Hydrodynamic Analysis and Propulsive Arrangement of Two Corvette Hulls with Different Operational Profiles

Abstract

This paper presents a few hydrodynamics analyses of two corvette hulls with different operational profiles (corvette 1 with maximum maintained speed of 25 knots and corvette 2 with 35 knots), which designs follow some Brazilian Navy high-level system requirements and are based on modern world military vessels. The total resistance coefficient and wave pattern were determined from computational fluid dynamics simulations using free surface models and ITTC procedures, and the form factors of both ships by Prohaska’s method and CFD simulations at low Froude numbers (to neglect the wave resistance). A preliminary numerical analysis of bulbous bow was carried out using CFD, and it was possible to notice that, at high Froude numbers, the ship resistance substantially decreased if compared to the bulbless hull and, with low Froude numbers, the resistance subtly increased. Moreover, the propulsive arrangements of both ships were predimensioned and it was possible to notice the differences due to the operational profiles. Corvette 1 has a combined diesel and diesel propulsion system with two controllable pitch propellers, which optimum pitch was defined using the OpenProp software and the wake field from CFD. Corvette 2, which has a broader range of speed, has a propulsive arrangement of two waterjets and a gas turbine at high speeds, and a CPP with diesel engines when operating at low speeds.