Turbulence kinetic energy characteristic extraction method and system

Abstract

The invention relates to a turbulent flow kinetic energy characteristic extraction method and system, and the method comprises the steps: setting a boundary condition for a computational domain of high-speed turbulent flow on a high-speed aircraft based on the type of the high-speed turbulent flow on the high-speed aircraft and the applied active flow control; based on the boundary condition of the computational domain, performing iterative computation through a Navier-Stokes equation to obtain a flow field variable instantaneous quantity of each flow field physical variable; and on the basis of the flow field variable instantaneous quantity of the flow field physical variable, each turbulent energy characteristic item in the turbulent energy transport equation is calculated, and the turbulent energy characteristic items represent the evolution process of the high-speed turbulent energy. By means of the method and device, high-speed turbulent flow computational domain boundary condition setting based on active flow control is achieved, the high-speed turbulent flow generation, transmission and dissipation processes under active flow control are analyzed, a supersonic flow control friction resistance reduction mechanism can be excavated, and the problem of how to obtain the influence of active flow control on high-speed turbulent flow is solved.

Description

Technical Field

[0001] The present application relates to the field of aircraft aerodynamic design, and in particular to a method and system for extracting turbulent kinetic energy characteristics. Background Art

[0002] Applying active flow control on the surface of a high-speed aircraft can reduce flight resistance. For example, applying blowing / inhaling control on the surface of a supersonic aircraft can effectively reduce the aerodynamic friction resistance of the aircraft. Therefore, understanding the mechanism of friction drag reduction of supersonic airflow controlled by blowing / inhaling is very important for the formulation of blowing / inhaling control strategies. However, since the evolution process of supersonic turbulent structure is very complex, it may involve typical flow field structures such as large and small scale vortices, near-wall strips, and unsteady shock waves, which makes it more difficult to understand the mechanism of supersonic turbulent drag reduction.

[0003] Currently, no effective solution has been proposed for how to obtain the effect of active flow control on high-speed turbulence in related technologies. Summary of the invention

[0004] The embodiments of the present application provide a method and system for extracting turbulent kinetic energy characteristics, so as to at least solve the problem in the related art of how to obtain the influence of active flow control on high-speed turbulence.

[0005] In a first aspect, an embodiment of the present application provides a method for extracting turbulent kinetic energy characteristics, the method comprising: Based on the type of high-speed turbulence on the high-speed aircraft and the applied active flow control, setting boundary conditions for the computational domain of the high-speed turbulence on the high-speed aircraft; Based on the boundary conditions of the computational domain, the instantaneous flow field variables of each flow field physical variable are obtained by performing iterative calculations through the Navier-Stokes equations; Based on the instantaneous quantity of the flow field variables of the flow field physical variables, various turbulent kinetic energy characteristic terms in the turbulent kinetic energy transport equation are calculated, wherein the turbulent kinetic energy characteristic terms characterize the evolution process of high-speed turbulent kinetic energy.

[0006] In some of the embodiments, based on the type of high-speed turbulence on the high-speed aircraft and the applied active flow control, setting boundary conditions for the computational domain of the high-speed turbulence on the high-speed aircraft includes: For a computational domain normal to high-speed turbulence on a high-speed aircraft, setting boundary conditions based on active flow control applied on the high-speed aircraft; For the computational domain flow direction of the high-speed turbulence on the high-speed aircraft, setting boundary conditions based on the type of high-speed turbulence on the high-speed aircraft; For the spanwise direction of the calculation domain of the high-speed turbulence on the high-speed aircraft, the boundary conditions set on the two boundary surfaces in the spanwise direction of the calculation domain are both periodic boundary conditions.

[0007] In some of the embodiments, for the computational domain normal of high-speed turbulence on a high-speed aircraft, setting boundary conditions based on active flow control applied on the high-speed aircraft includes: For the computational domain normal of high-speed turbulence on a high-speed aircraft, if no active flow control is applied on the high-speed aircraft, the boundary conditions set are no-slip and no-penetration wall conditions; If active flow control is applied on the high-speed aircraft, the velocity of the blowing / suction wall in the normal direction of the computational domain is set to:

[0008] in, F Indicates the intensity of blowing or inhaling. ρ bl Indicates the density of blowing or suction, S inlet represents the area of ​​the inlet or periodic surface, It represents the surface integral of the product of density and streamwise velocity at the inlet or periodic surface.

[0009] In some embodiments, for the computational domain flow direction of the high-speed turbulence on the high-speed aircraft, setting boundary conditions based on the type of high-speed turbulence on the high-speed aircraft includes: For the computational domain flow direction of the high-speed turbulence on the high-speed aircraft, if the high-speed turbulence on the high-speed aircraft is channel turbulence or pipe turbulence, the boundary conditions set on the two boundary surfaces of the computational domain flow direction are both periodic boundary conditions; If the high-speed turbulence on the high-speed aircraft is flat-plate turbulence, two boundary surfaces of the flow direction of the calculation domain are respectively set as an inlet and an outlet based on the mainstream direction.

