Prof. Rockwell delivers keynote at symposium on shallow flows

Donald Rockwell, the Paul B. Reinhold Professor of mechanical engineering and mechanics, gave the keynote address at the International Symposium on Shallow Flows held recently at Delft University of Technology in The Netherlands.

The topic of Rockwell's address was "Vortex Formation in Shallow Flows." Delft is located in the coastal lowlands of The Netherlands, where the Rhine River flows into the North Sea, and where Dutch engineers are attempting to prevent loss of coastal land to the encroaching sea.

Rockwell has a grant from the National Science Foundation to study shallow-water vortex systems, which occur in shallow rivers, channels and lakes, and also in two-phase manufacturing systems.

In some instances, says Rockwell, the diameter of the vortex created by the flow of water against a fixed object is greater than the depth of the water into which the object is fixed. The shallow flows cause unsteady patterns and affect pollution-control systems, aquatic life, vegetation, sediment transport and bottom erosion.

In Lehigh's Fluids Research Laboratory, Rockwell's group of graduate students and visiting researchers uses particle imaging velocimetry to study the interactions of fluid flows with stationary and oscillating objects. The lab has a 30-foot-long, 3-foot-wide tank that generates waves of varying speeds, heights and frequencies. As the waves roll against an object in the tank, the researchers sprinkle micro-particles near the object, illuminate the particles with lasers, then use a digital camera take a "picture" of the vortex created by the interaction between flow and object.

The result is a quantitative image that tells researchers how flow patterns change over time.

Rockwell and a colleague from Brown University have developed a method of correlating the quantitative image obtained in the lab with computer-based simulations. Their article was published recently in the Proceedings of the Royal Society of London.