| Research Abstract |
In order to get the basic equations for solid-fluid two phase flow, such as snow drift, powder snow avalanches and turbidity currents, the non-Boussinesq k-ε turbulence nodel, refered to as NBKE model, is proposed. NBKE model is appricable to the flow whose density is considerably heavior than the density of ambient fluid. This model consists of the Reynolds equation, mass conservation equations of fluid and solid particles, the equation of the kinetic energy of turbulence and the equaiton of the viscous dissipation rate of turbulence. This model does not assume the Boussinesq approximation and take into account the effect of density viariation not only in the gravity and pressure terms but also in the other term.
The experiments on the snow drift in the low temerature wind tunnel were carded out, because the snow drift has basically similar characteristics to the powder snow avalanches. This wind tunnel belongs to Shijo Branch of Snow and Ice Studies, National Research Institute for Ea
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rth Science and Disaster Prevention, Science and Technology Agency. The snow drifts were generated using this apparatus the vertical profiles of wind speed and flux of snow particles for non-equillibrium state. The wind speed was measured by the hot-wire anemometer and the flux of snow particles was meausred by the snow particle counter (SPC).
The numerical anslysis of NBKE model were carried out using the given conditions for the wind tunnel experiment. The numerical results explains well the experimental results on wind speed profiles and the snow particle mass flux profiles for the measuring sections. The non-equilibrium snow drift differed from the equilibrium one, especially the profiles of snow flux. These flow is considered to be similar to the transition from snow drift to powder snow avalanches.
In order to evaluate the simulation model of powder snow avalanches, the experiment on the inclined suspension thermals of conservatice cases or non-conservative cases were carried out. In case of conservative thermals, the saline water was used. In the case of non-conservative thermals, the mixture of the barium salfate particles and water was used. The flow characteristics such as the variation of the maximum thickness and travel speed were obtained from video-taped record. In addition, the depositional amount of Barium powder and their size distributions are also measured. Using these experimental data, the complex properties of non-conservative inclined thermals were clarified.
The generation and flow dynamics of powder snow avalanches are examined by the experiment and numerical analysis based on the fluid dynamical view points and the basic knowledge on these mechanism are clarified. Less
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