title: Fluid mixing in stratified gravity currents: the Prandtl mixing length.
abstract: Shear-induced vertical mixing in a stratified flow is a key ingredient of thermohaline circulation. We experimentally determine the vertical flux of momentum and density of a forced gravity current using high-resolution velocity and density measurements. A constant eddy-viscosity model provides a poor description of the physics of mixing, but a Prandtl mixing length model relating momentum and density fluxes to mean velocity and density gradients works well. For the average gradient Richardson number Ri(g) approximately 0.08 and a Taylor Reynolds number Re(lambda) approximately 100, the mixing lengths are fairly constant, about the same magnitude, comparable to the turbulent shear length.
authors.affiliation: Condensed Matter and Thermal Physics Group and Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
authors.forename: P
authors.initials: P
authors.lastname: Odier
authors.forename: J
authors.initials: J
authors.lastname: Chen
authors.forename: M K
authors.initials: MK
authors.lastname: Rivera
authors.forename: R E
authors.initials: RE
authors.lastname: Ecke