Experimental investigation on flow passing a rectangular pit in an open channel flow
Journal
Journal of the Chinese Institute of Engineers, Transactions of the Chinese Institute of Engineers, Series A
Journal Volume
15
Journal Issue
4
Pages
391-397
Date Issued
1992
Author(s)
Abstract
Abstract A series of experimental studies were conducted to study the velocity profiles, distributions of turbulent intensity, and reattachment properties of flow passing a rectangular pit in an open channel. The measurements were taken using current meters with diameters of 5 mm; and nine different height/length ratios of rectangular pits were chosen. The phenomena observed here are very similar to those of the backward‐facing step flow. But this study is more complicated due to effects of the downstream step. The vertical velocity components were analyzed using continuity equations. Abrupt variations were found in the regions close to the upstream and downstream steps. Friction coefficients of the pit area were also investigated by analyzing the longitudinal variations of the boundary layer thickness. It is found that friction coefficient increases in the streamwise direction along the pit. Another important finding is that the reattachment length increases as Froude number increases when the Reynolds number is greater than 20,000, and decreases as the relative pit height increases.
Type
journal article