Prediction of particle plume spreading in a quiescent ambient

Adrian C.H. Lai, S.N. Chan, J.W. Er, A.W.K. Law, Eric Adams

Wednesday 1 july 2015

12:00 - 12:15h at Antarctica (level 0)

Themes: (T) Special session, (ST) Marine outfall system

Parallel session: 9D. Special Session: Marine Outfall System

Spreading rate is an important parameter in predicting the particle plume mixing characteristics. Different from a single-phase plume in which its spreading rate is a constant, the spreading of particle plume varies with a number of dependent variables. In this study, we performed gravity-driven particle plume experiments in quiescent ambient to study the effects of particle size on the plume spreading rate. A particle plume was generated by releasing particles of density 2500 kg/m3 by gravity from a submerged hourglass in a water tank; particle size ranged 0.120 mm – 0.725 mm. The resulting plume spreading rate was measured and found to be significantly dependent on particle size. To predict the spreading rate, a two-phase integral model is proposed using a new spreading hypothesis accounting for the particle settling velocity; coupling between the solid and fluid phase is achieved by considering the drag forces acting on the particles by the fluid. The model predictions were in good agreement with observation, suggesting the key physics of this complicated flow has been well captured.