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Linear Stability Analysis of Open-Channel Shear Flow Generated by Vegetation
| Title: | Linear Stability Analysis of Open-Channel Shear Flow Generated by Vegetation |
| Authors: | de Lima, Adriano C Browse this author | | Izumi, Norihiro Browse this author |
| Keywords: | Linear stability analysis | | Shear flow | | Flow instability | | Kinematic eddy viscosity | | Lateral vortices. |
| Issue Date: | 2014 |
| Publisher: | ASCE |
| Journal Title: | Journal of Hydraulic Engineering |
| Volume: | 140 |
| Issue: | 3 |
| Start Page: | 231 |
| End Page: | 240 |
| Publisher DOI: | 10.1061/(ASCE)HY.1943-7900.0000822 |
| Abstract: | A linear stability analysis of flow in an open-channel partially covered with vegetation was performed. The differential drag 5 between vegetated zones and adjacent nonvegetated zones is known to induce a lateral gradient of the streamwise velocity. The velocity 6 gradient may result in flow instability in the shear layer around the edge of the vegetated zone causing the generation of discrete horizontal 7 vortices.We assume that the base state flow field before the occurrence of instability is characterized by turbulence with a smaller length scale 8 2 than the flow depth, which is mainly generated by the bottom friction. By introducing perturbations to the flow depth as well as the stream- 9 wise and transverse velocities in the base state, the conditions required for perturbations to grow in time were studied over a wide range of 10 (1) Froude number, (2) normalized nonvegetated zone width, and three other dimensionless parameters that represent the relative effect of 11 (3) bed friction, (4) vegetation drag, and (5) subdepth eddy viscosity. All parameters were found to have positive and negative growth rates of 12 perturbations within their respective evaluated ranges. The characteristic vortex shedding frequencies associated with the maximum growth 13 rate was compared with those observed in experiments. Although the analysis that employs a base state set without the large scale lateral 14 motions was shown to be capable of predicting the order of magnitude of the frequencies, there is a systematic discrepancy between the 15 predicted and observed frequencies, which may be due to the limitation of linear stability analysis. |
| Type: | article (author version) |
| URI: | http://hdl.handle.net/2115/66484 |
| Appears in Collections: | 工学院・工学研究院 (Graduate School of Engineering / Faculty of Engineering) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)
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