Turbulence Intensity Distribution in Flow Field under High Head Slid Gates in Conditions of Operating Two Gates

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv

Evaluation of Numerical Method by Fluent for Flow around High Head Slid Gates in Conditions of Operating Two Gates

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv

Numerical Modelling of Hydraulic Flow in Dam Stepped Spillway and Study of Cavitation Phenomenon

Cavitation is a phenomenon leading to damaging surfaces and usually occurs at steep and fast overflows. This can be prevented via decreasing pressure upon the floor of overflows or controlling the flow rate. Furthermore, controlling this phenomenon comes about through increasing air concentrations in the overflow. One of the methods of increasing air concentrations and decreasing the flow rate of the spill is to construct overflows in stepped forms. Dam spillway releases are from among shoot overflows which would confront cavitation phenomenon. This research tries to control this phenomenon via constructing stepped spillways instead of installing aeration systems. Because laboratory models and field researches are costly and time-consuming, using numerical modelling via CFD method for designing and simulating hydraulic flows are suggested. In this research, stepped fast flowing dam releases were designed instead of spillway fast flows, and then simulating flows on spillways, the cavitation phenomenon was studied and evaluated. Results from these simulations show that constructing stepped forms upon dam spillway releases are effective in controlling cavitation phenomenon, so that via reducing flow rate and increasing cavitation index, prevention of this phenomenon becomes possible

Numerical Modelling of Hydraulic Flow in Dam Stepped Spillway and Study of Cavitation Phenomenon

Cavitation is a phenomenon leading to damaging surfaces and usually occurs at steep and fast overflows. This can be prevented via decreasing pressure upon the floor of overflows or controlling the flow rate. Furthermore, controlling this phenomenon comes about through increasing air concentrations in the overflow. One of the methods of increasing air concentrations and decreasing the flow rate of the spill is to construct overflows in stepped forms. Dam spillway releases are from among shoot overflows which would confront cavitation phenomenon. This research tries to control this phenomenon via constructing stepped spillways instead of installing aeration systems. Because laboratory models and field researches are costly and time-consuming, using numerical modelling via CFD method for designing and simulating hydraulic flows are suggested. In this research, stepped fast flowing dam releases were designed instead of spillway fast flows, and then simulating flows on spillways, the cavitation phenomenon was studied and evaluated. Results from these simulations show that constructing stepped forms upon dam spillway releases are effective in controlling cavitation phenomenon, so that via reducing flow rate and increasing cavitation index, prevention of this phenomenon becomes possible

Numerical Modelling of Hydraulic Flow in Dam Stepped Spillway and Study of Cavitation Phenomenon

Cavitation is a phenomenon leading to damaging surfaces and usually occurs at steep and fast overflows. This can be prevented via decreasing pressure upon the floor of overflows or controlling the flow rate. Furthermore, controlling this phenomenon comes about through increasing air concentrations in the overflow. One of the methods of increasing air concentrations and decreasing the flow rate of the spill is to construct overflows in stepped forms. Dam spillway releases are from among shoot overflows which would confront cavitation phenomenon. This research tries to control this phenomenon via constructing stepped spillways instead of installing aeration systems. Because laboratory models and field researches are costly and time-consuming, using numerical modelling via CFD method for designing and simulating hydraulic flows are suggested. In this research, stepped fast flowing dam releases were designed instead of spillway fast flows, and then simulating flows on spillways, the cavitation phenomenon was studied and evaluated. Results from these simulations show that constructing stepped forms upon dam spillway releases are effective in controlling cavitation phenomenon, so that via reducing flow rate and increasing cavitation index, prevention of this phenomenon becomes possible

Effect of Duration on Variations in Bed Topography and Water Surface Profile in a Meandering Channel

In this study, variations in water surface profile and bed topography along a meandering path were examined under different experiment durations. Although several studies have been conducted on sediment and scour in open channels, addressing temporal variations in meandering channels requires independent, merely experimental research. In this regard, a meandering laboratory flume consisting of two consecutive 180-degree bends was used in this study. The test was conducted under clear water conditions and in 6 different durations equal to 0.2, 0.4, 0.5, 0.6, 0.8, and 1 times the equilibrium time (240 minutes). Results indicated that at the downstream bend, lengthening the test time from 0.2 to 0.4, 0.5, 0.6, 0.8, and 1 times the equilibrium time added to the maximum scour by 70, 100, 115, 120, and 165%, and also increased the maximum sedimentation by 30, 25, 45, 45, and 45%, respectively. Moreover, with a comparison made between the average transversal water surface profile for 0, 120, and 240-minute duration tests, it was observed that when these transversal profiles were displaced from 45 degrees to 90, 135, and 180 degrees, the water surface at the inner bank was lowered by 2, 5, and 7% and that at the outer bank decreased by 2, 6, and 12%, respectively

