Journal ArticleDOI
Boundary-layer receptivity to freestream disturbances
TLDR
The boundary-layer receptivity to external acoustic and vortical disturbances is reviewed in this article. But, the authors do not consider the effects of external acoustic or vortic disturbances on the boundary layer.Abstract:
The current understanding of boundary-layer receptivity to external acoustic and vortical disturbances is reviewed. Recent advances in theoretical modeling, numerical simulations, and experiments are discussed. It is shown that aspects of the theory have been validated and that the mechanisms by which freestream disturbances provide the initial conditions for unstable waves are better understood. Challenges remain, however, particularly with respect to freestream turbulenceread more
Citations
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Acoustic Forcing and Control of Reected Waves in
TL;DR: In this paper, the infrastructure of the Klebano{Saric Wind Tunnel is upgraded in anticipation of boundary layer sound receptivity experiments, and an active noise control system uses two speakers downstream of the test section to create upstream-traveling waves that destructively interfere with the reections.
DissertationDOI
Control of the secondary crossflow instability : direct numerical simulation of localized suction in three-dimensional boundary layers
TL;DR: In this paper, the effect of pinpoint hole suction in a 3D boundary-layer flow with crossflow was investigated by means of direct numerical simulation. But the results showed that the suction-induced increased wall shear is by far overcompensated by the much stronger decrease due to the transition delay resulting in an overall effective drag reduction.
Journal ArticleDOI
Optimal disturbances above and upstream of a flat plate with an elliptic-type leading edge
TL;DR: In this article, the Lagrangian approach is used to compute linear optimal disturbances in a spatially growing boundary layer around an elliptic leading edge, and the optimal initial condition with the largest potential for growth is a Tollmien-Schlichting-like wave packet that includes the Orr mechanism.
Model-Based Control of Tollmien-Schlichting Waves using DBD Plasma Actuators: An Experimental Study
TL;DR: In this paper, the feasibility and performance of a designed Linear Quadratic Gaussian (LQG) controller in attenuating Tollmien-Schlichting (TS) waves, in an experimental setting, was evaluated.
References
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Book
Stability and Transition in Shear Flows
TL;DR: In this article, the authors present an approach to the Viscous Initial Value Problem with the objective of finding the optimal growth rate and the optimal response to the initial value problem.
Journal ArticleDOI
A note on an algebraic instability of inviscid parallel shear flows
TL;DR: In this paper, it was shown that all parallel inviscid shear flows of constant density are unstable to a wide class of initial infinitesimal three-dimensional disturbances in the sense that, according to linear theory, the kinetic energy of the disturbance will grow at least as fast as linearly in time.
Journal ArticleDOI
Parabolized stability equations
TL;DR: Parabolized stability equations (PSE) have been used for aerodynamic design of laminar flow control systems as discussed by the authors, and they can be obtained at modest computational expense.
Journal ArticleDOI
Optimal disturbances and bypass transition in boundary layers
TL;DR: In this article, the authors used the steady boundary-layer approximation to calculate the upstream disturbances experiencing maximum spatial energy growth, which are numerically calculated using techniques commonly employed when solving optimal-control problems for distributed parameter systems.
Journal ArticleDOI
Reynolds number independent instability of the boundary layer over a flat surface : optimal perturbations
TL;DR: In this article, the dependence on initial conditions of the three-dimensional algebraic spatial instability of the Blasius boundary layer is examined by a recently developed method of receptivity analysis based on the upstream integration of adjoint equations.