DIRECT NUMERICAL-SIMULATION OF PLANKTONIC CONTACT IN TURBULENT-FLOW

We have investigated planktonic contact rates in a turbulent flow simulated directly from the Navier-Stokes equations. Although our simulation is a low Reynolds number flow, Re-lambda = 38, it is realistic for the ocean. Particles advected by the flow field while swimming were modeled by a random walk generated from a Maxwell distribution. In order to deduce the effect of turbulence on the contact rate we also calculated the contact rates for swimming alone without turbulence. Our numerical method can quantify the increase in planktonic contacts due to turbulence. We show that the effect of turbulence is enhanced when the capture radius is increased. We compare our calculations with the Gerritsen and Strickler model as well as a classic thermodynamic particle collision model.