Photo: CeSOS

How do 1000 tonnes of liquid petroleum behave inside the tank during a storm? What happens when a wrecked ship starts to take in water? How can a vessel be steered automatically and consult its own weather forecasting service? These are the sort of questions that are answered by researchers in marine technology.

A drama between forces
Marine industry, transport and resource exploitation are changing. The shipping industry wants faster ships, the aquaculture industry is heading for a boom, the energy sector is opening for drilling in deep waters and the vulnerable Arctic areas. All of these fields offer major opportunities, but at the same time represent enormous challenges related to financial matters, scientific and technological competence as well as safety and environment issues.

CeSOS provides fundamental, new knowledge about how ship structures, oil installations and all other marine structures can be exposed to loads from waves, ocean currents, ice, and wind. The Centre investigates the physics of the drama taking place between natural forces and the human-made structures in a marine environment. Its wide range of research projects are organized in three scientific areas of marine technology: hydrodynamics, structural mechanics and automatic control.

From a social perspective this gives the marine industry and the authorities the opportunity to build and approve structures that are strong, ecologically friendly, cost-effective and thereby create jobs both on shore and at sea.

Photo: Paul Sigve Amundsen/NTNU Info

Norway – the ocean – shipping and oil
As a natural consequence of its extended coastline, Norway has been a shipping nation for centuries and today the country holds an internationally leading position within shipbuilding, advanced shipping equipment, and offshore petroleum technology. As much as 5% of Norwegian industry is related to technology focused on the development and production equipment for shipping and the oil industry. With oil and gas as its most important natural resource, Norway has built up qualifications that could benefit the entire world.

The Norwegian University of Science and Technology (NTNU) places great emphasis on research and education in marine technology, energy and petroleum, and it supplies the shipping and oil industries with highly trained researchers within numerous fields of specialization. These are the researchers who in turn contribute to the development of companies such as Statoil, Hydro, and Det Norske Veritas.

Researchers crossing oceans
CeSOS is a very international research environment, and prioritizes international contact and projects in cooperation with selected researchers and marine technology environments abroad. Staff at CeSOS have an international profile as only 50% come from Norway. In total, about 20 different countries are represented, including China, Indonesia, Italy, Russia, and the USA.

“ Two key people at the Centre, Professor Torgeir Moan and Professor Odd M. Faltinsen both hold such strong positions in the international academic environment that we easily attract visiting researchers," said Carl Martin Larsen, professor in structural engineering. Our cooperation with MIT in Boston is particularly strong with four visiting professors often travelling across the Atlantic to Trondheim. Many people want to come here because of the unique laboratory facilities.

Photo: CeSOS

Huge ocean basin laboratory and 260 metre-long towing tank
When the gates open and reveal the ocean basin laboratory, it looks like a large film studio. Through cooperation with SINTEF MARINTEK, CeSOS has access to large tanks to conduct experiments and create waves, currents and wind, all in controlled conditions. With an ocean basin measuring 80x50 metres and a towing tank of 260 metres, the conditions are excellent for experiments using models in a relevant scale for reality, such as 1:20.

One of these experiments with ship models in the towing tank led to one of CeSOS’s most sensational conclusions in 2006. The vibrations in the hull of a ship increase with the size of the waves – and making the bow as hydrodynamic as possible does not help. Round or pointed, with or without wave-absorbing devices, these vibrations will cause fatigue and have resulted in cracks in brand new tankers.

“Ideal structures from an engineering perspective require the least possible resources during construction at the same time as they meet all safety requirements,” said Torgeir Moan, Director of the Research Centre.

In the ocean basin, computers generate waves from all sides, and the laboratory provides opportunities for complex experiments with anything from new types of platforms, aquaculture equipment and ship manoeuvring to floating structures. Carrying out experimental programmes in the ocean basin laboratory is so expensive that industry is the primary contractor, but CeSOS has access to the results from the measurements, which enables researchers to improve their own calculation models.

Photo: CeSOS

Plunging and sloshing – the physics of liquid fluids
CeSOS primarily develops mathematical models and statistic methods to describe the physics of what happens when structures are exposed to extreme loads.

