J. Civil Eng. Architect. Res. Vol. 2, No. 9, 2015, pp. 931-937 Received: June 23, 2015; Published: September 25, 2015 Journal of Civil Engineering and Architecture Research Head Loss Estimation of Water Jets from Flip Bucket of Cakmak-1 Diversion Weir and HEPP Cuneyt Yavuz, Ali Ersin Dincer, Kutay Yilmaz and Samet Dursun Department of Civil Engineering, Middle East Technical University, Ankara 06880, Turkey Corresponding author: Cuneyt Yavuz (cyavuz@metu.edu.tr) Abstract: A jet issued from flip bucket of spillway of a dam interacts with the surrounding air and develops into an aerated turbulent jet. Depending on the relative jet thickness, the fall height and the level of turbulence, the jet may be dispersed in air forming an aerated water body which will eventually plunge into the river surface at sufficiently far downstream of the flip bucket. If not aerated, the jet may have a larger impact on the river bed causing excessive scouring of the river bed. Dispersion of jet by aeration is the practical tool to reduce the jet impact. The spillway of Cakmak I Diversion Weir and HEPP project located in Kahramanmaras province of Turkey is used as a case study to estimate trajectory lengths with air entrainment. Depending on projectile motion theory, head losses due to the air entrainment can be determined between the difference of the trajectory lengths with and without air resistance. Empirical equations were used to calculate the jet trajectory length with and without air entrainment. For the same conditions, the flow is modelled with commercially available computer software that uses volume of fluid (VOF) technique. Results from empirical equations and from numerical simulations are compared and differences between the results are discussed. Key words: Water jet, flip bucket, trajectory length, head loss, jet dispersion, air entrainment, scour, flow-3D. Nomenclature: g Gravitational acceleration (m 2 /s) y 0 Water depth on the bucket lip(m) h L Head loss due to the air entrainment (m) H 0 Water level above the sharp crested weir(m) H t Total head at the bucket lip(m) H j1 Jet head without considering air entrainment (m) H j2 Jet head with considering air entrainment(m) L t Throw distance calculated using Projectile motion formula(m) L 1 Throw distance considering air resistance calculated Kawakami’s formula(m) L ts Throw distance obtained from numerical solution (m) L 1s Throw distance considering air resistance obtained from numerical solution (m) k Constant related to air resistance Q Water discharge (m 3 /s) V j Velocity at the bucket lip (m/s) V t Velocity at impingement point(m/s) z i Vertical drop from lip to tail water level (m) α Trajectory length constant from Eq. 6 α j Flip bucket lip angle (degree) α t Trajectory angle(degree) 1. Introduction Flip buckets are used to dissipate energy of the water coming from the spillway especially for large flow velocities. Flip buckets can be designed in various shapes and scales according to geological and economic circumstances involving relative curvature, deflection angles, take-off angles and special components are in operation. Mason [1] collected the studies on ski jump and recommended some points of design as follows: (a)Minimum bucket radius should be designed three out of five times the approach flow of the bucket; (b)Take off angle of the flip bucket between 200 and 350; (c)Water jet should be spread in air with the angle of 50; (d)Lip of the bucket ought to be flat due to the cavitation risk.