Three-Dimensional Mean Flow and Turbulence around a Spur Dike

This paper presents an experimental study conducted at the St. Anthony Falls Laboratory, University of Minnesota. Flow field at the neighborhood of a spur dike was measured by using a SonTek 10 MHz Acoustic Doppler Velocimeter (ADV). Time-history of velocities in all three spatial dimensions was recorded at 650 nodes near the dike. The time-averaged mean velocity and Reynolds stresses were calculated from the measurements. The results showed two counter-rotating secondary flow cells formed immediately downstream of the dike. The secondary flow cell at one side of the channel having the dike grows gradually, while the other cell decades until separated flows rejoin. These measurements clearly demonstrated the spatial distributions of turbulent normal stresses and Reynolds stresses. Additionally, bed shear stresses were calculated by using mean flow and turbulence Reynolds stresses. Bed shear stresses calculated by using Reynolds' stresses are more accurate for approximating bed shear stresses field around the dike.