A method and system for extracting turbulent kinetic energy characteristics

Abstract

The present application relates to a method and system for extracting turbulent kinetic energy characteristics. The method includes: setting boundary conditions for the computational domain of high-speed turbulence on a high-speed aircraft based on the type of high-speed turbulence on the high-speed aircraft and the applied active flow control; performing iterative calculations through the Navier-Stokes equations based on the boundary conditions of the computational domain to obtain the instantaneous flow field variables of each flow field physical variable; calculating each turbulent kinetic energy characteristic term in the turbulent kinetic energy transport equation based on the instantaneous flow field variables of the flow field physical variables, where the turbulent kinetic energy characteristic term characterizes the evolution process of high-speed turbulent kinetic energy. Through the present application, the setting of boundary conditions for the computational domain of high-speed turbulence based on active flow control is realized, the processes of generation, transfer, and dissipation of high-speed turbulence under active air flow control are analyzed, which helps to explore the mechanism of friction drag reduction in supersonic flow control, and solves the problem of how to obtain the influence of active flow control on high-speed turbulence.

Description

Technical Field

[0001] The present application relates to the field of aerodynamic design of aircraft, and particularly 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 / suction control on the surface of a supersonic aircraft can effectively reduce the aerodynamic friction drag of the aircraft. Therefore, understanding the mechanism of blowing / suction control for supersonic flow friction drag reduction is very important for formulating blowing / suction control strategies. However, due to the very complex evolution process of supersonic turbulent structures, which may involve typical flow field structures such as large and small scale vortices, near-wall strips, and unsteady shock waves, the difficulty of understanding the mechanism of supersonic turbulent drag reduction increases significantly.

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

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

[0005] In a first aspect, embodiments of the present application provide a method for extracting turbulent kinetic energy characteristics, the method including:

[0006] Setting boundary conditions for the computational 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;

[0007] Performing iterative calculations through the Navier-Stokes equations based on the boundary conditions of the computational domain to obtain instantaneous values of flow field variables of each flow field physical variable;

[0008] Calculating each turbulent kinetic energy characteristic term in the turbulent kinetic energy transport equation based on the instantaneous values of the flow field variables of the flow field physical variables, where the turbulent kinetic energy characteristic term characterizes the evolution process of high-speed turbulent kinetic energy.

[0009] In some embodiments, setting boundary conditions for the computational 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 includes:

[0010] For the normal direction of the computational domain of high-speed turbulence on the high-speed aircraft, setting boundary conditions based on the applied active flow control on the high-speed aircraft;

[0011] For the flow direction of the computational domain of high-speed turbulence on the high-speed aircraft, setting boundary conditions based on the type of high-speed turbulence on the high-speed aircraft;

[0012] For the spanwise direction of the computational domain of high-speed turbulence on the high-speed aircraft, the boundary conditions set for the two boundary surfaces in the spanwise direction of the computational domain are both periodic boundary conditions.

[0013] In some embodiments, for the normal direction of the computational domain of high-speed turbulence on the high-speed aircraft, setting the boundary conditions based on the active flow control applied on the high-speed aircraft includes:

[0014] For the normal direction of the computational domain of high-speed turbulence on the high-speed aircraft, if no active flow control is applied on the high-speed aircraft, the set boundary conditions are no-slip and non-penetrating wall conditions;

[0015] If active flow control is applied on the high-speed aircraft, the velocity of the blowing / suction wall surface in the normal direction of the computational domain is set to:

[0016]

[0017] where F represents the blowing or suction intensity, ρ bl represents the blowing or suction density, S inlet represents the area of the inlet or periodic surface, represents the surface integral of the product of density and flow velocity in the inlet or periodic surface.

[0018] In some embodiments, for the flow direction of the computational domain of high-speed turbulence on the high-speed aircraft, setting the boundary conditions based on the type of high-speed turbulence on the high-speed aircraft includes:

[0019] For the flow direction of the computational domain of 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 for the two boundary surfaces in the flow direction of the computational domain are both periodic boundary conditions;

[0020] If the high-speed turbulence on the high-speed aircraft is flat plate turbulence, the two boundary surfaces in the flow direction of the computational domain are respectively set as the inlet and the outlet based on the main flow direction.

