Optimal perturbations and transition energy thresholds in boundary layer shear flows
نویسندگان
چکیده
منابع مشابه
Delaying transition in rotating boundary-layer flows
We investigate both the type I and II modes of stationary instability within the boundarylayer flow over a rotating disk. Extending the work of previous studies we find that the flow can be stabilised via the introduction of shear-thinning non-Newtonian fluids. Laminar-flow profiles are determined from a generalised von Kármán similarity solution. An asymptotic study is presented in the limit o...
متن کاملBoundary layer (shear-band) in frustrated viscoplastic flows
We show that frustrated creep flows of yield stress fluids give rise to a boundary layer, which takes the form of a liquid region of uniform significant thickness separating two solid regions. In this boundary layer the shear rate is approximately constant for a given flow rate and the layer thickness extremely slowly varies with the flow rate. Yield stress fluids such as concentrated colloids,...
متن کاملRapid path to transition via nonlinear localized optimal perturbations in a boundary-layer flow.
Recent studies have suggested that in some cases transition can be triggered by some purely nonlinear mechanisms. Here we aim at verifying such an hypothesis, looking for a localized perturbation able to lead a boundary-layer flow to a chaotic state, following a nonlinear route. Nonlinear optimal localized perturbations have been computed by means of an energy optimization which includes the no...
متن کاملBoundary layer transition in high-speed flows due to roughness
Direct numerical simulation (DNS) is used to study the effect of individual (hemispherical) and distributed roughness on supersonic flat plate boundary layers. In both cases, roughness generates a shear layer and counter–rotating pairs of unsteady streamwise vortices. The vortices perturb the shear layer, resulting in trains of hairpin vortices and a highly unsteady flow. Mach 3.37 flow past a ...
متن کاملShear Layer Stability Analysis in Later Boundary Layer Transition and MVG Controlled Flow
A 1-D and 2-D cylindrical flow stability is investigated in this paper. A typical velocity profile in a shear layer with infection point is studied first. The fluid motion is decomposed to two parts: the rotational part and shear part. Linear stability analysis shows the rotational part (like rigid body) is stable but the shear part is unstable. Of course, the shear layer with inflection point ...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
ژورنال
عنوان ژورنال: Physical Review Fluids
سال: 2020
ISSN: 2469-990X
DOI: 10.1103/physrevfluids.5.062401