Turbulence-induced collision velocity of dust particles

The collisional growth of dust grains in protoplanetary disks is a crucial process for understanding the challenging problem of planetesimal formation. To model the grain size evolution, we examine the role of protoplanetary turbulence in setting the collision statistics of dust particles. I will talk about the general dynamics of inertial particles suspended in turbulent flows, and focus on modeling the collision velocity of dust particles induced by turbulent motions. Our model shows that turbulence-induced collision velocity has two contributions, representing, respectively, the particles' memory of the spatial flow structures they "saw" in the past, and the different responses of particles of different sizes to the flow velocity. We test our model prediction against simulation data and compare with previous models. I will show that the probability distribution of turbulence-induced collision velocity is highly non-Gaussian, and discuss the effect of this non-Gaussianity on dust particle growth.