CN111523239B - Object plane automatic slicing and data extraction method for CFD flow field post-processing - Google Patents

Object plane automatic slicing and data extraction method for CFD flow field post-processing Download PDF

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CN111523239B
CN111523239B CN202010341121.8A CN202010341121A CN111523239B CN 111523239 B CN111523239 B CN 111523239B CN 202010341121 A CN202010341121 A CN 202010341121A CN 111523239 B CN111523239 B CN 111523239B
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slice
data
flow field
end point
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CN111523239A (en
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赵莹
孙岩
孟德虹
江盟
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Computational Aerodynamics Institute of China Aerodynamics Research and Development Center
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Abstract

The invention discloses an object plane automatic slicing and data extraction method for structural grid CFD flow field post-processing, which reduces the manual participation of object plane slicing, can realize full-automatic slicing and data extraction of any multiple sections of the object plane of a structural grid through input parameter definition, constructs a point-by-point search sorting algorithm, completes the single-cycle direction automatic sorting of section slice extraction data points, outputs object plane section flow field data for quantitative calculation or analysis, and adjusts the three-dimensional display effect of the section extraction data through a spatial scaling factor. The invention can determine the object plane grid block, the intersected quadrilateral grid unit and the intersected grid unit line of the slice plane by only one-time data traversal, and the adopted segmentation calculation method has small calculation amount and strong practicability.

Description

Object plane automatic slicing and data extraction method for CFD flow field post-processing
Technical Field
The invention belongs to the technical field of aerodynamic computation, and particularly relates to the field of extraction and analysis of CFD (computational fluid dynamics) numerical simulation results of aerospace aircrafts.
Background
By means of the rapid development of computer hardware systems, Computational Fluid Dynamics (CFD) is widely applied to numerous engineering fields, such as aviation, aerospace, energy, traffic, and the like. The continuous development of the CFD simulation capability continuously pushes the updating and upgrading of the design mode of the aircraft in the aviation/aerospace field, greatly shortens the development period of the aircraft, and plays an increasingly important role in the design of the aircraft. The post-processing of the CFD simulation flow field is an important way for analyzing numerical calculation data and acquiring the key flow characteristics of the aircraft, and is an important component of CFD simulation software. In the post-processing analysis of the flow field, the flow data such as pressure, friction resistance, heat flow and the like at the specific section position of the object surface can be extracted to quantitatively calculate key flow characteristics such as the position of the separation area, the size of the separation area, the position of the shock wave, the strength of the shock wave, the distribution of the spanwise load and the like, the aerodynamic characteristics of the aircraft are analyzed, the optimization and performance improvement of the design scheme of the aircraft are supported, and the method is a technology widely used in the post-processing of the CFD flow.
At present, CFD flow field object plane data extraction is mainly realized in third-party software in a manual slicing mode, cross section positions are defined manually, and then flow field data of object plane cross sections are obtained through successive slicing. The manual method can realize the slicing of the section at any position, has good section selection and control capability, but has two obvious defects, one is that the position of the section needs to be manually selected, a large amount of manual participation exists, the process automation cannot be realized, and the data extraction efficiency is low; secondly, the data of the section plane is not sorted, and the dot sequence is disordered when the data are displayed in a connecting line mode.
Disclosure of Invention
The invention provides an object plane automatic slicing and data extracting method for CFD flow field post-processing aiming at the problem of extracting object plane data of a CFD flow field by a manual slicing method, reduces manual participation of object plane slicing, can realize full-automatic slicing and data extraction of any plurality of sections of a structural grid object plane through input parameter definition, constructs a point-by-point searching sequencing algorithm, completes single-cycle direction automatic sequencing of section slice extraction data points, outputs object plane section flow field data for quantitative calculation or analysis, and adjusts the three-dimensional display effect of the section extraction data through a space scaling factor.
