Fluid Dynamic Problems in Cold Regions

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1. A turbulent separated-and-reattaching flow is one of the most fundamental flows which are associated with the effectiveness of snow fences and shelters, the obstruction of drivers' sight during snow drifting, etc. Two- and three-dimensional separated flows were experimentally studied to obtain the time-mean velocities, turbulence properties, flow unsteadiness due to the shedding of large-scale vortical structure, and means of their manipulation. These results are likely to be similar to those of a wide range of separated-and-reattaching flows.2. An experimental study was made to investigate characteristics of the freezing heat transfer of layered ice-water flow in a circular pipe, in which cooled air and water flow in the same direction. The experiment was performed under a variety of conditions of water discharge, water temperature, tube-wall temperature, air discharge, and water level. Particular attention was focused on photographic visual observation of the developing ice layer … More along the tube wall. It was observed that there were two different regions characterizing the ice formation, one of which was the freeze-off region, and the other was the steady-state region. Conditions for the freezeoff onset were obtained in terms of an empirical formula.3. The formation of ice growth occurring in branched pipes which contained water was made over a range of Reynolds number, and the cooling temperature ratios. From the flow visualization studies, the branched pipe flowing water was first blocked by ice formation ; subsequently the main pipe downstream of the branched portion was frozen off, and eventually the main pipe downstream of the branched portion was blocked by ice formation. This shows that freezing of the remaining water in the branched portion results in the pipe rupture at around the branched portion. The transient behavior of the ice formation was expressed in terms of the pressure loss and Reynolds number for various cooling temperature ratios.4. Flow around a snow shelter consisting of cascade of elliptic wings was numerically studied by solving the Navier-Stokes equations by the use of a body-fitted coordinate to obtain the aerodynamic forces acting on the wing, the velocity distribution, and the effectiveness of blowing off snow on the ground level. Velocity and turbulence measurements were also made in wake of a porous plate to evaluate the extent of detached low-velocity region downstream of the plate. These results gave excellent information on design of effective snow fences and shelters. Less