CN113609598B - RANS/LES disturbance domain updating method for aircraft aerodynamic characteristic simulation - Google Patents

RANS/LES disturbance domain updating method for aircraft aerodynamic characteristic simulation Download PDF

Info

Publication number
CN113609598B
CN113609598B CN202111173753.9A CN202111173753A CN113609598B CN 113609598 B CN113609598 B CN 113609598B CN 202111173753 A CN202111173753 A CN 202111173753A CN 113609598 B CN113609598 B CN 113609598B
Authority
CN
China
Prior art keywords
dynamic domain
les
rans
domain
dynamic
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Active
Application number
CN202111173753.9A
Other languages
Chinese (zh)
Other versions
CN113609598A (en
Inventor
蒋崇文
胡姝瑶
高振勋
许晨豪
李椿萱
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Beihang University
Original Assignee
Beihang University
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Beihang University filed Critical Beihang University
Priority to CN202111173753.9A priority Critical patent/CN113609598B/en
Publication of CN113609598A publication Critical patent/CN113609598A/en
Application granted granted Critical
Publication of CN113609598B publication Critical patent/CN113609598B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F30/00—Computer-aided design [CAD]
    • G06F30/20—Design optimisation, verification or simulation
    • G06F30/23—Design optimisation, verification or simulation using finite element methods [FEM] or finite difference methods [FDM]
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F30/00—Computer-aided design [CAD]
    • G06F30/10—Geometric CAD
    • G06F30/15—Vehicle, aircraft or watercraft design
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F30/00—Computer-aided design [CAD]
    • G06F30/20—Design optimisation, verification or simulation
    • G06F30/28—Design optimisation, verification or simulation using fluid dynamics, e.g. using Navier-Stokes equations or computational fluid dynamics [CFD]
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F2111/00—Details relating to CAD techniques
    • G06F2111/10—Numerical modelling
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T90/00—Enabling technologies or technologies with a potential or indirect contribution to GHG emissions mitigation

Abstract

The invention discloses an RANS/LES disturbance domain updating method for aircraft aerodynamic characteristic simulation, which is characterized in that a dynamic calculation domain of RANS and LES is established according to flow parameters such as viscosity coefficient, velocity gradient and the like, and dynamic explicit partitioning of an RANS/LES mixing method is realized, so that dependence of the RANS/LES mixing method on manual experience is reduced while 'grey zone' non-material understanding is avoided, and applicability of the RANS/LES mixing method to a complex aircraft streaming flow field is improved; secondly, the solution of the unsteady double-time step method and the unsteady time advance method is unified, and the coupled solution of the steady RANS and the steady LES is realized by establishing a dynamic calculation domain which increases along with disturbance propagation and converges along with the solution, so that invalid calculation cannot be generated in numerical simulation, and extra boundary condition processing between the RANS and the LES working area can be avoided.

