In this study, we focused on caulking junction and strength of automobile parts which are the differential case and the ring gear. The caulking junction is a junction method utilizing the plastic deformation of metals. In this test, it was prepared fastening margin of three types of 0.1mm, 0.05mm and 0.025mm. First, performed a torsion test for measuring the torque of the miniature model of the differential case and subjected to stress analysis and contact analysis using that value. As a result, we researched the trend of friction stress in shear stress analysis and connecting surface by each fastening margin. Then, we were subjected to the same analysis in full scale model. This result was consistent with the trend of miniature models. However, the fastening margin of 0.1 mm is predicted to break from the theorem of Tresca. Therefore, it becomes possible that the material by setting the fastening margin of 0.05 mm to 0.1 mm is fixed without breaking.

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In recent years, influenced by the earth's environment and energy problems, honeycomb structure of lightweight structure in the automotive, aircraft, machines, and other fields has been widely used. However, because of too pursuit of lightweight, part of the structure are prone to rupture, makes the structure of whole rigid abate, deformation increase. The mechanical structure of the vibration noise becomes more intense, structure quality will appear all sorts of problems. Want to solve this problem, so a lot of light in the field of tough high require material. Lightweight way among them, the machinery industry strength and toughness, vibration and energy absorption characteristics of the conflict is very good, and reduce the cost, also truss core panel development concern. The new truss core panel has been developed using a composite material of glass fiber reinforce plastics (GFRP) to improves the of strength material. In this research, truss core panel of GFRP is produced, and the strength of product is discussed.

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An advantage of carbon fiber reinforced plastics (CFRP) is tailorable mechanical property by changing the lay-up designs since each layer has strong anisotropy. For more effective use of tailorable anisotropy of composites, an idea of using blended layers has recently been proposed. The blended layer has partly different fiber orientation angle in the same layer but straight fiber in each area, resulting in constant volume fraction of fibers. The present study proposes an analytical method for natural frequencies of the laminated plate with blended layers by using the Ritz method based on the classical lamination plate theory. The Ritz method makes it reasonable to conduct parametric study and optimization involving vast number of repeated calculations. The validity of calculation is verified by the comparison of results from the present method and FEM. Then, areas and their fiber orientation angles of blended layers are optimized by using a genetic algorithm to maximize their fundamental frequencies. Numerical results revealed the existence of specific tendencies in the fiber orientations of blended layers on boundary conditions of plate, and the plate can achieve higher fundamental frequencies than those from typical laminates. From above, it is demonstrated that the present method provides good accuracy for the laminated composites with blended layers and the effectiveness of the blended layer design.

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Golf is the sports that have been enjoyed by the people of a wide age group. The many golfers aim to get the high score and hope to getting the longer distance and to raising the ball speed with the golf club (Driver). And the improvement of the golf club head has been accomplished. In 2008, the upper limit of the coefficient of restitution of the golf club head was regulated. Therefore, the study of the golf club shaft comes to attract more attention. The authors already proposed the swing simulation referring the swing image of the golf swing robot. In the proposed swing simulation, the finite element model of golf club which consists of the golf club head and the laminated composite shaft is used. In this study, using the proposed swing simulation, the effect of the swing speed to the behavior of the swinging golf club shaft is clarified.

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Alpine ski racing is a competition in which the skier who skis down the course in the fastest time is the winner. Suitability of a ski boot design for the leg frame of a ski athlete is important to achieve a fast time and a win in a race. Performance of the ski boots acts as an interface between the physical performance of the skier and the performance of the skis. Speed in alpine ski competitions is becoming faster every year due to improvements in skis, boots and wax. Therefore, research and development of ski equipment based on engineering concepts is needed to further enhance performance and guarantee of safety of ski athletes. On one hand, ski athletes cannot win a victory in the races without skillful ski turn technique even if they use suitable ski boots. This report introduces the results of studying on the newly designed ski boots and skill analysis of the turn technique as an approach to a win in alpine ski races at the Olympics based on engineering for Japanese ski athletes.

