This paper describes the experimental study of the aerodynamic characteristics of some modified non-contact type suction devices. The present study has been carried out in collaboration with OHTANI-ENG. The main aim was to reduce magnitude of jet noise. We achieved the subject and that brought about improvement of suction force simultaneously. The force curve vs. supplied compressed air has been obtained by pressure distribution on surface of wall, and the jet velocity has measured by a hot-wire anemometry at edge of the suction device. As a result, the suction force has been improved in case of "With diffuser" at end of pad. However, the improvement is depended on size of valve, that is suggested that we have to consider relation between valve shape and Coanda effect at area of nozzle jet.

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The new use of ship's heat exhaust was proposed. Immersion surfaces of ship are heated by heat exhaust including relatively low temperature heat source, for example jacket cooling water. We examined the quantitative effect of heating of ship's bottom hull on drag reduction by flat plate model experiment. The flat plate incorporating electric heater was placed at circulating water channel, and the total resistance of model was estimated. The quantitative effect on drag reduction at turbulent flow region will be proportional to the ratio of heat output to water flow velocity within experimental condition.

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Direct numerical simulation of a spatially developing boundary layer is performed with uniform wall-heating or wall-cooling aiming at friction drag reduction. The Boussinesq approximation is adopted for the buoyant force. The Richardson number, Ri, is set to be 0.01 for wall-heating and -0.01 for wall-cooling. It is found that the uniform wall-cooling has drag reduction effect, while wall-heating leads to drag enhancement. The former is due to reduction of Reynolds shear stress -<v'v'>^^^- by stabilizing of the turbulent flow with wall-cooling.

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Traveling wave-like wall deformation is applied in fully developed channel flow to reduce the skin friction drag by means of direct numerical simulation. The downstream traveling wave can reduce drag, and at some parameter sets the mean pressure gradient converged to the laminar value. In this case, turbulent fluctuation vanishes ; re-laminarization is achieved.

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We numerically investigated the effects of friction drag reduction and energy gain by traveling wave-like blowing using plasma actuators arrayed on channel walls. The obtained maximum friction drag reduction rate is 37 %. Although the net energy saving is not achieved inmost cases, some parameter sets which result in net energy saving are found.

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The effects of voltage waveform characteristics and electrode dimensions on the flow induced by using a dielectric barrier discharge plasma actuator (DBD-PA) have been investigated in this study. It is known that the flow is induced in the direction from the upper electrode to the bottom electrode, then tangential one-way flow can be generated by using DBD-PA with asymmetric electrodes. We found, however, that it is possible to reverse the flow direction in certain conditions when offset voltages with a pulse wave are varied. Setting the negative offset, the flow is reversed by applying pulse wave in any electrode dimension. It should be noted that it is not reversed by sine waves even with same amplitudes and frequencies. Our experimental results indicate that the voltage surge velocity is important to realize reversed flow induced by DBD-PA.

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Research interest in plasma actuator is increasing day by day in the field of fluid dynamics. Various types of plasma actuators are used for various research purposes. In most cases, the plasma actuator is based on a surface dielectric barrier discharge (DBD), the flow is produced between two electrodes mounted on both sides of a dielectric material and can be used in flow control applications due to the momentum transfer from the plasma species to the fluid. This paper investigated floating type DBD plasma actuators in the absence of external flow by means of particle image velocimetry. The electric wind was generated by a single DBD excited by a sine wave of 5 kHz. The induced flow was compared by changing the distance from the leading edge to the actuator position.

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Drag reduction due to biodegradable surfactant aqueous solution was investigated in the turbulent flow range. Experiments were curried out by measuring the pressure drop of a pipe flow. Test surfactant solutions are alkylpolyglycoside solutions, which are small environmental loading. It is obtained about 40 % in the maximum drag reduction ratio of the friction factor. Drag reduction effect slightly depends on the particle size in the solution. The mechanical degradation of the drag reduction due to the alkylpolyglycoside solution did not occur in this experimental condition.

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Recently, research on drag reduction has attracted considerable attention concerning the problem with energy conservation, which is closely related to the prevention of global warming. But, some difficulties remain to clarify the effect of the forming a micelle on the flow behavior of surfactant solutions with some additives in the practical applications. In this study, the experiment carried out the measurement of the friction factor of surfactant solutions added a glycol, fatty acid and potassium, and the particle size distribution of these solutions was measured by means of a dynamic light scattering spectrophotometer. Consequently, it was seen that the drag reduction phenomena do not occur in surfactant solutions added coconut fatty acid and potassium hydroxide, and was discussed the effect of the particle size distribution on the drag reduction.

