Flow and Turbulence Structure past a Cluster of Freshwater Mussels

Abstract

Freshwater mussels are bivalve mollusks that inhabit the substrates of rivers. Their conservation is important to maintain a healthy river ecological system. The present study uses state-of-the-art experimental and numerical techniques to investigate flow and turbulence structure and to estimate the bed friction velocity distributions around a cluster of three semiburrowed mussels placed at a bottom of a flat-bed channel. The ability to describe and quantify these processes and mechanisms is a prerequisite to understanding how mussels are dislocated from the bed and to better comprehend biological aspects related to the life and role (e.g., nutrient transport) of these aquatic organisms. The large-eddy simulation (LES) study provides a detailed discussion of the flow physics and the role of large-scale coherent structures for a case in which the incoming flow is perpendicular to the shells of the mussels. For this limiting test case, strong necklace vortices develop around the upstream base of the mussels and massive separation occurs past the mussels. This provides an extremely complex turbulent flow field that is very challenging to predict using numerical models. As part of the study, data from particle image velocimetry (PIV) are compared with LES. The model can be used as a tool to investigate flow and transport processes at mussel scale for a variety of relevant flow conditions.