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山崎 正浩, 大池 真悟, 飯尾 昭一郎, 池田 敏彦
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セッションID: S0503-1-2
発行日: 2010/09/04
公開日: 2017/08/01
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The aim of this investigation was to develop an environmentally friendly nano-hydraulic turbine utilizing extreme low head waterfall. The relative distance between a runner and a waterfall is one of the important factors for stable supply of electricity. Flow rate always changes day by day. So, it is often necessary to determine precisely the relative position of the runner every time flow rate changes. It is necessary to keep the stable generation by changing the runner position or controlling the waterfall direction. The former is unrealistic method because of sophisticated mechanism to adjust the runner position. Accordingly, open type cross-flow runner was selected, and control method of flow direction by use of curved channel was investigated. As a result, the maximum power coefficient reaches at 74% even when the flow rate changes by 3.0 times.
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小出 瑞康, 関崎 敬広, 高橋 勉, 白樫 正高
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セッションID: S0503-1-3
発行日: 2010/09/04
公開日: 2017/08/01
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The target of this research is to develop a micro electric power generator for a low cost small river monitoring device. The power generator extracts an energy from flow of the river through the trailing vortex induced vibration (TVIV) occurred on a cruciform circular cylinder/strip-plate system. A prototype model for water flow was made and tested in high speed water tunnel. It was confirmed that TVIV occurs in water flow from 0.5 to 4 m/s. Power generation experiments were carried out in the water tunnel and the electric power was obtained in the same velocity range. The experiments show that this micro electric power generator is appropriate for a natural river of which flow velocity changes greatly. The power generator affects on TVIV as a damper. The obtained electric power was almost the same as a energy which was estimated from energy balance analysis, assuming the power generator is damper.
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鈴木 正己, 高尾 学, 永田 修一, 豊田 和隆, 瀬戸口 俊明, 荒川 忠一
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セッションID: S0503-1-4
発行日: 2010/09/04
公開日: 2017/08/01
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A floating type Backward-Bent Duct Buoy (BBDB) is a wave energy conversion device with an Oscillating Water Column (OWC) at the front side. The device captures the wave energy using the heaving, the pitching, the surging motion of BBDB and the heaving motion of OWC, and generates the oscillating air flow to drive the turbine-generator. The system introduces a special impulse turbine which can rotate unidirectionally and the turbine has advantage for the complete self-starting. An eigenfunction expansion method is introduced for analyzing the BBDB with OWC. It is confirmed that these solutions give good agreement with several experimental results. It is shown in a design method how to make BBDB match the turbine characteristics. The BBDB size and the turbine diameter are determined by considering the cost corresponding to the smallest size under the same output
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涌井 徹也, 中澤 健, 横山 良平
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セッションID: S0503-1-5
発行日: 2010/09/04
公開日: 2017/08/01
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Small-scale stand-alone wind turbine-generator systems have many problems on maintenance because they are operated in regions with less accessibility. In our target system, a straight-wing vertical axis wind turbine with self-starting capability is mainly operated at a constant tip speed ratio, which means a maximum power coefficient. The previous studies clarified that this system possesses high power generation performance; however, the power generation performance is significantly deteriorated due to performance deterioration of wind turbine. Thus, in order to clarify the optimal load characteristic for the system with wind turbine performance deterioration, this study analyzes the influence of the load characteristic for a constant tip speed operation on the system performance through numerical simulation.
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木綿 隆弘, 中田 博精, 古路 裕子, 中口 彰人, 木村 繁男, 小松 信義
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セッションID: S0503-1-6
発行日: 2010/09/04
公開日: 2017/08/01
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Performance of a cross-flow wind turbine located above a windbreak fence and the associated velocity fields have been investigated experimentally. Effects of the clearance between the wind turbine and the fence, as well as the direction of the turbine rotation were examined.The power coefficient of the wind turbine located above the fence was found to be higher than that of the wind turbine without a fence. When the turbine was rotating clockwise, i.e. the blades on the upstream side of the turbine were moving upward, the power coefficient decreased with the increasing clearance between the turbine and the fence. In contrast, when the turbine was rotating counterclockwise, the power coefficient increased with the increasing clearance. It was found that the variation of the power of wind turbine was related to the air flow velocity in clearance region and to the rotational direction of the wind turbine. The porous board fence and the wind turbine rotating clockwise was found to be most effective in reducing the flow velocity in the wake region.
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田畑 創一朗, 小嶋 晋平, 岡 信仁, 古川 雅人
原稿種別: 本文
セッションID: S0503-2-1
発行日: 2010/09/04
公開日: 2017/08/01
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A Quasi-three-dimensional aerodynamic design method for wind turbine with brimmed diffuser has been developed. The wind turbine with brimmed diffuser has internal and external flow feature. It is important to take into account non-uniform meridional flow distributions around it. The present design method consists of two parts: an axisymmetric viscous flow calculation on the meridional plane and a two-dimensional blade element design by wind turbine blade profile data. Continuing the process between the turbine rotor design using the two-dimensional blade element design method and the evaluation of the viscous flow fields around the rotor using the axisymmetric viscous flow calculation, the blade shape matching the flow fields around the rotor is converged. It is found that the present design method is useful to the wind-lens turbine design tool.