Description

RANS/LES disturbance domain updating method for aircraft aerodynamic characteristic simulation
Technical Field
The invention belongs to the technical field of computational fluid mechanics, and particularly relates to an RANS/LES disturbance domain updating method for aircraft aerodynamic characteristic simulation.
Background
Computational fluid dynamics numerical simulation has become one of the indispensable means in aircraft aerodynamic characteristics prediction. When the flow of an aircraft is simulated, turbulent flow which has obvious influence on the key aerodynamic characteristics of the aircraft such as aerodynamic force/moment, aerodynamic heating and the like is a key point and a difficult point of solving. The most mature turbulence numerical simulation method is a reynolds average turbulence model (RANS), which has the computational efficiency advantages of low grid resolution requirement, capability of solving turbulence problems regularly, and the like. However, the simulation accuracy of the RANS method for spatial free turbulence such as free shear layer mixing, free jet and large separation wake regions is limited, and the description of the turbulence structure is difficult to be in practical use. In order to further improve the accuracy of turbulence simulation, a Large Eddy Simulation (LES) method has been developed. However, the requirement of the LES method for the mesh resolution makes it only applicable to the study of the flow mechanism in a simple shape, and is difficult to be applied to a real aircraft. Therefore, the development of the RANS/LES hybrid method is one of effective ways to combine the simulation precision and efficiency of the aerodynamic characteristics of the aircraft.
The principle of the RANS/LES hybrid approach lies in: and (3) efficiently simulating a near-wall region dominated by small-scale motion by adopting RANS (random access storage), and calculating a separation region dominated by large-scale motion by using LES. The division of the action areas of the two modes has an explicit mode and an implicit mode. The implicit mode is that a mixing function is constructed by adopting parameters such as length scale, vortex viscosity and the like, so that the action areas of two modes are implicitly distinguished. Although this method is convenient and easy to implement, a "gray zone" appears in the vicinity of the characteristic parameters of the two modes, and the problem of non-understanding caused by the mismatch of the grid resolution and the modes exists. The explicit method is to explicitly divide the action areas of the two modes, so as to avoid the occurrence of "gray areas" from the root. However, in the existing explicit methods, such as the zone separation vortex simulation (ZDES) method, the user needs to specify the action region of each mode. For complex flows, it is difficult to both implement and ensure the rationality of the zone division. In addition, the conventional RANS/LES mixing method needs to solve two modes simultaneously in an unsteady manner, or needs to construct a complex boundary coupling condition between an unsteady LES and a steady RANS, and the two modes can generate additional calculation to different degrees, so that the calculation efficiency of the RANS/LES mixing method is limited.
Disclosure of Invention
The invention provides an RANS/LES disturbance domain updating method for aircraft aerodynamic characteristic simulation, which aims to solve the problems that the existing RANS/LES mixing method is high in explicit partitioning artificial experience requirement, a complex flow field is difficult to apply, and two modes of a constant RANS mode and an unsteady LES mode need complex boundary coupling conditions. The specific technical scheme of the invention is as follows:
RANS/LES disturbance domain updating method for aircraft aerodynamic characteristic simulation comprises the following steps:
s1: calculating and preprocessing;
s1-1: reading in data;
s1-2: calculating and storing the wall distances and the sub-lattice scales of all the grid units;
s1-3: initializing a flow field;
s1-4: establishing a dynamic calculation domain, including a convection dynamic domain, an RANS dynamic domain and an LES dynamic domain;
s2: solving a flow control equation;
s2-1: and (3) allocating storage space: distributing space for the variables related to updating in the time-marching method according to the range of the convection dynamic domain, namely keeping constant updating quantity and local time step length;
s2-2: processing boundary conditions;
s2-3: residual error estimation;
s2-4: time integration;
s2-5: judging whether exiting the iteration within the current moment: if the iteration step number in the current moment reaches the set maximum value or the maximum value of the module value of the unit conservative quantity updating quantity in the LES dynamic domain is smaller than the inner iteration convergence threshold value, exiting the iteration in the current moment and continuing the step S2-6; if the two are not satisfied, jumping to step S2-1, and entering the next iteration step of iteration within the current time;
s2-6: judging whether the calculation is finished: if the current time reaches the end-state time set by the user, continuing to step S4; if not, updating in the LES dynamic domainW n()、W n(-1)Entering the next physical time, and jumping to step S2-1;
s3: updating a dynamic calculation domain;
s4: and outputting the result.
Further, the process of step S1-4 is: when initializing according to the incoming flow condition, establishing a convection and RANS dynamic domain only according to the wall boundary; when the method is initialized according to the appointed flow field, three types of dynamic calculation domains are established according to the conservation quantity of the appointed flow field, the convection dynamic domain is ensured to only contain the region with the different flow state from the incoming flow, the LES dynamic domain only contains the separation region in the convection dynamic domain, and the RANS dynamic domain only contains the viscous effect leading region except the LES dynamic domain.
Further, the method of step S2-3 is:
the discrete unsteady flow control process of the double-time step method comprises the following steps:
Figure 426464DEST_PATH_IMAGE001
（1）
wherein the residual error is definedR(W *) Is composed of
Figure 812446DEST_PATH_IMAGE002
（2）
Wherein the content of the first and second substances,τrepresenting virtual time, ΔtRepresents a physical time step; l Ω |),N f、ΔSRespectively representing the volume of the grid unit, the number of surfaces and the area of the unit surface;F c、F vrespectively representing convection and viscous flux;Q Trepresenting a source term of a turbulence model equation;W *indicating that the current time is a constant value,W n()the value of the last time is the constant value,W n(-1)representing the last time conservation quantity;
