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In hydropower plants the kinetic energy of falling water is captured to generate electricity. In this process, the formation of vortices with an air core at the power intake entrances is expected at lower reservoir levels. The entrainment of air and swirl into the power tunnels leads to a reduction of power generation and vibration and damage to the turbine blades. To use the maximum potential of water power at lower reservoir levels when water is scarce, it is necessary to prevent vortex formation. Anti-vortex devices are usually considered as an efficient method for vortex prevention. The Godar-e-Landar Dam and Hydropower Plant is sited on the Karun River in the province of Khuzestan, Iran, with the capacity of 2000 MW. There are four horizontal power intakes where the capacity of each intake is equal to 375 m 3 /s. The dam is a rock fill type with 170 m height from the foundation. The dam has a gated spillway with an ogee chute and stilling basin. In the present work a physical model was used to study the formation and prevention of air core vortices at power intakes of the dam. Studies showed that vortices form when the reservoir water level decreases from a certain elevation and air enters the power tunnels. The performance of anti-vortex walls was therefore examined to eliminate vortices or reduce their strength and prevent entrainment of air. The anti-vortex walls were constructed on top of each intake to increase the friction stresses within the vortex path. To distinguish the vortex type, light colorful objects were released in the flow. Results of experiments showed Type 4 vortices (which may be a stronger air core Type 6 in prototype) reduced to a weak vortex Type 2 and 1 when an anti-vortex wall was installed. Moreover, the vortices became very unstable.

Vortex study on a hydraulic model of Godar-e-Landar Dam and Hydropower Plant