A method, device, equipment and medium for determining passive scalar in large eddy simulation

Abstract

The present application discloses a method, device, equipment and medium for determining a passive scalar of a large eddy simulation, which is applied to the field of fluid mechanics technology, including: obtaining a target flow field velocity, the target flow field velocity includes a flow field velocity obtained by filtering a grid filter of a large eddy simulation and a flow field velocity obtained by filtering a test filter, the test filter being a filter with a grid size larger than that of a grid filter; determining an analytical passive scalar flux based on the target flow field velocity and the passive scalar at the previous moment; determining a target strain rate tensor based on the target flow field velocity; calculating an eddy viscosity coefficient based on the analytical passive scalar flux and the target strain rate tensor and using an eddy viscosity coefficient calculation formula; closing a transport equation of a passive scalar based on the eddy viscosity coefficient, and determining a passive scalar at the next moment corresponding to the previous moment based on the transport equation of the passive scalar. In this way, the eddy viscosity coefficient can be adaptively calculated, thereby accurately determining the passive scalar.

Description

Technical Field

[0001] The present application relates to the technical field of fluid mechanics, and in particular to a method, device, equipment and medium for determining a passive scalar in large eddy simulation. Background Art

[0002] Passive scalars refer to physical quantities that are passively transported in the flow field, such as temperature, component concentration, volume fraction of gas-liquid two-phase phase function, etc. Passive scalars are important data in fluid mechanics. At present, in the large eddy simulation scenario, how to accurately determine the passive scalar is an urgent problem to be solved. Summary of the invention

[0003] In view of this, the purpose of this application is to provide a method, device, equipment and medium for determining a passive scalar in large eddy simulation, which can accurately determine the passive scalar. The specific scheme is as follows:

[0004] In a first aspect, the present application discloses a method for determining a passive scalar in large eddy simulation, comprising:

[0005] Obtaining a target flow field velocity, wherein the target flow field velocity includes a flow field velocity obtained by filtering using a grid filter of large eddy simulation and a flow field velocity obtained by filtering using a test filter, wherein the test filter is a filter having a grid size larger than a grid size of the grid filter;

[0006] Determining an analytical passive scalar flux based on the target flow field velocity and the passive scalar at the previous moment, wherein the analytical passive scalar flux characterizes the contribution of the flow structure whose scale is between the filter width of the grid filter and the filter width of the test filter;

[0007] Determining a target strain rate tensor based on the target flow field velocity, wherein the target strain rate tensor includes a strain rate tensor obtained by filtering using a grid filter and a strain rate tensor obtained by using a test filter;

[0008] Based on the analytical passive scalar flux and the target strain rate tensor, the eddy viscosity coefficient is calculated using an eddy viscosity coefficient calculation formula, wherein the eddy viscosity coefficient calculation formula is established based on a passive scalar transport rate conservation relationship of a flow structure having a scale between a filter width of the grid filter and a filter width of the test filter;

[0009] The transport equation of the passive scalar is closed based on the eddy viscosity coefficient, and the passive scalar at the next moment corresponding to the previous moment is determined based on the transport equation of the passive scalar.

[0010] Optionally, the eddy viscosity coefficient calculation formula is:

[0011] ;

[0012] in, is the eddy viscosity coefficient, To resolve the passive scalar flux, is a passive scalar, represents the passive scalar after grid filter filtering, represents the passive scalar after the test filter is filtered, is the distance vector, To test the filter width, is the filter width of the grid filter, represents the norm of the strain rate tensor after the test filter, represents the norm of the strain rate tensor after grid filter filtering, Represents the filter processing of the test filter.

[0013] Optionally, when the preset flow field uniformity condition is met, the eddy viscosity coefficient calculation formula is:

[0014] ;

[0015] in, is the eddy viscosity coefficient, To resolve the passive scalar flux, is a passive scalar, represents the passive scalar after grid filter filtering, represents the passive scalar after the test filter is filtered, is the distance vector, is the filter width of the grid filter, represents the norm of the strain rate tensor after the test filter, represents the norm of the strain rate tensor after grid filter filtering, Represents the filter processing of the test filter.

[0016] Optionally, the determining and analyzing the passive scalar flux based on the target flow field velocity and the passive scalar at the previous moment includes:

[0017] The preset analytical passive scalar flux calculation formula is used, and the analytical passive scalar flux is determined based on the target flow field velocity and the passive scalar at the previous moment; the preset analytical passive scalar flux calculation formula is:

[0018] ;

[0019] in, To resolve the passive scalar flux, is a passive scalar, represents the passive scalar after grid filter filtering, represents the passive scalar after the test filter is filtered, represents the flow field velocity obtained by filtering using a grid filter, represents the flow field velocity obtained by filtering using the test filter, Represents the filter processing of the test filter.

