CN113609597B - Method for updating time-space hybrid propulsion disturbance domain of supersonic aircraft streaming - Google Patents
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Abstract
The invention discloses a method for updating a time-space hybrid propulsion disturbance domain of a supersonic aircraft streaming, which establishes a method for efficiently dividing working areas of a time propulsion method and a space propulsion method by using a disturbance propagation rule and mathematical properties of a flow control equation and combining an updating algorithm and a data structure of a dynamic calculation domain; a boundary condition processing mode of a working area of a time-marching method is provided by utilizing a range specified by a dynamic calculation domain; and finally, the solution thought of local updating of the disturbance region is popularized to a space propulsion method, and a time-space hybrid propulsion disturbance region updating method is established, so that invalid calculation caused by a static calculation region in the time-space hybrid propulsion method is effectively avoided. The method solves the problems that the existing time-space hybrid propulsion method is high in dependence on region division experience, difficult to apply to the flow field of a complex aircraft and yet to improve the calculation efficiency.
Description
Technical Field
The invention belongs to the technical field of computational fluid mechanics, and particularly relates to a method for updating a time-space hybrid propulsion disturbance domain of a supersonic aircraft streaming.
Background
In the design of the aircraft, the efficient aerodynamic characteristic prediction technology is greatly beneficial to improving the performance of the aircraft and shortening the design iteration cycle. For an ultra/hypersonic speed aircraft with the resistance dominated by differential pressure resistance, a viscous-free aerodynamic efficient prediction technology based on solving Euler equations plays an important role in the concept design stage. The Euler equation can be solved by adopting a time propulsion method and a space propulsion method. The time-marching method can solve the subsonic velocity flow and the supersonic velocity flow at the same time, but the steady problem is solved by an unsteady method, so that the calculation amount is large and the convergence is slow. In contrast, the space-marching algorithm can reduce computation time by 1-2 orders of magnitude, but is only applicable to supersonic flow. The circumfluence of the hypersonic/hypersonic aircraft belongs to sub-supersonic mixed flow, so that the development of a time-space mixed propulsion method becomes an effective way for solving both the precision and the efficiency.
The key to the hybrid time-space approach is to determine the working area of both types of methods. The existing method mainly relies on an empirical formula or manual experience division, such as a document 'congratulatio lighting', hypersonic aircraft aerodynamic force aerodynamic heat numerical simulation and supersonic flow region propulsion solving [ D ]. Sichuan sun: 2007' of the research department of China aerodynamic research and development center, the precision of the division mode has high dependence on the manual experience, and the division mode is difficult to be suitable for the bypass flow simulation of the appearance of a complex aircraft. In addition, in the existing hybrid method, a global update solving strategy of a static computing domain is adopted in respective solving areas of the two types of methods, namely, a time-based propulsion method solves all grid units in the same working area in each virtual time iteration step, and a space-based propulsion method also solves all grid units in the working area on each flow direction section. The global updating solution method may cause a large amount of invalid calculations due to failure to consider the laws of disturbance propagation and solution convergence, thereby severely limiting the calculation efficiency. The acceleration technology of the 'disturbance region updating method' can effectively avoid invalid calculation in the time propulsion method, and the popularization of the acceleration technology in the space propulsion method and the time-space hybrid propulsion method still needs the support of relevant theories and technologies.
Disclosure of Invention
In order to solve the defects of the prior art, the invention provides a time-space hybrid propulsion disturbance domain updating method aiming at the problems that the existing time-space hybrid propulsion method is high in region division experience dependency, difficult to be suitable for a complex aircraft flow field and yet to be further improved in computational efficiency, and the specific technical scheme of the invention is as follows:
the method for updating the time-space hybrid propulsion disturbance domain of the circumfluence of the supersonic aircraft comprises the following steps:
s1: establishing a dynamic calculation domain according to the read-in data;
s2: solving a subsonic velocity region by adopting a time propulsion method;
s2-1: allocating storage space for the time marching method: 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: solving an Euler equation in a convection dynamic domain by adopting a time propulsion method;
s2-4: judging whether the time advance dynamic domain solution is converged or not according to the maximum value of the unit conservative updating quantity module value in the convection dynamic domain: if the maximum module value is smaller than the set convergence threshold value, solving convergence, and jumping to the step S3; if the maximum module value is larger than the set convergence threshold value, solving the non-convergence, and continuing to execute the step S2-5;
s2-5: increasing the time-marching dynamic domain and its convective dynamic domain: judging whether the boundary unit is positioned in subsonic flow or not through the conservative quantity of all boundary units in the convection dynamic domain, and judging whether the boundary unit is disturbed or not through the module value of the conservative quantity updating quantity; if the unit is in the subsonic flow and is disturbed, adding the adjacent units into a convection dynamic domain and a time propulsion dynamic domain, and simultaneously removing the newly added unit in the time propulsion dynamic domain from the space propulsion dynamic domain;
s2-6: narrowing the convective dynamic domain in the time-marching dynamic domain: and if all boundary units of the flow dynamic domain satisfy the following conditions simultaneously: removing the unit from the convection dynamic domain under four conditions of 'no newly-added undisturbed unit exists around', 'convergence is solved', 'located at the most upstream' and 'no longer influenced by other units in the convection dynamic domain';
skipping to the step S2-1, and entering the next iteration step of the time-marching dynamic domain solution;
s3: judging whether the whole flow field is solved;
s4: solving a supersonic speed area by adopting a space propulsion method;
s5: and outputting the result.
