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RISS 인기검색어
- 검색키워드
- 저자 : Etsuo Morishita (검색결과 3 건)
- 무료
- 기관 내 무료
- 유료
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Numerical Analysis of Flapping Wing
Hiroaki Matsutani,Etsuo Morishita,Hisao Koyama,Takeo Okunuki 한국항공우주학회 2008 한국항공우주학회 학술발표회 논문집 Vol.- No.-
Micro Air Vehicles (MAVs) are very small and fly at low speeds. Therefore, their wings are flat plates or membranes because the Reynolds number is very low. For MAVs, a flapping wing is proposed to generate lift and thrust simultaneously like birds and insects. In this study, the Immersed Boundary Method with the original ideas is used to analyze the airflow around stationary, heaving and feathering flat-plate numerically. The advantages of this method are easiness of the grid generation and less amount of calculation. The grid is not body-fitted but rectilinear. And the plate is expressed by the external force. The computational results are compared with the analytical solutions and the experimental photo. In the stationary plate, the drag coefficient and the velocity distribution agree with the Blasius solution. In the heaving plate, the lift and moment coefficients are close to the analytical solution with the Theodorsen function. And the pressure contours and the streamlines show the plate exists in the grid. In the feathering plate, the vorticity distribution and the experimental result show the similar trend.
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Numerical Analysis of Drag and Heating Reduction by Directed Energy Air Spike
Sho Sasamoto,Etsuo Morishita 한국항공우주학회 2008 한국항공우주학회 학술발표회 논문집 Vol.- No.-
It is well known to the aerospace engineering community that aerodynamic drag and heating are extremely critical issues at hyper velocities. Directed Energy Air Spike (DEAS) is a method to deposit a small amount of energy in the flow ahead of a blunt body and to reduce the drag and the heating. The hypersonic flow at M=7 past the blunt body is investigated numerically. The axis-symmetric bodies are studied. The compressible Navier-Stokes Equations are solved by the AUSM-DV scheme. The effects of heat addition and its location are of a particular interest in the present calculation. And the computational results show that optimum amount and location of the heat addition could be determined aerodynamically. The present calculations also confirm that DEAS is a very effective method for the drag and heat transfer reduction at hypersonic speeds.
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Numerical Analysis of Flows around a Sphere
Genichiro Ebe,Etsuo Morishita 한국항공우주학회 2008 한국항공우주학회 학술발표회 논문집 Vol.- No.-
A sphere is a simple structure and it is used in many things, particularly in sports fields. A soccer ball is an example. There exists a critical Reynolds number around at Re = 10? and sharp drag reduction is observed. This is caused by a transition from a laminar boundary layer to a turbulent one. The present authors attempt to analyze a flow around a sphere numerically. Our particular interest is to invcstigatc the three-dimensional unsteady flow of a sphere. The MAC method is used to solve the incompressible Navier Stokes equations. A special grid is developed for the present calculations. Singularities around poles are carefully avoided by combining two polar meshes. It is found that the wake of a sphere is complicated and unsteady movements is dominant at Re = 10³~10⁴ range. The periodicity is also observed, although it is not regular as in the two-dimensional Karman vortex street. Two of the three vortex components are stationary on the latter surface of a sphere, while the rest of the vortex components shows a very complex movement. The present study might contribute to the understanding of the How around the soccer ball, together will, other spherical objects in the sports field.
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