Open-channel turbulent flow through bar racks

The paper reports on an experimental study of turbulent open-channel flow near small-scale and large-scale bar rack models. The experiments were conducted for a wide range of bar depth, bar shape, bar spacing and bar inclination to the approach flow. The contours of the mean velocity near the small-scale models revealed that bar inclination produced asymmetric flow, a potential threat for vibration failure. The reconstructed fluctuating velocity fields obtained from proper orthogonal decomposition revealed strong organization of vortical structure downstream of the aligned bars compared to the inclined bars. The head loss coefficient generally increased monotonically with blockage ratio and bar inclination. Significant reduction in head losses was observed when square leading edges of rectangular bars are replaced by round leading edges, or if streamlined profile cross-section bars were used instead of rectangular bars.