Three-Dimensional Turbulence Numerical Simulation of Flow in a Stepped Dropshaft

Abstract

The dropshaft structure is usually applied in an urban drainage system to connect the shallow pipe network and the deep tunnel. By using the renormalization group (RNG) k~ε turbulence model with a volume of fluid method, the flow pattern and the maximum relative water depth over a stepped dropshaft with a different central angle of step were numerically investigated. The calculated results suggested that the flow in the stepped dropshaft was highly turbulent and characterized by deflection during the jet caused by the curvature of the sidewall. According to the pressure distribution on the horizontal step and the flow pattern above the step, the flow field was partitioned into the recirculating region, the wall-impinging region and the mixing region. In addition, with the increase in the central angle of step, the scope of the wall-impinging region and the mixing region increased and the scope of the recirculating region remained nearly unchanged. The maximum water depth increased with the increase in discharge. In the present work we have shown that, as the value of the central angle of step increased, the maximum water depth decreased initially and increased subsequently.

Three-Dimensional Flow of a Vortex Drop Shaft Spillway with an Elliptical Tangential Inlet

“…Although the k-ε turbulent models have been widely applied to flow simulations because of the fine convergence and computational efficiency [37][38][39], the RNG k-ε turbulence model proposed by Yakhot and Orzag, by providing an additional coefficient correcting the turbulent viscosity and taking into account the average rotational motion, can effectively process the strong swirling flow or curved wall jet under high Reynolds number [40]. Furthermore, regarding to previous research [2,24,41] were found that the RNG k-ε turbulence model can give the best prediction of the jet flow in such shaft spillway.…”

The effect of air velocity on slugs in a confined channel

“…The RNG model is recommended for flows involving recirculation and interface curvature [45]- [49]. The turbulent kinetic energy and the dissipation rate Equations for this model can be written in the following way [50]:…”

Hydraulic performance of helical-step dropshaft

“…Despite some favor by engineers, few achievements about the hydraulic characteristics about the helical-step dropshaft were reported. Similar dropshafts with large-angle steps or blade-shaped steps were tested by means of experimental and numerical methods, respectively, and these case studies provided some useful information about the flow characteristics in the dropshafts (Qi et al 2018;Wu et al 2018;Sun et al 2020). Attention was also paid to the standing waves formed at the inlet of such dropshafts in the literature (Wu et al 2017).…”