3-DIMENSIONAL CALCULATION OF SCOUR AROUND CYLINDERS

The flow of water around a cylinder was calculated by a numerical model. The model used a finite-volume method to solve the nontransient Navier-Stokes equations for three dimensions on a general nonorthogonal grid. The k-epsilon turbulence model was used to solve the Reynolds-stress term. The flow field gave the shear stress on the boundaries, which was used to calculate sediment concentration for the bed elements. The diffusion/convection equation for the sediment concentration was solved and continuity for the sediment concentration gave changes in the bed elevation. Using the modified bed, a new flow field was calculated, and also a new sediment concentration. This sequence was repeated until the depth of the calculated scour hole was identical to the depth of the scour hole from a physical model study. The rest of the geometry of the resulting scour hole compared well with the measured scour hole from the experimental study. Also other flow characteristics given by the numerical model were found to be in agreement with observations from the experimental study.