Small-scale isotropy of orificed, perforated plate turbulence

Abstract

The small-scale statistics of orificed, perforated plate (OPP) turbulence was studied over a range of Reynolds numbers based on Taylor microscale, Reλ, from 23 to 108. The streamwise velocity skewness, flatness, and the velocity spectra, deduced from hot-wire measurements taken at 70 D (where D is the diameter of the holes of the OPP) downstream of the OPP confirmed the turbulence to be quasi-isotropic. Application of the extended self-similarity concept enabled the analysis of the velocity structure functions of the small-scale statistics up to the sixth order. The ESS analysis revealed a large stretch of scaling region, despite the absence of a perceptible Kolmogorov inertial subrange. The values of the scaling exponents seem to affirm the superiority of the OPP over conventional grid in generating quasi-isotropic turbulence. The effects of Reλ on the extent of the scaling range and the scaling exponent were also explored.