CN110162823B - Unsteady aerodynamic force calculation method considering aerodynamic surface effect and normal motion - Google Patents

Unsteady aerodynamic force calculation method considering aerodynamic surface effect and normal motion Download PDF

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CN110162823B
CN110162823B CN201910206454.7A CN201910206454A CN110162823B CN 110162823 B CN110162823 B CN 110162823B CN 201910206454 A CN201910206454 A CN 201910206454A CN 110162823 B CN110162823 B CN 110162823B
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刘燚
刘凯
操小龙
何海波
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Beijing Research Institute of Mechanical and Electrical Technology
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Abstract

The invention provides a method for calculating unsteady aerodynamic force by considering aerodynamic surface effect and normal motion, which comprises the following steps: meshing the deformed pneumatic surface of the aircraft; acquiring a structural elastic mode of the aircraft; extracting a structural elastic mode related to the deformed pneumatic surface and interpolating the structural elastic mode to a pneumatic grid; arranging a dipole basic solution on the grid, solving a kernel function, and solving an aerodynamic influence coefficient matrix according to the kernel function; calculating the local normal vector of the pneumatic grid of the deformed pneumatic surface; solving a normal motion boundary condition according to the normal mode of the deformed pneumatic surface; solving the unsteady aerodynamic force on the aerodynamic surface grid after deformation; and acquiring generalized curved surface unsteady aerodynamic force according to the unsteady aerodynamic force on the deformed aerodynamic surface grid and the normal mode of the deformed aerodynamic surface. By applying the technical scheme of the invention, the technical problem that accurate description and calculation of the frequency domain unsteady aerodynamic force of the flexible aircraft cannot be realized in the prior art is solved.

Description

Unsteady aerodynamic force calculation method considering aerodynamic surface effect and normal motion
Technical Field
The invention relates to the technical field of aeroelasticity of aircrafts, in particular to an unsteady aerodynamic force calculation method considering the curved surface effect and normal motion of an aerodynamic surface.
Background
The calculation of unsteady aerodynamic force is a key link of aircraft design and analysis, and directly influences the assessment of the maneuverability, flight stability and safety of the aircraft. Therefore, unsteady aerodynamic force calculation is an important part of aeroelasticity analysis, servo stability analysis, flight mechanics simulation and flight performance evaluation in the aircraft design link, and the reasonability and accuracy of modeling calculation have important significance on aircraft design and analysis.
With the improvement of modern aircraft design technology, the development of composite material technology, and the development requirements of high-speed long endurance of aircraft, flexible aircraft becomes the hot spot of recent aircraft research. Due to the light weight and the large flexibility, the flexible aircraft can generate large elastic deformation under the action of pneumatic load, and the pneumatic surface is deformed into a space curved surface. The flat plate aerodynamic force calculation commonly adopted by the traditional aeroelasticity analysis cannot reflect the real aerodynamic surface shape of a three-dimensional space and cannot obtain an accurate flow field form, so the aerodynamic load calculation of the flexible aircraft must consider the curved surface effect of the aerodynamic surface. The motion form of the aerodynamic surface needs to be analyzed for unsteady calculation, and for a flexible aircraft, the effective motion component causing unsteady aerodynamic force is not limited to the Z component under a plane configuration any more but is perpendicular to the normal motion component of the local aerodynamic surface configuration at any moment under the influence of a curved surface effect. When the curve effect of the pneumatic surface is obvious, the difference between the Z-direction motion component and the normal motion component is obvious, if the Z-direction motion component of the plane configuration is still adopted to calculate unsteady aerodynamic force, a large error is inevitably caused, and the subsequent flutter analysis and pneumatic servo elasticity analysis are influenced.
Disclosure of Invention
The invention provides an unsteady aerodynamic force calculation method considering aerodynamic surface effect and normal motion, which can solve the technical problem that accurate description and calculation of unsteady aerodynamic force of a flexible aircraft frequency domain cannot be realized in the prior art.
