Flat plate bow covers pave way for more economical shipping by improving ship aerodynamics

Marine transportation accounts for over 80% of international trade. It is facilitated by superstructures, such as passenger ships, container ships, oil tankers, and roll-on–roll-off car ferries, making it efficient and effective. Nevertheless, there is an ever pressing need to make shipping more economical. In this regard, scientists have conducted numerous studies to improve the aerodynamic performance of ships, which face significant drag force from winds on their above-water hull— the visible body of the ship—when sailing.

Recently, an international cooperation research group—comprising Dr.Ngoc-Tam Bui, an Assistant Professor at the College of Systems Engineering and Science at the Shibaura Institute of Technology and Dr. Ngo Van He and Dr. Ngo Van Hien, Associate Professors from Hanoi University of Science and Technology—has simulated and compared different bow (the front of the hull) covers, which reduce the total wind drag acting on ships. Their work was made available online on 31 January 2023 and published in Volume 270 of the Ocean Engineering journal on 15 February 2023.

Prof. Bui briefly explains the research methodology. “This work utilized ANSYS-Fluent, a commercial software, for performing computational fluid dynamics (CFD) simulations. Herein, a small passenger ship (with and without a bow cover) and its surroundings were divided into millions of elements using a mesh—a numerical grid. Then, 'Reynolds-averaged Navier–Stokes equations,' which represent time-averaged fluid flow motion for each element, were solved using a turbulent viscous model. Their combined results yielded the wind drag acting on the ship’s above-water hull.”

The researchers found that a finer mesh gave more accurate results, with 23.62 million elements as an optimum number. In addition, a model called 'detached-eddy-simulation (DES) k-ε' yielded the lowest wind drag out of the five turbulent viscous models tested in this work. Using the optimum mesh and DES k-ε model, the researchers performed CFD simulations for seven flat plate-shaped bow covers of different lengths and heights, as well as a conventional streamlined cover. “The dynamic pressure region around the bow and the wind drag reduced drastically with increasing height of the flat plate cover. The ship faced 38.71% lower total drag with a 2.4 m-high bow cover than a 0.37 m-high one. This value is similar to the 42.41% reduction for a ship with the streamlined cover,” highlights Prof. Bui.

In this work, the researchers also highlight the effect of wind direction on the aerodynamic performance of a ship. The drag is the highest, irrespective of the bow cover when the wind blows at an angle of 20^o to the ship’s direction. Further, it is almost zero for 90^o. At larger angles, the wind drag reverses direction, aiding the ship’s movement.

Discussing the future potential of the present work, Prof. Bui says, “The proposed flat plate bow cover is simple to manufacture and reduces the wind drag acting on a ship almost as well as a streamlined cover. Thus, it will improve the aerodynamic performance of small passenger ships, resulting in greater fuel oil savings and economic efficiency in marine transportation.”

The findings of this work could prove useful for ship designers and engineers to optimize fuel consumption, thereby leading to more economical shipping.

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Reference

DOI: https://doi.org/10.1016/j.oceaneng.2023.113622

About Shibaura Institute of Technology (SIT), Japan
Shibaura Institute of Technology (SIT) is a private university with campuses in Tokyo and Saitama. Since the establishment of its predecessor, Tokyo Higher School of Industry and Commerce, in 1927, it has maintained “learning through practice” as its philosophy in the education of engineers. SIT was the only private science and engineering university selected for the Top Global University Project sponsored by the Ministry of Education, Culture, Sports, Science and Technology and will receive support from the ministry for 10 years starting from the 2014 academic year. Its motto, “Nurturing engineers who learn from society and contribute to society,” reflects its mission of fostering scientists and engineers who can contribute to the sustainable growth of the world by exposing their over 8,000 students to culturally diverse environments, where they learn to cope, collaborate, and relate with fellow students from around the world.

Website: https://www.shibaura-it.ac.jp/en/

About Assistant Professor Ngoc-Tam Bui from SIT, Japan
Ngoc-Tam Bui is an Assistant Professor at the College of Systems Engineering and Science at the Shibaura Institute of Technology (SIT) in Japan. He received a master’s degree from Hanoi University of Science and Technology (HUST), Vietnam in 2011 and Ph.D. in Engineering Optimization from SIT in 2015. Prof. Bui also he works as a lecturer at the School of Mechanical Engineering at HUST. Over the last decade, he has authored 70 research publications, which have been cited 145 times. His research interests include design optimization, artificial neural networks, manufacturing technology, multi-objective optimization, and computational intelligence. 

Funding Information
This research is funded by Vietnam National Foundation for Science and Technology Development (NAFOSTED).