A non-partitioned turbulence generation method based on synthetic particle groups

Abstract

The present invention proposes a non-partitioned turbulence generation method based on a synthetic particle group, including determining the basic characteristics of the synthetic particle group; setting the injection criteria of the synthetic particle group, including the generation position and the injection algorithm; completing the injection of the synthetic particle group according to the injection criteria to induce the generation of small-scale turbulent structures. The method proposed by the present invention uses a synthetic particle group to approximate high- and low-speed strip flow units. The construction of the synthetic particle group only involves local flow field variables and has good locality. The disturbance added in the form of volume force can quickly induce the generation of turbulent vortices to obtain a turbulent boundary layer.

Description

Technical Field

[0001] The invention belongs to the field of high-precision non-steady numerical simulation calculation. Background Art

[0002] In the past 10 years, driven by the needs of the national economy and national defense, the aerospace industry has developed rapidly. In various flight conditions of aircraft, flow separation often occurs. Whether it is a large-scale flow separation caused by high-angle flight or a small local separation caused by shock wave boundary layer interference at high Mach numbers, it will cause damage to the local structure or thermal protection system of the aircraft. In severe cases, it may even affect the smooth execution of the flight mission. Therefore, in the overall design stage of the aircraft, numerical simulation can be used to predict such flow phenomena, providing important support for the aerodynamic shape and structural design of the aircraft.

[0003] With the continuous development of computational fluid dynamics, combined with the pursuit of efficiency and accuracy in practical engineering applications, high-precision unsteady flow numerical simulation methods, Reynolds-Averaged Navier-Stokes (RANS)-Large Eddy Simulation (LES) hybrid method (abbreviated as RANS-LES hybrid method), is one of the main methods currently used. The main problem of the traditional RANS-LES hybrid method is the "gray area" problem, that is, there is a long transition zone when the RANS mode transitions to the LES mode. The LES mode switching is not timely, which can easily cause the turbulent structure analysis obtained by numerical prediction to be insufficient, the shear layer instability is delayed, and the flow separation position error is large. Therefore, it is impossible to provide more accurate and reasonable guidance for the structural design of the aircraft. To address this type of problem, the RANS-LES hybrid method combined with the turbulence generation method can be used. The turbulence generation method can impose turbulent disturbances in the flow field, accelerate the switching of the RANS-LES hybrid method from the RANS mode to the LES mode, and induce the generation of small-scale turbulent structures, which is conducive to alleviating the "gray zone" problem and improving the prediction accuracy of the RANS-LES hybrid method.

[0004] Currently, the existing turbulence generation methods are mainly inlet turbulence generation methods, such as the synthetic vortex method and the synthetic hairpin vortex method. The main idea is to use kernel functions to approximate turbulent vortices based on various vortex models, thereby applying turbulent disturbances.

[0005] Existing methods for generating inlet turbulence have two disadvantages:

[0006] The inlet cross section needs to be specified, that is, the disturbed velocity field is added in partitions, and the global flow field cannot be predicted;

[0007] The generation of turbulent boundary layer on a flat plate with zero pressure gradient is limited to two dimensions and cannot be applied to the numerical prediction of complex three-dimensional aircraft flows.

[0008] The above two shortcomings make the inlet turbulence generation method unsuitable for practical engineering applications, and there are still great challenges in the numerical prediction of real complex three-dimensional aircraft flows. Summary of the invention

[0009] The present invention aims to solve one of the technical problems in the related art at least to a certain extent.

[0010] To this end, the purpose of the present invention is to propose a non-partitioned turbulence generation method based on synthetic particle groups for non-partitioned turbulence generation, so as to accurately predict real complex three-dimensional aircraft flows.

[0011] To achieve the above-mentioned purpose, the first embodiment of the present invention proposes a non-partitioned turbulence generation method based on a synthetic particle group, comprising:

[0012] Determine the basic characteristics of the synthetic particle group;

[0013] Setting the injection criteria of the synthetic particle group, including the generation position and the injection algorithm;

[0014] The injection of the synthetic particle group is completed according to the injection criterion, inducing the generation of small-scale turbulent structures.

