Many tools exist to simulate dynamic systems in the time domain, with different focus and usage areas. The key goals when developing FhSim has been simulation performance, models development and re-usability. The resulting characteristics is the use of C++ for model development, integrated 3D visualisation (which can be disabled) and the need for C++ skills to develop new models.


FhSim is a software platform and framework for mathematical modelling and numerical simulation, with a focus on marine applications.

Fast Development

FhSim provides a common simulation environment in which models can be shared and combined in many different ways. This facilitates re-use, preserves project results, and cuts down on model development costs.

Extensive Model Library

FhSim features a large collection of mathematical models, including ships, trawl nets and doors, net cages, ropes and weight systems, buoys, cables, winches, and anchors.


FhSim can be run on Windows and Linux, as a stand-alone or as an API. It can be coupled with MATLAB/Simulink, and executed via Java (JNI).

High Realism

Models in FhSim are continuously validated against experimental data through projects employing FhSim as a tool. This ensures realistic model responses.

Speed and performance

FhSim is developed with performance and real-time applications in mind. FhSim is used for applications where performance is paramount, such as monitoring (state estimation), control systems (MPC), operational decision support and personnel training in virtual environments.

3D Visualization

FhSim features 3D visualization for development, demos, and presentation of results. Alternatively, it can also be run without visualization for maximum efficiency, e.g. when connected to external visualization engines.

Previous use cases

FhSim is in use in research, education, industry, and in training simulators. Here is a selection of past projects based on FhSim.
Sea cage
Full-scale sea cage in rough seas
Bottom trawling
Simulation of a bottom trawl system
Boat and net cage
Typical aquaculture operation with a boat and a net cage
Pitch damping with foils
Exploring optimal foil design and position to dampen vessel pitch movements
Fish farm
Simulation of a fish farm with multiple net cages
Trawl colliding with offshore pipeline
Evaluating the risk of trawl door snagging on offshore pipeline
State estimation
Improve inaccurate measurements using state estimation
Trawl impact on mooring
Analysis of trawl impact on mooring lines.
Structures in ice floe
Simulation of interactions between structures and ice floe
Vessel in ice (cosimulation)
Simulation of a vessel hull in ice, using cosimulation.
Digital twin of fish farm
Simulating a fish farm in real time, syncronised with the real farm using measurements.


FhSim consists of several components which support different ways of use. Currently, the license terms are different for different parts of FhSim. Some are available for academic use, some for everyone and some only for paying customers. It is in the process of being made available for the public.


The FhSim executables can run simulations with and without visualisation and with or without real-time requirements. FhSim also includes functionality for running parameter variations, well suited for sensitivity studies and batch simulations.

Expected available: May 2022

Model libraries

The FhSim models are collected in precompiled libraries according to domain and license. Some models will be publicly available, while other will be available only to paying customers.

Expected available: August 2022

Light API

The FhSim Light API can be used for running FhSim simulations from your own software. Its main part is a shared library, through which a simulation can be run. Your own software can then set input ports, read output ports and states and step the simulation forward.

Expected available: December 2022


The FhSim API can be used for creating new simulation models and seamlessly integrate FhSim with your own software.

Expected available: December 2022

Source code

The source code for the FhSim API will be made available both as an assurance for the Ratatosk users, simplify development and to facilitate extending it as desired.

Expected available: To be determined

Support & Team

Meet the team behind FhSim in SINTEF Ocean.

Stian Skjong

Energy systems, co-simulation, state estimation and control

Biao Su

Marine aquaculture systems, ice-structure interactions

Karl-Johan Reite

FhSim core, net structures, trawl

Joakim Haugen

FhSim core, net structures, trawl

Andrei Tsarau

Hydrodynamics, sea loads, closed containment systems and net cages

Herman Biørn Amundsen

FhSim build system, FhSim core, net cages

Do you have any questions? Do you need support? Are you wondering how FhSim can be used in your project to help you reach your goals? Don't hesitate to contact us today!