[0020] Optionally, determining a target strain rate tensor based on the target flow field velocity includes:

[0021] The target strain rate tensor is determined by using a preset strain rate tensor calculation formula and based on the target flow field velocity; the preset strain rate tensor calculation formula is:

[0022] , ;

[0023] in, represents the strain rate tensor after grid filter filtering, , represents the flow field velocity obtained by filtering using a grid filter, , is the distance vector, represents the strain rate tensor after the test filter, , It represents the flow field velocity obtained by filtering using the test filter, and i and j represent different directions.

[0024] Alternatively, the transport equation for the passive scalar is:

[0025] ;

[0026] in, is the eddy viscosity coefficient, is a passive scalar, represents the passive scalar after grid filter filtering, t is the time, is the distance vector, is the filter width of the grid filter, represents the norm of the strain rate tensor after grid filter filtering, Represents the flow field velocity obtained by filtering using a grid filter.

[0027] Optionally, obtaining the target flow field velocity includes:

[0028] Get the target flow field velocity at the previous moment;

[0029] Or, calculate the target flow field velocity at the next moment corresponding to the previous moment.

[0030] In a second aspect, the present application discloses a passive scalar determination device for large eddy simulation, comprising:

[0031] A flow field velocity acquisition module, used to acquire a target flow field velocity, wherein the target flow field velocity includes a flow field velocity obtained by filtering using a grid filter of a large eddy simulation and a flow field velocity obtained by filtering using a test filter, wherein the test filter is a filter having a grid size larger than a grid size of the grid filter;

[0032] An analytical passive scalar flux determination module is used to determine an analytical passive scalar flux based on the target flow field velocity and the passive scalar at the previous moment, wherein the analytical passive scalar flux characterizes the contribution of the flow structure whose scale is between the filter width of the grid filter and the filter width of the test filter;

[0033] A strain rate tensor determination module, configured to determine a target strain rate tensor based on the target flow field velocity, wherein the target strain rate tensor includes a strain rate tensor obtained by filtering using a grid filter and a strain rate tensor obtained by using a test filter;

[0034] An eddy viscosity coefficient calculation module, used for calculating the eddy viscosity coefficient based on the analytical passive scalar flux and the target strain rate tensor and using an eddy viscosity coefficient calculation formula, wherein the eddy viscosity coefficient calculation formula is established based on a passive scalar transport rate conservation relationship of a flow structure whose scale is between the filter width of the grid filter and the filter width of the test filter;

[0035] The passive scalar determination module is used to close the transport equation of the passive scalar based on the eddy viscosity coefficient, and determine the passive scalar at the next moment corresponding to the previous moment based on the transport equation of the passive scalar.

[0036] In a third aspect, the present application discloses an electronic device, including a memory and a processor, wherein:

[0037] The memory is used to store the computer program;

[0038] The processor is used to execute the computer program to implement the aforementioned passive scalar determination method for large eddy simulation.

[0039] In a fourth aspect, the present application discloses a computer-readable storage medium for storing a computer program, wherein the computer program, when executed by a processor, implements the aforementioned passive scalar determination method for large eddy simulation.

[0040] It can be seen from the above scheme that the present application provides a method for determining a passive scalar of a large eddy simulation, including: obtaining a target flow field velocity, wherein the target flow field velocity includes a flow field velocity obtained by filtering with a grid filter of a large eddy simulation and a flow field velocity obtained by filtering with a test filter, and the test filter is a filter whose grid size is larger than that of the grid filter; determining an analytical passive scalar flux based on the target flow field velocity and the passive scalar at the previous moment, wherein the analytical passive scalar flux characterizes the contribution of a flow structure whose scale is between the filter width of the grid filter and the filter width of the test filter; determining an analytical passive scalar flux based on the target flow field velocity and the passive scalar at the previous moment, wherein the analytical passive scalar flux characterizes the contribution of a flow structure whose scale is between the filter width of the grid filter and the filter width of the test filter; determining an analytical passive scalar flux based on the target flow field velocity The target strain rate tensor is determined, wherein the target strain rate tensor includes a strain rate tensor obtained by filtering with a grid filter and a strain rate tensor obtained by filtering with a test filter; an eddy viscosity coefficient is calculated based on the analytical passive scalar flux and the target strain rate tensor and using an eddy viscosity coefficient calculation formula, wherein the eddy viscosity coefficient calculation formula is established based on a passive scalar transport rate conservation relationship of a flow structure whose scale is between a filter width of the grid filter and a filter width of the test filter; a transport equation of a passive scalar is closed based on the eddy viscosity coefficient, and a passive scalar at a next moment corresponding to the previous moment is determined based on the transport equation of the passive scalar.

[0041] It can be seen that the beneficial effects of the present application are: using the large eddy simulation method to calculate the passive scalar transport, based on the conservation relationship of the passive scalar transport rate of the flow structure whose scale is between the filtering width of the grid filter and the filtering width of the test filter, according to the local flow characteristics of the flow field, the eddy viscosity coefficient can be adaptively calculated, thereby accurately determining the passive scalar.

