| Co-Investigator(Kenkyū-buntansha) |
NAKAHASHI Kazuhiro Tohoku University, Graduate School of Engineering, Professor, 大学院・工学研究科, 教授 (00207854)
KOHAMA Yasuaki Tohoku University, Institute of Fluid Science, Professor, 流体科学研究所, 教授 (60006202)
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| Research Abstract |
1) Wind tunnel experiments
First, PVDF attached on the surface of a flat plate was used to control the flow. The film was operated by a signal from a workstation, amplified by a high-speed power amplifier. Each film piece was controlled separately by different signals and it was shown that two-dimensional Tollmien-Schlichting wave and oblique waves of various sweep angles could be generated by this system.
Next, the flow controlling device was changed to a piezo-ceramic device. As a result, the system became capable of generating oblique waves of small sweep angles, which was difficult with the PVDF.In addition, by reducing the size of the devices and increasing their number, the freedom in the sweep angle of the wave increased.
The aim of the research which was to develop a technique to introduce various types of wave in the boundary layer was accomplished. However, due to the limitation in the experimental facility, we could not show that the system was capable of changing the transition point.
2) Numerical simulations
By using an orthogonal grid, the flow fields of the wind tunnel experiments were regenerated successfully. The result disclosed the complicated mechanism which takes place immediately after the controlling device before the wave develops. The result suggests that it is not essential for the edge of the actuator to be exposed the flow, and that there is a possibility that a flush-mounted device can be used to control the flow.
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