Page - 729 - in Book of Full Papers - Symposium Hydro Engineering

0 2 4 6 8 10 0.06 0.08 0.10 0.12 Opening rate of mid-level outlet (m) Upstream water level is 370m Upstream water level is 375m Upstream water level is 380m 265 270 275 280 285 290 295 300 0.03 0.06 0.09 0.12 0.15 0.18 Downstream water level (m) Mid-level outlet opening 3m Mid-level outlet opening 6m Mid-level outlet opening 8m Fig. 10 Prediction results of vertical vibration acceleration of measuring point T9 with discharge from both surface holes and mid-level outlets Fig. 11 Prediction results of vertical vibration acceleration of measuring points T9 with different downstream water levels 0 5000 10000 15000 20000 25000 30000 -0.03 0.00 0.03 0.06 0.09 0.12 Rate of flow (m 3 /s) Mid-level outlet discharge and upstream water level is 370m Mid-level outlet discharge and upstream water level is 380m Surface hole discharg and upstream water level is 370m Surface hole discharg and upstream water level is 380m Combined discharge and upstream water level from 370m to 380m Fig. 12 Comparison of vibration conditions under different discharge modes It can be seen in Fig.8 to 10 that there was a significant difference between vibration rules under different orifice opening modes. When the surface holes and mid-level outlets were operating, vibrations increased with an increasing in the degree of opening. The mid-level outlets had unfavorable operation ranges from about 5 m to 7 m. A relatively small fluctuating load could be generated at the orifice under both situations. There were no adverse operating conditions when discharging from surface holes, but the increasing range of vibration intensity decreased with a large degree of opening. When discharge occurred at the same time from the surface holes and mid-level outlets, ground vibrations were more sensitive to the degree of opening of the mid-level outlets. The vibration amplitude decreased significantly when the opening degree was between 1 m to 4 m. As can be seen from Fig. 11, the higher the downstream water level, the smaller was the vibration amplitude. While it can be seen from Fig.12 that a higher upstream water level resulted in stronger vibrations, the amplitude growth could be ignored when compared with the flow growth rate. In addition, with the same water flow rate, ground vibration intensity was the strongest when discharge occurred from the 729