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In the present study, the hysteretic behavior of supercritical flow that can occur in a channel near additional structures, such as changes in the bed of the channel, has been investigated experimentally and analytically. For this purpose, two diameters of the channel floor materials of 1.12 and 2 cm have been used. The critical depth ranges from 2.7 to 4.5 cm and the used flow rates range from 250 to 600 liters per minute. The flow rate increases in the primary flow and then decreases in the secondary flow into the laboratory flume. The possible flow regimes near the narrowed section are classified based on the relative depths and relative energy remaining in sections 1 and 2 as a function of the Froude number passing under the valve. The results show that by increasing the flow rate and then decreasing it, in some flow rates, two different behaviors can be seen from the flow in the same laboratory conditions. Also, the results showed that with the increase in the diameter of the bed material, the remaining relative energy values have increased a lot, so that in the primary flow, the amount of these depths indicates the subcritical regime, and in the secondary flow, with the formation of hysteresis phenomenon in some discharges, it indicates the regime Also, with the increase in the average diameter of the material, the hysteretic behavior of the flow becomes more intense. [ABSTRACT FROM AUTHOR]

The purpose of this research is to provide a solution to eliminate the vortices formed upstream of the sliding valve. The effect of the threshold with the geometric shapes of semicylinder, cylinder, pyramid and rectangular cube in different widths of 5, 7, 10, 15 and 20 cm under the sliding valve was investigated experimentally. The results of this research showed that the entry of air into the fluid leads to the formation of the vortex phenomenon in the flow profile due to the water absorption of the slide valve from the surface layers. The conservation of angular momentum at the opening of the valve causes the combination of vertical and horizontal components of the velocity near the sliding valve. The results showed that placing the threshold under the horizontal sliding valve increases the horizontal velocity of the flow. Therefore, it turns the vortex with a larger diameter into end-line vortices. Due to the insignificant effect of threshold shape on vortices, its effect was ignored. [ABSTRACT FROM AUTHOR]

The present investigation delves into the intricate dynamics surrounding the incorporation of thresholds and their consequential impact on parameters associated with hydraulic jumps—a phenomenon critical to the efficient functioning of the gates. In the pursuit of a comprehensive understanding, the study employed experimental models of thresholds crafted from polyethylene. These models underwent meticulous examination, encompassing variations in dimensions, widths, and positions relative to the gate. The positions explored included beneath the gate, tangent to the gate upstream, and downstream, each contributing unique insights into the behavior of water flow and energy dissipation. An intriguing outcome emerged as thresholds were introduced at different locations. The energy dissipation for a given gate opening exhibited a discernible increase, shedding light on the intricate relationship between threshold placement and hydraulic performance. Notably, as the initial depth relative to the secondary depth increased, a consequential decrease in the ∆EAB/yA was observed, signaling a convergence between the initial and secondary depths. Further illuminating the findings, a comparative analysis of energy loss was conducted across all three threshold positions—beneath the gate, tangent to the gate upstream, and downstream. This scrutiny uncovered a distinct pattern, indicating a heightened energy dissipation in scenarios where the threshold was submerged, setting it apart from conditions where the threshold was positioned otherwise. In essence, the investigation not only accentuates the intricate interplay between sluice gates, thresholds, and hydraulic parameters but also underscores the importance of considering the placement of thresholds in optimizing the energy dissipation efficiency of these hydraulic structures. [ABSTRACT FROM AUTHOR]

This study numerically investigated the effects of geometric parameters of chimney weirs on the discharge coefficient (Cd). Here, chimney weirs with apex angles 74°, 84°, 94.4°, 106° and 116° at two crest heights were examined. The RNG turbulence model was selected due to its greater accuracy compared to k-ε, k-ω and LES methods for these types of flows. With increasing discharge and crest height, the value of Cd decreases. The effect of constant Cd showed an increase in the percentage of discharge deviation from the discharge values obtained from numerical solution. Based on dimensionless variables such as ratio of water head to the crest height, the ratio of crest length to the crest height, the ratio of the vertical distance between weir crest and the first point where the weir slope changes to the crest height, and the vertex angle of the inverted triangle, non-linear polynomial regression relations were obtained. Highlights A numerical investigation of the discharge coefficient of Chimney weir with different geometry has been done using FLOW-3D software. Chimney weirs have high reliability in measuring discharge due to less sensitivity to changes in upstream water depth. This investigation improves the design of hydraulic control structures. New equation was developed for calculating the discharge coefficient of Chimney weir. [ABSTRACT FROM AUTHOR]

