Stilling basins with sudden expansions are one of the energy dissipater structures. This structure has many applications downstream of hydraulic structures, such as spillways, sluice gates and chutes. In the jump, the pressure fluctuations resulting from intense macro-s More
Stilling basins with sudden expansions are one of the energy dissipater structures. This structure has many applications downstream of hydraulic structures, such as spillways, sluice gates and chutes. In the jump, the pressure fluctuations resulting from intense macro-scale turbulence must be carefully considered during the design of the structure. Roughness can also cause changes in the behavior of stream line and vortices. So far its effects on the hydrodynamic characteristics of the jump have not been studied. In this study many tests are conducted in a relatively large flume size of 0.8 meter wide and 12 meter length. Channel expansions ratio (B1/B2) was 0.33 and data are presented for Froude numbers from 4-9.2. Measurements were conducted in the bed of flume by means of pressure transducers systems. The final results of this study show that roughness decreases Intensity of fluctuating pressure in sudden expansion stilling basin. Test results were compared with those of smooth sudden expansion jump and classical jump which indicates that the peak values of RMS dimensionless pressure fluctuations (Cp'), are 53% lower than smooth sudden expansion jump and are reduced 70% compared with classical jump. Intensity of fluctuating pressure at the position of about (0.15-0.3) Lj, can reach the maximal value. Peak values of RMS dimensionless pressure fluctuations C'p max up to 0.023 and maximum positive (negative) deviation Cp-and Cp-values up to 0.08 were obtained. In addition to dimensionless coefficients of pressure fluctuations, the longitudinal distribution of pressures and determined pressure fluctuations and extreme values occurring during flow are obtained.
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Due to the importance of stilling basin blocks and the significant effect of their shape and dimension on energy dissipation, and since various studies have been carried out on hydraulic jump properties and properties of stilling basins while fewer studies have addresse More
Due to the importance of stilling basin blocks and the significant effect of their shape and dimension on energy dissipation, and since various studies have been carried out on hydraulic jump properties and properties of stilling basins while fewer studies have addressed the effect of integrated sinusoidal blocks on hydraulic jump properties, the present research was designed to analyze the effect of sinusoidal blocks height using the Flow 3D model, which is a powerful software product for simulating flow turbulence in two or three dimensions. Froude numbers in this research ranged from 4.6 to 12.2, which indicated that as flow’s Froude number increases from 4.2 to 11, the length of roller and hydraulic jump escalate. Moreover, relative roller length changes for about 30% to 40% by changing the height of blocks. Consequently, jump submerges in the beginning of outflow of flow from below the vent and output flow dissipates quickly. Jump length also decreases with an increase in blocks height. Finally, roller length decreases by 40 to 50 cm with outflow of flow from below the vent for the following two values: (The wave steepness) t/s=0.25 and 0.75.
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Hydraulic structures such as stilling basins, mainly are used for the purpose of energy dissipation in the lower zone of overflows, chute and diversion dams, in order to control hydraulic jump. In this research, the rate and effect of the jump is determined by laborator More
Hydraulic structures such as stilling basins, mainly are used for the purpose of energy dissipation in the lower zone of overflows, chute and diversion dams, in order to control hydraulic jump. In this research, the rate and effect of the jump is determined by laboratory tests. In these experiments, the sharp roughness of the bed of basin and also the change in the slope of the basin( structure ) from 0 to 0.3 percent were tested and parameters such as flow rate, initial depth, secondary depth, jump length of water surface profile, water head on overflow crown and water head prior to overflow were accurately measured. The analysis of data showed that the sharp roughness can effectively reduce the length of jump to to 35.5%. For sharp shape roughness, with an increase in the landing rate, the ratio y2 / y1 increases by an average of 6.5%. For a Froude number with a sharp roughness setting, the Lj / y2 ratio decreases by an average of 1.2%.
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