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明渠水流自然掺气以后呈水气混合的两相流,其密度、粘性以及流场内和壁面上的剪力都小于相应条件下水流未掺气(虚拟清水流动)时的数值。因此,掺气水流中的水相速度将大于未掺气时的清水速度。本文分析了作者及L.G.Straub在实验室内测得的两批资料,最后给出:明渠掺气水流可比拟为分层结构;其减阻效应与水相连续的近壁层平均含水度_b明显有关;其增速效应则受全断面平均含水度及渠道底坡α的制约。
The two-phase flow, which is mixed with water and gas after natural aeration in the open channel, is less dense and viscous, and the shear forces in the flow field and on the wall are less than those when the water flow is not aerated (virtual water flow) under the corresponding conditions. As a result, the water phase velocity in the aerated water flow will be greater than the clear water velocity at the time of aeration. In this paper, we analyze two batches of data measured by the author and LGStraub in the laboratory. Finally, we conclude that the open channel aerated flow can be compared to a layered structure, and the drag reduction effect is similar to the water-borne continuous near wall average moisture content Obviously related to its growth rate effect is affected by the average cross-sectional water content and channel slope α constraints.