contrast. Prior to breakup, the downward motion of the cloud is more rapid than the value of $V_t$ found for Model 1. The differences are due to the modification in the drag caused by the leading shock in Model 2.

The energy evolution is shown in Figure \[fig:mod2en\]. The initial kinetic energy of the cloud, $E_{K,0}=6.3$, is almost entirely dissipated by $t=10$. Over the same time interval, the cloud is also able to penetrate to a greater depth than the cloud in Model 1, increasing the release of gravitational energy relative to that model. Together, these effects lead to a gain of internal energy for the background gas by a approximately a factor of two larger than seen in Model 1.

However, the depth at which the cloud breaks up is similar in the two models. As in Model 1, the break up occurs when the cloud encounters a column of RHG that is comparable in mass to that of the cloud. Thereafter, the fragments’ rate of sedimentation is significantly reduced in accordance with Equation (\[eq:vterm\]). The asymptotic rate of RHG’s internal energy increase in Model 2 is comparable to that in Model 1.

Model 3: Efficient energy loss within 