Abstract
In the present investigation , a laboratory study of scour characteristics downstream weirs , compound gates has been conducted . The study included the measurement of maximum scour depth and the length of scour hole downstream these structures . Also , the effects of structure height , undersluice opening height , discharge variation and bed material size on the depth and length of scour hole , Two hundred eighty eight Experiments were conducted in a concrete laboratory channel Three sizes of rocks were used are in range of (1.43-2.21) cm and three of 15,20 and 30cm and Three under gate opening heights of 1,2 and 3cm were tested Experimental. Results of this study showed a good direct relationships between relative scour depth (Ds/D50) with Froud Number (Fro) of correlation factor (R2) between (0.9729-0.9911) and other between relative scour length (Ls/D50) with (Fro) of correlation factor (R2) between (0.9636-0.9947) for weirs and another good direct relationships between (Ds/D50) with (Fr0) of correlation factor (R2) between (0.972-0.9866) and with (qu/qd) of correlation factor (R2) between (0.9608-0.9904) and other relationship between (Ls/D50) with (Fro) of correlation factor (R2) between (0.9861-0.9985) and with (qu/qd) of correlation factor (R2) between (0.9847-0.9955), many relationships were obtained the first to estimate (Ds/D50) of correlation factor (R2=0.9311) , the second for (Ls/D50) of correlation factor (R2=0.9421) downstream weirs each of them in terms of (Fr0) and (ΔHw/P) , the third to estimate (Ds/D50) of correlation factor (R2=0.8989) and the forth for (Ls/D50) of correlation factor (R2=0.9212) downstream compound gates each of them in terms of (Fr0),(ΔHw/P),(h0/ΔHt) and (qu/qd) . It was also shown that the scour depth and length downstream compound gates are less than those downstream weirs but the percentage decrement will decrease if the opening of compound gate is increased .