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We have studied the ski boots design based on the characteristic of the frame of the Japanese player experimentally to shorten finish time for the purpose of the improvement of the competition results of the alpine skiing player. However, understanding and the practicing of the technique to use the potential of the tool are important as well as modifying the design of the tool for shortening of the finish time. This paper focuses on the energy dissipation by the bending motion and the energy increase by the stretching motion at the change of turn, and clarify a turn technique to shorten the finish time. We analyzed the influence of energy balance during the joint movements on the finish time with posture analysis of the movie of world cup competitions by using a 3DCAD model. The results shows that shortening the finish time is achieved by reducing the number of bending motion and increasing the number of stretching motion while downhill. In addition, this paper shows that the joints motions of the skier during downhill can be estimated precisely by proposed analysis method using 3DCAD model.

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This study investigates a design of a new foot bed for ski boots which can improves the angular velocities of lean motion of skier to decrease the time of alpine ski races for all of the alpine skiers. The subject is the five top level alpine-skier in Japan, and the experimets are carried out by using a ski simulator "Skytec". The foot pressure distribution and the angular velocity during lean motion are measured by using the "Pedar"(foot pressure distribution sensor) and a gyro sensor. Also this study measures the downhill time in the field test. The experimental results revealed that the movement of the center of plantar pressure distribution in the horizontal direction and the position of the foot pressure at the begining of turn affect to the angular velocity of lean motion. In addition, this study show that competition results are improved effectively by attaching the proposed parts to the front of the foot bed bottom.

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Large deflection analysis of bending was performed by the finite element method using curved beam elements. The calculation was performed on the basis of the infinitesimally small strain theory and the non linearity due to the change in the loading direction during large deformation was considered. As a result, the deviation from the linear bending deflection appeared. Simultaneously, the deflection of a ski of conventional type with a curving shape was measured by three-point bending where the load was limited within the range of normal use; i.e. the static load applied in the bending was less than 700N, which subjected the curvature of not less than 1.4m. Since the load-deflection relationship obtained was almost exactly linear, no geometrical nonlinearity was found in the bending under the present condition.

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Skiers feel floating sensation in skiing on powder snow. In order to clarify turn mechanism I skiing we have developed measuring devices such as a goniometer, force sensors, pressure sensors, a reflection sensor beam, and so on. In this study the pressure sensors and the reflection sensor beam were used to acquire the actual data during skiing on powder snow. We considered about the cause of the floating sensation by the results.

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We developed a hardness tester with falling the weight by improving Kinoshita hardness tester. In our previous study, hardness of snow surface had been measured by indenting a conical indenter perpendicularly to snow surface. In this study, a square plate indenter has been adopted in order to suppose ski edging that is indentation profile in skiing, and been indented obliquely to snow surface to measure the hardness. We changed measurement condition (mass, falling height, number of falling motion of the weight) and snow surface condition (grain size, temperature, density of snow) to investigate the effect of the conditions on hardness of snow surface and to compare with previous results by the conical indenter. Moreover, the cross section after indentation was observed by the ink method, and the forming mechanism of indentation profile was considered.

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Several theories of the friction on snow and ice have been suggested. Especially, the melt-water lubrication theory proposed by Bowden and Hughes has been widely supported. However, even in very cold environment, such as water cannot exist, the surface of hard snow could be slippery, that was noticed by Nikki in skiing in Antarctica. It could be also difficult to explain some of experimental results reported recently. In this study we have measured the coefficient of friction statically and dynamically on various snow surfaces to consider the mechanism of friction fundamentally. Influence of surface energy of slider, grain size of snow, temperature, contact time (experiment on static friction), and sliding velocity (experiment on kinetic friction) has been investigated with various polyethylene for ski.

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Rocket turbopump is high-speed, high-power turbomachinery that has often suffered from rotor vibration problems. A circumferential hydrodynamic segmented seal (segment seal) is often applied to completely separate the turbine from the pump in the rocket turbopump. It is important to elucidate the effect of the rotordynamic fluid force of the segment seal on the rotor vibration. However, the effect has never been examined. The purpose of this study is to clarify the rotordynamic characteristics of the segment seal and the impact of this force on rotor vibration. The experimental results of the rotordynamic fluid force of the segment seal under whirling motion of the rotor are reported in this paper. Experiments were conducted by using the rotordynamic test stand of JAXA (JARTS) with active magnetic bearings. It was found that the rotordynamic fluid force of the segment seal has positive influence for stability of the rotor because the radial forces had a restoring effect and the tangential forces had a damping effect. The damping effect will be generated by the friction force on the secondary sealing surface and the squeeze effect.

