著者

東 大輔 中村 佳朗

出版者

一般社団法人 日本航空宇宙学会

雑誌

日本航空宇宙学会論文集 (ISSN:13446460)

巻号頁・発行日

vol.51, no.589, pp.52-60, 2003 (Released:2003-09-16)

参考文献数

17

被引用文献数

3 3

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The subsonic flow for a 45 deg-swept delta wing was numerically simulated to see the effects of rotational leading edges on aerodynamic forces. In the present study, part of the cylindrical leading edge can be rotated which extends from x=0.25C to 0.90 C. The computation has been performed at an angle of attack of 20 deg and a Reynolds number of 2.0×104 based on the maximum wing root chord. Under these conditions, the flow is fully separated from the wing surface in the case without leading edge rotation, so that no suction peaks due to leading edge vortices appear over the upper surface of the wing. Consequently, the delta wing will not have an effective vortical lift. In the case of steady rotation, leading edge vortices were produced on the wing in the early stage. However, a gradual drop in lift coefficient occurred as a result of the diffusion of these vortices. By contrast, in the case of unsteady rotation, a pair of leading edge vortices was maintained, so that a higher lift was produced. Consequently, the lift coefficient became more than 40% higher than that of the plain delta wing.

著者

上野 陽亮 中村 佳朗

出版者

一般社団法人 日本航空宇宙学会

雑誌

日本航空宇宙学会論文集 (ISSN:13446460)

巻号頁・発行日

vol.57, no.667, pp.317-322, 2009 (Released:2009-08-17)

参考文献数

13

被引用文献数

2 1

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A numerical simulation method taking into account both aerodynamics and flight dynamics has been developed to simulate the flight of a low speed flying object, where it undergoes unsteady deformation. This method can also be applied to simulate the unsteady motion of small vehicles such as micro air vehicles (MAV). In the present study, we take up a bird and demonstrate its flight in the air. In particular the effect of fluid forces on the bird's flying motion is examined in detail, based on CFD×CFD: Computational Fluid Dynamics (CFD) and Computational Flight Dynamics. It is found from simulated results that this bird can generate lift and thrust enough to fly by flapping its wing. In addition, it can make a level flight by adjusting its oscillation frequency. Thus, the present method is promising to study the aerodynamics and flight dynamics of a moving object with its shape morphing.

著者

香山 寛人 汪 運鵬 小澤 啓伺 土井 克則 中村 佳朗

出版者

一般社団法人 日本航空宇宙学会

雑誌

日本航空宇宙学会論文集 = Journal of the Japan Society for Aeronautical and Space Sciences (ISSN:13446460)

巻号頁・発行日

vol.60, no.2, pp.74-79, 2012-04-05

参考文献数

12

被引用文献数

1

---

The space transportation system will need advanced abort systems to secure crew against serious accidents. Here this study deals with the capsule-type space transportation systems with a Launch Abort System (LAS). This system is composed of a conic capsule as a Launch Abort Vehicle (LAV) and a cylindrical rocket as a Service Module (SM), and the capsule is moved away from the rocket by supersonic aerodynamic interactions in an emergency. We propose a method to improve the performance of the LAV by installing fences at the edges of surfaces on the rocket and capsule sides. Their effects were investigated by experimental measurements and numerical simulations. Experimental results show that the fences on the rocket and capsule surfaces increase the aerodynamic thrust force on the capsule by 70% in a certain clearance between the capsule and rocket. Computational results show the detailed flow fields where the centripetal flow near the surface on the rocket side is induced by the fence on the rocket side and the centrifugal flow near the surface on the capsule side is blocked by the fence on the capsule side. These results can confirm favorable effects of the fences on the performance of the LAS.

著者

土井 克則 Mohd FADHLI 川島 渉 中村 佳朗

出版者

一般社団法人 日本航空宇宙学会

雑誌

日本航空宇宙学会論文集 = Journal of the Japan Society for Aeronautical and Space Sciences (ISSN:13446460)

巻号頁・発行日

vol.59, no.693, pp.273-280, 2011-10-05

参考文献数

14

被引用文献数

3

---

A boomerang thrown properly into the air can fly in an elliptical path and return to the point of origin. In this study, such a motion of the boomerang was numerically simulated to clarify the mechanism of the motion. The simulation was conducted by the double CFD method which is the coupling method of the computational fluid dynamics and the computational flight dynamics. We considered the case that a small flat boomerang was thrown with a translational and a rotational velocity, an angle of the translational velocity from a horizontal plane, and no roll angle. Results showed that the boomerang lifted and traveled in a path with changing roll and pitch angles due to a pressure distribution on its surface, and returned to a point near the origin. Furthermore, an experiment was performed to confirm the validity of the computational results, and the experimental result was qualitatively corresponding to the computational results.

著者

松野 隆 横内 滋 中村 佳朗

出版者

一般社団法人 日本航空宇宙学会

雑誌

日本航空宇宙学会論文集 (ISSN:13446460)

巻号頁・発行日

vol.52, no.601, pp.80-86, 2004 (Released:2004-04-30)

参考文献数

15

被引用文献数

1 1

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This paper describes the mechanism of the non-slender wing rock that occurs on a 45° delta wing, by focusing on its unsteady aerodynamic characteristics. In free-to-roll test the wing motions showed irregular oscillations the amplitude of which varied with time. In some cases, the wing suddenly changed its trajectory in the middle of the oscillation, and came to stop at roll angle φ=0°. The static rolling moment is quite nonlinear in characteristics, the profile of which has many critical states. The balance test for constant roll rate motion showed that the amount of time lag was not constant for roll angle, and that it is not linear for roll rate. The results of numerical simulation using the experimental data suggest that it is important to take into account the trajectory of the motion for a better understanding about the unsteady aerodynamic characteristics, associated with the non-slender wing rock.

著者

甲村 圭司 中村 佳朗

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集B編 (ISSN:18848346)

巻号頁・発行日

vol.79, no.804, pp.1489-1499, 2013 (Released:2013-08-25)

参考文献数

10

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Aerodynamic noise with discrete frequencies is generated in an unexpected way from a slit between a flat plate, which is placed in parallel to the main flow, and a wedge that is placed normal to the flow. To study this phenomenon, we examined the discrete frequency noise generated by a subsonic air jet flow from a slit. It was found that the slit height and the plate length have considerable effects on the noise generation. In addition, the discrete frequency noise was generated only when the values of these parameters are within a limited range. Furthermore, it was found that the noise frequency is proportional to the jet velocity and is inversely proportional to the plate length. Finally, it was made clear from the present study that the interaction of the vortex, which is generated from the shear layer due to a wedge, with the wake of a flat plate is a major cause for the discrete noise due to a slit.

著者

斎藤 崇雄 中村 哲也 メンショフ・イゴール 中村 佳朗 前田 一郎 内山 直樹 海田 武司

出版者

日本流体力学会

雑誌

日本流体力学会年会講演論文集 (ISSN:13428004)

巻号頁・発行日

vol.2003, pp.480-481, 2003-07-28

被引用文献数

1

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The phenomena of ignition overpressure (IOP) has been simulated in two cases with the specific heat ratio γ=1.18 and γ=1.4. The former case assumes that a combustion gas fills the overall computational region, while the latter assumes air instead of the combustion gas. The objective of the present study is to investigate whether IOP is affected by the kind of gas. This simulation was performed for a solid rocket booster (SRB) of space shuttle. The time history of pressure rise at the nozzle inlet was taken into account by imitating the SRB ignition. The result with γ=1.18 shows good agreement with the data measured on the surface of STS-Ts SRB.