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There are a few studies on the drag-reducing effects of non-ionic surfactant solutions which are non-toxic and biodegradable, while a lot of investigations for cationic surfactant solutions have been performed so far. We investigated the drag-reducing effects of non-ionic surfactant, oleyldimethylamineoxide (ODMAO), solutions by measuring the pressure drop in the circuit pipe flow. The maximum drag reduction ratio for the ODMAO solution was over 70 %, which did not depend on solution temperature and concentration. After the solution was circulated for 158 hours, the drag reducing effect disappeared.

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Spatial structure of turbulent drag reducing flow with blowing polymer solution from the channel wall has been investigated by using PIV. The instantaneous velocity fields in x-z plane were measured in the near-wall region. In this experiment, 10.6 % of drag reduction was obtained under Re=20000. As a result of PIV measurement, RMS of streamwise velocity fluctuation increases and spanwise velocity fluctuation decreases. In the drag reducing flow with blowing polymer solution, low-speed streaks spaces expanded to the spanwise direction with increasing streak thickness. This phenomenon was also analyzed quantitatively by a two-point cross-correlation coefficient. In addition, small scale component in the velocity fluctuation decays and large scale component is dominant with drag reduction effect.

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Experimental investigation on turbulent diffusion for drag reducing channel flow with blowing polymer solution from the whole surface of channel wall was performed. We measured polymer concentration distribution qualitatively and quantitatively by two methods. Qualitative measurement is by Planer Laser Induced Fluorescence (PLIF). On the other hand, quantitative measurement is that liquid sample was extracted from the channel at three different locations by the sample probe and polymer concentration of this test liquid was directly measured by Total Organic Carbon (TOC) analyzer. Based on these experimental results, relation between turbulent diffusion of polymer solution blown from the wall and heterogeneous drag reduction was discussed.

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In 1989 to 2002, the project of CDIT and 20 Company long run tests of the Wave energy Conversion System in Sakata Port. This project had practiced to observed many wave characteristic (wave height and a wave period data etc.) and verification of Design and Operation for the Wave energy conversion system( including to efficiency) And the Project had inspected Wave energy conversion system for use to pump and connection to Power grid and road heating And etc. For the results, The Wave energy Conversion system had been hold to run for 13 years in real sea site.

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The air turbine installed in the oscillating water column type wave energy converter is analyzed linearizing in order to usually work as nonlinear load. On the other hand, it is possible solving directly nonlinear characteristic in more detailed analysis, and the nonlinear time series analysis using the impulse response function is performed. The advantage of the formation of equivalent linearization is treatment by the frequency domain, and is that statistical processing is possible, there are few amounts of calculation, and a solution is uniquely determined to an irregular wave. In this paper the error treated by the formation of equivalent linearization is validated by comparison with the nonlinear time series analysis for the orifice which is of nonlinear load damping.

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The primary conversion efficiency of a "Backward Bent Duct Buoy" (BBDB) wave energy converter is measured in two and three dimensional tank experiments. The effect of duct extension on the primary conversion efficiency is investigated by attaching 15cm and 45cm ducts to the normal model. The experimental result shows that the duct extensions reduce the primary conversion efficiency because they reduce the pitching motion of the BBDB.

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A twin unidirectional impulse turbine has been proposed in order to enhance the performance of wave energy plant. This turbine system uses two unidirectional impulse turbines and their flow direction is different each other. However, the turbine characteristics have not been clarified to date. The performances of a unidirectional impulse turbine under steady flow conditions were investigated experimentally by using a wind tunnel with large piston/cylinder in this study.

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A ducted Darrieus-type turbine has been proposed for extra-low head hydropower utilization of total head less than 2m. Though the hydro turbine system, in general, consists of an intake, runner section and draft tube for higher efficiency operation, it was clarified in previous experiment that there was no need of a draft-tube and the side-walls of runner section for keeping the performance high, provided with nozzle at the inlet, which yields a simplification of the structure of the turbine system. In order to further simplify the structure, the effects of upper-wall of runner section and water levels of downstream pond on turbine performance were experimentally investigated. In the present paper, the experimental results are shown with various water levels of downstream pond.

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The aim of this study is to develop the open type runner utilizing waterfall for environmentally friendly nano-hydraulic turbine. Impulse type runner and cross-flow type one was selected and compared with each runner performance. As a result, the cross-flow runner is superior to the impulse runner. Power coefficient of cross-flow runner is reached at 0.74 in wide range of tip speed ratio.

