Commenced in January 2007
Frequency: Monthly
Edition: International
Paper Count: 32020
Sediment Patterns from Fluid-Bed Interactions: A Direct Numerical Simulations Study on Fluvial Turbulent Flows

Authors: Nadim Zgheib, Sivaramakrishnan Balachandar


We present results on the initial formation of ripples from an initially flattened erodible bed. We use direct numerical simulations (DNS) of turbulent open channel flow over a fixed sinusoidal bed coupled with hydrodynamic stability analysis. We use the direct forcing immersed boundary method to account for the presence of the sediment bed. The resolved flow provides the bed shear stress and consequently the sediment transport rate, which is needed in the stability analysis of the Exner equation. The approach is different from traditional linear stability analysis in the sense that the phase lag between the bed topology, and the sediment flux is obtained from the DNS. We ran 11 simulations at a fixed shear Reynolds number of 180, but for different sediment bed wavelengths. The analysis allows us to sweep a large range of physical and modelling parameters to predict their effects on linear growth. The Froude number appears to be the critical controlling parameter in the early linear development of ripples, in contrast with the dominant role of particle Reynolds number during the equilibrium stage.

Keywords: Direct numerical simulation, immersed boundary method, sediment-bed interactions, turbulent multiphase flow, linear stability analysis.

Digital Object Identifier (DOI):

Procedia APA BibTeX Chicago EndNote Harvard JSON MLA RIS XML ISO 690 PDF Downloads 515


[1] Kennedy, J. F. (1969). The formation of sediment ripples, dunes, and antidunes. Annual Review of Fluid Mechanics, 1(1), 147-168.
[2] Elliot, A. H., & Brooks, N. H. (1997). Transfer of nonsorbing solutes to a streambed with bed forms: Laboratory experiments. Water Resour. Res, 33(1), 137-151.
[3] Breusers, H. N. C., Nicollet, G., & Shen, H. W. (1977). Local scour around cylindrical piers. Journal of Hydraulic Research, 15(3), 211-252.
[4] Zilker, D. P., Cook, G. W., & Hanratty, T. J. (1977). Influence of the amplitude of a solid wavy wall on a turbulent flow. Part 1. Non-separated flows. Journal of Fluid Mechanics, 82(1), 29-51.
[5] Hudson, J. D., Dykhno, L., & Hanratty, T. J. (1996). Turbulence production in flow over a wavy wall. Experiments in Fluids, 20(4), 257-265.
[6] Cherukat, P., Na, Y., Hanratty, T. J., & McLaughlin, J. B. (1998). Direct numerical simulation of a fully developed turbulent flow over a wavy wall. Theoretical and computational fluid dynamics, 11(2), 109-134.
[7] Calhoun, R. J., & Street, R. L. (2001). Turbulent flow over a wavy surface: Neutral case. Journal of Geophysical Research: Oceans, 106(C5), 9277-9293.
[8] Meyer-Peter, E., & Müller, R. (1948). Formulas for bed-load transport. In IAHSR 2nd meeting, Stockholm, appendix 2. IAHR.
[9] Cayocca, F. (2001). Long-term morphological modeling of a tidal inlet: the Arcachon Basin, France. Coastal Engineering, 42(2), 115-142.
[10] Zgheib, N., Fedele, J. J., Hoyal, D. C. J. D., Perillo, M. M., & Balachandar, S. (2018a). Direct numerical simulation of transverse ripples: 1. Pattern initiation and bedform interactions. Journal of Geophysical Research: Earth Surface.
[11] Zgheib, N., Fedele, J. J., Hoyal, D. C. J. D., Perillo, M. M., & Balachandar, S. (2018b). Direct Numerical Simulation of Transverse Ripples: 2. Self‐Similarity, Bedform Coarsening, and Effect of Neighboring Structures. Journal of Geophysical Research: Earth Surface.
[12] Bennett, S. J., & Best, J. L. (1995). Mean flow and turbulence structure over fixed, two‐dimensional dunes: implications for sediment transport and bedform stability. Sedimentology, 42(3), 491-513.
[13] Coleman, S. E., & Melville, B. W. (1996). Initiation of bed forms on a flat sand bed. Journal of Hydraulic Engineering, 122(6), 301-310.