The article "The universal two-fifths law of pier scour" by Subhasish Dey and Sk Zeeshan Ali presents a breakthrough in understanding the equilibrium scour depth at bridge piers. Despite extensive research, the traditional empirical formulas have struggled to provide a unified relation for the equilibrium scour depth. The authors propose a universal law that governs the equilibrium scour depth at a circular pier embedded in a sediment bed, specifically under clear-water conditions. This law is derived from a phenomenological model and reveals that the equilibrium scour depth to pier diameter ratio follows a consistent two-fifths scaling law, incorporating a newly defined "pier-scour number" that accounts for key parameters such as approach mean flow velocity, threshold shear velocity, approach flow depth, pier diameter, and sediment grain size. The scaling law also includes an additional term involving the drag coefficient raised to the power of 2/5, which addresses the impact of the pier shape on the equilibrium scour depth. The validity of this universal law is validated through extensive experimental data on circular pier scour. The article provides a comprehensive framework for predicting and mitigating the impact of pier scour on bridge infrastructure, emphasizing the importance of considering the shape and flow conditions of the pier.The article "The universal two-fifths law of pier scour" by Subhasish Dey and Sk Zeeshan Ali presents a breakthrough in understanding the equilibrium scour depth at bridge piers. Despite extensive research, the traditional empirical formulas have struggled to provide a unified relation for the equilibrium scour depth. The authors propose a universal law that governs the equilibrium scour depth at a circular pier embedded in a sediment bed, specifically under clear-water conditions. This law is derived from a phenomenological model and reveals that the equilibrium scour depth to pier diameter ratio follows a consistent two-fifths scaling law, incorporating a newly defined "pier-scour number" that accounts for key parameters such as approach mean flow velocity, threshold shear velocity, approach flow depth, pier diameter, and sediment grain size. The scaling law also includes an additional term involving the drag coefficient raised to the power of 2/5, which addresses the impact of the pier shape on the equilibrium scour depth. The validity of this universal law is validated through extensive experimental data on circular pier scour. The article provides a comprehensive framework for predicting and mitigating the impact of pier scour on bridge infrastructure, emphasizing the importance of considering the shape and flow conditions of the pier.