The skin friction on a surface is a major concern by engineers. It is widely accepted that turbulent flow has higher friction than laminar flow due to the higher mixing in boundary layer. However, our new high order DNS found that the high friction is generated in a laminar zone in a transitional flow. Whenever the small length scales are generated, the velocity shear becomes very large in the ...

Introduction MicroChannel Fabrication Experimental Apparatus and Methodology Results and Discussion Summary and Conclusions CHAPTER 4 MICROPIV MEASUREMENT OF TURBULENT FLOW IN RECTANGULAR MICROCHANNELS WITH VARYING AS­ PECT RATIOS Abstract Introduction MicroChannel Fabrication Experimental Methodology Experimental Setup Measurement Error Results and Discussion Summary and Conclusions CHAPTER 5 ...

We develop a semianalytic formulation suitable for solving the Navier-Stokes equations governing the induced steady, axially symmetric motion of an incompressible viscous fluid confined in a wide gap between two differentially rotating concentric spheres. The method is valid for arbitrarily high Reynolds number and aids in the presentation of multiple steady-state flow patterns and their bifurc...

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We study reduced-order models of three-dimensional perturbations in linearized channel flow using balanced proper orthogonal decomposition BPOD . The models are obtained from three-dimensional simulations in physical space as opposed to the traditional single-wavenumber approach, and are therefore better able to capture the effects of localized disturbances or localized actuators. In order to a...

Numerical and experimental studies of transitional pipe flow have shown the prevalence of coherent flow structures that are dominated by downstream vortices. They attract special attention because they contribute predominantly to the increase of the Reynolds stresses in turbulent flow. In the present study we introduce a convenient detector for these coherent states, calculate the fraction of t...

This paper experimentally investigates the rheology of dense granular flow through its solid-like to fluid-like transition. Between the well-established flow regimes – quasi-static and grain-inertial – the physical description of the transition remains elusive. Our experiment uses a top-rotating torsional shear cell capable of ±1 μm accuracy in height and 5 decades (10−3 − 100 rad s−1) in rotat...

The activation threshold of B cells is tightly regulated by an array of inhibitory and activator receptors in such a way that disturbances in their expression can lead to the appearance of autoimmunity. The aim of this study was to evaluate the expression of activating and inhibitory molecules involved in the modulation of B cell functions in transitional, naive, and memory B-cell subpopulation...