5 th International Symposium on Hydraulic Structures Brisbane, Australia, 25-27 June 2014 Hydraulic Structures and Society: Engineering Challenges and Extremes ISBN 9781742721156 - DOI: 10.14264/uql.2014.14 Hydraulic Jump Characteristics in Non-Prismatic Channels S. Gandhi 1 and R.P. Singh 2 1 Department of Civil Engineering, Jaypee University of Engineering & Technology, Guna (MP), INDIA 2 Department of Civil Engineering, Motilal Nehru National Institute of Technology, Allahabad (UP), INDIA E-mail: sumit_gandhi2001@yahoo.co.in Abstract: Empirical relations for hydraulic jump characteristics, viz. sequent depth ratio (Y 2 /Y 1 ), efficiency of jump (E 2 /E 1 ) and relative length of jump (L j /Y 1 ) in non-prismatic channel (i.e., suddenly expanding) with/without appurtenances are developed by introducing dimensionless Reynolds number, and neglecting the frictional effect for approach Froude numbers between 2 to 9 under different channel conditions. Developed empirical models were also tested, validated and compared with acquired experimental data as well as with literature data. Close fitness of the empirical models with appurtenances under varying dimensions, positions of baffle blocks and end sill provides accurate prediction of same for higher value of Froude number. Keywords: Non-prismatic channel, hydraulic jump characteristics, Reynolds number, baffles & sill. 1. INTRODUCTION In stilling basin when supercritical flow changes to subcritical flow during hydraulic jump occurrence, air is entrained and gets released in the form of air bubbles. Therefore, it is of considerable importance in many practical problems to control high energy turbulent flow. Compared to prismatic channels non-prismatic channels (suddenly expanding) with appurtenances not only modify the hydraulic jump characteristics but also effect significantly the formation of symmetric flows downstream of the channel. Also, non-prismatic channels are useful where there are design constraints to reduce basin length. A significant work has been reported by Chanson (1996), Chanson and Montes (1998), Chanson (2000), Ranga Raju et al. (1980), Pagliara and Chiavaccini (2006) on appurtenances and energy loss in the study of hydraulic jump. Rajaratnam (1964) and Tyagi et al. (1978) have studied the effect of the force on baffle blocks and sill in suddenly expanding channel. Rajaratnam and Subramanyam (1968), Negm et al. (2000) and Negm (2000) proved that the sequent depth ratio is a function of approach Froude number and expansion ratio only. There are some studies on hydraulic jump characteristics indicates that hydraulic jump characteristics are dependent on Froude number only [Elevatorski (2008), Wu and Rajaratnam (1996), Ranga Raju et al (1980), etc]. However, [Iwao et al. (2003) and Afzal and Bushra (2002)] have shown that Reynolds number also has significant effect on the modification of hydraulic jump characteristics. Keeping above fact in view, the present study is oriented towards the development of data based empirical models for different hydraulic jump characteristics for non-prismatic channel by introducing Reynolds number ‘R e1 ’. 2. BACKGROUND: LITERATURE REVIEW Rajaratnam and Subramanya (1968) suggested the use of the empirical equations for sequent depth ratio in suddenly expanding channel which is valid for B 1 /B 2 ratio in the range 0.3 to 0.9 and approach Froude number F r1 between 2 and 9 as: