Velocity distribution and drag characteristics of sill and baffles in submerged hydraulic jump

Abstract

The present investigation deals with the measurement of flow field in the body of the hydraulic jump, both on smooth and rough (artificial turf beds). Sills and baffles are used to assist the formation of hydraulic jump in a stilling basin. The drag offered by these appurtenances varies with the roughness of the bed, their distance from the toe of the jump and whether the jump is in an un-submerged or submerged condition. Although numerous investigators have studied hydraulic jump earlier, new insight is gained with every new investigation. Experiments were conducted in a smooth open channel (be visual observation). The channel has a 30hp pump and discharge about 0.19 m3 /s, which can be accurately measured over a suppressed weir. The three shutters at the end (tail gate) were used to control the tail water depth. Therefore, the hydraulic jump was created by the supercritical flow from a sluice gate opening which is in the form of a quadrant of an ellipse to suppress the formation of vena-contracta. The instantaneous velocity measurements were obtained using an Acoustic Doppler Velocimeter (ADV). The velocity measurements were despiked using Velocity Signal Analyser (VSA). The velocity distribution in the forward flow direction in the hydraulic jumps is similar to the turbulent wall jets. The velocity profiles exhibit the self-similarity and the velocity distribution follows Verhoff s equation. The characteristics of the velocity profiles were determined for free (un-submerged) and submerged hydraulic jump on smooth and rough (artificial turf) bed surfaces. From, the above aspects it is observed that the velocity decay and the growth of wall jet are newline