Further, the step S1 includes the following steps:
s1-1: reading in data;
s1-2: initializing a flow field: assigning the conservative quantities of all grid units in the preset calculation domain read in the step S1-1 as incoming flow values according to the incoming flow boundary conditions read in the step S1-1;
s1-3: determining the grid direction of space propulsion according to the incoming flow direction and the wall surface units;
s1-4: establishing a dynamic calculation domain;
three types of dynamic computing domains are defined: a time advance dynamic domain, a space advance dynamic domain and a convection dynamic domain; the time-marching dynamic domain is a region which must be solved by adopting a time-marching method, the space-marching dynamic domain is a region which is suitable for solving by adopting a space-marching method, and the convection dynamic domain is a region which is actually calculated in each iteration of the time-marching method or the space-marching method.
Further, in step S1-4, when the time-propelling dynamic domain is first established, the aircraft head stagnation point is determined according to the wall boundary condition and the incoming flow velocity vector, and the aircraft head stagnation point and the adjacent units of the specified number of layers thereof are defined as initial units of the time-propelling dynamic domain; at the moment, the space propulsion dynamic domain is set as the range of the preset calculation domain except the time propulsion dynamic domain;
when the time advance dynamic domain is not established for the first time, a conservative update quantity maximum value unit and adjacent units in a space advance method are used as initial units of the time advance dynamic domain; accordingly, newly added cells in the time-marching dynamic domain also need to be removed from the space-marching dynamic domain;
in both cases, the convective dynamic domain range is consistent with the maintenance of the time-marching dynamic domain.
Further, in the step S2-2, the boundary of the convection dynamic domain: coinciding with a preset calculation domain boundary, and assigning values to virtual grids of such boundary according to the physical meaning of the boundary; and when the boundary unit is positioned at the downstream, assigning values to the units with the number of layers specified at the downstream by adopting an extrapolation mode.
Further, the specific method for solving the Euler equation in the convection dynamic domain by using the time marching method in the step S2-3 includes:
s2-3-1: residual estimation: estimating the convection flux of all grid directions in an Euler equation by adopting a convection flux format;
s2-3-2: time integration: and (3) dispersing time-related terms in the Euler equation by adopting a time integral format, and updating the conservation quantity updating quantity and the conservation quantity of the units in the flow dynamic domain.