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Rotordynamic fluid forces and a mechanism of their occurrence were examined in experiments and computations for a closed type centrifugal impeller in whirling motion. The rotordynamic fluid force on a front shroud was a main component of the rotordynamic fluid force. Velocity disturbances in a clearance between the front shroud and a casing were caused by an eccentricity of the impeller and a squeeze effect due to the whirling motion of the impeller. Appling the Bernoulli equation to swirling flow in the clearance in a relative coordinate fixed on the whirling motion, the pressure disturbance which generated the rotordynamic fluid force could be reasonably explained.

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The rotor dynamic (RD) fluid force has been used for the stability analysis in the design of the rotating machinery. Recently, in order to expect the vibration of the high speed rotating machinery, it is desired to invoke the effect of RD fluid force in the analysis precisely. To this end, in this paper, the RD fluid force of the annular plain seal for the case of concentric circular whirl is considered, and the dependence of the RD fluid force on the rotational speed is investigated. As a result, it is clarified that the coefficients of the quadratic function for the normal and the tangential components of RD fluid force are represented as the function of the rotational speed, and the characteristics of these coefficients are explained.

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Design of inner flow network is one of the major issues in turbopumps. Inner flow network involves other components of turbopump, such as impeller, turbine, bearing and shaft seal. So design of inner flow network is used to be done in the latter phase of turbopump design, but it is difficult to find a solution of inner flow network in some cases. In this paper, inner flow network is designed for some turbopumps which are designed in different rotational speed, and analysis results are compared. From the results turbopump designed in high rotational speed has not good characteristics about inner flow network.

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Turbopumps are high-speed turbomachinery which feed the cryogenic propellant to the combustion chamber for rocket engines. Rotor vibration problems caused by the increase of power have occurred under development of turbopumps. Authors had proposed the morphology design method as way of resolving the rotor vibration problems. In this study, superior solutions are investigated by the morphology design method. Besides, the effect of the rotor morphologies on vibration characteristics such as system damping ratios and vibration amplitudes are discussed. The optimal rotor arrangement for the suppression of the rotor vibration was proposed by the morphology design method. Trend of the vibration characteristics for the permutation and direction of the rotor elements was shown.

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An externally pressurized gas journal bearing with an asymmetric gas supply mechanism has been developed. This type of bearing has a large load capacity compared with the conventional symmetric gas supply bearing because pressurized gases are supplied to the loaded and counter-loaded side bearing surfaces via asymmetrically arranged gas supply holes. The bearing load capacity of the developed bearing is considerably larger than that of conventional symmetric-type bearings. The load capacity increases owing to the asymmetry of the gas supply holes. Rotational test was conducted using eccentric rotor taking advantage of this property. The bearing diameter and length were 60 and 120 mm, respectively. Rotational vibration amplitude decreased at high rotational frequency in the proposed bearing configuration, although the amplitude increase monotonically with the frequency in the conventional bearing. The rotor of the test rig was safely supported by this bearing, and effective data for practical operation were obtained.

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A rotor system supported by a repulsive magnetic bearing has a weak damping, and therefore, a contact whirling vibration between the rotor and a backup bearing may occurs when the rotor system passes a critical speed. Four kinds of the contact whirling vibration, a forward sliding type, a backward sliding type, a forward rolling type and a backward rolling type, are possible to occur. It is desired to separate from the contacting condition at the lower rotational speed with smaller amplitude. In this study, the forward sliding contact vibration is considered, and the effective design parameters for early separation from it are investigated analitically. As a result, the larger friction coefficient and the smaller contact stiffness are effective to reduce the rotational speed of separation from the contacting condition.

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A damping device so called 'wire mesh damper' has been used between the ball bearing and the casing to increase the system damping. However, it has some disadvantages; it has moderate level of error from the nominal design, and it is difficult to achieve the designed damping performance, etc. In this study, active magnetic bearing is used as the damping device instead of wire mesh damper, and its vibration suppression effect is evaluated numerically. As a result, it is verified that the usage of the active magnetic bearing enables the turbopump system to suppress the vibration level at the third critical speed efficiently.

