Journal ArticleDOI
Optimal disturbances and bypass transition in boundary layers
TLDR
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.Abstract:
Streamwise streaks are ubiquitous in transitional boundary layers, particularly when subjected to high levels of free-stream turbulence. Using the steady boundary-layer approximation, the upstream disturbances experiencing maximum spatial energy growth are numerically calculated. The calculations use techniques commonly employed when solving optimal-control problems for distributed parameter systems. The calculated optimal disturbances consist of streamwise vortices developing into streamwise streaks. The maximum spatial energy growth was found to scale linearly with the distance from the leading edge. Based on these results, a simple model for prediction of transition location is proposed. Available experiments have been used to correlate the single constant appearing in the model.read more
Citations
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Journal ArticleDOI
Boundary-layer receptivity to freestream disturbances
TL;DR: 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.
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.
Journal ArticleDOI
A Three-Equation Eddy-Viscosity Model for Reynolds-Averaged Navier-Stokes Simulations of Transitional Flow
D. Keith Walters,Davor Cokljat +1 more
TL;DR: In this article, an eddy-viscosity turbulence model employing three additional transport equations is presented and applied to a number of transitional flow test cases, which is based on the k- framework and represents a substantial refinement to a transition-sensitive model that has been previously documented in the open literature.
Journal ArticleDOI
Simulations of bypass transition
Robert G. Jacobs,Paul A. Durbin +1 more
TL;DR: In this article, a simulation of the laminar boundary layer passing through free-stream turbulence is performed numerically using numerical flow fields, and a method to construct turbulent inflow from Orr-Sommerfeld continuous modes is described.
References
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Book
Viscous Fluid Flow
TL;DR: In this article, the stability of Laminar Boundary Layer Flow Appendices has been investigated in Cylindrical and Spherical Coordinates of Incompressible Newtonian Fluids.
Book
Optimal Control of Systems Governed by Partial Differential Equations
TL;DR: In this paper, the authors consider the problem of minimizing the sum of a differentiable and non-differentiable function in the context of a system governed by a Dirichlet problem.
Journal ArticleDOI
Hydrodynamic Stability Without Eigenvalues
TL;DR: A reconciliation of findings with the traditional analysis is presented based on the "pseudospectra" of the linearized problem, which imply that small perturbations to the smooth flow may be amplified by factors on the order of 105 by a linear mechanism even though all the eigenmodes decay monotonically.