Instantaneous Velocity and Wall Pressure Features in a Turbulent Boundary Layer.
ILLINOIS INST OF TECH CHICAGO FLUID DYNAMICS RESEARCH CENTER
Pagination or Media Count:
Instantaneous organized motions in a turbulent boundary layer are related to characteristic wall pressure signatures for 1500 Retheta 6000 and are compared with structures extracted from conditional averaging. The conditional velocity and pressure fields were obtained from velocity measurements performed at 176 separate locations in the streamwise-wall normal plane, and from one microphone mounted flush with the boundary layer test plate. Instantaneous realizations of the velocity and pressure field were obtained through high-resolution particle image velocimetry and an array of 39 microphones. The instantaneous and conditional flow fields showed that an adverse pressure gradient associated with a positive wall pressure was present beneath a large-scale shear layer structure separating high speed flow upstream from low speed flow dudx0. Only the instantaneous measurements showed that an isolated negative wall pressure was associated with a shear layer of positive dudx denoted here as an inverse shear layer the structure was washed out and therefore not observed in the conditional averaging calculations. The shear layer exhibited large vorticity with the same sense of rotation as the mean vorticity and localized regions of strong turbulence production along the interface, whereas the inverse shear layer did not.
- Fluid Mechanics