Project Title:
A Prediction Method for High-Angle-of-Attack Aerodynamics
02.05-9457A
910193
A Prediction Method for High-Angle-of-Attack Aerodynamics
Nielsen Engineering & Research, Inc.
510 Clyde Avenue
Mountain View
CA
94043-2287
Patrick H.
Reisenthel
415-968-9457
LaRC
NAS1-19529
018
02.05-9457A
910193
Abstract:
A Prediction Method for High-Angle-of-Attack Aerodynamics
The occurrence of structural failures of the vertical tails on aircraft such as the
F-15, F-18, and possibly the F-22 is a problem of extreme importance. These failures
are due to aerodynamic interaction between the vertical tail and the unsteady vortical
flow. In order to avoid this adverse interaction it is necessary to predict the flow
in the early design stages so that appropriate steps can be taken. The key element
in predicting the unsteady airloads on the tail of an aircraft at high angles-of-attack
is a model of the vortex that emanates from the forebody, inlet, or leading edge
extension. This model should be capable of representing a burst vortex. The overall
model of the flow field could then be used to analyze the loading on the tails. Predicting
the unsteady flow that causes the failure of the tails will be explored. The goal
of this project is to produce an engineering tool for high angle-of-attack flows
significantly beyond the onset of stall by applying the simplest possible physical
models.
This engineering methodology and a prediction tool would help designers ensure that
the fatigue problems occurring on twin-tail tactical fighters do not arise in future
aircraft designs. This will be of considerable benefit to the federal government
and to the aerospace industry.
unsteady aerodynamics, unsteady separated flow, vortex breakdown, buffeting, aeroelasticity,
mathematical modeling, potential flow, computational fluid dynamics