Seite - 693 - in Book of Full Papers - Symposium Hydro Engineering

Fig. 6. Pressure distribution on dam spillway Figure 6 indicates the pressure on each point of the location which described in Figure 5 where the transducers were installed. As can be seen that the pressure is vary along the spillway, some location has higher pressure due to turbulence and impact of the water with the stepped surface. The highest water pressure was shown at point 6 of tranducer location where the point of inception occurred. It is also found that negative pressure also occurred at point 3 of tranducer location where the transition zone from the smooth surface into stepped surface at Qpmf. To avoid cavitation effects from this negative pressure, aerator can be implemented at the spillway to minimize the impacts. 3.3. SCOURING CONDITION Scouring test were conducted for outflow discharge of period Q100yrs = 133 m3/s (See figure 7). Three scenarios were conducted, 1st scenario to study existing condition without downstream protection, 2nd and 3rd to study riprap protection. Fig. 7. 1st scenario without downstream protection -0,5 0 0,5 1 1,5 2 2,5 3 3,5 0 20 40 60 80 100 Distance from crest spillway (m) Q2year Q100year Q1000year Qpmf 693