Hydraulic conveying of snow

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Other Title
  • 雪の水力輸送に関する研究
  • ユキ ノ スイリョク ユソウ ニ カンスル ケンキュウ 8 セツスイ 2ソウリ
  • VIII. Blocking of snow/water mixture flow and criterion of stagnation of snow at pipe orifice
  • 第8報 雪水二相流の閉塞現象と絞りにおける停滞の発生限界

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Abstract

Based on observations of flows, an outline of the blocking phenomenon of snow/water mixture flow in closed channels was given. It was confirmed that a characteristic blocking occurred due to the property of snow in the mixture flow, i.e. a tendency of snow blocks to adhere to each other and to form a densified plug in the channel compressed by the water pressure. Since the blocking was revealed to originate from the stagnation of the snow cluster, the criterion at on orifice in a horizontal pipe was investigated experimentally. With pipe diameter D=47∼90 mm and the areal contraction ratio K=0.068∼0.27, the dependence of the critical flow velocity Vst (below which snow clusters were arrested at the orifice) on D, on K, on snow volume fraction C in discharge, and on the property of snow was made clear as follows.<BR>(1) When C<C*, where C* is 0.15 and 0.12 for granulated snow and fresh snow respectively, Vst is inversely proportional to D and independent of C. When C>C*, snow clusters almost fill the pipe and Vst is inversely proportional to D and proportional to C. While, the influence of K on Vst is not significant over the whole experimental range of C.<BR>(2) Fresn snow is apt to stagnate, and the critical values of DVst with C<C* and DVst/C with C>C* for fresh snow are 1.4 and 2 times the corresponding ones for granulated snow.<BR>(3) Blocking is avoidable by applying the critical values of DVst or DVst/C obtained in this work as the criterion of stagnation.

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