Velocity statistics of plane self-preserving buoyant turbulent adiabatic wall plumes

Measurements of the velocity properties of plane buoyant turbulent adiabati c wall plumes (adiabatic wall plumes) are described, emphasizing conditions far from the source where self-preserving behavior is approximated. The ex periments involved helium/air mixtures rising along a smooth, plane, and ve rtical wall. Mean and fluctuating streamwise and cross-stream velocities we re measured using laser velocimetry. Self-preserving behavior was observed 92-156 source widths from the source, yielding smaller normalized plume wid ths and larger near-wall mean velocities than observations within the flow development region nearer to the source. Unlike earlier observations of con centration fluctuation intensities, which are unusually large due to effect s of streamwise buoyant instabilities, velocity fluctuation intensities wer e comparable to values observed in nonbuoyant turbulent wall jets. The entr ainment properties of the present flows approximated self-preserving behavi or in spite of continued development of the wall boundary layer. Measuremen ts of temporal power spectra and temporal and spatial integral scales of ve locity fluctuations are also reported.