Experimental Observations of Entrainment Rates in Dense Gas Dispersion Tests

It is shown how the local entrainment rate and the local Richardson number used in box models of dense gas cloud dispersion can be found from experimental measurements of wind tunnel simulations. These calculated values can then be used to check the common hypothesis of box and other models that the dimensionless entrainment is a universal function of the local Richardson number. It is found that some experiments do not conform to this hypothesis, most likely because of the vigorous initial mixing of the cloud. An empirical mixing law is proposed for this early stage which does not violate energy conservation.