Efficient nested grid host unit searching method in aircraft dynamic flow field analysis

A search method and aircraft technology, applied in the field of efficient nested grid host cell search, can solve problems such as unbalanced tree structure, reduced search host cell efficiency, and increased depth, so as to improve efficiency, reduce intersection judgment tasks, and reduce small depth effect

Active Publication Date: 2022-03-01
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AI-Extracted Technical Summary

Problems solved by technology

But when dealing with large-scale grids, the tree structure of ADT will be extremely unbalanced, and th...
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Method used

[0075] As shown in FIG. 3, this embodiment is used to test the comparison of Bookkeeping ADT method with respect to conventional ADT method in terms of host unit search and nested grid assembly efficiency. The test example is based on a grid system with a unit scale of about 50 million (4 sets of 10 million sub-grids surrounding the sphere, and 1 set of background grids with about 10 million units). As shown in Figure 4, compared with the conventional ADT method (ND = 1), the Bookkeeping ADT method significantly improves the nested grid assembly speed. With the increase of the number of divisions ND, the Bookkeeping ADT method of the overall ADT strategy can increase the speed 8-9 times or more, and the speed of the local ADT strategy can be increased by more than 3-4 times. From the absolute task time of nested grid assembly shown in Figure 5, when the ND is large enough, the task time of the overall ADT strategy and the local A...
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The invention provides an efficient nested grid host unit searching method in dynamic flow field analysis of an aircraft, which comprises the following steps of: creating more than one sub-ADT tree of a series for grid units in a given area, and registering storage addresses of the sub-ADT trees to a register book in an array form; firstly, grid points to be checked are freeze-framed on sub-ADT corresponding to a specific local area according to coordinate positions of the grid points to be checked, then corresponding host units of the grid points to be checked are searched in a conventional ADT mode, and therefore multiple sets of mutually-nested grids are assembled, and aircraft dynamic motion flow field analysis is carried out. According to the method, the depth of each sub ADT is greatly reduced, so that each sub ADT tree structure has better balance, meanwhile, the to-be-searched point is quickly positioned to a very small local area, the area range searched by the host unit is reduced, the search time is effectively reduced, and the numerical simulation time of the dynamic motion process of the aircraft is shortened.

Application Domain

Sustainable transportationDesign optimisation/simulation +3

Technology Topic

Flight vehicleMesh point +9


  • Efficient nested grid host unit searching method in aircraft dynamic flow field analysis
  • Efficient nested grid host unit searching method in aircraft dynamic flow field analysis
  • Efficient nested grid host unit searching method in aircraft dynamic flow field analysis


  • Experimental program(1)

