An Improved Nonlinear Aerodynamic Derivative Model of Aircraft at High Angles of Attack

Mi Baigang,Yu Jingyi,Jinyang Xu

doi:10.1155/2021/5815167

Abstract

The classical aerodynamic derivative model is widely used in flight dynamics, but its application is extremely limited in cases with complicated nonlinear flows, especially at high angles of attack. A modified nonlinear aerodynamic derivative model for predicting unsteady aerodynamic forces and moments at a high angle of attack is developed in this study. We first extend the higher-order terms to describe the nonlinear characteristics and then introduce three more influence parameters, the initial angle of attack, the reduced frequency, and the oscillation amplitude, to correct the constant aerodynamic derivative terms that have higher-order polynomials for these values. The improved nonlinear aerodynamic derivative model was validated by using the NACA 0015 airfoil and the F-18 model. The results show that the improved model has a higher prediction ability at high angles of attack and has the ability to predict the aerodynamic characteristics of other unknown states based on known unsteady aerodynamic data, such as the initial angle of attack, reduced frequency, and oscillation amplitude.

Highlights

The unsteady aerodynamic characteristic requirements at high angles of attack for the generation aircraft are increasing quickly, and the complicated unsteady aerodynamics caused by dynamic motion at high angles of attack has become one of the current research hotspots [1, 2]
More attention has been given on how to obtain acceptable aerodynamic data through limited calculations or tests and establish a relatively accurate mathematical model to predict the aerodynamic characteristics of the dynamic motion at high angles of attack, that is, unsteady aerodynamic modeling [7, 8]
To improve the nonlinear aerodynamic modeling ability at a high angle of attack, this study developed an extended nonlinear aerodynamic derivative model by expanding the higher-order terms and adding three more motion parameters to correct the constant expression of the coefficient terms in the classical model

Summary

Introduction

The unsteady aerodynamic characteristic requirements at high angles of attack for the generation aircraft are increasing quickly, and the complicated unsteady aerodynamics caused by dynamic motion at high angles of attack has become one of the current research hotspots [1, 2]. International Journal of Aerospace Engineering they are still a focus due to their good applicability to both 2-D and 3-D configurations and subsonic and supersonic cases Both conventional and modern intelligent methods are undergoing constant development and improvement. The aerodynamic derivative model is based on a linear system, so the aerodynamic expression of unsteady dynamic motion at low angles of attack is more accurate, and it is not suitable for nonlinear situations with high angles of attack [10]. This model is still worth attention because of its simple form and easy coupling with flight quality analysis. The improved model is verified and analyzed by using the dynamic motion of the NACA 0015 airfoil in different cases

Classical Aerodynamic Derivative Model

Classical Aerodynamic Derivative Model Validation

Nonlinear Correction 1

Validation Analysis of Improved Model

Conclusions

Conflicts of Interest