LOCAL SCOUR BY A DEEPLY SUBMERGED HORIZONTAL CIRCULAR JET

This study investigates local scour caused by a deeply submerged circu lar jet. Both a wall jet and an offset jet were used in the experiment s with uniform cohesionless sediments making up the bed. Experiments c onducted in both air and water show that the densimetric Froude number , F-o is the main characteristic scouring parameter in the correlation of the maximum equilibrium scour dimensions. For an offset jet, the o ffset distance y, which is the vertical distance between the undisturb ed bed level and the center of the jet, also affects the scour hole di mensions. A higher y causes the formation of a smaller scour hole beca use most of the energy is diffused into the flow instead of being used to erode the sediment. For the same F-o value, the size of the scour hole is consistently smaller for tests conducted in water than in air. The reason is attributed to the formation of a sediment ridge at the downstream end of the scour hole. Due to the density difference betwee n air and water, the ridge height is markedly different in the two flo w media.