[0042] Correspondingly, the passive scalar device, equipment and readable storage medium for large eddy simulation provided by the present application also have the above-mentioned technical effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0044] Figure 1 A flow chart of a method for determining a passive scalar in large eddy simulation provided in an embodiment of the present application;

[0045] Figure 2 A grid schematic diagram provided for an embodiment of the present application;

[0046] Figure 3A schematic diagram for determining a passive scalar transport equation provided in an embodiment of the present application;

[0047] Figure 4 A flow chart for solving a passive scalar provided in an embodiment of the present application;

[0048] Figure 5 A schematic diagram of the structure of a passive scalar device for large eddy simulation provided in an embodiment of the present application;

[0049] Figure 6 A structural diagram of an electronic device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0050] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0051] At present, it is urgent to independently develop fluid industry software. For industrial-scale fluid mechanics simulation problems, large eddy simulation is a commonly used technology. It can ensure the accurate characterization of multi-scale turbulence by the fluid solver and greatly reduce the amount of calculation. It is an important technology for modern fluid simulation software. However, there is still a blank in the passive scalar large eddy simulation method. In view of the industrial demand for large eddy simulation of gas-liquid two-phase flow problems, it is necessary to develop corresponding passive scalar large eddy simulation methods to realize large eddy simulation of gas-liquid two-phase turbulence.

[0052] Two-phase flow is very common in daily life. For example, in chemical industry, petroleum, food processing, biomedicine and environmental engineering, flow systems composed of two fluids, gas and liquid, are often involved, such as: the movement of bubbles in liquid, the movement of droplets in gas, and boiling and condensation processes. These problems usually involve complex physical processes, including fluid dynamics, heat transfer and mass transfer. In engineering applications, the solution of these problems is crucial to improving system efficiency, ensuring operational safety and optimizing process. The gas-liquid two-phase flow solver consists of two parts: a fluid solver and a gas-liquid two-phase phase function solver. For two-phase flow, in addition to analyzing the flow field velocity, it is also necessary to accurately analyze the position of the two-phase interface, that is, to solve the phase function transport equation. Therefore, the implementation of large eddy simulation of gas-liquid two-phase flow needs to consider the fluid solver and the gas-liquid two-phase phase function solver respectively. This application develops and implements the large eddy simulation technology of the gas-liquid two-phase phase function solver. The control equation of the gas-liquid two-phase phase function solver is a passive scalar transport equation, so this application provides a large eddy simulation technology of the passive scalar transport equation.

[0053] See also Figure 1 As shown, the embodiment of the present application discloses a method for determining a passive scalar in large eddy simulation, comprising:

[0054] Step S11: Obtain a target flow field velocity, wherein the target flow field velocity includes a flow field velocity obtained by filtering using a grid filter of a large eddy simulation and a flow field velocity obtained by filtering using a test filter, wherein the test filter is a filter having a grid size larger than a grid size of the grid filter.

[0055] In an optional implementation, the target flow field velocity at the previous moment can be obtained. In another optional implementation, the target flow field velocity at the next moment corresponding to the previous moment can be calculated. That is, the present application can first update the flow field velocity, and then update the passive scalar based on the updated flow field velocity, or first update the passive scalar based on the flow field velocity at the previous moment, and then update the flow field velocity.

[0056] Step S12: determining an analytical passive scalar flux based on the target flow field velocity and the passive scalar at the previous moment, wherein the analytical passive scalar flux characterizes the contribution of the flow structure whose scale is between the filter width of the grid filter and the filter width of the test filter.

[0057] This embodiment can use a preset analytical passive scalar flux calculation formula, and determine the analytical passive scalar flux based on the target flow field velocity and the passive scalar at the previous moment; the preset analytical passive scalar flux calculation formula is:

[0058] ;

[0059] in, To resolve the passive scalar flux, is a passive scalar, represents the passive scalar after grid filter filtering, represents the passive scalar after the test filter is filtered, represents the flow field velocity obtained by filtering using a grid filter, represents the flow field velocity obtained by filtering using the test filter, Represents the filter processing of the test filter.

[0060] Step S13: determining a target strain rate tensor based on the target flow field velocity, wherein the target strain rate tensor includes a strain rate tensor obtained by filtering using a grid filter and a strain rate tensor obtained by using a test filter.

[0061] In this embodiment, a preset strain rate tensor calculation formula may be used to determine the target strain rate tensor based on the target flow field velocity; the preset strain rate tensor calculation formula is:

[0062] , ;

[0063] in, represents the strain rate tensor after grid filter filtering, , represents the flow field velocity obtained by filtering using a grid filter, , is the distance vector, represents the strain rate tensor after the test filter, , It represents the flow field velocity obtained by filtering using the test filter, and i and j represent different directions.

[0064] Step S14: Based on the analytical passive scalar flux and the target strain rate tensor, the eddy viscosity coefficient is calculated using an eddy viscosity coefficient calculation formula, wherein the eddy viscosity coefficient calculation formula is established based on a passive scalar transport rate conservation relationship of a flow structure whose scale is between the filter width of the grid filter and the filter width of the test filter.