Further, the step S4 includes the following steps:
s4-1: resetting the convective dynamic domain in the spatial boosting dynamic domain: if the first solved flow direction station position is present, resetting the convection dynamic domain according to the time advance dynamic domain of the upstream adjacent layer unit; if the flow direction station position is not the first solved flow direction station position, resetting the convection dynamic domain according to the space propulsion dynamic domain of the upstream adjacent layer unit;
s4-2: according to the range of the convection dynamic domain, storing a conservation constant updating quantity distribution space for a space propulsion method;
s4-3: solving an Euler equation in a convection dynamic domain by adopting a space propulsion method;
s4-4: judging whether the solution of the current flow station is converged according to the maximum value of the unit conservation quantity updating quantity module value in the flow dynamic domain: if the maximum module value is smaller than the set convergence threshold value, solving convergence, and continuing to the step S4-5; if the maximum module value is larger than the set convergence threshold value, solving the non-convergence, and jumping to the step S4-6;
s4-5: narrowing the space to advance the dynamic domain: for all boundary units of the current stream station space propulsion dynamic domain, if the boundary units simultaneously satisfy: if the conservation quantity is the same as the incoming flow condition and is positioned at the most upstream of the cross flow, the conservation quantity is removed from the space propulsion dynamic domain; after traversing all the boundary units, jumping to the step S4-1, and entering the solution of the next streaming direction station position;
s4-6: judging whether the solution of the current flow direction station is diverged or not according to the maximum value of the unit conservation quantity updating quantity module value in the convection dynamic domain: if the maximum value is increased along with iteration and is larger than the set divergence threshold value, solving divergence, jumping to the step S1-4, and converting the maximum value into a time propulsion method to solve a divergence region; if not, solving and not diverging, and continuing to the step S4-7;
s4-7: in the space propulsion dynamic domain of the current flow direction station position, increasing the convection dynamic domain; traversing the boundary cells of the convective dynamic domain, performing step S4-7 on cells in which the dynamic domain boundary is not immediately adjacent to the space-marching dynamic domain;
judging whether the boundary unit is disturbed or not through the module value of the conservative updating quantity: if the unit is disturbed, adding the adjacent unit which is positioned in the unit influence domain and contained in the current flow direction station space propulsion dynamic domain into the flow direction dynamic domain;
s4-8: narrowing the convective dynamic domain of the space-borne dynamic domain: and if all boundary units of the flow dynamic domain satisfy the following conditions simultaneously: removing the unit from the convection dynamic domain if three conditions of 'no newly-added disturbed unit exists around', 'convergence is solved' and 'the position is the most upstream'; if the conservation of the unit is the same as the incoming flow conditions, then it is also removed from the space-marching dynamic domain;
and jumping to the step S4-2, and entering the next iteration step of the current flow direction station position.
Further, the process of step S3 is: judging according to the minimum value of the module value of the difference between the adjacent wall surface unit and the inflow condition conservation quantity; if the minimum value is zero, areas remain to be solved, the step S4-1 is continued, and the solution of the space propulsion method is carried out; if the minimum value is not zero, the whole calculation domain is solved, and the step S5 is skipped.
Further, the specific method for solving the Euler equation in the convection dynamic domain by using the space propulsion method in the step S4-3 includes:
s4-3-1: residual estimation: estimating a spatial derivative in a non-spatial propelling direction in an Euler equation by adopting a convection discrete format, and calculating a source term of a spatial propelling method;
s4-3-2: space propulsion: and (3) dispersing the virtual time item in the control equation by adopting a time integral format, and updating the conservation quantity updating quantity and the conservation quantity of the units in the convection dynamic domain.
The invention has the beneficial effects that:
1. the method for updating the time-space hybrid propulsion disturbance domain of the circumfluence of the supersonic aircraft can obviously improve the calculation efficiency of the supersonic/hypersonic aircraft in evaluating the aerodynamic performance of a design scheme at the conceptual design stage.
2. In the traditional time-space hybrid propulsion method, the dependence of region division experience is high, and the method is difficult to be applied to the flow field of a complex aircraft; the invention realizes the dynamic and self-adaptive division of the working areas of the two methods by utilizing the characteristics of the two methods. For the two methods, a time advance dynamic domain and a space advance dynamic domain are respectively defined to represent the respective working areas. The step S1-4 can establish two types of dynamic domains of time propulsion and space propulsion according to the flow stagnation point or the space propulsion solution divergence unit, and the steps S2-5 and S4-5 can reasonably adjust the two types of dynamic domains according to the disturbance propagation condition, so that the time propulsion dynamic domain only contains the region which needs to be solved by adopting the time propulsion method, and the space propulsion dynamic domain only contains the region which needs to be solved by adopting the space propulsion method.
3. The traditional time-space hybrid propulsion method has a large amount of invalid calculations, and the calculation efficiency needs to be improved; the method defines the convection dynamic domain in the time-propelled or space-propelled dynamic domain, and realizes the local updating solution idea of only solving in the unconverged disturbed region. The convective dynamic domain represents the area that two types of methods actually need to solve in the solution. The steps S2-5, S2-6, S4-7 and S4-8 can efficiently update the convective dynamic domain according to the flow characteristics and the convergence condition; steps S2-3, S4-3 are both solved only in the convective dynamic domain, so that a significant reduction in computational effort can be achieved.
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 for simulating the supersonic blunt body problem according to the present invention;
FIG. 3 shows the numerical result of the subsonic flow region of the head of the ultrasonic bluff body simulated in the symmetry plane and the corresponding time advance dynamic domain;
fig. 4 shows the numerical result of the supersonic flow area of the simulated supersonic blunt body in a flow direction station and the corresponding space propulsion dynamic domain.
