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New Developments: Flow Structures around Mussels

Posted on November 13th, 2012
Seyed Mohammad Hajimirzaie ("Haji")

Seyed Mohammad Hajimirzaie (“Haji”)

A new video produced by CGRER explores how research conducted by IIHR PhD student Seyed Mohammad Hajimirzaie (“Haji”) focuses on the flow structures around obstacles in rivers and steep mountain streams, such as mussels.

Haji works with faculty member James Buchholz; their work examines the hydrodynamics of flow and sediment transport around small aspect ratio obstacles, such as mussels. Their work is motivated by the need for a better understanding of transport mechanisms in fresh water mussel populations. Mussels have small aspect ratios when compared to other bodies that can block flow—a bridge pier, for instance—and this makes the flow more complex.

Haji’s research includes experiments in the flume with cylinders and a semi-ellipsoidal physical model geometrically similar to a mussel. Profound change in the vortex topology was observed, for a subtle change in geometry, which has an effect on transport in the wakes of bodies, Haji says. This will have important implications on the modeling of vortex structures in this class of flows.

Haji’s flume study uses particle image velocimetry (PIV), an experimental technique to measure velocity fields in the flow around the mussel. “It’s really interesting,” he says. “Before this I never thought that the flow structure around small things, like mussels, could be important, or so very complicated.”

But even though the mussel research is on a small scale, its application far exceeds mussel research. “Our work can be expanded to very different engineering applications—control surfaces on aircraft and underwater vehicles, sails, and cowlings on submarines; components on electronic circuit boards; buildings and exhaust stacks; and boulders, clusters, and fish habitat structures on river beds. It’s quite interdisciplinary,” Haji explains.

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