Quickstart
=====
See :doc:`installation`, if you have not yet installed *openTorsion*. OpenTorsion can be used by creating a shaft-line finite element model.

Example: Calculating the eigenfrequencies, mode shapes and a Campbell diagram with a shaft-line finite element model of a windmill [#Sop2011]_.

.. code:: bash

    import opentorsion as ot
    
    k1 = 3.67e8  # Turbine shaft stiffness
    k2 = 5.496e9  # Rotor stiffness
    J1 = 1e7  # Turbine inertia
    J2 = 5770  # Rotor inner inertia
    J3 = 97030  # Rotor outer inertia

    # Elements are initiated and added to corresponding list
    shafts, disks = [], []
    disks.append(ot.Disk(0, J1))
    shafts.append(ot.Shaft(0, 1, None, None, k=k1, I=0))
    disks.append(ot.Disk(1, J2))
    shafts.append(ot.Shaft(1, 2, None, None, k=k2, I=0))
    disks.append(ot.Disk(2, J3))

    # An assembly is initiated with the lists of powertrain elements
    assembly = ot.Assembly(shafts, disk_elements=disks)
    
    # Calculation of the eigenfrequencies of the powertrain
    omegas_undamped, omegas_damped, damping_ratios = assembly.modal_analysis()

    # Print eigenfrequencies.
    # The list contains each eigenfrequency twice: e.g. eigenfrequencies = [1st, 1st, 2nd, 2nd, 3rd, 3rd, ...]
    print("Eigenfrequencies: ", omegas_undamped.round(3))

    # Initiate plotting tools calling Plots(assembly)
    plot_tools = ot.Plots(assembly)

    # Plot eigenmodes, input number of eigenmodes
    plot_tools.plot_assembly()
    plot_tools.plot_eigenmodes(modes=3)
    plot_tools.plot_campbell(frequency_range_rpm=[0, 300], num_modes=2)

See more :doc:`opentorsion.examples` and :doc:`tutorials`.

.. rubric:: References

.. [#Sop2011] J. Sopanen, V. Ruuskanen, J. Nerg and J. Pyrhonen, "Dynamic Torque Analysis of a Wind Turbine Drive Train Including a Direct-Driven Permanent-Magnet Generator," in IEEE Transactions on Industrial Electronics, vol. 58, no. 9, pp. 3859-3867, Sept. 2011, doi: 10.1109/TIE.2010.2087301.