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.
As shown in FIG. 1, the invention provides a method for updating a time-space hybrid propulsion disturbance domain of a supersonic aircraft streaming. The invention provides a boundary condition processing mode of a working area by a time advance method by utilizing a range specified by a dynamic calculation domain. Finally, the method and the device popularize the solution thought of local updating of the disturbance area into a space propulsion method and establish a time-space hybrid propulsion disturbance area updating method, thereby effectively avoiding invalid calculation caused by a static calculation area in the time-space hybrid propulsion method.
The method for updating the time-space hybrid propulsion disturbance domain of the circumfluence of the supersonic aircraft comprises the following steps:
s1: establishing a dynamic calculation domain according to the read-in data;
s1-1: data reading: distributing an array of storage grid coordinates and conservation quantities, and reading in data such as node coordinates, boundary conditions, calculation settings and the like of a calculation grid;
s1-2: initializing a flow field: assigning the conservative quantities of all grid units in the preset calculation domain read in the step S1-1 as incoming flow values according to the incoming flow boundary conditions read in the step S1-1;
s1-3: determining the grid direction of space propulsion according to the incoming flow direction and the wall surface units: traversing all the wall surface units, and counting the inner products of the incoming flow velocity vectors and all the grid directions of the units, wherein the grid direction with the minimum average inner product is the grid direction of space propulsion;
s1-4: establishing a dynamic calculation domain;
three types of dynamic computing domains are defined: a time advance dynamic domain, a space advance dynamic domain and a convection dynamic domain; the time-marching dynamic domain is a region which must be solved by adopting a time-marching method, the space-marching dynamic domain is a region which is suitable for solving by adopting a space-marching method, and the convection dynamic domain is a region which is actually calculated in each iteration of the time-marching method or the space-marching method.
When the time propulsion dynamic domain is established for the first time, determining an aircraft head stagnation point according to wall boundary conditions and incoming flow velocity vectors, and defining the aircraft head stagnation point and adjacent units with the specified number of layers as initial units of the time propulsion dynamic domain; at the moment, the space propulsion dynamic domain is set as the range of the preset calculation domain except the time propulsion dynamic domain;
when the time advance dynamic domain is not established for the first time, a conservative update quantity maximum value unit and adjacent units in a space advance method are used as initial units of the time advance dynamic domain; accordingly, newly added cells in the time-marching dynamic domain also need to be removed from the space-marching dynamic domain;
for example, when the time-marching dynamic domain is first established, i.e., entered by step S1-3, the time-marching dynamic domain is established based on the aircraft head stagnation location. Firstly, traversing all wall surface units, and taking a unit with the inner product of the normal direction and the incoming flow velocity vector of the wall surface unit closest to 0 as a unit where an aircraft head stagnation point is located; secondly, the cell and its adjacent 10 layers of cells are used as the initial cell of the time advance dynamic domain, and the space advance dynamic domain contains other cells except the time advance dynamic domain in the preset calculation domain.
When the time-marching dynamic domain is not established for the first time, i.e. the step S4-6 is entered, the time-marching dynamic domain is established according to the solution divergent elements, the solution divergent elements obtained in the step S4-6 and the adjacent 10-layer elements thereof are taken as initial elements of the time-marching dynamic domain, and these elements are removed from the space-marching dynamic domain.
In both cases, the convective dynamic domain range is consistent with the maintenance of the time-marching dynamic domain.
S2: solving a subsonic velocity region by adopting a time propulsion method;
s2-1: allocating storage space for the time marching method: 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;
boundary of the convective dynamic domain: the virtual grid of the boundary is assigned according to the physical meaning of the boundary and is the same as the conventional method; and when the boundary unit is positioned at the downstream, assigning values to the units with the number of the downstream assigned layers by adopting an extrapolation mode, wherein the number of the assigned units is consistent with the number of the virtual grid layers. For example, if the flow is calculated in a 2 nd order format, the number of virtual grid layers is 2.
S2-3: solving an Euler equation in a convection dynamic domain by adopting a time propulsion method;
s2-3-1: residual estimation: estimating the convection flux of all grid directions in an Euler equation by adopting a convection flux format;
s2-3-2: time integration: and (3) dispersing time-related terms in the Euler equation by adopting a time integral format, and updating the conservation quantity updating quantity and the conservation quantity of the units in the flow dynamic domain.
