Date of Award


Document Type


Degree Name

Master of Science (MS)


Mechanical Engineering

Committee Member

Joshua Bostwick, Committee Chair

Committee Member

John Saylor

Committee Member

Richard Miller


Hydraulic jumps are characterized by flows with an abrupt change in the fluid height, as seen in tidal basins, rivers, and dam spillways. They also occur on smaller scales and we have developed a small-scale table top experiment consisting of an impinging fluid jet impacting a horizontal plate to systematically study the geometry of the hydraulic jump. Striking polygonal shapes are observed which depend upon the flow of the impinging jet, fluid properties, weir geometry and the flow history. These steady shapes are reflective of a balance of inertial, pressure, and surface tension forces. The effect of weir height and geometry on the modal behavior and jump geometry is studied. Two experimental protocols are introduced that illustrate the effect of flow history and hysteresis in the formation of polygonal hydraulic jumps. This highlights the nonlinearity inherent in mode selection. We are able to collapse all of our experimental data with the Weber number using the downstream fluid height as the characteristic length scale. The critical wavelength is shown to be approximately constant which strongly implies the mode selection mechanism is related to Plateau-Rayleigh breakup. Our results highlight the complex multiphysics involved in this phenomena.