[0015] In addition, the non-partitioned turbulence generation method based on synthetic particle groups according to the above embodiment of the present invention may also have the following additional technical features:

[0016] Furthermore, in one embodiment of the present invention, determining the basic characteristics of the composite particle group includes:

[0017] Determine the shape, characteristic size, and density of the composite particle group, wherein:

[0018] The shape is described by a kernel function, which is an approximate high and low speed strip flow unit;

[0019] The characteristic scale LSPO is defined as:

[0020] L SPO =Δ max +α(L RANS -Δ max ),α~Υ(0,1),

[0021] Among them, Δmax is the grid scale, which is determined by the computational grid; LRANS is the turbulence scale, which is obtained from the local flow field; α is a random number uniformly distributed between 0 and 1;

[0022] The density is defined as:

[0023] Where Δt is the time step of the calculation, which can be set by the user; V cell is the volume of the grid unit, obtained by calculating the grid; τ SPO is the life cycle of the synthetic particle group, τ SPO =4.0 / ω, ω is the turbulence frequency, determined by the local flow field, V SPO is the volume of a single synthetic particle group.

[0024] Furthermore, in one embodiment of the present invention, the step of setting the injection criteria of the synthetic particle group includes:

[0025] Set the generation position of the synthetic particle group, specifically, the mixing length scale L determined by the local flow field hybrid and turbulent velocity Determine the injection location:

[0026]

[0027] Among them, C u As a constant, take C u =0.04;

[0028] And, a rejection / sampling algorithm is used, which involves traversing each grid for each physical time step and calculating the composite particle group density ρ SPO At the same time, a random number α~Υ(0,1) uniformly distributed between 0 and 1 is generated, and then the random number is combined with the density of the synthetic particle group ρ SPO Compare the size; if the random number is less than ρ SPO , then the synthetic particle group is injected into the grid unit; otherwise, the grid unit is skipped.

[0029] Further, in one embodiment of the present invention, the step of injecting the synthetic particle group according to the injection criterion to induce the generation of a small-scale turbulent structure includes:

[0030] The information of the global synthetic particle group is communicated, the disturbed volume force of each grid unit is calculated, and the NS equation is added to calculate the flow field to obtain the final flow field result.

[0031] Further, in one embodiment of the present invention, the calculating the disturbance volume force of each grid unit includes:

[0032] The part of turbulent energy that can be analyzed in RANS simulation is used to replace the disturbance velocity within the generation period of the synthetic particle group, thereby constructing the shear layer normal velocity v'.

[0033] The turbulent kinetic energy that can be analyzed is:

[0034]

[0035] Then the amplitude of the corresponding normal volume force caused by the composite particle group is:

[0036]

[0037] Combined with the kernel function of the synthetic particle group, the volume force of the synthetic particle group on each grid unit can be obtained as follows:

[0038]

[0039] To achieve the above-mentioned purpose, the second embodiment of the present invention proposes a non-partitioned turbulence generating device based on a synthetic particle group, comprising the following modules:

[0040] an acquisition module for determining basic characteristics of the composite particle group;

[0041] A setting module, used to set the injection criteria of the synthetic particle group, including the generation position and the injection algorithm;

[0042] The injection module is used to complete the injection of the synthetic particle group according to the injection criterion and induce the generation of small-scale turbulent structure.

[0043] Furthermore, in one embodiment of the present invention, the acquisition module is further used to:

[0044] Determine the shape, characteristic size, and density of the composite particle group, wherein:

[0045] The shape is described by a kernel function, which is an approximate high and low speed strip flow unit;

[0046] The characteristic scale LSPO is defined as:

[0047] L SPO =Δ max +α(L RANS -Δ max ),α~Υ(0,1),

[0048] Among them, Δmax is the grid scale, which is determined by the computational grid; LRANS is the turbulence scale, which is obtained from the local flow field; α is a random number uniformly distributed between 0 and 1;

[0049] The density is defined as:

[0050] Where Δt is the time step of the calculation, which can be set by the user; V cell is the volume of the grid unit, obtained by calculating the grid; τ SPOis the life cycle of the synthetic particle group, τ SPO =4.0 / ω, ω is the turbulence frequency, determined by the local flow field, V SPO is the volume of a single synthetic particle group.

