NLH Method

The Nonlinear Harmonic module


The Nonlinear Harmonic method can be used on both single or multi-stage turbomachinery configurations and allows a significant speed-up for unsteady analysis leading to a CPU gain of 2 to 3 orders of magnitude compared to full-unsteady simulations.

It decomposes the unsteady flow variables into time-averaged variables and periodic unsteady perturbations.

This unique technique computes the unsteady flow field by means of the Fourier decomposition of the periodic fluctuations based on a pre-selected number of harmonics, typically associated with the blade passing frequencies of the turbomachinery configuration and their multiples.

It also provides the full unsteady flow field predictions for the selected harmonics. Furthermore, because of the transposition to the frequency domain, only one blade channel is required.


  • Take advantage of the existing steady flow solver of FINE™/Turbo
  • Only one interblade channel is required like a steady flow simulation
  • The time-averaged flow solution incorporates the effects of the unsteadiness
  • Linear combination of blade passing frequencies can be solved
  • Clocking effects can be considered
  • Reduce the entropy discontinuity at the rotor/stator interface
  • Specific boundary conditions for distorsion effects and upstream wind with incidence


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