment method provided by the present embodiment can be used in mobile terminals such as electronic devices, servers or tablet computers, etc. Figure 1 As shown in the flowchart of the VPI simulation time step adjustment method according to an embodiment of the present application, the flowchart includes the following steps:

[0043] Step S101, obtain a VPI simulation model and a target Courant number.

[0044] The VPI simulation model is provided with the rheological properties and boundary conditions of the resin, and is used to accurately simulate the whole process of the vacuum pressure impregnation (VPI) process of the superconducting magnet before physical experiments, so as to determine the pressure field, velocity field and filling rate distribution of the resin in the impregnation process, and optimize the process parameters of VPI (such as vacuum pressure, injection port arrangement position and number, etc.).

[0045] Specifically, a three-dimensional CFD simulation model can be established according to the geometric structure and process conditions of the superconducting magnet coil, and then the rheological properties and boundary conditions of the resin are defined in the three-dimensional CFD simulation model, and the three-dimensional CFD simulation model defining the rheological properties and boundary conditions of the resin is determined as the VPI simulation model.

[0046] For example, the resin is considered a non-Newtonian fluid, and its rheological properties are influenced by viscosity. With temperature With time The relationship between change and viscosity With temperature With time The relationship of change can be expressed using the Arrhenius model or empirical formula as shown in formula (1):

[0047]

[0048] in, For the resin at absolute temperature Dynamic viscosity at (unit: ), Reference viscosity constant (unit: ), Apparent activation energy (unit: J / mol). This is the universal gas constant, equal to 8.314 J / (mol*K). These are empirical factors that change over time.

[0049] In this embodiment, an empirical factor that varies with time is introduced into the three-dimensional CFD simulation model to characterize the time effect caused by the curing reaction. The time step update not only depends on the flow rate but also takes into account the degree of curing reaction, making the viscosity model more consistent with the actual process and improving the reliability of the simulation results.

[0050] It can be characterized by an exponential model as shown in formula (2), a conversion rate model as shown in formula (3), or a double exponential model as shown in formula (4).

[0051]

[0052] in, This is the time factor constant (unit: 1 / s). The conversion rate of the curing reaction is dimensionless, 0 to 1. , is the reaction rate constant (unit: 1 / s); It is an empirical index, dimensionless; and These are dimensionless empirical coefficients; and This is the time constant (unit: 1 / s).

[0053] The boundary condition can be a single injection port based on a constant pressure boundary. Specifically, a constant pressure inlet boundary condition is set at the injection port, with a pressure value... (unit: Pa); the vacuum pressure boundary condition is set at the outlet, and the pressure value (unit: Pa); the rest of the boundary is set as a solid wall condition, which meets the no-slip boundary assumption.

[0054] The Courant number is the core constraint for showing the stability of the algorithm, and the Courant number can be represented by formula (5) as follows:

[0055]

[0056] Wherein, is the Courant number (dimensionless); is the characteristic velocity of the flow field, and the maximum velocity (unit: m / s) is taken; is the time step (unit: s); is the minimum characteristic length of the calculation unit (unit: m), and the minimum characteristic length of the calculation unit can be the grid size of the calculation domain.

[0057] In order to ensure numerical stability, the Courant number needs to satisfy , wherein, is the critical Courant number, generally 0.2-0.5 (dimensionless). The target Courant number can be configured by the designer, and it is ensured to meet this constraint condition.

[0058] Step S102, when the boundary condition is a single glue injection port based on a constant pressure boundary, according to the VPI simulation model, the first maximum flow rate of the resin and the first minimum grid size at the current time step are determined.

[0059] Specifically, based on the constant pressure boundary, the fluid motion equation in the VPI impregnation process of the superconducting magnet is solved by the explicit calculation module of the VPI simulation model, and the flow rate value of all grid units (or grid nodes) at the current time step can be obtained, including the speed size and direction. The maximum value of all flow rates in the current flow rate field is the first maximum flow rate , and the characteristic size of each unit is extracted by traversing all grid units in the calculation domain, and the minimum value of all grid characteristic sizes is the first minimum grid size.