[0051] Furthermore, in one embodiment of the present invention, the setting module is further used to:

[0052] Set the generation position of the synthetic particle group, specifically, the mixing length scale L determined by the local flow field hybrid and turbulent velocity Determine the injection location:

[0053]

[0054] Among them, C u As a constant, take C u =0.04;

[0055] And, a rejection / sampling algorithm is used, which involves traversing each grid for each physical time step and calculating the composite particle group density ρ SPO At the same time, a random number α~Υ(0,1) uniformly distributed between 0 and 1 is generated, and then the random number is combined with the density of the synthetic particle group ρ SPO Compare the size; if the random number is less than ρ SPO , then the synthetic particle group is injected into the grid unit; otherwise, the grid unit is skipped.

[0056] Furthermore, in one embodiment of the present invention, the setting module is further used to:

[0057] Communicate the information of the global synthetic particle group, calculate the perturbation volume force of each grid unit, add it into the NS equation for flow field calculation, and obtain the final flow field result;

[0058] The calculation of the disturbance volume force of each grid unit includes:

[0059] The part of turbulent energy that can be analyzed in RANS simulation is used to replace the disturbance velocity in the generation period of the synthetic particle group, so as to construct the shear layer normal velocity v';

[0060] The turbulent kinetic energy that can be analyzed is:

[0061]

[0062] Then the amplitude of the corresponding normal volume force caused by the composite particle group is:

[0063]

[0064] Combined with the kernel function of the synthetic particle group, the volume force of the synthetic particle group on each grid unit can be obtained as follows:

[0065]

[0066] To achieve the above-mentioned purpose, the third aspect of the present invention proposes a computer device, characterized in that it includes a memory, a processor, and a computer program stored in the memory and executable on the processor, and when the processor executes the computer program, it implements the non-partitioned turbulence generation method based on synthetic particle groups as described above.

[0067] The non-partitioned turbulence generation method based on synthetic particle groups proposed in the embodiment of the present invention constructs multi-scale turbulence disturbances according to a multi-scale vortex model, and proposes corresponding specific disturbance application criteria, so as to achieve the effect of inducing the generation of a three-dimensional turbulent boundary layer in a non-partitioned, random, and non-human-intervention manner, so as to solve the problem that the existing inlet turbulence generation method cannot be applied to the numerical prediction of complex three-dimensional aircraft flows, break through the technical bottleneck, and improve the numerical prediction accuracy of complex three-dimensional aircraft flows, providing important support for the structural design of real aircraft. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0069] Figure 1 A schematic flow chart of a non-partitioned turbulence generation method based on a synthetic particle group provided in an embodiment of the present invention;

[0070] Figure 2 A flowchart of a non-partitioned turbulence generation method based on a synthetic particle group provided in an embodiment of the present invention;

[0071] Figure 3 A schematic diagram of a distribution curve of a kernel function selected when describing synthesized particles provided by an embodiment of the present invention;

[0072] Figure 4 A schematic diagram of the structure of a synthetic particle group provided by an embodiment of the present invention;

[0073] Figure 5 A schematic diagram showing an injection position in a synthetic particle group injection criterion provided by an embodiment of the present invention;

[0074] Figure 6 A schematic diagram of a turbulent structure and a turbulent boundary layer induced after injection of a synthetic particle group provided in an embodiment of the present invention;

[0075] Figure 7A schematic diagram for comparing a calculation result using 2.16 million grids and a direct numerical simulation calculation result provided by an embodiment of the present invention;

[0076] Figure 8 A schematic diagram of a three-dimensional turbulent structure that can be obtained after the present invention is applied to a three-dimensional internal flow channel configuration provided by an embodiment of the present invention;

[0077] Fig. 9 A schematic structural diagram of a non-partitioned turbulence generating device based on a synthetic particle group provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0078] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0079] The following describes a non-partitioned turbulence generation method based on a synthetic particle group according to an embodiment of the present invention with reference to the accompanying drawings.

[0080] Figure 1 A schematic flow chart of a non-partitioned turbulence generation method based on a synthetic particle group provided in an embodiment of the present invention.

