The effect of flow patterns and energy dissipation over stepped chutes on aeration efficiency

Abstract

Stepped chutes that are commonly used for gabion weirs, river training, irrigation channels, and storm waterways have become popular in recent years mainly due to the intrinsic low-cost and the speed of construction. Stepped chutes are used also for in-stream re-aeration and in water treatment plants to enhance the air-water transfer of atmospheric gases and of volatile organic components. In a stepped chute, the provision of steps can produce significant energy dissipation. This paper seeks the effect of energy dissipation over stepped chutes on aeration efficiency. It is observed from the results that aeration efficiency increases with increasing energyloss ratio. There is higher energy dissipation in nappe flows than skimming flow situations and nappe flow regime lead to greater aeration efficiency than skimming flow regime. Moreover, regression equations are obtained relating aeration efficiency to stepped chute slope and energy-loss ratio. For this aim, genetic expression programming, a recently developed artificial intelligence technique, is used. The model equations obtained have high correlation coefficients and low minimum square error values.

Study of Energy Dissipation of Pooled Stepped Spillways

“…Also a change in the number of steps does not change the flow depth on the spillway crest for similar discharges. According to the equations 10 and 11 and also Baylar et al [28] classification, it could be stated that the flow surface has a series of fluctuations in all three discharges in the stepped spillway with 6 steps, in other words the transition flow regime is present in this state. The transition flow regime is only created in the discharge 0.075 m 3 /s when 8 steps are used.…”

“…They also came to the conclusion that the k-εturbulencemodelhadthemostcapabilityinsimulatingtheflowoversteppedspillwaysincomparisonwiththe other turbulence models. Baylar et al [28] examined energy dissipation and flow pattern on the stepped chutes. They concluded that flow aeration efficiency increased as the energy dissipation increased.…”

Numerical Investigation on the Hydraulic Properties of the Skimming Flow over Pooled Stepped Spillway

“…Apart from experimental studies, thanks to the advances in the computational performance of computers, numerical methods have also been successfully used to study the detailed flow properties in complex contexts [12][13][14][15]. Baylar et al [16] numerically examined the energy loss and aeration efficiency of the stepped chutes and found that both of them in nappe flow regime were greater than that of the skimming flow regime. Numerical simulations by researchers [17][18][19] demonstrated its high performance in investigating the detailed flow field and pressure distribution over stepped spillway.…”

GEP modeling of oxygen transfer efficiency prediction in aeration cascades

“…The hydraulic design of stepped cascades, and in particular, characteristics of nappe flow, transition flow and skimming flow over stepped cascades has been studied experimentally by a number of investigators. Recently, Baylar ***Associate Professor, Civil Engineering Deptartment, Firat University, Elazig 23119, Turkey (Corresponding Author, E-mail: abaylar@firat.edu.tr) ***Assistant Professor, Civil Engineering Deptartment, Kahramanmaras Sutcu Imam University, Kahramanmaras 46100, Turkey (E-mail: munsal@ksu.edu.tr) ***Assistant Professor, Construction Education Deptartment, Firat University, Elazig 23119, Turkey (E-mail: fozkan@firat.edu.tr) and Emiroglu ( , 2004Emiroglu ( , 2005, Emiroglu and Baylar (2003) and Baylar et al (2006Baylar et al ( , 2007aBaylar et al ( , 2007bBaylar et al ( , 2011 did some detailed studies on the oxygen transfer efficiency of stepped cascades. Today, the applications of soft computing systems, such as neural networks, fuzzy logic, genetic algorithms, least squares support vector machines, and etc.…”