[0065] In this embodiment, the eddy viscosity coefficient calculation formula is:

[0066] ;

[0067] in, is the eddy viscosity coefficient, To resolve the passive scalar flux, is a passive scalar, represents the passive scalar after grid filter filtering, represents the passive scalar after the test filter is filtered, is the distance vector, To test the filter width, is the filter width of the grid filter, represents the norm of the strain rate tensor after the test filter, represents the norm of the strain rate tensor after grid filter filtering, Represents the filter processing of the test filter. , .

[0068] Furthermore, when the preset flow field uniformity condition is met, the eddy viscosity coefficient calculation formula is:

[0069] ;

[0070] in, is the eddy viscosity coefficient, To resolve the passive scalar flux, is a passive scalar, represents the passive scalar after grid filter filtering, represents the passive scalar after the test filter is filtered, is the distance vector, is the filter width of the grid filter, represents the norm of the strain rate tensor after the test filter, represents the norm of the strain rate tensor after grid filter filtering, Represents the filter processing of the test filter.

[0071] That is, in this embodiment, when the flow field is uniform and has a simple geometric shape, a uniform grid can be used, and the filter width of the test filter is twice the filter width of the grid filter. The calculation formula of the eddy viscosity coefficient can be simplified to the above formula, thereby reducing the amount of calculation. A uniform grid means that the grid size is consistent. A uniform flow field can be understood as a flow field without a large velocity gradient and no drastic changes. The solver sets the grid division method based on experience and specific problems.

[0072] Step S15: closing the transport equation of the passive scalar based on the eddy viscosity coefficient, and determining the passive scalar at the next moment corresponding to the previous moment based on the transport equation of the passive scalar.

[0073] In this embodiment, the transport equation of the passive scalar may be:

[0074] ;

[0075] in, is the eddy viscosity coefficient, is a passive scalar, represents the passive scalar after grid filter filtering, t is the time, is the distance vector, is the filter width of the grid filter, represents the norm of the strain rate tensor after grid filter filtering, Represents the flow field velocity obtained by filtering using a grid filter.

[0076] It should be noted that the core idea of ​​Large Eddy Simulation (LES) is to decompose the flow into large-scale resolvable flow and small-scale flow that needs to be approximated by the model through spatial filtering. Among them, large scale and small scale are relative concepts, which are related to the problem to be solved, the part of concern, the size of the computational domain, etc., and there is no absolute value. The size scale depends on the size of the filter function. The filter function filters out the small scale, and retains the large scale. The implementation of spatial filtering usually adopts convolution operation, using the filter function (filter) With physical quantity Perform convolution calculations to obtain physical quantities on a coarser grid :

[0077] (1);

[0078] The filter function in large eddy simulation is a tool used to separate large-scale vortices in the fluid field (the part that we want to simulate directly) from small-scale vortices (the part that needs to be simulated through a subgrid model). The filter function is usually a local operation, which can be a box filter, a Gaussian filter, or a hat filter. Among them, the physical quantity is a general concept, and any physical quantity can be obtained by filtering to obtain the large-scale part. Among them, the grid size of the coarser grid is based on the specific problem to be solved and is controlled by the size of the filter.

[0079] The passive scalar transport equation is:

[0080] (2);

[0081] Where t is time, is a distance vector. All vectors in this application are expressed in the form of Einstein indicators. The subscript j=1, 2, 3 represents three different directions. Passive scalars, such as temperature, concentration, gas-liquid two-phase function, etc. is the velocity vector. Use grid filter The passive scalar transport equation is filtered to obtain the following filtering equation:

[0082] (3);

[0083] In this application, the physical quantities with upper horizontal lines represent the large-scale flow results after grid filter filtering, which can be directly calculated. and the velocity vector Decomposed into resolvable large-scale components ( and ), and the unresolved small-scale part ( and ):

[0084] (4);

[0085] (5);

[0086] Therefore, the second term in equation (3) It can be expanded into the following form:

[0087] (6);

[0088] When the filter function is operated by the Reynolds operator, ,in is any unresolved small-scale physical quantity.

[0089] The Reynolds operator satisfies the operation rules: , , The operation operator of . , is an arbitrary physical quantity, and the upper horizontal line represents the result of the operator.

[0090] Therefore, the second and third terms on the right side of the equal sign in the above formula satisfy:

[0091] (7);

[0092] (8);

[0093] At this time, formula (6) can be simplified as:

[0094] (9);

[0095] Define subgrid-scale passive scalar flux :

[0096] (10);

[0097] Among them, the second equal sign holds true when the filter's operation operator is the Reynolds operator.

[0098] Will Substituting into the filtering equation (3), the filtered passive scalar transport equation is as follows:

[0099] (11);

[0100] The influence of small-scale structures smaller than the filter scale on passive scalar transport is shown. Large eddy simulation can only directly calculate large-scale flows, so a model needs to be introduced to approximate the contribution of small-scale flow structures to the flow.

