Wind tunnel investigation of drifting snow development in a boundary layer: Fid-Bau Portal

Wind tunnel investigation of drifting snow development in a boundary layer

Okaze, Tsubasa / Mochida, Akashi / Tominaga, Yoshihide / Nemoto, Masaki / Sato, Takeshi / Sasaki, Yasutomo / Ichinohe, Kazusato

Abstract

Abstract Wind tunnel measurements over loose snow surface were carried out to experimentally investigate the characteristics of drifting snow phenomena in a non-equilibrium boundary layer and to obtain data for examining the numerical model of snow transport coupled with the computational fluid dynamics (CFD). In this experiment, the spatial distributions of the mass flux of drifting snow, wind velocity, and turbulence statistics were measured simultaneously under several different wind speed conditions. This paper reported that the drifting snow particles reduced the mean wind velocity near the snow surface when saltation occurred. The effective roughness height $z_{0}^{'}$ and the friction velocity 〈u ^⁎〉 estimated from our experimental results were in good agreement with the relation between $z_{0}^{'}$ and 〈u ^⁎〉 obtained in previous research. The turbulence energy k increased when saltation occurred because the velocity gradient above the saltation layer increased due to the effect of snow particle near the surface on flowfield. The streamwise change of the transport rate of drifting snow was also obtained by integrating the vertical profile of the mass flux. It indicated that the saltation layer requires several meters to reach equilibrium state. In addition, in the highest wind speed case, the transport rate showed the maximum value before saltation layer reached equilibrium state.

Highlights ► Wind tunnel measurement of drifting snow development was carried out. ► Drifting snow particles reduced mean wind velocity when saltation occurred. ► Saltation layer over loose snow requires several meters to reach equilibrium state. ► Turbulence energy increased due to the increase of velocity gradient above loose snow. ► Transport rate of drifting snow showed the peak before saltation reached equilibrium.