Example Embodiment

[0043] Next, the technical solutions in the embodiments of the present invention will be described in conjunction with the drawings in the embodiment of the present invention, and it is clearly, and it is understood that the described embodiments are merely the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art are in the range of the present invention without making creative labor premise.
[0044] The present invention disclosed one of the aircraft dynamic flow field analysis method, such as figure 1 As shown, including the following steps S10-S100:
[0045] S10, based on engineering object geometry model, generating N-sets of none-nested fluid computing grids, fluid computing grids can be arbitrary type, such as tetrahedral, hexahedral, multi-facete.
[0046] S20, calculate the boundary box size of each grid unit, and count the maximum boundary area of ​​each set of grids, for each grid unit, the calculation method of the bounded box size is, in the loop mesh unit M A grid node, from its coordinates ( xyz Determine the three axial minimum and maximum coordinates of the boundary box:. Determine the area of ​​the entire grid by the coordinates of each bounding box Is a minimum coordinate point Logical cube. The pseudo code of this step is as follows:
[0047] 1. For i = 1 to Cellamount DO
[0048] 2. For i = 1 to M DO
[0049] 3. x min = min (x, x min )
[0050] 4. End for
[0051] 5. x Rmin = min (x min , x Rmin )
[0052] 6. End for
[0053] Such as figure 2 In the middle (a), it is assumed that such a set of grids, according to the node coordinates of 10 mesh units, the logical cube of the entire grid, such as the dasket box.
[0054] S30, it is judged whether or not the entire set of grid is established, and then step S31 is executed, otherwise step S32 is performed;
[0055] S31, if the overall bookkeeping ADT is established in the whole set, the maximum boundary area of ​​each set is divided into three axial components. N D × N D × N D Sub-cube i ] [ j ] [ k ]. Logic cube according to the entire grid , Divided into three axial components N D × N D × N D Long width height is δ S Sub cubes, in which N D The number of divisions in a single coordinate direction, D For the space dimension, Then the sizes of the son.
[0056] Sub-cube Sub-Cube I, J (Two-dimensional) or I, J , k (3D) index, each sub-cube SUB-CUBE [ i ] [ j ] [ k ] And the area Associated. It should be noted that these cubes and sub-cubes are only logically, there is no need to create and store them truly.
[0057] S32, if the policy is established based on two nested grids, the largest boundary area of ​​each two sets, calculates the size of the public area of ​​each other, and each public area is along the three Shaft N D × N D × N D Sub-cube i ] [ j ] [ k ]. For two computing grids 1 and 2 in two presence, its logic cubes are and You can get logical cubes of common domains they intersect. for:
[0059] It is then built in the logical cube in the public area, and the method is similar to step S31, and details are not described herein again.
[0060] Such as figure 2 Middle (D), figure 2 The logical cube of (a) is divided into 2 x 2 subcrew.
[0061] S40, for the first n Each computing unit of a set is marked with which a subcube intersects. Boundary box according to each calculation unit It can determine the index of the Sub-Cube intersecting it:
[0063] At this time I, J, K The range of integer coordinates of the smallest coordinate point of the grid boundary box relative logic cube. E.g figure 2 In the middle (E), the grid unit No.1 intersects Sub-Cube [0] [1] and Sub-Cube [1] [1] and Sub-Cube [1] [1], and the mesh unit No.10 is only sub-cube [1] [ 0] intersect.
[0064] S50, for the first n Set of each sub-cube Sub-Cube i ] [ j ] [ k ], All computing units of the set of grids intersecting the grid are deposited in SUB-ADT [ i ] [ j ] [ k ].
[0065] Each Sub-ADT [ i ] [ j ] [ k The establishment process is consistent with the conventional ADT establishment method (such as figure 2 (B) shown in (b)). ADT describes the geometric element as supervitalized coordinates in the supervination space, and the node of each storage geometry element in the tree characterizes a certain supervitalized space area, starting from the root node, and its spatial area is alternately One is divided into two in each supervitalized space direction. For example, in a supervination space, any grid element can be E (Grid Unit or Grid Node) Description as a supervitalized space area R = Overview space coordinates , in The smallest, maximum coordinate value of the envelope, and the largest coordinate value is respectively figure 2 As shown in (a) and (b), based on supervocal coordinates, these mesh elements can be resended in the ADT binary tree in a manner in each direction in the direction of the supervitalized space area.
[0066] Finally, each sub-cube [ i ] [ j ] [ k ] Sub-ADT established based on the mesh unit included in itself i ] [j ] [ k ]Such as figure 2 In the middle (e), you can see the binary tree established compared to the conventional ADT method ( figure 2 Central (B)), each SUB-ADT [ i ] [ j ] [ k The depth of the elements and trees in the tree is greatly reduced, and the equalization is improved.
[0067] S60, judging if all grid processing is completed ( n N), then perform subsequent steps, then return to S40.
[0068] S70, for the first m An arbitrarily destroy point determines that it intersects the maximum boundary area / public area of ​​the grid. This step is a pre-search process, and it is determined whether or not the point is located in a logical cube in a mesh / public area, that is, full:. If you don't satisfy, skip the search tasks of all Bookkeeping ADTs in this logical cube.
