Experimental investigation on heated spheres entering water vertically at different temperatures

Our investigation of spheres entering water at high-temperature reveals that elevated temperatures modify traditional cavitation patterns and trigger novel fluid dynamic phenomena. Experimental analysis of the high-temperature sphere’s water entry process has identified four distinct cavitation morphologies: small cavities, complete cavities, dual cavities, and unstable cavities. These phenomena result from the sphere’s thermal effects altering the local flow dynamics around it, consequently impacting the hydrodynamic coefficients. Notably, thermal conditions cause the contact line from the sphere’s midpoint to transition to its tail, leading to transformations in cavity types. Furthermore, simulations employing the lattice Boltzmann method elucidate how unstable steam films formed on hot surfaces induce boundary slip, reducing pressure drag. This observation provides further insight into established mechanisms of fluid drag reduction. Our study deepens the understanding of how temperature influences water entry dynamics and offers new perspectives on reducing drag during the water entry process of objects.