A hydraulic jump is a phenomenon that occurs when a high-velocity liquid transitions to a region where the liquid slows. The fluid rises in height, turbulence increases, and air is entrained into the flow forming bubbles after the transition. Energy dissipation and higher rates of gas transfer also occur. This phenomenon is useful for engineering purposes such as energy dissipation and increasing oxygen concentration in water downstream of a dam. As with other problems in fluid flow, hydraulic jumps can be simulated with the use of high-performance computers.
In a recent paper, MSI Principal Investigators Professor John Gulliver (Civil, Environmental and Geo- Engineering, St. Anthony Falls Laboratory) and Associate Professor Lian Shen (Mechanical Engineering, St. Anthony Falls Laboratory Associate Director for Research), along with Research Assistant Adam Witt, used computer modeling to create simulations of hydraulic jumps. Earlier simulations did not numerically simulate the process of bubble formation and experimental characterizations had to be input into the simulations. The authors have developed simulations that numerically predict the air-water flow characteristics of a hydraulic jump without this step. The paper was published in the International Journal of Multiphase Flow in June 2015. (Adam Witt, John Gulliver, and Lian Shen. 2015. Simulating Air Entrainment and Vortex Dynamics in a Hydraulic Jump. International Journal of Multiphase Flow 72:165-180. DOI: 10.1016/j.ijmiltiphaseflow.2015.02.012.)
Professor Gulliver is currently using MSI resources for investigations into the infiltration of water that occurs at roadside drainage ditches with Professor John Nieber and for studies into turbulence close to a free surface. Professor Shen uses computational fluid dynamics to perform high-resolution simulations of wind and water wave flows. Dr. Witt was a student in Professor Gulliver’s MSI research group and is currently employed at the Oak Ridge National Laboratory.
Image Description: Visualization of the eddy structure in a hydraulic jump. Left: instantaneous vorticity contours through a 2D x–y plane down the center of the domain. Vorticity maxima inside a vorticity contour are indicated by A through F. Bubbles are represented by a volume fraction isosurface on γ = 0.95*. Right: a color contour map of vorticity contours through a 2D plane down the center of the domain. White areas indicate regions of high void fraction. Top and bottom rows are separated by 0.2 seconds.
* volume fraction of fluid, γ, indicates ratio of fluid to air in each computational cell
(Image, A Witt et al., Int J Multiphase Flow 72:165-180.)
posted on March 10, 2016