[0081] like Figure 1 As shown, the non-partitioned turbulence generation method based on synthetic particle groups includes the following steps:

[0082] S101: Determine basic characteristics of the synthetic particle group;

[0083] Further, in one embodiment of the present invention, determining the basic characteristics of the composite particle group includes:

[0084] Determine the shape, characteristic size, and density of the composite particle group, where

[0085] The shape is described by a kernel function, which is an approximate high- and low-speed strip flow unit;

[0086] The characteristic scale LSPO is defined as:

[0087] L SPO =Δ max +α(L RANS -Δ max ),α~Υ(0,1),

[0088] Among them, Δmax is the grid scale, which is determined by the computational grid; LRANS is the turbulence scale, which is obtained from the local flow field; α is a random number uniformly distributed between 0 and 1;

[0089] Density is defined as:

[0090] Where Δt is the time step of the calculation, which can be set by the user; V cell is the volume of the grid unit, obtained by calculating the grid; τ SPO is the life cycle of the synthetic particle group, τ SPO =4.0 / ω, ω is the turbulence frequency, determined by the local flow field, V SPO is the volume of a single synthetic particle group.

[0091] Specifically, the shape of the synthetic particle group is mainly described by the kernel function. In order to approximate the high- and low-speed strip flow units, multiple scales need to be considered. Therefore, a local orthogonal coordinate system Ofst is first established locally: the local velocity direction u, the vortex vector direction Ω and its cross product direction are selected respectively.

[0092] n f ||u,n s ||Ω,n t =n f ×n s ,

[0093] Three orthogonal kernel functions are selected and constructed through Cartesian product:

[0094]

[0095] Among them, r represents the spatial position vector, and L represents the characteristic scale in each direction.

[0096] The f method and the kernel function in the t direction use the super Gaussian distribution function, and the kernel function in the s direction uses the Ricker wavelet basis function, that is:

[0097]

[0098]

[0099] The kernel function that finally describes the composite particle group is:

[0100]

[0101] Considering the multi-scale characteristics of turbulence, the characteristic scale L of the synthetic particle group SPO It is defined by the following formula:

[0102] L SPO =Δ max +α(L RANS -Δ max ),α~Υ(0,1),

[0103] Among them, Δmax is the grid scale, which is determined by the computational grid; L RANS is the turbulence scale, obtained from the local flow field; α is a random number uniformly distributed between 0 and 1.

[0104] The characteristic scales in the three directions can be obtained:

[0105] L f =2.0L SPO ,L s =1.0L SPO ,L t =0.7L SPO .

[0106] After determining the kernel function and characteristic scale describing the synthetic particle group, the structure of the synthetic particle group can be obtained.

[0107] The synthetic particle group is generated randomly, so it is necessary to determine the density of the synthetic particle group, that is, the generation probability. For simplicity, the volume of a single synthetic particle group is defined by the following formula:

[0108] V SPO =2L f ×2L t ×8L s ,

[0109] In any grid cell, the spatial density of the composite particle group is:

[0110]

[0111] The density in the time direction is the same, so the density of the final composite particle group is:

[0112]

[0113] Where Δt is the time step of the calculation, which can be set by the user; V cell is the volume of the grid unit, obtained by calculating the grid; τ SPO is the life cycle of the synthetic particle group, τ SPO =4.0 / ω, ω is the turbulence frequency, determined by the local flow field.

[0114] S102: Setting injection criteria for the synthetic particle group, including generation position and injection algorithm;

[0115] The injection criteria of the synthetic particle group of the present invention are significantly different from the existing inlet turbulence generation method. This injection criterion can make the addition of the synthetic particle group applicable to the global flow field, not limited to the inlet cross section, and has a non-partitioned characteristic; and the injection algorithm of the present invention can adapt to any grid. Compared with the limitation that the existing inlet turbulence method is only applicable to two-dimensional / quasi-three-dimensional calculations, the present invention can be used for high-precision unsteady numerical prediction of complex three-dimensional models.

