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RISS 인기검색어
- 검색키워드
- 저자 : Koki Kitagawa (검색결과 2 건)
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Numerical analysis of multi-parallelized swirling flow inside a circular pipe
Akimasa Takayama,Koki Kitagawa,Toru Shimada 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.3
The flow field of multi-parallelized swirling flow inside a circular pipe was investigated numerically. Two types of swirling flow configurationare considered. One type is the co-rotating type. Four co-rotating swirls are arranged at the vertex position of square in thistype. The other type is the counter-rotating type which consists of two pairs of swirls having opposite swirl rotations. Each pair is arrangeddiagonally at the vertex position of a square. By coupling the discrete vortex method and boundary element method, unsteadyflow simulation is performed. Swirl modeling with vortex elements is used in this simulation and its validity is confirmed. From thesimulation results, in the co-rotating type, the four swirls interact and their shape is deformed. Each vortex motion vanishes rapidly in thedownstream region. Finally, they are turned into a single swirling flow. In counter-rotating type, each vortex motion is maintained a littlebit longer than co-rotating type, and their shape is not so deformed. However, the flow patterns are changed completely in the downstreamregion. The swirling velocity of each swirl mostly vanishes. Finally, they are turned into an axial flow. For the investigation of themixing promoting effect due to parallelizing swirls, particle tracking simulations are performed in the co-rotating type and the counterrotatingtype. As a comparison, the simulation for single swirl flow is also performed. In these simulations, the particles are introduced inthe vicinity of pipe inner wall. In addition, the assumption that particles follow the flow motion absolutely is used. From the results, themotion of particles in these three cases is completely different. For the co-rotating and counter-rotating type, the particle entrainment intothe main axial flow is clearly observed. This indicates the mixing is improved compared to single swirl flow. The difference of particleentrainment motion between co-rotating and counter-rotating type is slight.
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Design Optimization of Single-Stage Launch Vehicle Using Hybrid Rocket Engine
Kanazaki, Masahiro,Ariyairt, Atthaphon,Yoda, Hideyuki,Ito, Kazuma,Chiba, Kazuhisa,Kitagawa, Koki,Shimada, Toru The Society for Aerospace System Engineering 2015 International Journal of Aerospace System Engineer Vol.2 No.2
The multidisciplinary design optimization (MDO) of a launch vehicle (LV) with a hybrid rocket engine (HRE) was carried out to investigate the ability of an HRE for a single-stage LV. The non-dominated sorting genetic algorithm-II (NSGA-II) was employed to solve two design problems. The design problems were formulated as two-objective cases involving maximization of the downrange distance over the target flight altitude and minimization of the gross weight, for two target altitudes: 50.0 km and 100.0 km. Each objective function was empirically estimated. Several non-dominated solutions were obtained using the NSGA-II for each design problem, and in each case, a trade-off was observed between the two objective functions. The results for the two design problem indicate that economical performance of the LV is limited with the HRE in terms of the maximum downrange distances achievable. The LV geometries determined from the non-dominated solutions were examined.
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