PRESSURE MEASUREMENTS ON THE GATE SUBJECTED TO SUBMERGED HYDRAULIC JUMP

Vertical gates are commonly used to control the flow and to measure the discharge in irrigation canals and natural streams. Submerged hydraulic jump forms downstream of a gate when the tail water depth is greater than the conjugate depth of the free jump. Interaction of the recirculating flow with the incoming flow with high momentum creates surface pressures fluctuations on the gate. In this study, experimental studies were carried out in a laboratory flume under different flow conditions of jet Froude number and submergence factor in order to provide a clear understanding of how the vortex induced pressure fluctuations affect the gate stability. Simultaneous pressure measurements were made using pressure sensors attached to the different locations on the gate lip. Spatial variations of time-averaged and instantaneous pressure coefficients at the gate lip were evaluated for different inlet Froude numbers and submergence factors. Although the submergence factor is not very effective on the distribution of mean pressure coefficient, Froude number can significantly affect the mean pressure distributions. On the other hand, spatial distributions of instantaneous pressure coefficient strongly depend on both jet Froude number and submergence factor. Frequency spectra of the lift pressures reveal that the magnitude of the spectra increases as the Froude number increases and the slope of the spectra is independent of both Froude number and submergence factor.