[0116] Furthermore, in one embodiment of the present invention, setting the injection criteria of the synthetic particle group includes:

[0117] Set the generation position of the synthetic particle group, specifically, the mixing length scale L determined by the local flow field hybrid and turbulent velocity Determine the injection location:

[0118]

[0119] Among them, C u As a constant, take C u =0.04;

[0120] The velocity index is only used to exclude the far field and irrotational zone in the non-boundary layer area, and the scale index plays the main screening role. When the hybrid length scale Lhybrid is larger than the grid scale, that is, when the local flow field meets the requirements for resolving the turbulent structure, the synthetic particle group begins to be injected into the boundary layer and applies disturbances to promote the switching of RANS to LES mode; when switching to LES mode, the turbulent structure can be resolved, the hybrid length scale Lhybrid will also decrease, the scale index becomes invalid, and the synthetic particle group is no longer injected.

[0121] And, a rejection / sampling algorithm is used, which involves traversing each grid for each physical time step and calculating the composite particle group density ρ SPO At the same time, a random number α~γ(0,1) uniformly distributed between 0 and 1 is generated, and then the random number is combined with the density of the synthetic particle group ρ SPO Compare the size; if the random number is less than ρ SPO , then the synthetic particle group is injected into the grid unit; otherwise, the grid unit is skipped. By breaking the whole into parts, the synthetic particle group is evenly distributed in any control volume according to a given density. The algorithm is local and applicable to any grid, and it minimizes human intervention and achieves random generation of synthetic particle groups.

[0122] S103: completing the injection of the synthetic particle group according to the injection criteria, inducing the generation of small-scale turbulent structures.

[0123] Further, in one embodiment of the present invention, the injection of the synthetic particle group is completed according to the injection criterion to induce the generation of the small-scale turbulent structure, including:

[0124] The information of the global synthetic particle group is communicated, the disturbed volume force of each grid unit is calculated, and the NS equation is added to calculate the flow field to obtain the final flow field result.

[0125] Specifically, by adding a virtual volume force to the NS equations to induce the corresponding velocity field, the original flow field is less disturbed and the noise pollution caused by the synthetic turbulence can be significantly reduced. Only the normal velocity v' of the shear layer is constructed, and the disturbance component of other methods will be quickly established through the instability process and the redistribution mechanism such as the tilting and stretching of the vortex.

[0126] Furthermore, in one embodiment of the present invention, calculating the disturbance body force of each grid unit includes:

[0127] The part of turbulent energy that can be analyzed in RANS simulation is used to replace the disturbance velocity in the generation period of the synthetic particle group, so as to construct the shear layer normal velocity v';

[0128] The turbulent kinetic energy that can be analyzed is:

[0129]

[0130] Then the amplitude of the corresponding normal volume force caused by the composite particle group is:

[0131]

[0132] Combined with the kernel function of the synthetic particle group, the volume force of the synthetic particle group on each grid unit can be obtained as follows:

[0133]

[0134] In order to balance the turbulent kinetic energy, additional source terms need to be added to the modeled turbulent kinetic energy transport equation:

[0135]

[0136] In order to illustrate the specific implementation of the present invention in the algorithm and calculation flow field, a calculation flow chart is given, such as Figure 2 The main steps are as follows:

[0137] 1) Calculate the turbulence scale LRANS and grid scale Δmax from the local flow field and grid to obtain the characteristic scales of the synthetic particle group;

[0138] 2) Through a specific kernel function (see Figure 3 ), the shape of the composite particle group can be described according to the calculated characteristic scale, which is similar to a high- and low-speed strip flow unit, such as Figure 4 As shown;

[0139] 3) The density ρ of the synthetic particle group is calculated from the volume of the synthetic particle group, the volume of the grid unit, the time step, etc. SPO ;

[0140] 4) The mixing length scale and turbulent velocity are calculated from the local flow field, and then the injection position criterion of the synthetic particle group is set; if both the length criterion and the velocity criterion are satisfied, it means that the grid cell is an area where the synthetic particle group can be injected (the injection position is mainly located on the RANS-LES interface, such as Figure 5 shown);

[0141] 5) Within the grid points that meet the injection position criterion, execute the rejection / sampling algorithm: generate a random number α, and then compare it with the density ρ of the synthetic particle group SPO Compare the size, if the random number α is less than ρ SPO , then the synthetic particle group is injected into the grid unit, otherwise the synthetic particle group is not injected into the grid unit;

[0142] 6) Repeat steps (1) to (5) until all grid cells are traversed and the injection of the synthetic particle group in the entire field is completed;

[0143] 7) Communicate the information of the global synthetic particle group, calculate the disturbed volume force of each grid unit, add it into the NS equation for flow field calculation, and obtain the final flow field result.

