Parallel fluid-structure interaction method for thermal-hydraulic simulation of reactor fuel bundle

Abstract

The application relates to a fluid-solid coupling parallel method for reactor fuel rod bundle thermal-hydraulic simulation. The method comprises the following steps: dividing a whole calculation domain into different lattices according to the spatial positions of fuel rods of a reactor, assigning each lattice to a single calculation core, and respectively loading a solid domain grid and a fluid domain grid and initializing variable fields; calling a solid solver to solve a solid heat transfer model on the solid domain grid; judging the heat flux and the solid temperature in the solid heat transfer model, and transferring the heat flux to the fluid domain grid according to the judgment result; calling a fluid solver to calculate the flux at a wound interface of the fluid domain, and calculating the velocity, the pressure and the temperature on a grid unit at the wound interface of the fluid domain according to the flux; and judging the convergence of the velocity, the pressure and the temperature, and if the convergence is achieved, the temperature is sent to the fluid domain grid through a fluid-solid interface. The method can improve the parallel calculation efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of simulation, in particular to a fluid-structure coupling parallel method for thermal-hydraulic simulation of reactor fuel rod bundles. BACKGROUND

[0002] In recent years, with the rapid development of computer technology and high-performance computing, the thermal-hydraulic analysis of reactors based on the fine computational fluid dynamics (CFD) method and engineering application software technology has been widely studied and applied. As one of the key technologies of numerical reactors, full-core large-scale numerical simulation has attracted great attention. Realizing high-fidelity full-core numerical simulation requires considering the coupling between different physical fields, which puts higher requirements on current numerical methods and software technology.

[0003] Currently, the thermal-hydraulic analysis of nuclear reactors still mainly uses mainstream commercial software such as CFX, FLUENT, STAR-CCM+, etc. However, the cost of realizing large-scale multi-physical field coupling based on commercial software for customized scenarios is very high, high-performance computing resources cannot be efficiently utilized, and the needs of nuclear reactor engineering design cannot be fully met. YH-ACT (Parallel Analysis Code of Thermohydraulics) is a special independent software for local fine thermal-hydraulic analysis, which has comprehensive physical models, high calculation accuracy and good parallel computing efficiency. At the same time, it adopts an object-oriented highly scalable software architecture, which can carry out algorithm design and model development for the multi-physical field coupling simulation needs of specific application scenarios, and has strong flexibility. Due to the closed nature of commercial software, most of the fluid-structure coupling heat transfer simulations of reactor fuel rod bundles use a separate coupling scheme, i.e. fluid domain calculation and solid domain calculation are completed by different software respectively, and data communication is realized through coupling software. The defect of this coupling scheme is that the parallel scale is limited, and the fluid domain and the solid domain need to be parallelly divided respectively, one solid domain core often needs to correspond to multiple fluid domain cores, resulting in frequent fluid-structure data exchange which needs to be realized through communication between computing cores, affecting the parallel efficiency. SUMMARY

[0004] Therefore, it is necessary to provide a fluid-structure coupling parallel method for thermal-hydraulic simulation of reactor fuel rod bundles, which can improve the parallel computing efficiency.

[0005] A fluid-structure coupling parallel method for thermal-hydraulic simulation of reactor fuel rod bundles, the method comprising:

[0006] The whole calculation domain is divided into different lattices according to the spatial positions of the fuel rods of the reactor, each lattice contains a complete fuel rod, and each lattice is assigned to a single calculation core, and the solid domain grid and the fluid domain grid are loaded and the variable field is initialized for each calculation core; the variable field includes temperature, velocity and pressure;

[0007] The solid solver is called to solve the solid heat transfer model on the solid domain grid; the heat flux and the solid temperature in the solid heat transfer model are judged, and the heat flux is transmitted to the fluid domain grid according to the judgment result;

[0008] The fluid solver is called to calculate the flux at the wound interface of the fluid domain, the velocity, pressure and temperature on the grid cell at the wound interface of the fluid domain are calculated according to the flux, and the velocity, pressure and temperature are sent to the neighbor calculation core, and the variable field on the grid cell on the other side of the wound interface is received from the neighbor calculation core;

[0009] The convergence of the velocity, pressure and temperature is judged, and if the convergence is reached, the temperature is sent to the fluid domain grid through the fluid-solid interface.

