Hisashi Minakuchi
University of the Ryukyus
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Publication
Featured researches published by Hisashi Minakuchi.
International Journal of Materials & Product Technology | 2005
Hisashi Minakuchi; Yasunori Okano; Sadik Dost
The article presents a three-dimensional computational study for the transport phenomena occurring during the growth of Si-doped Ge crystals by the Floating-Zone (FZ) technique. Numerical simulations were performed to examine the role of the Marangoni convection in a Full-zone configuration under zero gravity. The effects of crystal rotation and zone aspect ratio were also considered in the model. The field equations of the liquid phase and the associated boundary conditions were discretised by the finite difference method, and solved by the HSMAC (Highly Simplified Marker And Cell) method. Results show that the flow and temperature fields are initially two-dimensional with two pairs of vortexes of the same size, as time proceeds, however the flow field becomes three-dimensional in spite of assumed axisymmetric boundary conditions. The concentration field becomes three-dimensional much earlier than the flow field. The float zone aspect ratio has a prominent effect on the critical Marangoni number at which three-dimensional flow structures occur, and as well as on the azimuthal wave number and the uniformity of the solute concentration along the crystal growth interface in the melt. It was also shown that the application of a crystal rotation is very beneficial in obtaining a moreuniform solute concentration distribution along the growth interface.
International Conference on Global Research and Education | 2018
Chihao Jin; Atsushi Sekimoto; Yasunori Okano; Hisashi Minakuchi
Marangoni convection is a flow along the interface between two fluids due to the variation of surface tension, which is mainly caused by temperature and/or concentration gradients, namely thermal and/or solutal Marangoni convection(s). During the crystal growth by the floating zone method, Marangoni convection may induce the striation and affect the quality of growing crystal. Therefore, it is necessary to understand the convective phenomenon and control it. In this study, a three-dimensional configuration of the half-zone liquid bridge in the crystal growth of SixGe1-x was selected by establishing the temperature and concentration differences. The equations of continuity, momentum, energy and mass transfer were solved by the PISO algorithm in the OpenFOAM. Thermal and solutal Marangoni convections were set to flow in the opposite direction under zero gravity in the melt with different Marangoni numbers. Results have shown that when MaC is larger than −MaT, the flow is steady and axisymmetric, while MaC is smaller than −MaT, the flow is unsteady and irregular. As for the control of Marangoni convection, rotation of top and bottom plane in the liquid bridge was applied during the crystal growth. With different rotation speeds and directions, the suppression of Marangoni convection can be effectively realized by the appropriate forced rotation.
Journal of Crystal Growth | 2014
Hisashi Minakuchi; Youhei Takagi; Yasunori Okano; Satoru Gima; Sadik Dost
Journal of Crystal Growth | 2014
Youhei Takagi; Yasunori Okano; Hisashi Minakuchi; Sadik Dost
Desalination and Water Treatment | 2010
Takehiro Nosoko; Satoru Gima; Hisashi Minakuchi; K. Ameku; K. Irabu
Journal of Crystal Growth | 2017
Hisashi Minakuchi; Yasunori Okano; Sadik Dost
Transactions of The Japan Society for Aeronautical and Space Sciences, Space Technology Japan | 2012
Hisashi Minakuchi; Youhei Takagi; Yasunori Okano; Takehiro Nosoko; Satoru Gima; Sadik Dost
THMT-12. Proceedings of the Seventh International Symposium On Turbulence, Heat and Mass Transfer Palermo, Italy, 24-27 September, 2012 | 2012
Hisashi Minakuchi; Youhei Takagi; Yasunori Okano; Satoru Gima; Sadik Dost
International Communications in Heat and Mass Transfer | 2011
Takehiro Nosoko; K. Ameku; Hisashi Minakuchi
The Proceedings of The Computational Mechanics Conference | 2015
Koki Nishime; Tatsuya Yoshino; Hisashi Minakuchi; Yasunori Okano