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How to build a linear buoyancy model
Dear David,
I have a question for you. In the QBlade Docs, I noticed that when you were validating the six DOF motion of the platform under regular wave conditions, you used a linear buoyancy model that closely matched the results from OpenFAST. Could you please explain how to set up and use the linear buoyancy model in QBlade?
Thank you.
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Hi Camelia,
a linear buoyancy model can be included via the linear hydrodynamic stiffness matrix (SUB_HYDROSTIFFNESS), see this section of the documentation. This matrix can also be utilized to represent a simple linear model of the mooring lines.
Typically, the elements of this matrix are obtained from linear potential flow solvers, such as Wamit or Nemoh, but they can also be derived analytically. When employing a linear stiffness matrix to model buoyancy, it is necessary to include a constant force representing the total buoyancy force when the floater is in its equilibrium position. This force can either be included by the keyword SUB_CONSTFORCE, or through the keyword SUB_DISPLACEDVOLUME.
BR,
David