[0060] It should be noted that when the current time step is the first time step, the current time step is a set value determined by the designer according to experience.

[0061] Step S103, according to the first maximum flow rate, the first minimum grid size and the target Courant number, the next time step is determined.

[0062] Specifically, according to the first maximum flow rate, the first minimum grid size and the target Courant number, the next time step can be determined by the following formula (6):

[0063]

[0064] wherein, is the self-adaptively adjusted time step (unit: s), i.e. the next time step; is the set target Courant number, usually taking 0.2-0.3; is the minimum grid size (unit: m); is the maximum flow rate of the current calculation step (unit: m / s).

[0065] When is larger, is automatically reduced to ensure stability; when is smaller, is automatically increased to improve the calculation efficiency. Specifically, after obtaining the next time step, the next time step is input into the explicit solver (display calculation module) as the current time step, the simulation calculation result is determined according to the output of the display calculation module, and then the next step calculation is continued, and steps S102 and S103 are repeated until the impregnation process is completed. The simulation calculation result includes at least one of the pressure field, the velocity field and the filling rate distribution of the resin in the impregnation process, and the time step change curve.

[0066] In this embodiment, the time step is dynamically adjusted through the actual flow rate of the resin at different stages. A smaller time step is used when the resin flows at a high speed in the initial stage to ensure stability; the time step is automatically enlarged in the low-speed stage to avoid redundant calculation, thereby significantly shortening the total simulation time and improving the simulation efficiency. At the same time, the Courant number constraint is also considered when the time step is automatically adjusted, avoiding numerical instability and calculation divergence caused by a fixed step that is too large, increasing the convergence judgment mechanism, and ensuring that the calculation converges when the speed suddenly changes or the front is unstable.

[0067] The present application can be realized through user-defined functions (UDF), scripts or macros on different CFD software platforms (such as Fluent, STAR-CCM+), and does not depend on specific solvers. In addition to the VPI process of superconducting magnets, the present application can also be extended to other explicit calculation scenarios involving non-Newtonian fluids, multiphase flow and solidification reactions.

[0068] In the actual VPI process, the viscosity of the resin is not only related to the temperature and flow conditions, but also gradually increases with the progress of the solidification reaction (cross-linking / polycondensation). If the solidification effect is ignored, the viscosity growth rate may be underestimated, thereby affecting the flow rate prediction and reasonable adjustment of the time step.

[0069] Therefore, in some embodiments, a resin curing kinetics model is introduced on the basis of adaptive adjustment of time step, so that the time step update depends not only on the flow rate, but also on the curing reaction degree.

[0070] The resin curing kinetics model can be characterized by a first-order kinetics model as shown in equation (7):

[0071]

[0072] wherein, is the degree of curing; is the reaction order; is the temperature (unit: K); is the rate constant, which satisfies the Arrhenius relationship: .

[0073] At this time, the conversion rate is associated with the resin viscosity, that is, the rheological properties of the resin are characterized by the viscosity change with temperature, time and curing reaction conversion rate, which can be shown as equation (8):

[0074]

[0075] wherein, is the curing reaction conversion rate, is an empirical constant, which represents the degree of viscosity increase with conversion rate.

[0076] In the present embodiment, as the curing reaction proceeds, the viscosity increases rapidly, the resin flow rate decreases, and the time step is reduced, allowing a larger time step. Coupling the time step adaptive adjustment method with the epoxy resin curing kinetics model, the empirical factor is automatically corrected according to the real-time evolution of the resin conversion rate , so that the viscosity model is more consistent with the actual process, and the reliability of the simulation results is improved.

[0077] In the VPI process, if there is only one glue injection port and symmetrical boundary, the time step only needs to be determined according to the global maximum speed and the minimum grid size. However, in the case of multiple glue injection ports and asymmetric outlet distribution, the flow of resin in different regions is very different, for example, high-speed flow may occur near some glue injection ports, and the speed in some regions may be close to zero, and the front interface region (resin-air interface) is most sensitive to calculation stability.

