VISUALIZATION STUDIES OF CLOUD-LIKE FLOWS

This paper reports a series of flow visualization studies in which clo ud-like off-source volumetric heating is injected into fully developed turbulent flow, with the objective of simulating the effect of the he at release that accompanies condensation and freezing of water vapour in a cloud. The visualizations provide axial and normal sections of th e flow using laser sheet illumination. special emphasis is placed on a comparison of the results obtained in jets and plumes. Although the r esults are broadly similar in both flows, the plume (which should be c loser to a cloud) shows greater dilution due to entrainment before hea ting,;and stronger effects due to heating. In particular, heating is s hown to arrest the spread of the plume and cause considerable disrupti on of the large eddies in the flow, It is concluded that heat release due to phase change in a cloud has not only thermodynamic but subtle a nd important fluid-dynamical consequences as well.