Language：English   Publishing type：Research paper (scientific journal)   Publisher：Iron and Steel Institute of Japan  

The electromagnetic stirring (EMS) is a method to stir molten metal using in the steel making like the continuous casting. Physics concerning the EMS includes electromagnetic and fluid dynamics with free surface, which is magneto hydrodynamics. Theoretical analysis of magneto hydrodynamics is limited and/ or very difficult, so that the numerical computation is required to analyze magneto hydrodynamic phenomena. It means that Maxwell’s equations and Navier-Stokes equations must be solved simultaneously, and a lot of calculation time is expected. In this study, “based plane shadow method”, which is similar to the previous “R shadow method” but different from it in ability to be applied to any shape of the free surface, is suggested. Validity of the “based plane shadow method” is demonstrated by solving a magneto hydrodynamic problem simulating the continuous casting. It is shown that a comparable accuracy with solution obtained to solve the governing equations directly and a large amount of reduction in computational time achieve.

DOI： 10.2355/isijinternational.ISIJINT-2017-564

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Wiley-Liss Inc.  

This paper deals with a transfer method for a thin plate by levitating with multiphase air flow. Noncontact transfer methods are required for glass plates and semiconductor wafers in order to keep them clean. In the proposed method, a thin plate was slightly levitated with a small inclination by blowing and sucking air from orifice restrictors, and airflow was blown against the lower side of the plate so that the driving force was generated. The plate was continuously carried by shifting the air flow pattern in accordance with the plate position. Forty-eight air flow slots were arranged with intervals of 15 mm. The velocity of a plate with dimensions of 90 mm × 100 mm × 2 mm and a weight of 139 g was almost linearly increased at an acceleration of 15 mm/s2 and reached 50 mm/s after driving for 3 s. The levitated height was 0.13 and 0.28 mm at the lower and higher sides at air pressures of the positive and negative restrictors of +7.0 and less than −3.0 kPa, respectively. In the case of an initial velocity of 60 mm/s, the plate was turned in reverse after moving for 100 mm. The plate can move reciprocally by reversing the air flow pattern.

DOI： 10.1002/ecj.12044

Authorship：Last author   Publishing type：Research paper (scientific journal)   Publisher：電気学会  

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical Engineers of Japan  

This paper deals with a transfer method for a thin plate by levitating with multiphase air flow. Non-contact transfer methods are required for glass plates and semiconductor wafers in order to keep them clean. In the proposed method, a thin plate was slightly levitated with a small inclination by blowing and sucking air from orifice restrictors, and airflow was blown against the lower side of the plate so that the driving force was generated. The plate was continuously carried by shifting the air flow pattern in accordance with the plate position. 48 air flow slots were arranged with intervals of 15 mm. The velocity of a plate with dimensions of 90 mm × 100 mm × 2 mm and a weight of 139 g was almost linearly increased at an acceleration of 15 mm/s2 and reached 50 mm/s after driving for 3 s. The levitated height was 0.13 and 0.28 mm at the lower and higher sides at air pressures of the positive and negative restrictors of +7.0 and less than -3.0 kPa, respectively. In the case of an initial velocity of 60 mm/s, the plate was turned in reverse after moving for 100 mm. The plate can move reciprocally by reversing the air flow pattern.

DOI： 10.1541/ieejeiss.137.1145

Authorship：Lead author   Publishing type：Research paper (scientific journal)   Publisher：日本機械学会  

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：一般社団法人 日本機械学会  

Flow fields with coherent turbulent structures behind a backward-facing step have been investigated with Laser Doppler Velocimetry to clarify a mechanism of flow control with synthetic jets. Synthetic jets with a frequency which is observed in the velocity fluctuation of the backward-facing step flow without the jet have been fed perpendicularly to the main flow from the vicinity of the step edge. Periodic component of velocity fluctuation with the same frequency of the jet is extracted with procedure of phase locked averaging. Vortices shed from the step edge have an organized structure which is synchronized with the jet and these vortices are advected immediately above the separated stream line at a speed of around 45% of the free stream velocity. Amplitude of non-periodic velocity fluctuation are larger than those of periodic fluctuations due to the vortices. The kinetic energy of the non-periodic velocity fluctuations comes from the main flow and the periodic velocity fluctuations are just the beginning of such taking in. The reattachment position closely correlates with total kinetic energy of the periodic and non-periodic velocity fluctuations. This implies the flow reattachment is promoted by the mixing of the fluids in the main stream and the reversed flow region. © 2011 The Japan Society of Mechanical Engineers.