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A new type of cross-flow turbine that is suitable for an overfall sill in the irrigation channel was developed. If the head of the turbine is very low, a draft tube is needed to effectively utilize the height difference between the runner and the water level in downstream channel as the hydraulic head. Therefore, predicting the performance of a cross-flow turbine is more difficult than that of other turbines with single-phase water flows because pressure in the runner chamber also influence the performance of the turbine. In this study, a performance prediction method for a cross-flow turbine with a very low head is developed by experimentally investigating the influence of parameters such as pressure and net head on the turbine performance.

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Micro hydro power is suitable for Japan, which has many rivers, but it is not sufficiently spread in present. On the other hand, a lot of water wheels had been used for thread twisting in the region around Ashikaga city, which is home ground of our institute, exists until early Showa era. In this study, by using properties of traditional water wheels which existed in the region around Ashikaga city, the authors set to work to develop the micro hydro turbine generator which can be used at low head condition without major construction for installation. The authors fabricated the prototype of the micro hydro turbine generator, and. carried out the performance test.

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Aero-hydro-servo-elastic simulations were conducted for a spar-type floating offshore turbine so as to investigate dynamics characteristics and fatigue loads to wind-wave direction misalignment. It equipped with a variable speed variable pitch controlled 1.5MW downwind turbine with 70m rotor diameter. Rotational deviations tend to increase as wind-wave misalignment increased, especially in high wind speed-high wave conditions. Fatigue load of tower base bending is dependent on the distributions of wave-wind misalignment. And fore-aft bending is dominant for tower base fatigue loads.

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Stand-alone small-scale wind turbine-generator systems have many problems on maintenance because they are operated in regions with less accessibility. In our target system, a straight-wing vertical axis wind turbine (with self-starting capability) is mainly operated at a constant tip speed ratio, which means a maximum power coefficient, by a rotational speed-squared load torque control. The previous studies clarified that this system possesses high power generation capability; however, it is significantly deteriorated due to performance deterioration of the wind turbine. This study develops an indicator for searching a rotational speed-squared load torque characteristic for a constant tip speed ratio operation adapted to performance deterioration of the wind turbine through a numerical simulation.

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The objective of the present work is to analyze the aerodynamic effects on the structural loads of rotor blade due to structural oscillation and inflow conditions. For the calculation of aerodynamic loads on the rotor blades, vortex lattice method based on panel method was adopted. In order to consider the blade oscillation in the edgewise and flapwise directions, a structural model with multiple degrees of freedom based on multi-body dynamics was used. The effects of the blade oscillation are taken account in the aerodynamic load calculation through the relative flow velocity due to oscillation along with the deformation and the displacement of the blades. The calculated results have been compared with the measurement results and the validity of the calculation model is evaluated.

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In order to widen the use of wind power generation, the improvement of wind farm efficiency is required. In wind farms, power loss often occurs due to the wake generated by upstream wind turbines. In this paper, we discuss the effects of wake for a single wind turbine to optimize the wind turbines layout in a wind farm. In the experiment, a Doppler SODAR near a wind turbine is installed in Aoyama-Kogen Wind Farm for measuring wake. Measurements of wind speed and turbulence intensity distributions in wake were performed in order to obtain the characteristics of the wind turbine wake. The test wind turbine which has 50.5m of diameter is located in the position of the distance about 1.86 times of rotor diameter from Doppler SODAR.

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The self-furling over-speed control system using a tail vane is simple and passive control system, which is appropriate for small wind turbines. However there are few experimental data to apply to assist the design of wind turbines. In this study, the authors examined the self-furling over-speed control system using a wind tunnel and could obtain fundamental datum to assist the design of small wind turbines.

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Power characteristics of Savonius type wind turbines with various aspect ratio whose axes were inclined were examined experimentally. Turbine powers were found to decrease sharply with the angle of obliquity. This phenomenon was more notable for blowing up wind. High aspect ratio was effective to suppress this decrease due to angle of obliquity. Savonius type turbines with two stage buckets showed extreme power decline hardly depending on buckets phase.

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An experiment was conducted to study the effect of the located position or the setting angle of a sub-blade on performance of the rotor, which the inner edge of it was always attached on the convex surface of the main blade. The chord length ratios of the sub-blade to the main blade length 90mm were prepared as 0.667 or 0.833. The two ways of location of the sub-blade was selected as changing of the opening angle and sliding to keep a constant opening on the main blade. The rotor diameter was 160mm and the wind velocity was about 5.5 m/s in the experiment, so that the Reynolds number was about 5.87×10^4. From the experimental result, it is shown that the maximum output power coefficient of the rotor with the sub-blades was succeeding about 20 percent to the normal rotor. Furthermore, the adding coefficient of the sub-blade was empirically estimated by applying the momentum theory to the flow around it and agreed well to the experiment.