[0010] In some embodiments, based on the instantaneous amount of the flow field variable of the flow field physical variable, each turbulent kinetic energy characteristic term in the turbulent kinetic energy transport equation is calculated to include: Based on the instantaneous amount of the flow field physical variable, the time average amount and density weighted average amount of the flow field physical variable are calculated, wherein the flow field physical variable includes density ρ , flow velocity u , Normal velocity v , spanwise velocity w and temperature T ; Based on the time average and density weighted average of the flow field physical variables, various turbulent kinetic energy characteristic terms in the turbulent kinetic energy transport equation are calculated.

[0011] In some embodiments, based on the instantaneous amount of the flow field physical variable, calculating the time average amount and the density weighted average amount of the flow field physical variable comprises: Select the flow field physical variables in the continuous N The instantaneous amount of the flow field variable at the output time step is output, and the instantaneous amount of the flow field variable is output from 1 to N , and then calculate recursively:

[0012] The physical variables of the flow field are calculated in the continuous N The time average over the output time steps ,in, Indicates n Output time steps ,when n =1, ,when n = N hour, ; It represents the physical variable of the flow field In the n The instantaneous amount of flow field variables at the output time step; In calculating the time average Based on the Favre average volume calculation formula The physical variables of the flow field are calculated in the continuous N The density-weighted average over the output time steps ,in, Indicates density and flow field physical variables The time average of the product, Indicates density The time average.

[0013] In some embodiments, based on the time average and density weighted average of the flow field physical variables, the various turbulent kinetic energy characteristic terms in the turbulent kinetic energy transport equation are calculated to include: Based on the time average and density weighted average of the physical variables of the flow field, the turbulent kinetic energy transport equation is calculated by spatial derivation: The various turbulent kinetic energy characteristic terms in, among which, is the generation term of turbulent kinetic energy, is the diffusion term of the turbulent kinetic energy, is the work done by pressure, is the viscous diffusion term, is the viscous dissipation term, is the stress diffusion term; The turbulent kinetic energy characteristic term is subjected to wall normalization processing to obtain the turbulent kinetic energy characteristic term for direct comparative analysis.

[0014] In some of the embodiments, before setting boundary conditions for a computational domain of high-speed turbulence on the high-speed aircraft based on active flow control applied on the high-speed aircraft, the method includes: A computational domain of supersonic turbulence on a supersonic aircraft is determined, and the computational domain is discretized to obtain a computational domain containing discrete grid points, wherein a computational domain flow direction and a computational domain span direction of the computational domain are discretized using equally spaced grids, and a computational domain normal direction of the computational domain is discretized using a hyperbolic tangent distribution grid.

[0015] In some of the embodiments, the high-speed aircraft is a supersonic aircraft, the high-speed turbulence is supersonic turbulence, and the active flow control is blowing / suction control.

[0016] In a second aspect, an embodiment of the present application provides a turbulent kinetic energy characteristic extraction system, the system is used to execute the method described in the first aspect above, the system includes a condition setting module, an instantaneous quantity calculation module and a characteristic extraction module; The condition setting module is used to set boundary conditions for the calculation domain of high-speed turbulence on the high-speed aircraft according to the type of high-speed turbulence on the high-speed aircraft and the active flow control applied; The instantaneous quantity calculation module is used to perform iterative calculations through the Navier-Stokes equation according to the boundary conditions of the calculation domain to obtain the instantaneous quantity of the flow field variables of each flow field physical variable; The characteristic extraction module is used to calculate various turbulent kinetic energy characteristic terms in the turbulent kinetic energy transport equation according to the instantaneous quantity of the flow field variables of the flow field physical variables, wherein the turbulent kinetic energy characteristic terms characterize the evolution process of high-speed turbulent kinetic energy.

