I have a question regarding the adjustment of the Hydrodyn linear and quadratic damping matrices. I use a Potential Flow model, combined with linear and quadratic damping matrices to account for viscous effects.
I would like to adjust the matrices based on CFD simulations (looking for the Free Decay in OpenFAST to be as close as possible to the Free Decay in CFD). And I want to adjust the matrix for a platform where the CoG does not coincide with the point (0, 0, 0), as shown in the attached image.
I thought that, in this case, the cross damping terms (non-diagonal terms of the matrix) in Pitch-Heave DOFs might be relevant (coefficientes C35 and C53 of the matrices). And I would like to know your opinion on this: whether the non-diagonal terms are important in this case, or whether they can be neglected. If these coefficients are important, I will run CFD with the 2 DOFs (Pitch and Heave) activated. If not, I will adjust damping coefficients of each DOF separately.
Thank you in advance.