Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
4993204 | International Journal of Heat and Fluid Flow | 2017 | 6 Pages |
Abstract
Vorticity dynamics plays an essential role in the description of turbulent flows, so an alternative definition of the mixing length (lÏ=yHâyL, where yH and yL represent the transverse boundary positions of turbulent shear layer at the high- and low-speed free streams, respectively) in a turbulent planar mixing layer, based on the shear induced vorticity field, is suggested in this study. A theoretical analysis for determining the values of yH and yL in the self-preserving development region is presented. An experimental study that demonstrates the self-preserving state in planar turbulent mixing layer is next made with particle image velocimetry (PIV) measurements to support the theoretical results. It is shown that “a linear growth rate of lÏ along stream-wise distance” can be now used as the necessary and sufficient conditions to identify the achievement of a self-preserving state in a turbulent mixing layer. Another advantage of this alternative definition of mixing length is that lÏ gives a better sectional range of shear turbulence in a turbulent mixing layer than the usual definitions of mixing length, which are determined on the basis of the mean velocity field, such as lu.
Related Topics
Physical Sciences and Engineering
Chemical Engineering
Fluid Flow and Transfer Processes
Authors
K.-C. Chang, K.-H. Lee,