Ahmed Saad

Date of Award

8-14-2000

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Department of Aeronautics and Astronautics

First Advisor

Bradley S. Liebst, PhD

Abstract

Modern fighter designs have been associated with lateral self-excited oscillations own as "Wing Rock". Simulations of wing rock by flow visualization utilities have been encouraged to develop a complete understanding of the fluid mechanism that drives the motion as well as for prediction purposes. Previous wind/water tunnel simulations have been limited to a single degree-of freedom (DoF) in roll. In this study, for the first time, wing rock is computationally simulated in three DoF: roll, sideslip, and vertical motion to study the effect of adding file sideslip and vertical motion. The results are for a generic fighter model consisting of a fore-body, a cropped delta wing, and a vertical fin. The effect of including the vertical fin is also studied. The interaction of aerodynamics and rigid-body dynamics during a single DoF wing rock for the wing-body configuration has been studied via snap shots of a cross-plane stagnation pressure distribution and tracing the instantaneous locations of vortex burst for an entire cycle of wing rock. The effect of adding the sideslip and vertical motion DoF to the simulations of the wing-body configuration was found to delay file onset and to reduce the amplitude of wing rock by about 50% with surprisingly no change in frequency. The wing rock simulation in three DoF was repeated for file full generic fighter model with the fin included. The aerodynamic effect of the fin was found to significantly delay the vortex burst on the upper surface of the wing. The net effect of the fin was found to augment the damping of the oscillations with significant increase in frequency.

AFIT Designator

AFIT-DS-ENY-00-01

DTIC Accession Number

ADA390885

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