Abstract
The present study examines the configuration of an offset jet issuing into a narrow and deep pool. The standard k-ε model with volume-of-fluid (VOF) method was used to simulate the offset jet for three exit offset ratios (OR = 1, 2 and 3), three expansion ratios (ER = 3, 4 and 4.8), and different jet exits (circular and rectangular). The results clearly show significant effects of the circumference of jet exits (Lexit) in the early region of flow development, and a fitted formula is presented to estimate the length of the potential core zone (LPC). Analysis of the flow field for OR = 1 showed that the decay of cross-sectional streamwise maximum mean velocity (Um) in the transition zone could be fitted by power law with the decay rate n decreased from 1.768 to 1.197 as the ER increased, while the decay of Um for OR = 2 or 3 was observed accurately estimated by linear fit. Analysis of the flow field of circular offset jet showed that Um for OR = 2 decayed fastest due to the fact that the main flow could be spread evenly in floor-normal direction. For circular jets, the offset ratio and expansion ratio do not affect the spread of streamwise velocity in the early region of flow development. It was also observed that the absence of sudden expansion of offset jet is analogous to that of a plane offset jet, and the flow pattern is different.
Highlights
Offset jets are common in drainage systems [1], slot fishways [2], and hydraulics engineering [3].The offset jet is formed when a fluid jet discharges into an ambient medium above the floor and parallel to the axis of the jet exit but which is offset by a certain height
The offset jet flow was widely used as energy dissipation downstream of hydraulic structures—for example, the submerged hydraulic jump at an abrupt drop could be considered as an offset jet flow
This paper addresses the decay of velocity of offset jets in the narrow and deep pool with various offset ratios, expansion ratios and jet exit shapes, through numerical simulations using a 3D
Summary
Offset jets are common in drainage systems [1], slot fishways [2], and hydraulics engineering [3]. Bhuiyan [5] analyzed thethan characteristics of shallow results indicated for an offset height larger the jet thickness, the peak velocity, the flow momentum decay faster in the downstream direction an offset jet and than submerged turbulent plane offset jets The results indicated thickness, the peak velocity, the flow momentum decay faster in the downstream direction the floor-normal location of maximum mean velocity and jet spread to be independent of Reynolds in an offset jet than in a turbulent plane wall jet. The hydraulic properties of submerged offset jets in a narrow and deep pool using a planar particle image velocimetry (PIV) system conducted the experiments to study have not beenThey completely understood, it was widely used asofan energyof dissipator in the velocity. This paper addresses the decay of velocity of offset jets in the narrow and deep pool with various offset ratios, expansion ratios and jet exit shapes, through numerical simulations using a 3D computational fluid dynamics (CFD) model with the k-ε turbulence model coupled with VOF method, which was confirmed perform well in jet flow [10,12,13,14,15,16,17]
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