Higher-order statistics of turbulent fluctuations in the plane wake

Abstract

Skewness and flatness factors of the velocity components, u, v, w, the temperature fluctuations θ, and of the momentum and heat transport correlations uv and vθ in the two-dimensional turbulent far wake are presented. Standard deviations σuv and σvθ are also included. Observed profiles are critically reviewed and discussed in conjunction with other available data. Among the interesting findings are a change of sign of the skewness of u and θ near the wake centerline and the existence of double minima in the flatness factors of u, v, and θ. The minimum of Kθ is only 2. Here σuv and σvθ show high and broad maxima at the centerline. The coefficients ∼((uv)2)/ ∼(u2 v2) and ∼((vθ)2)/∼(v2 θ2) were introduced to indicate the degree of correlation between the u and v fluctuations, and between the v and θ fluctuations in eddies regardless of sign. Surprisingly the highest degree of correlation is obtained at the wake centerline. The information thus provided will be helpful to workers developing use of probability density functions in prediction methodology. Quantitative physical insights are gained as well.