Aircraft real flight aerodynamic data simulation method based on CFD

Abstract

The invention discloses an aircraft real flight aerodynamic data simulation method based on CFD, and belongs to the field of aircraft computational fluid mechanics simulation, and the method comprises the following steps: S1, determining the track and attitude change of an aircraft under a ground inertial system according to the data of the real flight process of the aircraft; s2, determining input formats of CFD software at different moments according to the aircraft trajectory and displacement determined in the step S1; s3, carrying out aerodynamic force / torque simulation calculation by using CFD software; s4, post-processing a calculation result, wherein the aerodynamic coefficient and the torque coefficient consider the changes of the height and the speed in the flight process of the aircraft; according to the scheme, factors such as the speed, the posture and the rudder deflection in the real flight process of the aircraft are considered, the aerodynamic force / torque obtained through numerical simulation is more accurate than database interpolation, and the method has a large application prospect in aircraft trajectory simulation and multi-body separation aerodynamic prediction.

Description

Technical Field

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

[0002] The computational fluid dynamics (CFD) technology of aircraft has been widely applied in the field of aerospace and has played an increasingly important role in the development and finalization of aircraft. Taking missiles as an example, the CFD technology is used to obtain an aerodynamic database during the development process, that is, the aerodynamic forces and moments of the missile under different rudder deflections at different altitudes, speeds, and flight attitudes, providing support for missile flight control. On the one hand, with the development of CFD technology and the continuous expansion of computing resources, the acquisition of numerical calculations has become more efficient and convenient, making the aerodynamic database increasingly expanded and enriched; on the other hand, with the increasingly powerful performance of aircraft, the coupling of altitude, speed, flight attitude, rudder deflection angle, and flight angular velocity under real flight conditions has made the dynamic effects of aircraft complex, and it is necessary to use CFD technology for simulation and evaluation. The method provided by the present invention uses a CFD tool to simulate the trajectory and attitude changes during the flight process of an aircraft, and obtains the aerodynamic forces / moments changing with time during the flight process, which can be used for the verification of aerodynamic data in ballistic telemetry of aircraft and performance evaluation. Summary of the Invention

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

[0004] The present invention is realized by the following solution: A method for simulating real flight aerodynamic data of an aircraft based on CFD includes the following steps: Step S1: Determine the trajectory and attitude changes of the aircraft in the ground inertial system according to the data of the real flight process of the aircraft; Step S2: Determine the input format of the CFD software at different times according to the trajectory and displacement of the aircraft determined in Step S1; Step S3: Use the CFD software to carry out simulation calculations of aerodynamic forces / moments; Step S4: Post-process the calculation results, and consider the changes in altitude and speed during the flight process of the aircraft for the aerodynamic coefficient and moment coefficient.

[0005] In Step S1, the data of the real flight process of the aircraft specifically includes the data of speed, angular velocity, rudder deflection angle, angle of attack, and sideslip angle during the flight process.

[0006] In step S1, the trajectory and attitude change of the aircraft in the ground inertial system are determined, which specifically includes the following steps: The velocity in the body coordinate system Oxyz of the known aircraft during its flight and angular velocity , the angle of attack and sideslip angle of the aircraft during flight , calculate it as follows: 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 ; Step S12, based on the angle of attack at the initial moment and sideslip angle Determine the initial attitude angle of the aircraft ; Specifically, the coordinate transformation matrix from the ground coordinate system to the body coordinate system is

[0007] (1) (2) 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: ; Step S13, determining the attitude angle of the aircraft at different times; Specifically, after obtaining the attitude angle of the aircraft at the initial moment, the attitude angle at different moments can be determined according to the kinematic equation of formula (3) based on the known angular velocity in the aircraft body coordinate system.

[0008] (3) Where t represents time, dt represents the derivative with respect to time, and w x 、w y and w z It represents the angular velocity in the x, y, and z directions in the aircraft body coordinate system.

[0009] Step S14, determining the motion trajectory of the aircraft at different times; Specifically, according to the attitude angle of the aircraft 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 equation (4), and then the displacement of the aircraft at different times can be determined according to equation (5); (4) (5).

[0010] Where t represents time, t n and t n-1 represent the nth and (n - 1)th time steps of differentiation; v x0 , v y0 , v z0 represent the velocities in the x, y, and z directions in the ground coordinate system; x0, y0, z0 are the positions in the three directions in the ground coordinate system, and v0 is the velocity in the ground coordinate system; v x , v y , v z are the velocities in the three directions in the aircraft coordinate system.

[0011] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are as follows: 1. In this solution, factors such as the velocity, attitude, and rudder deflection of the aircraft during the actual flight process are considered, and the aerodynamic force / moment obtained by numerical simulation is more accurate than the database interpolation.

