Candace E. Wark

Thermal measurements for jets in disturbed and undisturbed crosswind conditions

A direct comparison is made of the thermal field properties for a low-disturbance and a high-disturbance level condition affecting the low-temperature air jets introduced into gas turbine combustor aft sections in order both to cool the high-temperature gases and quench the combustion reactions. Sixty-four fast-response thermocouples were simultaneously sampled and corrected for their time constant effect at a downstream plane close to the jet exit. Histograms formed from independent samples were sufficiently smooth to approximate a pdf.

Velocity and wall shear-stress measurements in high-Reynolds-number turbulent boundary layers

Velocity and wall shear stress were measured using hot-wire anemometry in two distinct turbulent boundary layers in the National Diagnostic Facility and have demonstrated some new and unique features of the high Reynolds number turbulent boundary layer. In agreement with the literature, mean velocity profiles showed that the socalled logarithmic region grew continuously for increasing Reynolds number for all of the boundary layers confirming an extended disparity between small and large scale motion. It was also observed from the mean velocity profiles that surface roughness elements of less than 2 viscous lengths caused a noticeable overshoot of the log-law line as the Reynolds number increased which indicated the importance of surface roughness at high Reynolds number even when the roughness height was within the viscous sublayer. Spectra computed from long time-series of the streamwise velocity revealed a bi-modal distribution of energy in the boundary layer close to the wall (50 viscous units) asserting that the large-scale, lowfrequency motions of the boundary layer are important in the near-wall region. Direct shear stress measurements using wire-on-wall and MEMS sensors were compared to the Clauser prediction, and it was seen that the Clauser scaling tended to mask the streamwise (Re.,) dependencies of the boundary layer quantities.

Effect of plate manipulators on coherent structures in a turbulent boundary layer

A three-dimensional sampling grid was used to investigate the effect of manipulators on the ensemble-averaged velocities and pseudoinstantaneous distributions of the structures associated with Reynolds-stress producing events detected at the wall over the Reynolds number range 3400