[0010] In one of the embodiments, the solid heat transfer model is solved on the solid domain grid, including:

[0011] The solid heat transfer model is solved on the solid domain grid as

[0012]

[0013] Wherein, q is the heat flux, T s is the solid temperature, λ s is the thermal conductivity of the solid, and Q v is the heat source.

[0014] In one of the embodiments, the heat flux and the solid temperature in the solid heat transfer model are judged, and the heat flux is transmitted to the fluid domain grid according to the judgment result, including:

[0015] The heat flux and the solid temperature in the solid heat transfer model are judged, and it is judged whether the heat flux and the solid temperature reach the convergence precision, if not, the solid heat transfer model is solved on the solid domain grid; if the convergence is reached, the heat flux is transmitted to the fluid domain grid through the fluid-solid interface.

[0016] In one of the embodiments, the flux at the wound interface of the fluid domain is calculated, including:

[0017] The flux at the wound interface of the fluid domain is calculated as

[0018]

[0019] Wherein, is the mass flow, μ f is the diffusion term coefficient, E f and T f are the face vectors S f are the non-orthogonal correction of two components, E f is the modulus of E f ; φ is the variable to be solved, d CF is the vector of the connection between the calculation unit and the neighbor centroid, d CF is the modulus of it, V C is the volume of the current calculation unit, ρ C is the density, Δt represents the time step, represents the density of the last time step, represents the value of the current discrete unit variable of the last time step, S b represents the equation source term, FluxC f represents the flux of the current discrete unit affected by the calculation of the convection term and the diffusion term, FluxF f represents the flux of the neighbor unit of the current discrete unit affected by the calculation of the convection term and the diffusion term, FluxV f represents the flux of the matrix source term affected by the calculation of the convection term and the diffusion term, FluxC C represents the flux of the current discrete unit affected by the calculation of the transient term, FluxV C represents the flux of the matrix source term affected by the calculation of the transient term and the source term.

[0020] In one of the embodiments, the velocity, pressure and temperature on the grid cell at the wound interface of the fluid domain are calculated according to the flux, including:

[0021] The expression of the velocity, pressure and temperature on the grid cell at the wound interface of the fluid domain is sequentially solved according to the flux, and is

[0022]

[0023] wherein,

[0024]

[0025] represents the coefficient of the current discrete unit, represents the coefficient of the neighbor unit of the current discrete unit, represents the matrix source term, φ C represents the solving variable of the current discrete unit, and the variable includes velocity, pressure and temperature, φ F represents the solving variable of the neighbor unit of the current discrete unit, F represents the neighbor, and NB(C) represents the number of neighbors.

[0026] The aforementioned parallel fluid-structure interaction method for thermal-hydraulic simulation of reactor fuel rod bundles divides the overall computational domain into different grids based on the spatial location of the fuel rods. Each grid contains a complete fuel rod, and each grid is assigned to a separate computational core. For each computational core, both solid-domain and fluid-domain grids are loaded and variable fields are initialized. By performing parallel partitioning according to the spatial location of the fuel rod bundle, data communication between the fluid and solid domains is completed within the grid, avoiding data communication between computational cores and improving parallel simulation efficiency. This provides an effective solution for large-scale coupled numerical simulation research of fuel assemblies. Then, a solid-state solver is invoked to solve the solid heat transfer model on the solid-state grid. In the volumetric heat transfer model, heat flux density and solid temperature are used for evaluation. Based on the evaluation result, the heat flux density is transferred to the fluid domain mesh. The fluid solver is called to calculate the flux at the fluid domain wound interface. Based on the flux, the velocity, pressure, and temperature on the mesh cells at the fluid domain wound interface are calculated and sent to the neighboring computational cores. The variable field on the mesh cells on the other side of the wound interface is received from the neighboring computational cores. The convergence of velocity, pressure, and temperature is evaluated. If convergence is achieved, the temperature is sent to the fluid domain mesh through the fluid-solid interface. The coupling heat transfer effect between fluid and solid is considered throughout the simulation process. Compared with traditional large-scale simulations that only perform fluid domain calculations, the calculation of the solid domain is realized, which improves the accuracy of the whole domain simulation. Attached Figure Description

[0027] Figure 1 This is a flowchart illustrating a parallel fluid-structure interaction method for thermal-hydraulic simulation of reactor fuel rod bundles, as an example.

