Flow-field and point velocity measurements in a barotropically unstable shear layer

A shear instability in a homogeneous rotating fluid is studied in a laboratory experiment. Geophysical situations where such shear layers play a role range from the breakdown of weather fronts to the atmospheres of the giant planets, as well as in the Earth's interior. Above a critical shear, the shear layer breaks up through an inertial instability, which is known as barotropic instability in Geophysical Fluid Dynamics. The flow then develops a string of vortices along the shear zone. This study used two complementary methods of measuring the flow, Laser Doppler Velocimetry and Particle Tracking Velocimetry. The respective merits of these two methods will be discussed, and how these techniques complement each other. It will become apparent that a combination of both methods is necessary to fully describe the flow structures and dynamics.