DOI： 10.1299/kikaib.77.2422

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：一般社団法人 日本機械学会  

Backward-facing step flows with horizontal or vertical synthetic jets fed from the vicinity of the step edge have been investigated to clarify effects of the synthetic jets on separated-reattachment flows as well as to obtain new knowledge for the active control of the flows. Relations between reattachment length and flow control parameters, such as frequencies and velocities of the jet, have been studied. Then details of the flow fields have been obtained with time-mean as well as phase-locked average procedures. Changes in the reattachment length for constant non-dimensional jet velocity are mostly determined from a ratio of the jet frequency to natural frequency of velocity fluctuation without a jet. The reattachment length becomes a minimum when the jet frequency ratio is around unity and decreases in proportion to the non-dimensional jet velocity to the power of -0.11〜-0.13. The feed of the synthetic jet makes shear layers in the downstream of the step edge be periodical organized vortices which induce organized periodic velocity fluctuation and causes non-organized random fluctuations with lower frequencies. These velocity fluctuations stimulate mixing of the fluids in the main stream and in the reverse flow region to promote the flow reattachment.

DOI： 10.1299/kikaib.75.749_19

Authorship：Lead author   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：一般社団法人日本機械学会  

Three-dimensional measurements of cross-correlation coefficient of velocity fluctuations are carried out to investigate flow behaviors of two-dimensional separated flows over a flat plate under an adverse pressure gradient. The velocity fluctuations are obtained with two I-type hotwire probes, one of which is fixed near the flat plate and the other traverses the flow region. The results show that regions with positive and negative cross-correlation distribute checkerwise in a vertical section parallel to the main flow and three-dimensionality of the region with positive correlation near the flat plate grows as the region flows down, whereas spanwise two-dimensionality of the negative region above it holds. In addition, time sequences of the correlation distributions tell that advection velocities of the separated flow structures are about 0.3 times as large as the inflow velocity. Simulations with simplified potential vortices are also made to specify the three-dimentional flow structure of the separation. They illustrate that alternate rows of arch-shaped vortices formed immediately downstream of the separation can reproduce well the characteristics of the experimental results.

DOI： 10.1299/kikaib.73.2242

Publishing type：Research paper (scientific journal)  

Three-dimensional measurements of cross-correlation coefficient of velocity fluctuations are carried out to investigate flow behaviors of two-dimensional separated flows over a flat plate under an adverse pressure gradient. The velocity fluctuations are obtained with two I-type hotwire probes, one of which is fixed near the flat plate and the other traverses the flow region. The results show that regions with positive and negative cross-correlation distribute checkerwise in a vertical section parallel to the main flow and three-dimensionality of the region with positive correlation near the flat plate grows as the region flows down, whereas spanwise two-dimensionality of the negative region above it holds. In addition, time sequences of the correlation distributions tell that advection velocities of the separated flow structures are about 0.3 times as large as the inflow velocity. Simulations with simplified potential vortices are also made to specify the three-dimentional flow structure of the separation. They illustrate that alternate rows of arch-shaped vortices formed immediately downstream of the separation can reproduce well the characteristics of the experimental results.

DOI： 10.1299/kikaib.73.2242

Authorship：Lead author   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：一般社団法人日本機械学会  

Flow visualization with surface tufts is carried out to investigate the flow behaviors in two dimensional separated flows over a flat plate. The separation is realized in the channels with diverging cross sectional areas, which are designed to generate constant adversed pressure gradients with quasi one dimensional flow assumption. Distributions of the local flow direction on the flat plate are determined from the photographs of the flow visualization with surface tufts. The flow angles are presented with complex numbers to enable ones to treat them in various manners. Complex correlation factor is introduced to evaluate the three dimensional behaviors of separated flows. The results show the flows immediately downstream of the separation exhibit periodic correlative regions in the spanwise direction as well as in the downstream direction, and their scales are independent of the flow velocity and the magnitude of pressure gradients.

