American Society of Civil Engineers


Numerical Modeling of Abutment Scour with the Focus on the Incipient Motion on Sloping Beds


by Hans Bihs, (corresponding author), (Dept. of Hydraulic and Environmental Engineering, Norwegian Univ. of Science and Technology, S.P. Andersenveg 5, 7491 Trondheim, Norway. E-mail: hans.bihs@ntnu.no) and Nils Reidar B. Olsen, M.ASCE, (Dept. of Hydraulic and Environmental Engineering, Norwegian Univ. of Science and Technology, S.P. Andersenveg 5, 7491 Trondheim, Norway.)

Journal of Hydraulic Engineering, Vol. 137, No. 10, October 2011, pp. 1287-1292, (doi:  http://dx.doi.org/10.1061/(ASCE)HY.1943-7900.0000401)

     Access full text
     Purchase Subscription
     Permissions for Reuse  

Document type: Technical Note
Abstract: A three-dimensional computational fluid dynamics model is applied to predict local scour around an abutment in a rectangular laboratory flume. When modeling local scour, steep bed slopes up to the angle of repose occur. To predict the depth and the shape of the local scour correctly, the reduction of the critical shear stress due to the sloping bed must be taken into account. The focus of this study is to investigate different formulas for the threshold of noncohesive sediment motion on sloping beds. Some formulas only take the transversal angle (perpendicular to the flow direction) into account, but others also consider the longitudinal angle (streamwise direction). The numerical model solves the transient Reynolds-averaged Navier-Stokes equations in all three dimensions to compute the water flow. Sediment continuity in combination with an empirical formula is used to capture the bed load transport and the resulting bed changes. When the sloping bed exceeds the angle of repose, the bed slope is corrected with a sand-slide algorithm. The results from the numerical simulations are compared with data from physical experiments. The reduction of the bed shear stress on the sloping bed improves the results of the numerical simulation distinctly. The best results are obtained with the formulas that use both the transversal and the longitudinal angle for the reduction of the critical bed shear stress.


ASCE Subject Headings:
Bridge abutments
Scour
Numerical models
Slopes
Computational fluid dynamics technique
Flumes

Author Keywords:
Abutment
Local scour
Numerical modeling
Incipient motion