In order to achieve the purpose, the invention adopts the following technical scheme:
an object plane automatic slicing and data extraction method for CFD flow field post-processing comprises the following steps:
s1 definition ofNumber of cross sections n of slicesliceAnd slice plane position locslice. Slice plane position locsliceThree-dimensional coordinate (X) of a point passing in a plane0,Y0,Z0) Normal vector norm (n) of the sum planex,ny,nz) A description will be given.
S2: according to the slice plane position parameter locsliceAnd traversing all object plane grid blocks, finding out all object plane grid blocks intersected with the slice plane, and marking. Traversing all grid nodes of the object plane grid block, and calculating the projection of the grid nodes in the normal direction of the tangent plane if the grid nodes (x) existi,yi,ziC) projection PiProjection P of the 1 st grid point of the grid block1Different sign (P)iP1≦ 0), the object plane grid block is marked as the intersecting grid block for this slice, and the traversal loop exits. Otherwise PiP1>And 0, not marking the object plane grid block. The projection of the grid points (x, y, z) in the normal direction of the slice plane is calculated as follows:
P＝nx(x-X0)+ny(y-Y0)+nz(z-Z0)
s3: and traversing all quadrilateral units in the object plane grid block marked by the slice according to the node storage sequence, finding out all quadrilateral units intersected with the slice plane through an intersection algorithm, and marking. Traversing all quadrilateral units in the marked grid block, and calculating the maximum value P of the normal projection of 4 grid points of the quadrilateral units on the slice planemaxAnd a minimum value PminIf P is presentmaxAnd PminDifferent sign (P)maxPmin≦ 0), the quadrilateral cell is marked as an intersecting cell for the slice, otherwise if there is P presentmaxAnd PminBoth positive and both negative, the quadrilateral elements are not labeled.
S4: calculating linear weighting coefficients coe for intersection points of slice planes and edges of labeled quadrilateral elements1And coe2. Traversing each grid ridge along the node numbering sequence of the marked quadrilateral units, and calculating two end points of the ridge on the slice planeProjection P1、P2. If P is1P2The number of the ridge lines is less than or equal to 0, and intersection points exist between the ridge lines and the slicing planes; otherwise P1P2>0, there is no intersection between the ridge and the slice plane. For the case of intersection points, the linear weighting coefficients coe of the intersection points with respect to the edge line end points1And coe2The calculation is as follows:
Figure GDA0002991702930000021
Figure GDA0002991702930000022
s5: and assembling a linear weighting coefficient vector Coe (4) of the intersection point relative to the quadrilateral unit node. The ridge where the intersection point is located is the ith ridge of the quadrilateral unit, and the linear weighting coefficient vector can be assembled as follows:
Figure GDA0002991702930000023
s6: and linearly connecting the slice plane with two intersection points of the intersected quadrilateral units to construct a slice linear unit, and calculating the geometric coordinates and the center point coordinates of two end points of the slice linear unit.
Figure GDA0002991702930000031
XYZCenter＝(XYZ1+XYZ2)/2
S7: and extracting CFD flow field data stored on the intersected quadrilateral grid unit to a slice linear unit. If the CFD flow field data adopts a unit center storage mode, directly assigning the flow field data of the quadrilateral unit where the slice linear unit is located to the slice linear unit; if the CFD flow field data adopts a unit node storage mode, the flow field variable value of the end point position of the slice linear unit is calculated by utilizing the linear weighting coefficient vector Coe (4), and then the flow field variable value of the central position of the slice linear unit is obtained by arithmetic mean.
Figure GDA0002991702930000032
VarCenter＝(Var1+Var2)/2
S8: position of slice locsliceIs transformed to the XOY plane using coordinates. For each linear element vector p, a unit quaternion q is found, there is a rotation axis u (where u is the unit vector of the rotation axis), and rotation by an angle θ about the u axis rotates the three-dimensional linear element p into an XOY planar linear element p', when the quaternion representing the rotation is as shown in equation (6). A pure quaternion P (0, P) is constructed, the linear element vector to the XOY plane after rotation is P', the pure quaternion after rotation is P (0, P), and the calculation process is shown in formula (7).
q＝cos(θ/2)+usin(θ/2)
P'＝qPq-1
S9: firstly, circularly comparing the size of the coordinate position of the end point in the X direction of each linear unit in sequence in all the slice unit data, and taking the unit where the minimum value of the coordinate value in the X direction is found out as an initial unit.