[0028] Figure 2 This is a schematic diagram of the framework of a fluid-structure interaction parallel method in one embodiment;

[0029] Figure 3 This is a schematic diagram of the computational domain z-direction for 1156 fuel rod bundles in one embodiment;

[0030] Figure 4 This is a schematic diagram of the 10*10 fuel rod bundle mesh division in another embodiment. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0032] In one embodiment, such as Figure 1 He Ru Figure 2As shown, a fluid-structure coupling parallel method for reactor fuel rod bundle thermal-hydraulic simulation is provided, comprising the following steps:

[0033] Step 102, according to the spatial position of the fuel rods of the reactor, the whole calculation domain is divided into different lattices, each lattice contains a complete fuel rod, and each lattice is assigned to a single calculation core, and the solid domain grid and the fluid domain grid are loaded respectively for each calculation core and the variable field is initialized; the variable field includes temperature, velocity and pressure.

[0034] As shown in Figure 3 , it is a schematic diagram of the z-direction of the calculation domain of 1156 fuel rod bundles, and the grid size is 110 million. Query the configuration file to get the total parallel degree nP, and the division number xP, yP, zP in the x, y, z directions. If nP≠xP*yP*zP, exit; otherwise, divide the whole calculation domain into xP*yP*zP lattices, each lattice contains a complete fuel rod, and each lattice is assigned to a single calculation core. As shown in Figure 4 , it is a schematic diagram of the grid division of a 10*10 fuel rod bundle. The interface between adjacent lattices is called a wound interface. For each calculation core, load the solid domain and the fluid domain respectively, and initialize the temperature, velocity, pressure and other variable fields, and solve the calculation according to steps 104-108.

[0035] Step 104, call the solid solver to solve the solid heat transfer model on the solid domain grid; judge the heat flux and the solid temperature in the solid heat transfer model, and transfer the heat flux to the fluid domain grid according to the judgment result.

[0036] Call the solid solver interface to solve the solid heat transfer model on the solid domain grid:

[0037]

[0038] In the formula, q is the heat flux, T s is the solid temperature, λ s is the thermal conductivity of the solid, and Q v is the heat source.

[0039] Judge whether q, T s reaches the convergence accuracy, if not, continue to call the solid solver to solve the solid heat transfer model on the solid domain grid; if it converges, the heat flux q is transferred to the fluid domain through the fluid-structure interface.

[0040] Step 106, call the fluid solver to calculate the flux at the wound interface of the fluid domain, calculate the velocity, pressure and temperature on the grid cell at the wound interface of the fluid domain according to the flux, and send the velocity, pressure and temperature to the neighbor computing core, and receive the variable field on the grid cell on the other side of the wound interface from the neighbor computing core.

[0041] Start the fluid solver, send the velocity, pressure, temperature on the grid cell at the wound interface of the fluid domain to the neighbor computing core, and receive the velocity, pressure, temperature and other variable fields on the grid cell on the other side of the wound interface from the neighbor computing core. The flux at the wound interface is calculated by the following formula:

[0042]

[0043] Where, is the mass flow; μ f is the diffusion term coefficient; E f and T f are the face vector S f Two non-orthogonal modified components, E f is the module of E f ; φ is the variable to be solved; d CF is the vector connecting the calculation cell and the neighbor centroid, d CF is the module of it; V C is the volume of the current calculation cell; ρ is the density;

[0044] Solve velocity, pressure and temperature in turn according to the following formula:

[0045]

[0046] Where,

[0047]

[0048] Step 108, convergence judgment is performed on the velocity, pressure and temperature, if the convergence, the temperature is sent to the fluid domain grid through the fluid-solid interface.

[0049] Determine whether the velocity, pressure and temperature reach the convergence precision, if not converged, continue to solve the velocity, pressure and temperature; if converged, the temperature is transmitted to the fluid domain through the fluid-solid interface. And determine whether the preset solving step number is reached, if not reached, jump to step 104 to continue solving; otherwise, the calculation is completed and terminated.