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飯野 光政, 飯田 誠, 荒川 忠一
原稿種別: 本文
セッションID: S0503-2-2
発行日: 2010/09/04
公開日: 2017/08/01
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Small wind turbines are spreading for the purpose of independent or domestic power suppliers. However its standard of strength is still being discussed. In this paper, IEC61400-1 Ed.3 DLC (Design Load Case) 1.1 for large wind turbines is applied for a small wind turbine and estimated its applicability. DLC 1.1 requires load estimation with extrapolation for 50 year return load. Target turbine is "AIRDORPHIN GTO" and aero-elastic simulation tool FAST is used. As a result the target turbine has various load characteristic in its operation modes; normal mode and stall mode. For this reason, an extrapolation method which considers operation modes is tried and established.
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小垣 哲也, 冨岡 義弘, 松宮 [ヒカル], 加藤 榮二
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セッションID: S0503-2-3
発行日: 2010/09/04
公開日: 2017/08/01
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In this paper, the inflow wind characteristics under towing experiments of small wind turbines were evaluated, and they were compared with the wind condition models in IEC 61400-2 Ed.2 (2006). As a result, it was found that the flow inclination angle and wind speed ratio between hub position and reference position were independent of the position on the bed of truck, and it is expected that wind conditions were almost uniform over rotor swept area. Moreover, turbulence intensity of inflow is dependent on the standard deviation of wind speed in stationary state.
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上野 祥彦, 秦 裕也, 大屋 裕二, 内田 孝紀
原稿種別: 本文
セッションID: S0503-2-4
発行日: 2010/09/04
公開日: 2017/08/01
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We have developed a new wind turbine system (WLT, WindLens Turbine) that consists of a difluser shroud with a brim at the exit periphery and a wind turbine inside it. WLT has a bigger power output compared with a general same size wind turbine. This is because a low-pressure region due to a strong vortex formation draws more mass flow to the wind turbine inside the difluser shroud. To investigate the three dimensional flow pattern around the WLT, numerical simulations are conducted with STAR-CCM+ using the LES for turbulent modeling and the moving boundary technique for rotating blades. In the simulation, it is confirmed that vortex rings are shed behind the brim alternately. However, we found an interaction with counter vortices formed between the tip vortex and the inside of the WindLens. In this report, behaviors of these vortices are investigated in more detail.
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長谷川 豊, 三好 良太, 古賀 真悟, 菊山 功嗣
原稿種別: 本文
セッションID: S0503-2-5
発行日: 2010/09/04
公開日: 2017/08/01
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For the horizontal axis wind turbine (HAWT) rotors, the rotor speed and/or the blade pitch of the rotors are frequently changed during their operation to control their power outputs or to reduce fluctuating loads on the rotors and drive trains. In order to optimize these control methods for HAWT rotors, it is imperative to understand unsteady aerodynamic characteristics of the wind turbine rotors. The unsteadiness of the rotor wake flow due to the blade pitch and the rotor speed control brings about a transient response of the rotor performance with relatively long time constant, while dynamic stall phenomena due to unsteadiness of the boundary layer flow on the rotor blade cause quicker aerodynamic response than the wake induced unsteadiness. The present study examines the unsteady aerodynamic characteristics of the HAWT rotor induced by the rotor speed control, by conducting a model analysis based on acceleration potential method and an experiment using a small HAWT rotor installed in the open air.
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高橋 正旭, 斉藤 純夫, 山科 貴裕, 山口 強太郎
原稿種別: 本文
セッションID: S0503-2-6
発行日: 2010/09/04
公開日: 2017/08/01
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As wind power generation systems have been common in these days, it is required to improve the efficiency of wind turbine blades, leading to its operational stability and high efficiency. It is introduced in this paper control methods for flow separations with simple devices, by which some improvements of airfoil characteristics can be achieved. By discussing experimentally the effects of both vortex generator installed on the upper side of blade surface and cylindrical rod set in the upstream of the blade on the airfoil characteristic, there methods are effective for improvements of the airfoil performance due to suppressed stall. The aerodynamic characteristics of the device is also verified by measuring the flow velocity just after the blade and by flow visualization using tuft grid method.
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永井 暁彦, 飯田 誠, 荒川 忠一
原稿種別: 本文
セッションID: S0503-3-1
発行日: 2010/09/04
公開日: 2017/08/01
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This study aims to design low-noise wind turbine blades by assessing some methods to predict wind turbine noise. This paper focuses on aerodynamic noise and analyzes wind turbine noise by using semi-empirical methods. The study reveals the difference of sound pressure level of aerodynamic noise. BPM model using XFOIL shows reducing noise by the control of rotating speed.
