B modeling
==============




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

The rotor is modelled by quadratic volume elements ('3D' modeling, MECA_HEXA20).

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 HEXA20 ", "112"


**Table** 4.2-1




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'", "2562.08"," 3.00%"
    "Mode 2", "'EXTERNE'", "2562.08"," 3.00%"
    "Mode 3", "'EXTERNE'", "2962.72"," 2.00%"
    "Mode 4", "'EXTERNE'", "2962.72"," 2.00%"
    "Mode 5", "'EXTERNE'", "6231.34"," 1.00%"
    "Mode 6", "'EXTERNE'", "6231.34"," 1.00%"
    "Mode 7", "'EXTERNE'", "6313.73"," 1.00%"
    "Mode 8", "'EXTERNE'", "6420.42"," 1.00%"
    "Mode 9", "'EXTERNE'", "6420.42"," 1.00%"
    "Mode 10", "'EXTERNE'", "6658.75"," 3.00%"
    "Mode 11", "'EXTERNE'", "6658.75"," 3.00%"
    "Mode 12", "'EXTERNE'", "7040.85"," 1.00%"
    "Mode 13", "'EXTERNE'", "7040.85"," 1.00%"
    "Mode 14", "'EXTERNE'", "7159.02"," 3.00%"


**Table** 4.3-1 **: Summary of results tested when stopped (elements** HEXA20 **)**

The gap at standstill between the two models seems significant (maximum difference of 3%). The explanation lies in the fact that code ANSYS sub-integrates quadratic volume elements (cf. modeling C) while this modeling uses elements with exact integration.


.. csv-table::

    "**Identification**", "**Reference type**", "**Reference value**", "**Tolerance**"
    "Mode 1", "'EXTERNE'", "53.26"," 2.00%"
    "Mode 2", "'EXTERNE'", "100"," 1.00%"
    "Mode 3", "'EXTERNE'", "2524.2"," 3.00%"
    "Mode 4", "'EXTERNE'", "2601.5"," 3.00%"
    "Fashion 5", "'EXTERNE'", "2928.5"," 2.00%"
    "Mode 6", "'EXTERNE'", "2998.1"," 2.00%"
    "Mode 7", "'EXTERNE'", "6211.4"," 1.00%"
    "Mode 8", "'EXTERNE'", "6251.8"," 1.00%"
    "Mode 9", "'EXTERNE'", "6313"," 1.00%"
    "Mode 10", "'EXTERNE'", "6388.2"," 1.00%"


**Table** 4.3-2 **: Summary of results tested in rotation without centrifugal sweetening**


.. csv-table::

    "**Identification**", "**Reference type**", "**Reference value**", "**Tolerance**"
    "Mode 1", "'EXTERNE'", "26.63"," 2.00%"
    "Mode 2", "'EXTERNE'", "26.63"," 2.00%"
    "Mode 3", "'EXTERNE'", "50"," 1.00%"
    "Mode 4", "'EXTERNE'", "50"," 1.00%"
    "Mode 5", "'EXTERNE'", "2523.74"," 3.00%"
    "Mode 6", "'EXTERNE'", "2600.99"," 3.00%"
    "Fashion 7", "'EXTERNE'", "2928.09"," 2.00%"
    "Mode 8", "'EXTERNE'", "2997.72"," 2.00%"
    "Mode 9", "'EXTERNE'", "6211.33"," 1.00%"
    "Mode 10", "'EXTERNE'", "6251.73"," 1.00%"
    "Mode 11", "'EXTERNE'", "6312.84"," 1.00%"
    "Mode 12", "'EXTERNE'", "6388.03"," 1.00%"


**Table** 4.3-3 **: Summary of results tested in rotation with centrifugal sweetening**