[0021] In some embodiments, 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 to include:

[0022] Based on the instantaneous quantities of the flow field variables of the flow field physical variables, the time-averaged quantity and density-weighted averaged quantity of the flow field physical variables are calculated, where the flow field physical variables include density ρ , flow velocity u , normal velocity v , spanwise velocityw and temperature T ;

[0023] Based on the time-averaged quantity and density-weighted averaged quantity of the physical variables of the flow field, each turbulent kinetic energy characteristic term in the turbulent kinetic energy transport equation is calculated.

[0024] In some embodiments, calculating the time-averaged quantity and density-weighted averaged quantity of the physical variables of the flow field based on the instantaneous quantity of the flow field variables of the physical variables of the flow field includes:

[0025] Select the instantaneous quantities of the flow field variables of the physical variables of the flow field at consecutive N output time steps, and sort the instantaneous quantities of the flow field variables in the output order from 1 to N , and then through the recursive calculation formula:

[0026]

[0027] Calculate the time-averaged quantity N of the physical variables of the flow field at consecutive output time steps, where represents the n th output time step, when n = 1, when n = N , ; then represents the instantaneous quantity of the flow field variable of the physical variable of the flow field at the n th output time step;

[0028] On the basis of calculating the time-averaged quantity , the density-weighted averaged quantity of the physical variables of the flow field at consecutive N output time steps is calculated through the Favre averaged quantity calculation formula , where represents the time-averaged quantity of the product of the density and the physical variable of the flow field , represents the time-averaged quantity of the density .

[0029] In some embodiments, calculating each turbulent kinetic energy characteristic term in the turbulent kinetic energy transport equation based on the time-averaged quantity and density-weighted averaged quantity of the physical variables of the flow field includes:

[0030] ​Based on the time-averaged and density-weighted averaged quantities of the physical variables of the flow field, the turbulent kinetic energy transport equation is calculated by means of spatial differentiation. Each turbulent kinetic energy characteristic term in is the generation term of the turbulent kinetic energy, is the diffusion term of the turbulent kinetic energy, is the pressure work term, is the viscous diffusion term, is the viscous dissipation term, is the stress diffusion term;

[0031] The wall normalization process is performed on the turbulent kinetic energy characteristic terms to obtain the turbulent kinetic energy characteristic terms for direct comparative analysis.

[0032] In some embodiments, before setting the boundary conditions for the computational domain of the high-speed turbulence on the high-speed aircraft based on the active flow control applied on the high-speed aircraft, the method includes:

[0033] Determine the computational domain of the supersonic turbulence on the supersonic aircraft, and perform discrete processing on the computational domain to obtain a computational domain containing discrete grid points, wherein the flow direction and spanwise direction of the computational domain are discretely processed using equally spaced grids, and the normal direction of the computational domain is discretely processed using a hyperbolic tangent distribution grid.

[0034] In some embodiments, the high-speed aircraft is a supersonic aircraft, the high-speed turbulence is supersonic turbulence, and the active flow control is blow / suction control.

[0035] In a second aspect, an embodiment of the present application provides a turbulent kinetic energy characteristic extraction system, which 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;

[0036] The condition setting module is used to set the boundary conditions for the computational domain of the high-speed turbulence on the high-speed aircraft according to the type of high-speed turbulence on the high-speed aircraft and the applied active flow control;

[0037] The instantaneous quantity calculation module is used to perform iterative calculations through the Navier-Stokes equation according to the boundary conditions of the computational domain to obtain the instantaneous quantities of the flow field variables of each physical variable of the flow field;

[0038] The characteristic extraction module is used to calculate each turbulent kinetic energy characteristic term in the turbulent kinetic energy transport equation according to the instantaneous quantities of the flow field variables of the physical variables of the flow field, wherein the turbulent kinetic energy characteristic terms characterize the evolution process of the high-speed turbulent kinetic energy.

