VOID FRACTION IN HIGHLY UNSTEADY AIR-WATER FLOWS

Highly unsteady flows, characterized by long-period, high- translatory waves, are common in nature. They describe coastal phenomena like tsunamis, storm surges, and flood waves, as well as more inland events such as tidal bores and dam failures. Recent incidents have shown that these phenomena significantly threaten densely populated coastal and riverine areas, with their frequency increasing globally due to climate change and sea level rise. Therefore, obtaining a deeper understanding of the physical processes behind their hydrodynamic behavior is necessary. This experimental study analyzes multi- phase characteristics in the breaking roller under various hydrodynamic conditions. Since the analogy with dam- break waves is commonly used to describe unsteady long-period wave phenomena (Chanson et al., 2003), this study focuses on the air-water flow properties of dam- break waves over varying tailwater depths, with a specific focus on the void fraction distribution.