Numerical Investigation of Flow Pattern, Bed profile and Shear Stress around the Rectangular Bridge Pier Using Flow 3D

One of the complicated phenomena in sediment hydraulic engineering is scouring around bridge pier. Regard to three-dimensional and complicated flow pattern around piers, measuring some hydraulics parameters during the tests such as flow pattern, variation of bed profile and shear stress are difficult, in this situation application of numerical models in order to extract results and more detailed study is useful. Aim of this research is numerical modeling of flow pattern, variation of bed profile and scour depth and shear stress around rectangular pier using Flow 3D and applying the results to protect piers against scouring. Results showed, for aligned pier with flow, shape of scour hole and flow pattern were symmetrical, the side in contact with flow is high-pressure and the other side is low-pressure. As increase of pier angle, shear stress in front of the pier increased so that for pier with 10° angle with flow direction, shear stress was 0.55 N/m2. Also fluctuations of bed profile and water surface increased. Application of submerged vanes, changed scour pattern and moved sediment in front of pier which scouring was reduced. Increase of height and angle of submerged vanes improved their protective role. Base on the results of numerical model, after 30 minutes, scour depth in front of pier in aligned pier with flow and angle of submerged vanes 30°, in same level with bed, 1.25 cm and 2.5 cm on the bed, was 3.1 cm, 0.035 cm and +0.005 cm (on the bed), respectively. As increase of pier angle, performance of submerged vanes to control scouring in front of pier and in side of high-pressure wall decreased, but in side of low-pressure wall scouring compared with alone pier was less.