1 May 2014
1 May 2014
Speaker: Liubin Pan (CfA)
Title:Clay Lecture: Dust Particle Dynamics in Turbulence
The collisional growth of dust grains in protoplanetary disks is a crucial process for understanding the challenging problem of planetesimal formation. To model the size evolution of dust grains, we need to examine the role of protoplanetary turbulence in setting the statistics of grain collisions. I will discuss the general dynamics of inertial particles in turbulence and its implications for dust particle collisions. Due to the finite inertia, dust particles exhibit inhomogeneous spatial distribution as they are expelled from vortices by a centrifugal force and cluster in the strain-dominated regions. The clustering intensity is strongest for particles that couple to the smallest eddies of the turbulent flow. We also investigate the collision velocity of dust particles induced by turbulent motions using both analytical modeling and numerical simulation. Our model shows that turbulence-induced collision velocity in general has two contributions, representing, respectively, the particles' memory of the spatial flow velocity difference they "saw" in the past, and the different responses of particles of different sizes to the flow velocity. We test our model prediction against the simulation data and compare with the commonly-used model in the literature. We show that the probability distribution of turbulence-induced collision velocity is highly non-Gaussian. The effects of turbulent clustering and the non-Gaussian collision velocity on the growth of dust particles will be discussed.