The invention provides an unsteady aerodynamic force calculation method considering aerodynamic surface effect and normal motion, which comprises the following steps: meshing the deformed pneumatic surface of the aircraft; performing structural dynamics analysis on the aircraft to obtain a structural elastic mode of the aircraft; extracting a structural elastic mode related to the deformed aerodynamic surface from structural elastic modes of the aircraft and interpolating the structural elastic mode to a pneumatic grid of the deformed aerodynamic surface; arranging a dipole basic solution on the grid of the deformed aerodynamic surface, solving a kernel function considering the deformation of the aerodynamic surface, and solving an aerodynamic influence coefficient matrix according to the kernel function; calculating the local normal vector of the pneumatic grid of the deformed pneumatic surface; solving the normal mode of the deformed pneumatic surface according to the structural elastic mode of the deformed pneumatic surface and the local normal vector, and solving the normal motion boundary condition according to the normal mode of the deformed pneumatic surface; solving the unsteady aerodynamic force on the aerodynamic surface grid after deformation according to the normal motion boundary condition and the aerodynamic force influence coefficient matrix; and acquiring generalized curved surface unsteady aerodynamic force according to the unsteady aerodynamic force on the deformed aerodynamic surface grid and the normal mode of the deformed aerodynamic surface.
Further, the kernel function considering the aerodynamic surface deformation is
Figure GDA0002693350000000021
λ1＝xi-xjWherein (x)i,yi,zi) Is the coordinates of the receiving point, (x)j,yj,zj) Is the coordinates of the disturbance point and is,
Figure GDA0002693350000000022
niis (x)i,yi,zi) In the normal direction of the airfoil, njIs (x)j,yj,zj) In the normal direction of the airfoil surface, omega is the structural vibration circular frequency, U∞For the far-coming velocity, R' is the distance between the receiving point and the disturbance point, a∞The speed of sound of far-front incoming flow, M∞The incoming flow mach number.
Further, the normal mode f of the deformed pneumatic surface can be obtained by multiplying the structural elastic mode of the deformed pneumatic surface by a local normal vector.
Further, the boundary condition of the normal motion is
Figure GDA0002693350000000031
Wherein w is the mesh dimensionless normal washing speed, k is the reduction frequency, b is the reference chord length, f is the normal mode of the deformed pneumatic surface, n' is the curved surface normal,
Figure GDA0002693350000000032
is the real part of the signal,
Figure GDA0002693350000000033
is the imaginary part.
Further, unsteady aerodynamic forces Δ c on the aerodynamic surface mesh after deformationpAccording to w ═ D Δ cpWhere w is the mesh dimensionless normal wash down velocity, D is the aerodynamic coefficient of influence matrix, Δ cpColumn vectors consisting of unsteady aerodynamic forces of the aerodynamic mesh.
Further, the aerodynamic coefficient of influence matrix D may be based on
Figure GDA0002693350000000034
Is solved, wherein Δ xjIs the median cross-sectional length of the jth cell, ljIs the span length, χ, of the 1/4 chord point of the jth gridjChord line sweep angle of grid 1/4, KijIs a kernel function.
Further, in the step one, the chordwise mesh of the deformed aerodynamic surface is at least larger than 5, and the spanwise mesh can be determined according to the slenderness ratio of the mesh units.
Further, the generalized unsteady aerodynamic force of the curved surface can be obtained by multiplying the unsteady aerodynamic force on the deformed aerodynamic surface grid by the normal mode of the deformed aerodynamic surface.
The technical scheme of the invention provides an unsteady aerodynamic force calculation method considering the aerodynamic surface curve effect and normal motion, aiming at the condition that the aerodynamic surfaces such as a flexible aircraft are obviously deformed, the method introduces the aerodynamic surface normal motion calculation method, accurately describes the unsteady effective motion component of the aerodynamic surface of the spatial curved surface and calculates the unsteady aerodynamic force. Compared with the prior art, the method not only describes the characteristics of the curved aerodynamic force precisely from the aspect of geometry, but also defines the effective motion component of the unsteady aerodynamic force precisely from the aspect of kinematics, and realizes the precise description and calculation of the unsteady aerodynamic force of the frequency domain.