if in the formulae (1) and (2), ΔtIf infinity is taken, the equation is degraded into a discrete equation of a constant time propulsion method, a viscous flux term and a turbulence model equation source term in a residual error are collectively called as a viscous term, and in the solution, firstly, a convection term in a formula (2) is calculated by traversing a unit in a convection dynamic domain; secondly, traversing the unit in the LES dynamic domain, and calculating a source item and a sticky item in a double time step method in the formula (2); finally, traversing the RANS dynamic domain unit, and calculating the sticky item in the formula (2).
Further, the step S2-4 includes the steps of:
s2-4-1: in the convection dynamic domain, traversing from the minimum label grid to the maximum label grid, and solving the matrixLAndD(ii) a If the cell is in the LES dynamic domain, then the matrixDIn consideration oft，ΔtTaking a physical time step specified by a user; if the cell is not in the LES dynamic domain, then the matrixDWithout taking into account Δt；
S2-4-2: in the convection dynamic domain, traversing from the maximum label grid to the minimum label grid, and solving the matrixU；
S2-4-3: in the convection dynamic domain, traversing from the minimum label grid to the maximum label grid, and updating the iteration value of the current time conservation quantityW *The velocity gradients of all cells are calculated and the position of the maximum velocity gradient is recorded.
Further, the step S3 includes the following steps:
s3-1: increasing the convection dynamic domain: for all convection dynamic domain boundary units, judging whether the boundary units are subjected to inviscid disturbance or not through the module values of the conservative quantity updating quantity; if the unit is disturbed, adding the adjacent unit positioned in the disturbance propagation direction into a convection dynamic domain;
s3-2: and (3) narrowing the convection dynamic domain: for all convection dynamic domain boundary units, if the boundary units simultaneously satisfy: removing the unit from the convection dynamic domain under the five conditions of 'no newly-added undisturbed unit exists around', 'the solution has converged', 'is located at the most upstream', 'does not influence the solution of other units in the convection dynamic domain any more' and 'is not influenced by other units in the convection dynamic domain any more'; if the unit also belongs to the RANS or LES dynamic domain, removing the unit from other dynamic domains;
s3-3: selecting an LES dynamic domain updating mode: if the module value of the maximum velocity gradient is greater than the velocity gradient threshold value, the velocity gradient along the normal direction and the tangential gradient from the nearest wall surface is in the same magnitude, and the maximum velocity gradient unit is not located in the LES dynamic domain, continuing to step S3-4; otherwise, if the LES dynamic domain already exists, jumping to step S3-5;
s3-4: establishing an LES dynamic domain: taking the maximum velocity gradient unit and the adjacent unit in the flow separation as the initial unit of the LES dynamic domain;
s3-5: increasing the LES dynamic domain: judging whether the cell is positioned in the flow separation region or not through the velocity gradient for all the LES dynamic domain boundary cells; if in the flow separation zone, add all of its immediate neighbors to the LES dynamic domain; if the adjacent unit is located in the RANS dynamic domain, removing the adjacent unit from the RANS dynamic domain;
s3-6: narrowing the LES dynamic domain: for all LES dynamic domain border elements, if the border element and its surrounding elements are not located in the flow separation region, removing the element from the LES dynamic domain and adding it to the RANS dynamic domain;
s3-7: increase of the RANS dynamic domain: for all the units in the boundary unit of the RANS dynamic domain which are not adjacent to the LES dynamic domain, if the boundary unit is dominated by the viscosity effect, all the adjacent units which are located in the convection dynamic domain but not located in the LES dynamic domain are added into the RANS dynamic domain:
s3-8: narrowing the RANS dynamic domain: for all elements in the RANS dynamic domain border element that are not immediately adjacent to the LES dynamic domain, if the border element and its neighbors are no longer dominated by sticky effects, they are removed from the RANS dynamic domain.
The invention has the beneficial effects that:
1. the RANS-LES disturbance domain updating method for aircraft aerodynamic characteristic simulation can remarkably improve the calculation efficiency of accurate simulation of large separation flow in the aircraft bypass flow field.
2. Compared with the existing implicit division mode, such as a despun vortex simulation (DES) method, the method has the advantages that the action areas of RANS simulation and LES simulation are clearly defined, the 'grey zone' cannot occur, and the problem of non-physical understanding caused by the use of an LES mode in a boundary layer can be solved.
3. Compared with the existing explicit division mode, the RANS and LES working areas of the method do not need to be specified by a user, the steps S3-3 to S3-6 can dynamically and adaptively determine reasonable working areas, and the method has the advantages of low dependence on manual experience, strong adaptability of complex flow fields and the like.
4. The method comprises the steps of coupling an unsteady double-time-step method and an unsteady time-marching method for solving, considering source items of the double-time-step method only in an LES dynamic domain in step S2-3, and considering the double-time-step method to an LU-SGS format matrix only in the LES dynamic domain in step S2-4DThe addition of (2); a convective dynamic domain which increases along with disturbance propagation and decreases along with solving convergence is defined through the steps S3-1 and S3-2, and a converged inviscid region, an RANS solving region and an LES solving region can be ensured not to participate in calculation any more, so that invalid calculation in a traditional numerical simulation method is effectively avoided, and coupling solving without additional boundary condition processing of a steady RANS method and a steady LES method is realized.
Drawings
