Turbulence flow field around two eccentric circular piers in scour hole

ABSTRACT

Flow pattern at single pier has been extensively studied by several investigators, but scanty work is available on turbulent flow pattern around piers placed in close proximity. The work explained in this research is concerned with an experimental study of the horseshoe vortex flow pattern and characteristics in a local equilibrium scour hole around two identical circular piers placed in the longitudinal direction to the flow with an eccentricity (transverse distance). Instantaneous three-dimensional velocities were measured by using an acoustic Doppler Velocimeter (ADV). The contours and distributions of the time-averaged velocity components, turbulence intensities and turbulence kinetic energy are presented at different azimuthal planes: 0°, 45°, −45°, 90° and −90°. Velocity vectors obtained from time-averaged velocity fields are used to show further flow features. The vorticity and circulation of the horseshoe vortex are determined by using a forward difference technique of computational hydrodynamics and the Stokes theorem, respectively. The eccentric pier arrangement and the interference between the piers play an important role in the creation and formation of the greater scour depth at the eccentric rear pier. Vortex strength of the eccentric rear pier is found higher than the front pier.

Keywords:

• Open channel turbulent flow
• clear water scour hole
• eccentric pier
• longitudinal spacing
• horseshoe vortex
• circulation