The turbulent destruction of clouds - III. Three-dimensional adiabatic shock-cloud simulations

We present 3D hydrodynamic simulations of the adiabatic interaction of a shock with a dense, spherical cloud. We compare how the nature of the interaction changes with the Mach number of the shock, M, and the density contrast of the cloud, χ. We examine the differences with 2D axisymmetric calculations, perform detailed resolution tests, and compare ‘inviscid’ results to those obtained with the inclusion of a k-ϵ subgrid turbulence model. Resolutions of 32–64 cells per cloud radius are the minimum necessary to capture the dominant dynamical processes in 3D simulations, while the 3D inviscid and k-ϵ simulations typically show very good agreement. Clouds accelerate and mix up to five times faster when they are poorly resolved. The interaction proceeds very similarly in 2D and 3D – although non-azimuthal modes lead to different behaviour, there is very little effect on key global quantities such as the lifetime of the cloud and its acceleration. In particular, we do not find significant differences in the hollowing or ‘voiding’ of the cloud between 2D and 3D simulations with M = 10 and χ = 10, which contradicts previous work in the literature.