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Rocket engine turbopumps equip balance piston (BP) which is a self-thrust balancing mechanism, because turbopump generates large axial load derived from its high discharged pressure. BP has a stable characteristic quasi-statically, but in some cases it becomes unstable and goes into the condition of self-excited vibration. In recent studies, linearized model of BP was used and their dynamic characteristics have investigated. However, non-linear behavior of BP is not studied sufficiently yet. In this paper, non-linear simulation including axial contact between the shaft and the casing is conducted. It uses the model based on 1 dimensional model developed by Hayashi. In the simulation, bulk modulus of fluid is used as a parameter, and stability and the vibration characteristics are investigated. Particularly, the transition of the dynamical characteristics of BP from the stable condition to the self-excited vibration without/with contacting to the casing are explained. As a result, the necessity of using non-linear model including wall-contact in numerical simulation of BP's dynamic behavior is indicated.

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A multiple objective optimization method is developed as one of the model update schemes in which the analysis model of the large-scale structures is improved to adjust the natural frequency to the experimental results. In this method, multiple natural frequency modes are the objective functions. This method has been developed to be applied to the large-scale structures. In this paper, it was applied to a grooved ring problem, in which not the ring sizes and the material constant but the known groove sizes (width, depth) were presumed as unknown design variables so that the calculation error of the natural frequency of six modes might be minimum. The errors of the estimated groove sizes were 2 to 8% of to the true value and it is confirmed that a suitable model update can be executed.

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The design and test of a 10-kW, battery-powered counter-rotating fan is presented in this paper. DC brushless motors are driven by 8 packs of 4000 mAh 7S LiPo batteries which supply 160 A of discharge current and 58 V of voltage. Designed fan diameter is 144 mm and the nominal rotation frequency is 42000/40000 rpm for the forward/aft fan. The experiment was carried out at the frequency of 20000 rpm. The pressure ratio of 1.07 and the efficiency of 0.5 were measured.

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An increasing number of small-sized vehicles like a mobility scooter are being developed these years since environmental and energy- saving performance have gained considerable importance on mobility developments. When the mass of a vehicle becomes small, it is expected that motion of human body has a large influence on running performance of the vehicle, and this affects vehicle safety. Accordingly, it is important to study effects of mass ratio of a vehicle and a human on driving stability by focusing on interactions between them. This study for a personal mobility evaluation examines interactions between a vehicle and a human from simulation results by a simulation model that consists of a vehicle model like a personal mobility and a human model that expresses human motion.

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Manual handling is one of the factors that increase the risk of upper limb disorders. Especially, most of workers in Japanese primary industries still do such operations in high risk. The purpose of this study is to reduce upper limb burden during manual handling in primary industries. We performed work observation and simulated work experiment with biological information measurement. As a result, we found out that wrist support is effective to reduce the burden. Moreover, we developed the prototype wrist support which assists dorsiflexion, and measured wrist joint angle and EMG during the simulated work with it. The effect of reducing the burden has been confirmed by the measurement data.

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Today, the half of disabled people have defect in the limb in Japan. In addition, in order to stabilize the standing or walking, they have to work their muscles well. There are many rehabilitation systems for them. However, it is too difficult for severe disabled people that cannot stand or walk using rehabilitation systems. On the basis of this current situation, rehabilitation systems that severe disabled people can use safely are necessary. We focus on reach movement with seating because this is one of the basic operation they desire reacquisition when suffer from disablement and the longer forward reach length makes people more stable. In this study, in order to understand the difference between extended posture and flexuous posture by healthy people people performing reach movement, we considered influence of posture on the muscle activity and floor reaction force. Then, in order to understand how differently healthy subjects and disabled subjects, we perform same experiment by disabled subjects. As a result, we understood flexuous posture by healthy subjects and severe disabled subjects apply a force to the buttocks than the foot. Also erector spinae muscle activity is extremely small in flexuous posture by healthy subjects and the peak of this muscle activity is seen at some point in time.

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In human gait motion analysis, which is one useful method for efficient physical rehabilitation to define various quantitative evaluation indices, ground reaction forces, joint angles and joint moments are measured during gait. On the other hand, human locomotion has variously been measured and analyzed from perspective of biomechanical kinetics and kinematics. However, behavior changes in diverse physical parameters remain to be fully elucidated when interaction to environmental changes of universal road surfaces is considered. Therefore, in this study, human gait motion is measured under various conditions with changes of motion velocity and inclination angle by treadmill and mobile force plate. Next, internal biomechanical loads in three-dimensional space such as joint moments are calculated by inverse dynamics analysis applied musculoskeletal model based on the use of measured data. In the end, especially, knee joint moments are weighed among conditions of motion velocity and inclination angle. Furthermore, Features of those results are understood by quantitative evaluation.