The present research investigates K-Nearest Neighbor (K-NN) and Support Vector Machine (SVM) algorithms for evaluating hydraulic parameters of inclined drops equipped with fishway elements. 395 measurements were analyzed using these two algorithms with a focus on E/E and yd/H. To evaluate algorithm effectiveness, three accuracy measures: R2, RMSE, and the KGE are used for a number of different scenarios. The SVM results show that in the first and second scenarios, respectively, model number 13 yielded RMSE=0.0156, R2=0.973, and KGE=0.961 for the training mode and RMSE=0.0241, R2=0.962, and KGE=0.952 for the testing mode. The KNN algorithm with 75% of the total data employed for the initial sample size gave the best results with RMSE=0.0121, R2=0.986, and KGE=0.975 for the first scenario and RMSE= 0.0123, R2= 0.986, and KGE= 0.975 for the second scenario. Also, the results stated that the RBF kernel function is superior among the kernel functions of the SVM algorithm and the Cityblock distance measurement method among other methods of the K-NN algorithm. On the other hand, the K-NN method was superior to the SVM method. [ABSTRACT FROM AUTHOR]

Screens, perforated units to dissipate energy in hydraulic structures, are investigated numerically in this study. These units are part of a physical setup exposed to supercritical flows, normally created by sluice gates. The interaction of perforated screens and supercritical flows results in local complex three-dimensional flows, which can be analyzed by the application of RANS-based flow equations. The most important controlling parameters include supercritical Froude number between 2 and 10 and screen porosity of 40% and 50%. Numerical water surface profiles and energy dissipation are validated by the author's experimental data. This paper derives a set of equations in terms of depth ratio of the hydraulic jump through the perforated screens and assesses the effect of baffles on energy dissipation. This study seeks a proof-of-concept for the application of the RANS-based technique for further application of the result to real hydraulic structures in due course. Key words: screen, hydraulic jump, energy dissipation, supercritical flow, baffles. Les ecrans, des unites perforees servant a dissiper l'energie dans les ouvrages hydrauliques, sont etudies numeriquement dans le cadre de cette recherche. Ces unites font partie d'une configuration physique exposee aux ecoulements torrentiels, normalement crees par des vannes registres. L'interaction d'ecrans perfores et d'ecoulements torrentiels donne lieu a des ecoulements tridimensionnels locaux complexes, qui peuvent etre analyses au moyen de l'application des equations d'ecoulements selon << Reynolds-averaged-Navier-Stokes >> (RANS). Les parametres determinants les plus importants sont le nombre de Froude supercritique entre 2 et 10 et la porosite de l'ecran de 40% et 50%. La dissipation d'energie et les profils de la ligne d'eau obtenus numeriquement sont valides par les donnees experimentales de l'auteur. Dans le cadre de cette etude, on etablit un ensemble d'equations en fonction du rapport hauteur a longueur du ressaut hydraulique a travers les ecrans perfores et evalue l'effet des dissipateurs d'energie. Cette etude se penche sur la validation de principe de l'application de la technique selon RANS en vue de l'application ulterieure du resultat, et ce, aux ouvrages hydrauliques reels en temps voulu. [Traduit par la Redaction] Mots-cles: ecran, ressaut hydraulique, dissipation d'energie, ecoulement torrentiel, dissipateurs d'energie., 1. Introduction The energy dissipator structures are installed to control flow velocity and dissipate extra energy in the downstream of hydraulic structures. The rate of energy dissipation has the direct [...]