[0101] Here, the Smagorinsky model is used as an analogy. Based on the eddy viscosity assumption, the subgrid passive scalar flux term is expressed in a form similar to viscous stress. The mathematical expression for modeling is:

[0102] (12);

[0103] in, is the filter width, , , is the eddy viscosity coefficient, is the Einstein tensor representation. Dimensional analysis is performed on both sides of the equation to verify its correctness, and the results are as follows:

[0104] (13);

[0105] L represents distance, T represents time, and formula (13) represents the dimension alignment of formula (12). To close the above-obtained filtered passive scalar transport equation, the eddy viscosity coefficient needs to be given: This application is based on the model proposed by Germano in 1991 to derive the eddy viscosity coefficient , which can adaptively calculate The specific process of adaptively calculating the eddy viscosity coefficient is given below.

[0106] In addition to using a grid filter, the present invention also uses a grid filter. In addition, the test filter (testfilter) is introduced The test filter grid size is larger than the grid filter grid size. The choice of filters can be the same or different, which does not affect the expression of the formula. The final definition is: .

[0107] DNS grids, LES grid filters, and test filter grids are available at Figure 2 As shown, Figure 2 A grid schematic diagram provided for an embodiment of the present application. The gray grid represents the DNS grid, which can resolve all scale structures in the flow; the blue grid represents the grid filter grid of the LES, which is larger than the DNS grid, and therefore can only resolve large-scale structures in the flow field. The grid of the test filter is shown by the red dotted line (here the test filter filter size is taken as 2 times the grid filter filter size as an example). The result after the test filter processing can be obtained by averaging the results of the grid filter processing. For example, the value after the test filter is applied at the red node in the figure can be obtained by weighted averaging the results at the nine grid point positions defined by the red dotted line.

[0108] Similarly, using Filtering the passive scalar transport equation yields the following equation:

[0109] (14);

[0110] In this application, physical quantities with upper horizontal lines and upper wavy lines, such as (f is an arbitrary physical quantity), which represents the large-scale flow result after the test filter is filtered. is the subgrid passive scalar flux, expressed as:

[0111] (15);

[0112] Similarly, when the filter operator is the Reynolds operator, the last equal sign in the above formula holds.

[0113] Define resolved passive scalar flux :

[0114] (16);

[0115] This term represents the passive scalar flux filtered by a grid filter with a scale between and test filter width The contribution of the flow structure between The expression of contains only the filtered physical quantities.

[0116] Using the above model, that is, formula (12), and The models are as follows:

[0117] (17);

[0118] (18);

[0119] Substituting formula (17) (18) into formula (16), we obtain:

[0120] (19);

[0121] Dimensional analysis on both sides of the equal sign in the above formula yields:

[0122] (20);

[0123] The dimensions on both sides of the equation are the passive scalar transport rates, which indicates that, at the physical level, equation (18) reflects the scale between the grid filter width and test filter width The passive scalar transport rate of the flow structure between them is conserved.

[0124] Finally, the eddy viscosity coefficient is obtained The expression is:

[0125] (twenty one);

[0126] This expression only contains the physical quantity after filtering, so equation (11) is closed. And the eddy viscosity coefficient calculated by this method is It can be adaptively adjusted according to the local flow characteristics of the flow field, thereby improving the adaptability of the model to different flow conditions. It can be seen that in this application, the eddy viscosity coefficient is not a pre-given empirical parameter, but a value calculated based on the local flow field and phase field, so it is adaptive.

[0127] For three-dimensional problems, if:

[0128] If the flow field is uniform (e.g., the velocity is uniform and there is no large velocity gradient) and the geometry is simple, a uniform grid can be used, i.e. , ;

[0129] The filter width of the test filter is twice the filter width of the grid filter, that is, , where the subscript i represents the grid direction, we have:

[0130] (twenty two);

[0131] (twenty three);

[0132] So the constant It can also be expressed as:

[0133] (twenty four);

[0134] The filtered passive scalar transport equation is finally expressed as:

[0135] (25);

[0136] For example, see Figure 3 As shown, Figure 3 A schematic diagram for determining a passive scalar transport equation provided in an embodiment of the present application.

[0137] For further information, see Figure 4 As shown, Figure 4A flow chart for solving passive scalar transport provided in an embodiment of the present application. When solving passive scalar, the flow of each iterative calculation is as follows (the upper right script indicates the time step):

[0138] First, the flow field velocity is obtained through the fluid solver , ;

[0139] According to the updated velocity field , and the passive scalar at the previous moment , , the analytical passive scalar flux is calculated by formula (16) ;

[0140] According to the updated velocity field , , calculate the strain rate tensor , ;

[0141] The eddy viscosity coefficient is calculated according to formula (21): ;

[0142] Solve equation (25) to calculate the passive scalar at the next moment .

[0143] After updating the passive scalar, return to step 1 and repeat the above process.

[0144] It should be noted that the above process is only an example of a calculation process for calculating two-phase flow based on the large eddy simulation passive scalar transport equation (25) derived above. In actual operation, the passive scalar can be updated first and then the velocity.

