Numerical Investigation of Turning Diffuser Performance by Varying Geometric and Operating Parameters


Article Preview

This paper presents a numerical investigation of pressure recovery and flow uniformity in turning diffusers with 90o angle of turn by varying geometric and operating parameters. The geometric and operating parameters considered in this study are area ratio (AR= 1.6, 2.0 and 3.0) and inflow Reynolds number (Rein=23, 2.653E+04, 7.959E+04, 1.592E+05 and 2.123E+05). Three turbulence models, i.e. the standard k-e turbulence model (std k-e), the shear stress transport model (SST-k-W) and the Reynolds stress model (RSM) were assessed in terms of their applicability to simulate the actual cases. The standard k-e turbulence model appeared as the best validated model, with the percentage of deviation to the experimental being the least recorded. Results show that the outlet pressure recovery of a turning diffuser at specified Rein improves approximately 32% by varying the AR from 1.6 to 3.0. Whereas, by varying the Rein from 2.653E+04 to 2.123E+05, the outlet pressure recovery at specified AR turning diffuser improves of approximately 24%. The flow uniformity is considerably distorted with the increase of AR and Rein. Therefore, there should be a compromise between achieving the maximum pressure recovery and the maximum possible flow uniformity. The present work proposes the turning diffuser with AR=1.6 operated at Rein=2.653E+04 as the optimum set of parameters, producing pressure recovery of Cp=0.320 and flow uniformity of su=1.62, with minimal flow separation occurring in the system.



Edited by:

Mohamed Othman




N. Nordin et al., "Numerical Investigation of Turning Diffuser Performance by Varying Geometric and Operating Parameters", Applied Mechanics and Materials, Vols. 229-231, pp. 2086-2093, 2012

Online since:

November 2012




[1] R.W. Fox and S.J. Kline, Flow regime data and design methods for curved subsonic diffusers, J. Basic Eng. ASME, vol. 84, pp.303-312, (1962).


[2] C.J. Sagi and J.P. Johnson, The Design and Performance of Two-Dimensional, Curved Diffusers, J. Basic Eng. ASME, vol. 89, pp.715-731, (1967).

[3] G. Guohui and B.R. Saffa, Measurement and computational fluid dynamics prediction of diffuser pressure-loss coefficient, Applied Energy, vol. 54(2), pp.181-195, (1996).


[4] B. Majumdar and D.P. Agrawal, Flow characteristics in a large area ratio curved diffuser, Proc. Instn. Mech. Engrs., vol. 210, p.65, (1996).

[5] E.G. Tulapurkara, A.B. Khoshnevis and J.L. Narasimhan, Wake boundary layer interaction subject to convex and concave curvatures and adverse pressure gradient, Exp. In Fluids, vol. 31, pp.697-707, (2001).


[6] C.K. Nguyen, T.D. Ngo, P.A. Mendis and J.C.K. Cheung, A flow analysis for a turning rapid diffuser using CFD, J. Wind Eng., vol. 108, pp.749-752, (2006).

[7] T.P. Chong, P.F. Joseph and P.O.A.L. Davies, A parametric study of passive flow control for a short, high area ratio 90 deg curved diffuser, J. Fluids Eng., vol. 130, (2008).


[8] W.A. El-Askary and M. Nasr, Performance of a bend diffuser system: Experimental and numerical studies, Computer & Fluids, vol. 38, pp.160-170, (2009).


[9] Y.C. Wang, J.C. Hsu and Y.C., Lee, 9], "Loss characteristics and flow rectification property of diffuser valves for micropump applications, Int. J. of Heat and Mass Transfer, vol. 52, pp.328-336, (2009).


[10] J.A. Bourgeois, R.J. Martinuzzi, E. Savory, C. Zhang and D. A. Roberts, Assessment of turbulence model predictions for an aero-engine centrifugal compressor, J. Turbomachinery, vol. 133, pp.1-15, (2010).


[11] W.P. Jones, B.E., Launder, The calculation of low-reynolds number phenomena with a two equation model of turbulence, Int. J. Heat Mass Transfer, vol. 6, pp.1119-1130, (1973).


[12] M.K. Gopaliya, M. Kumar, S. Kumar, S.M. Gopaliya Analysis of performance characteristics of S-Shaped diffuser with offset, Aerospace Science and Technology, vol. 11, pp.130-135, (2007).


[13] I.H. Ibrahim, E.Y.K. Ng, K. Wong and R. Gunasekaran, Effects of centerline curvature and cross-sectional shape transitioning in the subsonic diffuser of the f-5 fighter jet, J. Mechanical and Science Technology, vol. 22, pp.1993-1997, (2008).


[14] J.H. Bell and R.D. Mehta, Contraction design for low-speed wind tunnels, NASA 177488, Contract NAS2-NCC-2-294, (1988).