Some Physical Processes Involved in the Dispersion of Dense Gases

In this paper we attempt to provide a theoretical framework for the formulation of mathematical models of dense gas dispersion in the atmosphere. Our approach is to divide the evolution of a released dense gas cloud into four phases, during each of which different physical processes governing the behaviour of the cloud are most important. These processes are identified and recent attempts to uhderstand them are discussed. We also give scaling arguments for the order and duration of the different phases as functions of the atmospheric and release conditions.