[0039] Compared with the related art, an extraction method and system for turbulent kinetic energy characteristics provided by an embodiment of the present application, wherein the method sets boundary conditions for a computational domain of high-speed turbulence on a high-speed aircraft based on the type of high-speed turbulence on the high-speed aircraft and the applied active flow control; based on the boundary conditions of the computational domain, iterative calculations are performed through the Navier-Stokes equations to obtain instantaneous flow field variables of each flow field physical variable; based on the instantaneous flow field variables of the flow field physical variables, each turbulent kinetic energy characteristic term in the turbulent kinetic energy transport equation is calculated, where the turbulent kinetic energy characteristic term characterizes the evolution process of high-speed turbulent kinetic energy, realizes the setting of boundary conditions for the high-speed turbulence computational domain based on active flow control, completes the assembly of each term in the turbulent kinetic energy transport equation, analyzes the generation, transfer, and dissipation processes of high-speed turbulence under active air flow control, helps to explore the mechanism of friction drag reduction in supersonic flow control, and is applied to the aerodynamic design of low-drag aircraft, solving the problem of how to obtain the influence of active flow control on high-speed turbulence. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The schematic embodiments and descriptions thereof of the present application are used to explain the present application and do not constitute an improper limitation to the present application. In the drawings:

[0041] Figure 1 is a flowchart of the steps of the extraction method for turbulent kinetic energy characteristics provided by an embodiment of the present application;

[0042] Figure 2 is a schematic flowchart of the extraction method for turbulent kinetic energy characteristics provided by an embodiment of the present application;

[0043] Figure 3 is the turbulent kinetic energy transport equation according to a specific embodiment of the present application P K Item comparison schematic diagram;

[0044] Figure 4 is the turbulent kinetic energy transport equation according to a specific embodiment of the present application T K Item comparison schematic diagram;

[0045] Figure 5 is the turbulent kinetic energy transport equation according to a specific embodiment of the present application Item comparison schematic diagram;

[0046] Figure 6 is the turbulent kinetic energy transport equation according to a specific embodiment of the present application D K Item comparison schematic diagram;

[0047] Figure 7 is the turbulent kinetic energy transport equation according to a specific embodiment of the present applicationε K Schematic diagram for item comparison;

[0048] Figure 8 is the turbulent kinetic energy transport equation according to the specific embodiments of the present application M K Schematic diagram for item comparison;

[0049] Figure 9 is the internal structure schematic diagram of the electronic device according to the embodiments of the present application. Specific embodiments

[0050] In order to make the objectives, technical solutions and advantages of the present application more clear and understandable, the present application will be described and explained below with reference to 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 used to limit the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments provided in the present application without making creative efforts fall within the scope of protection of the present application.

[0051] Obviously, the accompanying drawings in the following description are only some examples or embodiments of the present application. For those of ordinary skill in the art, without making creative efforts, the present application can also be applied to other similar scenarios based on these drawings. In addition, it can also be understood that although the efforts made in this development process may be complex and lengthy, for those of ordinary skill in the art related to the content disclosed in the present application, some design, manufacturing or production changes based on the technical content disclosed in the present application are only conventional technical means and should not be understood as the content disclosed in the present application being insufficient.

[0052] Referring to "embodiments" in the present application means that the specific features, structures or characteristics described in connection with the embodiments can be included in at least one embodiment of the present application. The appearance of this phrase in various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those of ordinary skill in the art explicitly and implicitly understand that the embodiments described in the present application can be combined with other embodiments without conflict.

[0053] Unless otherwise defined, the technical terms or scientific terms involved in this application shall have the ordinary meanings understood by those with ordinary skills in the technical field to which this application belongs. The words such as "a", "an", "one", "the" and the like involved in this application do not indicate a quantity limitation and may represent a singular or plural number. The terms "comprising", "including", "having" and any variations thereof involved in this application are intended to cover non-exclusive inclusion; 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 further include unlisted steps or units, or may further include other steps or units inherent to these processes, methods, products or devices. The words such as "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 "plurality" involved in this application refers to two or more. "And / or" describes the association relationship of associated objects and indicates that three relationships may exist. For example, "A and / or B" may represent: A exists alone, A and B exist simultaneously, and B exists alone. The character " / " generally represents an "or" relationship between the front and rear associated objects. The terms "first", "second", "third" and the like involved in this application are only used to distinguish similar objects and do not represent a specific order of the objects.

[0054] An embodiment of the present application provides a method for extracting turbulent kinetic energy characteristics. Figure 1 It is a flowchart of the steps of the method for extracting turbulent kinetic energy characteristics provided by the embodiment of the present application, as Figure 1 shown, and the method includes the following steps:

[0055] Step S102, set boundary conditions for the computational domain of high-speed turbulence on a high-speed aircraft based on the type of high-speed turbulence on the high-speed aircraft and the applied active flow control.

