Abnormal changes of dynamic derivatives at low reduced frequencies

Weiwei ZHANG, Yiming GONG, Yilang LIU

Research output: Contribution to journalArticlepeer-review

12 Scopus citations

Abstract

A number of studies have found that abnormal changes of dynamic derivatives occurred at very low reduced frequencies, but its inducement mechanism is not very clear. This paper has researched the abnormal changes and analyzed the influence on some parameters by solving the unsteady flow around forced oscillation airfoils based on Navier-Stokes equations. Results indicate that when the reduced frequency approaches to zero, the dynamic derivatives obtained by the numerical method will diverge. We have also proven it in theory that this phenomenon is not physical but completely caused by numerical singularity. Furthermore, the abnormal phenomenon can be effectively mitigated by using the time spectral method to solve the aerodynamic forces and the integral method to obtain the dynamic derivatives. When the reduced frequency is in the range of 0.001–0.01, the dynamic derivative maintains nearly unchanged for the whole speed region. This study can provide a reference for the reasonable choice of the reduced frequency in calculations and experiments of dynamic derivatives.

Original languageEnglish
Pages (from-to)1428-1436
Number of pages9
JournalChinese Journal of Aeronautics
Volume31
Issue number7
DOIs
StatePublished - Jul 2018

Keywords

  • Dynamic derivatives
  • Numerical diverge
  • Reduced frequency
  • Time spectral method
  • Unsteady flow

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