Study Of Asymmetric Vortical Flow On Forebody
At High Angle Of Attack
Author(s)
A.-ul-Haque & F. Umar
Abstract
In high angle of attack regimes, the formation of asymmetric vortices gives rise
to side forces and produces lateral instability in the aircraft. A lot of studies
(computational as well as experimental) have been carried out in the past decade,
but a universally accepted theory of the asymmetric triggering mechanism has
not yet been formulated. Growth rate maps of symmetric and asymmetric
vortices were developed and the sources of asymmetry in flow were pointed out.
The effects of Reynolds number, Mach number, grid resolution and of geometric
shape were simulated and the computed results were compared with known
experimental and computational data. Reynolds Average Navier Stokes
equations were employed with RNG k-ε turbulence modelling. Single block
structured grids for 5-degree semi-apex cone and several high incidence
asymmetric turbulent flow cases were computed. The strength and shape of
vortices were found to be different at different flow conditions for different
geometries. Randomness of asymmetric vortices was captured at high angle of
attack and with the increase in Reynolds number. The location where vortices
change from symmetric to asymmetric was observed moving towards the apex of
a body which shows that the physics of high speed resembles that of low speed
in some aspects and is being numerically validated for the first time. It was
concluded that the truncation error was basically the source of creating
asymmetry in flow at high angle of attack.
Keywords: vortical flow, high angle of attack, supersonic flow, turbulence
modelling, lateral instability, symmetric vortices, cone, primary and secondary
vortices, truncation error, geometric disturbances.
Keywords
vortical flow, high angle of attack, supersonic flow, turbulence
modelling, lateral instability, symmetric vortices, cone, primary and secondary
vortices, truncation error, geometric disturbances.
Related Book
Other papers in this volume
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