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This paper proposes the muscle control theory analysis method to use stroke patents rehabilitation based on the muscle synergy theory. We measured the upper limb motion and muscle activity as the electromyograms (EMG). Then we calculated the muscle synergy patterns of EMG signals. The synergy pattern of affected side is different from the unaffected side. As a result, the affected side lost normal muscle synergy by stroke, it was recognized that different muscle synergy from the healthy side is appeared. By using this method, it can evaluate the recovery state of the disorder.

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A low-noise acoustic wind tunnels are usually used for the sake of clarification and reduction of aerodynamic noise. However, some cases of aerodynamic noise which are difficult to analyze enough by the experiment with only using acoustic wind tunnels have still remained without the best noise control. Two cases of aerodynamic noise with an interference air flow are introduced and consider reasons why it was difficult to measure and to analyze. Two cases are "air flow around a large scale twin tower" and "air flow passing a flow control vane with a thermal sensor". The dominant reasons might be that unsteady flow pattern did not make clear by an acoustic wind tunnel and that the test model could not reproduce the interference flow to understand by only simple experiment. Numerical simulations with respect to unsteady flow analyses and acoustic field analyses could be support to set the detail experimental condition with acoustic wind tunnel.

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The aim of this investigation is to clarify the relationship between the variation of large-scale eddies by jets in the upstream boundary layer and the reduction of cavity tone. Direct simulations of flow and acoustic fields for cavity flow were performed with installation of jets with various intervals d_j and inclination angles θ. The depth-to-length ratio of the cavity was D/L=0.5. The freestream velocity was U_0=43 m/s and incoming boundary layer was laminar. To estimate the two-dimensionality of large-scale eddies in cavity, the distributions of spanwise coherence of vertical component of velocity ν around the center of cavity were calculated. As a result, the two-dimensionality was reduced by the specific interval d_j/L=0.25 and angle θ=90°. The investigations of flow fields at downstream of jets show that high intensity streamwise eddies are induced at specific control condition and the reductions of two-dimensionality are coursed by that eddies.

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This work presents an experimental investigation for effects of the spanwise spacing of small-jets placed in the approaching boundary layer on cavity tone. The sound and velocity fields of a flow around a cavity were measured with a low noise wind tunnel. The freestream velocity was changed from U_0 = 10-45 m/s. The depth-to-length ratio of the cavity was D/L = 0.5. The upstream boundary layer is laminar, and the boundary layer thickness is δ_<99%>/L = 0.08 at U_0 = 43 m/s. The effects of the jets from the wall in the upstream boundary layer with various spanwise spacing p/L = 0.1, 0.25, 0.6, and 1.25 on the cavity tone were investigated. The jet velocity at the central axis of jet was changed from U_j = 2.2-4.0 m/s. The results show the cavity tone can be reduced by control of blowing jets. The control effect on the cavity tone depends on the spanwise pitch and velocity of blowing jets. In this experiment, the most effective pitch of jets for noise reduction was p/L = 0.25. The reduction level increases as the jet velocity becomes higher. The noise reduction effect becomes sufficiently large when the jet velocity is higher than 3 m/s. The three-dimensional spanwise velocity field was induced by blowing jets. As a result, the spanwise coherence of the vortices inducing intense sound became weak, and the radiating sound became weak.

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The fan used as PC cooler, blower, etc. generates aerodynamic noise that is uncomfortable, therefore fan noise reduction is required. The aerodynamic noise has two main components; rotational noise and broadband noise. It is necessary to construct analytical model of these noises for noise reduction. The purpose of our research is constitution analytical model of rotational noise generated by axial fan to calculate sound pressure level (SPL) of the noise. Our model assume the area blades passing are many point sound sources. Characteristic of any sound source are calculated from geometry of fan. Acoustic transfer function of any sound source to observation point are measured by using reciprocal theorem. The calculated result of second harmonic noise by the model was agreed with experimental result, but other harmonic noise were not agreed. The model is necessary be improved for practical applications.

