A CFD-based method for simulating real-flight aerodynamic data of aircraft

Abstract

The present invention discloses a method for simulating aerodynamic data of an aircraft in real flight based on CFD, which belongs to the field of aircraft computational fluid dynamics simulation and comprises the following steps: step S1: determining the trajectory and attitude change of the aircraft in a ground inertial system based on data of the aircraft's real flight process; step S2: determining the input format of CFD software at different times according to the aircraft trajectory and displacement determined in step S1; step S3: using the CFD software to carry out simulation calculation of aerodynamic forces / torques; step S4: post-processing the calculation results, wherein the aerodynamic force coefficient and the torque coefficient take into account the changes in the altitude and speed of the aircraft during the flight process; in this scheme, factors such as the speed, attitude, and rudder deflection of the aircraft during the real flight process are taken into account, and the aerodynamic forces / torques obtained by numerical simulation are more accurate than those obtained by database interpolation, and have great application prospects in aircraft trajectory simulation and multi-body separation aerodynamic prediction.

Description

Technical Field

[0001] The present invention relates to the field of aircraft computational fluid dynamics simulation, and in particular to a CFD-based method for simulating real-flight aerodynamic data of an aircraft. Background Art

[0002] Computational fluid dynamics (CFD) technology for aircraft has been widely used in the aerospace field, playing an increasingly important role in aircraft development and finalization. For example, during the missile development process, CFD technology is used to generate an aerodynamic database, specifically the aerodynamic forces and moments of the missile under different altitudes, speeds, and flight attitudes, with different rudder deflections, to support missile flight control. On the one hand, with the development of CFD technology and the continuous expansion of computing resources, numerical calculations have become more efficient and convenient, leading to the continuous expansion and enrichment of the aerodynamic database. On the other hand, with the increasing performance of aircraft, the coupling of altitude, speed, flight attitude, rudder deflection angle, and flight angular velocity under real-world flight conditions has complicated the dynamic effects of aircraft, necessitating the use of CFD technology for simulation and evaluation. The method provided by the present invention uses CFD tools to simulate the trajectory and attitude changes of an aircraft during flight, obtaining the time-varying aerodynamic forces / moments during flight, which can be used to verify aerodynamic data of aircraft trajectory telemetry and evaluate performance. Summary of the Invention

[0003] The purpose of the present invention is to provide a CFD-based method for simulating real-flight aerodynamic data of an aircraft to address the above-mentioned shortcomings, thereby solving the problem that there is no efficient method in the prior art to simulate and evaluate aircraft under complex conditions.

[0004] The present invention is achieved through the following solutions:

[0005] A CFD-based method for simulating real-flight aerodynamic data of an aircraft comprises the following steps:

[0006] Step S1: Based on the data of the actual flight process of the aircraft, determine the trajectory and attitude changes of the aircraft in the ground inertial system;

[0007] Step S2: Determine the input format of the CFD software at different times based on the trajectory and displacement of the aircraft determined in step S1;

[0008] Step S3: Using CFD software to perform aerodynamic force / torque simulation calculations;

[0009] Step S4: Post-processing of the calculation results. The aerodynamic coefficients and moment coefficients take into account the changes in the altitude and speed of the aircraft during flight.

[0010] In step S1 , the data of the actual flight process of the aircraft specifically include the speed, angular velocity, rudder angle, angle of attack and sideslip angle data of the flight process.

[0011] In step S1, the trajectory and attitude change of the aircraft in the ground inertial system are determined, which specifically includes the following steps:

[0012] The velocity of the body coordinate system Oxyz during the known flight process of the aircraft and angular velocity , the angle of attack and sideslip angle of the aircraft during flight , calculate it as follows:

[0013] Step S11, select the initial moment velocity coordinate system Ox v y v z v As the ground coordinate system Ox0y0z0, the initial displacement of the aircraft in all directions is 0, and the speed is ;

[0014] Step S12, the angle of attack at the initial moment and sideslip angle Determine the initial attitude angle of the aircraft ;

[0015] Specifically, the coordinate transformation matrix from the ground coordinate system to the body coordinate system is

[0016] (1)

[0017] (2)

[0018] At the initial moment, the velocity coordinate system and the ground coordinate system are the same. At this time, the velocity components in the body coordinate system obtained by converting Equations (1) and (2) should be equal. Substituting the initial moment angle of attack and sideslip angle, the initial moment attitude angle can be obtained: ;

[0019] Step S13, determining the attitude angle of the aircraft at different times;

[0020] Specifically, after obtaining the initial attitude angle of the aircraft, the attitude angles at different times can be determined according to the kinematic equation of formula (3) based on the known angular velocity in the aircraft body coordinate system.

[0021] (3)

[0022] Where t represents time, dt represents the time derivative, w x 、w y and w zIndicates the angular velocity in the x, y, and z directions in the aircraft's body coordinate system.

[0023] Step S14, determining the motion trajectory of the aircraft at different times;

[0024] Specifically, according to the aircraft attitude angle at different times and the velocity component of the aircraft in the body coordinate system, the velocity component in the ground system can be determined according to the coordinate transformation relationship from the system to the ground system in formula (4), and then the aircraft displacement at different times can be determined according to formula (5);

[0025] (4)

[0026] (5).

