A method for analyzing follow-up aerodynamic loads in finite element analysis of the entire aircraft

Abstract

The present application relates to the field of whole-aircraft finite element analysis, and is a method for analyzing the dynamic aerodynamic load in the whole-aircraft finite element analysis. The method first obtains the aerodynamic load coefficient at each simulation time, and then respectively calculates the whole-aircraft inertial load component corresponding to the aerodynamic load and the whole-aircraft inertial load component corresponding to the whole-aircraft external load, and then writes a load model file and a load card load master control file integrating all loads. By using the correspondence between the whole-aircraft load coefficient, the aerodynamic load coefficient and the ground load coefficient, the aerodynamic load of the dynamic distribution during the landing / carrier landing of the aircraft can be accurately included by simply modifying the load coefficient of the aerodynamic load. The method is simple and practical.

Description

Technical Field

[0001] The present application belongs to the field of whole-aircraft finite element analysis, and in particular relates to a method for analyzing follow-up aerodynamic loads in whole-aircraft finite element analysis. Background Art

[0002] When simulating and analyzing aircraft takeoff, taxiing, and landing, the total aerodynamic load of the entire aircraft, which changes with time, is often calculated through parameters such as aircraft speed and angle of attack, and is used as an input condition for simulation analysis of the entire aircraft. However, this has multiplied the workload of the subsequent calculation of the entire aircraft's distributed aerodynamic load, the entire aircraft's distributed inertial load, and the entire aircraft's finite element node load, and has increased the size of the load file of the entire aircraft's finite element analysis model, which is unacceptable to downstream designers of the two professions of load calculation and finite element analysis. Moreover, it is too time-consuming and laborious to implement. For the sake of simplicity in calculation, sometimes a fixed value is taken for the aerodynamic load of the whole aircraft or the aerodynamic load is ignored in the finite element analysis of the aircraft takeoff, taxiing and landing simulation conditions. The resulting imbalance of the whole aircraft is then balanced by the inertial load of the whole aircraft. However, this simplified approach cannot take into account the impact of the aerodynamic load of the whole aircraft on the aircraft that changes at any time, and blurs the interface between the aerodynamic load and the inertial load. Moreover, due to the different distribution forms of the aerodynamic load and the inertial load of the whole aircraft, the net load of the aircraft after the superposition of the aerodynamic load, landing gear load and inertial load is distorted, which affects the finite element analysis results of the whole aircraft.

[0003] Therefore, how to analyze the dynamic and changing aerodynamic loads of the entire aircraft more simply and effectively is a problem that needs to be solved. Summary of the invention

[0004] The purpose of this application is to provide a method for analyzing follow-up aerodynamic loads in the finite element analysis of the whole aircraft, so as to solve the problem that the calculation amount of the aerodynamic load of the whole aircraft is large or the use of fixed-value aerodynamic loads leads to distortion of the net load of the aircraft.

[0005] The technical solution of the present application is: a method for analyzing follow-up aerodynamic loads in finite element analysis of the whole aircraft, including selecting a standard aerodynamic load condition, calculating the standard aerodynamic load condition and the aerodynamic load coefficient at each simulation time; calculating the inertial load of the whole aircraft balanced with the standard aerodynamic load condition; calculating the total load of other external loads of the aircraft; calculating the inertial load of the whole aircraft that balances the external loads of the whole aircraft except the aerodynamic load; compiling all load model files acting on the aircraft in the load model file used in the finite element analysis of the whole aircraft; compiling a load card load master control file that integrates all loads; and solving the finite element model taking into account the follow-up load.

[0006] Preferably, the method for writing the load is to introduce the load condition number of the entire aircraft, write a master control file of the load condition of the entire aircraft, and use the load card to correlate and integrate all the loads acting on the aircraft.

[0007] Preferably, the finite element model is solved using Nastran.

[0008] Preferably, the load model file includes aerodynamic load and inertial load files of standard aerodynamic load conditions, and load files of other external loads acting on the aircraft except the aerodynamic load.

[0009] Preferably, the aerodynamic load condition number is used to calculate the aerodynamic load coefficient and the inertial load of the whole aircraft balanced with the standard aerodynamic load condition, the ground load condition number is used to calculate the total load and the inertial load of the whole aircraft that balances the external load of the whole aircraft except the aerodynamic load, and the whole aircraft load condition number is used when compiling the whole aircraft model file.

[0010] The present application discloses a method for analyzing the dynamic aerodynamic load in the finite element analysis of the whole aircraft. The method first obtains the aerodynamic load coefficient at each simulation time, and then respectively calculates the whole aircraft inertial load component corresponding to the aerodynamic load and the whole aircraft inertial load component corresponding to the whole aircraft external load. Then, a load model file and a load card load master control file integrating all loads are compiled. By utilizing the correspondence between the whole aircraft load coefficient, the aerodynamic load coefficient and the ground load coefficient, the aerodynamic load of the dynamic distribution during the landing / carrier landing of the aircraft can be accurately included by simply modifying the load coefficient of the aerodynamic load. The method is simple and practical. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In order to more clearly illustrate the technical solution provided by the present application, the following is a brief introduction to the accompanying drawings. Obviously, the accompanying drawings described below are only some embodiments of the present application.

[0012] Figure 1 The force model of the aircraft combined with the landing / carrier force of the aircraft in this application;

[0013] Figure 2 The aircraft force model for the force decomposition of the aircraft landing / carrier landing in this application;

[0014] Figure 3 For this application, the LOAD card is used to calculate the aerodynamic load principle diagram of the whole aircraft during landing / carrier follow-up;

[0015] Figure 4 This is a schematic diagram of the overall process of this application. DETAILED DESCRIPTION

[0016] In order to make the purpose, technical solutions and advantages of the implementation of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below in conjunction with the drawings in the embodiments of this application.

