Séminaire du Dr Hamidreza Ardeshiri ancien doctorant du LOG (thèse soutenue en octobre 2016) intitulé :
Dynamics of Copepods in Turbulent Flows
Date : 20 janvier 2017 à 11h
Lieu : salle de conférences à la MREN (Wimereux)
Copepods swimming behavior usually exhibits quick powerful jumps. Such an aptness is used to escape from high shear regions, which may be caused either by flow perturbations, produced by a large predator (i.e., fish larvae), or by the inherent highly turbulent dynamics of the ocean. The research presented this thesis is organized into three steps. First, recorded velocity tracks of copepods displaying escape response jumps in still water are here analyzed and used to define and tune a Lagrangian copepod (LC) model. Second, the model is further employed to simulate the behavior of thousands of copepods in a fully developed hydrodynamic turbulent flow obtained by direct numerical simulation of the Navier-Stokes equations. Third, numerical data analysis are performed to quantify copepods’ dynamics in turbulence and make a comparison with available experimental observations of copepods in turbulence.
Through this combined experimental and numerical study, we investigate the small-scale distribution of copepods in a turbulent environment and its dependency on the jump intensity, jump orientation, jump latency time and geometrical aspect ratio of the copepods. At last, possible ecological implications of the observed clustering on encounter rates and mating success are provided.