[0144] Depend on Figure 6 It can be seen that after the synthetic particle group is obtained from each local flow field variable and injected into the appropriate area, turbulent disturbance will be imposed in the flow field, inducing small-scale turbulent structure from the clean boundary layer flow, and developing into a turbulent boundary layer. Compared with the calculation results of direct numerical simulation (DNS), it can be seen that the turbulent boundary layer results obtained by this technical solution are accurate, such as Figure 7 As shown (DNS results can be used as reference data in CFD calculations and are considered accurate). Figure 8 It shows that the present invention can be used for turbulence generation in three-dimensional configurations, solving the problem that the prior art cannot be applied to high-precision numerical prediction of flows in three-dimensional complex configurations.

[0145] The non-partitioned turbulence generation method based on synthetic particle groups proposed in the embodiment of the present invention constructs multi-scale turbulence disturbances according to a multi-scale vortex model, and proposes corresponding specific disturbance application criteria, so as to achieve the effect of inducing the generation of a three-dimensional turbulent boundary layer in a non-partitioned, random, and non-human-intervention manner, so as to solve the problem that the existing inlet turbulence generation method cannot be applied to the numerical prediction of complex three-dimensional aircraft flows, break through the technical bottleneck, and improve the numerical prediction accuracy of complex three-dimensional aircraft flows, providing important support for the structural design of real aircraft.

[0146] Compared with the prior art, the advantages of the present invention are:

[0147] 1) For the injection criteria of the synthetic particle group, the technical solution of the present invention abandons the inlet cross section of the prior art, adopts the local scale criterion and speed criterion, allows the synthetic particle group to be automatically generated and injected in the appropriate area, without human intervention, and has non-partition characteristics, so that the present invention can be applied to the global flow numerical simulation of the aircraft, and can greatly reduce the number of calculation grids, improve the calculation efficiency, and greatly improve the engineering application capability; after testing, the calculation result of 2.16 million grids obtained by the present technical solution is comparable to the result of direct numerical simulation using 3 billion grids, and is better than the result of direct numerical simulation using 40 million grids, such as Figure 7 shown.

[0148] 2) The present invention adopts a multi-directional kernel function to construct a synthetic particle group, so that it has multi-scale three-dimensional characteristics, and adopts a rejection / sampling algorithm, so that the present invention is applicable to any grid, which solves the problem that the existing inlet turbulence generation method cannot be applied to the numerical prediction of complex three-dimensional aircraft flow, and breaks through the technical bottleneck.

[0149] 3) The application of the present invention can improve the numerical prediction accuracy of quasi-three-dimensional and complex three-dimensional configuration flows, provide important support for the structural design of complex engineering models, and control the prediction error of local separation scale, heat flow distribution, etc. within 25%.

[0150] In order to implement the above-mentioned embodiments, the present invention further proposes a non-partitioned turbulence generating device based on a synthetic particle group.

[0151] Fig. 9 A schematic structural diagram of a non-partitioned turbulence generating device based on a synthetic particle group provided in an embodiment of the present invention.

[0152] like Fig. 9 As shown, the non-partitioned turbulence generating device based on the synthetic particle group includes: an acquisition module 100, a setting module 200, and an injection module 300, wherein:

[0153] an acquisition module for determining basic characteristics of the composite particle group;

[0154] A setting module, used to set the injection criteria of the synthetic particle group, including the generation position and the injection algorithm;

[0155] The injection module is used to complete the injection of synthetic particle groups according to the injection criteria to induce the generation of small-scale turbulent structures.

[0156] Furthermore, in one embodiment of the present invention, the acquisition module is further used to:

[0157] Determine the shape, characteristic size, and density of the composite particle group, where

[0158] The shape is described by a kernel function, which is an approximate high- and low-speed strip flow unit;

[0159] The characteristic scale LSPO is defined as:

[0160] L SPO =Δ max +α(L RANS -Δ max ),α~γ(0,1),

[0161] Among them, Δmax is the grid scale, which is determined by the computational grid; LRANS is the turbulence scale, which is obtained from the local flow field; α is a random number uniformly distributed between 0 and 1;

[0162] Density is defined as:

[0163] Where Δt is the time step of the calculation, which can be set by the user; V cell is the volume of the grid unit, obtained by calculating the grid; τ SPO is the life cycle of the synthetic particle group, τ SPO =4.0 / ω, ω is the turbulence frequency, determined by the local flow field, V SPO is the volume of a single synthetic particle group.

