International Journal of Fluid Machinery and Systems

Korean Society for Fluid machinery (한국유체기계학회)
권호 표지
DOI QR코드

DOI QR Code

Large Eddy Simulation of a High Reynolds Number Swirling Flow in a Conical Diffuser

  • Accepted : 2009.05.27
  • Published : 2009.12.01
Download PDF
⟨ Previous Next ⟩

Abstract

The objective of the present work is to improve numerical predictions of unsteady turbulent swirling flows in the draft tubes of hydraulic power plants. We present Large Eddy Simulation (LES) results on a simplified draft tube consisting of a straight conical diffuser. The basis of LES is to solve the large scales of motion, which contain most of the energy, while the small scales are modeled. LES strategy is here preferred to the average equations strategies (RANS models) because it resolves directly the most energetic part of the turbulent flow. LES is now recognized as a powerful tool to simulate real applications in several engineering fields which are more and more frequently found. However, the cost of large-eddy simulations of wall bounded flows is still expensive. Bypass methods are investigated to perform high-Reynolds-number LES at a reasonable cost. In this study, computations at a Reynolds number about 2 $10^5$ are presented. This study presents the result of a new near-wall model for turbulent boundary layer taking into account the streamwise pressure gradient (adverse or favorable). Validations are made based on simple channel flow, without any pressure gradient and on the data base ERCOFTAC. The experiments carried out by Clausen et al. [1] reproduce the essential features of the complex flow and are used to develop and test closure models for such flows.

Keywords

References

  1. Clausen, D.H., Wood, D.H., and Koh, S.G., 1992, “Measurements of a swirling turbulent boundary layer developing in a conical diffuser,” Experimental Thermal and Fluid Science, Vol. 6, No. 2, pp. 39-48. https://doi.org/10.1016/0894-1777(93)90039-L
  2. Manhart, M., Peller, N., and Brun, C., 2008, “Near-wall scaling for turbulent boundary layers with adverse pressure gradient,” Theoretical Comput. Fluid Dynamic, Vol. 22, No. 2, pp. 243-260. https://doi.org/10.1007/s00162-007-0055-0
  3. Nilsson, H., 2006 “Evaluation of OpenFOAM for CFD of turbulent flow in water turbines,” IAHR Symposium on Hydraulic Machinery and Systems, Yokohama, Japan
  4. Page, M. and Beaudoin, M., 2007 “Adapting OpenFOAM for turbomachinery applications,” 2nd OpenFOAM Workshop Zagreb, Croatia
  5. Fureby, C., Tabor, G, Gosman, A.D., and Weller, H.G., 1997 “A comparative study of subgrid scale models in homogeneous isotropic turbulence,” Physic of Fluid Vol. 9, No. , pp. 1416-1429 https://doi.org/10.1063/1.869254
  6. Moser, R.D., Mansour, N.N., and Kim, J., 1999 “Direct numerical simulation of turbulent channel flow up to $Re_{\tau}$ = 590,”Physic of Fluid Vol. 11, No. 4, pp. 943-945 https://doi.org/10.1063/1.869966
  7. Schoppa, W. and Hussain, F., 2000 “Coherent structure dynamics in near-wall turbulence,” Fluid Dynamics Research Vol. 26, pp. 119-139 https://doi.org/10.1016/S0169-5983(99)00018-0
  8. Landman, M.J., 1990 “On the generation of helical waves in circular pipe flow,” Physic of Fluid, Vol. 2, No. 5, pp. 738-747 https://doi.org/10.1063/1.857727
  9. Orlanski, I., 1976 “A simple boundary condition for unbounded hyperbolic flows,” Journal of Computational Physics, Vol. 21, No. 3, pp. 251-269 https://doi.org/10.1016/0021-9991(76)90023-1
  10. Gyllenram, W. and Nilsson, H., 2004 “Numerical investigations of swirling flow in a conical diffuser,” 22 IAHR Symposium on Hydraulic Machinery and Systems, Stockholm, Sweden
  11. Armfield, S.W., Cho, N.-H., and Fletcher C.A.J., 1990 “Prediction of turbulence quantities for swirling flow in conical diffusers,” AIAA, Vol. 28, No. 3, pp. 453-460 https://doi.org/10.2514/3.10414