S10: and then comparing the coordinate size of the front and rear end points of the starting unit in the Y direction, if the Y coordinate value of the front end point of the starting unit is smaller than the Y coordinate value of the rear end point, finding out the front end point of the connecting unit and connecting the rear end point of the starting unit, wherein the unit connecting mode is clockwise sequencing. If the Y coordinate value of the front end point of the starting unit is larger than the Y coordinate value of the rear end point, the front end point of the connecting unit found out next is connected with the rear end point of the starting unit, and the unit connecting mode is anticlockwise sequencing connection.
S11: and then, circularly judging whether the coordinate values of the three directions of the front and rear end points XYZ of each unit in all the units except the initial unit are equal to the coordinate values of the corresponding directions of the rear end points XYZ of the initial unit. And if the sum of the absolute values of the difference values of the corresponding direction coordinate values of the XYZ front end point and the initial unit rear end point is less than 1.0e-5, the two end points are equal, and the front end point of the unit is connected with the rear end point of the initial unit for sorting. If the sum of the absolute values of the difference values of the corresponding direction coordinate values of the rear end point of a certain unit and the rear end point XYZ of the starting unit is less than 1.0e-5, the position and the size of the front end point of the unit are exchanged with the rear end point, and then the front end point of the unit and the rear end point of the starting unit are connected and sequenced. And searching the next unit connected with the last connected unit in all the units with the removed sorting units in sequence.
S12: when the data are circulated to the last connecting unit in all the units, if the sum of absolute values of differences between coordinate values of three directions of the rear endpoint XYZ of the unit and coordinate values of the corresponding directions of the front endpoint XYZ of the starting unit is less than 1.0e-5, the slicing unit data which are sequenced in the same direction (clockwise or anticlockwise) are closed areas, otherwise, the slicing unit data are not closed and open areas exist.
S13: at this time, if the sorted slice unit data in S12 includes all slice unit data, the slice data subjected to slice normalization has only one closed or non-closed unit data region. If the sorted slice unit data in S12 does not include all slice unit data, and if there is any unregulated unit data, the loop goes through S9 to S12 to obtain all regulated slice data of the slice plane.
S14: the linear unit coordinates of the slice normalized and sorted on the XOY plane are converted into an original XYZ three-dimensional space coordinate system by quaternion rotation.
S15: and circularly executing S2-S14 to obtain the normalized sorting data of all the slices.
S16: and according to the requirements of post-processing display and data analysis, merging the flow field variable data information into the position coordinate data, and outputting the slice data displayed in the three-dimensional space through the space scaling information.
When outputting a slice data format displayed in a three-dimensional space, if CFD flow field data adopts a unit center storage mode, directly assigning the flow field data of a quadrilateral unit where a slice linear unit is located to each slice linear unit; if the CFD flow field data adopts a unit node storage mode, the flow field variable values of the end points of the linear units of the slices are calculated by using the linear weighting coefficient vector Coe (4), and then the flow field variable values of the central positions of the linear units of each slice are obtained by arithmetic mean.
The position coordinate data is obtained as follows, the normal vector norm (n) of two end points of each linear unit and the planex,ny,nz) The parallel coordinate values are expressed by the coordinates of the center point of the linear unit of the slice, and the normal vector norm (n) of the plane isx,ny,nz) The vertical coordinate value adopts the data extracted by adjusting the slice through a space scaling factor, and is used for quantitatively calculating or analyzing the data of the object plane section flow field. The position point of each linear unit is determined by three coordinate values. Three-dimensional spatial display results of all slices are obtained.
