design of bulb parameters has also been briefly examined. The results of this study are presented in the form of design parameters related to main hull parameters for a set of input data in a narrow range. The first six parameters have been derived by re-correlation with statistical analysis and the seventh parameter by reanalysis of an approximate linear theory with sheltering effect for resistance estimation. Finally, a design example, which includes tank test results, of an additive bulbous bow for a container ship has been presented.
AbstractAlthough in modern times, bulbous bows have become an integral part of commercial ships, the hydrodynamic design of bulbous bows is still difficult because of costly tank tests and patent-driven knowledge banks. The design of a bulbous bow is needed even at the preliminary design level to predict speed and power. In this work, a design method is presented that combines and extends two famous theories i.e., Kracht (1978a) and Yim (1980) for a particular set of requirements within a narrow range of parameters. The method uses a reanalysis of an approximate linear theory with sheltering effect for resistance estimation, and re-correlation with statistical analysis via a non-linear multivariate regression analysis from existing literature and tank test results available in the public domain. The optimization of design parameters has been done for the design speed. The effect of change in the speed has been discussed and suitably incorporated in the design process. In the present work, the effect of production constraints on the
T E C H N I C A L P A P E RNAVAL ENGINEERS JOURNAL WINTER 2005 5 7 NOMENCLATURE ABL = area of ram bow in longitudinal direction, m 2 ABT = cross-sectional area at forward perpendicular (FP), m 2 AMS = mid-ship sectional area, m 2 BB = maximum breadth of bulb area A BT , m BMS = breadth of ship at mid-ship section, m CB or Cb, CM, CP, CPE, CWL = block, mid-ship, prismatic, entrance prismatic, waterplane area coefficients respectively CF, CR = frictional and residual resistance coefficients respectively CP R, ∆CP R = residual power displacement, residual power displacement reduction coefficient respectively CABL = lateral parameter CABT = cross-sectional parameter CBB = breadth parameter CLPR = length parameter C ∀PR = volumetric parameter in percentage distributed forward of FP CZB = depth parameter CCG = volumetric longitudinal distribution parameter C∀BTOT = volumetric parameter distributed aft and forward of FP Fn = Vs/ √ g• LLWL = Froude number FP = forward perpendicular HAP, HFP = draft at AP, and FP respectively H = average draft, B = average breadth of ship H1 = H/LLWL H B = height of A BT , m ∆ ∆