Fluid flow
seakeeping simulations of a survey vessel.
Work vessels that operate on sea must be able to function under a wide variety of conditions. Waves impose a limit on the operational capabilities of ships. Together with Demcon Unmanned Systems (DUS), we evaluated V2500 (3M) USV, a small unmanned survey vessel. For seakeeping simulations two approaches are possible to analyze the motion of a vessel in a wave spectrum for various sailing directions. One approach is to make use of a panel method as these are numerically efficient for these types of calculations. The other approach obtains a more accurate result using a CFD simulation, in which effects such as viscosity, damping and turbulence are modelled. Using the results of the simulations and calculations, DUS was able to refine the design of this survey vessel.
Seakeeping simulations
our approach.
For seakeeping simulations two approaches are possible. To analyze the motion of a vessel in a wave spectrum for various sailing directions, it is customary to make use of a panel method as these are numerically efficient for these types of calculations. However, panel methods cannot give insight into flow details around a vessel, as viscosity is neglected and an irrotational velocity field is assumed. A more accurate result is obtained using a CFD simulation, in which effects such as viscosity, damping and turbulence are modelled more accurately. A CFD simulation comes at the cost of increased calculation times, however. To analyze the air entrapment beneath the vessel, a CFD analysis has been performed with the vessel sailing into a regular wave with a height of 1 m. In this type of analysis, a volume of fluids (VOF) approach is used with two separate components: air and seawater. These two components are tracked throughout the simulation with each cell containing a fraction of air and a fraction of seawater.
The vessel is given two degrees of freedom: pitch (rotation around y-axis) and heave (movement along z-axis). Movement of the geometric body within the mesh is accounted for by using an overset mesh approach. For the analysis of the thruster orientation a steady state resistance calculation has been performed. Again, the vessel is allowed movement in pitch and heave. Surface flowlines are used to judge the orientation of the thrusters. For the roll damping a transient calculation has been performed in which the vessel is released from an inclined position. In this case the vessel has two degrees of freedom: roll (rotation around X-axis) and heave.
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Demcon multiphysics.
Demcon multiphysics is an engineering agency with high-end expertise in the area of heat transfer, fluid dynamics, structural mechanics, acoustics, electromagnetism and nuclear physics. We support clients from a wide variety of market sectors and help them achieve their goals in research and development with deep physical insights.
We combine fundamental physical knowledge from an analytical approach with Computer Aided Engineering (CAE) simulations tools from ANSYS, MATHWORKS, COMSOL, STAR-CCM+ and FLUKA to setup, execute, analyze and evaluate numerical simulations. The use of Computational Fluid Dynamics (CFD), Finite Element Analysis (FEM / FEA), Lumped Element Modelling (LEM), Computational Electromagnetics (CEM) and Monte Carlo simulations enables us to make a virtual prototype of your design. With these techniques we can simulate the fluid and gas flows, energy exchange, heat and mass transfer, stresses, strains and vibrations in structures and the interaction of electromagnetic fields with other physical aspects like heat generation. Simulation-driven product development increases the development efficiency and reduces the product development time. Our services can therefore fully support you in the designing phase, from idea up to prototype, from prototype to final design.