In summary, due to the adoption of the technical scheme, the invention has the beneficial effects that:
according to the position connection relation and the data structure characteristics of extracted object plane grid nodes, object plane grid blocks, intersected quadrilateral grid units and intersected grid unit lines of a slice plane can be determined by only one-time data traversal, a reordering method is adopted, all slice unit data obtained at each slice position are normalized and ordered according to the same direction, flow field data of the slice units after normalized and ordered are rapidly extracted, flow field variable information is merged into position coordinate data, slice data displayed in a three-dimensional space is output through space scaling control, and the adopted segmentation calculation method is small in calculation amount and strong in practicability.
Drawings
The invention will now be described, by way of example, with reference to the accompanying drawings, in which:
FIG. 1 shows the slice position ZsliceA top view of the object plane grid block passing through;
FIG. 2 shows the slice position ZsliceA top view of the passing quadrilateral mesh cells;
FIG. 3 shows slice position ZsliceA quadrangular grid unit line top view is penetrated;
FIG. 4 is a schematic diagram of interpolation solution of front and rear endpoint positions of a slice linear unit;
FIG. 5 is a schematic view showing the sorting direction of the slicing unit;
FIG. 6 is a diagram illustrating the sorting results of the slicing units;
FIG. 7 is a schematic representation of the lift coefficient of a plurality of cut plane cut airfoils;
wherein: a represents a grid node, and the following numbers represent the node number; z represents a projection point corresponding to the grid node A in the normal direction of the tangent plane; c denotes a grid cell composed of grid points, and the following numbers denote the grid cell numbers; i denotes the row number (increasing upwards); j represents a column number (increasing to the right); (i, j) represents a grid intersection point identification;
1 is the slice position Zslice(ii) a 2 is a grid block one; 3 is a grid block two; 4 is lattice block three; 21 is the grid block-the first grid point (x)i,yi,ziB) of the group A and B); 22 is a grid block-grid point (x)i,yi,ziB) of the group A and B); 31 is the second first grid point (x) of the grid blocki,yi,ziB) of the group A and B); 32 is a grid block two grid point (x)i,yi,ziB) of the group A and B); 41 is the first grid point (x) of the grid blocki,yi,ziB) of the group A and B); 51 is a grid cell line one; 52 is a grid cell line two; 53 is a grid cell line three; 54 is grid cell line four; 61 is the front intersection of linear element one; 62 is the rear intersection of linear element one; 71 is a linear unit one; 72 is linear element two; 73 is linear unit three; 74 is linear element four; 75 is linear element five; 81 is a linear unit I of the intersection of the slice and the object plane grid block I; 82 is linear element two; 83 is linear element three; 84 is linear element four; 85 is linear element five; 86 is linear element six; 91 is the starting unit of the normalized slice data; 92 is a unit connected to the start unit of the normalized slice data; 93 is the last connected element of the normalized slice data region.
Detailed Description
All of the features disclosed in this specification, or all of the steps in any method or process so disclosed, may be combined in any combination, except combinations of features and/or steps that are mutually exclusive.
Any feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving equivalent or similar purposes, unless expressly stated otherwise. That is, unless expressly stated otherwise, each feature is only an example of a generic series of equivalent or similar features.
Firstly, defining the number n of sections to be slicedsliceAnd slice plane position Zslice. Slice plane position ZsliceThree-dimensional coordinate (X) of a point passing in a plane0,Y0,Z0) Normal vector norm (n) of the sum planex,ny,nz) A description will be given.