[0078] When the boundary condition is based on multiple glue injection ports and asymmetric boundary, as shown in Figure 2 , the time step adjustment method of VPI simulation includes the following steps:

[0079] Step S201, obtaining a VPI simulation model and a target Rayleigh number.

[0080] For details, please refer to Figure 1 Step S101 of the embodiment shown is not described here.

[0081] Step S202, determining the second maximum flow rate of resin corresponding to each sub-computing domain and the second minimum grid size at the current time step according to the VPI simulation model.

[0082] Wherein, when the boundary condition is based on multiple glue injection ports and asymmetric boundaries, the computing domain of the VPI simulation model includes multiple sub-computing domains corresponding to the multiple glue injection ports, and a monitoring area (sub-computing domain) is defined near each glue injection port to track the high-speed flow of resin just after injection; the resin front area (interface zone) is separately defined as a monitoring area to prevent interface instability; the remaining areas that have not been filled or flow slowly are not the focus of control.

[0083] Specifically, by solving the fluid motion equation in the VPI impregnation process of the superconducting magnet through the explicit calculation module of the VPI simulation model, the flow rate values of all grid cells (or grid nodes) at the current time step can be obtained. Then, the maximum flow rate (denoted as the second maximum flow rate) of the region is extracted in each monitoring area, and the minimum grid size (denoted as the second minimum grid size) of the region is extracted.

[0084] Step S203, determining the candidate time step corresponding to each sub-computing domain according to the second maximum flow rate of resin corresponding to each sub-computing domain, the second minimum grid size corresponding to each sub-computing domain, and the target Rayleigh number.

[0085] Specifically, the candidate time step corresponding to each sub-computing region can be determined by the following formula (9):

[0086]

[0087] Wherein, denotes the candidate time step corresponding to the sub-computing region, denotes the second minimum grid size corresponding to the sub-computing domain, denotes the second maximum flow rate of resin corresponding to the sub-computing domain.

[0088] Step S204, determining the minimum value of the multiple candidate time steps as the next time step.

[0089] Specifically, after obtaining the multiple candidate time steps, compare the candidate time steps of all regions and take the minimum value as the next time step, that is, .

[0090] After the end of each step calculation, the velocity and grid information of each region are re-extracted, and steps S202 to S202 are repeated to continuously update the time step of the next step.

[0091] In this embodiment, the zoning monitoring and candidate step aggregation strategy is adopted, when there is a speed difference in different glue injection paths, the global and local time steps are jointly adjusted to ensure the convergence and stability of the calculation under complex working conditions.

[0092] In the VPI process, the details of resin flow and front interface often determine the accuracy of the calculation result. In order to capture the interface dynamics and local complex flow, it is usually necessary to use smaller grids in narrow areas of the flow channel. However, local grid refinement will lead to a large global minimum cell size Significant reduction, so that the time step based on the Courant-Friedrichs-Lewy (CFL for short) constraint is also reduced, resulting in reduced overall calculation efficiency.

[0093] Therefore, the calculation domain of the VPI simulation model includes a narrow area of the flow channel and a normal area, the grid size of the narrow area of the flow channel is smaller than the grid size of the normal area, before the step S102, the VPI simulation time step adjustment method further includes: Figure 3 As shown in the figure, the VPI simulation time step adjustment method further includes:

[0094] Step S301, detecting the position of the resin front at the current time step.

[0095] Step S302, determining whether the resin front enters the narrow area of the flow channel according to the position of the resin front.

[0096] At this time, the step of determining the first minimum grid size includes:

[0097] Step S303, if the resin front enters the narrow area of the flow channel, the grid size corresponding to the narrow area of the flow channel is determined as the first minimum grid size.

[0098] Step S304, if the resin front does not enter the narrow area of the flow channel, the grid size corresponding to the normal area is determined as the first minimum grid size.

