PIV Measurements Around a Submerged Cylinder with Local Scour Protection

Scour and erosion have been well established as the leading causes of bridge failure in North America (Wardhana and Hadipriono 2003). As flow characteristics in natural waterways adapt to climate change, design of hydraulic structures is required to keep pace. While the investigation of empirical scour design methods is ongoing, scour mitigation techniques such as rip-rap protection, aprons and splitter vanes have been employed in practice with mounting frequency. An increased understanding of the influence of such techniques on the flow field around a cylinder in an erodible bed is required in order to develop effective design methodologies for scour protection.

When scour mitigation techniques are not employed, local scour in the vicinity of the pier progresses unimpeded until a point of equilibrium, reaching appreciable depths and posing a threat to stability. It has been shown in literature that when a plate is installed around the base of a cylinder, the erosion pattern known as horseshoe scour is mitigated and the pattern called wake scour becomes dominant (Lachaussee et al. 2018). The present study investigates the influence of certain scour mitigation features on the flow field surrounding a submerged cylinder over an erodible bed.

An experimental investigation to this end was carried out at the University of Windsor in Windsor, Canada. Experiments were conducted in a horizontal flume with a test section of granular material. Local scour was investigated around a submerged cylinder of specified diameter and flow submergence. Results for a submerged cylinder were compared with the results for a submerged cylinder with a plate surrounding the base of the pier in the horizontal plane as well as those for a submerged cylinder with a fin in the vertical plane. Planar Particle Image Velocimetry (PIV) measurements were obtained for the central, near-cylinder and mid-cylinder-wall vertical planes, from the upstream extent of the scour hole to the downstream extent of the primary deposit in the wake of the cylinder. Comparison of flow characteristics in each plane will be carried out and presented.

References: 1. Lachaussée, F., Bertho, Y., Morize, C., Sauret, A., & Gondret, P. (2018). Competitive dynamics of two erosion patterns around a cylinder. Physical Review Fluids, 3(1), 012302. 2. Wardhana, K., & Hadipriono, F. C. (2003). Analysis of recent bridge failures in the United States. Journal of Performance of Constructed Facilities, 17(3), 144-150.