[0017] Compared with the related art, the embodiment of the present application provides a method and system for extracting turbulent kinetic energy characteristics, wherein the method sets boundary conditions for the calculation domain of high-speed turbulence on the high-speed aircraft based on the high-speed turbulence type on the high-speed aircraft and the applied active flow control; based on the boundary conditions of the calculation domain, iterative calculations are performed through the Navier-Stokes equations to obtain the instantaneous quantities of the flow field variables of each flow field physical variable; based on the instantaneous quantities of the flow field variables of the flow field physical variables, each turbulent kinetic energy characteristic term in the turbulent kinetic energy transport equation is calculated, wherein the turbulent kinetic energy characteristic term characterizes the evolution process of high-speed turbulent kinetic energy, realizes the setting of boundary conditions of the high-speed turbulence calculation domain based on active flow control, completes the assembly of each term in the turbulent kinetic energy transport equation, analyzes the process of high-speed turbulence generation, transmission and dissipation under active airflow control, helps to explore the friction drag reduction mechanism of supersonic flow control, and is applied to the aerodynamic design of low-drag aircraft, solving the problem of how to obtain the impact of active flow control on high-speed turbulence. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings: Figure 1 is a flowchart of the steps of the method for extracting turbulent kinetic energy characteristics provided in an embodiment of the present application; Figure 2 is a schematic diagram of a process for extracting turbulent kinetic energy characteristics according to an embodiment of the present application; Figure 3 is the turbulent kinetic energy transport equation according to the specific embodiment of the present application P K Item comparison diagram; Figure 4 is the turbulent kinetic energy transport equation according to the specific embodiment of the present application T K Item comparison diagram; Figure 5 is the turbulent kinetic energy transport equation according to the specific embodiment of the present application II K Item comparison diagram; Figure 6 is the turbulent kinetic energy transport equation according to the specific embodiment of the present application D K Item comparison diagram; Figure 7 is the turbulent kinetic energy transport equation according to the specific embodiment of the present application ε K Item comparison diagram; Figure 8 is the turbulent kinetic energy transport equation according to the specific embodiment of the present applicationM K Item comparison diagram; Fig. 9 It is a schematic diagram of the internal structure of an electronic device according to an embodiment of the present application. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application is described and illustrated below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not intended to limit the present application. Based on the embodiments provided in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present application.

[0020] Obviously, the drawings described below are only some examples or embodiments of the present application. For ordinary technicians in this field, the present application can also be applied to other similar scenarios based on these drawings without creative work. In addition, it can also be understood that although the efforts made in this development process may be complicated and lengthy, for ordinary technicians in this field related to the content disclosed in this application, some changes in design, manufacturing or production based on the technical content disclosed in this application are just conventional technical means, and should not be understood as insufficient content disclosed in this application.

[0021] Reference to "embodiments" in this application means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those of ordinary skill in the art that the embodiments described in this application may be combined with other embodiments without conflict.

[0022] Unless otherwise defined, the technical terms or scientific terms involved in this application should be understood by people with ordinary skills in the technical field to which this application belongs. The words "one", "a", "a", "the" and the like involved in this application do not indicate a quantity limitation, and may indicate the singular or plural. The terms "include", "comprise", "have" and any of their variations involved in this application are intended to cover non-exclusive inclusions; for example, a process, method, system, product or device that includes a series of steps or modules (units) is not limited to the listed steps or units, but may also include steps or units that are not listed, or may also include other steps or units inherent to these processes, methods, products or devices. The words "connect", "connected", "coupled" and the like involved in this application are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The "multiple" involved in this application refers to two or more. "And / or" describes the association relationship of associated objects, indicating that there may be three relationships, for example, "A and / or B" can mean: A exists alone, A and B exist at the same time, and B exists alone. The character " / " generally indicates that the objects before and after are in an "or" relationship. The terms "first", "second", "third", etc. involved in this application are only used to distinguish similar objects and do not represent a specific ordering of the objects.

[0023] The present application embodiment provides a method for extracting turbulent kinetic energy characteristics. Figure 1 is a flowchart of the steps of the method for extracting turbulent kinetic energy characteristics provided in an embodiment of the present application, such as Figure 1 As shown, the method comprises the following steps: Step S102, setting boundary conditions for the calculation domain of high-speed turbulence on the high-speed aircraft based on the type of high-speed turbulence on the high-speed aircraft and the applied active flow control; Step S102 specifically includes the following steps: Step S1021, for the normal direction of the calculation domain of high-speed turbulence on the high-speed aircraft, setting boundary conditions based on active flow control applied on the high-speed aircraft; Step S1022, for the flow direction of the calculation domain of the high-speed turbulence on the high-speed aircraft, setting boundary conditions based on the type of high-speed turbulence on the high-speed aircraft; Specifically, in step S1022, for the computational domain flow direction of high-speed turbulence on a high-speed aircraft, if the high-speed turbulence on the high-speed aircraft is channel turbulence or pipe turbulence, the boundary conditions set on the two boundary surfaces of the computational domain flow direction are both periodic boundary conditions; if the high-speed turbulence on the high-speed aircraft is flat plate turbulence, the two boundary surfaces of the computational domain flow direction are respectively set as the inlet and the outlet based on the mainstream direction.

[0024] Step S1023, for the spanwise direction of the calculation domain of the high-speed turbulence on the high-speed aircraft, the boundary conditions set on the two boundary surfaces in the spanwise direction of the calculation domain are both periodic boundary conditions.

[0025] It should be noted that the boundary conditions set for the two boundary surfaces are both periodic boundary conditions, which means that the flow characteristics in this direction (such as the flow direction of the calculation domain in step S1022 and the span direction of the calculation domain in step S1023) are assumed to be periodic. Specifically, it is assumed that the flow in the span direction of the calculation domain is uniform and infinitely extended, so the flow state on one side of the calculation domain is exactly the same as the flow state on the opposite side. This means that the velocity, pressure, temperature and all other relevant physical quantities are equal on the two opposite boundaries.

