Current methodologies misrepresent the sloshing phenomenon, which is critical in the maritime transport of liquid hydrogen and liquefied natural gas.

The sloshing around of liquid fuels when transported in tanks represents a crucial design consideration for large cargo ships. Recently, scientists from Korea have revealed that the design parameters specified in current guidelines may not accurately represent this phenomenon. Their findings will hopefully lead to a revision of these guidelines and pave the way for safer and more efficient transportation technologies for clean fuels, including hydrogen and liquefied natural gas.

Image title: Reviewing current design guidelines for liquid cargo tanks.

Image caption: In maritime transport, the sloshing of liquid fuels in storage tanks must be seriously considered to prevent problems, such as structural failure and capsizing. However, detailed fluid dynamics simulations reveal that current design parameters do not accurately reflect the sloshing phenomenon.

Image credit: Hyun-Duk Seo from KMOU

License type: Original Content

Usage restrictions: Cannot be reused without permission.

Many countries around the world are starting to gravitate towards clean energy sources and more eco-friendly fuels, such as hydrogen and natural gas. When transported overseas by cargo ships, these fuels are maintained in their liquid state within large tanks. Carrying them as liquids is not only safer but also more efficient in terms of energy and space. However, there is an important phenomenon that ship designers and engineers should never ignore: sloshing.

When a tank carrying a liquid is only partially filled, changes in the speed and direction of the ship cause the liquid to move back and forth, much like coffee does when the cup holding it is moved suddenly. This sloshing motion can exert great pressure on the tank’s structure and create large weight shifts, which can lead to toppling. To prevent such problems, national and international maritime organizations have provided guidelines known as “classification rules,” which provide methods for calculating sloshing loads based on a series of design parameters.

However, according to a recent study conducted by researchers from Korea, these guidelines may be suffering from some serious limitations. By leveraging advanced fluid dynamics simulations, Assistant Professor Hyun-Duk Seo from Korea Maritime and Ocean University and Dr. Jae-Min Lee from Chonnam National University have investigated whether the parameters considered in classification rules adequately represent the sloshing phenomenon. Their study was made available online on July 17, 2023, and published in a Special Collection of the journal Physics of Fluids on Recent Advances in Marine Hydrodynamics.

The researchers employed a technique known as smoothed particle hydrodynamics, which represents a fluid as a collection of individual particles. Using this method, they conducted several simulations involving different tank sizes, loads, and bulkheads―internal walls with holes used to create partitions inside tanks, which helps minimize sloshing.

Interestingly, the simulations revealed many aspects of sloshing that the design parameters specified in classification rules failed to represent accurately. Notably, bulkheads having different hole geometries but yielding the same parameter values resulted in considerably different liquid surface profiles, pressure distributions, and fluid velocities. “Based on the obtained results, it is evident that the classification rules do not consider the impact of the design parameters in sufficient detail,” highlights Dr. Seo. “Therefore, it is necessary to revise these guidelines so that they address these limitations and ensure the reliable design of liquid cargo tanks.”

Further work will be needed to incorporate these newfound insights into current design methodologies for liquid cargo tanks. This, in turn, would not only help prevent catastrophic accidents but would also lead to optimal tank designs to make maritime transport cheaper. Dr. Seo highlights: “Our research will pave the way to a better understanding of existing classification rules and their limitations. Ultimately, we aim to contribute to the development of cost-effective and safe technologies for transporting essential energy resources used in daily life.”

With any luck, this study will serve as a major step towards efficient fuel transportation and a more sustainable future!

Reference

About National Korea Maritime & Ocean University

South Korea’s most prestigious university for maritime studies, transportation science and engineering, the National Korea Maritime & Ocean University is located on an island in Busan. The university was established in 1945 and since then has merged with other universities to currently being the only post-secondary institution that specializes in maritime sciences and engineering. It has four colleges that offer both undergraduate and graduate courses.

Website: http://www.kmou.ac.kr/english/main.do

About the author

Hyun-Duk Seo is an Assistant Professor of the Department of Naval Architecture and Ocean Systems Engineering at Korea Maritime and Ocean University (KMOU). Before joining Korea Maritime and Ocean University, Dr. Seo worked at the research institute of Korea Electric Power Corporation (KEPCO). His research group is investigating design parameters related to liquid storage tanks for the transportation of energy sources such as oil, liquefied natural gas, and hydrogen. They are also developing computational methods to analyze fluid and structural dynamics in engineering fields.