[0017] A method for analyzing the dynamic aerodynamic load in the finite element analysis of the whole aircraft is disclosed. The aerodynamic load of the whole aircraft is analyzed by aerodynamics, and it can be known that the aerodynamic load of the aircraft mainly changes with the angle of attack and the speed when the aircraft lands / landing, while the distribution form of the aerodynamic load of each component does not change much. The distribution feature of the aerodynamic load of the whole aircraft that the distribution form of the aerodynamic load of each component does not change much determines that the dynamic total aerodynamic load and the distributed load of the whole aircraft at each moment can be determined using a load coefficient, and the load coefficient is equal to the ratio of the maximum aerodynamic load of the whole aircraft during landing / landing to the aerodynamic load of the whole aircraft at each moment.

[0018] Combining the knowledge of the synthesis and decomposition of theoretical mechanics forces, we can know that Figure 1 The force model of the aircraft landing / carrier landing can be decomposed into Figure 2 The force model of the aircraft landing / carrier landing shown is equivalent. Figure 2 Landing gear load case numbers were introduced.

[0019] According to the load card usage rules agreed by Nastran for solving finite element models, Figure 2 All relevant loads on the aircraft involved in the decomposed aircraft force model can be obtained through Figure 3 The method shown is unified again. Figure 3 When calling the LOAD card shown, you only need to modify the load coefficient of the aerodynamic load to accurately account for the aerodynamic load distributed during aircraft landing / carrier landing. Figure 3 The full aircraft load case number was introduced.

[0020] The specific steps include:

[0021] Step S100, selecting the aerodynamic load at the maximum aerodynamic load moment among all the moments of the simulation analysis as the standard aerodynamic load condition, introducing the aerodynamic load condition number, and calculating the aerodynamic load coefficients of the standard aerodynamic load condition and each simulation moment;

[0022] Step S200, introducing the aerodynamic load condition number, calculating the whole machine inertial load balanced with the standard aerodynamic load condition, that is, obtaining the inertial load component corresponding to the aerodynamic load;

[0023] Step S300, introduce the ground load condition number, calculate the total load of other external loads acting on the aircraft except the aerodynamic load, including the ground support and reaction load on the landing gear, engine thrust (pull) force, arresting (ejection) load, etc., and obtain the load components of other loads except the aerodynamic load.

[0024] Step S400, introducing the ground load condition number, and calculating the inertial load of the whole aircraft to balance the external load of the whole aircraft except the aerodynamic load;

[0025] Step S500, introducing the whole aircraft load condition number, and compiling all load model files acting on the aircraft in the load model file used for the whole aircraft finite element analysis;

[0026] Step S600, compile a load card load master control file that integrates all loads;

[0027] The writing method of load is:

[0028] Introduce the load condition number of the entire aircraft, compile the overall control file of the load condition of the entire aircraft, and use the load card to correlate and integrate all the loads acting on the aircraft in steps S100-S400.

[0029] Step S700, solving the finite element model taking into account the follower load, the finite element model is solved using Nastran, the calculation is convenient and accurate.

[0030] By taking into account the inertial load of the entire aircraft, using the correspondence between the aircraft load coefficient, ground load coefficient and aerodynamic load coefficient in the load card, and combining the corresponding situation numbers, first obtain the inertial load component corresponding to the aerodynamic load coefficient, and then obtain the inertial load component of the entire aircraft corresponding to other external loads. In this way, according to the corresponding relationship in the written load card, the load coefficient of the aerodynamic load can be modified to accurately obtain the aerodynamic load with dynamic distribution when the aircraft lands / landing.

[0031] By combining the calculation of aircraft aerodynamic loads with the finite element model used in strength analysis during calculation, the boundaries between disciplines have been broken. This method is scientifically proposed after analyzing the changing law of the dynamic aerodynamic load. This simple method satisfactorily solves the problems caused by the dynamic distributed aerodynamic load during the simulation analysis of aircraft takeoff, taxiing and landing without increasing the calculation workload of the distributed aerodynamic load of the whole aircraft and the finite element node load of the whole aircraft, and without increasing the load file size of the finite element model of the whole aircraft, making the analyzed load model closer to the actual situation, and the method is simple, operational and practical.

[0032] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A method for analyzing follow-up aerodynamic loads in finite element analysis of a whole aircraft, characterized by: include The aerodynamic load at the maximum moment of the aerodynamic load in all the moments of the simulation analysis is selected as the standard aerodynamic load condition, the aerodynamic load condition number is introduced, and the aerodynamic load coefficient of the standard aerodynamic load condition and each simulation moment is calculated; Introduce the aerodynamic load condition number and calculate the inertial load of the whole aircraft that is balanced with the standard aerodynamic load condition; calculate the total load of other external loads of the aircraft; Introduce the ground load condition number, calculate the total load of other external loads acting on the aircraft except the aerodynamic load, including the ground support and reaction load on the landing gear, engine thrust, and arresting load, and obtain the load components of other loads except the aerodynamic load; Introduce the ground load condition number and calculate the inertial load of the whole aircraft to balance the external load of the whole aircraft except the aerodynamic load; Introduce the load condition number of the whole aircraft and compile all the load model files acting on the aircraft in the load model file used in the finite element analysis of the whole aircraft; Write a load card load master control file that integrates all loads; the load writing method is: Introduce the load condition number of the whole aircraft, compile the overall control file of the load condition of the whole aircraft, and use the load card to correlate and integrate all the loads acting on the aircraft; A finite element model taking into account the follower load is solved, wherein the finite element model is solved using Nastran; the load model file includes aerodynamic load and inertial load files of standard aerodynamic load conditions, and load files of other external loads acting on the aircraft except the aerodynamic load.

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