Study of inception point, void fraction and pressure over pooled stepped spillways using Flow-3D

Abstract

Purpose -While many stepped spillways geometry design guidelines were developed for flat steps, designing pooled steps might be an appropriate alternative to spillways working more efficiency. This paper aims to deal with the inception point of air-entrainment and void fraction in the different height of the pools. Following that, pressure distribution was evaluated in aerated and non-aerated regions under the effect of different heights of the pools and slopes through the use of the FLOW-3D software. Comparison of obtained numerical results with experimental ones was in good agreement for all discharges used in this study. Pools height had the insignificant effect on the inception point location. The value of void fraction was more affected in lower discharges in comparison with higher ones. Negative pressure was not seen over the crest of spillway (non-aerated region), and the maximum pressure values were obtained for pools with 15 cm height along the crest in each discharge. In all slopes, negative pressure was not formed near the step bed in the pooled and flat stepped spillways. However, negative pressure was formed in more area near the vertical face in the flat stepped spillway compared with the pooled stepped spillway which increases the probability of cavitation phenomenon in the flat stepped chute.Design/methodology/approach -A pooled stepped spillway was used in order to evaluate pressure, void fraction, and inception point. Also, different height of the pools was used. Numerical simulation of this study was fulfilled through Flow-3D software. The obtained results indicated that pools can affect two-phase flow characteristics including pressure, void fraction and inception point.Findings -Over the crest, negative pressure was not seen. Pressure values were different for all used heights and the maximum ones obtained for 15 cm height. Also, pooled stepped played a more effective role in reducing the negative pressure points compared with flat cases. Inception point location was more affected in nappe and transition flow regimes in comparison with skimming flow regime particularly for 9 and 15 cm heights.Originality/value -The research results of Felder et al. (2012a) from the University of Queensland were used to numerically simulate the flow over the pooled stepped spillway.

Numerical Simulation of Velocity Field around Two Columns of Tandem Piers of the Longitudinal Bridge

“…With the development of computer science, numerical simulations based on Computational Fluid Dynamics (CFD) codes (e.g., Flow-3D(Three-Dimensional), Fluent) have been wildly used. The simulation results have been proved to be consistent with experimental results [21][22][23][24][25][26][27][28][29][30]. For tandem piers, Palau-Salvador et al [31] conducted numerical simulations around two submerged tandem piers and presented flow streamlines at different planes.…”

Prioritizing Design Parameters for Stepped Chutes and Shear Stress Distribution

“…A comparison of the results reported by Morovati and Eghbalzadeh [31] with Li and Yang [32] indicated that pressure distribution on flat and inclined steps followed a virtually S-shaped distribution. Inception point location was also researched by Munta et al [33], Bombardelli et al [34], and Morovati and Eghbalzadeh [35]. Morovati et al [3] investigated the effects of various configurations of openings on pooled stepped chutes, and they concluded that a staggered configuration of openings improved the chute's efficiency concerning the residual head.…”

Energy Loss in Steep Open Channels with Step-Pools

“…Bombardelli et al [39] compared measured time-averaged velocities for the flows in stepped spillway using k − ε, RNG k − ε turbulent models and found that the results did not significantly vary between the turbulent models. Morovati and Eghbalzadeh [40], Bayon et al [41] and Valero et al [42] used RNG k − ε model and it was found to be better than other models. Abdulla [43] evaluated the performance of different turbulent models (k − ε, RNG k − ε and SST) using ANSYS-CFX for Froude number varying from 1.2 to 2.0 for flows around bridge piers where flow separation was significant.…”