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Published: September 12, 2009
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Article type: Appendix
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Article type: Appendix
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Article type: Appendix
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Article type: Index
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A1-A8
Published: September 12, 2009
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Tengen MURAKAMI, Masahiro ISHIDA, Daisaku SAKAGUCHI, Hironobu UEKI
Article type: Article
Session ID: J0501-1-1
Published: September 12, 2009
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A low-solidity cascade diffuser was proposed for achieving a wide operating range as well as a high pressure ratio. However, noise increased by means of LSD due to vortex shedding from the LSD blade surface. The objectives of the present study are to show that the noise can be reduced effectively by means of a small tip-groove located at the shroud side alone without deterioration of the LSD performance, and to clarify the mechanism of high blade loading of the LSD blade with the shroud side tip-groove limited near the LSD blade leading edge. The effect of a small groove on the stagnation area, the vortex generated in the tip groove and the secondary flow behavior on the suction surface of the LSD blade and the diffuser walls as well are analyzed numerically. It is found that the formation of the recirculating secondary flow generated additionally and significantly by the shroud tip-groove is a key point of the high LSD performance.
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Takeshi Honda, Hirotoshi Sato
Article type: Article
Session ID: J0501-1-2
Published: September 12, 2009
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We computationally and experimentally investigated the effect of tip vortex on the aerodynamic performance of centrifugal blowers with shrouded impeller blades. The computational results showed that the tip vortex occurred at the leading edge of the blade, and caused loss and low velocity region in the blade passage. The distributions of the loss and the low velocity region depended on the meridian shapes of the blade around the leading edge. We confirmed the correlation between the predicted loss and low velocity region caused by the tip vortex with the measured aerodynamic performance in two blowers with different blade length along the hub.
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Takahiro NISHIOKA, Toshio KANNO, Hiroshi HAYAMI
Article type: Article
Session ID: J0501-1-3
Published: September 12, 2009
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Numerical and experimental studies were carried out to clarify the mechanism behind a modal-type stall inception in a low-speed axial-flow fan. The modal disturbance was experimentally observed in the positive slope region of the pressure-rise characteristics of two rotors. Tip-leakage vortex breakdown was not numerically confirmed in the positive slope region. A three-dimensional separation vortex, which was developed from the leading edge separation or the separation at the mid-chord on the suction surface, was confirmed. The numerical and experimental results show that the three dimensional separation vortex induced by the leading edge separation or the separation at the mid-chord influences the development of the modal disturbance.
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Jae-ho Jeong, Masato FURUKAWA, Zhiming ZHENG, Suguru NAKAGAWA
Article type: Article
Session ID: J0501-1-4
Published: September 12, 2009
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Three-dimensional structure of vortical flow fields in a half-ducted propeller fan has been investigated by numerical analysis. Complicated and unsteady flow phenomena in the fan were captured by a detached eddy simulation (DES) based on k-ω two-equation turbulence model. To elucidate the total pressure loss generation mechanism in each vortical flow phenomena, distributions of total pressure loss and absolute vorticity were investigated. Absolute vorticity is useful to separate the flow phenomena which are connected with each other, such as the wake, the tip vortex, and the corner separation. The tip vortex and the concentration of the low energy fluid between the wake and the tip vortex play major roles in the total pressure loss in a half-ducted propeller fan.
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Soichiro TABATA, Masato FURUKAWA, Masakazu ISHIKAWA
Article type: Article
Session ID: J0501-1-5
Published: September 12, 2009
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A three-dimensional aerodynamic design method for half-ducted propeller fan has been presented. The half-ducted propeller fan 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 : a three-dimensional inverse design of fan rotor blade and an axisymmetric viscous flow calculation on the meridional plane. Continuing the process between the blade design using the three-dimensional inverse 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 half-ducted propeller fan design tool.
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Ken-ichi FUNAZAKI, Hideo TANIGUTI, Hiroshi SAKAI, Atsushi CHIBA
Article type: Article
Session ID: J0501-2-1
Published: September 12, 2009
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This paper deals with the experimental study on the flow field around a low-pressure turbine linear cascade. The measurements are carried out at high and low inlet free-stream intensity (0.5% and 5%) for Re=130,000,based on the blade chord and the outlet velocity. Hot-wire probe measurements are conducted over the airfoil suction surface to understand transition process and behavior of the boundary layer. The results of the present experiment show that the size of separation bubble becomes smaller and transition point shifts more upstream as the free-stream turbulence intensity increases. At low free-stream turbulence intensity condition, K'H (Kelvin-Helmholtz) instability plays an important role in the separated boundary layer transition.