[0026] Before step S102, the method also includes step S101, determining the computational domain of supersonic turbulence on a supersonic aircraft, and discretizing the computational domain to obtain a computational domain containing discrete grid points, wherein the computational domain flow direction and the computational domain span direction of the computational domain are discretized using equally spaced grids, and the computational domain normal of the computational domain is discretized using a hyperbolic tangent distribution grid.

[0027] Step S104, based on the boundary conditions of the calculation domain, iterative calculation is performed through the Navier-Stokes equation to obtain the instantaneous value of the flow field variables of each flow field physical variable; Specifically, in step S104, the inviscid term in the Navier-Stokes equation (NS equation) is preferably discretized using the 8th order central difference format, the viscous term is preferably discretized using the 7th order upwind difference format, and the time term is preferably promoted using the 3rd order Runge-Kutta format with TVD properties. At the end of the iterative calculation, the physical variables of the flow field (density ρ , flow velocity u , Normal velocity v , spanwise velocity w and temperature T ) is the instantaneous value of the flow field variables at each output time step, and the file storing the instantaneous value of the flow field variables is named the instantaneous variable file.

[0028] Step S106, based on the instantaneous quantity of the flow field variable of the flow field physical variable, various turbulent kinetic energy characteristic terms in the turbulent kinetic energy transport equation are calculated, wherein the turbulent kinetic energy characteristic terms characterize the evolution process of high-speed turbulent kinetic energy.

[0029] Step S106 specifically includes the following steps: Step S1061, based on the instantaneous amount of the flow field physical variables, the time average amount and the density weighted average amount (Favre average amount) of the flow field physical variables are calculated, wherein the flow field physical variables include density ρ, flow velocity u , Normal velocity v , spanwise velocity w ,temperature T and pressure p ; (It should be noted that in the above step S104, there is no need to calculate the storage pressure p The instantaneous flow field variables, but the physical variables of the flow field include pressure p of) Step S1062, based on the time average and density weighted average of the flow field physical variables, various turbulent kinetic energy characteristic terms in the turbulent kinetic energy transport equation are calculated.

[0030] Specifically, step S1062 calculates each turbulent kinetic energy characteristic term in the turbulent kinetic energy transport equation based on the time average and density weighted average of the flow field physical variables by spatial derivation. The expression of the turbulent kinetic energy transport equation is:

[0031] The two terms on the left side of the equation represent the time and space growth rates of turbulent kinetic energy. is the generation term of turbulent kinetic energy, is the diffusion term of the turbulent kinetic energy, is the work done by pressure, is the viscous diffusion term, is the viscous dissipation term, is the stress diffusion term; The turbulent kinetic energy characteristic term is then wall-normalized to obtain the turbulent kinetic energy characteristic term for direct comparative analysis.

[0032] It should be noted that turbulent kinetic energy (TKE) is a measure of the energy of random motion of fluid in turbulence and is a key quantity in turbulence research. For wall-bounded turbulence, turbulent kinetic energy is of great significance and can help researchers understand and describe the characteristics of turbulence, especially the turbulent structure, energy transfer and flow characteristics in the boundary layer. The expression of turbulent kinetic energy is:

[0033] in, k represents the turbulent kinetic energy, u , v and w Respectively indicate flow direction X , Normal Y and span Z The speed of '' " represents the Favre pulsation quantity. , then the above turbulent kinetic energy expression can be converted to Among them, the subscript j It is a dummy mark (the following formula (2.1) to formula (2.8) i , and equations (2.7) and (2.8) l Similarly), you need to traverse j =1, j =2, j =3 and sum.

[0034] The Turbulent Kinetic Energy Transport Equation is a core equation in turbulence theory, which describes the generation, dissipation, transport of turbulent kinetic energy, and the interaction between turbulence and mean flow. The purpose of studying the turbulent kinetic energy transport equation is to describe the spatial and temporal variations of turbulent energy (i.e., turbulent kinetic energy), including the source, transformation, and transmission process of turbulent kinetic energy. Through the turbulent kinetic energy transport equation, we can better understand the energy distribution in different regions of turbulence, the variation of turbulent intensity, and its relationship with other flow characteristics (such as velocity field and pressure field). For the six terms on the right side of the equal sign in the expression of the above turbulent kinetic energy transport equation, specifically: Item 1 is the generation term of turbulent kinetic energy, which characterizes the generation of turbulent kinetic energy. Its specific expression is: (2.1) Item 2 is the diffusion term of turbulent kinetic energy, which characterizes the diffusion of turbulent kinetic energy caused by the correlation between velocity and density fluctuations. Its specific expression is: (2.2) The third item from the right is the pressure work term, which represents the effect of pressure work on turbulent kinetic energy. Represents pressure, and its specific expression is: (2.3) Item 4 is the viscous diffusion term, which characterizes the transport of turbulent kinetic energy in space caused by viscous stress. Its specific expression is: (2.4) Item 5 is the viscous dissipation term, which characterizes the viscous dissipation caused by turbulent pulsation. Its specific expression is: (2.5) Item 6 is the stress diffusion term, which characterizes the diffusion of the mean flow viscous stress caused by velocity pulsation. Its specific expression is: (2.6) For the fourth, fifth and sixth items above, represents the viscous stress of the mean flow, represents the stress caused by pulsation, represents the fluid viscosity coefficient, and its expressions are: (2.7) (2.8) In equations (2.7) and (2.8), is the Kronecker notation, only when hour, ,otherwise .

