Importance of the Basset History Force in Point-Particle Approaches for Modeling Suspended Sediments in Oscillatory Flow

Abstract:

Modeling suspended sediments in an oscillatory flow, representative of coastal environments, using an Euler-Lagrange point-particle approach requires accurate prediction of the interactions between the particles and the fluid phase. In the present work, the fluid phase momentum and continuity equations are solved in an Eulerian framework while the particles are treated as subgrid point sources in the flow and advanced in a Lagrangian framework with closure models for different forces exerted by the fluid on the particle following the Maxey & Riley equation. Of particular importance for slightly-heavier-than-fluid particles is the Basset history force, which is commonly neglected owing to its extensive computational overhead, yet may have a significant influence on fundamental sediment transport properties including particle relaxation time and settling rate in turbulent flow. An efficient and accurate reduced order approach developed by Hinsberg et al (JCP, 2011) is applied here to compute the history force, the effects of which are evaluated in a series of experiments.
The effectiveness and importance of the history force is first evaluated for single particle and group settling for different particle Stokes and Reynolds numbers in a quiescent fluid to show that the history force modifies the particle relaxation time. An extension to oscillatory flow is next investigated in an idealized manner by adding a time-periodic gravity field, and the effects of different periods of oscillation are evaluated. Finally, the effects on the evolution of a realistic suspended sediment flux in oscillatory flow with vortex ripple and sheet flow conditions are evaluated by using the DNS data of Finn et al (JFM 2016).