10:45 AM - 11:00 AM
[MGI33-06] On the role of high Reynolds number turbulence in the dust coagulation process in a protoplanetary disk
Keywords:protoplanetary disk, dust coagulation process, turbulence
Planetesimals are believed to be formed by repeated collisions and coalescence of dust particles in a turbulent gas of protoplanetary disk. However, it is generally believed that the larger the dust particles grow in the turbulence the larger the collision velocity, leading fragmentation or bouncing. Therefore, we have not yet had a complete scenario of collisional growth of dust particles in protoplanetary disk. To discuss this problem, we need to quantitatively understand the role of turbulence.
In recent years, direct numerical simulations (DNSs) of the Navier-Stokes equations were used for the study of the collision velocities of dust particles in turbulence. Pan & Padoan (2015) performed a DNS of weakly compressible turbulence (Re~1,000, where Re is Reynolds number) to show that the rms relative velocity of particle pairs obtained by DNS is as small as a half of the standard theoretical estimate by Ormel and Cuzzi (2007). Ishihara et al (2018) conducted DNSs of incompressible turbulence at high Re (up to Re=16,100) to show that their results are consistent with those by Pan & Padoan (2015). They also showed that sticking probabilities of particle with large inertia obtained by the DNS are higher than the theoretical estimate. However, the reason is not clear and the flow structure in high Re turbulence which enables for particles to collide at low speed is also not clear.
Ishihara et al (2013) showed that there exist significant thin-shear layers constructed by elongated vortical eddies with microscale thickness in high Reynolds number turbulence. In this paper, we consider possible roles of such large-scale vortical structures in the growth of dust particles in high Reynolds number turbulence by tracking a large number (20483) of inertial particles in the DNS of turbulence with 40963 grid points.
In recent years, direct numerical simulations (DNSs) of the Navier-Stokes equations were used for the study of the collision velocities of dust particles in turbulence. Pan & Padoan (2015) performed a DNS of weakly compressible turbulence (Re~1,000, where Re is Reynolds number) to show that the rms relative velocity of particle pairs obtained by DNS is as small as a half of the standard theoretical estimate by Ormel and Cuzzi (2007). Ishihara et al (2018) conducted DNSs of incompressible turbulence at high Re (up to Re=16,100) to show that their results are consistent with those by Pan & Padoan (2015). They also showed that sticking probabilities of particle with large inertia obtained by the DNS are higher than the theoretical estimate. However, the reason is not clear and the flow structure in high Re turbulence which enables for particles to collide at low speed is also not clear.
Ishihara et al (2013) showed that there exist significant thin-shear layers constructed by elongated vortical eddies with microscale thickness in high Reynolds number turbulence. In this paper, we consider possible roles of such large-scale vortical structures in the growth of dust particles in high Reynolds number turbulence by tracking a large number (20483) of inertial particles in the DNS of turbulence with 40963 grid points.