DOI： 10.1299/kikaib.72.649

Publishing type：Research paper (scientific journal)  

Flow visualization with surface tufts is carried out to investigate the flow behaviors in two dimensional separated flows over a flat plate. The separation is realized in the channels with diverging cross sectional areas, which are designed to generate constant adversed pressure gradients with quasi one dimensional flow assumption. Distributions of the local flow direction on the flat plate are determined from the photographs of the flow visualization with surface tufts. The flow angles are presented with complex numbers to enable ones to treat them in various manners. Complex correlation factor is introduced to evaluate the three dimensional behaviors of separated flows. The results show the flows immediately downstream of the separation exhibit periodic correlative regions in the spanwise direction as well as in the downstream direction, and their scales are independent of the flow velocity and the magnitude of pressure gradients.

DOI： 10.1299/kikaib.72.649

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：一般社団法人 日本機械学会  

Flow visualization with surface tufts is carried out to investigate the flow behaviors in two dimensional separated flows over a flat plate. The separation is realized in the channels with diverging cross sectional areas, which are designed to generate constant adversed pressure gradients with quasi one dimensional flow assumption. Distributions of the local flow direction on the flat plate are determined from the photographs of the flow visualization with surface tufts. The flow angles are presented with complex numbers to enable ones to treat them in various manners. Complex correlation factor is introduced to evaluate the three dimensional behaviors of separated flows. The results show the flows immediately downstream of the separation exhibit periodic correlative regions in the spanwise direction as well as in the downstream direction, and their scales are independent of the flow velocity and the magnitude of pressure gradients.

DOI： 10.1299/kikaib.72.649

Authorship：Lead author   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Mechanical Engineers  

Flows around circular cylinders under streamwise pressure gradients were studied experimentally. Pressure distributions on the cylinder surface, frequencies of shedding vortices and wake velocity distributions were obtained under the various pressure gradients. The fundamental characteristics of flows around the circular cylinders, such as pressure distributions on the cylinders, angles of separation, pressure drags as well as velocity profiles and turbulence in the wake flows, exhibit remarkable discontinuous changes at a specific value of pressure gradient. The specific pressure gradient, which may be called "critical pressure gradient", is proved to be around Xcr= (dp/dx)/(pUo/2d)=0.05, independently of Reynolds numbers. The vortex shedding vanishes under the pressure gradient more than Xcr.

DOI： 10.1299/kikaib.66.789

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：日本航空宇宙学会  

The objectives of the present study are to obtain unsteady pressure distributions on a freely oscillating body and to examine its relation with the body motion. In the present experiment, a low speed wind tunnel was used, where the exit was directed in a vertical direction. The shape of the model is similar to a Chinese pan with a diameter of 480mm. This experiment was performed at two flow velocities: 10m/s and 20m/s, and the model was suspended from a bar above the wind tunnel exit. The model was freely oscillated in the wind tunnel flow under the gravity and aerodynamic forces. The amplitude of this oscillation was damped due to the aerodynamic forces. The pressure distributions on the body were successfully measured, which clarified the damping mechanism of the body motion. To compare with the experimental result, the unsteady numerical calculations were also performed with the boundary element method.

DOI： 10.2322/jjsass1969.44.729

Authorship：Lead author   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society for Aeronautical and Space Sciences  

Surface and back pressures, and three aerodynamic force components for two models of reentry vehicle: the cocoon type and the pan type, were measured at three transonic flow speeds: Mach number of 0.6, 0.7 and 0.8. Schlieren photographs were also taken to visualize the flow pattern. Comparing the results of force measurement with those calculated from measured pressure distributions, reasonable agreement was obtained. The Euler equations were also solved for a case with attack angle of 0 deg and Mach number of 0.8. In spite of good agreement on pressure distribution along the forward part of model, there was some discrepancy in back pressure between numerical calculation and experiment, which produced difference in drag coefficient. When the back pressure was then replaced by the experimental data, reasonable agreement of drag coefficient was obtained between them. As a result, it turned out that the pan type was more appropriate as a reentry vehicle than the cocoon type.