[0027] Where t represents time, t n and t n-1 Indicates the time steps n and n-1 of differentiation; v x0 、v y0 、v z0 Indicates the speed in the x, y, and z directions in the ground coordinate system; x0, y0, and z0 are the three-directional positions in the ground coordinate system, and v0 is the speed in the ground coordinate system; v x 、v y 、v z are the three-direction velocities in the aircraft coordinate system.

[0028] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0029] 1. This scheme takes into account factors such as the speed, attitude, and rudder deflection of the aircraft during actual flight. The aerodynamic forces / torques obtained by numerical simulation are more accurate than those interpolated from the database.

[0030] 2. This scheme adopts unsteady calculation method, which can consider the dynamic effects of the aircraft flight process and evaluate the safety and effectiveness of the aircraft. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is an implementation flow chart of the present invention;

[0032] Figure 2 It is a coordinate system conversion relationship diagram in the present invention;

[0033] Figure 3 It is the trajectory change diagram of the aircraft relative to the incoming flow;

[0034] Figure 4 It is the attitude change diagram of the aircraft relative to the initial velocity system;

[0035] Figure 5 It is the axial force coefficient diagram of the aircraft. DETAILED DESCRIPTION

[0036] All features disclosed in this specification, or all steps in the disclosed methods or processes, except mutually exclusive features and / or steps, can be combined in any manner.

[0037] Any feature disclosed in this specification (including any appended claims and abstract), unless otherwise stated, may be replaced by other equivalent or similar features. In other words, unless otherwise stated, each feature is only an example of a series of equivalent or similar features.

[0038] In the description of the present invention, it should be understood that the terms "up", "down", "left", "right", etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a predetermined direction, be constructed and operated in a predetermined direction, and therefore cannot be understood as a limitation on the present invention.

[0039] Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be understood to indicate or imply relative importance or to implicitly indicate the quantity of the technical features being referred to. Thus, a feature defined as "first," "second," etc. may explicitly or implicitly include one or more of such features.

[0040] Example 1

[0041] The present invention provides a technical solution:

[0042] A CFD-based method for simulating real-flight aerodynamic data of an aircraft comprises the following steps:

[0043] Step S1: Based on the data of the actual flight process of the aircraft, determine the trajectory and attitude changes of the aircraft in the ground inertial system;

[0044] Step S2: Determine the input format of the CFD software at different times based on the trajectory and displacement of the aircraft determined in step S1;

[0045] Step S3: Using CFD software to perform aerodynamic force / torque simulation calculations;

[0046] Step S4: Post-processing of the calculation results. The aerodynamic coefficients and moment coefficients take into account the changes in the altitude and speed of the aircraft during flight.

[0047] In step S1 , the data of the actual flight process of the aircraft specifically includes the speed, angular velocity, rudder angle, angle of attack, and sideslip angle data of the flight process.

[0048] In step S1, the trajectory and attitude change of the aircraft in the ground inertial system are determined, which specifically includes the following steps:

[0049] The velocity of the body coordinate system Oxyz during the known flight process of the aircraft and angular velocity , the angle of attack and sideslip angle of the aircraft during flight , calculate it as follows:

[0050] Step S11, select the initial moment velocity coordinate system Ox v y v z v As the ground coordinate system Ox0y0z0, the initial displacement of the aircraft in all directions is 0, and the speed is ;

[0051] Step S12, the angle of attack at the initial moment and sideslip angle Determine the initial attitude angle of the aircraft ;

[0052] Specifically, the coordinate transformation matrix from the ground coordinate system to the body coordinate system is

[0053] (1)

[0054] (2)

[0055] At the initial moment, the velocity coordinate system and the ground coordinate system are the same. At this time, the velocity components in the body coordinate system obtained by converting Equations (1) and (2) should be equal. Substituting the initial moment angle of attack and sideslip angle, the initial moment attitude angle can be obtained: ;

[0056] Step S13: determining the aircraft attitude angles at different times when the aircraft attitude angle at the initial time is known.

[0057] Specifically, after obtaining the initial attitude angle of the aircraft, the attitude angles at different times can be determined according to the kinematic equation of formula (3) based on the known angular velocity in the aircraft body coordinate system.

[0058] (3)

[0059] Where t represents time, dt represents the time derivative, w x 、w y and w z Indicates the angular velocity in the x, y, and z directions in the aircraft's body coordinate system.

[0060] Step S14, determining the motion trajectory of the aircraft at different times;

[0061] Specifically, according to the aircraft attitude angle at different times and the velocity component of the aircraft in the body coordinate system, the velocity component in the ground system can be determined according to the coordinate transformation relationship from the system to the ground system in formula (4), and then the aircraft displacement at different times can be determined according to formula (5);

[0062] (4)

[0063] (5)

[0064] Where t represents time, t n and t n-1 Indicates the time steps n and n-1 of differentiation; v x0 、v y0 、v z0 Indicates the speed in the x, y, and z directions in the ground coordinate system; x0, y0, and z0 are the three-directional positions in the ground coordinate system, and v0 is the speed in the ground coordinate system; v x 、v y 、v z are the three-direction velocities in the aircraft coordinate system.