[0035] Through the above steps in the embodiment of the present application, the boundary conditions of the high-speed turbulence calculation domain based on active flow control are set, the assembly of each term in the turbulent kinetic energy transport equation is completed, and the process of high-speed turbulence generation, transmission and dissipation under active airflow control is analyzed, which helps to explore the friction drag reduction mechanism of supersonic flow control and is applied to the aerodynamic design of low-drag aircraft, solving the problem of how to obtain the impact of active flow control on high-speed turbulence.

[0036] In some embodiments, the above step S1021 is preferably: Figure 2 is a schematic diagram of a process for extracting turbulent kinetic energy characteristics according to an embodiment of the present application, such as Figure 2 As shown in the figure, for the computational domain normal of high-speed turbulence on a high-speed aircraft, if no active flow control is applied on the high-speed aircraft (such as the blowing / suction intensity is 0), the boundary conditions set are no slip and no wall penetration conditions (wall velocity v bl Set to 0); like Figure 2 As shown in the figure, if active flow control is applied on the high-speed aircraft, the velocity of the blowing / suction wall in the normal direction of the computational domain is v bl Set to:

[0037] in, F Indicates the intensity of blowing or inhaling. ρ bl represents the blowing or suction density (usually obtained by interpolation of points near the wall), S inlet represents the area of ​​the inlet or periodic surface, represents the surface integral of the product of density and streamwise velocity at the inlet (flat plate) or periodic surface (channel and pipe), ρ ∞,NC represents the density of the inlet (plate) or periodic surface (channel and pipe) in the uncontrolled case, u ∞,NC It represents the streamwise velocity at the inlet (flat plate) or periodic surface (channels and pipes) in the uncontrolled case.

[0038] Furthermore, for the case of active flow control on high-speed aircraft, the velocity of the blowing / suction wall in the normal direction of the computational domain is v bl In the program, it is calculated in discrete form, and its discrete form calculation formula is:

[0039] In the formula, N y and N z Represent the number of grid points in the normal direction and span direction respectively, I , J and K Represent the grid point numbers in the flow direction, normal direction and span direction respectively, ρ I=1,J,K Indicates the normal number on the inlet or periodic surface. J The grid points, u I=1,J,K Indicates the spanwise number on the inlet or periodic surface. K Grid points.

[0040] In some embodiments, the above step S1061 preferably selects the flow field physical variable to be continuous. N The instantaneous value of the flow field variable at the output time step is output, and the instantaneous value of the flow field variable is output from 1 to N , and then calculate recursively:

[0041] The physical variables of the flow field are calculated in the continuous N The time average over the output time steps ,in, Indicates n Output time steps ,when n =1, ,when n = N hour, ; It represents the physical variable of the flow field In the n The instantaneous amount of flow field variables at the output time step; Calculating the time average Based on the Favre average volume calculation formula The physical variables of the flow field are calculated in the continuous N The density-weighted average over the output time steps ,in, Indicates density and flow field physical variables The time average of the product, Indicates density The time average.

[0042] It should be noted that in step S1061, continuous N The instantaneous value of the flow field variable at the output time step is obtained by recursive solution. way, it can monitor in real time The value of Whether it converges, and can accelerate convergence when solving the average quantity (time average quantity and density weighted average quantity) of the product of multiple variables in step S1062. In addition, in order to ensure the accuracy of the time average quantity, N The time average value and Favre average value calculated in this step are saved separately in different files, named as time average value file and Favre average value file.

[0043] In some embodiments, the above step S1062 preferably uses the turbulent kinetic energy transport equation The correlation of the six turbulent kinetic energy characteristic terms on the right side of the middle sign can be directly based on the time average of the flow field physical variables ( , , , , and ) and density-weighted average.

[0044] ① In other words, the correlation quantities in the above equations (2.1) to (2.8) can be directly calculated based on the time average quantity and density weighted average quantity obtained in step S1061 by taking spatial partial derivatives. Specifically, these correlation quantities include , in formula (2.6) , in formula (2.7) , and Among them, the average flow viscosity coefficient in formula (2.7) is It can be calculated by Sutherland formula Calculated, among which, is the Reynolds number; , Indicates the reference temperature.