DOI： 10.2322/jjsass1969.43.696

Other Link： https://jlc.jst.go.jp/DN/JALC/00037366513?from=CiNii

Language：Japanese  

Language：Japanese  

Language：Japanese   Publisher：一般社団法人 日本機械学会  

Language：Japanese   Publisher：一般社団法人 日本機械学会  

Language：Japanese  

Language：Japanese   Publisher：一般社団法人 日本機械学会  

Language：Japanese  

Language：Japanese  

Language：Japanese   Publisher：一般社団法人 日本機械学会  

Backward-facing step flow, which is one of typical separated-reattachment flows, is controlled with a synthetic jet. The jet is added at the vicinity of the step edge. The flow is measured with laser-Doppler velocimetry, hot-wire anemometry and particle image velocimetry, and results obtained with these methods are compared. Details of flow field structure including the reverse flow region are clarified with time averaged and phase locked averaged technique. Mixture of fluids in the mainstream and the reverse flow region, which is considered as a cause of displacement of reattaching point, is stimulated by random component of the velocity fluctuation rather than periodic component.

Language：Japanese   Publisher：一般社団法人 日本機械学会  

Language：Japanese   Publisher：一般社団法人 日本機械学会  

Language：Japanese   Publisher：一般社団法人 日本機械学会  

Language：Japanese   Publisher：一般社団法人 日本機械学会  

Language：Japanese   Publisher：一般社団法人 日本機械学会  

Language：Japanese   Publisher：一般社団法人 日本機械学会  

Language：Japanese   Publisher：一般社団法人 日本機械学会  

Language：Japanese   Publisher：一般社団法人 日本機械学会  

Language：Japanese   Publisher：一般社団法人 日本機械学会  

Language：Japanese   Publisher：一般社団法人 日本機械学会  

Language：Japanese   Publisher：一般社団法人 日本機械学会  

Language：Japanese   Publisher：一般社団法人 日本機械学会  

Language：Japanese   Publisher：一般社団法人 日本機械学会  

The lattice Boltzmann method (LBM) gives unphysical results, in particular, near the wall boundary when arrangement between the wall and the lattice is asymmetric. The authors proposed a method which made set of the lattice velocities rotate randomly at every time step on each lattice node to overcome the problem. This method holds mass, momentum and Boltzmann's H-function conserved for distribution functions of each lattice velocity size, and thereby it can be applied only to the 2-dimensional 9-velocity (D2Q9) model. In a present report, this method is applied to the other model with an appropriate division of the mass conservation and it is shown that it works but keeps a problem of giving inaccurate flow properties observed in the D2Q9 version. However, if one selects the collision frequency of unity, the precise results, which agrees with previous results very well, can be obtained with this method.

DOI： 10.1299/jsmemecjo.2003.2.0_291

Language：Japanese   Publisher：一般社団法人 日本機械学会  

3 dimensional wake structures behind rectangular flat-plate wings with aspect ratios of 0.1∿1.0 have been investigated using Laser Doppler Velocimeter and yaw-probe. Flow details, such as vorticity vectors and vortex lines in the wakes, have been analyzed for the 5 typical flow configurations (PS-1∿PS-4,FS), which were classified in the previous report from the measurements of aerodynamic characteristics and surface flow visualization. Trailing vortices are clearly formed for flow configurations, PS-1 and PS-2. Ring-type vortices are shed for FS. Vortex structures for PS-3 and PS-4 appear to be mixed types of trailing vortices and ring-type vortices.

DOI： 10.1299/jsmemecjo.2003.2.0_341

Language：Japanese   Publisher：一般社団法人 日本機械学会  

Detailed aerodynamic characteristics and near field flow structures of delta wings with aspect ratios λ=1.28∿4 at angles of attack α=0∿90° have been presented. In high angle of attack regions near α_C_L_<max>, flow details for small λ, (1.28∿2), are mostly similar to each other, which leads to the similar values of α_C_L_<max> and C_L_<max>, whereas reattached flow regions for aspect ratios (2.4∿4) are severely affected by λ, then α_C_L_<max> and C_L_<max> decreases with and increase in λ. In full-stalled regions (α>50deg.), entirely separated flows appear all over the suction surfaces irrespective of λ, then C_L and C_D can be represented by sinα and cosα of the (C_D)_<α=90>. In intermediate regions between them, highly unsteady natures, in which longitudinal and ring-type vortices are alternatively formed, then aerodynamics are changed with α corresponding to the fraction ratio of the both vortex types.

