著者

伊藤 慎一郎 加瀬 光輝

出版者

一般社団法人 日本機械学会

雑誌

流体工学部門講演会講演論文集 2013 (ISSN:24242896)

巻号頁・発行日

pp._G1104-01_-_G1104-03_, 2013-11-09 (Released:2017-06-19)

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A flying disc can fly through the air because of the combination of the lift and drag forces by the oncoming air flow. Actual fight conditions were confirmed to perform the wind tunnel experiment beforehand. In order to clarify the mechanism of flight of flying discs, the flow field structure and the fluid force were investigated on non-spinning and spinning conditions. In the fluid force measurement, lift and drag forces were taken by varying wind speeds, spin speeds, and angle of attack. Drag and lift forces were found to increase as spin increased. The angle of attack on the maximum range of lift-drag ratio or glide ratio was found to be wide from 6 to 13 degrees which was suitable for a long distance throwing. Using a smoke wind tunnel, flow visualization around the disc was performed in order to understand the effect of disc spin. It was found that spin enhances lift force by attracting the Coanda effect on the trailing edge.

著者

深見 開 深潟 康二 平 邦彦

出版者

一般社団法人 日本機械学会

雑誌

流体工学部門講演会講演論文集 2019 (ISSN:24242896)

巻号頁・発行日

pp.OS8-01, 2019 (Released:2020-07-25)

被引用文献数

4 4

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We use machine-learning-based super-resolution analysis to reconstruct high-resolution flow field data from grossly coarse low-resolution data, for three-dimensional fully developed turbulent channel flow at Reτ = 180. The training data is obtained by three-dimensional direct numerical simulation (DNS). We use an average pooling operation used commonly in image tasks, to prepare the coarse input data set. As a machine learning model, the hybrid downsampled skip-connection multi-scale (DSC/MS) model based on convolutional neural network is utilized in this study. Remarkable about this model are its robustness against rotation/translation of the flow images and its ability to consider multi-scale property of turbulence. The super-resolved flow fields recovered through the proposed machine learning model are in agreement with the reference DNS data in terms of velocity color distributions, root mean squared values of velocity fluctuations and L2 error norm defined as the difference between the reference DNS data and super-resolved flow field. The maximum wavenumbers of streamwise and spanwise energy spectrum recovered by machine learning are increased by the super-resolution reconstruction. The proposed method holds great potential for various applications in experimental and numerical situations to handle the fluid big data efficiently, e.g., PIV measurements and subgrid-scale modeling of large-eddy simulation.

著者

吉竹 直樹 張 慧 萩原 良道

出版者

一般社団法人 日本機械学会

雑誌

流体工学部門講演会講演論文集 2007 (ISSN:24242896)

巻号頁・発行日

pp._114-a_, 2007-11-17 (Released:2017-06-19)

著者

荻野 琢己 飯田 明由 大田 浩嗣 杉田 光弘

出版者

一般社団法人 日本機械学会

雑誌

流体工学部門講演会講演論文集 2019 (ISSN:24242896)

巻号頁・発行日

pp.IS-29, 2019 (Released:2020-07-25)

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The aim of this investigation is to estimate drag force acting on a bicycle helmet and power required for wind speed of bicycle race. It is known that a helmet of bicycle race has not only role to protect the head but also reduce aerodynamic drag force. Since the required power of caused by aerodynamic force acting on the helmet and head is about 18% of the total power of cycling, development of the low drag force helmet is required. To evaluate and understand the unsteady aerodynamic force and its generation mechanism, LES analysis was performed. As a result, the streamlined shape helmet placed in straight against the flow has low drag, but the drag force rapidly increases in the posture during goal sprinting. Therefore, the power required for top speed of bicycle race is more than three times that in steady state. Since, the flow around the helmet is unsteady, the maximum fluid force reaches 3.5 times that of the average. For this reason, it is required to develop robust shape helmet against changes in posture with small fluctuating drag force.

著者

藤田 健

出版者

一般社団法人 日本機械学会

雑誌

流体工学部門講演会講演論文集 2009 (ISSN:24242896)

巻号頁・発行日

pp.3, 2009-11-06 (Released:2017-06-19)

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R&D study of Mitsubishi Regional Jet (MRJ) has been conducted since 2003, under the auspice from NEDO. In this study, various fundamental research items for aircraft development including advanced aerodynamics, noise study and multidisciplinary design optimization (MDO) have applied to the design of MRJ. In these R&D activities, state-of-the-art technology developments have been pursued by strong university-government-industry cooperation. This report presents application of CFD and MDO technologies to MRJ design as an example of R&D activities.

