I created a new simulation project called 'Free Floating Boat in a Wave Tank':
This project simulates the free movement of floating boat under a wave using 6 DOF motion.
More of my public projects can be found here.
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Description
The project simulates the free movement of a floating boat under the influence of a headon wave via a Multi-phase 6-DOF (degree of freedom) transient analysis. The boat is considered as a stationary floating body in a water tank with an open top. A single wave is generated to create disturbance in the water and simulate the motion of the boat. For simplicity of the analysis a laminar model was used.
Project Goals
The main purpose of this project is to demonstrate how free floating body motion can be predicted via simulation to provide insight and aid in marine vehicle design and development.
Geometries
The geometry consists of a boat body enclosed in a tank. The geometry is shown in Figure 1 with the boat highlighted in red. (Note: This is an inverted model, thus the fluid area around the boat is a solid volume while the boat is empty space.)
Figure 1: Floating Boat - Geometry
Meshes
To reduce the size of computational domain, only half of the original domain was meshed using the hex-dominant parametric meshing algorithm on the SimScale platform. The resulting mesh (flow domain only) consists of approximately 0.5 million cells and is shown in Figure 2 below.
Figure 2: Floating Boat - Mesh
Simulations
The flow domain consists of two fluid phases, water and air, thus a Mutiphase Analysis must be done.
The initial distribution of the water phase is set under Initial Conditions by using a geometry primitive named ‘water-initial-state’.
Figure 3: Floating Boat - Mesh
The wave is then generated using another geometry primitive named ‘Wave’.
Figure 4: Floating Boat - Mesh
The domain boundaries are considered as Walls with the top surface as an Open Inlet-Outlet boundary. A Symmetry condition is applied to the side surface based of geometry and flow requirements.
The 6 DOF (degree of freedom) model can be added under the Advanced Concepts item in the SimScale Project Tree, Solid Body Motions. Moreover, in accordance with the symmetry condition, constraints were applied for the rotations and lateral motion was allowed only in the vertical direction. The boat was taken as a solid body with a mass of 740 kg and appropriate values for the moment of inertia.
The simulation was run for 4 seconds of simulation time with automatic time stepping and a maximum courant number (CFL) of 0.5 ( It is recommended that the CFL should be < 0.5 and preferably around 0.3). The job was run on 8 compute cores and took about 5 hours to complete.
Results and Conclusions
The results below (processed using the local version of ParaView, an open source visualization toolkit) show the transient changes in phase fraction of water (Figure 5) and flow velocities along with the free motion of the boat due to the fluid forces. This simulation shows how the free floating body motion can be predicted via simulation to provide insight and aid in Marine vehicle design and development.
Figure 5: Phase Fraction animation
Figure 6: Velocity (m/s) animation
References
This is great! What is the current standing of SimScale on 2-way FSI? It appears to me that 2-way FSI is currently not capable on the platform. Are there any plans to add it?
Hello,
Indeed, right now the 2-way fluid-solid-interactions (FSI) are not fully integrated. There are upcoming developments that will enable these features, yet due to high complexity of these models it might take some time.
Best,
Pawel
@psosnowski2 can you please elaborate the method and filters you used for processing the results to get such type of animation in paraview. THANKS IN ADV.
Regards
Sachin
It would be really interesting to have an animation of the pressure evolving on the Hull.
this tutorial is available on the platform but isn’t detailed enough. Especially the 6 DOF section in advanced concepts. My simulation fails everytime.
There are two faces in the front. Why? How to generate a wave?
Hey there @prghumar!
This doc entry might help you out \rightarrow https://www.simscale.com/docs/simulation-setup/advanced-concepts/six-degree-of-freedom-motion/ . Let me know if that helped!
Jousef
This is the link to my project. I have 2 doubts:
In feature refinement I am not able to apply it only to the boat. The end result shows edge refinement over the edges of the tank which is unnecessary. How to get rid of it?
I want to calculate the force and moment over the boat faces. Should I consider the whole boat or half for reference area approximation?
Sincerely,