[0012] 2. This solution adopts an unsteady calculation method, which can consider the dynamic effects during the flight process of the aircraft and evaluate the safety and effectiveness of the aircraft. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is the implementation flowchart of the present invention; Figure 2 is the coordinate system conversion relationship diagram of the present invention; Figure 3 is the trajectory change diagram of the aircraft relative to the oncoming flow; Figure 4 is the attitude change diagram of the aircraft relative to the initial velocity system; Figure 5 is the axial force coefficient diagram of the aircraft. DETAILED DESCRIPTION OF THE INVENTION

[0014] All features disclosed in this specification, or all steps in the disclosed methods or processes, except for mutually exclusive features and / or steps, can be combined in any way.

[0015] Any feature disclosed in this specification (including any additional claims, abstract) can be replaced by other equivalent or similar-purpose alternative features unless specifically stated. That is, unless specifically stated, each feature is only an example of a series of equivalent or similar features.

[0016] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by terms such as "upper", "lower", "left", "right", etc. is based on the orientation or positional relationship shown in the drawings, and is 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 orientation, be constructed and operated in a predetermined orientation, and therefore should not be construed as a limitation to the present invention.

[0017] In addition, terms such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features.

[0018] Embodiment 1 The present invention provides a technical solution: A method for simulating actual flight aerodynamic data of an aircraft based on CFD, comprising the following steps: Step S1: For the data of the actual flight process of the aircraft, determine the trajectory and attitude changes of the aircraft in the ground inertial system; Step S2: Determine the input format of the CFD software at different moments according to the aircraft trajectory and displacement determined in step S1; Step S3: Use the CFD software to carry out simulation calculations of aerodynamic forces / moments; Step S4: Post-processing of the calculation results, and the aerodynamic coefficients and moment coefficients take into account the changes in altitude and speed during the flight process of the aircraft.

[0019] In step S1, the data of the actual flight process of the aircraft specifically includes the speed, angular velocity, rudder deflection angle, angle of attack, and sideslip angle data during the flight process.

[0020] In step S1, to determine the trajectory and attitude changes of the aircraft in the ground inertial system, the following steps are specifically included: Given the velocity and angular velocity in the body coordinate system Oxyz of the aircraft during the flight process, and the angle of attack and sideslip angle during the flight process of the aircraft, the calculations are carried out according to the following steps: v y v z v Select the velocity coordinate system Ox at the initial moment as the ground coordinate system Ox0y0z0, the displacements of the aircraft in all directions at the initial moment are 0, and the velocity is ; Step S12, determine the attitude angle of the aircraft at the initial moment from the angle of attack and sideslip angle Specifically, through the coordinate transformation matrix from the ground coordinate system to the body coordinate system

[0021] (1) (2) At the initial moment, the velocity coordinate system is the same as the ground coordinate system. At this time, the velocity components in the body coordinate system obtained by transforming from equations (1) and (2) should be equal. Substituting the angle of attack and sideslip angle at the initial moment, the attitude angle at the initial moment can be obtained ; Step S13, determine the attitude angle of the aircraft at different moments given the attitude angle of the aircraft at the initial moment

[0022] Specifically, after obtaining the attitude angle of the aircraft at the initial moment, based on the known angular velocity in the body coordinate system of the aircraft, according to the kinematic equation of equation (3), the attitude angle at different moments can be determined

[0023] (3) where t represents time, dt represents the derivative with respect to time, w x 、w y and w z represent the angular velocities in the x, y, and z directions in the body coordinate system of the aircraft

[0024] Step S14, determine the flight trajectory of the aircraft at different moments Specifically, according to the attitude angle of the aircraft at different moments and the velocity components of the aircraft in the body coordinate system, based on the coordinate transformation relationship from the body system to the ground system of equation (4), the velocity components in the ground system can be determined, and then the displacement of the aircraft at different moments can be determined according to equation (5) (4) (5) where t represents time, t n and t n-1 represent the nth and (n - 1)th steps of the differential time step; v x0 、v y0 、v z0 represent the velocities in the x, y, and z directions in the ground coordinate system; x0, y0, z0 are the positions in the three directions in the ground coordinate system, v0 is the velocity in the ground coordinate system; v x 、v y 、v z are the velocities in the three directions in the aircraft coordinate system

[0025] Embodiment 2 Based on the above Embodiment 1, the present invention provides a technical solution A method for simulating real flight aerodynamic data of an aircraft based on CFD, comprising the following steps: Taking a certain section of telemetry data during the flight of a certain aircraft as input, setting the simulation initial time to 0, the angle of attack α, the sideslip angle β, and the changes in velocity and angular velocity in the body axis system are given in Table 1. According to Step 1, taking the velocity coordinate system at the simulation start time as the ground inertial system, that is, the calculation coordinate system, taking the initial velocity of the aircraft as the oncoming flow condition, then the initial velocity of the aircraft relative to the oncoming 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 oncoming flow velocity, and thus undergoes a position change, and the aircraft attitude also changes with the change in angular velocity. Using Equations (1)-(5), the trajectory and attitude changes of the aircraft in the ground coordinate system Ox0y0z0 are as Figure 3 and Figure 4 shown.

