Estimating local instabilities for irregular flows in the differentially heated rotating annulus

  • U. HarlanderEmail author
  • R. Faulwetter
  • K. Alexandrov
  • C. Egbers
Conference paper
Part of the Springer Proceedings in Physics book series (SPPHY, volume 132)


In stable flows, transient growth of ’non-normal’ modes can lead to turbulence. Usually, non-normal modes are computed from linearized model equations [1]. However, for some problems the proper set of equations is unknown, or unhandy for the purpose of finding non-normal modes. Therefore it is proposed to estimate non-normal modes from data alone, without using the model equations. Crucial for such an estimation is a good guess of the linear system matrix for the flow under consideration. Such a guess can be obtained following the approach by [2] discussed in the context of climate analysis. In the present paper a simple test case will be presented that demonstrates the suitability of the approach. Subsequently, the method is applied to temperature data from a differentially heated rotating annulus, a laboratory model that covers features of the large-scale atmospheric circulation [3]. The method proposed might help to gain insight into the spatial structures of local instability in annulus flows.


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Copyright information

© Springer-Verlag Berlin Heidelberg 2009

Authors and Affiliations

  • U. Harlander
    • 1
    Email author
  • R. Faulwetter
    • 2
  • K. Alexandrov
    • 1
  • C. Egbers
    • 1
  1. 1.Dept. of Aerodynamics and Fluid MechanicsBTU CottbusCottbusGermany
  2. 2.Dept. of Theoretical MeteorologyUniversity of LeipzigLeipzigGermany

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