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Kazutoyo YAMADA, Ken-ichi FUNAZAKI, Mamoru KIKUCHI, Hideaki SATO
Article type: Article
Session ID: J0501-2-2
Published: September 12, 2009
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The purpose of this study is to investigate the effects of the axial gap between stator and rotor upon the performance and secondary flow field of a single axial flow turbine stage. We performed experiments for three axial gaps. In our test rig, it is possible to change the axial gap by moving the stator vane in axial direction. The tests were carried out at two different conditions, that is design and off-design conditions. The unsteady three-dimensional flow field was analyzed by time-accurate RANS (Reynolds-Averaged Navier-Stokes) simulations. The simulation results were compared with the experiments, in which total pressure loss and time-averaged flow field upstream and downstream of the rotor were obtained by five-hole probe measurements. The effect of the axial gap was confirmed in the endwall regions, and obtained relatively at the off-design condition. The turbine stage efficiency was improved almost linearly to reduce the axial gap at the off-design condition.
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Toshihiko TAKAHASHI, Ken-ichi FUNAZAKI, Bin Salleh Hamidon, Eiji SAKAI ...
Article type: Article
Session ID: J0501-2-3
Published: September 12, 2009
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The present paper presents validation results of CFD for showerhead film-cooling on the leading edge model simulating a gas turbine blade. A wind tunnel tests were conducted by using a large-scaled semi-circular model for a typical blade leading edge with circular cooling holes. The temperature distributions were measured by thermochromic liquid crystal and a comb-like thermo-probe consisting of a number of thermocouples. In regard to the CFD, Detached-Eddy Simulation (DBS) and unsteady RANS calculations by using the Spallart and Allmaras one-equation turbulence model were applied to solve convective heat transfer on the same model as the experiments. As a result, variation in the wall distribution of the adiabatic effectiveness with blowing ratio was clarified by the measurements. Spatial-averaged profiles of adiabatic effectiveness on the wall predicted by both calculations show reasonable agreement with the measurements. The DBS appears to be more valid in local distributions of the effectiveness than the URANS calculation.
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Yuichi FUSHIMI, Hoshio TSUJITA
Article type: Article
Session ID: J0501-2-4
Published: September 12, 2009
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The further improvement of gas turbines requires the development of cooling technique with reduction of cooling air mass flow rate as well as the increase of the turbine inlet temperature. The theoretically most effective air cooling method is the transpiration cooling, which will be expected to reduce the cooling air mass flow rate. In the present study, the two-dimensional flow within the turbine cascade made by the porous media was analyzed numerically by the commercial CFD code. The calculations were performed in order to examine the influence of parameters on the cooling efficiency, such as the porosity, the mean diameter of particles of the porous media and the blowing ratio. The results revealed that the cooling efficiency was strongly influenced by these parameters.
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Hiroto KATO, Yasuhiro SASAO, Satoru YAMAMOTO
Article type: Article
Session ID: J0501-2-5
Published: September 12, 2009
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Unsteady 3-D flows through two-stage stator-rotor cascade channels in the steam turbine model developed by Mitsubishi Heavy Industry (MHI) are numerically investigated. In the low pressure steam turbine cascades, vapor flows generate water droplets mainly due to homogeneous nucleation. The mass generation rate for water droplets is modeled as a sum of the mass generation rate of critical-sized nucleus and the growth rate of a water droplet based on the classical condensation theory. The total pressure, the static pressure, and the yaw angle in span-wise directions obtained by the 3-D calculations are compared with the experimental data. Also the difference between dry and wet steam flows is discussed.
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Yasuhiro SASAO, Kazuhiro Monma, Satoru YAMAMOTO
Article type: Article
Session ID: J0501-2-6
Published: September 12, 2009
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This paper presents a numerical study for unsteady flows in a high-pressure steam turbine with a partial admission stage. Compressible Navier-Stokes equations are solved by the high-order high-resolution finite-difference method based on the fourth-order compact MUSCL TVD scheme, Roe's approximate Riemann solver, and the LU-SGS scheme. The SST-model is used for evaluating the eddy-viscosity. As numerical examples, unsteady two-dimensional flows in a partial admission stage of steam turbine are calculated. The effect of the blockage to the lift of rotors is numerically investigated. The performance of several types of partial admission stage is parametrically predicted. The output ratio and the efficiency were improved by dividing the blockage regions.
