Numerical Simulation of Flow over a Rough Bed
Publication: Journal of Hydraulic Engineering
Volume 133, Issue 4
Abstract
This paper presents results of a direct numerical simulation (DNS) of turbulent flow over the rough bed of an open channel. We consider a hexagonal arrangement of spheres on the channel bed. The depth of flow has been taken as four times the diameter of the spheres and the Reynolds number has been chosen so that the roughness Reynolds number is greater than 70, thus ensuring a fully rough flow. A parallel code based on finite difference, domain decomposition, and multigrid methods has been used for the DNS. Computed results are compared with available experimental data. We report the first- and second-order statistics, variation of lift/drag and exchange coefficients. Good agreement with experimental results is seen for the mean velocity, turbulence intensities, and Reynolds stress. Further, the DNS results provide accurate quantitative statistics for rough bed flow. Detailed analysis of the DNS data confirms the streaky nature of the flow near the effective bed and the existence of a hierarchy of vortices aligned with the streamwise direction, and supports the wall similarity hypothesis. The computed exchange coefficients indicate a large degree of mixing between the fluid trapped below the midplane of the roughness elements and that above it.
Get full access to this article
View all available purchase options and get full access to this article.
Acknowledgments
This work was carried out under Grant No. GR/M85241 from the U.K. Engineering and Physical Science Research Council (EPSRC). Additional computing resources and support were provided by the U.K. Turbulence Consortium from HPC Grant No. GR/R64957/01. The writers gratefully acknowledge the support of these organizations. Invaluable comments from the reviewers and the Associate Editor for the improvement of the paper are also gratefully acknowledged.
References
Ashrafian, A., Andersson, H. I., and Manhart, M. (2004). “DNS of turbulent flow in a rod-roughened channel.” Int. J. Heat Fluid Flow, 25(3), 373–383.
Bhaganagar, K., and Kim, J. (2002). “Physics of roughwall turbulent boundary layer.” Bull. Am. Phys. Soc., 47(10), 55–55.
Choi, H., Moin, P., and Kim, J. (1993). “Direct numerical simulation of turbulent flow over riblets.” J. Fluid Mech., 255, 503–539.
Defina, A. (1996). “Transverse spacing of low-speed streaks in a channel flow over a rough bed.” Coherent flow structures in open channels, P. J. Ashworth, S. J. Bennett, J. L. Best, and S. J. McLelland, eds., Wiley, New York, 87–99.
Grass, A. J. (1971). “Structural features of turbulent flow over smooth and rough boundaries.” J. Fluid Mech., 50(2), 233–255.
Grass, A. J., and Mansour-Tehrani, M. (1996). “Generalized scaling of coherent bursting structures in the near-wall region of turbulent flow over smooth and rough boundaries.” Coherent flow structures in open channels, P. J. Ashworth, S. J. Bennett, J. L. Best, and S. J. McLelland, eds., Wiley, New York, 41–61.
Grass, A. J., Stuart, R. J., and Mansour-Tehrani, M. (1991). “Vortical structures and coherent motion in turbulent flow over smooth and rough boundaries.” Philos. Trans. R. Soc. London, Ser. A, 336(1640), 33–65.
Kim, J., Moin, P., and Moser, R. (1987). “Turbulence statistics in a fully developed channel flow at low Reynolds number.” J. Fluid Mech., 177, 133–166.
Lam, K., and Banerjee, S. (1992). “On the condition of streaks formation in a bounded turbulent flow.” Phys. Fluids A, 4(2), 306–320.
Leonardi, S., Orlandi, P., Smalley, R. J., Djenidi, L., and Antonia, R. A. (2003). “Direct numerical simulations of turbulent channel flow with transverse square bars on one wall.” J. Fluid Mech., 491, 229–238.
Lu, S. S., and Wilmarth, W. W. (1973). “Measurements of the structure of the Reynolds stress in a turbulent boundary layer.” J. Fluid Mech., 60(3), 481–511.
Manhart, M. (2000). “The directional dissipation scale: A criterion for grid resolution in direct numerical simulations.” Advances in turbulence VIII, CIMNE, Barcelona, 667–670.
Miyake, Y., Tsujimoto, K., and Agata, Y. (2000). “DNS of a turbulent flow in a rough-wall channel using roughness elements model.” JSME Int. J., 43(2), 233–242.
Moin, P., and Mahesh, K. (1998). “Direct numerical simulation: A tool in turbulence research.” Annu. Rev. Fluid Mech., 30, 539–578.
Nezu, I. (1977). “Turbulence structure in a open channel flow.” Ph.D. thesis, Kyoto Univ., Kyoto, Japan.
Nezu, I., and Nakagawa, H. (1993). Turbulence in open-channel flows, Balkema, Rotterdam, The Netherlands.
Orszag, S. A., and Patterson, G. S. (1972). “Numerical simulation of three-dimensional homogeneous isotropic turbulence.” Phys. Rev. Lett., 28(2), 76–79.
Raupach, M. R., Antonia, R. A., and Rajagopalan, S. (1991). “Rough-wall turbulent boundary layers.” Appl. Mech. Rev., 44(1), 1–25.
Singh, K. M., and Williams, J. J. R. (2005). “A parallel fictitious domain multigrid preconditioner for the solution of Poisson equation in complex geometry.” Comput. Methods Appl. Mech. Eng., 194(45–47), 4845–4860.
Sumitani, Y., and Kasagi, N. (1995). “Direct numerical simulation of turbulent transport with uniform wall suction and injection.” AIAA J., 33(7), 1220–1228.
Thomas, T. G., and Williams, J. J. R. (1995). “Turbulent simulation of open channel flow at low Reynolds number.” Int. J. Heat Mass Transfer, 38(2), 259–266.
Wu, F.-C., and Yang, K. H. (2004). “Entrainment probabilities of mixed-size sediment incorporating near-bed coherent flow structures.” J. Hydraul. Eng., 130(12), 1187–1197.
Information & Authors
Information
Published In
Copyright
© 2007 ASCE.
History
Received: Sep 20, 2004
Accepted: Sep 14, 2006
Published online: Apr 1, 2007
Published in print: Apr 2007
Authors
Metrics & Citations
Metrics
Citations
Download citation
If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download.