Study On The Mechanism Of Gas Migration And Diffusion In Horizontal Helical Aerated Water Flow

At present,the ecological environment of water conservancy projects is becoming more and more important.The influence of supersaturation of total dissolved gas on ecology caused by aerated flow has also become one of the key problems in the development of water resources and the sustainable development of water ecological environment.Vortex cores exist in the swirling area of horizontal spiral flow,and gas accumulate and coalesce towards the vortex cores,forming spiral flow in the gas zone,which increases the concentration of aerated gas in the water body.Therefore,studying the migration and diffusion law of horizontal to spiral flow gas is a necessary condition to reduce the concentration of total dissolved gas in water body,protect river water ecology and other issues,and formulate operation control strategies.The method of combining physical model test and theoretical analysis is used to analyze the flow state of the horizontal spiral flow,the numerical simulation was used to simulate the spiral flow field,the water flow structure is partitioned,and the gas flow analysis was used to analyze each area without considering gas exchange.Gas movement,comparative analysis of the experimental values of the measured aeration concentration in each area,revealing the mechanism of horizontal spiral gas migration and diffusion,and the horizontal spiral aeration water flow gas movement law.The conclusions are as follows:(1)The transverse velocity of horizontal spiral flow is much faster than the longitudinal velocity.The velocity value of measuring points affected by spiral flow in gas zone fluctuates along the path,while the flow velocity of other measuring points increases along the path.The flow velocity in the wall-attached flow area is the fastest.(2)The law of gas movement in the flow structure areaThe gases in all districts of the water diffuse to the water surface.The gas in the gas entrainment area migrates to the bottom of the water flow,and the air intake in the gas entrainment area is positively correlated with the water flow velocity.The gas in the swirling and rolling area of the water flow accumulates and coalesces towards the vortex core to form a spiral flow in the gas zone.The gas in the wall-attached flow area and backwater reflux area migrates with the flow direction.(3)Gas exchange in flow structure areaThe gas in the gas entrainment area migrates to the water flow swirling and rolling area and the wall-attached flow area.The gas in the rolling area of the water flow migrates and diffuses to the backwater reflux area.The gas in the wall-attached flow area migrates to the backwater reflux area and diffuses to the gas entrainment area and the water flow swirling area at the same time.The gas in backwater reflux zone migrates to water flow rolling zone and gas entrainment zone.