Disturbance propagation and shock-front evolution in underwater shock diffraction around convex corners

Abstract

Underwater shock diffraction around structural corners can substantially alter shock-front geometry and redistribute pressure and impulse along nearby boundaries. Although geometrical shock dynamics (GSD) has been widely applied to air-shock diffraction, its applicability to relatively weak underwater shocks remains insufficiently established. In this study, underwater shock diffraction around a convex corner is investigated using high-resolution weighted essentially non-oscillatory simulations combined with GSD-based analysis. Three formulations are examined: the classical GSD model, the GSD model with transverse flow effects (GSDT), and the GSD model with distributed disturbance effects (GSDD). The simulations show a relatively simple flow topology, with diffraction-induced secondary structures absent or negligibly weak, such that the evolution is dominated by the curved shock front. The recalibrated GSDT model empirical coefficient kemp for underwater conditions shows a strong dependence on the post-shock flow Mach number, approaching approximately 0.76 for uI/cI ≥ 0.2. Comparison with the simulated shock-front evolution indicates that disturbance propagation characteristics vary spatially: distributed disturbance effects dominate near the triple-point (TP), the relative characteristic disturbance speed varies continuously through an intermediate transition region, and transverse flow effects dominate toward the downstream wall. Accordingly, GSDD model reliably predicts the TP motion, whereas the GSDT model satisfactorily captures the wall shock state. At sufficiently low incident pressures, the classical GSD and GSDD models predict a limiting wall angle below which the shock-front solution cannot reach the wall, whereas no such limit is obtained from the recalibrated GSDT model. The results further manifest that no single disturbance propagation mechanism can fully account for the spatial evolution of the entire curved shock front. In addition, the normalized impulse transmission coefficient is nearly independent of incident shock strength and decreases from approximately 1.0 to about 0.38 as the wall angle θw decreases from 0° to −90°.