Difference between Yaw Bearing and Tower Top loads
Category: Structural dynamics
Problem
Why are Yaw Bearing and Tower Top loads sometimes different even when the yaw angle is zero?
Solution
In Bladed 4.4 and earlier, there is a slight different in coordinate system between the tower loads and the yaw bearing loads even when the yaw angle is zero.
In the diagram below, the dotted line shows the deflected tower position. In Bladed 4.4 and earlier, the coordinate system for tower load output doesn’t rotate with deflections. From Bladed 4.5, the tower load output coordinate system does rotate with tower deflection, so there should be an exact match between tower and yaw bearing loads when yaw angle = 0.
In both 4.4 and 4.5, the coordinate system for yaw bearing loads does rotate with nacelle rotation, so only in Bladed 4.5 and later will you see an exact match in loads.
Keywords Tower Tower, Yaw Bearing