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The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. It is obvious that the drawings in the following description are only some embodiments of the invention, and that for a person skilled in the art, other drawings can be derived from them without inventive effort.
FIG. 1 illustrates a block flow diagram of a method for unsteady aerodynamic force computation that accounts for aerodynamic surface curvature effects and normal motion provided in accordance with a specific embodiment of the present invention;
FIG. 2 illustrates a schematic diagram of a three-dimensional curved aerodynamic surface meshing provided in accordance with a specific embodiment of the present invention;
FIG. 3 illustrates a schematic diagram of a dipole spatial arrangement provided in accordance with a specific embodiment of the present invention;
FIG. 4 shows a schematic diagram of dipole lines, pressure points and wash-down points provided in accordance with a specific embodiment of the present invention;
FIG. 5 illustrates a schematic representation of a curved aerodynamic surface provided in accordance with a specific embodiment of the present invention;
FIG. 6 is a graphical illustration of a V-f curve of the results of a flutter calculation provided in accordance with a particular embodiment of the present invention;
FIG. 7 is a graphical illustration of a V-g plot showing the results of flutter calculations provided in accordance with an embodiment of the present invention.
Detailed Description
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
The relative arrangement of the components and steps, the numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present invention unless specifically stated otherwise. Meanwhile, it should be understood that the sizes of the respective portions shown in the drawings are not drawn in an actual proportional relationship for the convenience of description. Techniques, methods, and apparatus known to those of ordinary skill in the relevant art may not be discussed in detail but are intended to be part of the specification where appropriate. In all examples shown and discussed herein, any particular value should be construed as merely illustrative, and not limiting. Thus, other examples of the exemplary embodiments may have different values. It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, further discussion thereof is not required in subsequent figures.
As shown in fig. 1 to 7, according to an embodiment of the present invention, there is provided a unsteady aerodynamic force calculation method considering an aerodynamic surface curvature effect and a normal motion, the unsteady aerodynamic force calculation method including: meshing the deformed pneumatic surface of the aircraft; performing structural dynamics analysis on the aircraft to obtain a structural elastic mode of the aircraft; extracting a structural elastic mode related to the deformed aerodynamic surface from structural elastic modes of the aircraft and interpolating the structural elastic mode to a pneumatic grid of the deformed aerodynamic surface; arranging a dipole basic solution on the grid of the deformed aerodynamic surface, solving a kernel function considering the deformation of the aerodynamic surface, and solving an aerodynamic influence coefficient matrix according to the kernel function; calculating the local normal vector of the pneumatic grid of the deformed pneumatic surface; solving the normal mode of the deformed pneumatic surface according to the structural elastic mode of the deformed pneumatic surface and the local normal vector, and solving the normal motion boundary condition according to the normal mode of the deformed pneumatic surface; solving the unsteady aerodynamic force on the aerodynamic surface grid after deformation according to the normal motion boundary condition and the aerodynamic force influence coefficient matrix; and acquiring generalized curved surface unsteady aerodynamic force according to the unsteady aerodynamic force on the deformed aerodynamic surface grid and the normal mode of the deformed aerodynamic surface.
By applying the configuration mode, the unsteady aerodynamic force calculation method considering the aerodynamic surface curve effect and the normal motion is provided, aiming at the condition that the aerodynamic surfaces such as a flexible aircraft are obviously deformed, the aerodynamic surface normal motion calculation method is introduced, the unsteady effective motion component of the aerodynamic surface of the spatial curved surface is accurately described, and the unsteady aerodynamic force is calculated. Compared with the prior art, the method not only describes the characteristics of the curved aerodynamic force precisely from the aspect of geometry, but also defines the effective motion component of the unsteady aerodynamic force precisely from the aspect of kinematics, and realizes the precise description and calculation of the unsteady aerodynamic force of the frequency domain.
