Influence of Length-to-Width Ratio on Flow and Turbulence in the Wake of Piles with Elongated Cross-Sections

Elongated circular bridge piers are commonly used in hydraulic structures. Their interaction with the incident flow for varying length-to-width ratios, especially in the wake region, has not been comprehensively investigated before. In this study, the flow structure around piles, i.e., bridge piers, with elongated circular cross sections is experimentally investigated for changing length-to-width ratio values from 1 to 4 under steady flow conditions. The spatial variation of Reynolds-averaged velocity and turbulence characteristics around the piles, as well as the effect of cross-sectional shape on the flow field around the pile, were studied. Turbulent energy spectra and joint frequency distributions of velocity components were obtained. The results show that as the length-to-width ratio of the pile grows larger, the vortex shedding weakens as much as 45% in terms of lateral turbulence intensity. Furthermore, the flow contraction becomes stronger as much as two times in terms of the lateral velocity gradient for the piles with elongated cross sections in comparison to the circular cylinder. It is also concluded that although piles with elongated cross sections behave differently than circular piles, further increasing the length-to-width ratio over a certain value does not make a significant difference in the flow pattern.