Britter and McQuaid (B&M) 1988 workbook nomograms for dense gas modeling applied to the Jack Rabbit II chlorine release trials

The Britter and McQuaid (B&M) 1988 Workbook for Dense Gas Modeling uses principles of basic physics and thermodynamics to develop simplified nomograms for calculating dense gas dispersion, involving dimensionless combinations of the fundamental variables and parameters. There is one nomogram for instantaneous releases, and another for continuous releases. The B&M nomograms were applied to the three Jack Rabbit II (JR II) chlorine release trials being used for the multi-model comparison described in other papers in this special issue. The intent was to use the B&M model as a baseline against which other, more sophisticated models, could be compared. In any model applied to the JR II trials, it is important to properly initialize the cloud characteristics (geometry, density, etc.). The B&M handbook has a simple basic thermodynamics method to calculate the initial size and density of a cloud released as a two-phase pure mixture. It is shown that the B&M nomograms' predictions of arc maximum concentration (arc max C) for JR II trials 1, 6, and 7 have skill about in the middle of the group of 17 models that are being compared. The B&M predictions are relatively unbiased for Trials 6 and 7 (which has the largest arc max C), but overpredict by a factor of 2 or 3 for Trial 1. It is concluded that the B&M nomograms are conservative and are adequate for first-cut estimates of maximum concentrations following large scale dense gas releases.