Specifically, in the present invention, to complete the calculation of the unsteady aerodynamic force in the frequency domain, the deformed aerodynamic surface needs to be first subjected to meshing. The grid division standard can refer to the grid division requirement of a surface element method, generally, the grids are required to be consistent and not staggered along the airflow direction, and the length-to-fineness ratio of the grids is appropriate. The pneumatic surface mesh should not be too dense or too thick. The chord direction grid is at least larger than 5, and the span direction grid can be determined according to the slenderness ratio of grid units.
After meshing the deformed aerodynamic surfaces, structural dynamics analysis of the aircraft is required to obtain structural elastic modes. In the present invention, the structural dynamics analysis of the aircraft can be performed using general commercial software, such as msc.
Further, in the present invention, the structural elastic mode obtained by structural dynamics analysis of the aircraft may be independent of the aerodynamic surface. For example, for an airplane, the aerodynamic surface is a wing, but the structural elasticity modal solution can obtain the modes such as an engine and an undercarriage, which are not related to the aerodynamic surface, so that the modes do not need to be considered when the unsteady aerodynamic force is calculated, and only the structural modes related to the aerodynamic surface are needed. Therefore, the structural elastic mode related to the deformed aerodynamic surface is extracted from the structural elastic modes of the aircraft and interpolated on the aerodynamic mesh of the deformed aerodynamic surface.
Then, arranging the basic dipole solution in the spatial aerodynamic surface grid, the following integral equation should be satisfied for 3/4 chord length points in each grid
Figure GDA0002693350000000071
Wherein the content of the first and second substances,ρ is the incoming flow density, V is the incoming flow velocity, wiFor the wash-down velocity at the chord point of the ith grid 3/4, Δ xjIs the median cross-sectional length of the jth cell, ljThe span length of the past 1/4 chord points for the jth grid (figure)
Figure GDA0002693350000000072
)，
Figure GDA0002693350000000073
Is the sweep angle of the jth mesh (figure)
Figure GDA0002693350000000074
Sweep back angle of) KijIs a kernel function of aerodynamic force calculation, n is the number of the aerodynamic grid blocks of the lifting surface,
Figure GDA0002693350000000075
is the pressure coefficient on the jth grid,
Figure GDA0002693350000000076
and pressure Δ pjThe relationship between is
Figure GDA0002693350000000077
The kernel function taking into account the aerodynamic surface deformation is
Figure GDA0002693350000000078
Figure GDA0002693350000000079
λ1＝xi-xjWherein (x)i,yi,zi) Is the coordinates of the receiving point, (x)j,yj,zj) Is the coordinates of the disturbance point and is,
Figure GDA00026933500000000710
niis (x)i,yi,zi) In the normal direction of the airfoil, njIs (x)j,yj,zj) In the normal direction of the airfoil surface, omega being the structureCircular frequency of vibration, U∞For the far-coming velocity, R' is the distance between the receiving point and the disturbance point, a∞The speed of sound of far-front incoming flow, M∞The incoming flow mach number. In the lift surface of a spatially curved surface, ni，njIs a space arbitrary possible vector, is respectively determined in the local coordinate system of the respective grid,
Figure GDA00026933500000000711
Figure GDA00026933500000000712
related to the shape of the airfoil grid in space (e.g., bending, torsional). The geometric information (such as the dihedral angle, the sweepback angle and the torsion angle) of each grid of the curved surface lifting surface is different, and the geometric information needs to be updated from time to time so as to be suitable for calculating the unsteady aerodynamic force of the curved surface of the large-deformation wing. After the kernel function considering the aerodynamic surface deformation is obtained, a spatial surface dipole influence coefficient matrix D can be calculated according to the kernel function.
After obtaining the kernel function considering the deformation of the aerodynamic surface by calculation, the local normal vector of the curved surface aerodynamic surface mesh needs to be calculated. In particular, the local normal vector of the curved aerodynamic surface mesh may be obtained by cross-multiplying the two vectors of the mesh.