[0056] Step S102 specifically includes the following steps:

[0057] Step S1021, for the normal direction of the computational domain of high-speed turbulence on a high-speed aircraft, set boundary conditions based on the applied active flow control on the high-speed aircraft.

[0058] Step S1022, for the flow direction of the computational domain of high-speed turbulence on a high-speed aircraft, set boundary conditions based on the type of high-speed turbulence on the high-speed aircraft.

[0059] Specifically for the flow direction of the computational domain 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 for the two side boundaries in the flow direction of the computational domain are both periodic boundary conditions; if the high-speed turbulence on the high-speed aircraft is flat plate turbulence, the two side boundaries in the flow direction of the computational domain are respectively set as the inlet and the outlet based on the mainstream direction.

[0060] Step S1023: For the spanwise direction of the computational domain of high-speed turbulence on a high-speed aircraft, the boundary conditions set for the two side boundaries in the spanwise direction of the computational domain are both periodic boundary conditions.

[0061] It should be noted that if the boundary conditions set for the two side boundaries are both periodic boundary conditions, it means that the flow characteristics in this direction (such as the flow direction of the computational domain in step S1022 and the spanwise direction of the computational domain in step S1023) are assumed to be periodic. Specifically, it is assumed that the flow in the spanwise direction of the computational domain is uniform and infinitely extended. Therefore, the flow state on one side of the computational domain is exactly the same as that on the opposite side. This means that the velocity, pressure, temperature, and all other relevant physical quantities are equal on the two opposite boundaries.

[0062] Before step S102, the method further includes step S101 of 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. Among them, the flow direction and spanwise direction of the computational domain are discretized using equally spaced grids, and the normal direction of the computational domain is discretized using a hyperbolic tangent distribution grid.

[0063] Step S104: Based on the boundary conditions of the computational domain, perform iterative calculations through the Navier-Stokes equations to obtain the instantaneous flow field variables of each flow field physical variable.

[0064] Specifically for step S104, the inviscid term in the Navier-Stokes equations (abbreviated as the N-S equations) is preferably discretized using an 8th-order central difference scheme, the viscous term is preferably discretized using a 7th-order upwind difference scheme, and the time term is preferably advanced using a 3rd-order Runge-Kutta scheme with TVD properties. When the iterative calculations are completed, store the instantaneous flow field variables of each flow field physical variable (density ρ , flow direction velocity u , normal direction velocity v , spanwise direction velocity w and temperature T ) at each output time step, and name the file storing the instantaneous flow field variables as the instantaneous variable file.

[0065] Step S106: Based on the instantaneous values of the flow field physical variables, calculate each turbulent kinetic energy characteristic term in the turbulent kinetic energy transport equation, where the turbulent kinetic energy characteristic term characterizes the evolution process of the high-speed turbulent kinetic energy.

[0066] Step S106 specifically includes the following steps:

[0067] Step S1061: Based on the instantaneous values of the flow field physical variables, calculate the time-averaged value and density-weighted average value (Favre average value) of the flow field physical variables, where the flow field physical variables include density ρ , streamwise 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 and store the instantaneous values of the flow field variables of pressure p , but the flow field physical variables include pressure p ).

[0068] Step S1062: Based on the time-averaged value and density-weighted average value of the flow field physical variables, calculate each turbulent kinetic energy characteristic term in the turbulent kinetic energy transport equation.

[0069] Specifically, in step S1062, based on the time-averaged value and density-weighted average value of the flow field physical variables, calculate each turbulent kinetic energy characteristic term in the turbulent kinetic energy transport equation by means of spatial differentiation. The expression of the turbulent kinetic energy transport equation is:

[0070]

[0071] Among them, the two terms on the left side of the equation expression characterize the time and space growth rates of the turbulent kinetic energy, is the generation term of the turbulent kinetic energy, is the diffusion term of the turbulent kinetic energy, is the pressure work term, is the viscous diffusion term, is the viscous dissipation term, is the stress diffusion term;

[0072] Then, perform wall normalization on the turbulent kinetic energy characteristic term to obtain the turbulent kinetic energy characteristic term for direct comparative analysis.