In order to illustrate embodiments of the present invention or technical solutions in the prior art more clearly, the drawings which are needed in the embodiments will be briefly described below, so that the features and advantages of the present invention can be understood more clearly by referring to the drawings, which are schematic and should not be construed as limiting the present invention in any way, and for a person skilled in the art, other drawings can be obtained on the basis of these drawings without any inventive effort. Wherein:
FIG. 1 is a flow chart of the present invention;
FIG. 2 is a dynamic calculation domain in the separation flow under a simulated wing large angle of attack deep stall condition.
Detailed Description
In order that the above objects, features and advantages of the present invention can be more clearly understood, a more particular description of the invention will be rendered by reference to the appended drawings. It should be noted that the embodiments of the present invention and features of the embodiments may be combined with each other without conflict.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, however, the present invention may be practiced in other ways than those specifically described herein, and therefore the scope of the present invention is not limited by the specific embodiments disclosed below.
Firstly, according to flow parameters such as viscosity coefficient, velocity gradient and the like, a dynamic calculation domain of RANS and LES is established, and dynamic explicit partitioning of a RANS/LES mixing method is realized, so that dependence of the RANS/LES mixing method on manual experience is reduced while non-material understanding of a 'grey zone' is avoided, and applicability of the RANS/LES mixing method to a complex aircraft streaming flow field is improved. Secondly, the solution of the unsteady double-time step method and the unsteady time advance method is unified, and the coupled solution of the steady RANS and the steady LES is realized by establishing a dynamic calculation domain which increases along with disturbance propagation and converges along with the solution, so that invalid calculation cannot be generated in numerical simulation, and extra boundary condition processing between the RANS and the LES working area can be avoided.
Specifically, the RANS/LES disturbance domain updating method for aircraft aerodynamic characteristic simulation comprises the following steps:
s1: calculating and preprocessing;
s1-1: data reading: distributing static arrays for storing grid coordinates and conservative quantities, and reading in data such as node coordinates, boundary conditions, calculation settings and the like of a calculation grid;
s1-2: calculating and storing the wall distances and the sub-lattice scales of all the grid units;
the wall distance can be determined by calculating the distance from the grid center to all the wall cells and wall points one by one and storing the minimum value. The sub-lattice dimension is a characteristic length dimension of the LES mode, and can be the maximum value of the side length of the grid unit in each grid direction, namely
Figure 933461DEST_PATH_IMAGE003
（1）
In the formula,. DELTA.x、Δy、ΔzRespectively a grid cell edgeI、J、KGrid dimension in grid direction.
S1-3: initializing a flow field; and assigning the conservation quantities of all grid units in the preset calculation domain according to the incoming flow conditions or the given flow field. Initialization according to the incoming flow condition is to assign the conservative quantity of all units in a preset calculation domain as an incoming flow value. The initialization according to the given flow field is to obtain the conservative quantity of all units in the preset calculation domain according to the interpolation of the given flow field.
S1-4: and establishing a dynamic calculation domain, including a convection dynamic domain, a RANS dynamic domain and an LES dynamic domain.
When initializing according to the incoming flow condition, establishing a convection and RANS dynamic domain only according to the wall boundary; when the method is initialized according to the appointed flow field, three types of dynamic calculation domains are established according to the conservation quantity of the appointed flow field, the convection dynamic domain is ensured to only contain the region with the different flow state from the incoming flow, the LES dynamic domain only contains the separation region in the convection dynamic domain, and the RANS dynamic domain only contains the viscous effect leading region except the LES dynamic domain.
For example, when initializing according to the incoming flow condition, 10 layers of cells adjacent to the wall surface are taken as initial cells of the convection, and 1 layer of cells adjacent to the wall surface is taken as the RANS dynamic domain. When the unit is initialized according to the designated flow field, the unit with different conservation quantity and inflow conditions is screened as an initial unit of the convection dynamic domain. Viscous effects are measured as the ratio of convective flux to viscous flux Jacobian matrix and whether separation is measured as a velocity gradient. And screening units dominated by the viscous effect in the convection dynamic domain, wherein the units with larger velocity gradients in all coordinate directions are used as initial units of the LES dynamic domain, and the rest are used as initial units of the RANS dynamic domain.
S2: solving a flow control equation;
s2-1: and (3) allocating storage space: distributing space for the variables related to updating in the time-marching method according to the range of the convection dynamic domain, namely keeping constant updating quantity and local time step length;
s2-2: processing boundary conditions of a preset calculation domain by a virtual grid method;
s2-3: residual error estimation;
the discrete unsteady flow control process of the double-time step method comprises the following steps:
Figure 797512DEST_PATH_IMAGE004
（2）
wherein the residual error is definedR(W *) Is composed of
Figure 205360DEST_PATH_IMAGE002
（3）
Wherein the content of the first and second substances,τrepresenting virtual time, ΔtRepresents a physical time step; l Ω |),N f、ΔSRespectively representing the volume of the grid unit, the number of surfaces and the area of the unit surface;F c、F vrespectively representing convection and viscous flux;Q Trepresenting a source term of a turbulence model equation;W *indicating that the current time is a constant value,W n()the value of the last time is the constant value,W n(-1)representing the last time conservation quantity;