After the local normal vector of the curved pneumatic surface mesh is obtained, the structural elastic mode interpolated to the pneumatic surface is multiplied by the local normal vector to obtain the normal mode of the deformed pneumatic surface. n 'represents a normal vector of which the curved surface aerodynamic mesh S (x, y, z) is 0, (n', x), (n ', y) and (n', z) are included angles between the normal and coordinate axes, and the motion form of the curved surface aerodynamic mesh is assumed to be S (Se)iwtThe normal velocity of the object motion is
Figure GDA0002693350000000081
The formula is a universal curved surface pneumatic grid boundary condition. Normal motion boundary conditions that take into account normal motion correction are
Figure GDA0002693350000000082
Wherein w is the mesh dimensionless normal down-wash speedDegree, k is the reduction frequency, b is the reference chord length, f is the normal mode of the deformed aerodynamic surface, n' is the normal of the curved surface,
Figure GDA0002693350000000083
is the real part of the signal,
Figure GDA0002693350000000084
is the imaginary part.
Having obtained the boundary conditions for normal motion, the equation for the velocity of the wash down at the 3/4 chord length point in each mesh
Figure GDA0002693350000000085
The finishing can obtain w ═ D Δ cpUnsteady aerodynamic forces Δ c on the aerodynamic surface mesh after deformationpAccording to w ═ D Δ cpWhere w is the mesh dimensionless normal wash down velocity, D is the aerodynamic coefficient of influence matrix, Δ cpColumn vectors consisting of unsteady aerodynamic forces of the aerodynamic mesh. Specifically, in the present invention, the aerodynamic coefficient matrix D may be based on
Figure GDA0002693350000000086
Is solved, wherein Δ xjIs the median cross-sectional length of the jth cell, ljIs the span length, χ, of the 1/4 chord point of the jth gridjChord line sweep angle of grid 1/4, KijIs a kernel function.
Further, after acquiring the unsteady aerodynamic force of the curved aerodynamic surface, multiplying the unsteady aerodynamic force on the deformed aerodynamic surface grid by the normal mode of the deformed aerodynamic surface to acquire the generalized curved unsteady aerodynamic force. Therefore, the generalized curved surface unsteady aerodynamic force is obtained. According to the acquired generalized curved surface unsteady aerodynamic force, subsequent flutter analysis or pneumatic servo elasticity analysis can be carried out.
Therefore, the frequency domain unsteady aerodynamic force calculation method considering the aerodynamic surface curve effect and the normal motion is provided, the three-dimensional aerodynamic surface mesh is divided, the geometric characteristics of the bending and torsional deformation of the aerodynamic surface can be accurately described, and the effective normal motion of the unsteady aerodynamic force caused by the curved aerodynamic surface is truly reflected based on the introduction of the local normal mode. The method reflects the characteristics of the curve effect and normal motion in two aspects of modeling calculation and boundary condition determination of the aerodynamic surface, adapts to the calculation requirement of the unsteady aerodynamic force of the curved surface frequency domain of the flexible aircraft, and provides guarantee for the input of the follow-up flutter, aeroelastic aerodynamic response and aeroelastic servo analysis.
For further understanding of the present invention, the frequency domain unsteady aerodynamic force calculation method of the present invention considering the aerodynamic surface curvature effect and the normal motion is described in detail below with reference to fig. 1 to 7.
As an embodiment of the present invention, as shown in fig. 1 to 7, a frequency domain unsteady aerodynamic force calculation method considering the camber effect and the normal motion of the present invention is described by taking a rectangular airfoil with a large aspect ratio as an example. The wing chord length is 60mm, and the span length is 480 mm. Because the calculation example is a high aspect ratio wing, a symmetrical wing profile is adopted, the influence of the camber of the wing profile is not considered, and the wing is deformed into a space curved surface under the action of load, as shown in fig. 5. The method application is only explained here, so the selection example is simpler, and the division of the pneumatic surface is rougher. The practical application is that the division and modeling of the pneumatic surface are carried out more carefully according to the requirements of the technical scheme. The specific analysis procedure is as follows.
