On the Hydrodynamic Interaction of Shock Waves with Interstellar Clouds. II. The Effect of Smooth Cloud Boundaries on Cloud Destruction and Cloud Turbulence

By F. Nakamura, C. McKee, Richard Klein, R. Fisher. 2005

139 citations recorded by the source corpus.

The effect of smooth cloud boundaries on the interaction of steady planar shock waves with interstellar clouds is studied using a local adaptive mesh refinement technique with an axisymmetric Godunov hydrodynamic scheme. A three-dimensional calculation is also done to confirm the two-dimensional results. We find that smooth cloud boundaries significantly affect cloud morphology and retard cloud destruction. After shock passage, a sharp density jump forms due to velocity gradients generated in the smooth cloud boundary. We refer to this density jump as a "slip surface" because the velocity is sheared parallel to its surface. The formation of a slip surface leads to complete cloud destruction because of the Kelvin-Helmholtz and Rayleigh-Taylor instabilities. We construct analytic models of cloud drag and vorticity generation that compare well with the numerical results. Small shreds formed by the instabilities have significant velocity dispersions of 10%-20% of the ambient shock velocity. They could be related to the small cold H I clouds recently observed by Stanimirović & Heiles. The dependence of the velocity dispersion on region size, the so-called line width-size relation, is found to be time-dependent. In the early stages, the line width-size relation is more or less flat because of the significant small-scale fluctuations generated by the Kelvin-Helmholtz instability. In the later stages, the small-scale fluctuations tend to damp, leading to a line width that increases with size. The possibility of gravitational instability triggered by shock compression is discussed. We show that gravitational collapse can be induced in an initially uniform cloud by a radiative shock (γ < 4/3) only if it is not too strong and nonthermal motions are weak.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/c6c3e89dc2302d9986214be492dd922856985538

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Citations in the corpus

The Global Evolution of Giant Molecular Clouds. I. Model Formulation and Quasi-Equilibrium Behavior (2006, unknown): “This creates an “impedance mismatch” that makes it difficult to drive turbulence into the GMCs (Nakamura et al. 2006).”
Bimodal gas accretion in the Horizon–MareNostrum galaxy formation simulation (2008, background): “However, this would depend on the position of the clumps with respect to the jet origin and the violence of the shock, and for instance, with a Mach number ≈ 10 and density contrast ≈ 10, Nakamura et al. (2006) do indeed predict cloud destruction.”
Cool outflows in galaxies and their implications (2020, background): “When the flow encounters the cloud, it develops a shock that compresses it and starts to ablate and shred it on a “cloud crushing” timescale, tcc, equal to the ratio of the ratio of the time for the hot flow to travel the radius of the cloud multiplied by χ1/2 (Klein et al. 1994).”
Quasar feedback: more bang for your buck (2009, background): “…velocities of the cloud, then the cloud will be stretched and ‘shredded’ by a combination of Rayleigh–Taylor and Kelvin–Helmholtz instabilities on a time-scale approximately a few tcc (see e.g. Klein et al. 1994; Xu & Stone 1995; Fragile et al. 2004; Orlando et al. 2005; Nakamura et al. 2006).”
The growth and entrainment of cold gas in a hot wind (2018, background): “In fact, Klein et al. (1994) and Nakamura et al. (2006) suggest rcl/dcell & 100 are necessary (in 2D), but recent work finds that even for rcl/dcell > 1000 the solution is not converged (Yirak et al. 2010) in terms of, e.g., the shock structure.”
A computational parameter study for the three-dimensional shock–bubble interaction (2007, methodology): “First, the extensive database of twodimensional simulations for the shock–bubble interaction (see Picone & Boris 1988; Klein et al. 1994; Zabusky & Zeng 1998; Marquina & Mulet 2003; Giordano & Burtschell 2006) is extended further, here, to three spatial dimensions.”
MOMENTUM INJECTION BY SUPERNOVAE IN THE INTERSTELLAR MEDIUM (2014, background): “…have focused on the detailed evolution and fate of individual shocked clouds (e.g., Klein et al. 1994; Mac Low et al. 1994; Fragile et al. 2005; Nakamura et al. 2006; Orlando et al. 2008; Shin et al. 2008; Johansson & Ziegler 2013) rather than SNR evolution as a whole within the cloudy ISM.”