if in formulas (2) and (3), ΔtIf infinity is taken, the equation is degraded into a discrete equation of a constant time propulsion method, a viscous flux term and a turbulence model equation source term in residual errors are collectively called as viscous terms, and in the solution, firstly, a unit in a convection dynamic domain is traversed, and a calculation formula (3) is obtainedThe convection term of (1); secondly, traversing the unit in the LES dynamic domain, and calculating a source item and a sticky item in a double time step method in the formula (3); finally, traversing the RANS dynamic domain unit, and calculating the sticky item in the formula (3).
S2-4: in the convection dynamic domain, performing time integration by adopting a virtual time term of the LU-SGS format discrete formula (1);
s2-4-1: in the convection dynamic domain, traversing from the minimum label grid to the maximum label grid, and solving the matrixLAndD(ii) a If the cell is in the LES dynamic domain, then the matrixDIn consideration oft，ΔtTaking a physical time step specified by a user; if the cell is not in the LES dynamic domain, then the matrixDWithout taking into account Δt；
S2-4-2: in the convection dynamic domain, traversing from the maximum label grid to the minimum label grid, and solving the matrixU；
S2-4-3: in the convection dynamic domain, traversing from the minimum label grid to the maximum label grid, and updating the iteration value of the current time conservation quantityW *The velocity gradients of all cells are calculated and the position of the maximum velocity gradient is recorded.
S2-5: judging whether exiting the iteration within the current moment: if the iteration step number in the current moment reaches the set maximum value or the maximum value of the module value of the unit conservative quantity updating quantity in the LES dynamic domain is smaller than the inner iteration convergence threshold value, exiting the iteration in the current moment and continuing the step S2-6; if the two are not satisfied, jumping to step S2-1, and entering the next iteration step of iteration within the current time;
s2-6: judging whether the calculation is finished: if the current time reaches the end-state time set by the user, continuing to step S4; if not, updating in the LES dynamic domainW n()、W n(-1)Then, the process proceeds to the next physical time, and the process proceeds to step S2-1.
S3: updating a dynamic calculation domain;
s3-1: increasing the convection dynamic domain: for all convection dynamic domain boundary units, judging whether the boundary units are subjected to inviscid disturbance or not through the module values of the conservative quantity updating quantity; if the unit is disturbed, adding the adjacent unit positioned in the disturbance propagation direction into a convection dynamic domain;
specifically, traversing all the boundary cells of the convection dynamic domain, and for any one boundary cell:
(1) let | Δ |W| represents a modulus of a conservative update amount,ε a,cindicating that a given threshold is added to the flow, the perturbation of the boundary cell can be described as
||ΔW||＞ε a,c（4）
(2) If the cell satisfies equation (4), the immediate neighboring cell that it may be disturbed is added to the convective dynamic domain. For a cell in subsonic flow, the immediate vicinity of the cell that may be disturbed is all the cells around. For units in supersonic flow, letqFor the unit vector of the cell center pointing to the cell point, perturb the edgeqThe direction propagation will satisfy
u·q+a＞0 （5）
In the formula (I), the compound is shown in the specification,uwhich represents the vector of the flow velocity,ais the speed of sound. If the unit vector of the cell center pointing to a certain grid point satisfies equation (5), the adjacent cell containing the grid point is added to the convection dynamic field.
S3-2: and (3) narrowing the convection dynamic domain: for all convection dynamic domain boundary units, if the boundary units simultaneously satisfy: removing the unit from the convection dynamic domain under the five conditions of 'no newly-added undisturbed unit exists around', 'the solution has converged', 'is located at the most upstream', 'does not influence the solution of other units in the convection dynamic domain any more' and 'is not influenced by other units in the convection dynamic domain any more'; if the unit also belongs to the RANS or LES dynamic domain, removing the unit from other dynamic domains; the specific judgment conditions are as follows:
(1) the adjacent units of the newly added undisturbed unit satisfy the formula (4), so that if none of the surrounding units satisfy the formula (4), the newly added undisturbed unit is not present around the unit to be deleted.
(2) The convergence condition of the cell can be described by the modulus of the conservative update quantity. Order toε dIndicating a given deletionThreshold, then the solution of the to-be-deleted unit to converge can be described as
||ΔW||＞ε d（6）
(3) Whether the flow direction is positioned at the most upstream can be judged through the geometrical relation of the flow direction and the unit. Order toqThe unit vector indicating that the cell center to be deleted points to the adjacent cell center is positioned at the top stream, and all the adjacent cells in the convection dynamic domain should meet the requirement
Figure 496664DEST_PATH_IMAGE005
（7）
In the formula (I), the compound is shown in the specification,θ drepresenting the upstream unit tolerance angle, supersonic flow takes 10 ° and subsonic flow takes 45 °.
(4) The solution of other units in the flow dynamic domain is not influenced;
numerical experiments show that in the incompressible flow with the Mach number less than 0.3, the convergence of the upstream flow and the downstream flow has no sequence. Therefore, compressible flows with mach numbers greater than 0.3 are located most upstream, and the solution of other units in the flow dynamic domain can no longer be affected; incompressible flows with mach numbers less than 0.3 are not removable.
(5) No longer influenced by other units in the convection dynamic domain;
in the supersonic non-viscous flow, as the mathematical property of the control equation is hyperbolic, that is, any point in the flow field is not influenced by the downstream flow, the supersonic non-viscous unit positioned at the most upstream is naturally not influenced by other units in the convection dynamic domain any more.
For subsonic velocity and viscous flow, if the influence of the next unit on the conservative quantity update quantity of the unit to be deleted is considered and the next unit still meets the convergence condition, the unit can be considered to be not influenced by other units any more, namely the unit meets the requirement
