Mixture fraction statistics of plane self-preserving buoyant turbulent adiabatic wall plumes

Measurements of the mixture fraction properties of plane buoyant turbulent adiabatic wall plumes (adiabatic wall plumes) are described, emphasizing co nditions far from the source where self-preserving behavior is approximated . The experiments involved helium/air mixtures rising along a smooth, plane and vertical wall. Mean and fluctuating mixture fractions were measured us ing laser-induced iodine fluorescence. Self-preserving behavior was observe d 92-155 source widths above the source, yielding smaller normalized plume widths and near-wall mean mixture fractions than earlier measurements. Self -preserving adiabatic wall plumes mix slower than comparable free line plum es (which have 58 percent larger normalized widths) because the wall preven ts mixing on one side and inhibits large-scale turbulent motion. Measuremen ts of probability density functions, temporal power spectra, and temporal i ntegral scales of mixture fraction fluctuations are also reported.