[0045] ② For the remaining relevant quantities in the six turbulent kinetic energy characteristic terms, firstly Calculate the pressure in formula (2.3) p ,in, represents the Mach number; secondly, the time pulsation of the flow field physical variables and the density-weighted pulsation (Favre pulsation) are calculated. The calculation formula for the time pulsation of the flow field physical variables is: The calculation formula of Favre pulsation of flow field physical variables is: ,in, Indicates density ρ , flow velocity u , Normal velocity v , spanwise velocity w ,temperature T ,pressure p and viscosity coefficient μ Any physical variable in; again, based on the obtained time pulsation and density-weighted pulsation, by taking the spatial partial derivatives, solve the equation (2.1) in turn , in formula (2.2) , in formula (2.3) , in formula (2.4) , in formula (2.5) , in formula (2.6) In particular, when calculating the correlation in equations (2.4) and (2.5), we can first calculate In One item, and then calculate the inclusion The time average.

[0046] Based on the relevant quantities in the six turbulent kinetic energy characteristic terms calculated by ①② above, the six terms of the turbulent kinetic energy transport equation are assembled. Specifically, the first term Calculated from the above ① and the value calculated in ② above Multiply them together to get; the second term This is the value calculated in ② above. ; Item 3 This is the value calculated in ② above. ; Item 4 This is the value calculated in ② above. Item 5 This is the value calculated in ② above. Item 6 The calculated value from the above ① And the one calculated in ② above Multiply them and you get:

[0047] Finally, in order to facilitate direct comparative analysis, the six turbulent kinetic energy characteristic terms are wall normalized. Calculate the wall shear stress ,pass Calculate the wall friction velocity ,pass Calculate the wall viscosity scale , where all suffixes are w " all represent the value of the variable at the wall. If the incoming flow temperature is the same as the wall temperature, then . Then we get the unit of length used for dimensionless , speed unit The six turbulent kinetic energy characteristic terms , , , , and Divide by , and the wall normalized turbulent kinetic energy characteristic terms are obtained respectively. At the same time, the normalized normal height of the wall is obtained and speed .

[0048] After normalizing the wall By deriving and comparing the turbulent kinetic energy characteristic terms, the process of supersonic turbulence generation, transmission and dissipation under blowing / inhaling control can be analyzed, which helps to explore the friction and drag reduction mechanism of supersonic flow control and apply it to the aerodynamic design of low-drag aircraft.

[0049] In some embodiments, the above step S101 is preferably as follows: Figure 2 As shown in the figure, determine the computational domain and discretize the computational domain space into grid points (a rectangular computational domain can be selected, and the lengths of the computational domain in the flow direction, normal direction, and span direction are L x , L y and L z ), calculation domain flow direction X and the computational domain span Z Use equally spaced grids for discretization; the normal of the computational domain Y The hyperbolic tangent distribution grid is used for discretization. The expression for discretization of the hyperbolic tangent distribution grid is:

[0050] In the formula, J Indicates the sequence number of the normal grid point, y J Indicates J The normal height of a grid point,N y is the number of normal meshes; b g It is used to ensure the normal height of the wall of the first layer of mesh after normalization y + Parameters <1.

[0051] The specific embodiment of the present application improves a method for extracting turbulent kinetic energy characteristics, through which the generation, diffusion, pressure transport, viscous stress diffusion, viscous dissipation and other evolution processes of supersonic turbulent kinetic energy can be clearly displayed. In addition, by comparing the change law of turbulent kinetic energy characteristics before and after blowing / inhaling control is applied under different supersonic incoming flow Mach numbers, the friction drag reduction mechanism of blowing / inhaling flow control can be revealed.

[0052] The Mach numbers are , Uncontrolled working conditions and blowing / suction intensity Taking the working condition as an example, the various terms of the turbulent kinetic energy transport equation after normalization of the wall are compared and displayed.

[0053] Figure 3 is the turbulent kinetic energy transport equation according to the specific embodiment of the present application P K Item comparison diagram, Figure 4 is the turbulent kinetic energy transport equation according to the specific embodiment of the present application T K Item comparison diagram, Figure 5 is the turbulent kinetic energy transport equation according to the specific embodiment of the present application II K Item comparison diagram, Figure 6 is the turbulent kinetic energy transport equation according to the specific embodiment of the present application D K Item comparison diagram, Figure 7 is the turbulent kinetic energy transport equation according to the specific embodiment of the present application ε K Item comparison diagram, Figure 8 is the turbulent kinetic energy transport equation according to the specific embodiment of the present application M K Item comparison diagram, by comparing Figures 3 to 8 , we can draw some conclusions about the effect of blowing / inhaling on the turbulent kinetic energy characteristics: Before applying blowing / inhaling, the peak value of the turbulent kinetic energy generation term is the same, but the larger the Mach number, the larger the dimensionless normal height of the peak value. Applying blowing / inhaling does not change the position of the peak value, but as the Mach number increases, the peak value changes more. This shows that when applying the same blowing / inhaling intensity, the higher the Mach number, the more it can promote the generation of turbulent kinetic energy.