[0073] It should be noted that the Turbulent Kinetic Energy (TKE) is a measure of the energy of the random motion of the fluid in turbulence and is a key quantity in the study of turbulence. For wall-bounded turbulence, the turbulent kinetic energy is of great significance and can help researchers understand and describe the characteristics of turbulence, especially the turbulent structure, energy transport, and flow characteristics in the boundary layer. The expression for the turbulent kinetic energy is:

[0074]

[0075] where, k represents the turbulent kinetic energy, u 、 v and w represent the streamwise X 、normal Y and spanwise Z velocities respectively; the superscript " '' " represents the Favre fluctuating quantity. Let , then the above expression for the turbulent kinetic energy can be transformed into where the subscript j is a dummy index (the i in the following equations (2.1) to (2.8), and the l in equations (2.7) and (2.8) are the same by analogy), and it is necessary to iterate over j = 1, j = 2, j = 3 and sum them up.

[0076] The Turbulent Kinetic Energy Transport Equation is a core equation in the theory of turbulence. It describes the generation, dissipation, transport of the turbulent kinetic energy, and the interaction between turbulence and the mean flow. The purpose of studying the turbulent kinetic energy transport equation is to describe the changes of the turbulent energy (i.e., the turbulent kinetic energy) in space and time, including the source, transformation, and transport process of the turbulent kinetic energy. Through the turbulent kinetic energy transport equation, one can better understand the energy distribution in different regions of turbulence, the changes in the turbulent intensity, and its relationship with other characteristics of the flow (such as the 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:

[0077] The first term is the generation term of the turbulent kinetic energy, which characterizes the generation of the turbulent kinetic energy, and its specific expression is:

[0078] (2.1)

[0079] The second term is the diffusion term of turbulent kinetic energy, representing the diffusion of turbulent kinetic energy caused by the correlation of velocity and density fluctuations. Its specific expression is:

[0080] (2.2)

[0081] The third term on the right-hand side is the pressure work term, representing the influence of pressure work on turbulent kinetic energy. represents pressure, and its specific expression is:

[0082] (2.3)

[0083] The fourth term is the viscous diffusion term, representing the transport of turbulent kinetic energy in space caused by viscous stress. Its specific expression is:

[0084] (2.4)

[0085] The fifth term is the viscous dissipation term, representing the viscous dissipation caused by turbulent fluctuations. Its specific expression is:

[0086] (2.5)

[0087] The sixth term is the stress diffusion term, representing the diffusion of the mean flow viscous stress caused by velocity fluctuations. Its specific expression is:

[0088] (2.6)

[0089] For the above fourth, fifth, and sixth terms, represents the viscous stress of the mean flow, represents the stress generated by fluctuations, represents the fluid viscosity coefficient, and their expressions are respectively:

[0090] (2.7)

[0091] (2.8)

[0092] In equations (2.7) and (2.8), is the Kronecker symbol. Only when , , otherwise .

[0093] Through the above steps in the embodiments of the present application, the boundary conditions of the high-speed turbulent flow calculation domain based on active flow control are realized, the assembly of each term in the turbulent kinetic energy transport equation is completed, and the processes of generation, transfer, and dissipation of high-speed turbulence under active air flow control are analyzed, which helps to explore the friction drag reduction mechanism of supersonic flow control and apply it to the aerodynamic design of low-drag aircraft, and solves the problem of how to obtain the influence of active flow control on high-speed turbulence.

[0094] In some of these embodiments, preferably, the above step S1021 Figure 2 is a schematic flow chart of the method for extracting turbulent kinetic energy characteristics provided by the embodiments of the present application. As Figure 2 shown, for the normal direction of the calculation domain 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 set boundary condition is the no-slip and non-penetrating wall condition (the wall velocity v bl is set to 0);

[0095] As Figure 2 shown, if active flow control is applied on the high-speed aircraft, the velocity v bl of the blowing / suction wall on the normal direction of the calculation domain is set as:

[0096]

[0097] Wherein, F represents the blowing or suction intensity, ρ bl represents the blowing or suction density (generally obtained by interpolation of points near the wall), S inlet represents the area of the inlet or periodic surface, represents the area integral of the product of density and flow velocity at the inlet (flat plate) or periodic surface (channel and pipe), ρ ∞,NC represents the density of the inlet (flat plate) or periodic surface (channel and pipe) under the condition of no control, u ∞,NC represents the flow velocity of the inlet (flat plate) or periodic surface (channel and pipe) under the condition of no control.