In FIG. 1, according to slice position ZsliceTraversing all object plane grid blocks to find all and slice positions ZsliceAnd (5) grid blocks of the intersected object planes and marking. Traversing all grid nodes of the object plane grid block, calculating the projection of the grid nodes in the normal direction of the tangent plane, wherein the grid block I has a grid point (x)i,yi,ziA projection Z of-iWith the first grid point (x) of the grid blocki,yi,ziA projection Z of-1Different sign (Z)iZ1≦ 0), mark the grid block one as this slice position ZsliceThe two grid blocks have grid points (x)i,yi,ziA projection Z of-iFirst grid point (x) of grid blocki,yi,ziA projection Z of-1Different sign (Z)iZ1≦ 0), mark grid block two as this slice plane position ZsliceAnd exiting the traversal loop. Whereas grid block three does not have grid point (x)i,yi,ziA projection Z of-iProjection Z with three first grid points of grid block1Different sign (Z)iZ1>0) The grid block three is not marked. The projection of the grid points (x, y, z) in the normal direction of the slice plane is calculated as follows:
Z＝nz(z-Z0)
in fig. 2, in the object plane grid block marked by the slice, all quadrilateral units are traversed according to the node storage order, and all the positions Z of the quadrilateral units and the slice are found through an intersection algorithmsliceIntersecting quadrilateral elements and marking. Traversing all quadrilateral units in the marked grid block, and calculating the slicing position Z of four grid points of the quadrilateral unitssliceMaximum Z of plane normal projectionmaxAnd minimum value ZminIf Z is presentmaxAnd ZminDifferent sign (Z)maxZmin≦ 0), the quadrilateral element is marked as an intersecting element of the slice, whereas if Z is present, Z is marked as an intersecting element of the slicemaxAnd ZminAnd the quadrilateral grid cells marked in the first grid block are B1, B2, B3, B4, B5 and B6, and the quadrilateral grid cells marked in the second object plane grid block are C1, C2, C3, C4 and C5.
In FIG. 3, the linear weighting coefficients coe for the intersection of the slice plane and the edge lines of the marker quadrilateral elements are calculated1And coe2. Traversing each grid ridge along the node numbering sequence of the marked quadrilateral units, and calculating the positions Z of two endpoints of the ridge at the slicing positionssliceProjection Z in the normal direction of the plane1、Z2. If Z is1Z2The number of the ridge lines is less than or equal to 0, and intersection points exist between the ridge lines and the slicing planes; otherwise Z1Z2>0, there is no intersection between the ridge and the slice plane. Traverse slice position ZsliceCalculating the projection Z of two endpoints of the edge line on the slice plane with each grid edge line of the quadrilateral grid unit marked in the object plane grid block II and the grid block I1、Z2. If Z is1Z2The number of the ridge lines is less than or equal to 0, and intersection points exist between the ridge lines and the slicing planes; otherwise Z1Z2>0, there is no intersection between the ridge and the slice plane. For the case of intersection points, the slice plane is linearly connected with two intersection points of the intersected quadrilateral units to construct slice linear units, and the slice position ZsliceThe linear unit I, the linear unit II, the linear unit III, the linear unit IV and the linear unit V are constructed with the grid block II, the linear unit I is intersected with the grid block I, the linear unit II is intersected with the slice and object plane grid block I, and the linear unit III, the linear unit IV, the linear unit V and the linear unit VI are constructed with the slice and object plane grid block I. The data of the slice units are arranged out of order。
In fig. 4, for the case where there is an intersection, the slice position ZsliceLinear weighting coefficient coe of intersection point of front end of linear unit and intersection point of back end of linear unit formed by intersection with grid unit C1 relative to edge line end point1And coe2The calculation is as follows:
Figure GDA0002991702930000071
Figure GDA0002991702930000072
and assembling a linear weighting coefficient vector Coe (4) of the intersection point relative to the quadrilateral unit node. The ridge where the intersection point is located is the ith ridge of the quadrilateral unit, and the linear weighting coefficient vector can be assembled as follows:
Figure GDA0002991702930000073
and linearly connecting the slice plane with two intersection points of the intersected quadrilateral units to construct a slice linear unit, and calculating the geometric coordinates and the center point coordinates of two end points of the slice linear unit.
Figure GDA0002991702930000074
XYZCenter＝(XYZ1+XYZ2)/2
And extracting CFD flow field data stored on the intersected quadrilateral grid unit to a slice linear unit. If the CFD flow field data adopts a unit center storage mode, directly assigning the flow field data of the quadrilateral unit where the slice linear unit is located to the slice linear unit; if the CFD flow field data adopts a unit node storage mode, the flow field variable value of the end point position of the slice linear unit is calculated by utilizing the linear weighting coefficient vector Coe (4), and then the flow field variable value of the central position of the slice linear unit is obtained by arithmetic mean.
