Transitional wake flow behind an inclined flat plate : computation and analysis
Doctoral thesis
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Date
2013Metadata
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- Institutt for marin teknikk [3469]
Abstract
The flow past an inclined flat plate is characterized by fixed separation points at both edge and an asymmetric wake pattern. The present doctoral thesis investigates the threedimensional characteristics in the wake of an inclined flat plate. Direct numerical simulations were performed to study the intrinsic three-dimensionalities in the wake. Both regular and irregular vortex shedding patterns were found at different angles of attack as the Reynolds number increases. For the regular vortex shedding, the spanwise wavelength was measured and compared with previous investigations of other cylindrical bluff bodies. Due to the nonlinear effect, the irregular vortex shedding showed the modulation of vortex shedding along the plate span, and not perfectly periodic-like beating behavior was found in the velocity signals. This phenomenon is associated with the random appearance of vortex dislocations.
Time-frequency analysis was carried out to understand the features imbedded in the velocity signals by using different methods, i.e. Fourier transform, wavelet transform and Hilbert-Huang transform.
Furthermore, the Floquet stability analysis was adopted to show the onset of the threedimensionality in the wake. The results show similar flow patterns with the threedimensional simulations