[0098] Furthermore, for the case where active flow control is applied on the high-speed aircraft, the velocity v bl of the blowing / suction wall on the normal direction of the calculation domain is calculated in a discrete form in the program, and its discrete form calculation formula is:

[0099]

[0100] In the formula,N y and N z represent the number of grid points in the normal and spanwise directions respectively, I 、 J and K represent the grid point numbers in the flow direction, normal direction, and spanwise direction respectively, ρ I=1,J,K represents the grid point on the inlet or periodic surface with the normal serial number of J ; u I=1,J,K represents the grid point on the inlet or periodic surface with the spanwise serial number of K ;

[0101] In some of these embodiments, preferably in step S1061, the instantaneous quantities of the flow field variables of the flow field physical variables at consecutive N output time steps are selected, and the instantaneous quantities of the flow field variables are sorted from 1 to N in the output order, and then through the recursive calculation formula:

[0102]

[0103] the time-averaged quantity N of the flow field physical variables at consecutive output time steps is calculated, where represents the n th output time step's , when n = 1, , when n = N , ; then represents the instantaneous quantity of the flow field variable of the flow field physical variable at the n th output time step;

[0104] On the basis of calculating the time-averaged quantity , the density-weighted average quantity of the flow field physical variables at consecutive N output time steps is calculated through the Favre average quantity calculation formula , where represents the time-averaged quantity of the product of the density and the flow field physical variable , represents the time-averaged quantity of the density .

[0105] It should be noted that in step S1061, consecutive N ​The instantaneous values of the flow field variables at each output time step are obtained through recursive solution to get the time-averaged values. In this way, it is possible to monitor in real time the value of, which is convenient for judging whether it converges, and can accelerate the convergence when calculating the average value of the product of multiple variables (time-averaged value and density-weighted average value) in step S1062. In addition, to ensure the accuracy of the time-averaged quantity, N should be as large as possible. The time-averaged value and Favre average value calculated in this step are saved separately in different files, named the time-averaged value file and the Favre average value file.

[0106] In some of these embodiments, preferably in the above step S1062, the relevant quantities of the six turbulent kinetic energy characteristic terms on the right side of the equal sign in the turbulent kinetic energy transport equation can be directly calculated based on the time-averaged values of the flow field physical variables ( , , , , and ) and the density-weighted average value.

[0107] ① In other words, the relevant quantities in the above equations (2.1) to (2.8) can be directly calculated by taking the spatial partial derivatives based on the time-averaged value and density-weighted average value obtained in step S1061. Specifically, these relevant quantities include in equation (2.1), in equation (2.6), in equation (2.7), and . Among them, the average flow viscosity coefficient in equation (2.7) can be calculated by the Sutherland formula , where is the Reynolds number; , represents the reference temperature.

[0108] ② For the remaining relevant quantities among the six turbulent kinetic energy characteristic terms. First, the pressure in equation (2.3) is calculated through p , where represents the Mach number; secondly, the time fluctuation and density-weighted fluctuation (Favre fluctuation) of the flow field physical variables are calculated. The calculation formula for the time fluctuation of the flow field physical variables is , and the calculation formula for the Favre fluctuation of the flow field physical variables is , where represents the density ρ , the flow direction velocityu , normal velocity v , spanwise velocity w , temperature T , pressure p and viscosity coefficient μ ; Again, based on the obtained time pulsation quantity and density-weighted pulsation quantity, by taking spatial partial derivatives, the in Equation (2.1), the in Equation (2.2), the in Equation (2.3), the in Equation (2.4), the in Equation (2.5), and the in Equation (2.6) are solved in sequence. In particular, when calculating the relevant quantities in Equations (2.4) and (2.5), the in can be calculated first, and then the time-averaged quantity containing is calculated.

[0109] Based on the relevant quantities in the six turbulent kinetic energy characteristic terms calculated through the above ①②, these six terms of the turbulent kinetic energy transport equation are assembled. Specifically, the first term is obtained by multiplying the calculated in the above ① and the calculated in the above ②; the second term is the calculated in the above ②; the third term is the calculated in the above ②; the fourth term is the calculated in the above ②; the fifth term is the calculated in the above ②; the sixth term is obtained by multiplying the obtained in the above ① and the obtained in the above ②.

