... uses the Favre-averaged Navier-Stokes equations, where time-averaged effects of the flow turbulence on the flow parameters are considered, whereas the other, i.e. large-scale, time-a) b) c) ‐20‐15‐10‐50510‐30‐25‐20‐15‐10‐50510‐0.8 ... orifice model on waterhammer analysis of high and medium heads of small hydropower schemes. Journal of Hydraulic Research, IAHR, Vol. 39 (4), pp. 42 9- 436, ISSN-002 2-1 686, 2001. [12] Pereira, A., ... section of a ball valve Graph 2. Ball valve opening angle of 45º - velocity (v/vo) (a) and pressure (p/po) profiles Graph 2 shows the layout of the velocity and pressure profiles along...