Figure 107905DEST_PATH_IMAGE006
（8）
In the formula,. DELTA.tThe step size of the iteration is indicated,C CFLCFL number representing a time advance format, | Ω | represents a volume of a grid cell;I, J, Krepresenting the grid direction; deltaR i Representing the residual edge of the neighboring cell in the convection dynamic domain to the boundary cell of the convection dynamic domainiThe influence of the direction is that the direction of the light,i=I, J, K。
for subsonic inviscid cells, the effect of the next adjacent cell on the residual of the convection dynamic domain boundary cell along the grid direction ΔR i Can be expressed as
Figure 775647DEST_PATH_IMAGE008
（9）
In the formula,. DELTA.WRepresenting a conservative update amount; deltaF c Representing the convection flux variation, namely the difference between the current step and the previous step; subscripti＋1、i-1 represents the convective dynamic domain boundary cell edge positive and negative respectivelyiA direction immediate unit; subscripti＋1/2、i-1/2 denotes the convective dynamic domain boundary cell edge positive and negative respectivelyiA unit face of the direction;
Figure 38001DEST_PATH_IMAGE009
representing the convective flux Jacobian matrix edgeiThe spectral radius of the direction.
For viscous units
Figure 500206DEST_PATH_IMAGE011
（10）
S3-3: selecting an LES dynamic domain updating mode: if the module value of the maximum velocity gradient is greater than the velocity gradient threshold value, the velocity gradient along the normal direction and the tangential gradient from the nearest wall surface is in the same magnitude, and the maximum velocity gradient unit is not located in the LES dynamic domain, continuing to step S3-4; otherwise, if the LES dynamic domain already exists, jumping to step S3-5;
s3-4: establishing an LES dynamic domain: taking the maximum velocity gradient unit and the adjacent unit in the flow separation as the initial unit of the LES dynamic domain;
s3-5: increasing the LES dynamic domain: judging whether the cell is positioned in the flow separation region or not through the velocity gradient for all the LES dynamic domain boundary cells; if in the flow separation zone, add all of its immediate neighbors to the LES dynamic domain; if the adjacent unit is located in the RANS dynamic domain, removing the adjacent unit from the RANS dynamic domain;
specifically, the LES dynamic domain boundary cell is traversed, and for any boundary cell:
(1) order toε sIndicating a given threshold value of the velocity gradient,
Figure 598743DEST_PATH_IMAGE012
components representing the velocity gradient tensor, if satisfied
Figure 804597DEST_PATH_IMAGE013
（11）
And the gradient simulation magnitudes of the velocity components in the normal direction and the tangential direction from the nearest wall surface are similar, the boundary unit is considered to be positioned in the separation area;ε sthe average value of the unit velocity gradient in the RANS dynamic domain can be taken;
(2) if located in the separation region, its immediate neighbor, which is located in the convective dynamic domain, is added to the LES dynamic domain.
S3-6: narrowing the LES dynamic domain: for all LES dynamic domain border elements, if the border element and its surrounding elements are not located in the flow separation region, removing the element from the LES dynamic domain and adding it to the RANS dynamic domain;
s3-7: increase of the RANS dynamic domain: for all the units in the boundary unit of the RANS dynamic domain which are not adjacent to the LES dynamic domain, if the boundary unit is dominated by the viscosity effect, all the adjacent units which are located in the convection dynamic domain but not located in the LES dynamic domain are added into the RANS dynamic domain:
specifically, traversing all the cells not immediately adjacent to the LES dynamic domain in the sticky dynamic domain boundary cell, for any boundary cell:
(1) judging whether the boundary unit is adhered or not by keeping constantA sexual disturbance; order toε a,vFor a given newly added unit of viscosity, the dominant unit of viscosity effect should satisfy:
Figure 921457DEST_PATH_IMAGE014
（12）
in the formula, psi is a viscosity effect measurement parameter,
Figure DEST_PATH_IMAGE015
the maximum value of the parameter for measuring the viscosity effect of the adjacent unit in the 1 st iteration step.
(2) And if the boundary unit is subjected to viscosity disturbance, adding all the adjacent units of the boundary unit, which are positioned in the convection dynamic domain but not positioned in the LES dynamic domain, into the RANS dynamic domain.
S3-8: narrowing the RANS dynamic domain: for all elements in the RANS dynamic domain border element that are not immediately adjacent to the LES dynamic domain, if the border element and its neighbors are no longer dominated by sticky effects, they are removed from the RANS dynamic domain.
The elements in the border elements of the RANS dynamic domain that are not immediately adjacent to the LES dynamic domain are traversed and removed from the RANS dynamic domain if they satisfy the following 2 conditions. The specific conditions are as follows:
(1) judging whether the adjacent two layers of units satisfy the formula (12), if not, indicating that no newly added viscous effect main unit exists around the adjacent two layers of units;
(2) if the unit to be deleted does not satisfy the formula (12), it is represented as no longer being the viscous effect dominant unit.
S4: and outputting the result.
Example 1
In the embodiment, a dynamic calculation domain defined when the airfoil large-attack-angle deep stall flow is simulated, as shown in fig. 2, the unsteady physical time step is 5 × 10-5Computing grid satisfactiony +<1. As can be seen, the method of the present invention divides the airfoil flow field into a tack-free region, an RANS mode operating region and an LES mode operating region. Wherein, the LES mode working area is the area defined by the LES dynamic area and comprises the upper surface and the tail of the airfoil in the flow fieldLarge separation flow in the flow region; the RANS formula working area is an RANS dynamic area and comprises an attachment boundary layer area of a near-wall area of the lower surface of the airfoil profile; the inviscid region belongs to the convection dynamic domain, and the items and variables related to viscosity in the control equation are not calculated in numerical simulation. In the numerical simulation, only an LES dynamic domain adopts an unsteady numerical method to solve the area, and the boundary of the three dynamic domains does not need to be specially processed.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (2)