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佐野 健太郎, 飯田 誠, 荒川 忠一
原稿種別: 本文
セッションID: S0503-3-2
発行日: 2010/09/04
公開日: 2017/08/01
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This paper describes the numerical simulation of the wind flow around the MEXICO wind turbine based on Navier-Stokes equation with overset grid method and large-eddy simulation (LES). This study aims to reveal flow field around wind turbine by simulation to predict wind condition of the site where wind turbines will be constructed. The result shows that we should consider more about grid construction.
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寺田 慎吾, 飯田 誠, 荒川 忠一
原稿種別: 本文
セッションID: S0503-3-3
発行日: 2010/09/04
公開日: 2017/08/01
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With the expansion of the capacity of the wind power generation, the importance of developing precise and low-cost method of calculating the flow around wind turbines is increasing to prospect wind turbine's energy generation. In this paper, BEM supported by CFD is proposed as a method of calculating the flow and is examined for realization. Finally, it was revealed that CFD can calculate the air flow around blade tips more precisely than BEM as a result of comparison between CFD calculation, BEM calculation, and experiment. And it was revealed too that the grid used in CFD calculation should be improved.
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鎌田 泰成, 前田 太佳夫, 村田 淳介, マチュ チボ, 松田 聡志
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セッションID: S0503-3-4
発行日: 2010/09/04
公開日: 2017/08/01
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The wind turbines are operated in the field. The wind has a fluctuation in both speed and direction. Specially, the wind in the mountainous area has strong fluctuation. The fluctuation in speed and direction causes the change of incidence angle to blade cross section. So, the airfoils for wind turbine blade are operated with fluctuating angle of attach. To take into account this operation, Mie university group developed the special airfoil for fluctuating wind. In this paper, the experimental result of the rotor test in wind tunnel is described.
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鎌田 泰成, 前田 太佳夫, 村田 淳介, 松田 聡志, Thibault MATHIEU, 加賀 則光
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セッションID: S0503-3-5
発行日: 2010/09/04
公開日: 2017/08/01
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Because the amount of power generation of horizontal axis wind turbines is greatly influenced by the aerodynamic efficiency of the rotor blades, it is important to clarify the three dimensional flow on the blade surface. However, details of the flow are still unclear because of the difficulty of the three dimensional measurements in rotational system. This study use a large-sized wind tunnel, a test wind turbine and a LDV (Laser Doppler Velocimeter) in order to measure the velocity distribution on the rotor blade and consider the flow-field around the rotor blade of the wind turbine.
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内田 孝紀, 大屋 裕二
原稿種別: 本文
セッションID: S0503-3-6
発行日: 2010/09/04
公開日: 2017/08/01
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In the present numerical study, we carried out the large-eddy simulation (LES) of the wake generated behind the wind turbine generator under optimal tip speed ratio. Particular emphasis was placed on the effect of inflow turbulence on the wake region generated behind the wind turbine generator. Through comparisons between three cases with and without inflow turbulence, the speed loss of about 30-40 percent existed in the wake region (1D-5D) in all the cases, where D is a diameter of a rotor.
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石松 克也, 鹿毛 一之, 奥林 豊保, 安藤 竜也
原稿種別: 本文
セッションID: S0503-4-1
発行日: 2010/09/04
公開日: 2017/08/01
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Some wind collectors for the Darricus-type wind turbine were tried numerically by 3-D LES(Large Eddy Simulation) analysis. The aim of this study is improvement of power coefficient. The main parameters of wind collector are curvature of foil and its width. Another important parameter is foil setting angle. The rotor is constructed by 3 blades (chord length are 15% of diameter). As a result of analysis, The wind collector was effective to improve maximum power coefficient. However, it was not so effective to improve starting performance.
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脇坂 英佑, 水野 明哲
原稿種別: 本文
セッションID: S0503-4-2
発行日: 2010/09/04
公開日: 2017/08/01
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The final goal of this investigation is to develop high performance Vertical Axis Wind Turbines for clean energy supply systems. In this study, the flow-field around a VAWT was analyzed by numerical simulation. As the turbulence model DES was used and sliding-mesh scheme was applied to express rotation. The result is compared with the former analysis by RANS. RANS cannot accurately reproduce separation. On the other hand, DES showed reasonable separation performance in the current results. We found that 4 time steps per mesh length were suitable to analyze the sliding scheme. After this, the performance of VAWT will be evaluated quantitatively. Then, the numerical analysis will be compared with the field experiments of VAWT.
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原 豊, 原 頌一, 林 農
原稿種別: 本文
セッションID: S0503-4-3
発行日: 2010/09/04
公開日: 2017/08/01
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Responses of a small vertical axis wind turbine (VAWT) to pulsating wind with the amplitude of 2 m/s were measured by wind tunnel experiments and were compared with the previous results obtained in the case of the amplitude of 1 m/s. The responses in both cases agreeed well with the responses that were simulated based on the torque characteristics obtained in the steady rotational conditions. A simple expression between the rotational change width and the amplitude of the pulsating wind was presented.
