Excitation of unsteady Görtler vortices by localized surface nonuniformities
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- 作者：A. V. Boiko ; A. V. Ivanov ; Yu. S. Kachanov…
- 关键词：Boundary layer ; Görtler vortices ; Surface roughness ; Surface vibrations ; Receptivity ; Instability ; Optimal disturbances ; Local modes
- 刊名：Theoretical and Computational Fluid Dynamics
- 出版年：2017
- 出版时间：February 2017
- 年：2017
- 卷：31
- 期：1
- 页码：67-88
- 全文大小：
- 刊物类别：Physics and Astronomy
- 刊物主题：Engineering Fluid Dynamics; Classical and Continuum Physics; Computational Science and Engineering;
- 出版者：Springer Berlin Heidelberg
- ISSN：1432-2250
- 卷排序：31
文摘
A combined theoretical and numerical analysis of an experiment devoted to the excitation of Görtler vortices by localized stationary or vibrating surface nonuniformities in a boundary layer over a concave surface is performed. A numerical model of generation of small-amplitude disturbances and their downstream propagation based on parabolic equations is developed. In the framework of this model, the optimal and the modal parts of excited disturbance are defined as solutions of initial-value problems with initial values being, respectively, the optimal disturbance and the leading local mode at the location of the source. It is shown that a representation of excited disturbance as a sum of the optimal part and a remainder makes it possible to describe its generation and downstream propagation, as well as to predict satisfactorily the corresponding receptivity coefficient. In contrast, the representation based on the modal part provides only coarse information about excitation and propagation of disturbance in the range of parameters under investigation. However, it is found that the receptivity coefficients estimated using the modal parts can be reinterpreted to preserve their practical significance. A corresponding procedure was developed. The theoretical and experimental receptivity coefficients are estimated and compared. It is found that the receptivity magnitudes grow significantly with the disturbance frequency. Variation of the span-wise scale of the nonuniformities affects weakly the receptivity characteristics at zero frequency. However, at high frequencies, the efficiency of excitation of Görtler vortices depends substantially on the span-wise scale.