Circular hydraulic jumps triggered by boundary layer separation

H. C. Chang, E. A. Demekhin, P. V. Takhistov

Research output: Contribution to journalArticlepeer-review


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 Re1/3Λ-1/8, where Λ = (ga3/v2) Re-7/3 is a modified Froude number, Re = (Q/av) 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 Λ. When Λ 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.

Original languageEnglish (US)
Pages (from-to)329-338
Number of pages10
JournalJournal of Colloid And Interface Science
Issue number2
StatePublished - Jan 15 2001

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Biomaterials
  • Surfaces, Coatings and Films
  • Colloid and Surface Chemistry


  • Flow separation
  • Hydraulic jump
  • Jet


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