Flow and turbulence around an inclined pile

The present experimental study investigates the generated flow field in the presence of a bottom mounted cylinder with a downstream inclination. The experiments were conducted in an 18 m x 0.50 m x 0.50 m flume under steady flow conditions. A cylinder with a diameter of 7.5 cm served as a disturbance to the flow under several inclination angles, parallel to the flow direction. Specifically, 0o, 15o, 30o, 40o, and 50o inclination, with respect to the vertical, were tested separately under three different approach velocities. Instantaneous flow velocities were measured with an acoustic Doppler velocimeter, while the upstream separation distance in the cylinder proximity was visualized with the aid of a laser sheet. Results show that once the pile is inclined, the flow features change considerably. Generally, inclination renders the pile to be more hydrodynamic in shape with the suppression of the vortex shedding. At the same time, inclination makes the cross-sectional area of the pile to become elliptical, leading to an increase in the friction area and turbulence production on the cylinder boundary layer. Also, the upstream separation distance of the cylinder near the bed was significantly altered with the inclination, which would presumably affect the generation and strength of the horseshoe vortices to be generated due to this separation.