{"id":64671,"date":"2024-09-08T12:06:00","date_gmt":"2024-09-08T16:06:00","guid":{"rendered":"https:\/\/blogs.sw.siemens.com\/simcenter\/?p=64671"},"modified":"2026-03-26T06:52:44","modified_gmt":"2026-03-26T10:52:44","slug":"aker-solutions-creates-fish-farms-that-put-fish-first","status":"publish","type":"post","link":"https:\/\/blogs.sw.siemens.com\/simcenter\/aker-solutions-creates-fish-farms-that-put-fish-first\/","title":{"rendered":"Aker Solutions creates fish farms that put fish first"},"content":{"rendered":"\n
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How Aker Solutions leverages Simcenter’s cutting-edge CFD technology to design sustainable offshore fish farms for superior fish well-being<\/h2>\n\n\n\n

Utilizing the oceans\u2019 potential<\/h2>\n\n\n\n

It is almost ironic. Because of how the earth looks from a distance – we call it the blue planet. When astronauts look down on our home base, what is prominent is the sea. 70% of the earth’s surface is covered by water and yet today, only 2% of the food we eat stems from the ocean (Heidi K Alleyway 2019). Given that competition for land in the quest for energy, mobility, consumer goods and nutrition has made us squeeze every last drop out of our solid ground, gathering 2% of food mass from 70% of the earth\u2019s surface seems like a lost opportunity on a massive scale. \u201cThen go and catch more fish\u201d I hear you say. Well, it\u2019s no secret that despite the 2% we already consume, fish production from wild catches is already currently at its limit. Fish population in the world\u2019s lakes and oceans are already being exploited to the limit and we cannot push any further if we want to retain a sustainable source of food.<\/p>\n\n\n\n

So, tell us the solution!<\/p>\n\n\n\n

In the early days of homo sapiens, we survived by collecting, hunting and fishing. Cultivation of food production was the key disruptor to enable us to feed more people with less effort. It seemed relatively straight forward to increase productivity on soil. We understood that to gather more plant-based proteins per square meter, our strategy needed to move from collecting to growing and cultivating. Likewise, our ancient forefathers understood that a change in strategy from hunting wild animals to domesticating animals for meat was much more beneficial. At least on solid ground.<\/p>\n\n\n\n

\"Table<\/figure>\n\n\n\n
\"Total<\/figure>\n\n\n\n

Aquaculture – a fresh technology<\/h2>\n\n\n\n

Compared to those ancient disruptive moves, turning our focus back to the oceans, the strategy of cultivation to supplement wild catch seems comparably young. As such, Aquaculture, i.e., the cultivation of fish population under controlled conditions, started to play a noticeable role in fish-based protein no sooner than the 1990s (Mowi, 2023).<\/p>\n\n\n\n

However, just like for their land counterparts, the benefits of such cultivating technology in water are manifold and even superior. Aquaculture can happen either in seawater or freshwater. As fish are cold-blooded, there is no need for them to spend energy on heating and due to having a natural buoyancy by taking in air in the swim bladder, they have a significantly reduced need to fight gravity. This makes fish a very energy efficient species compared to land-living animals. And hence, farmed fish is an efficient protein source that when compared to meat-based land-grown proteins, is favorable from an environmental perspective. Food from farmed aquaculture even offers the highest protein output relative to feeding requirements, with a high level of nutrition stemming from healthy acids.<\/p>\n\n\n\n

Given the natural limitations of traditional wild catch and this line-up of benefits, it seems like a no-brainer to leverage aquaculture as a key contributor to feeding a seemingly ever-increasing population in a more sustainable way. For these reasons, projections anticipate that fish production from aquaculture will soon overtake the stagnating numbers from wild catch, in terms of mass of fish produced.<\/p>\n\n\n\n

At the same time, for numerous reasons, there is an increasing trend in the number of customers no longer accepting poorly grown food. This is true for plant-based, meat-based and likewise, fish-based-proteins. Consequently, regulations and the implementation of global quality standards demand an enhanced quality of farmed fish and of the conditions under which the fish are raised. These factors will support an ever-increasing acceptance of aquaculture and enable the industry to grow.<\/p>\n\n\n\n

But it isn\u2019t that simple.<\/p>\n\n\n\n

\"Offshore<\/span>
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Aquaculture at scale \u2013 it isn\u2019t that simple<\/p>\n\n\n\n

