Abstract:
Clouds play a major role in climate change, and the ability to simulate moist convection patterns is crictical for prediction of tropical weather and climate. Cumulus clouds
in particular can play a significant role in transportig heat across the whole extent of the
atmosphere. Recent laboratory experiments (Narasimha et al. (2011) have successfully
reproduced a variety of naturally occurring clouds, and suggest that the transient diabatic
plume, subjected to off-source diabatic heating is the appropriate cumulus flow model. In
the present work we report the first direct numerical simulation of a transient diabatic
plume as a fluid-dynamical model for understanding cumulus flows.
The simulation solves the 3D Navier-Stokes-Boussinesq equuations for an axisymmetric transient diabatic plume. The equations were solved using a fractional step method
within the finite volume frame work. The solver developed has been validated against
three bechmark cases - (i) lid driven cavity flow; (ii) Rayleigh-Benard convection and (iii)
Turbulent-jet simulations. The visualisations of the cloud flow were carried out using a
coarse grid of around 4 million grid points, The final simulation was performed using 128
million grid points at a Reynolds number of 2000. The computations were carried out in
the ICE cluster housed at CSIR Fourth Paradigm Institute, Bangalore.
