Experimental Study On Characteristics Of Jet In Bend Flow

The sewage is always discharged into the water through orifice jet,and the hydrodynamic characteristic of jet flow is relevant to the dynamic characteristic of environmental water.The bend flow has a complicated three-dimensional character,the characteristic of jet flow in bend flow is more complicated when compared with the one in straight flow.Since the majority of natural rivers are meandering river,the study on the characteristic of jet flow in bend flow has an important value of both theoretical and practical.In this paper,the distribution of flow velocity and the extending width of the single hole jet are measured by the Vectrino NDV and ADCP.Based on the analysis of the jet characteristics of different velocity ratio and different jet orifice's position,this paper draws some conclusions:1.By analyzing the vertical velocity distribution pattern,we found out that the initial length of the jet flow is linearly dependent on the initial velocity of the jet flow,and obtained a empirical formula.The position of the maximum vertical velocity in cross section of jet flow is moving toward the concave bank gradually.The attenuation law of vertical velocity on jet stream line is related to the position of jet orifice and the velocity ratio.The attenuation of velocity is quicker near the convex bank in the same section;the attenuation of velocity is quicker as the velocity ratio is smaller at the same position.And we obtained the empirical formula of jet stream line as the jet orifice in the position of the central line in 90°cross-section.2.The expansion of half width of the jet flow increases gradually along the direction of flow.The expansion of half width of the jet flow upward the path line is exceed the expansion beneath the path line;the expansion of half width of the jet flow on the concave side of the path line is exceed the expansion on the convex side of the path line;and all of them have connection with the velocity ratio and the position of the jet orifice.3.The extension of full width increases with the increase of the velocity ratio,and we obtained a empirical formula about the jet's vertical and horizontal extension of full width as the jet orifice in the position of the central line in the 90° cross-section.The extension of full width appears differences with the change of the jet orifice's position.When the jet orifice is on the convex/concave side of the section,the vertical/horizontal extension of full width is larger than other positions;when the jet orifice is on the 45°/90° section,the vertical/horizontal extension of full width is larger than other sections.