2004 Fiscal Year Final Research Report Summary
Feedback Control of Nonlinear Thermocapillary Convection in a Half-zone Liquid Bridge
| Project/Area Number |
14350114
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (B)
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
Thermal engineering
|
|---|
| Research Institution | Faculty of Science & Technology, Tokyo University of Science |
|---|
Principal Investigator |
KAWAMURA Hiroshi Tokyo University of Science, Faculty of Science & Technology, Professor, 理工学部, 教授 (80204783)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
NISHINO Koichi Yokohama National University, Department of Mechanical Engineering, Professor, 工学研究院・システムの創成部門, 教授 (90192690)
UENO Ichiro Tokyo University of Science, Faculty of Science & Technology, Assistant Professor (Ichiro Ueno left this project on 26 August 2004, because of the sabbatical leave.), 理工学部, 講師(在外研究のため途中辞退平成16年8月26日承認) (40318209)
|
|---|
| Project Period (FY) |
2002 – 2004
|
| Keywords | Microgravity / Thermocapillary convection / Floating-zone crystal growth / Half-zone model / Active control / Oscillatory convection |
|---|
| Research Abstract |
In the microgravity condition, a buoyancy-driven convection becomes almost negligible. The floating-zone(FZ) crystal growth is a containerless method to produce high-quality semiconductors and oxides under the microgravity. In this method, a transition to three-dimensional oscillatory thermocapillary convection takes place with increasing temperature difference between the heated area and cold rods or with increasing Marangoni number Ma. It is widely known that the oscillatory convection causes detrimental defects in the crystal structure even in the space environment. Control of the convection is of great importance in order to establish high-quality material processing techniques.
As the fundamental research, a half-zone model(HZ) has been employed to simplify the thermocapillary convection in FZ. A large number of research were conducted with respect to the transition and successive flow structures in the HZ liquid bridge. Only a few works have been concerned with a control of the convection.
The present study aims to suppress the three-dimensional oscillatory thermocapillary convection in the HZ liquid bridge in a wide range of Ma. The control was applied by modifying the free surface temperature locally with the electric heaters. The control output was calculated by the simple cancellation algorithm using local surface temperature signals. In order to develop control schemes, the oscillatory convection was measured by the three-dimensional particle tracking velocimetry.
Through the experiments, significant attenuation of the oscillation was obtained for a wide range of Ma. The complete suppression of the oscillatory convection was achieved close to the critical point of the transition. The control scheme achieved a significant reduction of the temperature oscillation, also far beyond the critical point.
|