DOI： 10.1299/jsmemecjo.2002.3.0_337

Language：Japanese   Publisher：一般社団法人 日本機械学会  

A system and a procedure shown in a previous report, which can identify location of sound source by near-field acoustic holography method using sound fields apart from the source measured with a small pressure transducer in a uniform flow, was applied to detection of a discrete frequency noise, DFN. It has been verified that three-dimensional distributions of sound fields can be estimated fairy well with this system from the tests for pressure fluctuations on a circular cylinder. Moreover, sound pressure distributions over the entire surface of a flat plate aerofoil with various boundary layer manipulations were estimated. As a consequence of additional consideration with an aid of experimental data of pressure fluctuations on aerofoil as well as coherent flow structures near it, four different types of DFN generating mechanisms have been proposed.

DOI： 10.1299/jsmemecjo.2002.3.0_155

Language：Japanese   Publisher：一般社団法人 日本機械学会  

Lattice Boltzmann Method (LBM) has been extended to complex geometries with various procedures although it is originally a numerical method calculating flows on regular symmetrical lattice. In this paper, numerical simulations with LBM of D2Q9 lattice, BGK approximation and interpolated-supplemented are carried out for flows around 2-dimensional circular cylinder to illustrate influences on the flow properties especially on the cylinder's surface as a result of directional nonuniformity of discretized lattice velocities caused by confining molecular velocities to finite number. We propose a method which makes the set of lattice velocities rotate at random with conservation of total mass, momentum and Boltzmann's H-function for distribution functions of each lattice velocity size. This method applies to the above simulation of 2-D circular cylinder and the result shows independence of lattice structure while oscillative characteristics which can be removed with time average appears.

Language：Japanese   Publisher：一般社団法人 日本機械学会  

Aerodynamic characteristics and near-field flow fields of rectangular flat-plate wings with very small aspect ratios, λ=1∿0.05 at full angles of attack, α=0∿90 deg, have been presented. The flow details were investigated using oil film flow visualization and PIV measurements. The typical features of surface flows on wings with various aspect ratios can be classified into 6 types, i.e., un-separated(US), partially separated(PS-1) with U-type flow reattachment, PS-2 with O-type reattachment, PS-3 with long cigar-type reattachment, PS-4 with indistinct reattachment and fully separeted(FS). The aerodynamic characteristics and near-flow structures of test wings can be classified into three groups corresponding to their aspect ratios, which are (1) small aspect ratio wing (λ=1), (2) smaller aspect ratio wings (λ=0.75∿0.66) and (3) very small aspect ratio wings (λ=0.5∿0.05). It has been confirmed that the aerodynamics and detailed flow structures investigated exhibit very close correlations.

DOI： 10.1299/jsmemecjo.2002.3.0_335

Language：Japanese   Publisher：一般社団法人 日本機械学会  

A new procedure to estimate aeroacoustic noise source using near acoustic holography (NAH) method has been proposed. In this procedure, sound pressure distribution is obtained with combination of a single small pressure transducer and PLA method instead of a microphone array system not to disturb the flow field. It was applied to known sound field and following results were obtained. Sound resolution of this system is about a half of measuring meshes. Identification of two same sources is attained with measuring on surface at distance within 2/3 of spacing of two sources. Same accuracy can be obtained for the estimation of sound sources in flows. It is shown that this system has reasonable accuracy to estimate the location of aero acoustic noise sources.

DOI： 10.1299/jsmemecjo.V.01.1.0_171

Language：Japanese   Publisher：一般社団法人 日本機械学会  

Aerodynamic characteristics and flow structures in wakes of delta wings with aspect ratios of 1.28〜4.0 have been investigated at angle of attack 0 ° to 90 °. The Reynolds number based on the maximum chord length is 1.3×10^5. The delta wings with λ=1.2〜2.0 indicate mostly similar C_<Lmax> and α_<C_<Lmax>>, whereas those for delta wings with λ=2.4〜4.0 change gradually with an increase in λ, but in the unstalled and full stalled conditions, the aerodynamic characteristics are quite similar independently of λ. In the unstalled region, clear trailing vortices are formed in the wakes and ring-type vortices which correspond to their aspect ratios are formed.

