Characteristics of Small Vortices in a Turbulent Axisymmetric Jet

Abstract

Characteristics of small vortices were studied in axisymmetric jets wherein the Kolmogorov scale was approached by progressively decreasing the Reynolds number while still maintaining turbulent flow. A periodic forcing introduced far upstream of the jet nozzle ensured that the jet was turbulent. A vortex eduction tool was developed and applied to the high-pass filtered 2D velocity field in the axial plane of a turbulent jet while varying Re between 140 and 2600. Vortex population, energy, vorticity, and rms (root-mean-square velocity fluctuations) of the high-pass filtered field were measured to elucidate vortex characteristics. The observed population of vortices decreases dramatically at the Kolmogorov scale. The observed increase in vortex population with decreasing vortex size appears to be in accord with the space-filling argument, in that the vortex population in a two-dimensional domain should grow as R−2. The energy density curve obtained from vortex statistics reproduces the −5∕3 slope for the inertial subrange, and the high-pass filtered field accounts for approximately two-thirds of the total rms.

Highly resolved large eddy simulations of a binary mixture flow in a cavity with two vents: Influence of the computational domain

“…In the followings, a uniform unstructured cubic mesh of size δ = 7 × 10 −4 m, per cell in each direction, has then been generated for the six configurations. Following the work of Chhabra et al [22], the Kolmogorov length scale can be estimated at η = 2.1 × 10 −4 m (leading to a ratio δ/η = 3.3).…”

Experimental and computational study of turbulent mixing in a confined rectangular jet

“…Of particular interest to the present study. Agrawal and Prasad (2003) and Chhabra et al (2006) reported results on small-scale vortices present in the axial plane of a self-similar turbulent axisymmetric jet by using a high-pass filter and vortex extraction method based on velocity quadrant and angular variance. These studies include measurements of the vortex characteristics, such as the vortex population, energy, vorticity, and rms of velocity fluctuations.…”