Author(s): Sean Mulligan, Eoghan Clifford
Linked Author(s): Sean Mulligan
Keywords: Vortex, drop shaft, free-surface, jet, dissipation.
Abstract: Vortex flow drop structures are commonly employed in sewer systems and large hydropower schemes to convey water to lower levels and dissipate energy safely. The free-surface jet that forms just downstream of the intake plays a critical role in the performance of the device and knowledge of its characteristics are of importance to safe and optimum engineering design. In this study, principles of vortex flow and the critical cross-section of the free-surface vortex are used to evaluate the characteristics of the free-surface jet. A physical model of a subcritical vortex chamber was analysed and the nature of the emanating jet was observed for various approach flow conditions. The reduced scale vortex chamber was also simulated using a three-dimensional numerical model employing two different turbulence models: the shear stress transport with curvature correction and the baseline Reynolds stress model. The results indicated that the jet angle is largely independent of the approach flow depth for the investigated vortex chamber and test cases. The numerical models provide an excellent simulation of the free-surface jet position, shape and initial spray angle in addition to the bulk velocity throughout the jet. However, the analytical model developed was shown to produce errors in the region of 24 to 50 % which was pondered to be as a result of neglecting the gravitational constant at low pressures
Year: 2017