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Full-Text Articles in Physics
Robust Identification Of Dynamically Distinct Regions In Stratified Turbulence, Gavin D. Portwood, Stephen M. De Bruyn Kops, J. R. Taylor, H. Salehipour, C. P. Caulfield
Robust Identification Of Dynamically Distinct Regions In Stratified Turbulence, Gavin D. Portwood, Stephen M. De Bruyn Kops, J. R. Taylor, H. Salehipour, C. P. Caulfield
Mechanical and Industrial Engineering Faculty Publication Series
we present a new robust method for identifying three dynamically distinct regions in a stratified turbulent flow, which we characterise as quiescent flow, intermittent layers, and turbulent patches. The method uses the cumulative filtered distribution function of the local density gradient to identify each region. We apply it to data from direct numerical simulations of homogeneous stratified turbulence, with unity Prandtl number, resolved on up to 8192x8192x4092 grid points. In addition to classifying regions consistently with contour plots of potential enstropy, our method identifies quiescent regions as regions where ∊ ⁄ νΝ2 ~ Ο(1), layers as regions where …
Drag Reduction In Turbulent Flows Over Micropatterned Superhydrophobic Surfaces, Robert J. Daniello
Drag Reduction In Turbulent Flows Over Micropatterned Superhydrophobic Surfaces, Robert J. Daniello
Masters Theses 1911 - February 2014
Periodic, micropatterned superhydrophobic surfaces, previously noted for their ability to provide drag reduction in the laminar flow regime, have been demonstrated capable of reducing drag in the turbulent flow regime as well. Superhydrophobic surfaces contain micro or nanoscale hydrophobic features which can support a shear-free air-water interface between peaks in the surface topology. Particle image velocimetry and pressure drop measurements were used to observe significant slip velocities, shear stress, and pressure drop reductions corresponding to skin friction drag reductions approaching 50%. At a given Reynolds number, drag reduction was found to increase with increasing feature size and spacing, as in …