Three-dimensional Instability of the Flow Induced around an Oscillating Cylinder in a Density Stratified Fluid at Rest

Research Project

Project/Area Number	06640528
Research Category	Grant-in-Aid for General Scientific Research (C)
Allocation Type	Single-year Grants
Research Field	物理学一般
Research Institution	KYUSYU UNIVERSITY
Principal Investigator	TATSUNO Masakazu Kyushu University, Research Institute for Applied Mechanics, Associate Professor, 応用力学研究所, 助教授 (70038553)
Co-Investigator(Kenkyū-buntansha)	KARASUDANI Takashi Kyushu University, Research Institute for Applied Mechanics, Research Associate, 応用力学研究所, 助手 (30150527)
Project Period (FY)	1994 – 1995
Project Status	Completed (Fiscal Year 1995)
Budget Amount *help	¥2,100,000 (Direct Cost: ¥2,100,000) Fiscal Year 1995: ¥300,000 (Direct Cost: ¥300,000) Fiscal Year 1994: ¥1,800,000 (Direct Cost: ¥1,800,000)
Keywords	Stratified Fluid / Oscillating Motion / Non-linearlity / Secondary Flow / Three-dimensional Instability
Research Abstract	The structures of the flow induced by a vertical circular cylinder performing transverse oscillations in a linearly stratified fluid at rest are investigated. The density gradient inhibits the onset of the three-dimensional instability. The instability appears as regularly spaced streaked flows along the cylinder axis. Each streaked flow is shed being oscillated along the cylinder surface. Regularly spaced streaked flows arrange themselves alternately along the cylinder axis as the oscillating motion of a streaked flow is 180ﾟ out of phase with adjacent streaked flows. When the non-dimensional amplitude or frequencies are increased beyond critical values, the streaked flows generated alternately along the cylinder axis do not oscillate along the cylinder surface but extend straight in the direction of cylinder oscillation in the same manner as in the homogeneous fluid.