Numerical Investigation of the Effect of CEDEX Profile on the Hydraulic Parameters in the Stepped Spillway and the Perfo
- PDF / 1,289,214 Bytes
- 8 Pages / 595.276 x 790.866 pts Page_size
- 83 Downloads / 204 Views
RESEARCH PAPER
Numerical Investigation of the Effect of CEDEX Profile on the Hydraulic Parameters in the Stepped Spillway and the Performance of This Profile in Various Chute Slopes Kazem Dalili Khanghah1 · M. R. Kavianpour1 Received: 3 October 2018 / Accepted: 22 October 2019 © Shiraz University 2019
Abstract An important part in designing stepped spillways is making the spillway in order to direct the flow appropriately on the first step. In low discharges, the water flow moves over the spillway and arrives at the first step, and if the first step is high enough, the flow may leave the first step horizontally, skip some steps and land as a free jet of water on the lower steps, which might cause some damages to the structure. One of the solutions to this problem is to use CEDEX profile, transition steps between the ogee crest and the stepped chute. The present research carries out a numerical study of the effects of CEDEX profile on various hydraulic parameters and also the effects of the chute slope on the performance of this profile in preventing the flow jump. For this purpose, four models were created with different geometries and were studied in various discharges with FLOW-3D software. The results show that deploying CEDEX profile in the initial parts of the spillway leads to lower velocity and less risk of cavitation. Also, the results illustrate that CEDEX profile can shift the inception point of aeration to downstream. Furthermore, findings show that CEDEX profile, in the slope of less than 50°, can prevent flow jump in the first step. In steeper slopes, however, it fails to achieve the optimal performance. Keywords Stepped spillways · CEDEX profile · FLOW-3D · Flow jet · Chute slope
1 Introduction One of the main characteristics of stepped spillways is the high turbulence and air entrainment of their flows. Chamani and Rajaratnam (1999) and Baylar et al. (2006) studied the skimming flow and concluded that the air and oxygen that enter the flow in stepped spillways are more than the air entering smooth spillways. Stepped spillways are thought to be less prone to cavitation damage than smooth spillways because of air presence (Frizell et al. 2013). Pfister et al. (2006) realized that the cavitation index in specific discharges of larger than 30 cubic meters per second divided by width is less than 0.9. Amador et al. (2009) and Frizell et al. (2013) claimed that cavitation occurs precisely on the downstream of the edge of the steps close to their vertical side, where the pressure is at its lowest. * Kazem Dalili Khanghah [email protected] 1
Faculty of Civil Engineering, K.N. Toosi University of Technology, Tehran, Iran
Sorensen (1985) compared the point of inception and the flow depth in stepped and smooth spillways and claimed that aeration of the free surface of the flow in stepped spillways occurs at a more upstream point than smooth spillways and that boundary layer growth takes place better in stepped spillways. Chanson (1994), Meireles and Matos (2009) and Hunt and Kadavy (2013) offere
Data Loading...
