雪の水力輸送に関する研究-4-雪水二相流の管内流れの観察

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The flow of snow/water mixtures in straight pipes of circular cross section (inner diameters <I>D</I>=40 mm and 77 mm) was observed in the range of the velocity of 0.5-1.9 m/s and the snow fraction of 3-30%. The samples were granulated snow and fresh snow. The flow pattern of a snow/water mixture was found to be classified into four types : 1) cluster flow, 2) flow with snow clusters in a homogeneous snow/water mixture, 3) homogeneous flow and 4) cylindrical flow.<BR>The cluster flow, shown at low values of velocity and snow fraction, and the cylindrical flow at high snow fraction were characteristic patterns for a snow/water mixture. In the horizontal pipe the snow clusters were slightly longer in the axial direction than in the vertical pipes and moved near the upper wall of the pipe. However, for the cylindrical flow or the homogeneous flow, little difference in flow pattern between horizontal and vertical pipes could be discerned.<BR>Since fresh snow was slightly more difficult to mix with water than granulated snow, the cylindrical flow was attained at lower snow fraction and the homogeneous flow was not observed for fresh snow. Generally speaking, the inclination of the pipe and the properties of snow had only a slight influence on the flow, and the outline of the flow pattern of snow/water mixture in a pipe was shown to be decided by the snow fraction and the Froude number.