Computational Studies of Two Dimensional Rayleigh Taylor Driven Mixing for a Tilted Rig

Abstract

A timedependent, incompressible, turbulent mixing problem, referred here to as the “tiltedrig,â€‌ is defined, based results from an experiment that involved the introduction of a largescale overturning motion, with a superposed localized RayleighTaylor (RT) driven mixing. The problem serves to examine the development of RT turbulent mixing while being strained by a largescale twodimensional confined motion. Care is taken to define the problem in detail so others might use the definition, and the results, to help develop advanced models of buoyancy driven mixing in complex flows. Aside from a careful definition, the problem has been solved using two different implicitlargeEddysimulations (ILES) based codes, and with a direct numerical simulations (DNS) code. Twodimensional and onedimensional mix metrics are defined, and then used to examine the development of the mixing region, and the overall evolution of the flow. Comparison of simulations with experiment reveals that largescale overturning can be well captured in all the simulations, similarly central mix widths, and spike/bubble sidewall penetrations are also in good agreement. A comparison between the different simulation methodologies, ILES and DNS, reveals an overall good agreement between mix metrics such as the amount of molecular mixing. The DNS simulations reveal a dependency on Reynolds number that merits further experimental work.