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In order to explore the essential characteristics to pronounce sibilant fricative /s/, we prepared the simplified vocal tract models and compared the sound and the flow characteristics in the models with that in the realistic model which was constructed from the CT images. The two simplified models having a constriction at center position (CN model) and upper position (UN model) were proposed. The far-field sounds generated from the models were measured by a microphone. The large-eddy simulation was conducted and aeroacoustic sound sources was calculated in the models. The sound generated from UN model was similar to the sound generated from the realistic model compare to that of CN model. The velocity fluctuation and the sound source nearby the exit of constriction of CN model were larger than that of UN model and realistic model, indicating that reduction of the turbulent flow in the upstream of incisors is essential to pronounce sibilant /s/.

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Effects on absorption performance of acoustic panel configurations for turbo fan jet engine were examined experimentally. Acoustic panels for test were made from plastics, by 3D printer. The experiments were carried out in the transfer function method using two microphones. Experimental result indicates triangle or square cross-sectional shape holes in the surface sheet were more effective than the circle shape concerning the sound absorption coefficient.

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An aerodynamic sound generated by a flow inside a pipe is one of the noise problems. In addition to the aerodynamic sound sources, a characteristic of the generated sound is sometimes affected by acoustic and vibration characteristics of the pipe. In this paper, we have performed the experiments and simulations to clarify acoustic and aerodynamic sound characteristics of a T-shaped rectangular cross-sectional pipe. The experiments and simulations were performed under several inflow velocity conditions. The results show that the characteristics of the generated aerodynamic sound in the pipe are strongly affected by the acoustic characteristic of the pipe. Frequency characteristic of the generated sound sources depend on the inflow velocity conditions. However, that of the generated sound does not depend on the inflow velocity conditions, but on the acoustic frequency characteristic of the pipe.

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Surface shear stress is generated by flows near a solid object. For several decades, whether surface shear stress fluctuation is a sound source or not has been discussed. On the one hand, Howe insisted that surface shear stress fluctuation is not a sound source. But on the other hand, Shariff and Wang claimed that shear stress fluctuation is a sound source by numerical simulation. In this paper, surface shear stress fluctuation is studied on the condition that shear stress fluctuation is a sound source. We computed the time evolution of surface shear-stress caused by vortex pair colliding with a non-slip wall. It is revealed that surface shear-stress fluctuation is influenced by secondary vortex on the wall very much. An absolute value of surface shear-stress is increased when a vortex pair approaches the wall because of an increase of an absolute value of vorticity of secondary vortex. After, an absolute value of surface shear-stress is decreased and the position of maximum value of an absolute value of surface shear stress is changed because the vortex pair is separated with secondary vortex. This surface shear-stress fluctuation mechanism might be a one of the sound source.

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Motors are widely used in various factories. Because these motors is operated bi-directionally, radial blade centrifugal fan is widely applied to the cooling fan of the electric motor. In this study, it is proposed the new mixed flow fan to improve the fluid performance and low noise. It is compared the performance and noise for the ordinary fans and new type mixed-flow fans mounted on the motor experimentally. It is investigated the aerodynamic characteristics of both fans using numerical flow simulation.

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The increasing of the aerodynamic force and aeroacoustic noise are caused by the vortex shedding generated from a circular cylinder. The decreasing of these phenomena is one of the important issues in engineering. In order to reduce the aerodynamic force, the drag force of the cylinder attached with the cylindrical rings was experimentally measured. As a result of this study, the flow fluctuation behind the cylinder was suppressed and the drag reduction was confirmed. In this study, the reduction effect of the aeroacoustic noise generated from the cylindrical rings is investigated by the low-Noise wind tunnel in the Reynolds number ranged from 1.4 to 4.2 × 10^4. The sound pressure level decreases from 13 to 20 % at these ring pitches of 2 and 4 in comparison with the no rings.

