Cavitation risk estimation at orifice spillway based on UVP and dynamic pressure measurements
Orifice spillways might be affected by cavitation if the profile of the inlet structure includes a relevant curvature. At one of the world’s largest dams, such damages were observed on the profiled slab. To limit their progression, an adapted operation regime of the gates had to be defined using physical model tests. The risk estimation was based on dynamic pressure and velocity measurements, indicating that a maximum gate opening ratio of 0.8 should be respected until the damage is repaired and the profile re-shaped. Beside this, the data set allowed to compare the flow characteristics at the profile surface in terms of turbulence intensity and dominant frequencies. The Ultrasonic Velocity Profiler (UVP) provides comparable characteristic values as the dynamic pressure transmitter (DPS).
Hydraulic investigation and design of roof profile of an orifice spillway using experimental and numerical models
The roof profile of an orifice spillway plays an important role in deciding its discharging capacity. The necessary requirement is that the profile should not experience excessive negative pressures and should be simple to construct. It is found from the literature that the flow through orifice spillway at the entrance does not follow an elliptical roof profile recommended by United States Bureau of Reclamation. During the regime of flow with high heads, flow separation takes place on the orifice roof profile resulting in reduced discharging capacity. It is also found that there is no specific design method available for design of orifice spillway roof profile with respect to the upstream head as well as other parameters. The main aim of the present study is to develop an equation for design of the roof profile of an orifice spillway. Computational fluid dynamics software FLUENT version 6.3.26 was used for the numerical simulations. The numerical model was verified and validated by comparing the results with the physical model. An equation for the design of roof profile was developed after analyzing the observed discharge through orifice, pressures on spillway bottom profile and upper nappe profile of an orifice spillway. The proposed equation was verified with the data which have not been used in deriving the equation. The proposed equation was also validated in terms of coefficient of discharge and pressure distribution on the bottom and roof profile with the existing data of some other real-life orifice spillways. The results are encouraging indicating that the developed equation can be used to get roof profile of an orifice spillway, which can be used at the design stage of an orifice spillway.
PASSIVE AND LOW-ENERGY RESEARCH AND PRACTICES-DEHUMIDIFICATION
Methods of achieving acceptable indoor conditions in overheated, temperate, and underheated humid climates are discussed and compared. Desiccants and desiccant systems utilizing solid and liquid sorbents and various low-energy mechanical systems are described and evaluated.