Numerical time domain simulations have proven applicable for analysing marine systems and operations, but available tools often target specific sub-problems or applications associated with a system or an operation. Such tools are also often limited in terms of extensions and usage. This has motivated the development of FhSim at SINTEF Fisheries and Aquaculture (SFA). FhSim is a software framework aimed at simulating especially marine systems in the time domain, using models described as ordinary differential equations (ODEs). In this paper, we present the architecture and core functionality of the FhSim framework, including modelling, integration and 3D-visualisation. We also present a series of simulation cases which illustrate the different core properties of FhSim, including numerical simulations of aquaculture structures, model-based estimation of trawl nets and optimisation of energy systems in ships.
In this work, we present a generic framework for designing on-board decision support systems for marine operations. We discuss different technologies and methods for obtaining and analysing data and providing relevant information to on-board personnel. In particular, we focus on combining and integrating simulators with measurements, both live and stored historical data, in on-board systems for both pre-operational planning and live situation observers that might have predictive functionalities. To exemplify, we present four case studies: The first two are concerned with development of an on-board decision support system for offshore crane operations. Here, vessel motion measurements and numerical models are combined for both on-board surveillance applications and on-board pre-operational planning applications, where the latter include historical vessel characteristics. In the third, we combine simulations, measurements and automatic control in an application aimed at triple-trawl fishing operations. Finally, we present a data-driven decision support system for energy-efficient operation of hybrid propulsion systems.
The performance of three different numerical methods were compared and evaluated against data from physical model tests of nets subjected to a static load due to water currents. A parameter study of a simplified net cage model subjected to a steady flow was performed by all methods, varying the net solidity and the flow velocity. The three numerical methods applied models based on springs, trusses, or triangular finite elements. Hydrodynamic load calculations were based on the drag term in Morison's equation and the cross-flow principle. Different approaches to account for wake effects were applied. In general, the presented numerical methods should be able to calculate loads and deformations within acceptable tolerance limits for low to intermediate current flow velocities and net solidities, while numerical analyses of high solidity nets subjected to high current velocities tend to overpredict the drag loads acting on the structure. To accurately estimate hydrodynamic loads and structural response of net structures with high projected solidity, new knowledge and methods are needed.
Research within marine aquaculture has either focused on technology (e.g. farming structures, autonomous systems, harvesting and transport technologies) or biology (e.g. biomass control, feeding process, fish behavior and welfare). Here, we present a computational framework allowing the integrated analysis of these two aspects in a flexible and evolutive way. This framework is called FhSim which was originally developed for the modelling and simulation of fisheries operations and aquaculture structures, but its application domain has been continuously extended through different research projects. In this paper, we present the basic design principles and functionality of the FhSim framework with the focus on modelling and simulation of marine aquaculture systems. The basic theories and methods used for the modelling of open net cages, closed cages, fish behavior, feeding processes, and ROV operations in net cages are introduced, respectively. It is also shown how the technological and biological aspects of fish farming can be considered in a specialized or integrated analysis. Furthermore, approaches for combining numerical models with monitoring sensor data, techniques for real-time simulation of fish farming operations and the coupling of FhSim with other simulation programs are discussed.
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