Author(s): Xiao Chen; Li Zeng; Yihong Wu
Keywords: No Keywords
Abstract: Understanding the swimming characteristics of Heterosigma akashiwo (H. akashiwo), is significant for modelling the migration of motile cells and corresponding ecological risk assessments associated with harmful algae in oceans and estuaries. Presented in this paper is a numerical computation for the probability density of swimming direction of H. akashiwo in a three-dimensional vorticity field, based on the finite volume method. The swimming velocity and translational diffusion tensor of H. akashiwo are found to change with the horizontal and vertical vorticity due to cell’s gyrotaxis. For the weak horizontal vorticity, algal cells are able to determine the swimming direction. When Bw < 0.9, the vertical swimming velocity is greater than the horizontal swimming velocity. For strong horizontal vorticity, cells cannot swimming towards a given direction. The vertical vorticity can affect the swimming characteristics of H. akashiwo, if the horizontal vorticity exists. The cells with larger rotational diffusivity have strong ability to keep swimming direction in the vorticity field.