Imagine a wave breaking against the hull and flowing onto the deck. The water rises as a vertical wall on one side of the deck before washing at high speed across to the other side. Perhaps tearing down equipment or damaging important parts of the structure in the process. These are called non-linear wave forces and are studied by methods similar to hammer force and the dam break effect.

Have you ever carried water in an open bucket and tried to keep it there while running? The water pitches and hits the sides before eventually sloshing over. The water moves in a dancing rhythm that reinforces itself. The same dance occurs aboard huge tankers sailing across oceans. Many of them carry liquefied natural gas (LNG) that will supply cities with heat and light. We are talking about intense rhythms here, because the tanks are loaded with 1000-150 000 tonnes of boiling energy. This is called sloshing and is a priority research area at CeSOS.

CeSOS’s research methods are primarily analytical and mathematical. The researchers calculate the probability of events occurring before developing methods to handle the events. One look at the sea tells you that waves are random. If you observe an area long enough, you will discover that the wave height is rather unpredictable. The advantage with stochastic mathematical models is that they can describe reality as accurately as possible, because they include the aspect of unpredictability.

Marine technologists go deeper into this theory. Instead of calculating random waves indefinitely, they concentrate on finding an extreme wave or one particular wave height suitable for generalization. One such mathematical ideal could for instance be defining when a 100-year wave will occur.

”We are looking for computer programs that we can use more generally. If they work, they can also be used for other studies of the phenomena without experiments with models,” Torgeir Moan explains.

Research projects within structural engineering investigate what gives strength. Which shape is ideal for instance for a pentamaran, a tanker or a cruise ship? Oil and gas production is moving into deeper waters, but we know very little about how ocean currents affect pipelines, risers, and seabed installations. Research on the mechanics of slender marine structures could gradually provide the answers.

Illustration: CeSOS

The future at sea – floating airports and flexible fish farms
The future will look different. We envisage huge farms for fish and seafood. Perhaps we will be crossing straits and channels using large floating barges instead of bridges. We will be building floating airports and fast and light multihull vessels, tidal-power stations, and wave-power stations. These topics are being discussed in large fishing and shipping nations such as Japan, Norway, and the USA. CeSOS cooperates with the Megafloat Programme in Japan, and the Mobile Offshore Base Programme in the US.

Fish farms must be able to withstand powerful forces at sea and be towed from place to place, for instance to get away from algal bloom in the upper waters. The aquaculture industry also needs new vessels, new types of harvesting tools, and a totally new infrastructure for transport and processing. The challenges are numerous – this is a field where we need fundamental qualifications, and brand new ideas.

For this reason, CeSOS arranges creative workshops with innovative researchers such as Robert Skelton from the University of California, San Diego, to generate ideas for new projects. He is working on new types of structures, transferring principles from biology to marine technology. “Traditionally we have thought in terms of large and robust, but why not go in the opposite direction: flexible and adaptable? asks Professor Skelton. “The wing of an insect, which is lighter than a feather, can stand enormous wind loads compared to its size.” The term ‘tensigrety’ is new within marine technology and CeSOS is going to explore it.

Never again – major accidents at sea can be prevented
If we want safe workplaces at sea, the key words are reliable structures. The list of safety premises also includes well-functioning machinery, fire prevention, navigation and communication equipment, and rescue equipment, but the single most important factor is a hull or platform that can withstand sea loads.

After the catastrophic accident in 1980 when the accommodation platform Alexander Kielland capsized and 123 people were killed, safety research in Norway was intensified. The disaster was a turning point for the marine industry. Professor Moan was a member of the commission of inquiry that discovered that a minor structural defect – basically a trifle – led to the entire platform capsizing.

”Since then, we have introduced a system of testing for accidental loads before starting the production of ships and platforms. That means that damage to one part of the structure should never lead to a total collapse. Defects occurring more than once per 10 000 years are to be eradicated. We investigate what may happen and map how to prevent it from happening. In this way, research and cooperation on regulations function as a basis for safety at sea. DNV and other classification societies continuously cooperate with the research environment at CeSOS,” concludes Torgeir Moan.