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水野 明哲, 杉山 武令
原稿種別: 本文
セッションID: S0503-4-4
発行日: 2010/09/04
公開日: 2017/08/01
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In the current study, we propose a set of control scheme for field test of the straight wing vertical axis wind turbine, constructed by our group. The control scheme has two modes: The first mode is the control to keep the tip speed ratio to constant value in order to obtain highest power coefficient. For the purpose, variable load to the generator was used. The second mode is the control system of the disk brake, which is activated when the wind is strong, in order to avoid destruction by over rotation. The authors have established the control system for these purposes, and now filed test can be carried out in automatic operation.
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山西 拓也, 川口 清司, 平井 僚, 渡辺 大輔
原稿種別: 本文
セッションID: S0503-4-5
発行日: 2010/09/04
公開日: 2017/08/01
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Darius type wind turbine with straight blades has many advantages of high performance, the wind direction independency, and easy productivity of the blade. Moreover, practical use in urban areas can be expected by the improvement of the performance because it is suitable for downsizing, and low cost due to simple mechanism. In this paper, the relationship between the fluid force of blade and flow field around blade was analyzed by using PIV method combined with CFD method. Moreover in order to improve the wind turbine performance, the effects of cylindrical guide mounted inside the wind turbine were examined by wind tunnel test. It was clarified that the cylindrical guide with the diameter of rc/lr=0.5 could increase the efficiency of the wind turbine because of improvement of flow around the blades.
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谷垣 三之介, 小垣 哲也, 松宮 輝, 今村 博
原稿種別: 本文
セッションID: S0503-5-1
発行日: 2010/09/04
公開日: 2017/08/01
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Wind data at 259 windy locations selected from NEDO "Wind Power Generation Field Test Program" sites were statistically analyzed in view of turbulence with regards to Normal Turbulence model (NTM) in IEC61400-1Ed.3. It was shown that present NTM does not appropriately represent wind climate of these sites. Among others, deviation in the scatter of turbulence (σ_σ) between NTM and observation is too significant to be disregarded. Assessment according to Sec.11.9 procedure resulted in that around 40% of the sites are not suitable for IEC standard wind turbines. As a course of measure to remedy the situation a new NTM model that would better represent the observation is presented.
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村田 淳介, 鎌田 泰成, 前田 太佳夫, 西田 将志
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セッションID: S0503-5-2
発行日: 2010/09/04
公開日: 2017/08/01
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When wind turbines are installed in wind farm, the site design is important. However recently wind measurement using meteorological masts and anemometers needs a lot of cost for large wind farms and large wind turbines. Therefore, a numerical analysis is used for the wind potential prediction. Good wind condition sites in Japan concentrate in mountain region. Wind profiles are influenced by not only the topography of the site but the ground roughness, and the consideration of the ground roughness influences is necessary for accurate simulation of flow fields. In this study, a numerical analysis of flow field around 2D hill model with different terrain shape and ground roughness models is conducted. The numerical analysis employs standard k-s model, and analyzes steady-state model. The effect of terrain shape and ground roughness on the flow field is discussed and proved.
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神尾 武史, 飯田 誠, 荒川 忠一
原稿種別: 本文
セッションID: S0503-5-3
発行日: 2010/09/04
公開日: 2017/08/01
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The purpose of this study is the analysis of the turbulent wind on the complex terrain and the modeling of the fluctuating wind for the inlet condition of the numerical wind prediction. The inlet condition with the turbulent wind is significantly important for the fluctuating wind simulation, and the several methods, for example, randomness, roughness block, re-scale cyclic boundary, were designed to generate the turbulent for the inlet condition. However, a method, which is suitable for the simulation of the fluctuating wind on the complex terrain, does not appear. The approach, which is the LES calculation of the wind on a real site, would offer the much information of the wind on the complex terrain. From the temporal wind data of LES calculation, the wind profiles and the turbulences were achieved and the modeling of the inlet flow condition might be possible.
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今村 博, 小垣 哲也, 谷垣 三之介, 松宮 [ヒカル], 福田 寿
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セッションID: S0503-5-4
発行日: 2010/09/04
公開日: 2017/08/01
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This paper shows results of aero-elastic on wind turbine fatigue load to clarify the effects of turbulence characteristics in complex terrain. The effects of turbulence intensity, longitudinal, lateral and normal component of turbulence standard deviation of wind speed fluctuations on the blade bending moment are compared. The results showed that the correction model of turbulence intensity for complex terrain described in the IEC 61400-1 is very conservative for normal operation mode.
