Laboratory simulation of the rise of buoyant thermals created by open detonation

Abstract

Laboratory experiments were conducted in a water tank to investigate the rise through the atmosphere of thermals generated by the detonation of surplus military munitions. The fall of a dense volume of fluid through the water in the tank follows the same governing equations as the rise of a buoyant volume of gas in the atmosphere. By filling the tank with a layer of water and a layer of salt water, an elevated step change in density was obtained, simulating a temperature inversion or jump in the atmosphere. The growth of the linear dimensions of the thermal and its volume were determined and used in the development of a criterion for predicting when a thermal will fully penetrate the inversion. Replacing the second layer of fluid with water of gradually increasing salinity, an elevated constant density gradient was obtained. In these cases, the maximum penetration distance of the thermal was observed and the equilibrium position and vertical spread were determined experimentally.These observations and the empirical relationships determined from them should prove useful in the development and evaluation of air pollution dispersion models for predicting the atmospheric transport and diffusion of material released during such detonations.