Two-point correlations in high Reynolds number flat plate turbulent boundary layers

Abstract

Two-point correlations of turbulent boundary layer are presented for Reθ of 9800 and 19,100. The results are based on wind tunnel measurements performed in the 30 cm thick boundary layer of the 21.6 m long LML (Laboratoire de Mécanique de Lille) boundary layer research facility. Simultaneous hot-wire probe measurements of the entire boundary layer at 143 different points on an array are used for computation of the two-point correlations. The two-point correlations in the streamwise–spanwise plane at 11 different wall-normal positions covering one boundary layer thickness in the spanwise direction show that the maximal extension of the correlations in the streamwise direction is bounded within ±3.5δ for both of the Reynolds number tested. The shapes of the positive correlations in the streamwise–spanwise plane at different wall-normal positions are similar throughout the boundary layer from nearly the freestream to the wall. The correlations in the streamwise–wall-normal plane for 11 different wall-normal reference positions also show that the correlations in some cases cover the entire boundary layer. The streamwise extent of the correlations in the streamwise–wall-normal plane is about 7–8 boundary layer thicknesses. Two-point correlation maps for the streamwise–wall-normal plane reveal the existence of non-zero correlations between even the intermittent region and near-wall region.