Unsteady aerodynamic characteristics of a fighter model undergoing large-amplitude pitching motions at high angles of attack

1990 ◽  
Author(s):  
JAY BRANDON ◽  
GAUTAM SHAH
Keyword(s):  
Large Amplitude ◽  
Aerodynamic Characteristics ◽  
Unsteady Aerodynamic ◽  
High Angles Of Attack

Modeling of unsteady aerodynamic characteristics at high angles of attack

2018 ◽  
Vol 233 (6) ◽  
pp. 2291-2301 ◽  
Author(s):  
Dong Hao ◽  
Lin Zhang ◽  
Jing Yu ◽  
Daiyong Mao
Keyword(s):  
State Space ◽  
Series Expansion ◽  
Angular Rate ◽  
Minimum Mean Square Error ◽  
Aerodynamic Characteristics ◽  
Unsteady Aerodynamic ◽  
Aerodynamic Model ◽  
Constant Pitch ◽  
High Angles Of Attack ◽  
Taylor’S Series

An improved model to express the unsteady aerodynamic characteristics at high angles of attack is presented in this paper. The proposed aerodynamic model is expressed on the basis of a progressive state-space representation and Taylor’s series expansion. The state-space expression is a first-order differential equation in which the power item of the angular rate of attack is introduced. The unsteady aerodynamic coefficients are described by Taylor’s series expansion in terms of input variables. The approach of minimum mean square error criterion is utilized to identify the unknown parameters of the proposed model by nonlinear least square method from the tunnel data. The given modeling method is experimentally demonstrated by the wind tunnel measurements of NACA 0015 airfoil with constant rate to high angles of attack, F18 aircraft with constant pitch rate ramp motion, and F18 HARV (high alpha research vehicle) configuration with large-amplitude harmonic oscillatory. The results show that it is possible to analyze more complex unsteady aerodynamic problems for an aircraft within the framework of the proposed aerodynamic model and the represented model is directly amenable to the simulation and control system design.

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

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Mi Baigang ◽  
Yu Jingyi
Keyword(s):  
Oscillation Amplitude ◽  
Angle Of Attack ◽  
Aerodynamic Characteristics ◽  
Higher Order ◽  
Initial Angle ◽  
Prediction Ability ◽  
Unsteady Aerodynamic ◽  
Reduced Frequency ◽  
High Angles Of Attack ◽  
Nonlinear Aerodynamic

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.

Effect of Shock Wave Behavior on Unsteady Aerodynamic Characteristics of Oscillating Transonic Compressor Cascade

2021 ◽  
Author(s):  
Jiuliang Gan ◽  
Toshinori Watanabe ◽  
Takehiro Himeno
Keyword(s):  
Shock Wave ◽  
Aerodynamic Force ◽  
Aerodynamic Characteristics ◽  
Fast Response ◽  
Influence Coefficient ◽  
Compressor Cascade ◽  
Blade Vibration ◽  
Unsteady Pressure ◽  
Transonic Compressor ◽  
Unsteady Aerodynamic

Abstract The unsteady behavior of the shock wave was studied in an oscillating transonic compressor cascade. The experimental measurement and corresponding numerical simulation were conducted on the cascade with different shock patterns based on influence coefficient method. The unsteady pressure distribution on blade surface was measured with fast-response pressure-sensitive paint (PSP) to capture the unsteady aerodynamic force as well as the shock wave movement. It was found that the movement of shock waves in the neighboring flow passages of the oscillating blade was almost anti-phase between the two shock patterns, namely, the double shocks pattern and the merged shock pattern. It was also found that the amplitude of the unsteady pressure caused by the passage shock wave was very large under the merged shock pattern compared with the double shocks pattern. The stability of blade vibration was also analyzed for both shock patterns including 3-D flow effect. These findings were thought to shed light on the fundamental understanding of the unsteady aerodynamic characteristics of oscillating cascade caused by the shock wave behavior.

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