Transport of orientable motile or sedimenting plankton in turbulence
Date:
Understanding the transport of Stokesian swimmers such as motile microorganisms and artificial swimmers in complex flow is vital to many ecological and industrial applications. In particular, it is important to capture the two-way interactions between the flow and the swimmers. However, a key challenge in the continuum modelling for active suspension is that the transport of swimmers is coupled with the orientation, while the orientation is determined by the local flow field. Therefore, accurately modelling the swimmer phase as a continuum requires solving a variable in both positional and orientational space. When coupled with the flow equation, the direct numerical simulation of the equations would be too expensive unless some simplification is made.
Past models to reduce the equation are either inaccurate or not generalised enough to be applied in any arbitrary flow fields or turbulent flow. We will present a new local approximation model that gives the effective transport as a function of the local flow field and swimming. It overcomes the limitation of the past models while giving effective transport properties as a function of the local flow field more accurately. It can also be extended to estimate the effective sedimentation and dispersion of non-motile planktons.