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杉本 大輔, 鈴木 博貴, 酒井 康彦, 長田 孝二
原稿種別: 本文
セッションID: S0502-1-1
発行日: 2010/09/04
公開日: 2017/08/01
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Spatial structures of a turbulent plane jet are investigated by the direct numerical simulation (DNS) based on the finite difference method. Reynolds number is 1500. Special care has been paid to the boundary condition to reproduce proper entrainments. In this study, we focused on the pressure fluctuations, velocity gradient tensors, and rate-of-rotation tensors in the transition region of the jet, which are difficult to measure.
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安原 大樹, 酒井 康彦, 久保 貴, 長田 孝二, 寺島 修
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セッションID: S0502-1-2
発行日: 2010/09/04
公開日: 2017/08/01
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A two-dimensional turbulent jet diffusion in liquid-phase has been investigated experimentally in order to clarify an effect of turbulent mixing on chemical reactions. The chemical reaction used in this study is the second-order reaction (A+B→R). The equilibrium limits of concentrations of all the species (A, B, and R) have been estimated from the results on nonreactive diffusion field by using the conserved scalar theory. We will try to measure the concentration of all the species (A, B and R) and the velocity simultaneously by using the combined probe of optical fiber probe and hot-film probe to investigate the conditional statistics by the CMC theory.
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社河内 敏彦, 津田 真彰, 鬼頭 みずき, 辻本 公一, 安藤 俊剛
原稿種別: 本文
セッションID: S0502-1-3
発行日: 2010/09/04
公開日: 2017/08/01
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中島 大, 松原 庸充, 飯尾 昭一郎, 羽田 喜昭, 池田 敏彦
原稿種別: 本文
セッションID: S0502-1-4
発行日: 2010/09/04
公開日: 2017/08/01
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Active control of a rectangular jet has been attempted to manipulate the vortex shedding interval in the major shear layer. It is considered essential that the vortex distribution along the each major shear layers plays an important role to characterize a rectangular jet behavior. In the present investigation, it was remarkably observed that the jet spreads more widely in the minor direction and contracts more greatly in major direction by the asymmetric excitation than that of the non-excited jet. Hot wire measurement was conducted, and could provide the mean, coherent and random velocity components from the instantaneous velocity signal. The measurement results showed that the coherent vortices are generated in synchronization with the excitation frequency and the pattern. In addition, it was revealed that the inclined vortex rings are formed and interacted with each other only when the jet was excited by asymmetric mode. The jet spreading is attributed to the tilting alignment of the vortex ring, and the jet contracting in minor direction is due to the self-induced deformation of the rectangular vortex ring.
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杉渕 和平, 飯尾 昭一郎, 羽田 喜昭, 池田 敏彦
原稿種別: 本文
セッションID: S0502-1-5
発行日: 2010/09/04
公開日: 2017/08/01
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This study focused on the development in space and time of vortex structures evolution in low aspect-ratio rectangular jet with pulsation. Pulsed rectangular jet was visualized using scanning-LIF (Laser Induced Fluorescence) method to clarify the vortex nature in the near field of the jet. Pulsation means large-amplitude, low-frequency excitation. It was deemed appropriate to investigate whether jet characteristics of the pulsating, submerged jet flow can be altered by including pulsations. The difference of the vortex deformation process was discussed in relation to pulsating conditions. Consequently, the pulsation leads to the formation of vortices at regular intervals. These vortices are larger than those occurring in a steady jet. The results show that the interaction between leading vortex and trailing vortex.
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木綿 隆弘, 臼沢 太一, 小松 信義, Peter OSHIKAI
原稿種別: 本文
セッションID: S0502-1-6
発行日: 2010/09/04
公開日: 2017/08/01
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The flow structures in a coaxial jet with axisymmetric and helical instability modes for a comparatively low Reynolds number were investigated. Three-dimensional numerical simulation of a coaxial jet was performed using the commercial CFD software FLUENT6.3. The numerical simulation obtained vortex shedding frequencies were in good agreement with the results of the experiment. It was confirmed that the helical vortex was shed for the range of velocity ratios from 0.5 to 1.0. For the coaxial jet with helical instability, it was found that the axial velocity along the centerline of the jet decreased more than that of the coaxial jet with axisymmetric instability, and the amplitude of the axial velocity fluctuation was small near the nozzle exit. Consequently, the increased velocity fluctuations and Reynolds stress in the mixing region were associated with the arrangement of the vortex street in the shear layer.