[0065] Example 2

[0066] Based on the above embodiment 1, the present invention provides a technical solution:

[0067] A CFD-based method for simulating real-flight aerodynamic data of an aircraft comprises the following steps:

[0068] Taking a certain period of telemetry data of a certain aircraft during its flight as input, the initial simulation time is set to 0, the angle of attack α, the sideslip angle β, the velocity and angular velocity changes of the body axis are given in Table 1.

[0069] According to step 1, the velocity coordinate system at the start of the simulation is the ground inertial system, that is, the calculation coordinate system, and the initial velocity of the aircraft is used as the incoming flow condition. Then the initial velocity of the aircraft relative to the incoming flow is 0, and the initial attitude is the angle of attack and sideslip angle of the body axis system relative to the velocity system, and the roll attitude angle is 0. At each subsequent moment, the aircraft generates a relative velocity relative to the fixed incoming flow velocity, and then the position changes, and the aircraft attitude also changes with the change of angular velocity. Using equations (1) to (5), the trajectory and attitude changes of the aircraft in the ground coordinate system Ox0y0z0 are as follows: Figure 3 and Figure 4 shown.

[0070] Table 1 Telemetry data of a certain period of aircraft flight process

[0071]

[0072] According to step 2, determine the input of the CFD software. This embodiment takes a third-party software that can solve the aerodynamic characteristics of the aircraft and the multi-body separation characteristics as an example, and the input content is shown in the following table:

[0073] Table 2 CFD software simulation input

[0074]

[0075] According to step 3, CFD calculations are carried out. For comparison, the unsteady dynamic calculation uses the inputs in Table 2. The steady calculation selects the times t=0, 0.08, 0.16, 0.24, 0.32, and 0.4s, and adopts the general calculation method for given angle of attack and sideslip angle.

[0076] According to step 4, the calculation results are post-processed, and the aerodynamic force / torque coefficient needs to be calculated based on the real-time speed change. Figure 5 The axial force coefficients obtained from dynamic and steady calculations are shown, and the results are consistent, proving the effectiveness of this method.

[0077] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A CFD-based method for simulating real-flight aerodynamic data of an aircraft, characterized by: The following steps are involved: Step S1: Based on the data of the actual flight process of the aircraft, determine the trajectory and attitude changes of the aircraft in the ground inertial system; In step S1, the trajectory and attitude change of the aircraft in the ground inertial system are determined, which specifically includes the following steps: Step S11, select the initial moment velocity coordinate system Ox v y v z v As the ground coordinate system Ox0y0z0, the initial displacement of the aircraft in all directions is 0, and the speed is ; The velocity in the body coordinate system Oxyz of the known aircraft flight process and angular velocity , the angle of attack and sideslip angle of the aircraft during flight Calculation is performed under the condition of Step S12, the angle of attack at the initial moment and sideslip angle Determine the initial attitude angle of the aircraft ; Coordinate transformation matrix from ground coordinate system to body coordinate system At the initial moment, the velocity coordinate system and the ground coordinate system are the same. The velocity components in the body coordinate system should be equal through the formula conversion. Substituting the initial moment angle of attack and sideslip angle, the initial moment attitude angle can be obtained. ; The specific formula used for formula conversion is: and ； Step S13, determining the aircraft attitude angle at different times; after obtaining the aircraft attitude angle at the initial time, the attitude angle at different times can be determined based on the known angular velocity in the aircraft body coordinate system and the kinematic equation; the kinematic equation is specifically: ； Where t represents time, dt represents the time derivative, w x 、w y and w z Indicates the angular velocity in the x, y, and z directions in the aircraft body coordinate system; Step S14, determining the motion trajectory of the aircraft at different times; According to the aircraft attitude angle at different times and the velocity component of the aircraft in the body coordinate system, the velocity component in the ground system is determined according to the coordinate transformation relationship from the system to the ground system, and then the aircraft displacement at different times is determined; the coordinate transformation relationship from the system to the ground system is: and through Determine the displacement of the aircraft at different times; where t represents time, t n and t n-1 Indicates the time steps n and n-1 of differentiation; v x0 、v y0 、v z0 Indicates the speed in the x, y, and z directions in the ground coordinate system; x0, y0, and z0 are the three-directional positions in the ground coordinate system, and v0 is the speed in the ground coordinate system; v x 、v y 、v z is the three-direction velocity in the aircraft coordinate system; Step S2: Determine the input format of the CFD software at different times based on the trajectory and displacement of the aircraft determined in step S1; Step S3: Using CFD software to perform aerodynamic force / torque simulation calculations; Step S4: Post-processing of the calculation results. The aerodynamic coefficients and moment coefficients take into account the changes in the altitude and speed of the aircraft during flight.

2. The CFD-based method for simulating real-flight aerodynamic data of an aircraft according to claim 1, characterized in that: In step S1 , the data of the actual flight process of the aircraft specifically include the speed, angular velocity, rudder angle, angle of attack and sideslip angle data of the flight process.

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