Flow-Field Complexity and Design Estimation of Pier-Scour Depth: Sixty Years since Laursen and Toch

This paper, written to celebrate the 60th anniversary of the Journal of Hydraulic Engineering, presents a structured, contemporary approach to scour-depth estimation that matches design method practicality to pier flow-field complexity. The approach involves a mix of semiempirical formulation, advanced experimentation aided by new instruments, and computational fluid dynamics (CFD). Highly useful for understanding complex pier flow fields, CFD holds patent promise for substantial use in design estimation of scour depth. Presently, however, CFD's limited ability to simulate erosion and scour at a pier foundation hampers CFD's practicality for design estimation of pier-scour depth. The writers reflect back 60 years when Laursen and Toch's milestone publication provided major insights into pier scour, and when the hot-film anemometer first became available for investigating complex flow fields. Sixty years ago, pier flow fields were thought too complex to measure, or even visualize. The writers indicate where, today, further research into pier flow fields would benefit design estimation of scour depth. (C) 2017 American Society of Civil Engineers.