[0145] This embodiment is based on the model proposed by Germano in 1991, and the control equations for the numerical solution of the passive scalar transport large eddy simulation are derived. The eddy viscosity coefficient of the passive scalar large eddy simulation is adaptive and does not need to be given in advance. Based on this, the passive scalar large eddy simulation numerical simulation independent source code simulation software is developed to achieve independent control of the independent source code software, and the source code software can be parallel calculated by the CPU (i.e., Central Processing Unit).

[0146] This application achieves a breakthrough from 0 to 1 and develops a passive scalar large eddy simulation numerical solver. Passive scalar refers to physical quantities that are passively transported in the flow field, such as temperature, component concentration, volume fraction of gas-liquid two-phase phase function, etc. For single-phase flow, large eddy simulation technology is very mature; however, for problems involving gas-liquid two-phase flow, multi-component chemical reactions, etc., the corresponding passive scalar large eddy simulation patented technology has not yet been seen in the world. The passive scalar large eddy simulation numerical solver developed in this application is dedicated to solving the phase function of gas-liquid two-phase flow, which can achieve high-precision simulation of multi-scale turbulence of gas-liquid two-phase flow, while greatly reducing the amount of calculation, serving the realization of industrial-scale simulation and optimization design.

[0147] It can be seen that in the large eddy simulation scenario, the embodiment of the present application is based on the conservation relationship of the passive scalar transport rate of the flow structure whose scale is between the filtering width of the grid filter and the filtering width of the test filter, and according to the local flow characteristics of the flow field, the eddy viscosity coefficient can be adaptively calculated, thereby accurately determining the passive scalar.

[0148] See also Figure 5 As shown, the embodiment of the present application discloses a passive scalar determination device for large eddy simulation, comprising:

[0149] A flow field velocity acquisition module 11 is used to acquire a target flow field velocity, wherein the target flow field velocity includes a flow field velocity obtained by filtering using a grid filter of a large eddy simulation and a flow field velocity obtained by filtering using a test filter, wherein the test filter is a filter having a grid size larger than a grid size of the grid filter;

[0150] An analytical passive scalar flux determination module 12 is used to determine an analytical passive scalar flux based on the target flow field velocity and the passive scalar at the previous moment, wherein the analytical passive scalar flux characterizes the contribution of the flow structure whose scale is between the filter width of the grid filter and the filter width of the test filter;

[0151] A strain rate tensor determination module 13, configured to determine a target strain rate tensor based on the target flow field velocity, wherein the target strain rate tensor includes a strain rate tensor obtained by filtering using a grid filter and a strain rate tensor obtained by using a test filter;

[0152] An eddy viscosity coefficient calculation module 14 is used to calculate the eddy viscosity coefficient based on the analytical passive scalar flux and the target strain rate tensor and using an eddy viscosity coefficient calculation formula, wherein the eddy viscosity coefficient calculation formula is established based on a passive scalar transport rate conservation relationship of a flow structure whose scale is between the filter width of the grid filter and the filter width of the test filter;

[0153] The passive scalar determination module 15 is used to close the transport equation of the passive scalar based on the eddy viscosity coefficient, and determine the passive scalar at the next moment corresponding to the previous moment based on the transport equation of the passive scalar.

[0154] Optionally, the strain eddy viscosity coefficient calculation module 14 is specifically used for:

[0155] Based on the analytical passive scalar flux and the target strain rate tensor, the eddy viscosity coefficient is calculated using the eddy viscosity coefficient calculation formula, and the eddy viscosity coefficient calculation formula is:

[0156] ;

[0157] in, is the eddy viscosity coefficient, To resolve the passive scalar flux, is a passive scalar, represents the passive scalar after grid filter filtering, represents the passive scalar after the test filter is filtered, is the distance vector, To test the filter width, is the filter width of the grid filter, represents the norm of the strain rate tensor after the test filter, represents the norm of the strain rate tensor after grid filter filtering, Represents the filter processing of the test filter.

[0158] Optionally, when the preset flow field uniformity condition is met, the eddy viscosity coefficient calculation formula is:

[0159] ;

[0160] in, is the eddy viscosity coefficient, To resolve the passive scalar flux, is a passive scalar, represents the passive scalar after grid filter filtering, represents the passive scalar after the test filter is filtered, is the distance vector, is the filter width of the grid filter, represents the norm of the strain rate tensor after the test filter, represents the norm of the strain rate tensor after grid filter filtering, Represents the filter processing of the test filter.

[0161] Optionally, the analytical passive scalar flux determination module 12 is specifically used for:

[0162] The preset analytical passive scalar flux calculation formula is used, and the analytical passive scalar flux is determined based on the target flow field velocity and the passive scalar at the previous moment; the preset analytical passive scalar flux calculation formula is:

[0163] ;

[0164] in, To resolve the passive scalar flux, is a passive scalar, represents the passive scalar after grid filter filtering, represents the passive scalar after the test filter is filtered, represents the flow field velocity obtained by filtering using a grid filter, represents the flow field velocity obtained by filtering using the test filter, Represents the filter processing of the test filter.

