| Budget Amount *help |
¥3,700,000 (Direct Cost: ¥3,700,000)
Fiscal Year 2004: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 2003: ¥2,600,000 (Direct Cost: ¥2,600,000)
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| Research Abstract |
Recently, there are so many researches and developments in order to design and make the micro machine in blood vessels. The unsteady fluid flow in a small diameter tube is laminar and the effect of viscosity becomes so large that it can no more be disregarded as compared to gravity and inertia. The behavior of fluid flow will be dynamically unstable and many flow patterns will occur due to the small clearance between a sphere and the tube. However, there is still so few researches associated with such phenomena because it is difficult to analyze in a three dimensional space.
This research investigates numerically and experimentally the motion of a sphere of density ρ_s and diameter D_s, and flow field in small-diameter tube filled with fluid of density ρ and kinematic viscosity υ, under the external constant force of gravity acceleration G parallel to the pipe axis. The marker and cell method is used to calculate numerically, and the flow field is assumed to be axisymmetric. There are three dimensionless parameters in this system, i.e., Galilei No.Ga=D_s^3G/υ^2, the tube-diameter ratio d=D/D_s, and the density difference ratio α=(ρ_s - ρ)/ρ. The tube-diameter ratio d and the density difference ratio α are changed in this research, though Ga is constant.
As a main result, the following conclusions are obtained from the numerical analysis ;
(1)The dimensionless terminal velocity of a sphere ν_<bterr>=V_<Bter>υ/(αD_s^2G) does not change with increasing the product of α and Ga for the case that d is small value.
(2)The streamline around a moving sphere in a small-diameter tube is elliptical. The length of streamline behind a sphere increases with increasing d and αGa.
The theoretically predicted characteristics of unsteady laminar fluid flow around the sphere and the motion of the sphere are confirmed qualitatively in experiments.
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