Circular Hydraulic Jumps Triggered by Boundary Layer Separation

✍ Scribed by H.-C. Chang; E.A. Demekhin; P.V. Takhistov

• Publisher: Elsevier Science
• Year: 2001
• Tongue: English
• Weight: 360 KB
• Volume: 233
• Category: Article
• ISSN: 0021-9797
• DOI: 10.1006/jcis.2000.7289

✦ Synopsis

When a high-flow-rate circular jet impinges vertically on a horizontal plane, it flows out radially and then undergoes a distinctive hydraulic jump on the plane because of boundary layer separation induced by hydrostatic back pressure. The jump radius is shown to be 0.37 a Re 1/3 -1/8 , where = (ga 3 /ν 2 ) Re -7/3 is a modified Froude number, Re = (Q/aν) is the jet Reynolds number, a is the jet radius, and Q the liquid flow rate, which is favorably compared to experimental data in the limit of small . When exceeds 3.0 × 10 -4 at low flow rates, the jump radius decreases below a minimum in the film depth and our experiments detect a different jump mechanism that may be triggered by capillary pressure rather than hydrostatic pressure.