M. Emin Emiroglu

Discharge Capacity of Labyrinth Side Weir Located on a Straight Channel

Side weirs, also known as lateral weirs, are flow diversion devices widely used in irrigation as a head regulator of distributaries and escapes, land drainage, and urban sewage systems. The studies on the subject have been generally focused on rectangular and triangular side weirs located on a straight channel. However, the same is not true for labyrinth side weirs. The current studies deal with sediment transport and scour problems around side weirs and lateral structures. The investigation of the hydraulic effects of labyrinth side weirs to increase discharge capacity of them has been studied in this particular work. In the study, 2,830 laboratory tests were conducted for determining discharge coefficient of labyrinth side weirs, and results were analyzed to find the influence of the dimensionless weir length L/b , the dimensionless effective length L/l , the dimensionless weir height p/ h1 , triangular labyrinth side weir included angle θ , and upstream Froude number F1 on the discharge coefficient, wa...

Prediction of lateral outflow over triangular labyrinth side weirs under subcritical conditions using soft computing approaches

Highlights? ANN and GEP techniques could be employed in modeling discharge coefficient. ? The performance of ANN and GEP models is better than that of regression models. ? The value of RMSE of the RBNN model is lower than that of the other models. This paper presents the results of laboratory model testing of triangular labyrinth side weirs located on the straight open channel flume. The discharge capacity of triangular labyrinth side weirs is estimated by using two different artificial neural network (ANN) techniques, that is, the radial basis neural network (RBNN) and generalized regression neural network (GRNN), and gene-expression programming (GEP), which is an extension to genetic programming. 2500 laboratory test results are used for determining discharge coefficient of triangular labyrinth side weirs. The performance of the ANN and GEP models is compared with multi-linear and nonlinear regression models. Comparison results indicated that the neural computing and gene-expression programming techniques could be employed successfully in modeling discharge coefficient from the available experimental data.

Study of the influence of air holes along length of convergent-divergent passage of a venturi device on aeration

One of the most cited water quality parameters in the freshwater hydrosphere is dissolved oxygen. The oxygen concentration in surface waters is a prime indicator of the quality of that water for human use as well as use by the aquatic biota. When a water jet impinges a pool of water at rest, air bubbles may be entrained and carried a way below the pool free surface. This process is called plunging water jet entrainment and aeration. In this paper, air entrainment rate and oxygen transfer efficiency of venturi device with air holes along the length of the convergent-divergent passage was studied experimentally, and in particular, the effect of varying numbers, positions, and open/close status of the air holes. A negative pressure drew air in through holes at the convergent-divergent passage of the venturi device. This phenomenon affected the water jet expansion, the air entrainment rate, and the bubble penetration depth and hence the oxygen transfer efficiency. It was demonstrated that the values of air entrainment rate and the oxygen transfer efficiency of the venturi device were significantly higher than those of the circular nozzle.

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...

The effect of broad-crested weir shape on air entrainment

Aeration is a mass transfer process between the atmosphere and water. Aeration is used for water quality enhancement in sewage treatment plants and in polluted rivers and lakes. This can be enhanced by creating turbulence in the water. Plunging overfall jets from weirs are a particular instance of producing such turbulence. This paper investigates flows over broad-crested weirs of different cross-sectional geometry and their effect on the air entrainment rate. It is demonstrated that the air entrainment rate of the 30° triangular broad-crested weir is better than for the other broad-crested weirs. Moreover, an empirical correlation predicting air entrainment rate was developed for triangular broad-crested weirs. Good agreement between measured and predicted air entrainment rate values was obtained.

The effect of tailwater depth on the local scour downstream of stepped-chutes

This paper reports on an experimental study of the effect of tailwater depth on local scour downstream of stepped-chutes. Different tailwater conditions were tested to study the form of the scour for two gradations of non-cohesive bed material, various flow rates, chute angles, sill heights and step heights. Measurements were taken to obtain the scour hole profile in the equilibrium state of scour, the value of the maximum depth of scour, the location of the maximum scour depth, and the length of the scour hole. The present results indicate that maximum depth and area of scour are highly dependent on tailwater depth. Moreover, the maximum scour depth increases with increases in the discharge and the tailwater depth. It was also found that step geometry, stepped chute angle and the sill types of the stilling basin are very important parameters for scour hole and geometry. A comparison was made between the scour characteristics produced by different tailwater depths. Empirical correlations predicting maximum scour depth were developed. Hence, accurate equations for the maximum scour depth are introduced.

Applicability of Several Soft Computing Approaches in Modeling Oxygen Transfer Efficiency at Baffled Chutes

AbstractThe present study investigates the accuracy of five different data-driven techniques in estimating oxygen transfer efficiency in baffled chutes: feedforward neural network (FFNN), radial ba...

Effects of Antivortex Structures Installed on Trapezoidal Labyrinth Side Weirs on Discharge Capacity and Scouring

AbstractGreater or more constant discharge can be achieved at lower upstream water depths over the weir crest by increasing the effective lengths of labyrinth side weirs. Labyrinth weirs have uneve...

Discharge Coefficient of Sharp-Crested Trapezoidal Labyrinth Weirs

Labyrinth weirs provide an effective means to increase the spillway discharge capacity of dams and are often considered for renovation projects required due to an increase in expected flood inflow to the reservoir of an existing dam. Free crest spillways are hydraulically efficient and safe in operation. Since their discharge capacity is directly proportional to the crest length several types have been developed with the purpose to increase the length of the latter. In recent years many research investigations have considered the hydraulic performance of labyrinth weirs, particularly as dependent on the geometric features. The previous work has improved the design basis for such weirs. In the present study, discharge coefficients were experimentally determined for sharp crested trapezoidal labyrinth weirs of varying side wall angle (α). The experimental results of 21 physical models were used to develop a hydraulic design and analysis method for labyrinth weirs. The present research primarily aims at evaluating various characteristics of a flow-over labyrinth weir by conducting experimentations at wider range of values for important parameters.