1994/09/10 by F. J. Higuera · 4 citations
Engineering · #Hydraulic flow and structures #Fluid Dynamics and Turbulent Flows #Fluid Dynamics and Vibration Analysis
paper · doi:10.1017/s0022112094002041
The hydraulic jump appearing in the viscous laminar flow of a thin liquid layer over a finite horizontal plate is studied using the boundary-layer approximation for the flow in and around the jump. The position and structure of the jump are determined by numerically solving the resulting problem with a boundary condition at the edge of the plate that expresses the matching of the layer with the shorter region where the liquid turns around and falls under the action of gravity. When the Froude number of the flow ahead of the jump is very large, the jump is much shorter than the horizontal extent of the layer, though still much longer than its depth. An asymptotic description of the inner structure of such a jump is given, building upon the analysis of Bowles & Smith for the short interaction region at the leading end of the jump. This structure consists of a fast moving separated flow in the upper part of the layer that progressively slows down by ingesting new fluid across its lower boundary, until the hydrostatically generated adverse pressure gradient makes it recirculate in the lower part of the layer. The effects of the surface tension and the cross-stream pressure variation owing to the curvature of the streamlines are taken into account in the jump and in the flow approaching the edge of the plate, showing that they can lead to quantitative and also qualitative changes of the jump structure, including a local breakdown of the boundary-layer approximation.