[0050] In the above fluid-structure coupling parallel method for reactor fuel rod bundle thermal-hydraulic simulation, the whole calculation domain is divided into different lattices according to the spatial positions of the fuel rods of the reactor, each lattice contains a complete fuel rod, and each lattice is assigned to a single calculation core, the solid domain grid and the fluid domain grid are loaded and initialized for each calculation core, the data communication between the fluid and the structure is completed in the lattice by parallel partitioning according to the spatial position of the fuel rod bundle, the fluid-structure data communication between the calculation cores is avoided, the parallel simulation efficiency is improved, an effective solution is provided for large-scale coupled numerical simulation of fuel assemblies, then a solid solver is called to solve the solid heat transfer model on the solid domain grid; the heat flux and the solid temperature in the solid heat transfer model are judged, and the heat flux is transmitted to the fluid domain grid according to the judgment result; a fluid solver is called to calculate the flux at the wound interface of the fluid domain, the velocity, pressure and temperature on the grid cell at the wound interface of the fluid domain are calculated according to the flux, and the velocity, pressure and temperature are sent to the neighbor calculation core, and the variable field on the grid cell on the other side of the wound interface is received from the neighbor calculation core; the convergence of the velocity, pressure and temperature is judged, if the convergence is reached, the temperature is transmitted to the fluid domain grid through the fluid-structure interface, and the coupling heat transfer effect between the fluid and the structure is considered in the whole simulation process, compared with the traditional large-scale simulation which only performs fluid domain calculation, the calculation of the solid domain is realized, and the accuracy of the whole domain simulation is improved.

[0051] In one of the embodiments, the solid heat transfer model is solved on the solid domain grid, including:

[0052] The solid heat transfer model solved on the solid domain grid is

[0053]

[0054] wherein q is the heat flux, T s is the solid temperature, λ s is the thermal conductivity of the solid, and Q v is the heat source.

[0055] In one of the embodiments, the heat flux and the solid temperature in the solid heat transfer model are judged, and the heat flux is transmitted to the fluid domain grid according to the judgment result, including:

[0056] The heat flux and the solid temperature in the solid heat transfer model are judged, whether the heat flux and the solid temperature reach the convergence accuracy is judged, if the convergence is not reached, the solid heat transfer model is solved on the solid domain grid; if the convergence is reached, the heat flux is transmitted to the fluid domain grid through the fluid-structure interface.

[0057] In one of the embodiments, the flux at the wound interface of the fluid domain is calculated, including:

[0058] The fluxes at the wound interface are computed as

[0059] the two positive components, E f the modulus of E f is the variable to be solved, d CF is the vector of the connection of the computational cell with the neighboring cell centers, d CF is the modulus of d, V C is the volume of the current computational cell, p C is the density, Δt represents the time step, represents the density at the previous time step, represents the value of the current discrete cell variable at the previous time step, S b represents the equation source term, FluxC f represents the flux that affects the current discrete cell resulting from the computation of the convection and diffusion terms, FluxF f represents the flux that affects the neighboring cells of the current discrete cell resulting from the computation of the convection and diffusion terms, FluxV f represents the flux that affects the matrix source term resulting from the computation of the convection and diffusion terms, FluxC C represents the flux that affects the current discrete cell resulting from the computation of the transient term, FluxV C represents the flux that affects the matrix source term resulting from the computation of the transient and source terms.

[0060] In one of the embodiments, the velocity, pressure and temperature at the grid cells at the wound interface of the fluid domain are computed from the fluxes, including:

[0061] The expressions for the velocity, pressure and temperature at the grid cells at the wound interface of the fluid domain are solved sequentially from the fluxes as

[0062]

[0063] where,

[0064]

[0065] represents the coefficient of the current discrete cell, represents the coefficient of the neighboring cell of the current discrete cell, represents the matrix source term, p C represents the solution variable of the current discrete cell, the variable includes velocity, pressure and temperature, p F represents the solution variable of the neighboring cell of the current discrete cell, F represents the neighbor, NB(C) represents the number of neighbors.