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Ken-ichi FUNAZAKI, Nozomi TANAKA, Kazutoyo YAMADA, Yasuhiro CHIBA
Article type: Article
Session ID: J0501-3-1
Published: September 12, 2009
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This paper deals with experimental and numerical investigations on the interaction between inlet freestream turbulence and boundary layers with separation bubble for low-pressure turbine airfoils under Ultra-High Lift condition. Reynolds number examined is 57,000, based on chord length and averaged exit velocity. Freestream turbulence intensity is from 0.80% (no gird condition) and 2.1% (with grid condition). Hot-wire probe measurements of the boundary layer on the suction surface for the airfoils are carried out to obtain time-averaged and time-resolved characteristics of the boundary layers under the influence of the freestream turbulence. Using turbulence grid installed upstream of the cascade. Numerical analysis based on high resolution Large Eddy Simulation is also executed to enhance the understanding on the flow field around turbine airfoils. Emphasis is placed on the relationship of inherent instability of the shear layer of the separation bubble and the freesteam turbulence. Results were indicative of characteristics of the boundary layer T-S wave and KH instability as no grid condition and captured bypass transition mode as grid condition.
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Ken-ichi FUNAZAKI, Takahiro SHIBA, Nozomi TANAKA, Kazuya KIKUCHI
Article type: Article
Session ID: J0501-3-2
Published: September 12, 2009
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This paper details experimental studies on the flow field around 3 types of LPT (Low Pressure Turbine) airfoils with different peak load positions linear turbine. Highly loaded LPT blades are one of the key paths to successful future aero-engines. However, those blades are usually accompanied with separation bubble, especially at cruise condition, eventually leading to the increase in aerodynamic loss. The purpose of this study is to clarify the performance of aft-loaded LPT blade as well as front-loaded LPT blade through measurements of wake-affected boundary layers upon including separation bubble at low Reynolds number conditions. This paper focuses on differences of characteristics of the separate boundary layer influenced by the wake passing, through the comparison among the measurements for these airfoils.
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Takashi AOYAMA, Atsushi HASHIMOTO, Keiichi MURAKAMI, Paulus R. LAHUR, ...
Article type: Article
Session ID: J0501-3-3
Published: September 12, 2009
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Digital Wind Tunnel (DWT) is being developed in a project entitled Digital/Analog Hybrid Wind Tunnel in JAXA. The main objective of this project is to sophisticate the transonic wind tunnel in JAXA by applying IT technologies. We have several hurdles to establish DWT such as the developments of an automatic grid generation tool and a high performance CFD solver. In this paper, the prediction accuracy of aircraft loads by using the automatic grid generation tool and the modeling of porous wall for the CFD calculations of whole wind tunnel including an aircraft model, support instruments, and walls are discussed.
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Futoshi NAGAMINE, Hiroaki KISHIGE, Mitsuru IKEDA, Takeshi MITSUMOJI, M ...
Article type: Article
Session ID: J0501-3-4
Published: September 12, 2009
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Speed up is one of the most important issues of Shinkansen. However, aerodynamic noise of Shinkansen has been serious problem. One of the main noise sources is a pantograph installed on the roof to collect current. Sound from a panhead predominates in pantograph noise. Up to now, the shape optimization for the panhead using CFD analysis has been studied. But, the performance of a present computer is not enough. Therefore, the authors proposed shape-optimization method based on wind tunnel testing with "Deformable Wind runnel Model", which is composed of frames and a film. By some experiment, this method can be useful for shape optimization.
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Naruhiko TAN, Takayuki AOKI
Article type: Article
Session ID: J0501-3-5
Published: September 12, 2009
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In this study, level set method and conservative level set method had been implemented on rotational cylindrical coordinate system and applied to simulation of churning by a gear-shaped rotating object. As a result, it was found that conservative formulation was favorable for estimating the amount of splashed oil rather than non-conservative formulation such as level set method. Through the series of test cases, it was shown that the conservative level set method could be effective method to analyze the splashed oil by churning.
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Satoshi WATANABE, Naoki INOUE, Koichi ISHIZAKA, Akinori FURUKAWA
Article type: Article
Session ID: J0501-3-6
Published: September 12, 2009
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The attachment of inducer upstream of main impeller is an effective method to improve the suction performance of turbopump. However, various types of cavitation instabilities are known to occur even at the designed flow rate as well as in the partial flow rate region. The cavitation surge occurring at partial flow rates is known to be strongly associated with the inlet back flow. In the present study, in order to understand the detailed structure of internal flow of inducer, we firstly carried out the experimental and numerical studies of non-cavitating flow, focusing on the flow field near the inlet throat section and inside the blade passage of a two bladed inducer at a partial flow rate. The steady flow simulation with cavitation model was also made to investigate the difference of the flow field between in the cavitating and non-cavitating conditions.
