Buoyancy-Driven Vertically Rising Turbulent Plumes of Light Gases in a Quiescent Atmosphere

초록

Modeling thermophysical properties of leaked flammable gas is of paramount importance to perform risk analysis of petrochemical plants. Once a light flammable gas is leaked and rises vertically from a damaged pipe, both the imparted momentum flux and buoyancy drive upward the leaked gas that is also decelerated by turbulent eddy viscosity and simultaneously mixes with surrounding air being diluted by it. Naturally, this accident scenario would pose a threat of subsequent fire or explosion. In this study, velocity and fuel concentrations of such axisymmetric gas plumes are modelled in the framework of the free turbulent boundary layer theory based on the semi-empirical Prandtl's mixing length theory in a non-burning case. The longitudinal velocity (u), fuel (cf) and air (ca) concentrations in vertical axisymmetric plumes of methane and hydrogen (the two light gases with different gas-to-air density ratio phi = rho g/rho a) were found for the Froude (Fr) in the 10 <= Fr <= 104 range. The modeling results offered the overall shapes of the leaked plumes and the distributions of u, cf and ca in the vertical and radial directions. The modeling results may be useful for risk analysis in the aforementioned accident scenarios in petrochemical plants.

키워드