[0066] It should be understood that although Figure 1The steps in the flowcharts of the above embodiments are displayed in sequence according to the arrows, but the steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified herein, the execution of the steps is not strictly limited in sequence, and the steps can be executed in other sequences. Moreover, Figure 1 At least a part of the steps in the flowcharts of the above embodiments can include a plurality of sub-steps or a plurality of stages, which are not necessarily executed at the same time, but can be executed at different times, and the execution sequence of the sub-steps or stages is not necessarily sequential, but can be executed in rotation or alternation with at least a part of other steps or sub-steps or stages of other steps.

[0067] The technical features of the above embodiments can be combined in any manner. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described, but it should be understood that any combination of the technical features is within the scope of the present disclosure as long as there is no contradiction.

[0068] The above embodiments only express several implementation manners of the present application, and the description is relatively specific and detailed, but it should not be understood as a limitation on the scope of the patent. It should be noted that, for those skilled in the art, some modifications and improvements can be made without departing from the concept of the present application, and these are within the scope of the present application. Therefore, the scope of the patent of the present application should be subject to the appended claims.

Claims

1. A fluid-structure coupling parallel method for reactor fuel bundle thermal-hydraulic simulation, characterized in that, The method comprises: dividing the whole calculation domain into different lattices according to the spatial positions of the fuel rods of the reactor, each lattice containing a complete fuel rod, and assigning each lattice to a separate calculation core, loading the solid domain grid and the fluid domain grid for each calculation core and initializing variable fields; the variable fields include temperature, velocity and pressure; calling a solid solver to solve a solid heat transfer model on the solid domain grid; judging the heat flux and the solid temperature in the solid heat transfer model, and transferring the heat flux to the fluid domain grid according to the judgment result; calling a fluid solver to calculate the flux at the wound interface of the fluid domain, calculating the velocity, pressure and temperature on the grid cell at the wound interface of the fluid domain according to the flux, and sending the velocity, pressure and temperature to the neighbor calculation core, and receiving the variable fields on the grid cell on the other side of the wound interface from the neighbor calculation core; judging the convergence of the velocity, pressure and temperature, and if the convergence is reached, sending the temperature to the fluid domain grid through the fluid-solid interface; judging the heat flux and the solid temperature in the solid heat transfer model, and transferring the heat flux to the fluid domain grid according to the judgment result, comprising: judging the heat flux and the solid temperature in the solid heat transfer model, and judging whether the heat flux and the solid temperature reach the convergence precision, if not, solving the solid heat transfer model on the solid domain grid; if the convergence is reached, transferring the heat flux to the fluid domain grid through the fluid-solid interface.

2. The method of claim 1, wherein, solving the solid heat transfer model on the solid domain grid, comprising: solving the solid heat transfer model on the solid domain grid is: wherein, q is the heat flux density, is the solid temperature, is the thermal conductivity of the solid, is the heat source.

3. The method according to any one of claims 1 to 2, characterized in that, calculating the flux at the wound interface of the fluid domain, comprising: calculating the flux at the wound interface of the fluid domain is: wherein is the mass flow, is the diffusion term coefficient, and are the face vectors two components of the non-orthogonal correction, is the modulus of ; is the variable to be solved, is the vector of the connection of the calculation cell with the neighbor cell center, is the modulus of is the volume of the current calculation cell, is the density, denotes the time step, denotes the density of the previous time step, denotes the value of the current discrete cell variable of the previous time step, denotes the equation source term, denotes the flux that influences the current discrete cell resulting from the calculation of the convection and diffusion terms, denotes the flux that influences the neighbor cell of the current discrete cell resulting from the calculation of the convection and diffusion terms, denotes the flux that influences the matrix source term resulting from the calculation of the convection and diffusion terms, denotes the flux that influences the current discrete cell resulting from the calculation of the transient term, denotes the flux that influences the matrix source term resulting from the calculation of the transient term and the source term.

4. The method of claim 3, wherein, calculating the velocity, pressure and temperature on the grid cell at the wound interface of the fluid domain according to the flux, comprising: the expressions of the velocity, pressure and temperature on the grid cell at the wound interface of the fluid domain solved according to the flux in turn are: wherein, represents a current discrete cell coefficient, represents a neighbor cell coefficient of a current discrete cell, represents a matrix source term, represents a current discrete cell solution variable, the variable including velocity, pressure and temperature, represents a neighbor cell solution variable of a current discrete cell, represents a neighbor, represents a number of neighbors.

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