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Donghyuk Kang, Koichi Yonezawa, Hironory Horiguchi, Yutaka Kawata, Yos ...
Article type: Article
Session ID: J0501-4-1
Published: September 12, 2009
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Rotating cavitation in rocket turbopump inducers was simulated by a three dimensional commercial CFD code. In order to clarify the cause of cavitation instabilities, the velocity disturbance caused by cavitation was obtained by subtracting the velocity vector under non-cavitating condition from that under cavitating condition. It was found that there exists a disturbance flow towards the trailing edge of the tip cavity. This flow has an axial flow component towards downstream which reduces the incidence angle to the next blade. It was found that all of the cavitation instabilities start to occur when this flow starts to interact with the leading edge of the next blade. The existence of the disturbance flow was validated by experiments.
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Kengo KIKUTA, Yoshiki YOSHIDA
Article type: Article
Session ID: J0501-4-2
Published: September 12, 2009
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The degree of thermodynamic effect depends on rotation speed and fluid temperature. Experiments in liquid nitrogen were conducted, in which the inducer rotational speed and the fluid temperature ware changed to estimate the influence on the thennodynamic effect. In the experiment with lower rotational speed, the cavity length was shorter, and suction perfbnnance was improved than that with higher speed. From the arrange data using the modified non-dimensional thennodynamic parameter Σ^〓_<mod>, the effect of nonlinearity of the vapor pressure curve should be considered to evaluate the thennodynamic effect especially in the case of higher temperature.
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Genki YAMAMOTO, Yuka IGA, Motohiko NOHMI, Toshiaki IKOHAGI
Article type: Article
Session ID: J0501-4-3
Published: September 12, 2009
Released on J-STAGE: August 01, 2017
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In this study, numerical simulation of turbulent cavitating flow around a two dimensional hydrofoil was performed. RANS/LES hybrid model were compared with RANS model. Dynamic switching according to flow field was used for RANS/LES hybrid model. In a non-cavitating and cavitating condition, time-averaged lift and drag coefficient obtained by both turbulence model were approximately the same magnitude. In a cavitating condition, the results obtained by both turbulence model showed periodic shedding of cloud cavitation. However, the Strouhal number obtained by RANS/LES hybrid model was smaller than that by RANS model, and was in the predicted range by an experiment.
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Takanori Ishii, Takahide Nagahara, Yasuhiro Inoue
Article type: Article
Session ID: J0501-4-4
Published: September 12, 2009
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We developed a new method for controlling specific speed at best efficiency point of axial flow pumps. This method introduced two scalar parameters for adjusting a blade surface globally, one is the total curvature of blade camber surface, and the other is blade setting angle. The total curvature represents strength of blade surface curving and controls pump head. The blade setting angle determines blade inlet attack angle and controls a flow rate characteristics. Changing both parameters at once, we control the specific speed of the pump best efficiency point. If we modify the total curvature of blade surface with keeping its curvature distribution similar, we can change specific speed without major deterioration of pump efficiency. Because the controlling method is simple and efficient, we can also reduce the duration and cost of the blade design and optimization process.
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Yasuhiro Inoue, Takahide Nagahara, Toshiyuki Sato, Satoshi Sugahara
Article type: Article
Session ID: J0501-4-5
Published: September 12, 2009
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In recent years, Particle Image Velocimetry (PIV) is being recognized as one of the effective flow measurement methods to investigate the flow field in detail. On the other hand, a performance prediction at off-design point as well as design point using computational fluid dynamics (CFD) also comes to be possible with the advance of the computer technology. In this report, the internal flow field in a mixed-flow pump at the performance instability point was investigated using PIV and comparing with the CFD result. As a result, the recirculation flow that reached to the trailing edge around the suction side of impeller blades was observed.
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Yoshikado HOTTA, Ryota FUJIWARA, Yasuyuki NISHI, Junichiro FUKUTOMI, T ...
