Dynamics of Flexible Rotor Systems with an Interim Mass Unbalanced Disk Using a Spectral Element Model

Table 2

Natural frequencies (Hz) of the rotor system (𝑚_𝑈 = 0.493 kg, Ω = 100 Hz).

Modes	SEM(3)	FEM(𝑛)
		𝑛=3	𝑛=11	𝑛=21	𝑛=41	𝑛=51	𝑛=61
1st
Backward	153.879	153.888	153.880	153.879	153.879	153.879	153.879
Forward	155.229	155.238	155.230	155.230	155.229	155.229	155.229
2nd
Backward	858.096	862.037	858.467	858.177	858.113	858.105	858.096
Forward	890.763	895.183	891.186	890.856	890.783	890.774	890.763
3rd
Backward	1750.56	1779.63	1753.59	1751.22	1750.70	1750.64	1750.56
Forward	1769.11	1798.58	1772.22	1769.80	1769.26	1769.19	1769.11
4th
Backward	2906.57	3040.74	2917.39	2908.95	2907.08	2906.85	2906.57
Forward	2995.77	3143.81	3007.69	2998.40	2996.33	2996.08	2995.77

Note: (𝑛): the total number of finite elements used in the analysis.