Modeling A
==============




Characteristics of modeling
-----------------------------------

The rotor is modelled by linear volume elements ('3D' modeling, MECA_HEXA8).

CALC_MODES calculates the modes specific to standstill (ie. without gyroscopic damping) and in rotation, ie. with gyroscopic damping (option MECA_GYRO), but taking into account or not taking into account the softening effect by centrifugal stiffness (option RIGI_ROTA).




Characteristics of the mesh
----------------------------


.. csv-table::

    "Number of stitches HEXA8 ", "896"


**Table** 3.2-1




Results: comparison between Code_Aster and ANSYS calculations
----------------------------------------------------------------

The table gives the numerical values tested in this test case. These are the natural frequencies of the cylinder in a free-free configuration at standstill and at 3000 rpm.


.. csv-table::

    "**Identification**", "**Reference type**", "**Reference value**", "**Tolerance**"
    "Mode 1", "'EXTERNE'", "2627.2"," 6.00%"
    "Mode 2", "'EXTERNE'", "2627.6"," 6.00%"
    "Mode 3", "'EXTERNE'", "3017.1"," 4.00%"
    "Mode 4", "'EXTERNE'", "3017.3"," 4.00%"
    "Mode 5", "'EXTERNE'", "6276.1"," 1.00%"
    "Mode 6", "'EXTERNE'", "6276.1"," 1.00%"
    "Mode 7", "'EXTERNE'", "6327"," 1.00%"
    "Mode 8", "'EXTERNE'", "6487.5"," 2.00%"
    "Mode 9", "'EXTERNE'", "6487.6"," 2.00%"
    "Fashion 10", "'EXTERNE'", "6937.8"," 4.00%"
    "Fashion 11", "'EXTERNE'", "6938.8"," 4.00%"
    "Mode 12", "'EXTERNE'", "7090.9"," 3.00%"
    "Mode 13", "'EXTERNE'", "7091"," 3.00%"
    "Mode 14", "'EXTERNE'", "7410.5"," 4.00%"


**Table** 3.3-1 **: Summary of results tested at standstill**

The gap at standstill between the two models seems significant (up to 6%). The explanation lies in the fact that code ANSYS underintegrates linear solid elements. Since Code_Aster does not allow the sub-integration of elements HEXA8, we used exact integration. It is therefore not possible to verify whether the difference decreases with these elements. On the other hand, Code_Aster allows sub-integration for elements HEXA20 (cf. models B and C).

.. csv-table::

    "**Identification**", "**Reference type**", "**Reference value**", "**Tolerance**"
    "Mode 1", "'EXTERNE'", "53.42"," 1.00%"
    "Mode 2", "'EXTERNE'", "100"," 1.00%"
    "Mode 3", "'EXTERNE'", "2588.8"," 6.00%"
    "Mode 4", "'EXTERNE'", "266.6"," 6.00%"
    "Mode 5", "'EXTERNE'", "2982.4"," 4.00%"
    "Mode 6", "'EXTERNE'", "3052.4"," 4.00%"
    "Mode 7", "'EXTERNE'", "6256.1"," 1.00%"
    "Mode 8", "'EXTERNE'", "6296.5"," 1.00%"
    "Mode 9", "'EXTERNE'", "6326.2"," 1.00%"
    "Mode 10", "'EXTERNE'", "6455.1"," 2.00%"
    "Mode 11", "'EXTERNE'", "6520.1"," 2.00%"


**Table** 3.3-2 **: Summary of results tested in rotation without centrifugal sweetening**


.. csv-table::

    "**Identification**", "**Reference type**", "**Reference value**", "**Tolerance**"
    "Mode 1", "'EXTERNE'", "26.63"," 1.00%"
    "Mode 2", "'EXTERNE'", "26.63"," 1.00%"
    "Mode 3", "'EXTERNE'", "50"," 1.00%"
    "Mode 4", "'EXTERNE'", "50"," 1.00%"
    "Mode 5", "'EXTERNE'", "2588.4"," 6.00%"
    "Mode 6", "'EXTERNE'", "266.1"," 6.00%"
    "Mode 7", "'EXTERNE'", "2982.1"," 4.00%"
    "Mode 8", "'EXTERNE'", "3052"," 4.00%"
    "Mode 9", "'EXTERNE'", "6255.8"," 1.00%"
    "Mode 10", "'EXTERNE'", "6296.2"," 1.00%"
    "Mode 11", "'EXTERNE'", "6326"," 1.00%"
    "Mode 12", "'EXTERNE'", "6455"," 2.00%"
    "Mode 13", "'EXTERNE'", "6519.9"," 2.00%"


**Table** 3.3-3 **: Summary of results tested in rotation with centrifugal sweetening**