Some properties of truncated turbulence signals in bounded shear flows

Abstract

Earlier measurements of the contribution of four distinct classes of motions, i.e. (u < 0, v > 0), (u > 0, v < 0), (u < 0, v < 0) and (u > 0, v > 0), to the Reynolds stress $-\rho \overline{uv}$ in the wall region of a bounded turbulent shear flow have been extended. These classes were obtained by truncating the u and v signals about zero. Various statistical properties of the truncated streamwise and normal velocity components u and v and of their product uv have been determined in an attempt to characterize quantitatively the motions in this flow. Average values and probability density distributions both of the truncated and untruncated signals have been taken.

Coherent structures in flow over hydraulic engineering surfaces

“…Many characteristic elements have been recognized and documented in the near-wall layer, including: low-speed streaks with spacing of 100 viscous wall units and the burst process (Kline et al 1967), sweeps and ejections (Brodkey et al 1974), quasi-streamwise vortices, Q2/Q4 events (Wallace et al 1972, Willmarth andLu 1972) and associated variable integration time average (VITA) events (Blackwelder and Kaplan 1976) and inclined shear layers (Kim 1987). Here, Q2/Q4 refers to events in the second and fourth quadrants of the u − v map, which thus contribute a positive contribution to the Reynolds shear stress, −uv.…”

Large-eddy simulation of accelerated turbulent flow in a circular pipe

“…Quadrant analysis of the Reynolds shear stress −u v provides detailed information on the contribution of flow events to the production (or destruction) of turbulent kinetic energy (Willmarth and Lu, 1972;Brodkey et al, 1974). The contribution to the Reynolds shear stress from each quadrant is shown in Figure 10.…”

Turbulent flow and heat transfer in eccentric annulus

“…This supposition gets further support by quadrant analysis of the Reynolds shear stresses in different parts of the duct. The quadrant analysis, proposed in Willmarth & Lu (1972) and Brodkey, Wallace & Eckelmann (1974), provides the detailed information on the contribution of different flow events to the turbulence production. The analysis divides the Reynolds shear stress into four categories Q 1 -Q 4 according to the signs of longitudinal u z and wallnormal u n velocity fluctuations.…”