Higher-order turbulence around simple and complex piers using Particle Image Velocimetry

Abstract

The objective of this study is to explore the higher-order turbulence statistics of flow and turbulent length scales around a complex pier (CP) and compare the results with that of a simple pier (SP). The velocity data were recorded in a laboratory flume using Particle Image Velocimetry (PIV). The PIV data were analyzed to estimate the velocity fluctuations of third-order, turbulence production, and dissipation rates, turbulent length scales and the contributions of burst-sweep events to the total Reynolds shear stress around the piers mounted on a rigid flat surface. The skewness and advection coefficients indicate a more asymmetric distribution of velocity fluctuations for SP than that of CP. The ejection and sweep events illustrate the dominance of similar strengths for an extended period, downstream of the piers. The upstream TKE production was similar for both the piers, while the upstream dissipation rate is higher for CP than SP. The length scales show greater values at the upstream and lower values at the downstream of SP than CP. The findings show the importance of the pile-cap in restricting the downward moving flow by showing a lower magnitude of scour-causing turbulence parameters for CP than SP.