Article type: Article
Session ID: J0501-4-6
Published: September 12, 2009
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Single-blade centrifugal pump is used as a sewage pump widely. However, single-blade centrifugal pump impeller is acted on a big radial thrust because the shape of the impeller is an asymmetry geometrically. Therefore it is necessary to grasp a radial thrust quantitatively when the reliability of the pump is improved. This study investigated the behavior of the radial thrust to act on single-blade centrifuging impeller by an experiment and CFD analysis. Furthermore, the radial thrust was divided by applying unsteady conservation of momentum to single-blade centrifugal impeller, and it was investigated.
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Katsunori ONISHI, Maki MORITA, Madoka NAKAJIMA, Toichi FUKASAWA
Article type: Article
Session ID: J0501-5-1
Published: September 12, 2009
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Authors have developed a new type pressure sensor using an optical fiber with Fiber Bragg Grating (FBG), which enable to measure pressure only by sticking the sensor on a body surface. It was reported that the developed FBG pressure sensor could well measure pressures on a body surface in steady flow. In this paper, response of a developed FBG sensor to fluctuating pressure produced by an audio speaker and that on a cylinder surface in waves were studied
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Toshihiro Morioka, Shin-ichi Nakao, Masaki Takamoto
Article type: Article
Session ID: J0501-5-2
Published: September 12, 2009
Released on J-STAGE: August 01, 2017
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A new PVTt system has been developed to establish the national standard for a gas flowrate of less than 5 mg/min. It, is presented in this paper that a mass of gas gathered in the constant volume tank is the most important parameter on an uncertainty analysis of a PVTt system and the uncertainty of a flowrate must be described with the collection time. This PVTt system can calibrate a flow meter with a desired uncertainty for the flowrate range less than 5 mg/min, because it is possible to calibrate a test flow meter over several days without disturbances of the upstream condition.
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Katsuhisa OHBA, Yuki TOYAMA
Article type: Article
Session ID: J0501-5-3
Published: September 12, 2009
Released on J-STAGE: August 01, 2017
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In this study, the compensator for the cold-wire thermometer was digitized by employing a FPGA (Field Programmable Gate Array) device. The cold-wire thermometer involved the frequency response of a first-order lag in a high-frequency range (100Hz〜) and a low-frequency range (0.01〜10Hz) due to the thermal time constants related to the cold-wire and its prongs, respectively. The bilinear transformation was utilized to design a digital filter with the first-order lead characteristic. As the characteristic roots of the thermometer depend on temperature and velocity fields, the temperature signals were compensated through updating the filter coefficients based on the instantaneous temperature and velocity fluctuations. Consequently, the present method made it possible to realize the high-accuracy temperature measurements by using the cold-wire thermometer in unsteady flows. It was verified that the temperature signals at the low frequency were appropriately compensated with an uncertainty of less than 5.5%.
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Shigeru MURATA, Risa HIRAO, Yohsuke TANAKA
Article type: Article
Session ID: J0501-5-4
Published: September 12, 2009
Released on J-STAGE: August 01, 2017
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This paper presents an optical technique for fibrous object measurement in 3D space based on digital holography. The technique consists of two steps : one is object identification using clustering based on self-organization algorithm and the other is shape evaluation using curvature and torsion as evaluation indexes. On identification, candidate points of fibrous objects are clustered to each fiber. Then constitution point sequences are made from the clustered points to evaluate curvature and torsion quantitatively representing object shape. The performance of the present technique is checked by numerical simulation. It is found from the numerical simulation results that curvature and torsion obtained in shape evaluation are in good agreement with the true values.
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Satoshi NAKAZAKI, Kouju SHIOZAKI, Hiroyuki HIRAHARA
Article type: Article
Session ID: J0501-5-6
Published: September 12, 2009
Released on J-STAGE: August 01, 2017
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When a gas-filled closed column is driven at the resonant frequency of the column, finite amplitude standing wave is induced. Acoustic compressor is a device which is based on this standing wave under the region of the finite amplitude wave. In this paper, axial symmetric convergent tubes are used. It was confirmed that a shock wave appeared in a cylindrical resonator and thereby the amplitude of the standing wave has a cut off value. This phenomena is called acoustic saturation, and the cylindrical resonator could not use for an acoustic compressor. In this paper, the large amplitude pressure fluctuation is measured by use of the exponential converging resonator and the resonant type driver which have a mechanical resonant frequency near that of the gas-column. The experimental research was conducted and its compression ratio was compared with numerical simulation.