Specifically, the flow control equation solved by the time-marching method is:
in the formula (I), the compound is shown in the specification,Wrepresenting a conservation quantity;trepresenting a virtual time; l Ω |),N f、ΔSRespectively representing the volume of the grid unit, the number of surfaces and the area of the unit surface;F crepresenting the convective flux.
Firstly, traversing units in a convection dynamic domain, and calculating a convection item at the equal-sign right end of an equation (1) by adopting a convection flux format; and traversing the units in the convection dynamic domain, and calculating a virtual time derivative term at the left end of the equal sign of the formula (1) by adopting a time advance format.
S2-4: judging whether the time advance dynamic domain solution is converged or not according to the maximum value of the unit conservative updating quantity module value in the convection dynamic domain: if the maximum module value is smaller than the set convergence threshold value, solving convergence, and jumping to the step S3; if the maximum module value is larger than the set convergence threshold value, solving the non-convergence, and continuing to execute the step S2-5;
s2-5: increasing the time-marching dynamic domain and its convective dynamic domain: judging whether the boundary unit is positioned in subsonic flow or not through the conservative quantity of all boundary units in the convection dynamic domain, and judging whether the boundary unit is disturbed or not through the module value of the conservative quantity updating quantity; if the unit is in the subsonic flow and is disturbed, adding the adjacent units into a convection dynamic domain and a time propulsion dynamic domain, and simultaneously removing the newly added unit in the time propulsion dynamic domain from the space propulsion dynamic domain; specifically, all boundary cells of the convection dynamic domain are traversed, and for any boundary cell:
first, the current Mach number of the passing unitMJudging whether the unit is in the subsonic flow, if soM<1, the representative unit is located in subsonic flow;
secondly, judging whether the boundary unit is disturbed or not through the module value of the conservative updating quantity; let | Δ |W| represents a modulus of a conservative update amount,ε a,cindicates that given a newly added threshold to the flow, | | ΔW||>ε a,cRepresenting that the cell has been perturbed;
finally, if a cell is both in subsonic flow and disturbed, its immediate neighbors are added to the convective and temporally propulsive dynamic domains, while it is removed from the spatial propulsive dynamic domain.
S2-6: narrowing the convective dynamic domain in the time-marching dynamic domain: and if all boundary units of the flow dynamic domain satisfy the following conditions simultaneously: removing the unit from the convection dynamic domain under four conditions of 'no newly-added undisturbed unit exists around', 'convergence is solved', 'located at the most upstream' and 'no longer influenced by other units in the convection dynamic domain'; the specific judgment conditions are as follows:
(1) if all the surrounding units satisfy | | | DeltaW||<ε a,cAnd then, the newly added undisturbed unit does not exist around the cell.
(2) Order toε dRepresenting a given deletion threshold, the solution of the unit to be deleted is described as | | | ΔW||<ε d。
(3) Order toqThe unit vector indicating that the cell center to be deleted points to the immediately adjacent cell center of the cell, if the cell to be deleted is located at the most upstream, all the immediately adjacent cells in the convection dynamic domain should satisfy:
in the formula (I), the compound is shown in the specification,urepresenting a velocity vector;θ drepresenting the upstream unit tolerance angle, supersonic flow takes 10 ° and subsonic flow takes 45 °.
(4) If the immediate unit still satisfies the convergence condition after considering the influence of the conservative update quantity of the unit to be deleted by the immediate unit, the unit can be considered to be not influenced by other units any more, namely, the unit satisfies the requirement
Wherein
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；ΔWrepresenting a conservative update amount; deltaF cRepresenting 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;
representing the convective flux Jacobian matrix edgeiThe spectral radius of the direction.
And jumping to the step S2-1, and entering the next iteration step of the time advance dynamic domain solution.
S3: judging whether the whole flow field is solved; traversing all units close to the wall boundary, and judging according to the minimum value of the module value of the difference between the adjacent wall unit and the inflow condition conservation quantity; if the minimum value is zero, areas remain to be solved, the step S4-1 is continued, and the solution of the space propulsion method is carried out; if the minimum value is not zero, the whole calculation domain is solved, and the step S5 is skipped.
