An Optimal Design of the Inlet and Outlet Obstacles at USBR II ‎Stilling Basin

Abstract

Hydraulic jump is one of the rapidly varied flows that different elements can be employed to control it in stilling basins. The purpose of this study is optimal design of obstacles at USBR II stilling basin of Nazloochay dam model. For this purpose, the obstacles at the end chute with thicknesses and heights of 0.5, 1, 1.5 and 2 m and 2, 3 and 4 steps at the end USBR II stilling basin have been considered. Then for the most optimal state, the pressure, water surface profile, turbulent kinetic energy, and turbulent kinetic energy dissipation investigated for discharging 830 m 3 /s by using K-ε and RNG turbulence model and VOF method. According to changes in water height, obstacles selected with heights of 1 and 1.5 equal of standard state at the end chute and 3 steps at the end stilling basin. The comparison of numerical and experimental values of water surface and pressure profiles showed that numerical model has good agreement with experimental results. Also, hydraulic jump on adverse steps at the end stilling basin increase energy dissipation and stability of hydraulic jump. In addition, numerical model can be used to model stilling basins and measuring non-measurable parameters in laboratory.

Numerical Investigation of Critical Hydraulic Parameters Using FLOW-3D: A Case Study of Taunsa Barrage, Pakistan

“…However, as compared with lower tailwater levels, the values for TKEs in 129.40 m tailwater were found to be lower and the TKEs levelled off earlier within and after the HJ. In the HJ regions, following the similar trends for the 129.10 and 129.40 m tailwater levels, the TKEs in the 129.70, 129.99, and 130.30 m tailwater levels reached 3.20, 3.15, and 2.90 m 2/ s 2 , respectively, and their values decreased after the HJ, as illustrated in Figure 15c-e. Additionally, the results for the TKEs showed a trend that was noted in the numerical studies (Nikmehr and Aminpour [71]; Soori et al [76]). Figure 16 shows 2D illustrations of turbulent kinetic energies captured using RNG-K-ε at five different tailwater levels.…”

“…The literature only revealed one study that employed a one-dimensional (1D) HEC-RAS model to investigate the limited hydraulic parameters downstream of the studied barrage [36]. Therefore, the present FLOW-3D model results are compared with 1D and the relevant studies from the literature, i.e., Bayon-Barrachina and Lope-Jimenez [4], Chaudhry [36], Ead and Rajaratnam [11][12][13], Nikmehr and Aminpour [71], Soori et al [76], and Kucukali and Chanson [94]. After comparing with the results of the free surface profiles of HJs at the studied tailwater levels, it is revealed that the previously used 1D model underestimates the locations of the HJs; for which the errors reached 8%.…”

“…Based on the published data from similar studies, the present studies implemented the RNG K-ε turbulence model within the stilling basin of the studied barrage. In the RNG K-ε turbulence model [73][74][75][76][77][78][79][80][81], Equations ( 6) and ( 7) were applied to model the turbulent kinetic energy (k) and its dissipation (ε), respectively.…”

Assessment of the Performance of a Modified USBR Type II Stilling Basin by a Validated CFD Model

“…These authors found that the original design dimensions of the chute blocks led to the optimal performance of the basin, since they achieved better submergences and higher dissipation efficiency. Soori et al (2017) also tested different sizes for the chute blocks in a USBR Type-II stilling basin, changing the end sill for a series of steps too. The results presented by these authors also point out to an optimal dimension of the chute blocks in line with the original design.…”