Hydraulic performance evaluation of head works using FLOW 3D

This paper evaluates the hydraulic performance of barrage and under-sluice of Sunkoshi-Marin diversion head works. The numerical simulation was carried out based on the conceptual design of hydraulic structures using FLOW 3D. Velocity vectors, pressure profiles, entrained air volume for barrage and under-sluice were assessed and evaluated. The average velocity over the barrage crest was observed more than 9 m/s at full gate opening. The maximum flow velocity at stilling basin and throughout the longitudinal profile were observed around 10 m/s was 16.90 m/s respectively. There was no sign of negative pressure formation throughout the profile. The minimum pressure observed was 101.356 KPa downstream from diversion axis, along the free surface elevation. Therefore, the structure would be free from cavitation phenomenon. The discharging capacity at FSL with simultaneous operation of barrage and under-sluice bays was assessed as 10,086 m3/s. The flood corresponding to 100 years return period equivalent to 9,241 m3/s easily passes with headwater level being lower than FSL. Further, the extreme discharging capacity of the head works for headwater level 479.5 masl was found 16,547 m3/s. Therefore, deck level adopted as 481.00 masl would be sufficient to release 10,000 years flood.