[0164] Furthermore, in one embodiment of the present invention, the setting module is also used to:

[0165] Set the generation position of the synthetic particle group, specifically, the mixing length scale L determined by the local flow field hybrid and turbulent velocity Determine the injection location:

[0166]

[0167] Among them, C u As a constant, take C u =0.04;

[0168] And, a rejection / sampling algorithm is used, which involves traversing each grid for each physical time step and calculating the composite particle group density ρ SPO At the same time, a random number α~γ(0,1) uniformly distributed between 0 and 1 is generated, and then the random number is combined with the density of the synthetic particle group ρ SPO Compare the size; if the random number is less than ρ SPO , then the synthetic particle group is injected into the grid unit; otherwise, the grid unit is skipped.

[0169] Furthermore, in one embodiment of the present invention, the setting module is also used to:

[0170] Communicate the information of the global synthetic particle group, calculate the perturbation volume force of each grid unit, add it into the NS equation for flow field calculation, and obtain the final flow field result;

[0171] The calculation of the disturbance volume force of each grid unit includes:

[0172] The part of turbulent energy that can be analyzed in RANS simulation is used to replace the disturbance velocity in the generation period of the synthetic particle group, so as to construct the shear layer normal velocity v';

[0173] The turbulent kinetic energy that can be analyzed is:

[0174]

[0175] Then the amplitude of the corresponding normal volume force caused by the composite particle group is:

[0176]

[0177] Combined with the kernel function of the synthetic particle group, the volume force of the synthetic particle group on each grid unit can be obtained as follows:

[0178]

[0179] To achieve the above-mentioned purpose, the third aspect of the present invention proposes a computer device, characterized in that it includes a memory, a processor, and a computer program stored in the memory and executable on the processor, and when the processor executes the computer program, it implements the non-partitioned turbulence generation method based on synthetic particle groups as described above.

[0180] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0181] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0182] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A non-partitioned turbulence generation method based on synthetic particle groups, characterized in that: The following steps are involved: Determine the basic characteristics of the synthetic particle group; Setting the injection criteria of the synthetic particle group, including the generation position and the injection algorithm; Injecting the synthetic particle group according to the injection criterion to induce the generation of small-scale turbulent structures; Wherein, the basic characteristics of the composite particle group are determined, including: Determine the shape, characteristic size, and density of the composite particle group, wherein: The shape is described by a kernel function, which is an approximate high and low speed strip flow unit; The characteristic scale LSPO is defined as: L SPO =D max +α(L RANS -D max ),α~γ(0,1), Among them, Δmax is the grid scale, which is determined by the computational grid; LRANS is the turbulence scale, which is obtained from the local flow field; α is a random number uniformly distributed between 0 and 1; The density is the generation probability, and the density is defined as: Where Δt is the time step of the calculation, which can be set by the user; V cell is the volume of the grid unit, obtained by calculating the grid; τ SPO is the life cycle of the synthetic particle group, τ SPO =4.0 / ω, ω is the turbulence frequency, determined by the local flow field, V SPO is the volume of a single composite particle group, V SPO =2L f ×2L t ×8L s , L f =2.0L SPO ,L s =1.0L SPO ,L t =0.7L SPO , establish a local orthogonal coordinate system Ofst locally, select the local velocity direction, vortex vector direction and its cross product direction, L f , L t , L s represent the characteristic scales in the f, t, and s directions, respectively; The step of setting the injection criteria of the synthetic particle group comprises: Set the generation position of the synthetic particle group, specifically, the mixing length scale L determined by the local flow field hybrid and turbulent velocity Determine the injection location: Among them, C u As a constant, take C u =0.04; And, within the grid points that meet the injection position criterion, a rejection / sampling algorithm is used, which involves traversing each grid for each physical time step and calculating the composite particle group density ρ SPO At the same time, a random number α~γ(0,1) uniformly distributed between 0 and 1 is generated, and then the random number is combined with the density of the synthetic particle group ρ SPO Compare the size; if the random number is less than ρ SPO , then the synthetic particle group is injected into the grid unit; otherwise, the grid unit is skipped.

