Skip to Content

Shallow Water Free-Surface Instability

Experiment

Unsteady free surface waves generated in a shallow water flume over a bump are investigated with different measurement systems. Conventional wave gauges and standard particle image velocimetry systems are used to determine the wave profiles and flow velocity distributions around the bump. An imaging technique is developed to measure the duration, displacement, and size of the bulge-scar pattern of free surface deformation from the bump top to the primary wave crest, and a unique configuration of particle image velocimetry is used to measure the velocity distribution related to the free surface bulge-scar pattern, i.e. visualized free surface bulge is captured together with seeding particles in the stereo PIV recording. Test results indicate that a bulge-scar pattern of free surface deformation is related to a stream-wise vortex pair possibly resulting from the Görtler type centrifugal instability of flow over the convex bump surface or the Taylor-Dean instability of curved flow at the wave trough.

Sample Data

Free surface elevations in two selected cases: (a) mean wave profiles over the bump, (b) RMS values of free surface fluctuation, (c) spectrum map of free surface fluctuation in case #1, (d) spectrum map of free surface fluctuation in case #2.

Free surface elevations in two selected cases: (a) mean wave profiles over the bump, (b) RMS values of free surface fluctuation, (c) spectrum map of free surface fluctuation in case #1, (d) spectrum map of free surface fluctuation in case #2.

Stream-wise velocity distribution measured with 2D PIV in case #1: (a) Secondary flow vector map and vorticity distribution, (b) Distribution of RMS flow velocity fluctuation.

Stream-wise velocity distribution measured with 2D PIV in case #1: (a) Secondary flow vector map and vorticity distribution, (b) Distribution of RMS flow velocity fluctuation.

Visualized free surface deformation patterns from bump top to primary wave crest (a) Single bulge-scar pattern in case #1, (b) Multiple bulge-scar patterns in case #1, (c) Single bulge-scar pattern in case #2, (d) Multiple bulge-scar patterns in case #2.

Visualized free surface deformation patterns from bump top to primary wave crest (a) Single bulge-scar pattern in case #1, (b) Multiple bulge-scar patterns in case #1, (c) Single bulge-scar pattern in case #2, (d) Multiple bulge-scar patterns in case #2.

Note: If you use our data, please also use the following citations:

Reference

Gui, L., Yoon, H., Stern, F., “Experimental Investigation of Shallow Water Free Surface Instability over a Bump,” Experiments in Fluids, Submitted, 2013

 

 

 

Tags: ,
Last modified on July 1st, 2015
Posted on October 28th, 2013