|
|
|
KTH /
Engineering Sciences /
Mechanics /
Research /
Publication list /
Publication information
Article information
Spectral analysis of nonlinear flows
| Authors: |
Rowley, W,
Mezic, ,
Bagheri, S.,
Schlatter, P.,
Henningson, D.S.H.,
|
| Type: |
Article |
| Pubstate: |
Published |
| Journal: |
J. Fluid Mech. |
| Volume: |
641
115-127 |
| Year: |
2009 |
Abstract
We present a technique for describing the global behavior of complex, nonlinear flows, by decomposing the flow into modes determined from spectral analysis of the Koopman operator, an infinite-dimensional linear operator associated with the full nonlinear system. These modes, referred to as Koopman modes, are associated with a particular observable, and may be determined directly from data (either numerical or experimental) using a standard Arnoldi algorithm. They have an associated temporal frequency and growth rate and may be viewed as a nonlinear generalization of global eigenmodes of a linearized system. They provide an alternative to Proper Orthogonal Decomposition, and in the case of periodic data the Koopman modes reduce to a discrete temporal Fourier transform. We illustrate the method on an example of a jet in crossflow, and show that the method captures the dominant frequencies and elucidates the associated spatial structures.
|
|
|