[0165] Optionally, the strain rate tensor determination module 13 is specifically used for:

[0166] The target strain rate tensor is determined by using a preset strain rate tensor calculation formula and based on the target flow field velocity; the preset strain rate tensor calculation formula is:

[0167] , ;

[0168] in, represents the strain rate tensor after grid filter filtering, , represents the flow field velocity obtained by filtering using a grid filter, , is the distance vector, represents the strain rate tensor after the test filter, , It represents the flow field velocity obtained by filtering using the test filter, and i and j represent different directions.

[0169] Alternatively, the transport equation for the passive scalar is:

[0170] ;

[0171] in, is the eddy viscosity coefficient, is a passive scalar, represents the passive scalar after grid filter filtering, t is the time, is the distance vector, is the filter width of the grid filter, represents the norm of the strain rate tensor after grid filter filtering, Represents the flow field velocity obtained by filtering using a grid filter.

[0172] Optionally, the flow field velocity acquisition module 11 is specifically used for:

[0173] Get the target flow field velocity at the previous moment;

[0174] Or, calculate the target flow field velocity at the next moment corresponding to the previous moment.

[0175] It can be seen that in the large eddy simulation scenario, the embodiment of the present application is based on the conservation relationship of the passive scalar transport rate of the flow structure whose scale is between the filtering width of the grid filter and the filtering width of the test filter, and according to the local flow characteristics of the flow field, the eddy viscosity coefficient can be adaptively calculated, thereby accurately determining the passive scalar.

[0176] See also Figure 6 As shown, an embodiment of the present application discloses an electronic device 20, including a processor 21 and a memory 22; wherein the memory 22 is used to store a computer program; the processor 21 is used to execute the computer program, the passive scalar determination method of large eddy simulation disclosed in the above embodiment.

[0177] For the specific process of the passive scalar determination method of the above-mentioned large eddy simulation, reference may be made to the corresponding contents disclosed in the aforementioned embodiments, which will not be repeated here.

[0178] Furthermore, the memory 22 as a carrier for storing resources may be a read-only memory, a random access memory, a magnetic disk or an optical disk, etc., and the storage method may be temporary storage or permanent storage.

[0179] In addition, the electronic device 20 also includes a power supply 23, a communication interface 24, an input / output interface 25 and a communication bus 26; wherein the power supply 23 is used to provide working voltage for each hardware device on the electronic device 20; the communication interface 24 can create a data transmission channel between the electronic device 20 and an external device, and the communication protocol it follows is any communication protocol that can be applied to the technical solution of the present application, and is not specifically limited here; the input / output interface 25 is used to obtain external input data or output data to the outside world, and its specific interface type can be selected according to specific application needs, and is not specifically limited here.

[0180] Furthermore, an embodiment of the present application also discloses a computer-readable storage medium for storing a computer program, wherein the computer program, when executed by a processor, implements the passive scalar determination method for large eddy simulation disclosed in the aforementioned embodiment.

[0181] For the specific process of the passive scalar determination method of the above-mentioned large eddy simulation, reference may be made to the corresponding contents disclosed in the aforementioned embodiments, which will not be repeated here.

[0182] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0183] The steps of the method or algorithm described in conjunction with the embodiments disclosed herein may be implemented directly using hardware, a software module executed by a processor, or a combination of the two. The software module may be placed in a random access memory (RAM), a memory, a read-only memory (ROM), an electrically programmable ROM, an electrically erasable programmable ROM, a register, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.

[0184] The above is a detailed introduction to the passive scalar determination method, device, equipment and medium for large eddy simulation provided by the present application. Specific examples are used in this article to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method of the present application and its core idea; at the same time, for general technical personnel in this field, according to the idea of ​​the present application, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. A passive scalar determination method for large eddy simulation, characterized in that: include: Obtaining a target flow field velocity, wherein the target flow field velocity includes a flow field velocity obtained by filtering using a grid filter of large eddy simulation and a flow field velocity obtained by filtering using a test filter, wherein the test filter is a filter having a grid size larger than a grid size of the grid filter; Determining an analytical passive scalar flux based on the target flow field velocity and the passive scalar at the previous moment, wherein the analytical passive scalar flux characterizes the contribution of the flow structure whose scale is between the filter width of the grid filter and the filter width of the test filter; Determining a target strain rate tensor based on the target flow field velocity, wherein the target strain rate tensor includes a strain rate tensor obtained by filtering using a grid filter and a strain rate tensor obtained by using a test filter; Based on the analytical passive scalar flux and the target strain rate tensor, the eddy viscosity coefficient is calculated using an eddy viscosity coefficient calculation formula, wherein the eddy viscosity coefficient calculation formula is established based on a passive scalar transport rate conservation relationship of a flow structure having a scale between a filter width of the grid filter and a filter width of the test filter; The transport equation of the passive scalar is closed based on the eddy viscosity coefficient, and the passive scalar at the next moment corresponding to the previous moment is determined based on the transport equation of the passive scalar.

