[M-GI29] 計算科学が拓く宇宙惑星地球科学

[MGI29-07] Dust growth simulation using direct numerical simulation of turbulence

*石原 卓¹、河原 昌平²、梅村 雅之² (1.岡山大学大学院環境生命科学研究科、2.筑波大学)

キーワード：原始惑星系円盤、ダスト成長、乱流、直接数値計算

Planetesimals are believed to be formed by repeated collisions and coalescence of dust particles in the turbulent gas of protoplanetary disks. However, it is generally believed that the larger the dust particles grow in the turbulence the larger the collision velocity, leading to 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 (DNS) of the Navier-Stokes equations have been used to study the collision processes of dust particles in turbulence. Ishihara et al (2018) conducted a DNS of incompressible turbulence at a high Reynolds number (Re=16,100) and showed that the DNS value of the mean relative velocity of particle pairs is less than half of the standard theoretical estimate by Ormel and Cuzzi (2007). The DNSs also showed that the sticking probabilities of particles with large inertia are higher than the standard theoretical estimate. These results are convenient for colliding dust particles to grow. However, the sticking probabilities of particles with large inertia are still small and how the dust particles with large inertia can repeatedly collide at low speeds in turbulence is still unresolved. Recently, we utilised a DNS of turbulence and conducted dust growth simulations setting a critical collision velocity for dust particles in the turbulence. The simulation results suggest that repeated low-speed collisions may be possible at low enstrophy regions in turbulence and also that as a consequence of this dust growth is accelerated in turbulence.