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Three-dimensional hydrodynamic simulation of an accretion flow in a close binary system

封闭二元系统中吸积流的三维流体动力学模拟

基本信息

批准号：
03640267
负责人：
MATSUDA Takuya
金额：
$ 1.54万
依托单位：
KOBE UNIVERSITY (1992)Kyoto University (1991)
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1991
资助国家：
日本
起止时间：
1991 至 1992
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-03640267/
关键词：
accretion disc accretion x-ray star numerical simulation close binary wind accretion 渦状衝撃波数値流体力学 SS433 近接連星系

项目摘要

An accretion is a phenomenon by which gas falls onto a stellar surface by the stellar gravity. Interesting phenomena occur in close binary systems, in which one component star ejects gas while the other accretes it. Depending on the speed of the ejected gas, there are two modes of accretion, i.e. a wind accretion and an accretion disc. The purpose of the present research is to perform three-dimensional hydrodynamic computer simulations to clarify the behavior of these accretion flows.The present author performed two-dimensional numerical simulations of wind accretion flows. We found that the accretion flows were unstable and the bow shock formed in the upstream region of the compact object waves. The accreted gas conveys the angular momentum of both the positive and the negative sign onto the compact object. Because of it, the compact object may undergo the spin up and down sporadically. We termed this phenomenon as the flip-flop instability.If this instability occurs in nature, it may … More explain observations. However, since the computations were two-dimensional ones, the instability may be merely an artifact due to the restriction. In order to see if this phenomenon occurs in three-dimensional cases, we performed joint research with Anzer and Borner at the Max-Planck Institute, Garching and Livio in Israel(now in Baltimore). We found that the flow in three-dimensional case is less violent compared with two-dimensional counterpart.As to an accretion disc, we performed two-dimensional numerical simulations and found that spiral shocks were formed due to the tidal force by the companion star. The gas loses angular momentum by hitting the shocks and accretes onto the compact object.This phenomenon may be also an artifact due to the two-dimensional nature of the calculations. Sawada at Tohoku university and the present author performed a three-dimensional numerical simulation of an polytropic gas and found that the spiral shocks were formed. On the other hand, the three-dimensional SPH calculations performed by Nagasawa at the Institute of Computational Fluid Dynamics and the present author did not show marked spiral shocks. This discrepancy should be clarified in future researches.Chakrabarti at Tata Institute and the present author investigated the time variability of two-dimensional flows and applied the results to SS433. We found a good agreement of the computed results with observations. Less

吸积是气体在恒星引力作用下福尔斯落在恒星表面的现象。在密近双星系统中会出现一些有趣的现象，其中一颗星星喷出气体，而另一颗恒星则吸积气体。根据喷出气体的速度，有两种吸积模式，即风吸积和吸积盘。本研究的目的是进行三维流体动力学的计算机模拟，以澄清这些吸积流的行为。本作者进行了风吸积流的二维数值模拟。我们发现，吸积流是不稳定的，在致密物波的上游区域形成弓形激波。吸积气体将正负号的角动量传递到致密物体上。正因为如此，紧凑的物体可能会经历零星的上下自旋。我们称这种现象为触发器不稳定性，如果这种不稳定性发生在自然界中， ...更多信息解释观察结果。然而，由于计算是二维的，不稳定性可能仅仅是由于限制的伪影。为了观察这种现象是否发生在三维情况下，我们与马克斯-普朗克研究所的Anzer和Borner，以色列的Garching和Livio（现在位于巴尔的摩）进行了联合研究。对于吸积盘，我们进行了二维数值模拟，发现在伴星星星的潮汐力作用下，形成了螺旋激波。气体在撞击激波时会失去角动量，并在致密物体上吸积。由于计算的二维性质，这种现象也可能是人为的。日本东北大学的泽田和本作者对多变气体进行了三维数值模拟，发现形成了螺旋激波。另一方面，计算流体动力学研究所的Nagasawa和本文作者进行的三维SPH计算没有显示出明显的螺旋激波。这种差异应在未来的研究中澄清。塔塔研究所的Chakrabarti和本文作者研究了二维流动的时间变化，并将结果应用于SS 433。我们发现计算结果与观测值吻合得很好。少