S4: solving a supersonic speed area by adopting a space propulsion method;
s4-1: resetting the convective dynamic domain in the spatial boosting dynamic domain: if the first solved flow direction station position is present, resetting the convection dynamic domain according to the time advance dynamic domain of the upstream adjacent layer unit; if the flow direction station position is not the first solved flow direction station position, resetting the convection dynamic domain according to the space propulsion dynamic domain of the upstream adjacent layer unit;
s4-2: according to the range of the convection dynamic domain, storing a conservation constant updating quantity distribution space for a space propulsion method;
s4-3: solving an Euler equation in a convection dynamic domain by adopting a space propulsion method;
s4-3-1: residual estimation: estimating a spatial derivative in a non-spatial propelling direction in an Euler equation by adopting a convection discrete format, and calculating a source term of a spatial propelling method;
s4-3-2: space propulsion: and (3) dispersing the virtual time item in the control equation by adopting a time integral format, and updating the conservation quantity updating quantity and the conservation quantity of the units in the convection dynamic domain.
Specifically, the flow control equation solved by the space propulsion method is:
in the formula, ξ represents the coordinate of the spatial propulsion direction.
Firstly, traversing units in a convection dynamic domain, calculating the convection flux in the non-propulsion direction in the formula (5) by adopting a convection flux format, and calculating the convection flux in the propulsion direction in the formula (5) by adopting a single-side interpolation format; and traversing the units in the convection dynamic domain, and adopting a time advance format calculation formula (5) equal-sign left-end item.
S4-4: judging whether the solution of the current flow station is converged according to the maximum value of the unit conservation quantity updating quantity module value in the flow dynamic domain: if the maximum module value is smaller than the set convergence threshold value, solving convergence, and continuing to the step S4-5; if the maximum module value is larger than the set convergence threshold value, solving the non-convergence, and jumping to the step S4-6;
s4-5: narrowing the space to advance the dynamic domain: for all boundary units of the current stream station space propulsion dynamic domain, if the boundary units simultaneously satisfy: if the conservation quantity is the same as the incoming flow condition and is positioned at the most upstream of the cross flow, the conservation quantity is removed from the space propulsion dynamic domain; the specific judgment conditions are as follows:
(1) if the module value of the difference between the conservation quantities of the unit and the incoming flow condition is smaller than the convergence threshold value, the conservation quantities of the unit are the same as the incoming flow condition.
(2) In the current flow direction station, taking the cross flow velocity entrainment type (2) can determine whether the position is the most upstream of the cross flow.
After traversing all the boundary units, jumping to the step S4-1, and entering the solution of the next streaming direction station position;
s4-6: judging whether the solution of the current flow direction station is diverged or not according to the maximum value of the unit conservation quantity updating quantity module value in the convection dynamic domain: if the maximum value is increased along with iteration and is larger than the set divergence threshold value, solving divergence, jumping to the step S1-4, and converting the maximum value into a time propulsion method to solve a divergence region; if not, solving and not diverging, and continuing to the step S4-7;
s4-7: in the space propulsion dynamic domain of the current flow direction station position, increasing the convection dynamic domain; traversing the boundary cells of the convective dynamic domain, performing step S4-7 on cells in which the dynamic domain boundary is not immediately adjacent to the space-marching dynamic domain;
judging whether the boundary unit is disturbed or not through the module value of the conservative updating quantity: if the unit is disturbed, adding the adjacent unit which is positioned in the unit influence domain and contained in the current flow direction station space propulsion dynamic domain into the flow direction 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,cindicates that given a newly added threshold to the flow, | | ΔW||>ε a,cRepresenting that the cell has been perturbed;
(2) if the cell has been disturbed, letqFor the unit vector of the cell center pointing to the cell point, perturb the edgeqThe direction propagation will satisfy
u·q+a＞0（6）
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 (6), the adjacent cell containing the grid point and located in the current stream station space pushing dynamic domain is added into the stream dynamic domain.
S4-8: narrowing the convective dynamic domain of the space-borne dynamic domain: and if all boundary units of the flow dynamic domain satisfy the following conditions simultaneously: removing the unit from the convection dynamic domain if three conditions of 'no newly-added disturbed unit exists around', 'convergence is solved' and 'the position is the most upstream'; if the conservation of the unit is the same as the incoming flow conditions, then it is also removed from the space-marching dynamic domain;
and jumping to the step S4-2, and entering the next iteration step of the current flow direction station position.
S5: and outputting the result.
Example 1
The present example performs simulation on a flow passing through a supersonic blunt body at an angle of attack of mach 2 and 10 °.
