I need proper references with the differential equations solved in FAST v7 along with the details of the integration scheme used.
Additionally, it would help if I could get some information on how and which damping modes are taken in the time domain analysis while the turbine is operational.
The structural equations of motion of FAST v7 are the same as those of the ElastoDyn module of OpenFAST, documented here: 4.2.7. ElastoDyn Users Guide and Theory Manual — OpenFAST v3.2.0 documentation. In FAST v7, the states are updated from one time step to the next based on a fourth-order Adams-Bashforth-Adams-Moulton (ABM4) predictor-corrector integration scheme. This integrator is initialized using a fourth-order Runge-Kutta (RK4) integration scheme.
For an aeroelastic simulation, damping results from structural damping and aerodynamic/aeroelastic damping. Technically, any velocity-dependent force acts like a damping, so, you could also say forces such as gyroscopic, Coriolis, and generator torque-speed curves are also “damping like” terms.
I appreciate your input. I would further like to take a step ahead and quantify the aerodynamic damping of an operating wind turbine during a seismic event. How can I use FAST Seismic Module in doing so?
Perhaps you could compute the structural response with and without the aerodynamic loads applied and calculate the effect of aerodynamic damping by comparing these responses?