[0099] Specifically, in this embodiment, the Adaptive Mesh Refinement (AMR) function is enabled in the calculation domain of the VPI simulation model, the narrow area of the flow channel is locally refined, and the normal area (the area in the calculation domain except the narrow area of the flow channel) maintains a relatively coarse grid to control the total number of cells.

[0100] At each time step, the position of the resin front is detected from the VPI simulation model, the coordinates of the flow front position are extracted, and it is determined whether the resin front enters the encryption area (i.e. the narrow area of the flow channel). If the front enters the encryption area, the grid size of the encryption area is taken as the minimum grid size; if the front is still in the normal area, the grid size of the normal area is taken as the minimum grid size.

[0101] In the present embodiment, adaptive grid encryption is introduced in the resin flow front area, which is used in cooperation with the adaptive time step adjustment method, so that in the key area, both a higher spatial resolution and a dynamic adjustment of the time step are maintained, thereby improving the overall calculation efficiency while ensuring accuracy.

[0102] In an embodiment, the time step adjustment method of VPI simulation is combined with parallel computing architecture to further shorten the calculation time through multi-core parallel or GPU acceleration under the premise of ensuring the Courant number constraint, thereby realizing fast simulation of large-scale superconducting magnet VPI process.

[0103] In an embodiment, the time step adjustment method of VPI simulation is introduced in the simulation process to correct the calculation parameters by experimental monitoring data (such as real-time pressure and flow data), so that the time step adaptive adjustment method is not limited to numerical simulation, but also realizes the dynamic coupling and verification of experiment-simulation.

[0104] In another embodiment, referring to Figure 4 , another time step adjustment method for VPI simulation is provided, comprising the following steps:

[0105] Step 1: Establishing geometric and physical models

[0106] The models include: coils, insulation layers, flow channels / porous domains, etc.

[0107] Step 2: Defining fluid properties and solidification models

[0108] The viscosity of the resin changes with temperature, time and solidification conversion rate.

[0109] Step 3: Setting boundaries and working conditions

[0110] Setting single / multiple injection port pressure, outlet vacuum degree, wall conditions, etc.

[0111] Step 4: Grid division and encryption strategy

[0112] The narrow area of the flow channel is refined, and the remaining area is coarsened.

[0113] Step 5: Initialize time step

[0114] A conservative first time step is given.

[0115] Step 6: Perform a calculation step

[0116] Give a conservative first step time step.

[0117] Step 7: Extract monitoring data

[0118] Extract the maximum speed, front position, and minimum grid size.

[0119] Step 8: Determine whether it is a multi-nozzle asymmetric boundary condition

[0120] If so, calculate the candidate step size in each partition, take the most stringent constraint in each nozzle / partition unit; if not, calculate the candidate step size in single nozzle condition, and use the global maximum speed and effective grid constraint.

[0121] Step 9: Determine whether the flow front enters the encryption area

[0122] If so, update the time step based on the grid size of the encryption area to ensure the stability of the front calculation; if not, update the time step based on the grid size of the normal area to improve the overall efficiency.

[0123] Step 10: Stability and step size smoothing check

[0124] Determine whether the residual is large or divergent, if so, reduce the time step, reiterate, and return to step 5; if not, go to the next step.

[0125] Add a convergence judgment mechanism in the time step update to effectively prevent numerical oscillation or divergence.

[0126] Step 11: Termination condition judgment

[0127] Whether the total calculation time set is reached, if so, go to the next step; if not, continue to calculate the next time step and return to step 6.

[0128] Step 12, result output

[0129] Output the simulation calculation results: pressure field, velocity field and filling rate distribution of resin in the impregnation process; dynamic adjustment of time step change curve; overall calculation efficiency and stability comparison results.

[0130] The time step adjustment method of VPI simulation provided by the embodiment has the following advantages:

[0131] (1) The calculation efficiency is significantly improved

[0132] The present application can dynamically adjust the time step according to the actual flow rate of the resin at different stages. A smaller time step is used to ensure stability when the resin flows at high speed in the initial stage; the time step is automatically enlarged in the low-speed stage to avoid redundant calculation, thereby significantly shortening the total simulation time.

