Experimental Study of Internal Waves Due to the Movement of a Cylindrical Body in a Density Stratified Fluid

In the case of an internal force in stratified fluid, internal waves are one of the most important phenomena that occurs in the stratified oceanic environment. This study was conducted to investigate internal waves and turbulent wake effect behind a cylindrical body in a linear stratified environment in laboratory. In this work, in a glass tank with dimensions of 3×1×0.5 (m), a linear stratification with buoyancy frequency (N) of 0.51 (s-1), was set up. Then a cylindrical body of 6 cm diameter and 45 cm long was towed in the fluid, while changing the Froude and Reynolds numbers of the flow and the effect of these changes on the formation of the internal waves and wake of the cylinder, at speeds of 5 mm/s to 4.5 cm/s, using a computer controlled system, were examined. In this work shadowgraphs technique was used to capture the flow. The results show that the presence of internal waves depend on changes of Froude and Reynolds numbers of the flow, and maximum internal waves activities were found when Froude number was tended to the critical values of one; the wavelength of the internal waves was also increased with Froude number. In the range of the supercritical Froude number the flow consisted of a turbulence wake in the environment, also relatively increasing irregular shorter waves were observed around the cylinder. Detection of such waves at a distance from the cylinder was one of the objective of the present work.