[0026] Table 1 A certain section of telemetry data during the flight of the aircraft

[0027] According to Step 2, determine the input of the CFD software. In this embodiment, taking a third-party software that can solve the aerodynamic characteristics and multi-body separation characteristics of the aircraft as an example, the input content is shown in the following table: Table 2 CFD software simulation input

[0028] According to Step 3, conduct CFD calculations. For comparison, the unsteady dynamic calculation uses the input in Table 2, and the steady calculation selects the moments t = 0, 0.08, 0.16, 0.24, 0.32, 0.4 s, and adopts the general calculation method of given angle of attack and sideslip angle.

[0029] According to Step 4, post-process the calculation results. The aerodynamic force / moment coefficient needs to be calculated according to the real-time velocity change. Figure 5 Shows the axial force coefficients obtained from the dynamic and steady calculations, and the results are in agreement, proving the effectiveness of this method.

[0030] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A CFD-based method for simulating actual flight aerodynamic data of an aircraft, characterized in that: It includes the following steps: Step S1: For the data of the actual flight process of the aircraft, determine the trajectory and attitude changes of the aircraft in the ground inertial system; Step S2: According to the aircraft trajectory and displacement determined in Step S1, determine the input format of the CFD software at different times; Step S3: Use the CFD software to carry out simulation calculations of aerodynamic forces / moments; Step S4: Post-process the calculation results, and consider the changes in altitude and speed during the flight process of the aircraft for the aerodynamic coefficient and moment coefficient.

2. The method for simulating actual flight aerodynamic data of an aircraft based on CFD according to claim 1, wherein: In Step S1, the data of the actual flight process of the aircraft specifically includes the speed, angular velocity, rudder deflection angle, angle of attack, and sideslip angle data during the flight process.

3. A CFD-based method for simulating actual flight aerodynamic data of an aircraft according to claim 1 or 2, characterized in that: In Step S1, to determine the trajectory and attitude changes of the aircraft in the ground inertial system, it specifically includes the following steps: Step S11, select the velocity coordinate system Ox at the initial moment v y v z v as the ground coordinate system Ox0y0z0. The displacements of the aircraft in all directions at the initial moment are 0, and the velocity is ; Step S12, determine the attitude angle of the aircraft at the initial moment from the angle of attack and sideslip angle at the initial moment of the aircraft; ; Step S13: Determine the attitude angles of the aircraft at different times; Step S14: Determine the motion trajectory of the aircraft at different times.

4. The method for simulating real flight aerodynamic data of an aircraft based on CFD according to claim 3, characterized in that: Velocity in the body coordinate system Oxyz during the known flight process of the aircraft and angular velocity , under the conditions of the angle of attack and sideslip angle during the flight process of the aircraft for calculation.

5. The method for simulating actual flight aerodynamic data of an aircraft based on CFD according to claim 4, characterized in that: Step S12 is specifically as follows. Through the coordinate transformation matrix from the ground coordinate system to the body coordinate system , at the initial moment, the velocity coordinate system is the same as the ground coordinate system. By formula conversion, it can be obtained that the velocity components in the body coordinate system should be equal. Substituting the angle of attack and sideslip angle at the initial moment, the attitude angle at the initial moment can be obtained .

6. The method for simulating actual flight aerodynamic data of an aircraft based on CFD according to claim 5, wherein: In Step S12, the specific formulas used for formula conversion are: and 。 7. The method for simulating real flight aerodynamic data of an aircraft based on CFD according to claim 6, wherein: In Step S13, specifically, after obtaining the attitude angles of the aircraft at the initial moment, based on the known angular velocity in the body coordinate system of the aircraft and according to the kinematic equation, the attitude angles at different times can be determined.

8. The method for simulating real flight aerodynamic data of an aircraft based on CFD according to claim 7, wherein: In Step S13, the specific kinematic equation is: ； where \(t\) represents time, \(dt\) represents the derivative with respect to time, \(w\) x , \(w\) y and \(w\) z represent the angular velocities in the \(x\), \(y\), and \(z\) directions in the body coordinate system of the aircraft.

9. The method for simulating actual flight aerodynamic data of an aircraft based on CFD according to claim 8, wherein: In Step S14, specifically: According to the attitude angles of the aircraft at different times and the velocity components of the aircraft in the body coordinate system, determine the velocity components in the ground coordinate system according to the coordinate transformation relationship from the body coordinate system to the ground coordinate system, and then determine the displacements of the aircraft at different times.

10. A CFD-based method for simulating actual flight aerodynamic data of an aircraft, characterized in that: In Step S14, specifically: The coordinate transformation relationship from the body coordinate system to the ground coordinate system is: and through Determine the displacement of the aircraft at different times; where t represents time, t n and t n-1 represent the differential time steps at the nth and (n - 1)th steps; v x0 、v y0 、v z0 represent the velocities in the x, y, and z directions in the ground coordinate system; x0, y0, and z0 are the positions in the three directions in the ground coordinate system, and v0 is the velocity in the ground coordinate system; v x 、v y 、v z are the velocities in the three directions in the aircraft coordinate system.

Images