Estudio experimental y numérico de la estabilidad de la pendiente aguas arriba en un embalse de presas de tierra en condiciones de extracción rápida

The rapid ‎drawdown of the dam reservoir is one of the most common situations occurring in the lifetime of a dam. For this reason, one of the main factors in the design of the upstream slope is the rapid drainage of the reservoir. In this case, the upstream slope is in a critical condition and the slope may be unstable. When the water surface in the reservoir is drawdown suddenly, the water level in the dam body does not decrease at the same time as the reservoir water level. The analysis of seepage from the earth dam body and calculation of the water loss play an important role in calculating the amount of pore water pressure, and, consequently, the stability analysis of the dam body. In addition, any seepage analysis is dependent on the hydraulic properties of the dam materials. In order to investigate the effect of hydraulic conductivity on the rapid drawdown of water level and the seepage, an experimental model was constructed of an earth dam. By accurate measurement of hydraulic parameters of the materials in saturated and unsaturated media, the flow through this model was modeled using a disk penetrometer by seep/w software. The results were then compared with the observed data.The rapid ‎drawdown of the dam reservoir is one of the most common situations occurring in the lifetime of a dam. For this reason, one of the main factors in the design of the upstream slope is the rapid drainage of the reservoir. In this case, the upstream slope is in a critical condition and the slope may be unstable. When the water surface in the reservoir is drawdown suddenly, the water level in the dam body does not decrease at the same time as the reservoir water level. The analysis of seepage from the earth dam body and calculation of the water loss play an important role in calculating the amount of pore water pressure, and, consequently, the stability analysis of the dam body. In addition, any seepage analysis is dependent on the hydraulic properties of the dam materials. In order to investigate the effect of hydraulic conductivity on the rapid drawdown of water level and the seepage, an experimental model was constructed of an earth dam. By accurate measurement of hydraulic parameters of the materials in saturated and unsaturated media, the flow through this model was modeled using a disk penetrometer by seep/w software. The results were then compared with the observed data

Numerical Study of Flow Characteristics Over Pivot Weirs

Pivot weirs have a lifting mechanism to change the weir angle relative to the channel bed. These are installed across the waterways in the form of multiple weirs in a row. The water level will be adjusted by changing the weir angle. In this study, the flow over the pivot weirs was simulated with different flow discharges and angles using Ansys CFX model to investigate the flow characteristics. The model was evaluated using USBR experimental data. The standard K-ε turbulence model was considered as the best model for numerical analysis. According to the results, discharge coefficient increases with the inclination angle up to 1.076. The results showed a slight difference in comparison with the previous studies where values of 1.121, 1.110 and 1.082 were presented. The discharge coefficient equations were developed for the weirs. The equations for various hydraulic parameters, including upstream water depth, water head on the crest, the ratio of water head over the crest to the weir height, and weir angle were developed. Based on the developed equations, the operation of the weirs was analyzed during flood events

Decomposing socioeconomic inequality in poor mental health among Iranian adult population: results from the PERSIAN cohort study

Background Socioeconomic inequality in mental health in Iran is poorly understood. This study aimed to assess socioeconomic inequality in poor mental health among Iranian adults. Methods The study used the baseline data of PERSIAN cohort study including 131,813 participants from 17 geographically distinct areas of Iran. The Erreygers Concentration index (E) was used to quantify the socioeconomic inequalities in poor mental health. Moreover, we decomposed the E to identify factors contributing to the observed socioeconomic inequality in poor mental health in Iran. Results The estimated E for poor mental health was - 0.012 (95% CI: - 0.0144, - 0.0089), indicating slightly higher concentration of mental health problem among socioeconomically disadvantaged adults in Iran. Socioeconomic inequality in poor mental health was mainly explained by gender (19.93%) and age (12.70%). Region, SES itself, and physical activity were other important factors that contributed to the concentration of poor mental health among adults with low socioeconomic status. Conclusion There exists nearly equitable distribution in poor mental health among Iranian adults, but with important variations by gender, SES, and geography. These results suggested that interventional programs in Iran should focus on should focus more on socioeconomically disadvantaged people as a whole, with particular attention to the needs of women and those living in more socially disadvantaged regions. Keywords:Mental health; Socioeconomic inequality; Concentration index; Decompositio