Geometric Modeling and Analysis of Passenger Ship Hull Model Using FreeShip Plus

Abstract

The good quality of the parametric ship hull form model from Computer Aided Design (CAD) is indeed relevant to Computational Fluid Dynamics (CFD). The CAD must interact well with CFD to avoid too much error and problem on CFD analysis. To make a precise and an accurate geometric design of ship hull form CFD is essential because it relates to the prediction of hull performance in the CFD analysis. Thus, this research is to re-model the geometric of passenger ship hull form model (MTC 092) which was developed by Marine Technology Centre (MTC) by using CAD of open source software called FreeShip Plus. Initially, the geometric of passenger ship hull model was presented in the form of 2D lines plan drawing using AutoCAD software. Then, the lines plan drawing was imported into FreeCAD in ‘iges’ file format to undergo a digitized process by following the table of offset format. The ship hull form coordinates were next extracted into a Python script in an XYZ table which starts with ‘0’ and ends with ‘eof’. This is followedby generating the model in FreeShip Plus after importing the Python script into FreeShip Plus asa text fileusing the chine import tool in FreeShip Plus. Subsequently, FreeShip Plus generated half of the ship hull form and then exported it into Blender as an ‘obj’ file. In Blender software, the ship design process proceeded with a mirrored function then and clipped the half ship hull form into full ship hull form, after which the passenger ship hull model was saved in ‘stl’ file format. Lastly, the hydrostatic data results of the passenger ship hull model involving a set of geometric parameters in FreeShip Plus show a maximum error of 2.77% compared to the MTC 092 model in a towing tank test, thereby implying the validity and accuracy of the analysis. The significance of this study is expected to help proliferate the acceptance on the use of open source CAD Software in professional working environment.