An Experimental and Numerical Investigation of Flow Characteristics Around Bridge Abutment

The flow's velocity field with the lateral contraction and expansion in an open channel around bridge abutment was measured with laser Doppler anemometry (LDA), and the free-surface profile was determined using a limnimeter for two flow discharges. Basic equations of fluid flow are solved by the ANSYS Fluent program based on the finite volume method for the same experimental flow conditions. In the numerical simulations, the detached eddy simulation (DES) model is used to simulate the turbulence, and the free-surface profile is calculated using the volume of fluid method (VOF). Computational results for free-surface profiles and horizontal velocity component are compared with measured data for the two cases. The length of the separation zone formed in the downstream region of the bridge abutments is considerably larger than in the upstream region. The length of this region downstream (L-s) is greatest at the channel bottom and is approximately 14 d (d: length of the bridge abutment perpendicular to the flow). The thickness of the separation zone was similar around both piers. In the contraction region, the horizontal maximum velocity component (u(max)) occurred at z/z(max) = +/- 0.5, not in the central axis. Moreover, the u(max) is larger in the downstream region than in the upstream region, u(max) = 1.5u(o) and u(max) = 2u(o) for Cases 1 and 2, respectively. The experimental and numerical results indicate that the DES model accurately predicts the velocity field and free-surface profiles under the present flow conditions.