17:15 〜 18:30
[MGI35-P08] On the role of turbulence in the dust coagulation process in a protoplanetary disk
キーワード：原始惑星系円盤、ダスト成長、乱流
According to a standard model of planet formation, planetesimals are believed to be formed by repeated collisions and coalescence of dust particles in a turbulent gas of protoplanetary disk. This process may be enhanced by turbulence which regulate the motion of dust particles. On the other hand, it is generally believed that the larger the dust particles grow in the turbulence the larger the collision velocity, leading fragmentation or bouncing. This is known as barrier in the scenarios of collisional growth of dust particles.
In recent years, several studies on planetesimal formation based on direct numerical simulations (DNSs) of the Navier-Stokes equations have been performed. Pan & Padoan (2015) performed a DNS of weakly compressible turbulence (Re~1,000, where Re is Reynolds number) to understand motions of inertial particles. They showed that the rms relative velocity of particle pairs obtained by DNS is smaller by more than a factor of two, compared to that by Ormel & Cuzzi (2007). Ishihara et al (2018) conducted DNSs of incompressible turbulence at high Re (up to Re~16,100) to study the particle clustering. They showed that the results are consistent with those by Pan & Padoan (2015) and also that the collision statistics of particles with large inertia are not so sensitive to the Re. However, the barriers mentioned above are still remain unsolved.
To construct a possible scenario for dust particle growth in protoplanetary disk, it is necessary to understand the role of high Reynolds number turbulence in the collisional process. Ishihara et al (2013) showed that there exist complex 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 analyzing the DNS data of turbulence as well as the inertial particle data obtained in the DNSs of turbulence.
In recent years, several studies on planetesimal formation based on direct numerical simulations (DNSs) of the Navier-Stokes equations have been performed. Pan & Padoan (2015) performed a DNS of weakly compressible turbulence (Re~1,000, where Re is Reynolds number) to understand motions of inertial particles. They showed that the rms relative velocity of particle pairs obtained by DNS is smaller by more than a factor of two, compared to that by Ormel & Cuzzi (2007). Ishihara et al (2018) conducted DNSs of incompressible turbulence at high Re (up to Re~16,100) to study the particle clustering. They showed that the results are consistent with those by Pan & Padoan (2015) and also that the collision statistics of particles with large inertia are not so sensitive to the Re. However, the barriers mentioned above are still remain unsolved.
To construct a possible scenario for dust particle growth in protoplanetary disk, it is necessary to understand the role of high Reynolds number turbulence in the collisional process. Ishihara et al (2013) showed that there exist complex 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 analyzing the DNS data of turbulence as well as the inertial particle data obtained in the DNSs of turbulence.