We determine the initial condition on the laminar-turbulent boundary closest to the laminar state using nonlinear optimization for plane Couette flow. Resorting to the general evolution criterion of nonequilibrium systems we optimize the route to the statistically steady turbulent state, i.e., the state characterized by the largest entropy production. This is the first time information from the...

The mechanics of inhomogeneous turbulence in and adjacent to interfacial layers bounding turbulent and non-turbulent regions are analysed. Different mechanisms are identified according to the straining by the turbulent eddies in relation to the strength of the mean shear adjacent to, or across, the interfacial layer. How the turbulence is initiated and the topology of the region of turbulence a...

Swifts are aerodynamically sophisticated birds with a small arm and large hand wing that provides them with exquisite control over their glide performance. However, their hand wings have a seemingly unsophisticated surface roughness that is poised to disturb flow. This roughness of about 2% chord length is formed by the valleys and ridges of overlapping primary feathers with thick protruding ra...

A description of different inflow methodologies for turbulent boundary layers, including validity and limitations, is presented. We show that the use of genuine periodic boundary conditions, in which no alteration of the governing equations is made, results in growing mean flow and decaying turbulence. Premises under which the usage is valid are presented and explained, and comparisons with the...

The work on this theme will comprise a boundary layer analysis in channel flow. Here we will be looking at both the laminar and turbulent case of incompressible flow within the presence of shear stress and vorticity. This study for both cases is a very important concept to understand for boundary layers in channel flows. To accomplish this study, we used the Finite Element Method and Finite Vol...

The HYLIFE-II conceptual design uses arrays of high-speed oscillating and stationary slab jets, or turbulent liquid sheets, to protect the reactor chamber first walls. A major issue in thick liquid protection is the hydrodynamic source term due to the primary turbulent breakup of the protective slab jets. During turbulent breakup, drops are continuously ejected from the surface of turbulent liq...

tion models, in spite of some advances, the boundary layer is still not represented realistically. Figure 1 illustrates an aspect of this problem by showing the opposing response of boundary layer (low) clouds to perturbation experiments (e.g., double CO2) in current climate models. The general problem of parameterization in fluids dates back to the first modern studies of turbulence during the...