Abstract:
Bulbous bow (or bulb at the bow) is designed below the water line to modify
the flow of water around the hull, probably will cancel out or reduce the bow
pressure wave systems. The aim of this project is to investigate the effect of
the bulbous bow shape to the wave drag of a 28.3m Trawler/Purse Seiner.
The prediction of resistance was conducted using CFD simulation by using
SHIPFLOW CFD code developed by of FLOWTECH International AB. In
order to find the optimized design of the bulbous bow shape, there are three
parameters were laid out and studied by using Kratch (1978) design bulb
approaches. The three parameters are the protruding length, LPR, bulb
breadth, BB, and bulb height, ZB. The aim of the study is to improvise the
bulbous bow shape design by changing the parameters to get the minimum
resistance result, and quantify the resistance of the trawler upon the
installation of bulbous bow in model and full scale. There were 8 different
bulbous bow shape configurations. All the 8 different configurations were
compared in terms of its resistance in model and full scale. All the 8
difference configurations were simulated using full RANS equations for speed
of 7 to 15 knots. The free surface of the water was modelled using panel and
volume of fluid (VOF) method. A grid dependence study was conducted to
determine the best grid cell resolution and it was chosen at a total of
2469746 cells. The bare hull resistance of trawler was validated with
experiment data from UTM’s towing tank results. All the bulbous bow shape
designs were modelled using Maxsurf and Rhinoceros 3D software, and
settings in SHIPFLOW. The best and worst bulbous bow design was selected
in judging its minimum drag, largest percentage reduction, wave elevations
and hull pressure distribution. It was found that the bulbous bow design TR1
by CFD is the most optimized configuration in terms of its performance
criteria as mentioned earlier and TR2 is the worst bulbous bow design.
