Steady turbulent density currents on a slope in a rotating fluid. (2nd April 2014)

• Record Type: Journal Article
• Authors: Manucharyan, G. E.; Moon, W.; Sévellec, F.; Wells, A. J.; Zhong, J.-Q.; Wettlaufer, J. S.
• Is Part Of: Journal of fluid mechanics. Volume 746(2014:May)
• Page Start: 405
• Page End: 436
• Publication Date: 2014-04-02
• Subjects: gravity currents, -- rotating flows, -- turbulent mixing; Fluid mechanics -- Periodicals; 532.005
• DOI: 10.1017/jfm.2014.119
• Languages: English
• ISSNs: 0022-1120

Abstract

Abstract: We consider the dynamics of actively entraining turbulent density currents on a conical sloping surface in a rotating fluid. A theoretical plume model is developed to describe both axisymmetric flow and single-stream currents of finite angular extent. An analytical solution is derived for flow dominated by the initial buoyancy flux and with a constant entrainment ratio, which serves as an attractor for solutions with alternative initial conditions where the initial fluxes of mass and momentum are non-negligible. The solutions indicate that the downslope propagation of the current halts at a critical level where there is purely azimuthal flow, and the boundary layer approximation breaks down. Observations from a set of laboratory experiments are consistent with the dynamics predicted by the model, with the flow approaching a critical level. Interpretation in terms of the theory yields an entrainment coefficient $E\propto 1/\Omega $ where the rotation rate is $\Omega $ . We also derive a corresponding theory for density currents from a line source of buoyancy on a planar slope. Our theoretical models provide a framework for designing and interpreting laboratory studies of turbulent entrainment in rotating dense flows on slopes and understanding their implications in geophysical flows.