FIG. 2 is a dynamic calculation domain defined when simulating the M supersonic blunt body problem. As can be seen from the figure, the method automatically divides the supersonic blunt body flow field into a time propulsion dynamic domain and a space propulsion dynamic domain by taking the sound velocity as a boundary. The time-marching dynamic domain includes a subsonic flow domain upstream of the sonic line, while the space-marching dynamic domain includes a supersonic flow domain downstream of the sonic line. Both types of dynamic calculation domains only contain near shock waves and post-wave flow fields thereof. In the numerical simulation, the time propulsion dynamic domain inner unit is subjected to iterative solution at the same time, and the space propulsion dynamic domain is propelled downstream layer by layer along the space propulsion direction from the sonic velocity. In all the iteration steps, the maximum range participating in calculation is the area defined by the two types of dynamic calculation domains, and the convection dynamic domain is gradually reduced from the shock wave to the wall surface along with the iterative convergence in the iteration.
Fig. 3 is a pressure coefficient cloud diagram of the subsonic flow region of the head of the present embodiment on a symmetric plane, and fig. 4 is a pressure coefficient cloud diagram and an entropy cloud diagram of the supersonic flow region of the present embodiment on a flow direction station. As can be seen from the figure, the method of the present invention can obtain accurate numerical simulation results.
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 (4)
1. The method for updating the time-space hybrid propulsion disturbance domain of the circumfluence of the supersonic aircraft is characterized by comprising the following steps of:
s1: establishing a dynamic calculation domain according to the read-in data;
s1-1: reading in data;
s1-2: initializing a flow field: assigning the conservative quantities of all grid units in the preset calculation domain read in the step S1-1 as incoming flow values according to the incoming flow boundary conditions read in the step S1-1;
s1-3: determining the grid direction of space propulsion according to the incoming flow direction and the wall surface units;
s1-4: establishing a dynamic calculation domain;
three types of dynamic computing domains are defined: a time advance dynamic domain, a space advance dynamic domain and a convection dynamic domain; the time propulsion dynamic domain is a region which needs to be solved by adopting a time propulsion method, the space propulsion dynamic domain is a region suitable for solving by adopting a space propulsion method, and the convection dynamic domain is a region actually calculated in each iteration of the time propulsion method or the space propulsion method;
when the time propulsion dynamic domain is established for the first time, determining an aircraft head stagnation point according to wall boundary conditions and incoming flow velocity vectors, and defining the aircraft head stagnation point and adjacent units with the specified number of layers as initial units of the time propulsion dynamic domain; at the moment, the space propulsion dynamic domain is set as the range of the preset calculation domain except the time propulsion dynamic domain;
when the time advance dynamic domain is not established for the first time, a conservative update quantity maximum value unit and adjacent units in a space advance method are used as initial units of the time advance dynamic domain; accordingly, newly added cells in the time-marching dynamic domain also need to be removed from the space-marching dynamic domain;
in the two cases, the convection dynamic domain range is consistent with the time propulsion dynamic domain;
s2: solving a subsonic velocity region by adopting a time propulsion method;
s2-1: allocating storage space for the time marching method: 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: solving an Euler equation in a convection dynamic domain by adopting a time propulsion method;
s2-4: judging whether the time advance dynamic domain solution is converged or not according to the maximum value of the unit conservative updating quantity module value in the convection dynamic domain: if the maximum module value is smaller than the set convergence threshold value, solving convergence, and jumping to the step S3; if the maximum module value is larger than the set convergence threshold value, solving the non-convergence, and continuing to execute the step S2-5;
s2-5: increasing the time-marching dynamic domain and its convective dynamic domain: judging whether the boundary unit is positioned in subsonic flow or not through the conservative quantity of all boundary units in the convection dynamic domain, and judging whether the boundary unit is disturbed or not through the module value of the conservative quantity updating quantity; if the unit is in the subsonic flow and is disturbed, adding the adjacent units into a convection dynamic domain and a time propulsion dynamic domain, and simultaneously removing the newly added unit in the time propulsion dynamic domain from the space propulsion dynamic domain;
s2-6: narrowing the convective dynamic domain in the time-marching dynamic domain: and if all boundary units of the flow dynamic domain satisfy the following conditions simultaneously: removing the unit from the convection dynamic domain under four conditions of 'no newly-added undisturbed unit exists around', 'convergence is solved', 'located at the most upstream' and 'no longer influenced by other units in the convection dynamic domain';
skipping to the step S2-1, and entering the next iteration step of the time-marching dynamic domain solution;
s3: judging whether the whole flow field is solved; judging according to the minimum value of the module value of the difference between the adjacent wall surface unit and the inflow condition conservation quantity; if the minimum value is zero, areas remain to be solved, the step S4-1 is continued, and the solution of the space propulsion method is carried out; if the minimum value is not zero, the whole calculation domain is solved, and the step S5 is skipped;
