Numerical and analytical studies of single and multiphase starting jets and plumes

Abstract

Multiphase starting jets and plumes are widely observed in nature and engineering systems. An environmental engineering example is open-water disposal of sediments. The present study numerically simulates such starting jets/plumes using Large Eddy Simulations. The numerical scheme is first validated for single phase plumes, and the relationship between buoyancy and penetration rate is revealed. Then, the trailing stem behind the main cloud is identified, and the the formation number (critical ratio U[delta]t/D, where U, D and [delta]t are discharge velocity, diameter and duration) that determines its presence is determined as a function of plume buoyancy. A unified relationship for starting plumes is developed to describe behaviors from negative to positive buoyancy. In multiphase simulations, two-phase phenomena are clarified including phase separation and the effect of particle release conditions. The most popular similarity law to scale up from the lab to the field (Cloud number scaling) is validated by a series of simulations. Finally, an example of sediment disposal in the field is given based on the present study. In related theoretical analysis, an analytical model on the vortex ring is developed and found to agree well with the direct numerical simulation results.