[0133] (2) Numerical stability enhancement

[0134] The time step is automatically adjusted based on the Courant number constraint throughout the whole process, avoiding numerical instability and calculation divergence caused by excessively large fixed step size. A convergence judgment mechanism is added to ensure convergence of the calculation when the speed suddenly changes or the front is unstable.

[0135] (3) Strong adaptability to complex working conditions

[0136] For multiple glue injection ports and asymmetric boundary conditions, the application adopts a zoning monitoring and candidate step aggregation strategy, which can still ensure global convergence when the flow rates in different regions differ greatly. It supports various VPI working conditions such as single glue injection, multiple glue injection, and asymmetric arrangement.

[0137] (4) Coordination with spatial adaptive technology

[0138] The method of the application is combined with adaptive mesh refinement (AMR), and only when the front enters the fine mesh region is the fine mesh constraint time step used, and the rest of the stage is still controlled according to the ordinary mesh, avoiding the efficiency decline caused by the global minimum mesh.

[0139] (5) Higher process authenticity

[0140] The viscosity model introduces resin curing kinetics feedback, so that the time step adjustment not only depends on the flow rate, but also automatically relaxes with the increase of curing reaction viscosity, making the simulation more consistent with the actual process.

[0141] (6) Scalability and versatility

[0142] The method can be implemented on different CFD software platforms (such as Fluent, STAR-CCM+) through user-defined functions (UDF), scripts or macros, and does not depend on specific solvers. In addition to superconducting magnet VPI processes, this method can also be extended to other explicit calculation scenarios involving non-Newtonian fluids, multiphase flow and curing reactions.

[0143] In this embodiment, a VPI simulation time step adjustment device is also provided, which is used to implement the above-mentioned embodiments and preferred embodiments, and will not be described again. As used below, the term "module" can be a combination of software and / or hardware that implements a predetermined function. Although the device described in the following embodiments is preferably implemented in software, hardware, or a combination of software and hardware implementation is also possible and contemplated.

[0144] The present embodiment provides a VPI simulation time step adjustment device, as shown in Figure 5 , comprising:

[0145] The acquisition module 501 is used to acquire the VPI simulation model and the target Kullmann number, wherein the VPI simulation model is set with the rheological properties and boundary conditions of the resin;

[0146] The parameter determination module 502 is used to determine the first maximum flow rate and the first minimum mesh size of the resin at the current time step, based on the VPI simulation model, when the boundary condition is a single injection nozzle based on a constant pressure boundary.

[0147] The time step adjustment module 503 is used to determine the next time step based on the first maximum flow rate, the first minimum grid size, and the target Courant number.

[0148] Further functional descriptions of the above modules and units are the same as those in the corresponding embodiments described above, and will not be repeated here.

[0149] In this embodiment, the vacuum pressure impregnation process optimization device is presented in the form of a functional unit. Here, a unit refers to an application-specific integrated circuit (ASIC), a processor and memory that execute one or more software or fixed programs, and / or other devices that can provide the above functions.

[0150] This invention also provides a computer device, such as... Figure 6 As shown, the computer device includes one or more processors 610, memory 620, and interfaces for connecting the components, including high-speed interfaces and low-speed interfaces. The components communicate with each other via different buses and can be mounted on a common motherboard or otherwise installed as needed. The processors can process instructions executed within the computer device, including instructions stored in or on memory to display graphical information of a GUI on external input / output devices (such as display devices coupled to the interfaces). In some alternative implementations, multiple processors and / or multiple buses can be used with multiple memories and multiple memory modules, if desired. Similarly, multiple computer devices can be connected, each providing some of the necessary operations (e.g., as a server array, a group of blade servers, or a multiprocessor system). Figure 4 Take the 610 processor as an example.