s4: solving a supersonic speed area by adopting a space propulsion method; in particular, the amount of the solvent to be used,
s4-1: resetting the convective dynamic domain in the spatial boosting dynamic domain: if the first solved flow direction station position is present, resetting the convection dynamic domain according to the time advance dynamic domain of the upstream adjacent layer unit; if the flow direction station position is not the first solved flow direction station position, resetting the convection dynamic domain according to the space propulsion dynamic domain of the upstream adjacent layer unit;
s4-2: according to the range of the convection dynamic domain, storing a conservation constant updating quantity distribution space for a space propulsion method;
s4-3: solving an Euler equation in a convection dynamic domain by adopting a space propulsion method;
s4-4: judging whether the solution of the current flow station is converged according to the maximum value of the unit conservation quantity updating quantity module value in the flow dynamic domain: if the maximum module value is smaller than the set convergence threshold value, solving convergence, and continuing to the step S4-5; if the maximum module value is larger than the set convergence threshold value, solving the non-convergence, and jumping to the step S4-6;
s4-5: narrowing the space to advance the dynamic domain: for all boundary units of the current stream station space propulsion dynamic domain, if the boundary units simultaneously satisfy: if the conservation quantity is the same as the incoming flow condition and is positioned at the most upstream of the cross flow, the conservation quantity is removed from the space propulsion dynamic domain; after traversing all the boundary units, jumping to the step S4-1, and entering the solution of the next streaming direction station position;
s4-6: judging whether the solution of the current flow direction station is diverged or not according to the maximum value of the unit conservation quantity updating quantity module value in the convection dynamic domain: if the maximum value is increased along with iteration and is larger than the set divergence threshold value, solving divergence, jumping to the step S1-4, and converting the maximum value into a time propulsion method to solve a divergence region; if not, solving and not diverging, and continuing to the step S4-7;
s4-7: in the space propulsion dynamic domain of the current flow direction station position, increasing the convection dynamic domain; traversing the boundary cells of the convective dynamic domain, performing step S4-7 on cells in which the dynamic domain boundary is not immediately adjacent to the space-marching dynamic domain;
judging whether the boundary unit is disturbed or not through the module value of the conservative updating quantity: if the unit is disturbed, adding the adjacent unit which is positioned in the unit influence domain and contained in the current flow direction station space propulsion dynamic domain into the flow direction dynamic domain;
s4-8: narrowing the convective dynamic domain of the space-borne dynamic domain: and if all boundary units of the flow dynamic domain satisfy the following conditions simultaneously: removing the unit from the convection dynamic domain if three conditions of 'no newly-added disturbed unit exists around', 'convergence is solved' and 'the position is the most upstream'; if the conservation of the unit is the same as the incoming flow conditions, then it is also removed from the space-marching dynamic domain; jumping to the step S4-2, and entering the next iteration step of the current flow direction station position;
s5: and outputting the result.
2. The method for updating the time-space hybrid propulsion disturbance domain of the circumfluence of the supersonic aircraft according to claim 1, wherein in the step S2-2, the boundary of the convective dynamic domain: coinciding with a preset calculation domain boundary, and assigning values to virtual grids of such boundary according to the physical meaning of the boundary; and when the boundary unit is positioned at the downstream, assigning values to the units with the number of layers specified at the downstream by adopting an extrapolation mode.
3. The method for updating the time-space hybrid propulsion disturbance domain of the circumfluence of the supersonic aircraft according to claim 1, wherein the specific method for solving the Euler equation in the convection dynamic domain by using the time propulsion method in the step S2-3 comprises:
s2-3-1: residual estimation: estimating the convection flux of all grid directions in an Euler equation by adopting a convection flux format;
s2-3-2: time integration: and (3) dispersing time-related terms in the Euler equation by adopting a time integral format, and updating the conservation quantity updating quantity and the conservation quantity of the units in the flow dynamic domain.
4. The method for updating the disturbance domain of the time-space hybrid propulsion of the streaming of the supersonic aircraft according to claim 1, wherein the specific method for solving the Euler equation in the convection dynamic domain by using the space propulsion method in step S4-3 comprises:
s4-3-1: residual estimation: estimating a spatial derivative in a non-spatial propelling direction in an Euler equation by adopting a convection discrete format, and calculating a source term of a spatial propelling method;
s4-3-2: space propulsion: and (3) dispersing the virtual time item in the control equation by adopting a time integral format, and updating the conservation quantity updating quantity and the conservation quantity of the units in the convection dynamic domain.
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