The effect of pier geometry on scour potential has been widely studied and recognized. Based on the classic excess shear stress theory, our previous study demonstrated that pier streamlining would significantly reduce the local scour potential, and thus it can potentially serve as an alternative scour countermeasure. However, the RANS method employed in our previous study inherently fails to capture the coherent dynamics of turbulence around pier, which also plays an important role in scour mechanism. With the more advanced DES method in this paper, the coherent turbulence structures in the vicinity of pier are captured and the computed results are compared among different cases systematically. Comparison of simulation results reveal significant variations of the flow physics with pier streamlining features in terms of coherent structure dynamics, turbulence statistics, and bed shear stress distribution. The bimodal dynamics of horseshoe vortex (HSV) system is captured by the DES model, as has been observed by many experimental studies. Findings of this study confirm that streamlined pier geometry helps reduce the dynamic turbulence intensity and therefore can serve as a scour countermeasure alternative.
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