Step one, performing pneumatic grid division on a deformed pneumatic surface of the aircraft.
And secondly, performing structural dynamics analysis on the aircraft to obtain the structural elastic mode of the aircraft.
And step three, extracting the structural elastic mode related to the deformed aerodynamic surface from the structural elastic modes of the aircraft and interpolating the structural elastic mode to the aerodynamic grid of the deformed aerodynamic surface.
And step four, arranging a spatial dipole basic solution on each grid of the deformed aerodynamic surface, wherein F1 and F3 are the intersection points of the aerodynamic grid ohm dipole lines and the aerodynamic grid. F2 is the point of action of the steady state pneumatic force, which is the midpoint of F1, F3, and H is the control point of the pneumatic grid. And solving a kernel function considering the aerodynamic surface deformation, and solving an aerodynamic influence coefficient matrix according to the kernel function.
And step five, calculating the local normal vector of the pneumatic grid of the deformed pneumatic surface.
And step six, multiplying the structural elastic mode of the deformed pneumatic surface with a local normal vector to obtain a normal mode of the deformed pneumatic surface, and solving a normal motion boundary condition according to the normal mode of the deformed pneumatic surface.
And step seven, solving the unsteady aerodynamic force on the aerodynamic surface grid after the deformation according to the normal motion boundary condition and the aerodynamic force influence coefficient matrix.
And step eight, multiplying the unsteady aerodynamic force on the deformed aerodynamic surface grid and the normal mode of the deformed aerodynamic surface to obtain the generalized curved surface unsteady aerodynamic force in the frequency domain range.
After the generalized curved surface unsteady aerodynamic force is acquired, flutter calculation can be performed by using the acquired unsteady aerodynamic force.
In summary, the invention provides an unsteady aerodynamic force calculation method considering the aerodynamic surface curve effect and normal motion, which not only accurately describes the deformed curved aerodynamic surface from the geometric modeling level, but also introduces the curve effect into the calculation of the aerodynamic influence coefficient matrix kernel function, and essentially considers the influence of the curve effect after the aerodynamic surface deformation. And moreover, the influence of the effective normal motion component of the curved surface aerodynamic surface on the unsteady aerodynamic force calculation is also considered, and the computation of the curved surface unsteady aerodynamic force is carried out starting from the accurate description of the boundary condition. Compared with the prior art, the unsteady aerodynamic force calculation method provided by the invention has the following advantages.
Firstly, the unsteady aerodynamic force calculation method provided by the invention can be used for dividing a three-dimensional aerodynamic surface grid in space, can accurately describe the geometric characteristics of bending and torsion of a lifting surface, and is suitable for aerodynamic force modeling calculation under various motion and deformation states of an aircraft.
Secondly, the unsteady aerodynamic force calculation method introduces the aerodynamic surface curve effect into the spatial arrangement of the dipole basic solution and the calculation of the kernel function, and fully reflects the curve effect in the unsteady aerodynamic force calculation.
Thirdly, the unsteady aerodynamic force calculation method introduces the local normal motion mode of the aerodynamic surface in the frequency domain aerodynamic force calculation, and accurately describes the effective normal motion form and normal boundary conditions causing the unsteady aerodynamic force.
Spatially relative terms, such as "above … …," "above … …," "above … …," "above," and the like, may be used herein for ease of description to describe one device or feature's spatial relationship to another device or feature as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if a device in the figures is turned over, devices described as "above" or "on" other devices or configurations would then be oriented "below" or "under" the other devices or configurations. Thus, the exemplary term "above … …" can include both an orientation of "above … …" and "below … …". The device may be otherwise variously oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.
It should be noted that the terms "first", "second", and the like are used to define the components, and are only used for convenience of distinguishing the corresponding components, and the terms have no special meanings unless otherwise stated, and therefore, the scope of the present invention should not be construed as being limited.