Figure GDA0002991702930000075
VarCenter＝(Var1+Var2)/2
Position of slice locsliceIs transformed to the XOY plane using coordinates. For each linear element vector p, a unit quaternion q is found, there is a rotation axis u (where u is the unit vector of the rotation axis) and rotation by an angle θ about the u axis rotates the three-dimensional linear element p into the XOY plane but linearly wishes p', when the quaternion representing the rotation is as shown in the formula. A pure quaternion P ═ P,0 is constructed, the linear element vector to the XOY plane after rotation is P ', the pure quaternion after rotation is P ═ P',0, and the calculation process is shown in the formula.
q＝cos(θ/2)+usin(θ/2)
P'＝qPq-1
In FIG. 5, slice position Z is setsliceAll the obtained slice unit data are sorted according to the same direction (clockwise or anticlockwise), and normalized slice data are obtained.
In fig. 5, a compares the coordinate positions of the front and rear end points of each linear unit in turn in a cyclic manner in all the slice unit data, and takes the unit where the minimum value of the X-direction coordinate value is found as the starting unit of the normalized slice data. And then comparing the Y-direction coordinates of the front and rear end points of the starting unit, wherein the Y-direction coordinate value of the front end point of the starting unit is smaller than the Y-direction coordinate value of the rear end point, and finding out the unit front end point connected with the starting unit of the normalized slice data and connecting the unit front end point with the rear end point of the starting unit, wherein the unit connection mode is clockwise sequencing. As shown in b of fig. 5, if the Y coordinate value of the front end point of the start unit is greater than the Y coordinate value of the back end point, the front end point of the start unit connected with the start unit of the normalized slice data is then connected with the back end point of the start unit, and the connection manner of the start unit and the back end point is counterclockwise sorted.
In fig. 6, XYZ tristimulus values of front and rear end points of each cell in all cells excluding the start cell of the normalized slice data are cyclically dividedWhether the coordinate values of the directions are equal to the coordinate values of the directions corresponding to the starting unit rear end point XYZ or not. If the sum of absolute values of the difference values of the XYZ corresponding direction coordinate values of the front end point of a certain unit and the rear end point of the starting unit is less than 1.0e-5If the two endpoints are equal, the front endpoint of the unit connected with the start unit of the normalized slice data is connected with the rear endpoint of the start unit for sorting. If the sum of absolute values of the difference values of the XYZ corresponding direction coordinate values of the rear end point of the unit connected with the start unit of the normalized slice data and the rear end point of the start unit is less than 1.0e-5Then, the front end point and the rear end point of the connection unit are exchanged in position and size, and then the front end point and the rear end point of the start unit are connected and sequenced. And sequentially searching all the slice units with the sorting units removed for the next unit connected with the last connected unit.
As shown in a of fig. 6, when the loop is performed to the last connected cell of the region where the slice data is normalized among all the slice cells, the sum of the absolute values of the differences between the coordinate values of the three directions of the rear end point XYZ of the last connected cell and the coordinate values of the corresponding directions of the front end point XYZ of the start cell is less than 1.0e-5Then the normalized slice unit data is a closed region sorted in the same direction (clockwise), otherwise, as shown in b in fig. 6, the normalized slice unit data is not closed, and an open region exists. At this time, if the sorted slice unit data includes all slice unit data, the slice position Z is the slice positionsliceThe normalized slice data only has one closed or non-closed cell data region. If the sorted slice unit data does not contain all slice unit data and there are no sorted units, the circular sorting algorithm is used to obtain the slice position ZsliceAll normalized slice data. Then the slice position ZsliceAnd converting the linear unit coordinates subjected to the normalization sorting on the XOY plane into an original XYZ three-dimensional space coordinate system by utilizing quaternion rotation.