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Kodai HANYU, Keisuke MATSUDA, Takayuki SAITO
Article type: Article
Session ID: J0502-1-1
Published: September 12, 2009
Released on J-STAGE: August 01, 2017
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Optical fiber probing is one of the efficient and reliable measurement methods for gas-liquid two-phase flows. We demonstrate the simultaneous measurement of velocities and diameters of bubbles and droplets using S-TOP and report its excellent performance. In order to realize more high-accuracy measurement, we need to consider a contact position of S-TOP at a bubble surface. In this research, we focus pre-signal which appears when S-TOP contacts with the center region of a bubble, and discuss the relationship between the output voltage of pre-signal and the contact position of S-TOP at a bubble surface. Appling this property cleverly, one can discriminate a contact position.
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Kenjo YOSHIMOTO, Manabu YAMAMOTO, Daiji SONE, Takayuki SAITO
Article type: Article
Session ID: J0502-1-2
Published: September 12, 2009
Released on J-STAGE: August 01, 2017
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The liquid phase around a zigzagging ascent bubble move three-dimensionally. In this study, Stereoscopic particle image velocimetry (PIV) was applied to measurement of liquid motion around a zigzagging ascent bubble. In this method, a zigzagging bubble was captured by high-speed video cameras from two directions. The two cameras satisfied the scheimpflug condition. To minimize the effect of reflection of YAG laser from the surface of a bubble, Sharp Cut Filters was set in front of each camera. As a result, instantaneous three component velocity fields were obtained. From these results, we compared the results of stereoscopic PIV with the visualization of mass transfer of CO_2 from bubble surface via LIF with HPTS.
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Masaaki ISHIKAWA, Kunio IRABU, Isao TERUYA, Munehiro NITTA
Article type: Article
Session ID: J0502-1-3
Published: September 12, 2009
Released on J-STAGE: August 01, 2017
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This paper described a bubble jet flow. Bubbles and seeding particle are simultaneously visualized by the single high-speed camera. The obtained images are separated to bubble and particle images by image processing. These liquid phase velocities are calculated by PIV and PTV, and we calculate the instantaneous velocity and mean velocity in order to compare single phase flow with bubble jet flow.
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Yuichi MURAI, Koji Yoshida, Yuji TASAKA, Yasushi TAKEDA
Article type: Article
Session ID: J0502-1-4
Published: September 12, 2009
Released on J-STAGE: August 01, 2017
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Vortex patterns in Taylor-Couette flow are uniquely determined with Reynolds number in single-phase medium. It never contains hysteresis in any transition from one to another for sufficiently large aspect ratio. In contrast, inclusion of bubbles provides a remarkable hysteresis in wavy vortex regime, snowing a periodic switching between spiral and toroidal modes. From this fact, space-time four-dimensional mechanism on bubble-vortex interaction is to be deduced from a number of physical aspects. Moreover, the interaction is tightly relevant to frictional drag reduction that occurs at high gain factor up to 10. We report on the interpretation on this phenomenon in this paper.
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Noriaki KAMIOKA, Tatsuya KAWAGUCHI, Isao SATOH, Takushi SAITO
Article type: Article
Session ID: J0502-1-5
Published: September 12, 2009
Released on J-STAGE: August 01, 2017
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In this paper we applied interferometric laser imaging technique to the measurement of ζ potential and diameter of bubbles in liquid. The experimental results showed that various methods for producing microbubbles did not make difference in the values of ζ potential. Helium and air were used as gas components of bubbles and it resulted no difference in the values. In order to understand the mechanism of charging characteristic of microbubbles, we changed the pH of the deionized water and added alcohols to the deionized water. The results showed that the absolute value of the ζ potential increased when the pH increased and higher molecular weight alcohol easily decreased the absolute value of ζ potential.
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Takehiko KUMAGAI, Manabu IGUCHI
Article type: Article
Session ID: J0502-2-2
Published: September 12, 2009
Released on J-STAGE: August 01, 2017
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Relationship between the channel height and flow pattern of gas-liquid tow-phase flow in a millimeter-scale rectangular channel has been investigated experimentally. Particular attention is paid to the effect of the channel height on the flow pattern through a sudden expansion. The height is reduced from 2mm to 0.5mm. Some interesting flow patterns are observed with a decrease in the height of the channel. For example, the re-circulating flow commonly observed downstream of the sudden expansion in the conventional scale channel disappears at a height of 0.5mm.
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Toshihiro KAWAGUCHI, Kenichiro HAGIHARA, Hirotaka YADA, Takuya TSUJI, ...
