Author:
HAYNES TIM S.,REED HELEN L.
Abstract
The nonlinear development of stationary crossflow vortices over a 45° swept NLF(2)-0415 airfoil is studied. Previous investigations indicate that the linear stability theory
(LST) is unable to accurately describe the unstable flow over crossflow-dominated
configurations. In recent years the development of nonlinear parabolized stability
equations (NPSE) has opened new pathways toward understanding unstable
boundary-layer flows. This is because the elegant inclusion of nonlinear and non-parallel effects in the NPSE allows accurate stability analyses to be performed without
the difficulties and overhead associated with direct numerical simulations (DNS).
NPSE results are presented here and compared with experimental results obtained at
the Arizona State University Unsteady Wind Tunnel. The comparison shows that the
saturation of crossflow disturbances is responsible for the discrepancy between LST
and experimental results for cases with strong favourable pressure gradient. However,
for cases with a weak favourable pressure gradient the stationary crossflow disturbances
are damped and nonlinearity is unimportant. The results presented here clearly
show that for the latter case curvature and non-parallel effects are responsible for the
previously observed discrepancies between LST and experiment. The comparison of
NPSE and experimental results shows excellent agreement for both configurations.Through this work, a detailed quantitative comparison and validation of NPSE
with a careful experiment has now been provided for three-dimensional boundary
layers. Moreover, the results validate the experiments of Reibert et al. (1996), and
Radeztsky et al. (1993, 1994) suggesting that their databases can be used by future
researchers to verify theories and numerical schemes. The results show the inadequacy
of linear theories for modelling these flows for significant crossflow amplitude and
demonstrate the effects of weak curvature to be more significant than slight changes
in basic state, especially near neutral-stability locations.
Publisher
Cambridge University Press (CUP)
Subject
Mechanical Engineering,Mechanics of Materials,Condensed Matter Physics
Cited by
138 articles.
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