Effect of Spray Rails on Slamming Loads in High-Speed Planing Hulls under Symmetric and Asymmetric Water Entry

Resumen

Planing hulls are widely used in high-speed patrol boats, racing vessels, and search and rescue crafts due to their ability to achieve elevated speeds by lifting the hull above the water surface. However, this hydrodynamic lift also increases the frequency and severity of slamming impacts, which can lead to structural damage, equipment malfunction, and passenger injury. While spray rails are commonly added to reduce spray and improve performance, their influence on slamming loads remains insufficiently understood. This study investigates the effect of spray rails on slamming pressures and vertical accelerations during symmetric and asymmetric water entry using a validated Computational Fluid Dynamics (CFD) model of a wedge-type planing hull section. Results show that the presence of spray rails increases slamming pressures by up to 45% in certain regions while reducing them in others, and may raise peak vertical acceleration by 38%, particularly under symmetric entry conditions. In asymmetric water entry, the pressure distribution becomes increasingly uneven with higher peaks occurring earlier on the lower side of the hull, and vertical acceleration responses become more abrupt with increasing heel angle. The findings offer new insights into the complex role of spray rails in slamming behavior, which is vital in improving performance and safety of high-speed planing vessels.