[0069] S80, according to the first m An arbitrary coordinate determines which subcrew sub-cube is in the area [ i ] [ j ] [ k ]intersect. Such as figure 2 In the middle (F), the Sub-Cube index is now calculated quickly for the point of viewing. i = 0, j = 0.
[0070] S90, in SUB-CUBE [ i ] [ j ] [ k ] Corresponding SUB-ADT [ i ] [ j ] [ k ] Search m An arbitrary point corresponding to the host unit. The search process is consistent with the search process of the regular ADT, and it is possible to find or treat the grid element q (including the box) from the grid area of ​​the ADT management. For the grid point, ) The intersecting grid unit, the search process starts from the ADT root node and is recursively executed to its sub-nodes, such as figure 2 In the middle (c), in each sub-node that needs to be executed, the intersection is performed.
[0071] ,
[0072] The ADT node has overlap with the destroy element enclosure, and the grid unit corresponding to the node may contain or intersect the destroy element, recorded as a potential intersecting unit, and the recursive search process continues to perform it to its sub-node; otherwise Ignore the current ADT node and all of the subtots, and end the recursive search of the current branch tree. After being searched by ADT, after finding a grid unit intersecting the elements of the design, the accurate geometry or geometric intersection of this small portion of the potential grid unit is found, finding the real container or associated mesh element. Intersection of the mesh unit.
[0073] Compared figure 2 Central (C) and figure 2 In the middle (F), the host unit of the desired point is a mesh unit No. 8. For a conventional ADT method, search for 6 times in the ADT to find the host unit, and Bookkeeping ADT can only find 4 searches. . As the number of mesh is increased, the advantages of Bookkeeping ADT will be more prominent.
[0074] S100, it is determined whether all host unit search processing of all to seek points is completed, and then the search task is ended, and the assembly of multiple sets of nested grid is completed, and the flow field analysis of the aircraft dynamic movement is carried out, and it returns to S70.
[0075] Such as image 3 As shown, this embodiment is used to test the Bookkeeping ADT method relative to the comparative situation of the host unit search and nested grid assembly efficiency relative to the conventional ADT method. The test example is based on a grid system of about 50 million (4 sets of 10 million winding body grid, 1 set of background grids of about 10 million units). Such as Figure 4 As shown, compared to the conventional ADT method ( N D = 1) The bookkeeping ADT method significantly improves the speed of nested mesh assembly, with the number of divisions N D Increased, the speed of the Bookkeeping ADT method of the overall ADT policy increases by 8-9 times, and the speed of local ADT strategy can increase by 3-4 times. From Figure 5 The nested grid shown is in the absolute task time, when N D At sufficient, the overall ADT strategy and the local ADT policy have similar task time. This is because the overall ADT policy manages all units all units all units to the ADT, and each calculation processor is parallel to establish the load balance of ADT, but inevitably manages grid units other than overlapping regions to the ADT. It may increase the selection range of the host unit, so it takes a larger N D And the local ADT policy establishes ADT between the two-two-two-two-two-two-two-two sub-grids to establish an ADT to avoid unnecessary addition of the grid unit other than overlap regions to the ADT to narrow the search area, improve Search efficiency; but when there is a multi-set grid overlap overlap, the region mesh unit may be processed multiple times and simultaneously, and the overlap area is large, and the time consumption of the ADT is established. Relative increase.
[0076] After adequate example test and engineering application example assessment, number of divisions N D The choice, the overall ADT policy takes about 40, local ADT policy 10-15; Overall, local ADT policy enhances the performance of nested grid assembly efficiency relatively more stable, and recommends preferentially using local ADT policies.
[0077] Fig. 6 (a) is a result of nested grid assembly provided by an embodiment of the present invention. Fig. 6 (b) is a flow field situation obtained based on the nested grid assembly, the geometric engineering object contains aircraft fuselage, pair of fuel tanks, missiles, total 17 million grid, 64 thread nested grid assembly consumption 40 seconds, it is 4 times more than the traditional ADT method. The flow field results show that the method is robust and accuracy in the host unit search process.
[0078] The various embodiments in this specification are described in the process, and the same components are described with each other, and each of the embodiments are respectively illustrated. In particular, for the device embodiment, the above is merely the preferred embodiment of the present invention, since it is substantially similar to the method embodiment, the partial description of the method embodiment will be described in relatively simple and related to the method. As described above, only the embodiments of the present invention are described herein, but the scope of the present invention is not limited thereto, and any technicrat will be described in the technical scope of the present invention, and any skilled in the art. For example, it can be easily thought of or replaced, and it should be covered within the scope of the invention without departing from the principles of the invention. Therefore, the scope of the invention should be based on the scope of protection of the claims.


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