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Onsala Ingenjörsbyrå AB

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+46 705 64 64 00

Onsala Ingenjörsbyrå AB

Your partner in advanced structural and fluid calculations

With a history of over two decades in the Swedish nuclear industry, we have a long record of projects carried out for the nuclear power plants Ringhals, Oskarshamn och Forsmark.

With high-end resources in both software and hardware, combined with experience and continuously educated personel, we are able to perform highly advanced projects in-house, in our office in Kungsbacka, Sweden.

We work with:

fracture mechanics, vibrations caused by flow fields

fluid-structure-interaction (FSI)



water-hammer analysis

large and small effects of LOCA (Loss of cooling accidents)

we have long experience in structural verification projects of RPVs and internals of BWRs including fatigue analysis

Project management

Our field of expertise

What we offer


We use Creo, Pro/E and NX for CAD


We model everything from complex high detailed models for customers wanting to bring their drawings in to the 21th century like a complete CAD assembly model of a nuclear reactor, down to the smallest nut and bolt, all the way to smaller models of interest like a piping system with supports.

The in-house knowledge and CAD modeling expertise is the back-bone to all our further engineering work today. As all the models are compatible with our calculation software, this leads to a boost in geometric quality and endless levels of detail for the calculation models that we produce.


Powerful computers helps us to conduct structural problems on a large scale with high complexity.


We analyze structural responses caused by vibrations, thermal transients and analyze thermo-mechanical fatigue, cracks, structural collapse, impact, etc. Mainly we analyze components in the nuclear industry such as. reactor vessels, cooling systems, internal parts, piping systems, turbines and buildings. Each component individually or many components in the same model, as is the case in larger structural verification projects.


We perform CFD calculations in FLUENT and iSTAR-CCM+ on powerful HP Linux clusters.


We have over 20 years of experience in CFD. For model preparation we use Pro/E, ANSA and ADINA/AUI. To name some examples of typical work, we analyze the structural response to transient and vibrational loadings, thermal transients and thermo-mechanical fatigue, cracks and fracture, collisions and collapse. Typical cases range in size from a few million cells to over 100 million cells in some complex models and/or R&D projects.

Thanks to the capacity of our clusters, we can offer companies the opportunity to buy CPU hours from us to run their own cases on our system.


We use ADINA-FSI and ADINA coupled with thermo-hydraulic results from e.g. RELAP5, FLUENT and STAR-CCM+ to solve coupled FSI problems.


For LOCA and acoustic analysis we use slightly different strategies. For the water modeling, e.g. linear potential-based elements or subsonic potential-based elements. For the connection between fluid and structure, e.g. 2-way ADINA-FSI or 1+2-way ADINA-FSI, depending on the phenomena and loads involved.

The method of linking RELAP5 with Adina has proven to be a very powerful method in various evaluation tests against real cases and experiments.

Read about our latest mention in ADINA News!

New from 2013 is that we have also brought in ANSYS Mechanical which we connect with ANSYS Fluent for full 2-way FSI coupling. The vision is to be able to calculate strongly coupled systems where the non-linear flow effects are dominant and difficult to correct for.

Feel free to contact us for questions or a quote.


Latest projects

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