著者

渡邊 大賀 松村 昌典

出版者

一般社団法人 日本機械学会

雑誌

流体工学部門講演会講演論文集 2021 (ISSN:24242896)

巻号頁・発行日

pp.OS03-03, 2021 (Released:2022-06-25)

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Three-dimensional structures such as longitudinal vortex appear in the two-dimensional vortex street wake of a cylinder. These structures are very complex structures. It is important to understand the details of the three-dimensional structures in the two-dimensional vortex street wake. The purpose of this study is to construct the three-dimensional structures from layered cross-sectional images and to understand its structures. In the flow visualization, four cylinders with different diameter were used to change the Reynolds number. The 3D structure constructed in this study could be observed from any angles and the details of its structures were revealed.

著者

高田 稜一 高橋 江梨香 内田 孝紀 杉谷 賢一郎 谷川 博哉 野口 尚史 平田 勝哉

出版者

一般社団法人 日本機械学会

雑誌

流体工学部門講演会講演論文集 (ISSN:24242896)

巻号頁・発行日

pp.OS03-05, 2020 (Released:2021-05-25)

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In the present study we investigate the relationship between various aerodynamic characteristics and attack angle α for FP (a flat plate), NACA0015 and iNACA0015 (the NACA0015 placed back to front) by numerical analysis and water-tank experiment at Re = 100 – 800. Then, we reveal the effects of α upon various aerodynamic characteristics such as the lift coefficient CL, drag coefficient CD and the lift-to-drag ratio CL/CD. In order to discuss these revealed α effects, we further visualize the flow around the airfoils in terms of the velocity vector, vorticity and the Q value at α = 0 – 30 deg., based on PIV analyses by water-tank experiment. Such results suggest that FP is similar not with NACA0015 but with iNACA0015 from an aerodynamic point of view.

著者

石原 裕二

出版者

一般社団法人 日本機械学会

雑誌

流体工学部門講演会講演論文集 2019 (ISSN:24242896)

巻号頁・発行日

pp.IS-28, 2019 (Released:2020-07-25)

著者

吉田 直之 加瀬 篤志 田地川 勉 板東 潔

出版者

一般社団法人 日本機械学会

雑誌

流体工学部門講演会講演論文集 2013 (ISSN:24242896)

巻号頁・発行日

pp._1202-01_-_1202-03_, 2013-11-09 (Released:2017-06-19)

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The purpose of this study is elucidating the mechanism of mosquito's flight. The motion of mosquito's wings consists of three representative motion; flapping, lead-lug and feathering motion. The feathering motion is a rotational movement which is centering on a wing leading edge. The mosquitoes are performing this motion passively produced by fluid forces and so on. In order to build the enlarged model which simulates this motion, we need to measure the stiffness of the mosquito's wings. The bending stiffness of the mosquito's wings were measured by the experiment using a cantilever. The enlarged wing model was designed based on its results. We observed the flapping motion of the enlarged wing model in the very low velocity wind tunnel and verified whether the feathering motion can be simulated.

著者

細谷 直人 山川 勝史 松野 謙一

出版者

一般社団法人 日本機械学会

雑誌

流体工学部門講演会講演論文集 2013 (ISSN:24242896)

巻号頁・発行日

pp._G0401-01_-_G0401-02_, 2013-11-09 (Released:2017-06-19)

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The most difficult way to prevent infection among some infection routes is viral droplet nuclei transmission. Droplet nuclei are generated during coughing and sneezing, and suspend for a long time. Hence, specifying its infection route is important issue. The behavior of the droplets is governed by the physical principles. In addition, environmental factors, such as temperature, relative humidity and droplet size, also affect their dispersion and determining the survival. Thus, in this paper, first airflow in the crowded train was analyzed by using CFD.

著者

高橋 勉 坂本 夏澄 Withun HEMSUWAN 吉武 裕美子

出版者

一般社団法人 日本機械学会

雑誌

流体工学部門講演会講演論文集 2016 (ISSN:24242896)

巻号頁・発行日

pp.0617, 2016 (Released:2017-06-19)

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A newly developed innovative wind / water turbine mechanism that is driven by longitudinal vortex is introduced. The blades of a conventional propeller type windmill with a horizontal rotation axis are replaced to the simple circular cylinders and a ring shaped plate is placed in the wake region. Once the propeller starts to rotate a certain direction, the longitudinal vortex appears stably behind the cylinder and the steady lift force is generated. It can rotate to the CW or CCW direction and the rotation direction is decided by the initial rotation direction. This new turbine is the simple structure, toughness and high torque feature. Therefore, it has a great possibility to use as a wind turbine to generate electricity even in the high speed wind without the pitch controller. It can apply for wider purposes, such as a turbine with high corrosion resistance and temperature resistance. We can also manufacture a micro-size turbine easier.