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岩渕 健二, 居合 徹, 元祐 昌廣, 本阿弥 眞冶
原稿種別: 本文
セッションID: S0502-2-1
発行日: 2010/09/04
公開日: 2017/08/01
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A synthetic jet is a promising technique to promote the mixing and to control flow separation because of the periodic flow disturbance. When the synthetic jet array is applied to the flow control in the fluid machinery, it is necessary to consider the optimal configuration of the jet devices. In this study, the phase-averaged three-dimensional flow structures of the two synthetic jets with in-line and parallel configurations injected in cross flow were measured by scanning stereoscopic PIV. The two jets can be actuated independently at the different injection phase and the jet spacing. The phase difference is set to ensure the coincidence of the tip location of the front and rear jets. In in-line configuration, the volume averaged vorticity of longitudinal vortex is increased by rear jet which is interacted at the position where the vortex of the front jet is fully developed. In parallel configuration with the spacing less than 12D, the momentum transport to the wall is not affected compared to wide spacing case, although the vorticity of longitudinal vortex decays by interaction with adjacent vortex.
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眞嶋 康裕, 新田 貴志, 元祐 昌廣, 本阿弥 眞冶
原稿種別: 本文
セッションID: S0502-2-2
発行日: 2010/09/04
公開日: 2017/08/01
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In this study, a synthetic jet array which can be actuated individually at the different phase from those of adjacent synthetic jets is employed. Influence of the phase difference on reattachment process in the low Reynolds number flow over a backward facing step is discussed. Flow visualization and measurement of near-wall flow using the micro flow sensor are conducted. In counter-phase injection, the excitation of separating shear layer and the transverse vortex structure are different from those in common-phase injection. It is also found from phase-averaged forward flow fraction that stable control of the reattachment process can be performed by the synthetic jets with the counter-phase injection.
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西部 光一, 藤田 祐樹, 佐藤 光太郎, 横田 和彦, 高曽 徹
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セッションID: S0502-2-3
発行日: 2010/09/04
公開日: 2017/08/01
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The flow characteristics of the plane synthetic jets were investigated by conducting experiment and numerical simulation. The time averaged flow structure between the synthetic jet and the continuous jet was compared. The flow patterns and the pressure distributions for the typical non-dimensional stroke K were showed to clarify the influence of vortex pair on the unsteady flow characteristics. Furthermore, the location of the mean flow formation was also discussed.
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山田 慎一, 高曽 徹, 松田 信吾, 山田 由人
原稿種別: 本文
セッションID: S0502-2-4
発行日: 2010/09/04
公開日: 2017/08/01
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Structures of circular synthetic jets were investigated numerically by using 3D Large-Eddy-Simulation. The instantaneous velocity vectors and vorticity contours were obtained for 3 different strokes of alternating flow in an orifice with nearly the same Reynolds numbers. The simulation results indicate that an array of vortex rings is formed near the orifice and the spacing of vortex rings increases as the stroke is increased. As the vortex travels downward from the orifice, the vortex spacing increases at first and then decreases gradually to the scale of the orifice diameter where the vortex is observed to break down. The location of the vortex collapse is shifted to downward as the stroke is increased. This change of vortex collapse allows us to explain the change in the starting point of the jet growth which was observed in previous experiments.
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田畑 隆英, 宇都 尚哉
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セッションID: S0502-2-5
発行日: 2010/09/04
公開日: 2017/08/01
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As a part of the study on the diffusion control and the direction control of the jet, the investigation of the basic characteristics of the jet flow, issuing from the pentagonal duct and the circular pipe, was carried out. The jet diffusion has been investigated using the PIV method. By using the velocity information, the half value widths of the jet and the turbulent intensities have been obtained. As a result, it has been found that there exists the difference of the flow structure between the pentagonal jet and the circular one.
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人見 孔太, 佐久間 正仁, 清水 誠二, 彭 国義
原稿種別: 本文
セッションID: S0502-2-6
発行日: 2010/09/04
公開日: 2017/08/01
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A sheathed nozzle with ventilation for abrasive suspension jets (ASJs) is proposed as a means of extending the effective standoff distance in submerged environments. Submerged cutting tests are conducted with aluminum specimens at the jetting pressure of 30 MPa and the water depth of 100 mm. The nozzle used in the cutting tests is a conical convergent nozzle followed by a straight passage, focusing section. The diameter of the nozzle and the inner diameter of the sheath are 1 mm and 3 mm, respectively. Air is sucked to the sheath via a tube with an inner diameter of 6 mm. The air flow rate is measured by a float type area flow meter attached to the end of the tube. The abrasive is garnet having a mesh designation of #100. It is showed that the sheathed ASJ nozzle with ventilation is useful for extending the effective standoff distance between the nozzle and the work-piece without a drastic reduction in the cutting capability.
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藤田 重隆, 張間 貴史, 吉武 伸晃, 大坂 英雄
原稿種別: 本文
セッションID: S0502-3-1
発行日: 2010/09/04
公開日: 2017/08/01
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The turbulent flowfield of three-dimensional turbulent free jet issuing from a two-dimensional (2-D) nozzle with multiple rectangular notches, has been investigated experimentally. The aim of this study is to manipulate a turbulent characteristic of the 2-D jet using multiple rectangular notches (Aspect Ratio=12.5) normal to the 2-D jet axis. The Reynolds number based on the nozzle width d and the nozzle exit velocity U_e was kept constant 25000, throughout this experiment. From this experiment, it was revealed that the attachment of the multiple rectangular notches to the 2-D jet restrained the increase of the turbulent energy at the jet center region on both the y and z axes in the upstream region. Furthermore, the present turbulent flowfield shows almost the same characteristics of the 2-D j et in the region x/d≧150.