2. The method according to claim 1, characterized in that The step of completing the injection of the synthetic particle group according to the injection criterion to induce the generation of a small-scale turbulent structure comprises: The information of the global synthetic particle group is communicated, the disturbed volume force of each grid unit is calculated, and the NS equation is added to calculate the flow field to obtain the final flow field result.

3. The method according to claim 2, characterized in that The calculation of the disturbance volume force of each grid unit includes: The part of turbulent energy that can be analyzed in RANS simulation is used to replace the disturbance velocity in the generation period of the synthetic particle group, so as to construct the shear layer normal velocity v'; The turbulent kinetic energy that can be analyzed is: Then the amplitude of the corresponding normal volume force caused by the composite particle group is: Combined with the kernel function of the synthetic particle group, the volume force of the synthetic particle group on each grid unit can be obtained as follows:

4. A non-partitioned turbulence generating device based on a synthetic particle group, characterized in that: Includes the following modules: an acquisition module for determining basic characteristics of the composite particle group; A setting module, used to set the injection criteria of the synthetic particle group, including the generation position and the injection algorithm; An injection module, used to complete the injection of the synthetic particle group according to the injection criterion, and induce the generation of small-scale turbulent structures; Wherein, the acquisition module is also used for: Determine the shape, characteristic size, and density of the composite particle group, wherein: The shape is described by a kernel function, which is an approximate high and low speed strip flow unit; The characteristic scale LSPO is defined as: L SPO =D max +α(L RANS -D max ),α~γ(0,1), Among them, Δmax is the grid scale, which is determined by the computational grid; LRANS is the turbulence scale, which is obtained from the local flow field; α is a random number uniformly distributed between 0 and 1; The density is the generation probability, and the density is defined as: Where Δt is the time step of the calculation, which can be set by the user; V cell is the volume of the grid unit, obtained by calculating the grid; τ SPO is the life cycle of the synthetic particle group, τ SPO =4.0 / ω, ω is the turbulence frequency, determined by the local flow field, V SPO is the volume of a single composite particle group, V SPO is the volume of a single composite particle group, V SPO =2L f ×2L t ×8L s , L f =2.0L SPO ,L s =1.0L SPO ,L t =0.7L SPO , establish a local orthogonal coordinate system Ofst locally, select the local velocity direction, vortex vector direction and its cross product direction, L f , L t , L s represent the characteristic scales in the f, t, and s directions respectively; The setting module is also used for: Set the generation position of the synthetic particle group, specifically, the mixing length scale L determined by the local flow field hybrid and turbulent velocity Determine the injection location: Among them, C u As a constant, take C u =0.04; And, within the grid points that meet the injection position criterion, a rejection / sampling algorithm is used, which involves traversing each grid for each physical time step and calculating the composite particle group density ρ SPO At the same time, a random number α~γ(0,1) uniformly distributed between 0 and 1 is generated, and then the random number is combined with the density of the synthetic particle group ρ SPO Compare the size; if the random number is less than ρ SPO , then the synthetic particle group is injected into the grid unit; otherwise, the grid unit is skipped.

5. The device according to claim 4, characterized in that The setting module is also used for: Communicate the information of the global synthetic particle group, calculate the perturbation volume force of each grid unit, add it into the NS equation for flow field calculation, and obtain the final flow field result; The calculation of the disturbance volume force of each grid unit includes: The part of turbulent energy that can be analyzed in RANS simulation is used to replace the disturbance velocity in the generation period of the synthetic particle group, so as to construct the shear layer normal velocity v'; The turbulent kinetic energy that can be analyzed is: Then the amplitude of the corresponding normal volume force caused by the composite particle group is: Combined with the kernel function of the synthetic particle group, the volume force of the synthetic particle group on each grid unit can be obtained as follows:

6. A computer device, characterized in that: The method comprises a memory, a processor and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the method for generating non-partitioned turbulence based on a synthetic particle group as described in any one of claims 1 to 3 is implemented.

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