Effect of Turbulence Intensity on Turning Diffuser Performance at Various Angle of Turns

CFD Letters
Volume 12, No. 1, January 2020, Pages 48-61

Lim Gim Huang1, Normayati Nordin1,*, Lim Chia Chun1, Nur Shafiqah Abdul Rahim1, Shamsuri Mohamed Rasidi1, Muhammad Zahid Firdaus Shariff1

1 Centre for Energy and Industrial Environment Studies, Faculty of Mechanical and Manufacturing Engineering, Universiti Tun Hussein Onn Malaysia, 86400 Parit Raja, Johor, Malaysia
*Corresponding author: mayati@uthm.edu.my


3-D turning diffuser; turbulence intensity; pressure recovery coefficient; flow uniformity; Computational Fluid Dynamics (CFD)


The performances of turning diffuser are highly affected due to the nature of its geometries by the existence of flow separation and dispersion of core and secondary flows. Turning diffusers with potential turbulence intensity may lead to optimum performance. However, there has been yet insufficient literature on 3-D turning diffuser fluid flow performance analysis by varying inlet turbulence intensity. Hence, this study aims to investigate the effect of turbulence intensity on 30o and 90o 3-D turning diffuser performances. The performances of turning diffusers were scientifically evaluated in term of pressure recovery coefficient, Cp and flow uniformity index, ?out while turbulence intensity was varied from 1.5% to 7.5%. This work involved both numerical and experimental methods. ANSYS Computational Fluid Dynamics (CFD) was used for the simulation and Particle Image Velocimetry (PIV) for the experiment. The inlet free-stream turbulence intensity was varied which imposed on the flow by suppressing the separation of the inner wall boundary layer and mixing to provide optimum uniformity of the flow. The pressure recovery increased 8.02% and 9.74% while the flow uniformity improved about 2.95% and 1.60% in 30° case and 90° case respectively. In conclusion, the 7.5% of turbulence intensity is promising to introduce in the ducting flow application so as to improve the pressure recovery and the flow uniformity of both 30° and 90° turning diffuser cases.


Lim, Gim Huang, et al. “Effect of Turbulence Intensity on Turning Diffuser Performance at Various Angle of Turns.” CFD Letters 12.1 (2020): 48-61.

Lim, G. H., Normayati, N., Lim, C. C., Nur Shafiqah, A. R., Shamsuri, M. R., & Muhammad Zahid, F. S.(2020). Effect of Turbulence Intensity on Turning Diffuser Performance at Various Angle of Turns. CFD Letters, 12(1), 48-61.

Lim Gim Huang, Normayati Nordin, Lim Chia Chun, Nur Shafiqah Abdul Rahim, Shamsuri Mohamed Rasidi and Muhammad Zahid Firdaus Shariff.”Effect of Turbulence Intensity on Turning Diffuser Performance at Various Angle of Turns.” CFD Letters. 12, no. 1 (2020): 48-61.

Lim, G.H., Normayati, N., Lim, C.C., Nur Shafiqah, A.R., Shamsuri, M.R., and Muhammad Zahid, F.S., 2020. Effect of Turbulence Intensity on Turning Diffuser Performance at Various Angle of Turns. CFD Letters 12(1), pp. 48-61.

Lim GH, Normayati N, Lim CC, Nur Shafiqah AR, Shamsuri MR, Muhammad Zahid FS. Effect of Turbulence Intensity on Turning Diffuser Performance at Various Angle of Turns. CFD Letters. 2020;12(1): 48-61.