1. RANS/LES disturbance domain updating method for aircraft aerodynamic characteristic simulation, which is characterized by comprising the following steps:
s1: calculating and preprocessing;
s1-1: reading in data;
s1-2: calculating and storing the wall distances and the sub-lattice scales of all the grid units;
s1-3: initializing a flow field;
s1-4: establishing a dynamic calculation domain, including a convection dynamic domain, an RANS dynamic domain and an LES dynamic domain;
the specific process is as follows: when initializing according to the incoming flow condition, establishing a convection and RANS dynamic domain only according to the wall boundary; when the method is initialized according to the appointed flow field, three types of dynamic calculation domains are established according to the conservation quantity of the appointed flow field, the convection dynamic domain is ensured to only contain the region with the different flow state from the incoming flow, the LES dynamic domain only contains the separation region in the convection dynamic domain, and the RANS dynamic domain only contains the viscous effect leading region except the LES dynamic domain;
s2: solving a flow control equation;
s2-1: and (3) allocating storage space: according to the range of the convection dynamic domain, space is allocated for the variables related to updating in the time-marching method, namely the conservative updating quantity and the local time step length;
s2-2: processing boundary conditions;
s2-3: residual error estimation; the specific method comprises the following steps:
the discrete unsteady flow control process of the double-time step method comprises the following steps:
Figure 968452DEST_PATH_IMAGE001
（1）
wherein the residual error is definedR(W *) Is composed of
Figure 325353DEST_PATH_IMAGE002
（2）
Wherein the content of the first and second substances,τrepresenting virtual time, ΔtRepresents a physical time step; l Ω |),N f、ΔSRespectively representing the volume of the grid unit, the number of surfaces and the area of the unit surface;F c、F vrespectively representing convection and viscous flux;Q Trepresenting a source term of a turbulence model equation;W *indicating that the current time is a constant value,W n()the value of the last time is the constant value,W n(-1)representing the last time conservation quantity;
if in the formulae (1) and (2), ΔtIf infinity is taken, the equation is degraded into a discrete equation of a constant time propulsion method, a viscous flux term and a turbulence model equation source term in a residual error are collectively called as a viscous term, and in the solution, firstly, a convection term in a formula (2) is calculated by traversing a unit in a convection dynamic domain; secondly, traversing the unit in the LES dynamic domain, and calculating a source item and a sticky item in a double time step method in the formula (2); finally, traversing units in the RANS dynamic domain, and calculating the sticky items in the formula (2);
s2-4: in a convection dynamic domain, performing time integration by adopting a virtual time term of an LU-SGS format discrete formula (1);
s2-4-1: in the convection dynamic domain, traversing from the minimum label grid to the maximum label grid, and solving the matrixLAndD(ii) a If the cell is in the LES dynamic domain, then the matrixDIn consideration oft，ΔtTaking a physical time step specified by a user; if the cell is not in the LES dynamic domain, then the matrixDWithout taking into account Δt；
S2-4-2: in the convection dynamic domain, traversing from the maximum label grid to the minimum label grid, and solving the matrixU；
S2-4-3: in the convection dynamic domain, traversing from the minimum label grid to the maximum label grid, and updating the iteration value of the current time conservation quantityW *Calculating the speed gradients of all the units, recording the position of the maximum speed gradient, and continuing to step S2-5 after the step S3 is finished;
s2-5: judging whether exiting the iteration within the current moment: if the iteration step number in the current moment reaches the set maximum value or the maximum value of the module value of the unit conservative quantity updating quantity in the LES dynamic domain is smaller than the inner iteration convergence threshold value, exiting the iteration in the current moment and continuing the step S2-6; if the two are not satisfied, jumping to step S2-1, and entering the next iteration step of iteration within the current time;
s2-6: judging whether the calculation is finished: if the current time reaches the end-state time set by the user, continuing to step S4; if not, updating in the LES dynamic domainW n()、W n(-1)Entering the next physical time, and jumping to step S2-1;
s3: updating a dynamic calculation domain;
s4: and outputting the result.
2. The RANS/LES disturbance domain updating method for aircraft aerodynamic characteristics simulation according to claim 1, wherein said step S3 comprises the steps of:
s3-1: increasing the convection dynamic domain: for all convection dynamic domain boundary units, judging whether the boundary units are subjected to inviscid disturbance or not through the module values of the conservative quantity updating quantity; if the unit is disturbed, adding the adjacent unit positioned in the disturbance propagation direction into a convection dynamic domain;
s3-2: and (3) narrowing the convection dynamic domain: for all convection dynamic domain boundary units, if the boundary units simultaneously satisfy: removing the unit from the convection dynamic domain under the five conditions of 'no newly-added undisturbed unit exists around', 'the solution has converged', 'is located at the most upstream', 'does not influence the solution of other units in the convection dynamic domain any more' and 'is not influenced by other units in the convection dynamic domain any more'; if the unit also belongs to the RANS or LES dynamic domain, removing the unit from other dynamic domains;
s3-3: selecting an LES dynamic domain updating mode: if the module value of the maximum velocity gradient is greater than the velocity gradient threshold value, the velocity gradient along the normal direction and the tangential gradient from the nearest wall surface is in the same magnitude, and the maximum velocity gradient unit is not located in the LES dynamic domain, continuing to step S3-4; otherwise, if the LES dynamic domain already exists, jumping to step S3-5;
s3-4: establishing an LES dynamic domain: taking the maximum velocity gradient unit and the adjacent unit in the flow separation as the initial unit of the LES dynamic domain;
s3-5: increasing the LES dynamic domain: judging whether the cell is positioned in the flow separation region or not through the velocity gradient for all the LES dynamic domain boundary cells; if in the flow separation zone, add all of its immediate neighbors to the LES dynamic domain; if the adjacent unit is located in the RANS dynamic domain, removing the adjacent unit from the RANS dynamic domain;
s3-6: narrowing the LES dynamic domain: for all LES dynamic domain border elements, if the border element and its surrounding elements are not located in the flow separation region, removing the element from the LES dynamic domain and adding it to the RANS dynamic domain;
s3-7: increase of the RANS dynamic domain: for all the units in the boundary unit of the RANS dynamic domain which are not adjacent to the LES dynamic domain, if the boundary unit is dominated by the viscosity effect, all the adjacent units which are located in the convection dynamic domain but not located in the LES dynamic domain are added into the RANS dynamic domain:
s3-8: narrowing the RANS dynamic domain: for all elements in the RANS dynamic domain border element that are not immediately adjacent to the LES dynamic domain, if the border element and its neighbors are no longer dominated by sticky effects, they are removed from the RANS dynamic domain.
CN202111173753.9A 2021-10-09 2021-10-09 RANS/LES disturbance domain updating method for aircraft aerodynamic characteristic simulation Active CN113609598B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202111173753.9A CN113609598B (en) 2021-10-09 2021-10-09 RANS/LES disturbance domain updating method for aircraft aerodynamic characteristic simulation