[0054] Before blowing / inhaling, the larger the Mach number, the larger the dissipation term of turbulent kinetic energy. After blowing / inhaling, the difference in turbulent kinetic energy dissipation caused by Mach number is significantly amplified.

[0055] In the viscous sub-region ( ), the diffusion caused by viscous stress promotes the growth of turbulent kinetic energy; in the buffer zone ( ), the effect of diffusion caused by viscous stress on turbulent kinetic energy gradually changes from promoting growth to weakening; in the logarithmic region ( ), the effect of diffusion caused by viscous stress on turbulent kinetic energy gradually disappears.

[0056] In some of the embodiments, the high-speed aircraft in the above embodiments is preferably a supersonic aircraft, the high-speed turbulence is preferably supersonic turbulence, and the active flow control is preferably blowing / suction control.

[0057] It should be noted that the steps shown in the above process or the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and although a logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0058] The embodiment of the present application provides a turbulent kinetic energy characteristic extraction system, which includes a condition setting module, an instantaneous quantity calculation module and a characteristic extraction module; A condition setting module, used to set boundary conditions for the computational domain of high-speed turbulence on the high-speed aircraft according to the type of high-speed turbulence on the high-speed aircraft and the active flow control applied; The instantaneous quantity calculation module is used to perform iterative calculations through the Navier-Stokes equation according to the boundary conditions of the calculation domain to obtain the instantaneous quantity of the flow field variables of each flow field physical variable; The characteristic extraction module is used to calculate various turbulent kinetic energy characteristic terms in the turbulent kinetic energy transport equation according to the instantaneous quantity of the flow field variables of the flow field physical variables, wherein the turbulent kinetic energy characteristic terms characterize the evolution process of high-speed turbulent kinetic energy.

[0059] Through the condition setting module, instantaneous quantity calculation module and characteristic extraction module in the embodiment of the present application, the boundary condition setting of the high-speed turbulence calculation domain based on active flow control is realized, the assembly of each term in the turbulent kinetic energy transport equation is completed, and the process of high-speed turbulence generation, transmission and dissipation under active airflow control is analyzed, which helps to explore the friction drag reduction mechanism of supersonic flow control and is applied to the aerodynamic design of low-drag aircraft, solving the problem of how to obtain the impact of active flow control on high-speed turbulence.

[0060] It should be noted that the above modules can be functional modules or program modules, and can be implemented by software or hardware. For modules implemented by hardware, the above modules can be located in the same processor; or the above modules can be located in different processors in any combination.

[0061] This embodiment further provides an electronic device, including a memory and a processor, wherein a computer program is stored in the memory, and the processor is configured to run the computer program to execute the steps in any one of the above method embodiments.

[0062] Optionally, the electronic device may further include a transmission device and an input / output device, wherein the transmission device is connected to the processor, and the input / output device is connected to the processor.

[0063] It should be noted that the specific examples in this embodiment can refer to the examples described in the above embodiments and optional implementation modes, and this embodiment will not be described in detail here.

[0064] In addition, in combination with the turbulent kinetic energy characteristics extraction method in the above embodiment, the embodiment of the present application can provide a storage medium for implementation. The storage medium stores a computer program; when the computer program is executed by a processor, any one of the turbulent kinetic energy characteristics extraction methods in the above embodiment is implemented.

[0065] In one embodiment, a computer device is provided, which may be a terminal. The computer device includes a processor, a memory, a network interface, a display screen, and an input device connected via a system bus. The processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The network interface of the computer device is used to communicate with an external terminal via a network connection. When the computer program is executed by the processor, a method for extracting turbulent kinetic energy characteristics is implemented. The display screen of the computer device may be a liquid crystal display screen or an electronic ink display screen, and the input device of the computer device may be a touch layer covering the display screen, or a key, trackball, or touchpad provided on the housing of the computer device, or an external keyboard, touchpad, or mouse, etc.

[0066] In one embodiment, Fig. 9 is a schematic diagram of the internal structure of an electronic device according to an embodiment of the present application, such as Fig. 9 As shown, an electronic device is provided, which may be a server, and its internal structure diagram may be as shown in Fig. 9As shown. The electronic device includes a processor, a network interface, an internal memory and a non-volatile memory connected through an internal bus, wherein the non-volatile memory stores an operating system, a computer program and a database. The processor is used to provide computing and control capabilities, the network interface is used to communicate with an external terminal through a network connection, the internal memory is used to provide an environment for the operation of the operating system and the computer program, the computer program is executed by the processor to implement a method for extracting turbulent kinetic energy characteristics, and the database is used to store data.

