First Principles‐Based Approach for 3D Scour Processes Under Variable Jet Discharge

Abstract Scour processes caused by plunging jets are particularly important in hydraulic engineering because of the connected risk of structural failure. Therefore, many investigations have been conducted on this topic, focusing on jet‐induced scour under constant flow discharge (i.e., steady case). Yet, to the best of the authors' knowledge, no studies have analyzed the scour mechanism under variable jet discharge (i.e., unsteady case) and clear‐water conditions. Following recent theoretical advancements on scour phenomena for steady cases based on the phenomenological theory of turbulence, we address in this study the general validity of such an approach for time‐dependent (i.e., unsteady) jet inflow conditions, in non‐cohesive soils. Results show that scour evolution is consistent with that obtained for steady jet flows. In particular, they confirm the existence of two distinct phases—developing and developed—and indicate that the transition time between the two phases does not depend on the jet inflow characteristics. Once again, this study confirms that the phenomenological theory of turbulence is a valid tool for all jet‐driven scour problems.