Torsional Coupling
A torsional coupling offers a torsional stiffness between the two rotors. Other degrees of freedom — displacement and tilting rotations — of both rotors are rigidly connected. On an interior boundary, the following constraints and torsional moments are applied:
Here, θ1u and θ2u are the bending rotations on one side of the interior boundary and θ1d and θ2d are the rotations on the other side. Subscripts 1 and 2 denote the local y and z direction components of the bending rotation. θ0y and θ0z are the angular misalignment values in the local y and z directions, respectively.
On an exterior boundary, displacements and tilt rotations are free. A torsional moment given by
acts on this boundary.