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中村 元
原稿種別: 本文
セッションID: S0502-3-2
発行日: 2010/09/04
公開日: 2017/08/01
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Omnidirectional reductions in drag and fluctuating forces can be achieved for a circular cylinder subjected to cross-flow by attaching cylindrical rings along its span at an interval of several diameters. In this work, flow visualizations and PIV measurement were performed in order to explore the mechanism of the vortex shedding suppression. The mechanism is considered as follows: The corner vortices formed on the ring edges inflows to the side of the ring due to a pressure gradient. This promotes the flow turbulence on the side of the ring, and thus, the separated flow from the side of the ring reattaches on the rear of the ring at Re_d ≥ 20000. This shrinks the wake behind the ring markedly, which induces a pair of large transverse circulations behind the ring. This flow interferes the formation of two-dimensional spanwise vortices, and consequently suppresses the periodic vortex shedding.
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安田 孝宏, 里深 信行
原稿種別: 本文
セッションID: S0502-3-3
発行日: 2010/09/04
公開日: 2017/08/01
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The Entropic Lattice Boltzmann Method (ELBM) which can get stable solution by satisfying the second principle of the thermodynamic by imposing the monotonicity and the minimality of the H-function is developed recently. In the algorithm of ELBM non-linear equation must be solved to calculate relaxation adjusting parameter. However using of the iteration methods causes the increasing of computational effort for parallel computing due to the load imbalance which is occurred by the differences of iteration number on each grid point. In this study, we suggest the two kinds of approximation methods based on Taylor series expansion which do not use iteration method and compared the results with those of Newton-Raphson method for the channel flow past a square cylinder. It was found that the results using our methods is agree with those using Newton-Raphson method and can decrease the computational time even in single computation.
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近江 和生
原稿種別: 本文
セッションID: S0502-3-4
発行日: 2010/09/04
公開日: 2017/08/01
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The flow past a square cylinder with various corner curvatures has been investigated by 2-D PIV experiment. The present study is focused on the variation of the flow characteristics according to the change in the normalized curvature R/D, where R is the corner radius of the cylinder cross section and D is the side length of the square cross section. The Reynolds number is fixed at 500. Non uniform variation of flow characteristics has been observed according to the increase in the normalized curvature R/D.
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中嶋 規之, 長谷川 裕晃, 中川 健一
原稿種別: 本文
セッションID: S0502-3-5
発行日: 2010/09/04
公開日: 2017/08/01
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In recent years, considerable research efforts in a number of institutions have been devoted to advancing understanding of the unsteady effect, because the effect of unsteady fluid forces must be important to the flight mechanism. In the present study, the unsteady fluid forces and vortical flow field were measured during upward movement by changing the angle of attack impulsively. In order to better understand the relationship between unsteady fluid forces and vortex behavior, a flow visualization technique was also used to examine the flow field near the airfoil in a wind tunnel test. The unsteady fluid forces were affected by the vortex behavior on the upper surface of the airfoil during upward movements, and the vortex deforms in the spanwise direction due to the velocity induced by the airfoil movements for the discoid airfoil.
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宇佐美 達也, 伊藤 慎一郎, 大山 聖, 藤井 孝蔵
原稿種別: 本文
セッションID: S0502-3-6
発行日: 2010/09/04
公開日: 2017/08/01
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The dielectric barrier electric discharge plasma actuator is expected as a new technology which can make the design of an aerofoil etc. unnecessary. The boundary layer control might be able to be performed by induced velocity in the boundary layer as an effect of the dielectric substance barrier electrical discharge plasma actuator. Moreover, it also turns out that the control effectiveness increases by repeating ON and OFF of the applied voltage, which is called burst. But, the control mechanism is unknown. In this study, separation control on an airfoil by a plasma actuator was performed, and its control effectiveness was evaluated. The result showed a possibility to change the control effectiveness with the burst frequency mainly.
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横井 嘉文, 五十嵐 保, 宮崎 聖, 的場 敬也, 平尾 恵子
原稿種別: 本文
セッションID: S0502-4-1
発行日: 2010/09/04
公開日: 2017/08/01
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In this study, the cylinder which set grooves in the surface was designed so that it might correspond to all the direction of the wind for the purpose of cylinder drag reduction, and characteristic tests were performed using the wind tunnel experimental device. The relationship between a Strouhal number and Reynolds number was investigated in the range of mainstream velocity 2.5 m/s to 35 m/s (the range corresponding to Reynolds number is 1×10^4 to 1.2×10^5). In order to check turbulent flow transition, comparison of the wake width of a smooth cylinder and two kinds of circular cylinder with grooves was performed by Reynolds number 4×10^4. As the results of experiments, it was found that the drag reduction effect changes in the depth of a groove. It was shown that the cylinder with the deep depth of a groove is not influenced by the direction of wind. The value of a drag coefficient was about 56% of a value of the drag coefficient of a smooth cylinder. It was shown that the wake width of the proposed cylinder narrows from the wake width of the smooth cylinder.