[1] Nordin, Normayati, Abdul Karim, Zainal Ambri, Safiah Othman, and Vijay R. Raghavan. “Effect of varying inflow reynolds number on pressure recovery and flow uniformity of 3-D turning diffuser.” In Applied Mechanics and Materials, vol. 699, pp. 422-428. Trans Tech Publications, 2015.
[2] Li, Angui, Changqing Yang, Tong Ren, Xin Bao, Erwei Qin, and Ran Gao. “PIV experiment and evaluation of air flow performance of swirl diffuser mounted on the floor.” Energy and Buildings 156 (2017): 58-69.
[3] Sinha, Prasanta K., A. K. Biswas, A. N. Mullick, and B. Majumdar. “Flow development through a duct and a diffuser using CFD.” Int J Eng Res Appl 7 (2017): 46-54.
[4] Fox, Robert W., and S. J. Kline. “Flow regimes in curved subsonic diffusers.” Journal of Basic Engineering 84, no. 3 (1962): 303-312.
[5] Hoffmann, J. A., and G. Gonzalez. “Effects of small-scale, high intensity inlet turbulence on flow in a two-dimensional diffuser.” Journal of Fluids Engineering 106, (1984): 121-124.
[6] Sullerey, R. K., Brajesh Chandra, and V. Muralidhar. “Performance comparison of straight and curved diffusers.” Defence Science Journal 33, no. 3 (1983): 195-203.
[7] Mahalakshmi, N. V., G. Krithiga, S. Sandhya, J. Vikraman, and V. Ganesan. “Experimental investigations of flow through conical diffusers with and without wake type velocity distortions at inlet.” Experimental Thermal and Fluid Science 32, no. 1 (2007): 133-157.
[8] Khong, Y. T., N. Nordin, S. M. Seri, A. N. Mohammed, A. Sapit, I. Taib, K. Abdullah, A. Sadikin, and M. A. Razali. “Effect of turning angle on performance of 2-D turning diffuser via Asymptotic Computational Fluid Dynamics.” In IOP Conference Series: Materials Science and Engineering, vol. 243, no. 1, p. 012013. IOP Publishing, 2017.
[9] Jakirli?, S., G. Kadavelil, M. Kornhaas, M. Schäfer, D. C. Sternel, and C. Tropea. “Numerical and physical aspects in LES and hybrid LES/RANS of turbulent flow separation in a 3-D diffuser.” International Journal of Heat and Fluid Flow 31, no. 5 (2010): 820-832.
[10] Tham, Wei Xian, Normayati Nordin, Azian Hariri, Nurul Fitriah Nasir, Norasikin Mat Isa, Musli Nizam Yahya, and Suzairin Md Seri. “Asymptotic Computational Fluid Dynamic (ACFD) Study of Three-Dimensional Turning Diffuser Performance by Varying Angle of Turn.” International Journal of Integrated Engineering 11, no. 5 (2019): 109-118.
[11] Nordin, Normayati, Safiah Othman, Vijay R. Raghavan, and Zainal Ambri Abdul Karim. “Verification of 3-D stereoscopic PIV operation and procedures.” International Journal Engineering and Technology IJET/IJENS 12, no. 4 (2012): 19-26.
[12] Bourgeois, Jason A., Robert J. Martinuzzi, Eric Savory, Chao Zhang, and Douglas A. Roberts. “Assessment of turbulence model predictions for an aero-engine centrifugal compressor.” Journal of Turbomachinery 133, no. 1 (2011): 011025.
[13] Nguyen, Cuong K., Tuan D. Ngo, Priyan A. Mendis, and John CK Cheung. “A flow analysis for a turning rapid diffuser using CFD.” In 4th International Symposium on Computational Wind Engineering, (2006).
[14] Nordin, Normayati, and BANDAR SERI ISKANDAR. “Performance investigation of turning diffusers at various geometrical and operating parameters.” PhD diss., Universiti Teknologi Petronas, 2016.
[15] Selamat, Ubaidullah, Kahar Osman, Arul Hisham A. Rahim, and Selamat Ubaidullah. “Heat and Flow Analysis of a Chilled Water Storage System using Computational Fluid Dynamics.” Journal of Advanced Research in Fluid Mechanics and Thermal Sciences 57, no. 1 (2019): 131-140.
[16] Nordin, N., S. M. Seri, I. Taib, A. N. Mohammed, M. K. Abdullah, and A. Sapit. “Secondary flow vortices and flow separation of 2-D turning diffuser via particle image velocimetry.” In IOP Conference Series: Materials Science and Engineering, vol. 226, no. 1, p. 012149. IOP Publishing, 2017.
[17] Chong, T. P., P. F. Joseph, and P. O. A. L. Davies. “A parametric study of passive flow control for a short, high area ratio 90deg curved diffuser.” Journal of Fluids Engineering 130, no. 11 (2008): 111104.
[18] Abe, K., M. Nishida, A. Sakurai, Yuji Ohya, Hisashi Kihara, E. Wada, and K. Sato. “Experimental and numerical investigations of flow fields behind a small wind turbine with a flanged diffuser.” Journal of wind engineering and industrial aerodynamics 93, no. 12 (2005): 951-970.