DOI： 10.1299/jsmemecjo.II.01.1.0_197

Language：Japanese   Publisher：一般社団法人 日本機械学会  

Language：Japanese   Publisher：一般社団法人 日本機械学会  

Language：Japanese   Publisher：一般社団法人 日本機械学会  

© 1994 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. The objective of the present study is to determine the motion of a freely oscillating body from the outputs of accelerometers and a force balance. In the present experiment, a low speed wind tunnel was used, the exit section of which can be arbitrarily inclined. The exit shape is a regular octagon with a diameter of about 2 meters. The model takes a shape like Chinese pan and its dimensions ate 48cm in diameter and 14cm in depth. This experiment v/as performed at two flow velocities: l0m/s and 20m/s, and the model was hung from a bar above the wind tunnel exit which is turned upward. The model was freely oscillated in the wind tunnel flow by the action of gravity and aerodynamic forces. The amplitude of this oscillation is damped due to aerodynamic forces. The outputs from the accelerometers and the force balance were successfully analyzed by our newly developed method to obtain the motion of the model. Thus, the dynamic aerodynamic forces acting on an oscillating blunt body were revealed, which play an essential role in damping the body motion.

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Micro UAVs are used under various circumstances nowadays. Their bodies are often made in light weight and processible materials such as plastics. These bodies can be morphed and vibrated easily by aerodynamic forces because of low rigidity. These actions also affect aerodynamic forces. In this study, modification to aerodynamic characteristics by morphing and vibration of planar wings with various Young’s modulus are investigated experimentally as well as flow fields around the wings. Motions of wings are obtained with a high-speed camera. Flows around the wings are evaluated with phase locked PIV technique. As a result, bending vibration of the wings is observed almost all over the angels of attack and twisting one being around the angles giving maximum lift force. Larger aerodynamic forces and delay in the stall are given under the condition that the twisting vibration occurs. Analysis of high-speed movies shows that amplitude of the twisting determines magnitude of variations in aerodynamic forces. The flow field observations indicate that the twisting vibration generates vortices near the trailing edge and they induce a flow toward upper surface of the wing. It reduces the volume of the separation bubbles on the wings, in particular, around center of the wing span.

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

近年，ドローンと呼ばれる無人の小型航空機が大きな注目を集めている．ドローンの機体には，加工が容易で軽量である合成樹脂が用いられることが多いが，このような非金属材料は剛性が低いため，空気力により容易に変形や振動が生じることが予想される．本研究では柔軟性を有する三次元平板翼を対象とし，翼の剛性，流速等を系統的に変化させ，翼に生じる変形・振動を計測すると同時に時間平均空力特性の測定を行い，翼の変形・振動による空力特性の変化を明らかにした．

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

一様流中において任意の角速度・角加速度でピッチング運動を行う種々の形状・縦横比を有する三次元翼に作用する非定常空力特性を実験的に明らかにした．その結果，定常状態において失速しやすい翼の方が，ピッチング運動時に非定常性が顕著に現れること，非定常空力特性は，一様流が翼弦長分の距離を流下するのに要する時間で無次元した無次元時間等の導入により整理することができること等を示した．

Presentation type：Oral presentation (general)  

二次元円柱近傍の速度変動波形にウエーブレット変換を施すことによって，円柱から放出される大規模組織渦列の瞬時における放出周波数および渦強さを算出し，この時系列変化に対して周波数分析，相関解析等の統計的処理を加えることによって，渦放出現象の揺らぎ特性の詳細について明らかにした．さらに，個々の放出渦およびその前後の放出渦の放出状態の関係を定量的に分析し，渦放出現象に生じる揺らぎの状態の詳細について解明した．さらに，これらの知見を基にして，渦放出時に揺らぎが生じる機構を説明することができる「揺らぎモデル」を提案し，上記の種々の揺らぎ現象が良く説明できることを示した．

Presentation type：Oral presentation (general)