Instantaneous velocity fields in the x-y plane of a zero pressure gradient turbulent boundary layer are measured using particle image velocimetry. It is found that there exist random, time-varying zones in the U-V fields in which the streamwise momentum is remarkably uniform. The largest dimension of a typical zone is proportional to the boundary layer thickness. The zone closest to the wall co...

Direct numerical simulations (DNS) are carried out to study the laminar stability properties of an effusioncooled adiabatic flat-plate boundary layer at Mach 6. Through four aligned rows of holes, cold gas is blown into the boundary layer at the wall and background disturbances are excited at the wall upstream of the holes. Two cases are compared, with small and large spanwise spacing of the ho...

Abstract Free-stream turbulence (FST) alters the boundary layer of wind turbine blades, changing hydrodynamic stability and near wake. Large-eddy simulations (LES) a blade section with laminar separation bubble for several intensities ( TI ) Reynolds number 10 5 are performed. The effects boundary-layer streaks generated by FST on Tollmien-Schlichting (TS) Kelvin-Helmholtz (KH) instabilities an...

A new high Reynolds number wind-tunnel facility at New Mexico State University (NMSU) was fitted with a roughened surface consisting of sheets of paper embossed by a Braille printer. The resulting roughness distribution was regular, three-dimensional and relatively sparse in the spanwise direction. Careful hot-wire studies show that the near-wall peak in turbulence intensity is reduced by the r...

The development of three-dimensional motions in a plane mixing layer was investigated experimentally. It is shown that superimposed on the primary, spanwise vortex structure there is a secondary, steamwise vortex structure. Three aspects of this secondary structure were studied. First, the spanwise vortex instability that generates the secondary structure was characterized by measurements of th...

Abstract. We perform direct numerical simulations of impinging shock-boundary layer interaction on a flat plate, in which the shock is not orthogonal to boundary flow. The analysis relies an idealized configuration, where spanwise flow component used introduce effect sweep angle between statistically two-dimensional and shock. A quantitative comparison carried out swept case corresponding unswe...

Effective gas exchange can be maintained in animals without the need for endotracheal intubation using external chest wall oscillation (ECWO). The clinical application of this technique has been limited by equipment which was either impractical or uncomfortable. We evaluated a prototype of a new oscillator in which an oscillatory profile of negative and positive pressure was imposed on a negati...

A composite drag control (CDC) combining the opposition (OC) and spanwise opposed wall-jet forcing (SOJF) methods is investigated. maximum reduction of about 33% obtained for CDC -- much higher than that produced by either individual method (namely, 19% SOJF 23% OC). Flow analysis shows can take advantage both OC to better suppress producing near-wall turbulent structures --vortices streaks. Ou...

This communication presents the results and conclusions of an experimental study of the near-separation region of a single-stream shear layer. The momentum thickness at separation (x=0) was θ0 = 9.6mm, with Reynolds number Reθ =4650. Boundary layer separation was caused by a sharp 90◦ edge. Detailed singleand multipoint measurements of the velocity field were acquired at the streamwise location...

The phenomenon of bursting, in which streaks in turbulent boundary layers oscillate and then eject low speed fluid away from the wall, has been studied experimentally, theoretically, and computationally for more than 50 years because of its importance to the three-dimensional structure of turbulent boundary layers. We produce five new three-dimensional solutions of turbulent plane Couette flow,...