[0151] The processor 610 may be a central processing unit, a network processor, or a combination thereof. The processor 610 may further include a hardware chip. The hardware chip may be an application-specific integrated circuit (ASIC), a programmable logic device (PLD), or a combination thereof. The programmable logic device may be a complex programmable logic device (CAMP), a field-programmable gate array (FPGA), a general-purpose array logic (GDA), or any combination thereof.

[0152] The memory 620 stores instructions executable by the at least one processor 610 for causing the at least one processor 610 to perform the methods illustrated by the above embodiments.

[0153] The memory 620 can include a program storage area and a data storage area. The program storage area can store an operating system, application programs, etc. required by at least one function. The data storage area can store data created by the computer device, etc. In addition, the memory 620 can include a high-speed random access memory, and can also include a non-transitory memory, such as at least one disk storage device, a flash memory device, or other non-transitory solid-state storage device. In some alternative embodiments, the memory 620 can optionally include a memory disposed remotely from the processor 610, which can be connected to the computer device through a network. Examples of the network include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and a combination thereof.

[0154] The memory 620 can include a volatile memory, such as a random access memory, and can also include a non-volatile memory, such as a flash memory, a hard disk, or a solid-state disk, and can also include a combination of the above-mentioned kinds of memories.

[0155] The computer device further includes a communication interface 630 for enabling the computer device to communicate with other devices or communication networks.

[0156] The embodiments of the present application also provide a computer readable storage medium. The above-mentioned methods according to the embodiments of the present application can be implemented in hardware, firmware, or recorded in a storage medium, or stored in a remote storage medium or a non-transitory machine readable storage medium and downloaded to a local storage medium through network downloading of computer code, so that the methods described herein can be processed by such software on a storage medium using a general purpose computer, a special purpose processor, or programmable or special purpose hardware. The storage medium can be a magnetic disk, an optical disk, a read-only memory, a random access memory, a flash memory, a hard disk, or a solid-state disk, etc. Further, the storage medium can also include a combination of the above-mentioned kinds of memories. It can be understood that the computer, the processor, the microprocessor controller, or the programmable hardware includes a storage component that can store or receive software or computer code, which, when accessed and executed by the computer, the processor, or the hardware, implements the methods illustrated by the above embodiments.

[0157] Part of the present application can be applied as a computer program product, for example, computer program instructions, when executed by a computer, through the operation of the computer, can invoke or provide the method and / or technical solutions according to the present application. Those skilled in the art should understand that the form of computer program instructions in computer readable medium includes but is not limited to source file, executable file, installation package file and the like, and accordingly, the way of computer program instructions executed by computer includes but is not limited to: the computer directly executes the instructions, or the computer executes the corresponding compiled program after compiling the instructions, or the computer reads and executes the instructions, or the computer reads and installs the instructions and then executes the corresponding installed program. Here, the computer readable medium can be any available computer readable storage medium or communication medium accessible to the computer.

[0158] In the description of the present application, the description of the terms "the embodiment", "one embodiment", "some embodiments", "example", "specific example" or "some examples" means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present application, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any suitable manner in any one or more embodiments or examples. In addition, the skilled in the art can combine and combine the different embodiments or examples described in the present application and the features of different embodiments or examples without contradiction.

[0159] In addition, the terms "first", "second" are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Therefore, the features defined with "first", "second" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "a plurality of" is at least two, for example, two, three, etc., unless otherwise specifically limited.

[0160] Although the embodiments of the present application are described in conjunction with the drawings, various modifications and variations can be made by those skilled in the art without departing from the spirit and scope of the present application, and such modifications and variations fall within the scope defined by the present application.

