**Planetesimal precursors in turbulent protoplanetary disks**

In this project we will use direct numerical simulations of turbulence to study the effect on planetesimal precursors (~ 1cm - 10m). The goal is twofold: In one part we will measure turbulent relative velocities in high resolution local simulations, and in the other part we will determine the global distribution of solids in the "weather-pattern" of turbulent protoplanetary disks. Thus, we can determine the key parameters for the influence of turbulence on planetesimal formation from direct numerical simulations. The distribution of planetesimal precursors in the protoplanetary disk will be derived through global 3D-MHD simulations. We will also determine the degree to which the precursors can be concentrated locally in protoplanetary disks in particular in flow features such as spiral arms, high pressure regions or vortex structures. In addition we will derive collision speeds and probabilities as generated by the turbulence as a function of the particle size of the collision partners and of the location in the disk. The obtained data are an essential input for projects B1, B2, B3 and C2, and will also be used for project D2.

**Principle Investigators**

Dr. Hubertus Klahr

Prof. Dr. Wilhelm Kley