[0110] Finally, for the convenience of direct comparison and analysis, wall normalization processing is performed on these six turbulent kinetic energy characteristic terms. The wall shear stress is calculated through , the wall friction velocity is calculated through , and the wall viscous scale is calculated through , where all the quantities with the subscript " w " represent the values of the variables at the wall. If the incoming flow temperature and the wall temperature are the same, then . Furthermore, the length unit for dimensionlessization , speed unit . Divide the six turbulent kinetic energy characteristic terms , , , , and by respectively to obtain the wall-normalized turbulent kinetic energy characteristic terms. At the same time, obtain the wall-normalized normal height and speed .

[0111] Export and compare the wall-normalized and turbulent kinetic energy characteristic terms, and the process of supersonic turbulence generation, transfer, and dissipation under blowing / suction control can be analyzed, which helps to explore the mechanism of friction drag reduction in supersonic flow control and apply it to the aerodynamic design of low-drag aircraft.

[0112] In some of the embodiments, preferably in step S101, as Figure 2 shown, determine the computational domain and discretize the computational domain space into grid points (a cuboid computational domain can be selected, and the lengths of the computational domain in the flow direction, normal direction, and span direction are respectively L x , L y and L z ), and the flow direction X and span Z of the computational domain are discretized using equally spaced grids; the normal direction Y of the computational domain is discretized using a hyperbolic tangent distribution grid, and the expression for discretizing the hyperbolic tangent distribution grid is:

[0113]

[0114] wherein, J represents the serial number of the normal grid point, y J represents the normal height of the J th grid point, N y is the number of normal grids; b g is a parameter used to ensure that the wall-normalized normal height y + < 1.

[0115] The specific embodiments of the present application improve a method for extracting turbulent kinetic energy characteristics. Through this method, the evolution processes such as the generation, diffusion, pressure transport, viscous stress diffusion, and viscous dissipation of supersonic turbulent kinetic energy can be clearly demonstrated. In addition, by comparing the variation laws of turbulent kinetic energy characteristics before and after applying blowing / suction control at different supersonic oncoming flow Mach numbers, the friction drag reduction mechanism of blowing / suction flow control can be revealed.

[0116] Taking the uncontrolled conditions with Mach numbers of and and the blowing / suction intensity conditions as examples, each term of the wall-normalized turbulent kinetic energy transport equation is compared and shown.

[0117] Figure 3 is a comparison schematic diagram of the P K term of the turbulent kinetic energy transport equation according to the specific embodiments of the present application, Figure 4 is a comparison schematic diagram of the T K term of the turbulent kinetic energy transport equation according to the specific embodiments of the present application, Figure 5 is a comparison schematic diagram of the term of the turbulent kinetic energy transport equation according to the specific embodiments of the present application, Figure 6 is a comparison schematic diagram of the D K term of the turbulent kinetic energy transport equation according to the specific embodiments of the present application, Figure 7 is a comparison schematic diagram of the ε K term of the turbulent kinetic energy transport equation according to the specific embodiments of the present application, Figure 8 is a comparison schematic diagram of the M K term of the turbulent kinetic energy transport equation according to the specific embodiments of the present application. By comparing Figures 3 to 8 , some conclusions about the influence of applying blowing / suction on turbulent kinetic energy characteristics can be obtained:

[0118] Before applying blowing / suction, the peaks of the turbulent kinetic energy generation terms are the same, but the larger the Mach number, the larger the dimensionless normal height of the peak. Applying blowing / suction does not change the position of the peak, but the larger the Mach number, the larger the peak change amount. This indicates that for the same blowing / suction intensity, the higher the Mach number, the more it can promote the generation of turbulent kinetic energy.

[0119] Before applying blowing / suction, the larger the Mach number, the larger the dissipation term of the turbulent kinetic energy. After applying blowing / suction, the difference in turbulent kinetic energy dissipation caused by the Mach number is significantly amplified.

[0120] In the viscous sublayer ( ), the diffusion caused by viscous stress promotes the growth of turbulent kinetic energy; in the buffer layer ( ), 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.

[0121] In some of these 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 blow / suction control.

[0122] It should be noted that the steps shown in the above process or the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although the logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in a different order than here.

