Bondi-Hoyle-Lyttleton accretion flow revisited: Numerical simulation of unstable flow

The Bondi-Hoyle-Lyttleton accretion flow of cold gas is known to be unconditionally unstable. We investigate the instability of the Bondi-Hoyle-Lyttleton accretion flow numerically. We confirm previous studies that find that the velocity and the line mass density on the accretion line fluctuate widely both spatially and temporally. The mechanism underlying this fluctuation can be described in terms of the traffic-jam model. We calculate the time-averaged accretion radius to be ra=0.89×2GM∕v∞2. In our previous paper, we investigated time-steady equations and concluded that ra=0.90×2GM∕v∞2.