Impact pressures of falling jets on the plunging pool bed

Subject Areas : Farm water management with the aim of improving irrigation management indicators

منوچهر فتحی مقدم ¹ (استاد گروه هیدرولیک دانشگاه شهید چمران اهواز)
سجاد کیانی ² (دانشجوی دکتری؛ گروه سازه‌های آبی؛ دانشکده مهندسی علوم آب؛ دانشگاه شهید چمران اهواز)
بابک لشکرآرا ³ (استادیار؛ گروه مهندسی عمران؛ دانشگاه صنعتی جندی شاپور دزفول)

Received: 2016-07-02 Accepted : 2016-10-22 Published : 2017-02-19

Keywords: rough surface, plunging pool, Froude number, falling jet, dam spillway,

Abstract :

Plunging pools are constructed at the downstream of dam spillways to dissipate the excess energy. The turbulent flow velocity converts to the dynamic pressure due to impact of flow with the pool’s bed. The aim of this research is to determine impact pressure of a vertical jet on plunging pool bed. Hence, the experiments were carried out in four different discharges (ranging from 6 to 27.5 lit/s according to the nozzle diameters), three jet diameters including 4.3, 5.2 and 8.2 cm and four falling heights of 37, 60, 90 and 120 cm. Also the experiments are conducted in similar flow conditions for smooth and rough surfaces, and results are compared. Dynamic pressures were measured with a pressure transducer. The analysis of data showed that increase of jet diameter causes decrement in the dynamic pressure coefficient. Results revealed an increase in dynamic pressures due to roughness of contacting surface. Moreover, variations of jet Froude number and fall length have significant effects on the dynamic pressure coefficient. The impact pressure was the highest in the surface center and was gradually reduced in outer zones.

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