linear artificial viscosity. The energy changes in the cloud and background were found to differ among the models by no more than 10%. We therefore conclude that the form of the artificial viscosity does not dominate our results. The lack of sensitivity is most likely to to the absence of strong shocks in the models.

The models are run with reflecting boundary conditions on all sides. This choice of boundaries serves to isolate the system, eliminating potential ambiguities in the interpretation of the energies of the two components.

Results of the Numerical Simulations
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Model 1: Transsonic sedimentation of adiabatic clouds
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In Model 1, we adopt a polytropic equation of state for both the cloud and background. For the values of $D_\rho$, $S$, and $g$ of the model, $V_t \sim C_h$ during the descent.

In Figure \[fig:mod1rho\], we show the evolution of the density of Model 1. The model is shown from time 0 to 16, at intervals of 2 (the horizontal sound crossing time in the RHG $\Delta x/C_h=1.5$). The WFC rapidly accelerates to a speed $\vert V_y\vert \approx C_h$, at which point the increasing drag causes it to achieve a terminal speed. The deceleration of the cloud 