Measurements of density fluctuations in steady, buoyant plumes in crossflow

Abstract Measurements of density fluctuations in steady, buoyant plumes in crossflow are reported. The aim of the laboratory experiments is to obtain density time series within the elevated plume at various locations downwind of the source. Rms levels of density fluctuations are approximately equal in magnitude to the value of the local mean, but time series show that peak values are an order of magnitude greater than the local mean. Crosswind distributions of skewness and kurtosis show near Gaussian values at the center of the plume but indicate skewed and peaked distributions at the plumes' edges. Analysis of the conditional signal reveals that values of the intermittency and non-dimensional burst frequency are inhomogeneous; their product., the burst persistence time, is near constant, however. Evaluation of the duration and spacing between events indicates that instantaneously large density fluctuations will persist for non-dimensional distances of at least up to x / l B ∼ 1000.