Just like on land there are major antagonistic forces at work when it comes to Aquaculture at scale. Despite astronauts confirming that 70 % of the earth\u2019s surface is covered by water, the first hurdle, astonishingly, is available space. The location criteria of \u2019traditional\u2019 fish farms are very specific. They need the right temperature range and sufficiently high-water quality and exchange, and on top of all that, they require protection from the wild open oceans and their harsh conditions, so the huge area of potential locations quickly shrinks to limited shorelines. Immediately you find yourself in competition with other industries, and interests – like recreational activities or just scenery, that claim that space. If you look at Norway\u2019s coastline the capacity for aquaculture is almost fully exploited.<\/p>\n\n\n\n

The second caveat: environmental impact due to emissions. Like any other animal, fish produce waste and this waste needs to be taken care of, especially if you want to grow sustainable food at scale.<\/p>\n\n\n\n

Thirdly, and tightly coupled to waste production, the fish\u2019s welfare is of paramount importance in aquaculture. Not just from an ethical perspective but also from a plain business perspective. Tightly packing in a swarm of fish is not acceptable. Keeping the water fresh and oxygenated in a fish farm and allowing for enough space not only serves the quality of the produced fish, it is simply a mandatory measure to keep mortality rates under control. Another fatal factor related to the living conditions is sea lice. This tiny little parasite has become the biggest threat, specifically to salmon and even more specifically to cultivated salmon. Not only does it cause a significant business impact, but it harms the fish\u2019s welfare in an ultimately irreversible fashion.<\/p>\n\n\n\n

So, what\u2019s the solution to all those challenges? Does it even exist?<\/p>\n\n\n\n

To answer that question the aquaculture team at Aker Solutions<\/a> started from a very simple but bold idea.<\/p>\n\n\n\n

\u2018Fish first\u2019<\/p>\n\n\n\n

Based on this mantra, the team around Kristoffer Jakobsen, head of technology, aquaculture at Aker Solutions tried to answer the following questions: All constraints aside \u2013 if we were to design a fish farm that ensures fish welfare as the paramount condition, what would it look like? Where would it be? What would be required to build and operate it? And what would it produce at which cost?<\/p>\n\n\n\n

The answer to all these questions brings us back to an equally disruptive thought:<\/p>\n\n\n\n

\u201870% – the blue surface from outer space\u2019<\/p>\n\n\n\n

In other words, offshore fish farms. Moving all traditional concerns aside, the team at Aker Solutions, took well known research seriously and gave an already existing concept another thought. Moving aquaculture to the open waters offers higher fish welfare. Open water fish farms naturally offer a more continuous exchange of water, as such they reduce the risk of parasites and diseases and are expected to significantly reduce mortality. Furthermore, first trials indicate that offshore farms are also reducing the disturbance of wild populations.<\/p>\n\n\n\n

With decades of experience in engineering offshore structures, Aker Solutions had all the know-how to come up with a first conceptual design for an offshore fish farm that would withstand the harshest conditions. And they went big, 70 – 120 meters in diameter, rivalling Rome\u2019s Colosseum, depending on the cage design. Offering a home for 3,000 and 6,000 tons of salmon, that is more than 0.5 to 1 million individuals, respectively, all while withstanding individual waves of up to 27 meters high.<\/p>\n<\/div><\/div>\n\n\n\n

Design to accommodate for biology \u2013 leveraging a digital twin<\/h2>\n\n\n\n

But obviously a large basin and structural integrity is not enough when \u2019Fish first\u2019 is your mantra. The team around Kristoffer also wanted to ensure a design that accommodated biology. Throughout each design phase the team\u2019s focus was targeted on a design that was good for the fish.<\/p>\n\n\n\n

Kristoffer Jakobsen states: \u201cTraditionally, in the design phase, there is little criteria you can use to manage fish health and welfare. This implies that biologists and vets typically evaluate fish performance after a system has been built and, any changes at this late stage can be very expensive, if not impossible. You basically design a structure to withstand the waves, and then you hope the fish will like it.\u201d<\/p>\n\n\n\n

So how do you judge fish welfare when the structure you are about to design and build is so huge and expensive that you can\u2019t afford to just \u2018build and see\u2019.<\/p>\n\n\n\n

The first imminent answer for Aker Solutions was to tackle the challenge like it would tackle many other engineering challenges, by leveraging a digital twin. \u201cWe have worked on aquaculture projects before. While simulation technology has always been an intrinsic part of our offshore projects, to assess fish welfare based on simulation was not on our radar in these early days. And yet, these first projects indicated how important simulation really is.\u201d says Kristoffer.<\/p>\n\n\n\n