Claims

1. A method for adjusting the time step in VPI simulation, characterized in that, The method includes: Obtain the VPI simulation model and the target Coulomb number. The VPI simulation model sets the rheological properties of the resin and boundary conditions. The rheological properties of the resin are characterized by the relationship between viscosity and temperature, time, and curing reaction conversion rate. The relationship between viscosity and temperature, time, and curing reaction conversion rate is shown below: For the resin at absolute temperature The dynamic viscosity below, For reference viscosity constant, As the apparent activation energy, The universal gas constant is equal to , The conversion rate of the curing reaction. It is an empirical constant that characterizes the degree to which viscosity increases with conversion rate; When the boundary condition is a single injection nozzle based on a constant pressure boundary, the first maximum flow rate and the first minimum mesh size of the resin at the current time step are determined according to the VPI simulation model. The next time step is determined based on the first maximum flow velocity, the first minimum grid size, and the target Courant number; The next time step is used as the current time step and input to the display calculation module. The simulation calculation result is determined based on the output of the display calculation module. The steps of determining the first maximum flow rate and the first minimum grid size of the resin at the current time step are returned until the superconducting magnet completes the impregnation process. The simulation calculation result includes at least one of the following: pressure field, velocity field and filling rate distribution of the resin during the impregnation process, and time step change curve.

2. The method according to claim 1, characterized in that, When the boundary conditions are based on multiple injection ports and asymmetric boundaries, the computational domain of the VPI simulation model includes multiple sub-computational domains corresponding one-to-one with the multiple injection ports. The method further includes: Based on the VPI simulation model, determine the second maximum flow rate and the second minimum mesh size of the resin corresponding to each sub-computation domain at the current time step; Based on the second maximum flow rate of the resin corresponding to each sub-computation domain, the second minimum grid size corresponding to each sub-computation domain, and the target Courr number, determine the candidate time step corresponding to each sub-computation domain; The minimum value among the multiple candidate time steps is determined as the next time step.

3. The method according to claim 1, characterized in that, The computational domain of the VPI simulation model includes a narrow flow channel region and a normal flow channel region. The mesh size of the narrow flow channel region is smaller than that of the normal flow channel region. Before determining the first maximum flow velocity and the first minimum mesh size of the resin at the current time step, the method further includes: Detect the position of the resin front at the current time step; Based on the position of the resin front, determine whether the resin front has entered a narrow region of the flow channel; Determining the first minimum grid size includes: If the resin front enters the narrow region of the flow channel, the grid size corresponding to the narrow region of the flow channel is determined as the first minimum grid size; If the resin front does not enter the narrow flow channel region, the grid size corresponding to the normal region is determined as the first minimum grid size.

4. A time step adjustment device for VPI simulation, characterized in that, The device includes: The acquisition module is used to acquire the VPI simulation model and the target Coulomb number. The VPI simulation model includes the rheological properties and boundary conditions of the resin. The rheological properties of the resin are characterized by the relationship between viscosity and temperature, time, and curing reaction conversion rate, as shown below: For the resin at absolute temperature The dynamic viscosity below, For reference viscosity constant, As the apparent activation energy, The universal gas constant is equal to , The conversion rate of the curing reaction. It is an empirical constant that characterizes the degree to which viscosity increases with conversion rate; The parameter determination module is used to determine the first maximum flow rate and the first minimum grid size of the resin at the current time step, based on the VPI simulation model, when the boundary condition is a single injection nozzle based on a constant pressure boundary. The time step adjustment module is used to determine the next time step based on the first maximum flow rate, the first minimum grid size, and the target Coulomb number, and to input the next time step as the current time step into the display calculation module, determine the simulation calculation result based on the output of the display calculation module, and return to the steps of determining the first maximum flow rate and the first minimum grid size of the resin at the current time step, until the superconducting magnet completes the impregnation process. The simulation calculation result includes at least one of the following: pressure field, velocity field and filling rate distribution of the resin during the impregnation process, and time step change curve.

5. A computer device, characterized in that, include: A memory and a processor are communicatively connected, the memory stores computer instructions, and the processor executes the computer instructions to perform the time step adjustment method for VPI simulation according to any one of claims 1 to 3.

6. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer instructions for causing the computer to execute the time step adjustment method for VPI simulation according to any one of claims 1 to 3.

7. A computer program product, characterized in that, Includes computer instructions for causing a computer to execute the time step adjustment method for VPI simulation as described in any one of claims 1 to 3.

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