Turbulent Flow in Pipes and Channels as Cross-Stream "Inverse Cascades" of Vorticity

Details Turbulent Flow in Pipes and Channels as Cross-Stream "Inverse Cascades" of Vorticity Turbulent Flow in Pipes and Channels as Cross-Stream "Inverse Cascades" of Vorticity

2008-09-06

arxiv.org/abs/0809.1165v2

Physics

Fluid Dynamics

38 pages, 2 figures; resubmitted to Physics of Fluids with some changes requested by referees

Scientific paper

10.1063/1.3013635

A commonplace view of pressure-driven turbulence in pipes and channels is as "cascades" of streamwise momentum toward the viscous layer at the wall. We present in this paper an alternative picture of these flows as "inverse cascades" of spanwise vorticity, in the cross-stream direction but away from the viscous sublayer. We show that there is a constant spatial flux of spanwise vorticity, due to vorticity conservation, and that this flux is necessary to produce pressure-drop and energy dissipation. The vorticity transport is shown to be dominated by viscous diffusion at distances closer to the wall than the peak Reynolds stress, well into the classical log-layer. The Perry-Chong model based on "representative" hairpin/horsehoe vortices predicts a single sign of the turbulent vorticity flux over the whole log-layer, whereas the actual flux must change sign at the location of the Reynolds-stress maximum. Sign-reversal may be achieved by assuming a slow power-law decay of the Townsend "eddy intensity function" for wall-normal distances greater than the hairpin length-scale. The vortex-cascade picture presented here has a close analogue in the theory of quantum superfluids and superconductors, the "phase slippage" of quantized vortex lines. Most of our results should therefore apply as well to superfluid turbulence in pipes and channels. We also discuss issues about drag-reduction from this perspective.

Affiliated with

Also associated with

No associations

Rating

Turbulent Flow in Pipes and Channels as Cross-Stream "Inverse Cascades" of Vorticity does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Turbulent Flow in Pipes and Channels as Cross-Stream "Inverse Cascades" of Vorticity, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Turbulent Flow in Pipes and Channels as Cross-Stream "Inverse Cascades" of Vorticity will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-5213