A BULBOUS BOW DESIGN METHODOLOGY FOR HIGH-SPEED SHIPS

A methodology for designing bulbous bows for high-speed, fine-form ships is proposed. Using the Kracht bulbous bow design curves developed for low-speed, full-form ships as a starting point, a series of bulb forms is developed and analyzed, using a combined numerical and experimental approach to ascertain resistance and seakeeping characteristics. This study was performed using the FFG-7 class of naval frigates as the reference hull form. Nine variations in bulb design plus the bulbless hull form were analyzed, using the DTNSRDC's XYZ Free Surface Program. Five of the bulb variations were appended to a model of the FFG-7 and tested in the 116-m (380 ft) towing tank at the U.S. Naval Academy. The results from the computer predictions and the calm-water towing tank tests show remarkably similar trends, while the relative rankings of the bulb forms derived from these analytical procedures were identical. Furthermore, the addition of a bulbous bow to the FFG-7 hull form appeared only marginally to degrade the ship's seakeeping characteristics.