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The noise generated from the internal flow in a centrifugal blower was computed by computational aero-acoustics (CAA). The rotational speed of the impeller of the centrifugal blower is 3000 rpm. The sound sources were obtained by computational fluid dynamics (CFD), using large-eddy simulation (LES) to compute the turbulent flow in the centrifugal blower. The sound field was computed by solving the Lighthill's equation in the frequency domain with the finite element method (FEM). The results of CAA are compared with the experimental data measured by a microphone. The sound pressure level (SPL) computed with sound source from coarse-mesh LES is overpredicted, while the SPL computed with sound source from fine-mesh LES agrees reasonably well with the experimental data. The peak of SPL at the blade passing frequency (BPF) is underpredicted. The peaks of SPL at the second harmonic and the third harmonic of BPF are not captured by CAA.

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In this paper, surface pressure and NACA0012 airfoil flows are measured by wind tunnel test with inflow turbulence using the active turbulence generator (ATG) in order to clarify unsteady airfoil flows behavior contributed to airfoil noise under atmospheric turbulence. Turbulence intensity of the inflow can be changed from 9.3 % to 19.5 % and integral scale of the inflow can be changed from 298 mm to 1592 mm. The Reynolds number based on the chord length of the airfoil and flow velocity is 3 × 10^5. As the results, short bubble generated on suction surface seems to be disappeared by the inflow turbulence. The turbulent intensity affects static pressure fluctuation on the leading edge of the airfoil. The integral scale affects fluctuating surface pressure from the leading edge to the trailing edge. The inflow turbulence does not affect only increasing of uniform flow turbulence, but also increasing of airfoil flow close to the suction surface.

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This paper deals with an experimental study of flutter on a flat plate suspended by wires. The influence of the suspending angle, the length of wire and aspect ratio on the flutter velocity, frequency, and mode are clarified. Moreover we examined the influence of the attack angle on the flutter and vortex induced vibration characteristics.

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To assure the complete stability and long-term safe operation of the large number of Tainter gates used worldwide, an effective method of distinguishing those gates susceptible to instability from unsusceptible gates is essential. For this purpose, the authors have undertaken field vibration testing of several operational gates to identify the dynamic stability of these Tainter gates. From the specific test data for a limited number of operating conditions, our theoretical analysis permits assessment of the dynamic stability of the gate for all operating conditions. At that time, it should be consider the effect of the upstream water level to the natural vibration mode of the gate. When the upstream water level changes, the in-water natural vibration characteristics will change due to the water added mass effect. The theoretical analysis for the in-water natural vibration frequency depends on the water level changes has already been established. Therefore, it is possible to determine the complete dynamic stability if it can be identify the vibration mode change with changing the water level. For this purpose, the authors have undertaken the 3-dimentional model tests, to consider the effect of the upstream water level has on the natural vibration mode. This paper presents the model test results and consideration of in-water vibration mode.

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This paper deals with an experimental study of a flutter on a cantilevered rectangular sheet between walls subjected to axial fluid flow. The influence of the gap ratio and aspect ratio on the flutter velocity and frequency are clarified. The fluid force distributions on the wall surface coupled with motion of the sheet which is fluttering are clarified by measuring pressure on the wall surface and displacement of the sheet.

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With the power-generating plant, there is a problem of most caused by vibration. Even among those, the phenomenon that we must be careful about in particular is fluidelastic instability. There are a number of columns in U-tube heat exchanger and fluidelastic instability may occur. When fluidelastic instability occurs in tube group, it might be damaged by a tube next to each other bumping it, and being worn. Fluidelastic instability is extremely destructive vibration. In the past research, Energy is taken out by in-flow fluidelastic instability in the air and we used a phenomenon in limit cycle to raise the voltage stably after fluidelastic instability occurred. But in this study, to extract more energy from fluidelastic instability, we increased the number of test cylinders which generated electricity and tried that increased the voltage. Test array is triangular array. The cylinder is supported with a thin plate limiting motion to only the in-flow direction

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This paper deals with a vibration analysis and experiments of the self-excited vibration in a flow dynamics conveying machine. In this study, unstable conditions and unstable regions of the self-excited vibration in the case of that the air bar has 1slit and 2slits are examined by theoretical analysis. Experiments are conducted with the plate floated by an air, and vibration characteristic and unstable conditions are examined. Moreover, the unsteady fluid force acting on the plate surface is examined by measuring pressure between the air bar and the plate, and the local work by the unsteady fluid force on the plate surface is clarified.

