TURBULENT WAKES OF STRATIFIED FLOW PAST A CYLINDER

Laboratory measurements were carried out to investigate the evolution of a turbulent wake behind a right circular cylinder moving in a linea rly strati fluid . The flow field is mainly determined by the internal Froude number Fi and the Reynolds number Re, but at high Re, Fi becom es the only governing parameter. Measurements show that stratified tur bulent wakes can be classified into three how regimes, based on Fi. Wh en Fi<2, the wakes do not grow downstream, and remain at an approximat ely constant height. For 2<Fi<3, the wakes grow to a maximum height at Nt approximate to 5 and then collapse physically; for Fi>3, the maxim um height is achieved at Nt approximate to 2.5, before the collapse be gins. The evolution of such other length scales as the Ozmidov, Kolmog orov, overturning, and Thorpe scales and the maximum Thorpe displaceme nts was measured, and their behavior in the above Fi ranges was deline ated. Length scale diagrams for the evolution of stratified turbulence in cylinder wakes were constructed and compared with previous theoret ical predictions. The present results provide new insights into the ev olution, collapse, and long-term evolution of stratified turbulent flo ws. (C) 1995 American Institute of Physics.