On the incipient sediment suspension downstream of three-dimensional wall-mounted obstacles.

The incipient sediment suspension downstream of thin square shaped tab with various inclination angles was studied using theoretical and experimental arguments. Sediment distribution characteristics and wake flows under various tab inclinations and incoming velocities were studied using volumetric particle tracking velocimetry and particle image velocimetry. Results indicate that sediment suspension occurred right downstream of obstacles due to enhanced local turbulent intensities. Sediment volumetric fraction was highly influenced by wake turbulent kinetic energy for low inclination angles (i.e., obstacles nearly parallel to incoming flow). However, for high inclination angles, sediment suspension was dominated and suppressed by distinct downward velocities resulting in lower volumetric fraction. Revised Rouse number, supported by flow measurements, was proposed to allow us to quantitatively depict the coupled influence of turbulent mixing load and vertical flows across various inclination angles and incoming velocities.