Article type: Article
Session ID: J0502-2-3
Published: September 12, 2009
Released on J-STAGE: August 01, 2017
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It is difficult to apply optical techniques to the velocity measurement of the fluid-particle flows, especially when the volume fraction of the particle becomes high. In the present paper, the NMR (Nuclear Magnetic Resonance) measurement is applied to dense liquid-solid flows. The velocity distribution of the liquid-solid flow is measured non-invasively by the phase method. It is verified that the velocity distribution of the laminar and the turbulent flow for the single phase flow agrees with the theoretical solution or the empirical correlation. The velocity distribution of the turbulent liquid-solid flow is successfully measured and compared with the wall law.
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Yuto ITO, Masahiro TAKEI
Article type: Article
Session ID: J0502-2-5
Published: September 12, 2009
Released on J-STAGE: August 01, 2017
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An electrical CT, calculate the particle concentration distribution in a pipe by measuring the resistance. However, the resistance is measured in a series circuit in a simple model. Therefore, an equivalent circuit should be considered by analyzing the measured resistance value using the sweeping impedance method. These experiment conditions are three cases which the pipe inside was filled only with water, filled only with the particle, and half filled with the particle. The experimented three cases are analyzed, and compared respectively.
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Takao MAEDA, Yasunari KAMADA, Takayuki KAMEI, Masayoshi OKAMOTO, Masas ...
Article type: Article
Session ID: J0503-1-1
Published: September 12, 2009
Released on J-STAGE: August 01, 2017
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For wind turbines, the site selection is important to utilize wind energy, because it depends strongly on wind speed. Wind assessment needs long term observation and high cost, especially for large wind turbines. Then, numerical analysis is often used for the site selection. However, the accuracy is not enough for complex terrains that are more common in Japan. The objective of this study is to improve the numerical analysis of winds on complex terrains by investigation of effects of surface roughness and steepness. This paper describes the experimental results of wind tunnel measurements of wind field on two-dimensional hill models which have various surface roughness and steepness with PIV system.
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Sannosuke Tanigaki
Article type: Article
Session ID: J0503-1-2
Published: September 12, 2009
Released on J-STAGE: August 01, 2017
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Wind data at 290 points widely distributed in domestic potential wind farm sites were assessed in view of turbulence with regards to Turbulence model (NTM) in IEC91400-1Ed.3. While observed mean 15m/s turbulence intensity exceeded NTM cat.A value(=0.16) only at 20% of the investigated sites, observed 90% quantile exceeded NTM cat.A representative value at 48% of the sites. This discrepancy in the NTM coverage between mean and 90% quantile mainly comes from the fact that estimation of variance of σ in NTM is far below observation. Some idea of modification to NTM model to adequately describe the observation is presented.
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Takanori UCHIDA, Yuji OHYA
Article type: Article
Session ID: J0503-1-3
Published: September 12, 2009
Released on J-STAGE: August 01, 2017
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It is highly important in Japan to choose a good site for wind turbines, because the spatial distribution of wind speed is quite complicated over steep complex terrain. We are developing the unsteady numerical model called the RIAM-COMPACT^<[○!R]> (Research Institute for Applied Mechanics, Kyushu University, Computational Prediction of Airflow over Complex Terrain). The RIAM-COMPACT^<[○!R]> is based on the LES (Large-Eddy Simulation) which is a kind of a turbulence model. The object domain of the RIAM-COMPACT^<[○!R]> is from several m to several km, and can predict the airflow and gas diffusion over complex terrain with high precision. In the present paper, an influence of elevation data on topography-induced turbulence of wind turbine neighborhood was examined.
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Yasuo HATTORI, Hiromaru HIRAKUCHI, Soichiro SUGIMOTO, Shuji ISHIHARA, ...
Article type: Article
Session ID: J0503-1-4
Published: September 12, 2009
Released on J-STAGE: August 01, 2017
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Turbulence simulations in the neutral atmospheric surface layer with a numerical weather prediction model WRF have been performed under an ideal condition; the terrain was flat and the surface roughness was homogeneous. When the vertical turbulence diffusion coefficient was estimated by using a large-eddy simulation (LES) with a high-resolution grid (the horizontal-grid spacing was 100m), the predicted turbulence intensity of grid-scale velocity fluctuations agreed well with that of observations. On the other hand, the magnitude of grid-scale velocity fluctuations with a PEL scheme, which is usually used in weather forecasting, remained a small value even with the high-resolution grid. This is caused by a difference of prediction capability for turbulence structure in the surface layer, i.e., only a LES can capture coherence structures near the surface.
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Shinji KADOKURA, Atsushi HASHIMOTO, Yasuo HATTORI, Soichiro SUGIMOTO, ...
