Effect of hull separation ratio and various ship draft to a low-speed catamaran in shallow water

Abstract

Putrajaya is Malaysia's federal administrative capital and a well-planned city. With a display of colored boats floating across the lake at Marina Putrajaya, Putrajaya Lake is turned into a beautiful sight for everyone to enjoy it. It has a high potential to be a part of the growth and development of Malaysia‘s tourism industry. In addition, the Management of Putrajaya Lake plans to cater to recreation, fishing, water sports and water transport. Currently, there are a few catamaran cruise boats that are used for sightseeing propose. Therefore, the number of cruise boats is planned to increase in the future due to accommodating a large number of tourists. The existing design of catamarans shall be improved and fulfill the limitations of Putrajaya Lake especially the low operational speed catamarans and shallow water conditions. However, limited researches has been found for low-speed catamaran studies in shallow water conditions. In order to fulfil the research gap, the current study is focused on studying the effect of hull separation ratio, H/L of the catamaran and various ship drafts, T on the low-speed catamaran in shallow water and improving the catamaran design with better operational performance in terms of better resistance and lower operating cost. This research aims to provide a more competitive hull separation ratio, H/L for catamaran boats to operate in this low-speed condition. Then, a parametric study was conducted to identify the effect of hull separation ratio and different catamaran drafts on the low operational speed in shallow water using Computational Fluid Dynamics (CFD) software, which is Flow3D. Grid independence study and method validation were carried out in methodology. Three types of catamaran drafts were calculated with water depth to ship draft ratio, h/T for 2.5, 2.32, and 2.18 to analyse the total coefficient and free surface elevation effect. The objectives of this research were successfully achieved and the collected data is able to contribute to future development either for Putrajaya Lake Management or low-speed operation catamaran. The results showed that the smaller hull separation ratio, H/L is more suitable since lower total coefficient of resistance and free surface elevation occurred during the Froude number, Fr = 0.4 condition. Also, it recommended to use of a higher water depth to ship draft ratio, h/T due to the smaller ship draft, T showed smaller total coefficient of resistance and free surface elevation. In conclusion, this research is able to contribute valuable data for Putrajaya Lake management in improving its catamaran design in the future, as public transport operators always face challenges in producing a more environmentally friendly catamaran with commercial speed.