| Budget Amount *help |
¥2,400,000 (Direct Cost: ¥2,400,000)
Fiscal Year 2002: ¥300,000 (Direct Cost: ¥300,000)
Fiscal Year 2001: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 2000: ¥1,300,000 (Direct Cost: ¥1,300,000)
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| Research Abstract |
The primary purpose of the present study is to know the aerodynamic forces acting on a macroscopic particle which undergoes a step change in its rotating and translating velocities, in particular, to investigate the effect of nonlinear interaction to the hydrodynamic forces, which may play an important role in the unsteady motion of the particle.
In the theoretical study, a two-dimensional circular cylinder, which starts impulsively with rotational motion, is mainly treated, using the method of the matched asymptotic expansion, which was proposed by the present investigator. The most important result is that the lift force is generated by the nonlinear interaction and its asymptotic behavior for the beginning of motion is dependent on the order of Reynolds number, that is, for the low Reynolds number it exhibits t^<-1/2> singularity, for the moderate Reynolds number it is a constant, and for the high Reynolds number it has t^<1/2>, where t is tune from the start.
In the numerical study, the vortex method is used in the present study, which may be powerful for the unsteady flow, and is developed to the extremely low Reynolds number flow. To confirm the validity of the vortex method the above mentioned theoretical problems are treated and the theoretical results are confirmed. In the three-dimensional flow, the stretching term plays an important role to the flow behavior, so in the present vortex method the concept of the PSE method is applied to this term and the flow around a sphere is calculated. The numerical results show that the PSE method for the stretching term is available.
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