Yanhua Wu

Population trends of spanwise vortices in wall turbulence

The present effort documents the population trends of prograde and retrograde spanwise vortex cores in wall turbulence outside the buffer layer. Large ensembles of instantaneous velocity fields are acquired by particle-image velocimetry in the streamwise–wall-normal plane of both turbulent channel flow at

Spatial structure of a turbulent boundary layer with irregular surface roughness

\hbox{\it Re}_\tau\equiv u_*\delta/\nu=570

Outer-layer similarity in the presence of a practical rough-wall topography

, 1185 and 1760 and a zero-pressure-gradient turbulent boundary layer at

Spatial signatures of retrograde spanwise vortices in wall turbulence

\hbox{\it Re}_\tau=1400

Reynolds-Stress Enhancement Associated with a Short Fetch of Roughness in Wall Turbulence

, 2350 and 3450. Substantial numbers of prograde spanwise vortices are found to populate the inner boundary of the log layer of both flows and most of these vortices have structural signatures consistent with the heads of hairpin vortices. In contrast, retrograde vortices are most prominent at the outer edge of the log layer, often nesting near clusters of prograde vortices. Appropriate Reynolds-number scalings for outer- and inner-scaled population densities of prograde and retrograde vortices are determined. However, the Re

Visualization and Characterization of Small-Scale Spanwise Vortices in Turbulent Channel Flow

_\tau=570

Force measurements of flexible tandem wings in hovering and forward flights.

channel-flow case deviates from these scalings, indicating that it suffers from low- Re effects. When the population densities are recast in terms of fractions of resolved prograde and retrograde spanwise vortices, similarity is observed for

A study of energetic large-scale structures in turbulent boundary layer

100\,{ in channel flow and in both flows for

Visualization and characterization of near-wake flow fields of a flapping-wing micro air vehicle using PIV

100\,{ over the Re

Wave interaction with a surface-piercing body in water of finite depth: a parametric study

_\tau