M. Cihan Aydin

CFD simulation of free-surface flow over triangular labyrinth side weir

Side weirs are extensively used in the hydraulic and environmental engineering applications. The modeling of free surface flow over a labyrinth side weir is a sophisticated problem in the hydraulic engineering. The water surface profiles over the triangular labyrinth side weirs were investigated by many of the researchers experimentally and theoretically. In this study, the free surface flow over the triangular labyrinth side weir was modeled by using Volume of Fluids (VOF) method to describe the flow characteristics in subcritical flow conditions. A valid method, Grid Convergence Index (GCI) was used to determine the numerical uncertainty of the simulation results. The simulation results were compared with experimental observations, and good agreements were obtained between the both results.

Verification and validation of a computational fluid dynamics (CFD) model for air entrainment at spillway aerators

The results of computational fluid dynamics (CFD) modeling obtained by using FLUENT software with respect to the air entrainment at spillway aerators are compared with data from a physical model study, as well as the results of some empirical equations and prototype observations presented by other investigators. The air-entrainment rates obtained from the CFD analyses are in reasonable agreement with the prototype data and the values calculated from empirical equations, and are better than the physical model data, which include considerable scale effects. The numerical verification procedure in this study is based on the American Society of Mechanical Engineers (ASME) editorial policy statement, which provides a framework for CFD uncertainty analysis. Thus, validation of the CFD is discussed within the scope of this study.

Discharge Characteristics of a Trapezoidal Labyrinth Side Weir with One and Two Cycles in Subcritical Flow

AbstractA labyrinth weir provides an effective way to increase weir crest length without an associated increase in structure width. Labyrinth side weirs have important advantages compared to conventional side weirs in term of discharge capacity, length of the channel opening, and nappe height over the weir. A different equation is needed for each number of cycles to determine the discharge coefficient of labyrinth side weir. Unlike labyrinth spillways, one or two cycles are mostly sufficient for the labyrinth side weirs to accommodate the required discharge. This study examines the hydraulic characteristics of trapezoidal labyrinth side weirs with two cycles in a subcritical situation and the effect on discharge capacity of using single or multiple cycles in side weirs with the same length openings and crest lengths. The results show that a side weir with one cycle has slightly greater discharge coefficient. In addition, the variation of the discharge capacity was investigated for both one-cycle and two-c...

New Approach for Estimation of Rectangular Side Weirs Discharge in Subcritical Flow

AbstractSide weirs are used to divert the flow from a main channel to a desired environmental area. These basic hydraulic elements are commonly preferred in drainage and irrigation systems of surface water. Many studies have been conducted to determine the outflow discharge of side weirs. De Marchi’s approach, which assumes constant specific energy along the side weir, can be applied to describe the surface equation and therefore the discharge coefficient. However, the use of this approach is not easy in experimental and theoretical studies. This study presents a new semianalytical approach that determines the discharge capacity of rectangular side weirs. The findings of this new method are consistent with numerical and experimental results.

Prediction of Discharge Capacity over Two-Cycle Labyrinth Side Weir Using ANFIS

AbstractPhysical and mathematical models widely used in hydraulic engineering are not always effective in practice. Numerical methods such as the adaptive neuro fuzzy inference system (ANFIS) can be quite useful for estimating the key parameters, especially for complex and multivariate mathematical models. The aim of this study is to determine the discharge coefficients of labyrinth side weirs with two cycles using an experiment setup and ANFIS. Estimation of the discharge efficiency of the side weir has been achieved by using 285 laboratory data sets. The results of ANFIS functions and multiple nonlinear regression (MNLR) analysis were compared with experimental results. It is shown that two ANFIS functions, trimf and gbellmf, give the best estimations, and therefore this technique can be used effectively in practice.

Aeration efficiency of bottom-inlet aerators for spillways

Abstract The bottom-inlet aerator can efficiently protect a spillway chute surface from cavitation damage due to high-flow velocities. This aerator, unlike conventional ones, is especially preferred at low Froude numbers and with wide spillway chutes to overcome submerged aerator conditions. In this study, the aeration performance of bottom-inlet aerators was investigated for different Froude numbers and ramp heights. Some practical formulas based on experimental and numerical data were obtained to estimate the air entrainment coefficient (and thus the average air concentration) of the bottom-inlet aerators. The findings were compared to some empirical results in published literature for conventional aerators, and then discussed.

Antivortex Effects on Two-Cycle Trapezoidal Labyrinth Side Weirs

AbstractLabyrinth side weirs can be preferred for the weirs with same opening instead of the other conventional side weirs. However, the vortex occurring in the cycles of the labyrinth side weirs u...