Hydrodynamics of a Rotating Gas Disk Associated with Outflows

2023 Fiscal Year Final Research Report

• Project/Area Number: 19K03906
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 16010:Astronomy-related
• Research Institution: Chiba University
• Principal Investigator: Hanawa Tomoyuki 千葉大学, 先進科学センター, 特任教授 (50172953)
• Co-Investigator(Kenkyū-buntansha): 松本 洋介 千葉大学, 大学院理学研究院, 准教授 (20397475)
• Project Period (FY): 2019-04-01 – 2024-03-31
• Keywords: 原始星 / ブラックホール / 流体力学 / 数値シミュレーション

Outline of Final Research Achievements

We derived a difference equation from the fluid dynamics equation in the cylindrical coordinate system, by taking into account the effect that the radial (r) direction and azimuthal (φ) direction are different at the boundary between the center of the calculation cell and the azimuthal direction. The obtained difference equation not only maintains uniform flow, but also has the good property that no significant error occurs even when the resolution in the azimuthal direction around the z-axis is lowered to Δφ=60°. By using this difference equation, we can simulate the flow of gas accreting onto protostars using a cylindrical coordinate system while maintaining accuracy and with a relatively small amount of computation cost. We also created fluid models for the molecular cloud core TMC-1A and the protostar DG Tau, both of which exhibit significant asymmetry in gas accretion, and semi-quantitatively reproduced the results of observations of molecular radio emission lines.

Free Research Field

理論天文学

Academic Significance and Societal Importance of the Research Achievements

原始星などに付随する対称性の良い回転ガス円盤と、著しい異方性を示す降着流を同時にかつ精度良く数値シミュレーションできる手法が得られた。円筒座標系ではベクトル量の各成分が座標の曲りにより見かけの変化を示す。本研究で開発した局所的なデカルト座標系への座標変換を採用すると、見かけの変化は打ち切り誤差なしに求めることができる。これは多くの計算法で採用されているテーラー展開による見かけの変化の評価より本質的に優れている。局所的なデカルト座標系への変換という手法は、3次元極座標など曲線座標系一般に応用可能である。