Article type: Article
Session ID: J0503-1-5
Published: September 12, 2009
Released on J-STAGE: August 01, 2017
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By combined use of a meso-scale meteorological prediction system, a Computational Fluid Dynamics (CFD) model and a statistical model, which are developed by CRIEPI, in addition to a wind turbine wake-model and a prediction model for operational status of wind-turbine, a prediction model for wind power generation of a wind farm have been constructed. Evaluating the uncertainty step-by-step in the model, it is shown that the performance of predictability is improved at each step of the model ; the meteorological prediction system show the possibility of rapid variations, the CFD model separates difference between wind-turbines, and the statistical model improve the bias and error. This analysis, furthermore, makes it clear that the error statistics is affected by the prediction of operational status based on observational data from a wind farm. The model is validated by the prediction simulation for 5 wind farms, where the wind fields have different properties, 3 sites in Tohoku Area, 1 site each in Kanto Area and Kyushu Area. The prediction error is less than 20% as for the next day prediction, where the lead-time is between 18 and 42 hours. The improvement rate defined by comparison with the continuous model, which predicts continuously the same value of the wind power generation as that at the prediction time, is greater than 30%.
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Kazuhiro Murata, Tomohiro FUKUI, Koji MORINISHI
Article type: Article
Session ID: J0503-2-1
Published: September 12, 2009
Released on J-STAGE: August 01, 2017
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When designing fluid machines such as a windmill, it is important to consider flow pattern by computational simulation. In this paper, the numerical simulation of flow around a windmill-rotor is presented. The artificial compressibility method is used for solving the incompressible Navier-Stokes equations. The scheme used for convection term is the Roe's flux-difference splitting solver. For pseudo time, the LU-SGS method is used. These methods enable us to solve two dimensional incompressible Navier-Stokes equations. For the technique to analyze flow pattern around windmill, the overset grid is used. As a result, the pressure distribution and velocity vectors around the windmill are obtained quantitatively.
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Mikio SHIMIZU, Go SAKAGUCHI, Jyun-ichi SATO
Article type: Article
Session ID: J0503-2-2
Published: September 12, 2009
Released on J-STAGE: August 01, 2017
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According as introduction of wind power generation growth, the necessity of detail structural analyses of wind turbines is increasing in recent years. In addition, there are various wind turbine design codes that can be used to estimate wind turbine behavior. However, the number of degrees of freedom that can be modeled by many of the design codes is limited in order to execute efficient calculation. In this study, we developed an original code for wind turbine dynamic response simulations. The code is based on the finite element method which adopts a direct integration method and it can take geometrical nonlinearity including finite rotation into account for modeling turbine rotation. In this paper, an outline of developed code functions is shown and wind turbine behaviors are analyzed to verify the functions. The results calculated by the developed code are in fairly good agreements with the results obtained in terms of an existing design code FAST.
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Eisuke WAKISAKA, Akisato MIZUNO
Article type: Article
Session ID: J0503-2-3
Published: September 12, 2009
Released on J-STAGE: August 01, 2017
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We quantitatively evaluate the airfoil performance using numerical analysis on the flow around the airfoil to improve the startup characteristics and the maximum output of straight wing vertical axis wind turbines. To do this We need a numerical method that can accurately evaluate the performance of airfoil. In this study, using a single airfoil of NACA0018, We compared analyzed results and experimental results on the phenomenon that detachment arises prominently at near the stall angle. Therefore we used three turbulence models LES, DES-SA and DES-SST in our analysis. As a result, over the stall angle (α=14°), Cl and Cd did not match the experimental value. But we figured out that the DES-SST model decreased Cl and was able to analyze the stall phenomenon.
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Toru ARAYA, Makoto IIDA, Chuichi ARAKAWA
Article type: Article
Session ID: J0503-2-4
Published: September 12, 2009
Released on J-STAGE: August 01, 2017
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Recently, attention is focused on the wind turbine breakdown mechanism, the analytic tool covering the motion in detail is needed. The aim of this study is to establish and modify some of the analytic tool about the wind turbine structure. Specifically, FAST and Simulation X are combined to use them for the analysis technique. FAST is an aeroelastic code for horizontal axis wind turbines and supplied by NREL. Simulation X is a multidomain physical modeling software and supplied by ITI. One of the purposes of this study is to develop the analytic tool using monitoring and comparative verification. In the present paper, modeling of several elements in Simulation X is verified in the first stage.
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