.. _knowledge_base_slidingInterfaces:

:ref:`slidingInterfaces <slidingInterfacesParameters>`
=======================================================

:code:`axisOfRotation`
-----------------------
The rotation of a sliding interface follows the right hand rule. The fingers follow the spinning of the sliding interface and the thumb points to the :code:`axisOfRotation`. Left handed rotations can be simulated by entering a negative :code:`omega`.

.. grid:: 2

    .. grid-item::
        :columns: 6
        :margin: auto

        .. figure:: ../BETDisks/Figures/left_hand_rule.svg
            :width: 80%
            :align: center

    .. grid-item::
        :columns: 6
        :margin: auto

        .. figure:: ../BETDisks/Figures/right_hand_rule.svg
            :width: 80%
            :align: center

:code:`omega`
--------------
For convenience, there are two options for prescribing the nondimensional rotation speed in the Flow360.json file.
Users can either input :code:`omegaRadians` or :code:`omegaDegrees` according to the units of their physical rotation speed :math:`\Omega`\:

.. math::

    \text{omegaRadians} = \Omega \ \text{(rad/s)} \cdot \frac{L_\text{gridUnit}}{C_\infty}
    
    \text{omegaDegrees} = \Omega \ \text{(deg/s)} \cdot \frac{L_\text{gridUnit}}{C_\infty}

See this :ref:`example <non_dim_omega>` showing how to obtain nondimensional :code:`omega` from RPM and this :ref:`tutorial <sliding_interface>` for an unsteady isolated rotor case using a sliding interface.

..
    [TODO]
    Once Qiqi and I figure out the best-practice for the dynamic derivatives, I will add more info on setting up thetaRadians and thetaDegrees