As shown in fig. 7 for a plurality of slice data displayed in three-dimensional space, the information of the flow field variable data is merged into the position coordinate data according to the requirements of post-processing display and data analysis, and the merged information is output through spatial scaling information.
When outputting a slice data format displayed in a three-dimensional space, if CFD flow field data adopts a unit center storage mode, directly assigning the flow field data of a quadrilateral unit where a slice linear unit is located to each slice linear unit; if the CFD flow field data adopts a unit node storage mode, the flow field variable values of the end points of the linear units of the slices are calculated by using the linear weighting coefficient vector Coe (4), and then the flow field variable values of the central positions of the linear units of each slice are obtained by arithmetic mean.
The position coordinate data is obtained as follows, the normal vector norm (n) of two end points of each linear unit and the planex,ny,nz) The parallel coordinate values are expressed by the coordinates of the center point of the linear unit of the slice, and the normal vector norm (n) of the plane isx,ny,nz) The vertical coordinate value adopts the data extracted by adjusting the slice through a space scaling factor, and is used for quantitatively calculating or analyzing the data of the object plane section flow field. The position point of each linear unit is determined by three coordinate values. Three-dimensional spatial display results of all slices are obtained.
The invention is not limited to the foregoing embodiments. The invention extends to any novel feature or any novel combination of features disclosed in this specification and any novel method or process steps or any novel combination of features disclosed.

Claims (10)

1. An object plane automatic slicing and data extraction method for CFD flow field post-processing is characterized by comprising the following steps:
s1, defining the number of the sections to be sliced and the position of the slicing plane;
s2, traversing all object plane grid blocks according to the position parameters of the slice plane, finding out all object plane grid blocks intersected with the slice plane, and marking;
s3, traversing all quadrilateral units according to the node storage sequence in the object plane grid block marked by the slice, finding out all quadrilateral units intersected with the slice plane through an intersection algorithm, and marking;
s4: calculating linear weighting coefficients coe1 and coe2 of intersection points of the slicing plane and the edges of the marked quadrilateral cells, traversing each grid edge along the node number sequence of the marked quadrilateral cells, calculating projections P1 and P2 of two end points of the edges on the slicing plane, and calculating linear weighting coefficients coe1 and coe2 of the intersection points relative to the end points of the edges as follows:
Figure DEST_PATH_IMAGE002
Figure DEST_PATH_IMAGE004
s5: assembling a linear weighting coefficient vector Coe (4) of the intersection point relative to the quadrilateral unit node, recording the ridge line where the intersection point is located as the ith ridge line of the quadrilateral unit, and assembling the linear weighting coefficient vector as follows:
Figure DEST_PATH_IMAGE006
s6, linearly connecting the slice plane with two intersections of the intersecting quadrilateral units to construct a slice linear unit, and calculating the geometric coordinates and the center point coordinates of two end points of the slice linear unit;
s7, extracting CFD flow field data stored in the intersected quadrilateral grid unit to a slice linear unit;
s8, transforming all the linear unit data of the slice position to an XOY plane by using coordinates;
s9, sequentially and circularly comparing the coordinate position of the end point X direction of each linear unit in all the slice unit data, and taking the unit where the minimum value of the coordinate value in the X direction is found out as an initial unit;
s10, comparing the coordinate of the front and back end points of the initial unit in the Y direction;
s11, circularly judging whether the coordinate values of the three directions of the front and rear end points XYZ of each unit in all the units except the starting unit are equal to the coordinate values of the corresponding directions of the rear end points XYZ of the starting unit;
s12 judging the unit when circulating to the last connection unit in all unitsThe sum of the absolute values of the differences between the coordinate values of the rear end point XYZ in three directions and the coordinate values of the start unit front end point XYZ in the corresponding directions is 1.0e-5The size of (d);
s13, judging whether the data of the sorted slice units in the S12 contain all the data of the slice units;
s14: converting the linear unit coordinates of the slice in the XOY plane through normalization sorting into an original XYZ three-dimensional space coordinate system by utilizing quaternion rotation;
s15, circulating S2-S14 to obtain the normalized sorting data of all slices;
and S16, according to the requirements of post-processing display and data analysis, merging the flow field variable data information into the position coordinate data, and outputting the slice data displayed in the three-dimensional space through the space scaling information.
