Mechanical Vibration » Rotordynamics Analysis

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Rotordynamics Analysis

INERTANCE has performed the Lateral Vibration Analysis (Rotordynamics Analysis) with necessary design tools for turbo-machinery that includes centrifugal and axial compressors, centrifugal pumps, steam & gas turbines, motors, and gear applications. The rotor components including blades, impellers, etc have been modeled based on manufactured drawings, which can generate a mass-elastic Rotor dynamics Analysis model of rotor assembly. Those analysis includes the critical speed map, unbalance response (imbalance response), stability analysis, etc.

Lateral Vibration (Lateral Analysis)

INERTANCE has a capability to perform below kinds of rotor dynamics analysis.

  • Lateral vibration analysis
  • Rotordynamics analysis
  • Damped eigenvalue (Critical speed) analysis
  • Undamped critical speed map
  • Train lateral vibration analysis
  • Mode shape
  • Campbell diagram analysis
  • Bearing stiffness and damping coefficients
  • Separation margins as per API requirements
  • Forced response analysis (Unbalance response analysis)
  • Imbalance response analysis
  • Bearing clearance assessment
  • Stability analysis
  • Log decrement
  • Oil whirl and whip against rotor instabilities
  • Transient analysis
  • Forward and backward mode
  • As per API 610, 611, 612, 617, 672, 684, etc. (Any other API Standard)

In addition, the linearized coefficients are calculated for various bearing types with application of any seal type step by step. INERTANCE can provide various kinds of rotor dynamics analysis as requested in API standards as below.

Here, INERTANCE can show the various type of lateral vibration analysis as follows;

Lateral vibration (Rotordynamics)
Lateral vibration (Rotordynamics)

Critical Speed

The purpose of undamped critical speed map is to check the bearing stiffness briefly at initial design stage, and it could be used to expect the rotor’s behavior & sensitivity around its critical speed. The intersection between bearing stiffness and each natural frequency should be checked in order to determine if the designed equipment is stiff rotor or soft rotor. It should be noted that the undamped critical speed map shall not be used to assess the rotor reliability, as the bearings are estimated in absent of their damping and the aerodynamic cross-coupling for each impeller does not also included in this analysis. 


Mode Shape

Mode shape provides the approximate displacement of rotor relatively around critical speed, and it is determined that the unbalance location with phase is applied for response analysis.

Mode-Shape (Lateral-Analysis)
Mode-Shape (Lateral-Analysis)

Unbalance Response (Imbalance Response)

As one of rotordynamics analysis, Damped unbalance response analysis is performed to check the adequate separation margin between critical speeds and operating speeds, as well as to check  internal clearance limitation against rubbing, etc.

Unbalance-Response-Analysis (Imbalance-Response)
Unbalance-Response-Analysis (Imbalance-Response)

INERTANCE has a capability regarding noise and vibration engineering, and our experts are familiar with assessment of Lateral Vibration (Rotordynamics) Analysis. For further information, contact us at (

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