ISSN Print: 1049-0787
ISSN Online: 2375-0294
Indexed in
UNSTEADY HEAT TRANSFER IN A CHANNEL OBSTRUCTED BY AN IMMERSED BODY
摘要
Channel flows obstructed by a rod and the related heat transfer were studied numerically and experimentally. From the numerical results, the flow was found to fluctuate in a highly periodic fashion and the Karman vortex formed downstream from the rod exhibited a crisscross motion in the obstructed channel flow. This crisscross motion was confirmed by a flow visualization experiment. From the viewpoint of time variation of instantaneous flow structure, the wavering motion of the separation layer on either side of the rod causes the high vorticity layer near the wall region to be lifted from the channel wall. The tip of this lifted tongue of the wall layer forms an isolated vortex and the circular fluid motion induced by the isolated vortex in the near wall region causes the washing action of the wall. The washing action entrains fresh and cooler fluid from the downstream side between the isolated vortex and the channel wall and is concluded to contribute to the enhancement of the wall heat transfer. From a statistical viewpoint, the presently studied periodic flow is different from turbulent flow in the sense that no irregularity of the flow fluctuation exists. However, this flow is similar to the turbulent flow in another sense that the values of uv and vθ take a nonzero value in some region.