[0067] Those skilled in the art will understand that Fig. 9 The structure shown in the figure is merely a block diagram of a partial structure related to the scheme of the present application, and does not constitute a limitation on the electronic device to which the scheme of the present application is applied. The specific electronic device may include more or fewer components than shown in the figure, or combine certain components, or have a different arrangement of components.

[0068] Those of ordinary skill in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, storage, database or other media used in the embodiments provided in this application may include non-volatile and / or volatile memory. Non-volatile memory may include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM) or flash memory. Volatile memory may include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in many forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link (Synchlink) DRAM (SLDRAM), memory bus (Rambus) direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM), etc.

[0069] Those skilled in the art should understand that the technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0070] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A method for extracting turbulent kinetic energy characteristics, characterized in that: The method comprises: Based on the type of high-speed turbulence on the high-speed aircraft and the applied active flow control, setting boundary conditions for the computational domain of the high-speed turbulence on the high-speed aircraft; Based on the boundary conditions of the computational domain, the instantaneous flow field variables of each flow field physical variable are obtained by performing iterative calculations through the Navier-Stokes equations; Based on the instantaneous quantity of the flow field variables of the flow field physical variables, various turbulent kinetic energy characteristic terms in the turbulent kinetic energy transport equation are calculated, wherein the turbulent kinetic energy characteristic terms characterize the evolution process of high-speed turbulent kinetic energy.

2. The method according to claim 1, characterized in that Based on the high-speed turbulence type on the high-speed aircraft and the applied active flow control, the boundary conditions for the calculation domain of the high-speed turbulence on the high-speed aircraft are set as follows: For the computational domain normal of high-speed turbulence on a high-speed aircraft, if no active flow control is applied on the high-speed aircraft, the boundary conditions set are no-slip and no-penetration wall conditions; If active flow control is applied on the high-speed aircraft, the velocity of the blowing / suction wall in the normal direction of the computational domain is set to: in, F Indicates the intensity of blowing or inhaling. ρ bl Indicates the density of blowing or suction, S inlet represents the area of ​​the inlet or periodic surface, It represents the surface integral of the product of density and streamwise velocity at the inlet or periodic surface.

3. The method according to claim 1, characterized in that Based on the instantaneous amount of the flow field variables of the flow field physical variables, the various turbulent kinetic energy characteristic terms in the turbulent kinetic energy transport equation are calculated to include: Select the flow field physical variables in the continuous N The instantaneous amount of the flow field variable at the output time step is output, and the instantaneous amount of the flow field variable is output from 1 to N The sorting is then calculated recursively: The physical variables of the flow field are calculated in the continuous N The time average over the output time steps ,in, Indicates n Output time steps ,when n =1, ,when n = N hour, ; It represents the physical variable of the flow field In the n The instantaneous amount of flow field variables at the output time step; In calculating the time average Based on the Favre average volume calculation formula The physical variables of the flow field are calculated in the continuous N The density-weighted average over the output time steps ,in, Indicates density and flow field physical variables The time average of the product, Indicates density The time average of Based on the time average and density weighted average of the flow field physical variables, various turbulent kinetic energy characteristic terms in the turbulent kinetic energy transport equation are calculated.

4. The method according to claim 3, characterized in that Based on the time average and density weighted average of the flow field physical variables, the various turbulent kinetic energy characteristic terms in the turbulent kinetic energy transport equation are calculated to include: Based on the time average and density weighted average of the physical variables of the flow field, the turbulent kinetic energy transport equation is calculated by spatial derivation: The various turbulent kinetic energy characteristic terms in, among which, is the generation term of turbulent kinetic energy, is the diffusion term of the turbulent kinetic energy, is the work done by pressure, is the viscous diffusion term, is the viscous dissipation term, is the stress diffusion term; The turbulent kinetic energy characteristic term is subjected to wall normalization processing to obtain the turbulent kinetic energy characteristic term for direct comparative analysis.

5. A turbulent kinetic energy characteristics extraction system, characterized in that: The system is used to execute the method according to any one of claims 1 to 4, and the system comprises a condition setting module, an instantaneous quantity calculation module and a characteristic extraction module; The condition setting module is used to set boundary conditions for the calculation domain of high-speed turbulence on the high-speed aircraft according to the type of high-speed turbulence on the high-speed aircraft and the active flow control applied; The instantaneous quantity calculation module is used to perform iterative calculations through the Navier-Stokes equation according to the boundary conditions of the calculation domain to obtain the instantaneous quantity of the flow field variables of each flow field physical variable; The characteristic extraction module is used to calculate various turbulent kinetic energy characteristic terms in the turbulent kinetic energy transport equation according to the instantaneous quantity of the flow field variables of the flow field physical variables, wherein the turbulent kinetic energy characteristic terms characterize the evolution process of high-speed turbulent kinetic energy.

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