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202111173753.9A CN113609598B (en) 2021-10-09 2021-10-09 RANS/LES disturbance domain updating method for aircraft aerodynamic characteristic simulation

Publications (2)

Publication Number Publication Date
CN113609598A CN113609598A (en) 2021-11-05
CN113609598B true CN113609598B (en) 2022-01-07

Family

ID=78343366

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202111173753.9A Active CN113609598B (en) 2021-10-09 2021-10-09 RANS/LES disturbance domain updating method for aircraft aerodynamic characteristic simulation

Country Status (1)

Country Link
CN (1) CN113609598B (en)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113962030B (en) * 2021-12-20 2022-03-11 北京航空航天大学 Method for updating disturbance domain of overlapped grids of multi-body separation simulation of aircraft
CN114841095B (en) * 2022-07-05 2022-09-09 北京航空航天大学 Incompressible flow disturbance domain propulsion method
CN114880971B (en) * 2022-07-13 2022-09-20 中国空气动力研究与发展中心计算空气动力研究所 Implicit method adopted by computational fluid dynamics software
CN117131806B (en) * 2023-09-11 2024-02-02 南京信息工程大学 CFD-based biological pool speed and volume analysis method, system and storage medium

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2012031398A1 (en) * 2010-09-09 2012-03-15 Tianjin Aerocode Engineering Application Software Development Inc. Numerical method for simulating subsonic flows based on euler equations in lagrangian formulation
CN111651831B (en) * 2020-04-13 2022-04-08 北京航空航天大学 Partition disturbance domain updating calculation method for constant-viscosity compressible streaming of aircraft
CN111859530B (en) * 2020-06-11 2022-04-22 北京航空航天大学 Iterative propulsion disturbance domain updating method for aircraft dynamic aerodynamic characteristic simulation

Also Published As

Publication number Publication date
CN113609598A (en) 2021-11-05

Similar Documents

Publication Publication Date Title
CN113609598B (en) RANS/LES disturbance domain updating method for aircraft aerodynamic characteristic simulation
He et al. Robust aerodynamic shape optimization—from a circle to an airfoil
Hartmann et al. A strictly conservative Cartesian cut-cell method for compressible viscous flows on adaptive grids
Yu et al. A high-order spectral difference method for unstructured dynamic grids
CN111859530B (en) Iterative propulsion disturbance domain updating method for aircraft dynamic aerodynamic characteristic simulation
CN111859529B (en) Multi-grid disturbance domain updating acceleration method for aircraft streaming numerical simulation
Pan et al. Upwind finite-volume Navier-Stokes computations on unstructured triangular meshes
Loppi et al. Locally adaptive pseudo-time stepping for high-order flux reconstruction
Tucker Hybrid Hamilton–Jacobi–Poisson wall distance function model
Cai et al. A parallel viscous flow solver on multi-block overset grids
Mirzaei et al. Simulation of fluid flow in a body-fitted grid system using the lattice Boltzmann method
Jung et al. Turbulent and unsteady flows on unstructured line-based Hamiltonian paths and strands grids
Meakin Adaptive spatial partitioning and refinement for overset structured grids
US20140324399A1 (en) Method and System for Determining Fluid Flow of Compressible and Non-Compressible Liquids
Pang et al. An efficient grid assembling method in unsteady dynamic motion simulation using overset grid
Nair et al. Flow past rotating cylinders at high Reynolds numbers using higher order upwind scheme
Aumann et al. MEGAFLOW: Parallel complete aircraft CFD
Li An improved volumetric LBM boundary approach and its extension for sliding mesh simulation
Evans et al. Computational fluid dynamics applied to the aerodynamic design of a land‐based supersonic vehicle
Burg et al. Unstructured nonlinear free surface simulations for the fully-appended DTMB model 5415 series hull including rotating propulsors
Sitaraman et al. Enhancements to overset methods for improved accuracy and solution convergence
Jouhaud et al. A multigrid adaptive mesh refinement strategy for 3D aerodynamic design
Riha et al. Linear stability of a boundary-layer vortex on a hypersonic finned cone
Luo et al. Strongly coupled fluid–structure interaction analysis of aquatic flapping wings based on flexible multibody dynamics and the modified unsteady vortex lattice method
Filippone et al. Aerodynamic drag prediction of helicopter fuselage

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
GR01 Patent grant
GR01 Patent grant