Characteristics of Transverse Waves in Supercritical Flow behind Pier of the Dam's Spillway Gates

Abstract: Usually in the chute spillways designers are facing problems such as aeration، transverse waves، cavitations and erosion. Although many studies have been performed to determine the flow characteristics over these structures، however، little information are available on supercritical flow downstream of chutes piers and their effects on flow domain. Due to the flow interaction with the chutes piers، a supercritical and wavy flow known as rooster tail is formed. The result of this wavy flow is three kinds of transverse waves، the first one is formed downstream of the piers، the second is formed on the middle of the chute and the third is formed on the wall of the spillway. The importance of investigate this phenomenon is because of influencing on flow field and creating unbalanced hydraulics conditions. In this Study، experimental Investigation the formation of the transverse waves and its profiles are presented. Experiments were conducted on a scaled physical model of Kheirabad dam spillway، at Water Research Institute of Iran. The results showed that three types of waves are created by the placing gate''s pier on the chutes. The height of these waves can be more than twice the water depth and thus impact on the design of the side walls of chute. It was realized Froude number of flow and gate opening have the main effect on wave formation. Finally، the equations used to express the maximum height of waves and location of its formation was presented for the three types of waves.