On the Periodic Motion of a Circular-Cylinder through a Linearly Stratified Fluid

The results of a series of experiments on the periodic motion of a horizontal circular cylinder through a linearly stratified fluid are described. For cases in which the motion is composed of a uniform horizontal translation and a superimposed sinusoidal variation in horizontal velocity, a number of different flow types are identified, and regime diagrams delineating the boundaries between the flow types are presented. Conditions for forward overshooting of wake fluid are discussed, and suitable scaling criteria are derived for the occurrence of the overshooting phenomenon. Comparisons are made between the unsteady flow data and those pertaining to steady flow counterparts having the same instantaneous parameter values, and the conditions for the generation of flow phenomena associated solely with the periodic nature of the motion are discussed. Quantitative data are presented on the dependence of typical wake region dimensions on the controlling dimensionless parameters.