Title page for ETD etd-110498-091714


Type of Document Master's Thesis
Author Stagg, Gregory A.
URN etd-110498-091714
Title An Aerodynamic Model for Use in the High Angle of Attack Regime
Degree Master of Science
Department Aerospace and Ocean Engineering
Advisory Committee
Advisor Name Title
Lutze, Frederick H. Jr. Committee Chair
Anderson, Mark R. Committee Member
Durham, Wayne C. Committee Member
Keywords
  • Pitching Moment
  • Normal Force
  • Rolling Moment
  • Aerodynamic Modeling
  • High Angle of Attack
Date of Defense 1998-12-02
Availability unrestricted
Abstract
Harmonic oscillatory tests for a fighter aircraft using the

Dynamic Plunge--Pitch--Roll model mount at Virginia Tech Stability

Wind Tunnel are described. Corresponding data reduction methods are

developed on the basis of multirate digital signal processing. Since

the model is sting mounted, the frequencies associated with sting

vibration are included in balance readings thus a linear filter must

be used to extract out the aerodynamic responses. To achieve this, a

Finite Impulse Response (FIR) is designed using the Remez exchange

algorithm.

Based on the reduced data, a state--space model is developed to

describe the unsteady aerodynamic characteristics of the aircraft

during roll oscillations. For this model, we chose to separate the aircraft

into panels and model the local forces and moments. Included in this

technique is the introduction of a new state variable, a separation

state variable which characterizes the separation for each panel.

This new variable is governed by a first order differential equation.

Taylor series expansions in terms of the input variables were performed

to obtain the aerodynamic coefficients of the model. These

derivatives, a form of the stability derivative approach, are not

constant but rather quadratic functions of the new state variable.

Finally, the concept of the model was expanded to allow for the

addition of longitudinal motions. Thus, pitching moments will be

identified at the same time as rolling moments. The results show that

the goal of modeling coupled longitudinal and lateral--directional

characteristics at the same time using the same inputs is feasible.

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