2. The passive scalar determination method for large eddy simulation according to claim 1, characterized in that: The eddy viscosity coefficient calculation formula is: ； in, is the eddy viscosity coefficient, To resolve the passive scalar flux, is a passive scalar, represents the passive scalar after grid filter filtering, represents the passive scalar after the test filter is filtered, is the distance vector, To test the filter width of the filter, is the filter width of the grid filter, represents the norm of the strain rate tensor after the test filter, represents the norm of the strain rate tensor after grid filter filtering, Represents the filter processing of the test filter.

3. The passive scalar determination method for large eddy simulation according to claim 1, characterized in that: When the preset flow field uniformity condition is met, the eddy viscosity coefficient calculation formula is: ； in, is the eddy viscosity coefficient, To resolve the passive scalar flux, is a passive scalar, represents the passive scalar after grid filter filtering, represents the passive scalar after the test filter is filtered, is the distance vector, is the filter width of the grid filter, represents the norm of the strain rate tensor after the test filter, represents the norm of the strain rate tensor after grid filter filtering, Represents the filter processing of the test filter.

4. The passive scalar determination method for large eddy simulation according to claim 1, characterized in that: The step of determining and analyzing the passive scalar flux based on the target flow field velocity and the passive scalar at the previous moment includes: The preset analytical passive scalar flux calculation formula is used, and the analytical passive scalar flux is determined based on the target flow field velocity and the passive scalar at the previous moment; the preset analytical passive scalar flux calculation formula is: ； in, To resolve the passive scalar flux, is a passive scalar, represents the passive scalar after grid filter filtering, represents the passive scalar after the test filter is filtered, represents the flow field velocity obtained by filtering using a grid filter, represents the flow field velocity obtained by filtering using the test filter, Represents the filter processing of the test filter.

5. The passive scalar determination method for large eddy simulation according to claim 1, characterized in that: The determining of a target strain rate tensor based on the target flow field velocity comprises: The target strain rate tensor is determined by using a preset strain rate tensor calculation formula and based on the target flow field velocity; the preset strain rate tensor calculation formula is: 、 ； in, represents the strain rate tensor after grid filter filtering, , represents the flow field velocity obtained by filtering using a grid filter, , is the distance vector, represents the strain rate tensor after the test filter, , It represents the flow field velocity obtained by filtering using the test filter, and i and j represent different directions.

6. The passive scalar determination method for large eddy simulation according to any one of claims 1 to 5, characterized in that: The transport equation for the passive scalar is: ； in, is the eddy viscosity coefficient, is a passive scalar, represents the passive scalar after grid filter filtering, t is the time, is the distance vector, is the filter width of the grid filter, represents the norm of the strain rate tensor after grid filter filtering, Represents the flow field velocity obtained by filtering using a grid filter.

7. The passive scalar determination method for large eddy simulation according to claim 1, characterized in that: The obtaining of the target flow field velocity comprises: Get the target flow field velocity at the previous moment; Or, calculate the target flow field velocity at the next moment corresponding to the previous moment.

8. A passive scalar determination device for large eddy simulation, characterized in that: include: A flow field velocity acquisition module, used to acquire a target flow field velocity, wherein the target flow field velocity includes a flow field velocity obtained by filtering using a grid filter of a large eddy simulation and a flow field velocity obtained by filtering using a test filter, wherein the test filter is a filter having a grid size larger than a grid size of the grid filter; An analytical passive scalar flux determination module is used to determine an analytical passive scalar flux based on the target flow field velocity and the passive scalar at the previous moment, wherein the analytical passive scalar flux characterizes the contribution of the flow structure whose scale is between the filter width of the grid filter and the filter width of the test filter; A strain rate tensor determination module, configured to determine a target strain rate tensor based on the target flow field velocity, wherein the target strain rate tensor includes a strain rate tensor obtained by filtering using a grid filter and a strain rate tensor obtained by using a test filter; An eddy viscosity coefficient calculation module, used for calculating the eddy viscosity coefficient based on the analytical passive scalar flux and the target strain rate tensor and using an eddy viscosity coefficient calculation formula, wherein the eddy viscosity coefficient calculation formula is established based on a passive scalar transport rate conservation relationship of a flow structure whose scale is between the filter width of the grid filter and the filter width of the test filter; The passive scalar determination module is used to close the transport equation of the passive scalar based on the eddy viscosity coefficient, and determine the passive scalar at the next moment corresponding to the previous moment based on the transport equation of the passive scalar.

9. An electronic device, characterized in that: comprising a memory and a processor, wherein: The memory is used to store the computer program; The processor is used to execute the computer program to implement the passive scalar determination method for large eddy simulation according to any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that: Used to store a computer program, wherein when the computer program is executed by a processor, the passive scalar determination method for large eddy simulation according to any one of claims 1 to 7 is implemented.

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