# Equations for the tail orientation

Hello all,

I am modelling a small wind turbine which is passive oriented with a tail, but not a furling a system. I have deactivated the tail-furl DOF and I am trying to understand the influence of different variables (e.g. tail mass, tail area, position of the pressure center and so on) on the orientation mechanism. I would like to know which are the equations that govern the orientation to correctly understand the implication of each part of the tail.

Thanks,

Ohiana Goikoetxe

Dear Ohiana,

I’m not sure I understand your question. The tail-furl DOF is one of the many DOFs that is included in FAST’s equations of motion for the full wind turbine system.

The “Tail-Furl” section of the “Model Description” chapter of the FAST User’s Guide explains how the tail-furl model works.

Best regards,

Dear Jason,

I think I was not very clear in my explanation. I am modelling an upwind oriented wind turbine with a tail, but it doesn’t have a furling system, so the DOF of the furling is set to False. My intention is to use FAST to study the influence of the different parameters that define the tail -such as tail area, boom mass, tail mass, inertia and so on- on the yaw speed and yaw error for the configuration mentioned. So, my question was which is the equation that governs the movement aroung the yaw axis in this situation.

Thanks again. Best regards,

Ohiana

Dear Ohiana,

I guess I’m still not sure I understand your question. Even without furling DOFs, there are many things that effect the yaw motion of a wind turbine, including:
*tail size/configuration
*lateral offset and tilt of the shaft from the yaw axis
*rotor dynamics, including assymetric aerodynamic loads and mass imbalances
*gyroscopics from rotor rotation in conjunction with tower dynamics

All of these effects contribute to terms in the overall system-dynamics equations of motion; with the nacelle-yaw DOF coupled to many other system DOFs. Without simplifying many aspects of the model, one can’t identify a simple yaw equation. Instead, one would have to look at the entire set of system equations of motion.

I hope that helps.

Best regards,