Tangential oscillations of a circular disk in a stratified fluid

We present experimental measurements of internal waves generated by a an horizontal circular disk oscillating in a stratified fluid. Two particular cases are studied: horizontal (perpendicular to the axis of the disk) and vertical (parallel to the axis of the disk) oscillations. Velocity fields in a vertical plane are measured by particle image velocimetry and show that the wave takes place in a stationary cross-shaped wavepacket. The effect of the viscosity is characterized in both cases and we observe that viscosity is the motor of the generation of the wave in the case of horizontal oscillation. Experimental results are then compared to theoretical work previously done by Davis and Smith [J. Fluid. Mech., 656, 342 (2010)].