Wind Tunnel Experiment And Numerical Simulation Of Dense Gas Leakage In Plateau Mountainous City At Complex Terrain

Dense gas leakage will cause the huge destroy as result of the crowded population and building in the city. Great atention has been paid to the hazard of dense gas dispersion, and the numerical simulation and risk analysis of the dense gas dispersion in recent year, but the wind tunnel experiment and numerical simulation of dense gas leakage aren't done in plateau mountainous city at complex terrain. It is imperative that the research is done because of the big surface roughness, the low air pressure in plateau mountainous city, and unique dispersion behavior.During research of regional wind field, the pilot balloon was used to determine the wind velocity at different height, and it is 0.518,0.594,0.615 for the exponent of wind profile respectively at the unstable, neutral and stable condition as a research object taking a plateau mountainous city Gejiu Yunnan. The high wind profile exponent is found in the plateau mountainous city. A model of downtown and suburb area with a proportion of 1:1000 in Gejiu city was made. Onsite data of wind profile was used to regulate the wind profile of wind tunnel, and to identify the characteristics of wind profile in Gejiu city as relative deviation of less than 3.4%. Velocity distributor, rough components and wind poles situated in the wind tunnel can be regulated to simulate the wind field mentioned above.It is found that the wind profile can become the object rapidly by adjusting the height and density of the pole of lcmXlcm and 2cmX2cm cross section. Determination spots were located to identify the variation of wind velocity in different terrain. Due to the complex terrain and built-up urban in Gejiu city, there were some differences for wind velocity at the same height and exponent of wind profile at the different site. Characteristic of wind of the central axis was used to evaluate the influence of mountain-crossing wind and terrain block on the wind field. The rapid analysis method of CFC12 with gas chromatograph is developed, and the quantitative results as the peak height is better than that of the peak area. The characteristic features of the dense gas plume dispersion in plateau mountainous city based on the wind tunnel experiment shows that there is the dangerous wind velocity, that is the concentration of dense gas is maximal when viscous coefficient is maximal, and it is 0.121m/s to be calculated with fitting of polynomial. The dispersion process of the dense gas is shown by the smog apparatus of wind tunnel made of smog machine and buffer box etc. The variation of concentration with the downwind distance is slow after downwind 0.5m. The variation of concentration with the transverse distance is skew distribution. The concentration is reduced with the increase at the same situ of downwind, the concentration over the 0.02m varies slowly.The fluid dynamic models based on Computational Fluid Dynamics (CFD) can not only be applied to reflect the physical phenomenon in the air turbulent flow with dense gases, but also is possible to be used to simulate the dense gas dispersion where topography change or obstacles exists. In this paper, the CFD models are employed to investigate the regular patern of dense gas dispersion. A set of three-dimensional, time-dependent conservation equations is developed. Three kinds of turbulence models are introduced in this paper. By comparison, the Realizable k-εtwo-equation turbulence model with the modification of buoyancy effect is used in the simulation. The conservation equations are discretized in terms of the finite volume method in space and are fully implicit in time.They are solved by means of a method,based on the SIMPLE algorithm.The resulting linear equations are solved iteratively. From this validation it can be concluded that the models and algorithm used in this paper are cceptable.The influence of air temperature and air pressure on the process of dense gas dispersion is analyzed, it was shown that the concentration of dense gas at the normal air pressure is less 6.2%-24.7%, average 18.6% than that of 810hPa, and the concentration of dense gas at 0℃is less 6.9%～8.9%, average 8.2% than that of 23.5℃under the same mass flow rate etc.