Dear all,
I don’t know I don’t know if this is the right place to ask the question, but I should have a try.
I have read a certain amount of theses about various floating platform, for example OC4 or OO-Star because I am major in NREL5MW and DTU10MW. But almost all are not provide inertia about system CM, which are replaced by inertia about RNA CM and floating platform CM.A paper about OC5 provide it but it is not adapted to NREL5MW or DTU10MW, but a blade from MARIN.
I use STAR-CCM+ for CFD and DFBI. When I setting up the DFBI, I should type in moment of inertia of the 6-DOFs body. But unlucky I hardly to find it if it is the inertia about system CM mentioned in many theses.
I wang to know where I could find the full system inertia for my DFBI setting, or if the inertia about floating platform CM can be used as that about full system.
Dear @Wenchao.Shen,
The 6x6 mass matrix for the full system (rotor + drivetrain + nacelle + tower + floater + ballast) of the NREL 5-MW baseline wind turbine atop the OC4-DeepCwind semisubmersible is available in my post dated Feb 13, 2020 in the following forum topic: OC4-DeepCwind semisubmersible - WAMIT Files.
Best regards,
[quote=“Wenchao.Shen, post:3, topic:8158, full:true”]
Dear Jonkman,
Thanks for your reply and I find the matrix I need, it is really help me a lot.
But the center of mass quadrant,
0.000E+00 -1.392E+08 0.000E+00
1.392E+08 0.000E+00 -1.448E+05
0.000E+00 1.448E+05 0.000E+00
In my understanding, the center of mass is a point at Z axis, but I can’t understand what’s the 3×3 matrix mean.
I find the center of mass about platform is a mumber that “CM location below SWL”, for example it is 13.46m in OC4. But what I need is about the whole system.
Could you please tell me how could I read this matrix or where can I find the value of the CM location about the system?
Best regards
Dear @Wenchao.Shen,
The 6x6 mass matrix of a rigid body includes the mass (upper-left quadrant), inertias (lower-right quadrant), and center of mass (upper-right and lower-left quadrants) of the rigid body about the reference point used to derive the mass matrix, per the following equation:
E.g., in your case, z_g = M(1,5)/M(1,1) = ( -1.392E+8 kg*m )/( 1.407E+7 kg ) = -9.893 m.
Best regards,
Thank you so much! That really help me a lot!!