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じゃむしどにあ はみどれざ, Yuji Tasaka, Yuichi Murai, Yasuhsi Takeda
原稿種別: 本文
セッションID: S0502-4-2
発行日: 2010/09/04
公開日: 2017/08/01
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The vertical flow structure around a standing baffle in a rectangular open channel has been investigated by an Ultrasonic Velocity Profiler (UVP). Spatial distributions of the time-averaged of vertical velocity components and relative turbulent intensities for vertical components at vertical measuring lines indicate how the flow structure changes from up- to downstream of it. At baffle's upstream they indicate the flow structure of the uprising flow. But behind the baffle indications of vortex shedding and flow separation such as the prominent peak values in the relative turbulent intensity profiles are observed. Spatio-temporal distributions of the vertical velocity at up- and downstream sections confirm the existence of periodic change of flow direction near the baffle edge at its downstream which can be attributed to the vortex shedding. Smoothed space-dependent power spectra indicate the existence of some peak structures near the baffle's edge at its downstream which are corresponding to the periodic nature of flow concentrated mainly near the baffle's edge in the spatio-temporal vertical velocity distributions. Such peak structures could not be observed for the upstream sections.
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山[ザキ] 洋武, 舟木 治郎, 平田 勝哉
原稿種別: 本文
セッションID: S0502-4-3
発行日: 2010/09/04
公開日: 2017/08/01
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The present aim is to reveal the flow past a pipe which is immersed parallel to the mainstream at high Reynolds numbers. In a wind tunnel, we carry out (1) base-pressure measurements, (2) velocity-fluctuation measurements using a hot-wire anemometer and (3) flow visualisations by a smoke-wire method with PIV analyses. The tested parameter ranges are Re = 2.0×10^3-1.3×10^4, d/t=4.0-10.0 and l/t=1.0-10.0, where Re, d, t and l are the Reynolds number, mean diameter, thickness and length of the pipe, respectively. As a result, the Re effects are negligible. The base-suction coefficient -C_<pb> monotonously decreases with increasing l/t, or with decreasing d/t. In addition, we conduct flow visualisations, and reveal the effects upon axisymmetry of wake. Finally, we classify the flow into three modes based on both periodicity and axisymmetry.
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市川 誠司, 菊地 謙次, 望月 修
原稿種別: 本文
セッションID: S0502-4-4
発行日: 2010/09/04
公開日: 2017/08/01
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We studied on a vortex ring generated by a suddenly accelerated disk to understand a relation between the circulation and necessary force to accelerate the disk. To estimate a propulsive force of small swimming animals is our motivation. We measured velocity fields using a PIV system and high speed CMOS camera around a circular disk as a model of a fin and paddle. We showed that the time derivative of the circulation related to the force to drive the disk. Thus, the disk gives energy impulsively to the vortex ring. This gives us the way to estimate thrust if we could measure the change in circulation of the starting vortex ring by the disk. We applied it to the estimation of thrust by an accelerated non-circular disk by introducing an equivalent circle that has the same area as the non-circular disk.
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服部 康男, 須藤 仁, 平口 博丸
原稿種別: 本文
セッションID: S0502-4-5
発行日: 2010/09/04
公開日: 2017/08/01
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We examined wake characteristics behind a 2-dimensioanl hill under the influence of overlying large-scale freestream disturbance. This flow field corresponds to the near-neutral atmospheric surface layer over a complex terrain. We used the active grid technique to generate the freestream disturbance, which mimics meso-scale disturbances in the planetary boundary layer. We carried out the 2-dimensional velocity measurements with a dynamic PIV system, and accumulate the turbulence statistics below the logarithmic layer height. Through the comparison of the statistics with those for experirhents without large-scale disturbances, we revealed that the fluctuating velocities are mainly generated by the local wind shear, and turbulence statistics have a similarity regardless of the addition in the disturbance.
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木村 憲二, 山口 靖之, 宮園 真悟, 小園 茂平
原稿種別: 本文
セッションID: S0502-4-6
発行日: 2010/09/04
公開日: 2017/08/01
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Aerodynamic characteristics of a scale model of a concentrator photovoltaic system built near the ground were investigated for a wide range of yaw and incidence angles. For smaller angles of incidence, aerodynamic forces are proportional to projected area in the transverse and lateral direction to the free stream. However, as the yaw angle increased, aerodynamic forces decreased slowly. Measurements revealed the effect of blockage by the ground on the aerodynamic forces and moment.
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