\"Simulation<\/figure>\n\n\n\n

Computational Fluid Dynamics of an offshore fish farm<\/h2>\n\n\n\n

Realizing the potential, Aker Solutions started to run computational fluid dynamics simulations to judge the flow conditions and make first assessments of how an offshore fish farm would perform in terms of water exchange. The methodology was initially based on air and water dynamics only. Yet it was quickly expanded to model the net-flow interactions. This already allowed the engineers at Aker Solutions to judge the effect of various net types including their interaction with the fish farm structure which jointly affected the flow conditions inside the cage and hence the water conditions for the fish.<\/p>\n\n\n\n

\u201cReliably modeling the effect of net structures is not new to this industry and modeling a net alone can be done by many. But modeling the net interacting with a structure can only be done with a sophisticated CFD methodology. That has been done by few so far.\u201d says Joakim H\u00e4gglund, specialist CFD engineer at Aker Solutions. The challenge becomes even clearer if you remember that these nets, given the size of the offshore fishfarm, are huge. With a diameter of a farm about 100 m, a typical net circumference measures more than 300 m, so we are talking football fields of nets, millions of netting nodes etc. \u201cThe capabilities of Simcenter\u2122 STAR-CCM+\u2122 software really enabled us to resolve the impact of various net designs and their interaction with the structure to draw some valuable engineering conclusions.\u201d says Joakim.<\/p>\n\n\n\n

But the insights from that initial study also raised a huge question. \u201cCan we draw any meaningful conclusions on fish welfare from the flow field inside the cage, when we ignore the fish itself? And what does that even mean in engineering terms, fish welfare?\u201d says Kristoffer.<\/p>\n\n\n\n

\"Simulation<\/figure>\n\n\n\n

Fish welfare \u2013 in CFD engineering terms<\/h2>\n\n\n\n

It was clear to the team at Aker Solutions that now was the time to take \u2018fish first\u2019 seriously and come up with a simulation methodology that was capable of judging if fish welfare is better or worse as a function of the aquaculture design under various flow conditions. \u201cWe were quite realistic in terms of what we could achieve,\u201d says Joakim. \u201cIf your goal is to simulate the well-being of a fish swarm of a million individuals in the rough and highly transient conditions of the high seas, you need to set the right expectations. If we can judge whether design A is superior to design B with a high-level certainty, given the complex nature of the challenge at hand, that is a huge achievement and beyond anything this industry has seen so far.\u201d<\/p>\n\n\n\n

The team around Joakim was ready to do what it took to achieve that ambitious goal. In the next phase of the project, they looked at ways to quantify how fish welfare translated into accessible CFD simulation data. Many factors to foster healthy conditions in aquaculture are well understood in research. Above all is a sufficient exchange of wastewater with fresh water, connected to a certain level of flow velocity across the cage as well as the maintenance of optimum oxygen levels across the whole farm. While correlating such engineering numbers with a quantifiable real-life absolute \u2019fish welfare index\u2019 is hard, such indicators are a solid basis to compare two fish farm designs. \u201cBeing able to predict those factors will already allow to us to draw meaningful conclusions,\u201d says Joakim.<\/p>\n\n\n\n

Thanks to Simcenter STAR-CCM+, judging local velocity field conditions across a given fish farm design was straight forward. With the embedded design exploration tool, the Aker Solutions team could easily make simulation sweeps across various weather, i.e. wind, water stream and temperature conditions and correlate these with sensors delivering data from potential fish farm locations.<\/p>\n\n\n\n

The impact of a million fish<\/h2>\n\n\n\n

But coming back to \u2019fish first\u2019 the big question was still: Is it good enough to neglect the presence of 6,000 tons of fish when the aim of the study was to understand exactly how those fish are doing under certain conditions? In engineering terms, does the fish swarm affect the flow field? And if yes, to what extent? Is it sufficient to neglect the fish impact on the flow entirely or are the simulation errors associated with such a crude approximation of a reality so big, that the entire methodology is meaningless? It was the usual simulation engineer\u2019s set of questions that bubbled up. \u201cIf you don\u2019t have any measurements available, which we did not at that stage,\u201d says CFD engineer Philip M\u00e5nsson. \u201cThere is only one way to find out, model the fish.\u201d<\/p>\n\n\n\n

Up until this point this would be quite the usual CFD simulation story, but with the decision to simulate a swarm of fish coupled to highly transient flows, Aker Solutions took the risk of opening a can of worms, in the hope for a good catch. Consequently, the team entered and explored entirely new territories of CFD.<\/p>\n\n\n\n