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This paper deals with an experimental of self-excited vibrations translational single degree of freedom excited by the leakage flow through contraction. In this study, the influence of gap width and the shape of the contraction part on the critical flow velocity are examined experimentally. Moreover, we measured the unsteady fluid force acting on the plate and calculated the local work by the fluid force on the plate surface. As a result, it is found that the critical flow velocity is increasing as the gap width of the contraction part become wider. And the vibration is excited because the fluid force act the positive work on the upstream side of the contraction part.

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This paper describes verification and examination in applying Mathieu functions for constructing Non-compact Green functions for wing-like body. First the paper reviews composition of plane wave and scattering wave by Bessel functions for cylindrical body. Key idea is introduction of Bessel functions and Hankel functions in the composition. Similarity of Mathieu functions in elliptic cylindrical coordinates with Bessel functions in circular cylindrical coordinates is utilized for constructing the Non-compact Green's function for wing-like bodies. Adequacy of Mathieu Functions are examined in their behavior in neighborhood of body surface. Lastly the paper discusses application of the new Non-compact Green's functions to designing low-noise wing with porous surface.

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In this paper, three components of flow velocity around NACA0012 airfoil in some two dimensional sections are measured by using the stereo PIV method in order to clarify flow structures and unsteady behavior of airfoil tip flows contributed to tip flow noise. 2D3C stereo PIV measurements of the airfoil tip flow with double pulsed YAG laser in maximum power of 50 W, two high speed CMOS cameras and dioctyl sebacate as tracer are carried out. The camera condition is 512 pixel × 512 pixel resolution and 2 kfps and 6 kfps frame rates. The Reynolds number based on the chord length of the airfoil and uniform flow velocity is 1.3 ×10^5 and 3.3 × 10^4, and the airfoil is under the high lift condition. Far field sound is measured 1 m away from the airfoil in the perpendicular to main flow. In the test section, the airfoil is vertically installed and the laser sheet source is radiated over the airfoil perpendicular to the uniform flow. Band pass filtered velocity characteristics with non dimensional frequency of 20 to 32 are shown.

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The ultimate objective of this study is to predict aeroacoustics noise radiated from a centrifugal blower. The test blower has 12 impeller blades and a vaneless diffuser with a scroll. We performed one-way coupled simulation of internal flow computation and acoustical analysis. Firstly, we performed internal flow computation to get sound source data. Computed unsteady fluid force acting on an impeller of the test centrifugal blower was converted to a dipole sound source located at the center of an impeller. In this paper, prediction of source of aeroacoustics noise is reported. Pressure fluctuations on the surfaces of the impeller blades and the casing of the blower were computed by performing large eddy simulations (LES) with computational meshes composed respectively of 10 million, 80 million, 640 million and 8 billion grids. The predicted pressure fluctuations on the surface of the casing were compared with measured data. Relationship between accuracy of the prediction and grid resolutions was investigated.

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This paper deals with a flutter analysis and experimental study of a inclined web received local cross-flow. The unsteady fluid force acting on the web surface is calculated by using Doublet-point method, which is based on the unsteady lifting surface theory. The equation of motion of the sheet coupled with the fluid flow is derived by employing the finite element method. The stability of the system is examined by the characteristic roots obtained from the flutter determinant. The effects of inclination angle, non-dimensional tension, aspect ratio, cross-flow distance on the flutter velocity and mode are clarified. Moreover, the local work by the fluid force on the sheet surface, and instability mechanism are clarified.

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Flapping flights seen in birds and insects have been studied for purpose of the development of small aerial robots with flapping wings for many years. Biological wings are flexible so that they passively deform depending on aerodynamic force and inertia force. The wing deformation is structurally tuned with multiscale complex structures such as feathers of birds. On the other hand, typical structure of artificial wings is quite simple: The wing consists of a flat film supported by a simple framework. Here we have proposed a wing with anisotropic micro wrinkles in order to achieve fine tuning of wing deformation in artificial flapping wings. The micro wrinkles were created by utilizing self-organization phenomena in which micro wrinkles spontaneously emerge on the centimeter-scale elastomeric substrate. In this study, we first studied the influence of anisotropic wrinkles on the film stiffness by using finite element method simulation. Then we tested the fabricated wings with different wrinkle arrangements using a hummingbird-inspired tethered flapping mechanism. It was found that wrinkles perpendicular to the leading edge prevented undesirable twist of the wing film, resulting in improvement of cyclic average lift and efficiency.

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