[0123] The embodiment of the present application provides a system for extracting turbulent kinetic energy characteristics, which includes a condition setting module, an instantaneous quantity calculation module, and a characteristic extraction module;

[0124] The condition setting module is used to set boundary conditions for the computational domain of high-speed turbulence on a high-speed aircraft according to the type of high-speed turbulence on the high-speed aircraft and the applied active flow control;

[0125] The instantaneous quantity calculation module is used to perform iterative calculations through the Navier-Stokes equations according to the boundary conditions of the computational domain to obtain the instantaneous quantities of the flow field variables of each flow field physical variable;

[0126] The characteristic extraction module is used to calculate each turbulent kinetic energy characteristic term in the turbulent kinetic energy transport equation according to the instantaneous quantities of the flow field variables of the flow field physical variables, where the turbulent kinetic energy characteristic term characterizes the evolution process of high-speed turbulent kinetic energy.

[0127] Through the condition setting module, the instantaneous quantity calculation module, and the characteristic extraction module in the embodiment of the present application, the setting of the boundary conditions of the high-speed turbulence computational domain based on active flow control is realized, the assembly of each item in the turbulent kinetic energy transport equation is completed, the processes of generation, transfer, and dissipation of high-speed turbulence under active air flow control are analyzed, which helps to explore the mechanism of friction drag reduction in supersonic flow control and is applied to the aerodynamic design of low-drag aircraft, and solves the problem of how to obtain the influence of active flow control on high-speed turbulence.

[0128] It should be noted that the above-mentioned each module can be a functional module or a program module, and can be implemented either by software or by hardware. For the modules implemented by hardware, the above-mentioned each module can be located in the same processor; or the above-mentioned each module can also be located in different processors in any combined form.

[0129] This embodiment also provides an electronic device, including a memory and a processor. 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.

[0130] Optionally, the above electronic device may further include a transmission device and an input / output device. The transmission device is connected to the above processor, and the input / output device is connected to the above processor.

[0131] It should be noted that the specific examples in this embodiment may refer to the examples described in the above embodiments and optional implementation manners, and will not be repeated here.

[0132] In addition, in combination with the turbulent kinetic energy characteristic extraction method in the above embodiments, an embodiment of the present application can provide a storage medium to implement. A computer program is stored on the storage medium; when the computer program is executed by a processor, it implements any one of the turbulent kinetic energy characteristic extraction methods in the above embodiments.

[0133] In one embodiment, a computer device is provided. The computer device may be a terminal. The computer device includes a processor, a memory, a network interface, a display screen, and an input device connected through 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 through a network connection. When the computer program is executed by the processor, it implements a turbulent kinetic energy characteristic extraction method. The display screen of the computer device may be a liquid crystal display screen or an electronic ink display screen. The input device of the computer device may be a touch layer covering the display screen, or a button, a trackball, or a touchpad provided on the housing of the computer device, or an external keyboard, touchpad, or mouse, etc.

[0134] In one embodiment, Figure 9 is a schematic internal structure diagram of an electronic device according to an embodiment of the present application. As Figure 9 shown, an electronic device is provided. The electronic device may be a server, and its internal structure diagram may be as Figure 9As shown. The electronic device includes a processor, a network interface, an internal memory, and a non-volatile memory connected by an internal bus. Among them, 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, when executed by the processor, is used to implement a method for extracting turbulent kinetic energy characteristics. The database is used to store data.

[0135] Those skilled in the art can understand that Figure 9 the structure shown in is only a block diagram of some structures related to the solution of this application, and does not constitute a limitation on the electronic device to which the solution of this application is applied. The specific electronic device may include more or fewer components than those shown in the figure, or combine some components, or have different component arrangements.

[0136] Those of ordinary skill in the art can understand that all or part of the processes in the methods of the above embodiments can be completed by instructing relevant hardware through a computer program. 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 methods. Among them, any reference to a memory, storage, database, or other medium used in the various embodiments provided in this application can include non-volatile and / or volatile memories. 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 an external cache. By way of illustration and not limitation, RAM is available in various 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.

[0137] Those skilled in the art should understand that the technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered to be within the scope described in this specification.

[0138] The above-described embodiments merely represent several implementation manners of the present application. The description thereof is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all fall within the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the appended 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, represents the surface integral of the product of density and streamwise velocity at the inlet or periodic surface, ρ ∞,NC represents the density of the inlet or periodic surface in the uncontrolled case, u ∞,NC It represents the streamwise velocity at the inlet or periodic surface without control.

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 , and then calculate 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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