Discrete Element Modeling of a fish swarm<\/h2>\n\n\n\n

3,000-6,000 tons of fish translates to around 1 million individuals. So, you soon realize that you cannot model each fish.<\/p>\n\n\n\n

\u201cThis was the moment when Simcenter STAR-CCM+ really came in handy,\u201d says Joakim. \u201cWe were quite certain modeling the swarm of fish must be tightly coupled to the flow field to add further value to our predictions, and we needed a tool that would seamlessly and computationally cater for such two-way coupled simulations with ease.\u201d<\/p>\n\n\n\n

Therefore, the fully integrated Discrete Element Method DEM seemed the way to go. By representing a local sub-swarm of 130 fish individuals with a representative particle, the simulation engineers reduced the total number of necessary \u2019fish-representative particles\u2018 to capture the whole swarm to a computationally reasonable number of around 10-20 thousand. This, in principle, enabled the simulation of the complete swarm moving inside the entire fish farm, some of which measure over 100 meters in diameter.<\/p>\n\n\n\n

But that immediately brought several new challenges to the simulation engineers at Aker Solutions.<\/p>\n\n\n\n

Firstly, if you want to simulate the overall swarm dynamics from the behavior of its individuals, or a representative cluster of such individuals, you must define the interaction forces between these representative sub-swarms in a meaningful way. Secondly, if you want to study the two-way coupled impact of a sub-swarm particle on the local flow field and vice versa, you must come up with meaningful drag and thrust force correlations for such an artificial cluster of fish.<\/p>\n\n\n\n

The simulation team at Aker Solutions did not shy away from those challenges and instead, shifted gears, further pushing their innovative simulation method. \u201cLeveraging Simcenter STAR-CCM+\u2019s flexibility, we were able to implement customized physically motivated interaction force fields to precisely model the interaction between the fish sub-swarms,\u201d explains Joakim. Whilst the CFD team is not disclosing all details, the model caters for an attraction force between sub swarms if they get close enough that turns into a retraction force if two sub-swarms overlap or collide.<\/p>\n\n\n\n

\"Swarm<\/figure>\n\n\n\n
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Simulating swarm dynamics<\/h2>\n\n\n\n

\u201cIf you know a little bit about swarm dynamics, or ever watched a swarm of birds or fish for a few minutes, you will realize how those interaction functions between individuals or subsets of the swarm can trigger highly non-linear effects that lead to impressive, often beautiful pattern formations at times,\u201d says Joakim. \u201cIt was an amazing moment to see our digital salmon swarm execute such exciting choreographies as if guided by some invisible hand, when we did our first digital experiments.\u201d<\/p>\n\n\n\n

At that stage, the simulation engineers leveraged Simcenter STAR-CCM+\u2018s meshfree DEM that enabled them to run rapid swarm-only simulations to study the impact of and fine-tune their sub-swarm interaction model.<\/p>\n\n\n\n

Yet the interaction between the local water conditions and a fish sub-swarm particle was still to be answered. Two forces act on a representative fish sub-swarm while it moves through the water. A thrust force drives the cluster of fish forward, representing the self-propelling motion of those fish in that cluster. Fish sub-swarms accelerate based on this thrust force until they either reach a certain goal velocity or (coming back to the intra-particle interaction forces) collide with another sub-swarm and decelerates.<\/p>\n\n\n\n

<\/p>\n<\/div>\n\n\n\n

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At the same time the undisturbed sub-swarm experiences a decelerating drag force based on the effective slip velocity. These forces determine the two-way coupling between particles and fluid as the fish sub-swarms move through the water.<\/p>\n\n\n\n

Fish first CFD principles<\/p>\n\n\n\n

But it would not have been this ambitious simulation engineering team, had they not further stepped up their CFD-game to gather precise drag coefficients and thrust functions for the individual fish. And so, the team around Joakim created another highly sophisticated simulation model of an individual moving fish. \u201cIt felt like we were really pushing the edge of what Simcenter STAR-CCM+ had to offer. Morphing mesh, overset mesh, 6 degree-of-freedom fluid structure interaction. That fish will be moving as realistically as possible,\u201d says Philip.<\/p>\n\n\n\n

\u201cWe could not have taken our initial project mantra \u2018fish first\u2019 any more literally,\u201d adds Joakim. \u201cWhen we started this, I never thought we would end up simulating a moving fish with CFD.\u201d<\/p>\n<\/div>\n<\/div>\n\n\n\n