2. The method for object plane automatic slicing and data extraction for CFD flow field post-processing according to claim 1, wherein in S2:
traversing all grid nodes of the object plane grid block, if the projection of the grid point is different from the projection of the first grid point of the grid block, marking the object plane grid block as the intersected grid block of the section, and exiting the traversal loop, otherwise, not marking the object plane grid block.
3. The method for object plane automatic slicing and data extraction of CFD flow field post-processing according to claim 1 or 2, characterized in that in S3:
traversing all quadrilateral units in the marked grid block, calculating the maximum value and the minimum value of the four grid points of the quadrilateral units projected in the normal direction of the slice plane, if the maximum value and the minimum value have opposite signs, marking the quadrilateral units as the intersection units of the slices, otherwise, if the maximum value and the minimum value are both positive or both negative, not marking the quadrilateral units.
4. The method for object plane automatic slicing and data extraction of CFD flow field post-processing according to claim 3, wherein in S4:
traversing each grid ridge along the node numbering sequence of the marked quadrilateral units, calculating the projection of two endpoints of the ridge on the slicing plane, if the two projections have different signs, the ridge and the slicing plane have an intersection point, otherwise, the ridge and the slicing plane do not have an intersection point.
5. The method for object plane automatic slicing and data extraction for CFD flow field post-processing according to claim 1, wherein in S7:
if the CFD flow field data adopts a unit center storage mode, directly assigning the flow field data of the quadrilateral unit where the slice linear unit is located to the slice linear unit;
if the CFD flow field data adopts a unit node storage mode, the flow field variable value of the end point position of the slice linear unit is calculated by utilizing the linear weighting coefficient vector, and then the flow field variable value of the central position of the slice linear unit is obtained by arithmetic mean.
6. The method for object plane automatic slicing and data extraction of CFD flow field post-processing according to claim 5, wherein in S8:
for each linear element vector, a unit quaternion is found, and rotation about the rotation axis causes the three-dimensional linear element to rotate into an XOY planar linear element.
7. The method for object plane automatic slicing and data extraction for CFD flow field post-processing according to claim 1, wherein in S10:
if the Y coordinate value of the front end point of the starting unit is smaller than the Y coordinate value of the rear end point, the connection mode of the front end point of the unit and the rear end point of the starting unit is clockwise sequencing;
if the Y coordinate value of the front end point of the starting unit is larger than the Y coordinate value of the rear end point, the connection mode of the front end point of the unit and the rear end point of the starting unit is anticlockwise sequencing connection.
8. The method for object plane automatic slicing and data extraction for CFD flow field post-processing according to claim 7, wherein in S11:
if any unit front end point and the starting unit rear end pointXYZThe sum of absolute values of the differences of the coordinate values corresponding to the directions is less than 1.0e-5If the two end points are equal, the front end point of the unit is connected with the rear end point of the starting unit for sequencing;
if any unit back end point and the starting unit back end pointXYZThe sum of absolute values of the differences of the coordinate values corresponding to the directions is less than 1.0e-5Then, the front end point and the rear end point of the unit are exchanged in position and size, and then the front end point and the rear end point of the starting unit are connected and sequenced.
9. The method for object plane automatic slicing and data extraction for CFD flow field post-processing according to claim 8, wherein in S12:
if the sum of absolute values of the differences is less than 1.0e-5If the data of the slice units sorted according to the same direction is a closed area;
if the sum of absolute values of the differences of the coordinate values is more than 1.0e-5Then the slice unit data is unclosed and an open region exists.
10. The method for object plane automatic slicing and data extraction of CFD flow field post-processing according to claim 1 or 9, wherein in S13:
if the sorted slice unit data in S12 does not include all slice unit data, the loop goes through steps S9 to S12 to obtain all the normalized slice data of the slice plane.
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