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 (5)

1. A unsteady aerodynamic force calculation method taking into account aerodynamic surface effects and normal motion, characterized by comprising:
meshing the deformed pneumatic surface of the aircraft;
performing structural dynamics analysis on the aircraft to obtain a structural elastic mode of the aircraft;
extracting a structural elastic mode related to the deformed aerodynamic surface from the structural elastic modes of the aircraft and interpolating the structural elastic mode to the aerodynamic grid of the deformed aerodynamic surface;
arranging a dipole basic solution on the grid of the deformed aerodynamic surface, solving a kernel function considering the deformation of the aerodynamic surface, and solving an aerodynamic influence coefficient matrix according to the kernel function; the kernel function taking into account the aerodynamic surface deformation is
Figure FDA0002693349990000011
λ1＝xi-xjWherein (x)i,yi,zi) Is the coordinates of the receiving point, (x)j,yj,zj) Is the coordinates of the disturbance point and is,
Figure FDA0002693349990000012
niis (x)i,yi,zi) In the normal direction of the airfoil, njIs (x)j,yj,zj) In the normal direction of the airfoil surface, omega is the structural vibration circular frequency, U∞For the far-coming velocity, R' is the distance between the receiving point and the disturbance point, a∞The speed of sound of far-front incoming flow, M∞The mach number of the incoming flow;
calculating the local normal vector of the pneumatic grid of the deformed pneumatic surface;
solving a normal mode of the deformed pneumatic surface according to the structural elastic mode of the deformed pneumatic surface and a local normal vector, wherein the normal mode of the deformed pneumatic surface is obtained by multiplying the structural elastic mode of the deformed pneumatic surface by the local normal vector; solving a normal motion boundary condition according to the normal mode of the deformed pneumatic surface;
according to the normal motion boundary condition and the aerodynamic force influence coefficient matrix, solving the unsteady aerodynamic force on the aerodynamic surface grid after deformation;
and acquiring generalized curved surface unsteady aerodynamic force according to the unsteady aerodynamic force on the deformed aerodynamic surface grid and the normal mode of the deformed aerodynamic surface, wherein the generalized curved surface unsteady aerodynamic force is acquired by multiplying the unsteady aerodynamic force on the deformed aerodynamic surface grid by the normal mode of the deformed aerodynamic surface.
2. The method of claim 1, wherein the boundary condition of the normal motion is that
Figure FDA0002693349990000021
Wherein w is the mesh dimensionless normal washing speed, k is the reduction frequency, b is the reference chord length, f is the normal mode of the deformed aerodynamic surface, n' is the curved surface normal,
Figure FDA0002693349990000022
is the real part of the signal,
Figure FDA0002693349990000023
is the imaginary part.
3. The method of claim 2, wherein the unsteady aerodynamic force Δ c on the aerodynamic surface mesh after deformation is calculated by taking into account the aerodynamic surface curvature effect and the normal motionpAccording to w ═ D Δ cpWhere w is the mesh dimensionless normal wash down velocity, D is the aerodynamic coefficient of influence matrix, Δ cpColumn vectors consisting of unsteady aerodynamic forces of the aerodynamic mesh.
4. A method of unsteady aerodynamic force calculation taking into account aerodynamic surface effects and normal motion as defined in claim 3, wherein said matrix of aerodynamic force influence coefficients D is based on
Figure FDA0002693349990000024
Is solved, wherein Δ xjIs the median cross-sectional length of the jth cell, ljIs the span length, χ, of the 1/4 chord point of the jth gridjChord line sweep angle of grid 1/4, KijIs a kernel function.
5. Method for unsteady aerodynamic force calculation taking into account the aerodynamic surface effect and the normal motion as claimed in any one of claims 1 to 4, characterized in that the chordwise mesh of the deformed aerodynamic surface is at least larger than 5, and the spanwise mesh is determined by the mesh cell slenderness ratio.
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