| Budget Amount *help |
¥3,000,000 (Direct Cost: ¥3,000,000)
Fiscal Year 2005: ¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 2004: ¥800,000 (Direct Cost: ¥800,000)
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| Research Abstract |
The numerical study was conducted on the fluid phenomenon of the low Reynolds number and high Mach number flow, which are typical flows around a small flight vehicle planned to be used in the planetary exploration in the near future. The aerodynamic characteristic in the low Reynolds number flow was analyzed for a typical airfoil (NACA4402). The effect of the Reynolds number and the Mach number, and unsteadiness of the fluid dynamics were analyzed. Moreover, the numerical analysis technique for unsteady flow around moving body was developed in order to investigate flow around flapping wings which are considered to be a highly effective propulsion system in the low Reynolds number flow.
1.Analysis of aerodynamic characteristic of a typical airfoil in the low Reynolds number flow.
(1)Aerodynamic characteristics in the low Reynolds number flow were investigated for a typical airfoil (NACA4402) around Reynolds number 1000. Comparing with usual high Reynolds number flows (for instance, Re=10^
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6), the low Reynolds number flow shows following features. The drag of the airfoil becomes larger. The lift-to-drag ratio (L/D) becomes smaller. The stall angle becomes smaller and flow becomes easier to separate Moreover, the dependence of aerodynamic characteristics on the Reynolds number is greater than that on the Mach number, and the great degradation of aerodynamic characteristics and the change of flow separation behavior are occurred on the boundary of a certain Reynolds number.
(2)The flow is easy to separate and unsteadiness is essential in the low Reynolds number flow. However, steady is good in the aerodynamic performance, especially for the value of L/D.
2.Development of numerical analysis technique for the flow around flapping wing
The numerical analysis technique, which can analyze unsteady flow around moving body accurately, was developed in order to analyze flow around flapping wings. The effect of the moving body was considered as the movement of the computational grid according to the movement of the body. A simple test calculation shows that unsteady flow around moving body is correctly calculated. Moreover, the developed program being applied to the flow around the forced oscillating airfoil was validated. Less
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