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To improve Savonius rotor performance, flow suction from the upper end plate by the flow over rotor is suggested. Increase in power coefficient by the end plate hole has already been confirmed. This paper deals with the influence of the hole by measuring the pressure distribution on the bucket surface and flow visualization in the rotor with stationary Svonius rotor. Stagnation area near the rotation axis was sucked out in the advancing bucket and also the flow over the rotor flowed into the rotor at the returning bucket were observed. Finally, rotation speed promotion system was confirmed.

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A wind concentrating tower type wind turbine was developed as a propeller type wind turbine without the mechanism to follow the changing wind direction. The purpose of this study is to understand the optimum cowl shape for the accelerate ratio of wind speed. Several type of cowl shape were used for this experiment, e.g. expansion cowl, contraction cowl, double structure composed of inner cowl and outer cowl and single structure. As a result, it was found that the accelerate ratio of expansion cowl is higher than the accelerate ratio of the contraction cowl.

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Some specific wind patterns were detected from the natural wind data measured near a VAWT; the corresponding rotational speed variations of the VAWT were investigated. The rotational speed change width tended to increase with increasing the initial wind speed of each pattern. The rotational speed variation of the VAWT was able to be simulated with about 4 % error by introducing the effective wind speed ratio (EWSR), which was estimated to be 63.4 % for the present study.

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Velocity field measurements were carried out in the wake of a small straight-bladed vertical axis wind turbine (VAWT) by using an ultrasonic anemometer. The measurements of the V and W velocity components showed the downwash and the upwash, which proceeded toward the equator level and merged into the horizontal flow. The counter flow region was observed in the mainstream direction (U component). Expected increase in turbulent intensity caused by the dynamic-stall condition was not observed. Large thrust coefficients estimated from the deficit in the U velocity component suggested that the measured flow field may be highly different from the flow field assumed in the momentum theory.

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In order to overcome the disadvantages of S-VAWT mentioned above, a straight-bladed vertical axis wind turbine with a directed guide vane row has been proposed and tested by the authors. According to previous studies, it was clarified that the performance of the straight-bladed vertical axis turbine can be improved by means of the directed guide vane row. However, field test of the proposed wind turbine has not been carried out so far. In the study, performance of straight-bladed vertical axis wind turbine with a directed guide vane row was investigated experimentally in field. As a result, it has been clarified that the guide vane row is effective equipment for improving the turbine performance and the power coefficient of turbine depends on time interval of control of guide vane row.

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For a couple of years, wind turbines have been attracting attention for the utilization of renewable energy resources. Vertical axis wind turbines (VAWTs) which are one of their types can be operated in wind conditions with rapid change of direction. This paper describes the relationship between performance and design of VAWTs. In this study, using CFD analysis, the flow around the rotor was calculated with different design conditions, which means different relationships between the ratio of blade chord length to rotor radius and the number of blades at fixed solidity. Also, the effects of the change of the design condition on the performance of the VAWT will be discussed.

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To understand unsteady flow phenomena around a body, it is important to measure time-resolved surface pressure distributions with high spatial resolution. Pressure Sensitive Paint (PSP) has a capability of providing high-resolution pressure images. In this study, we propose a new PSP technique to obtain time-resolved surface pressure distributions by using conditional sampling of time-series PSP images. To obtain high SNR data, the high-speed camera images are phase-averaged after image acquisition, using a simultaneously-measured pressure transducer data to detect a phase of each image. This method allows us to obtain high SNR images at arbitrary phase of the periodic phenomena using a simplify measurement system and image processing. The effectiveness of the present method was evaluated by applying it to a 3-D square cylinder in low-speed wind tunnel testing. As a result of this experiment, we could obtain time-resolved unsteady pressure images around the square cylinder caused by periodic vortex shedding.

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Recently, measurement method using pressure sensitive paint (PSP) and temperature sensitive paint (TSP) is attractive in measurement of pressure and temperature field on surfaces. However, PSP has temperature dependence as well as pressure sensitivity. Temperature dependence will be the factor which brings an error in pressure measurement using PSP, so temperature correction is needed to obtain the highly precise pressure distribution. So, in this research we apply use the combined method using both PSP and TSP by stacking PSP and TSP layer up. Using the combined method, the temperature distribution obtained by TSP can be used for the temperature compensation of PSP. We call this combined method as "Dual-layer PSP/TSP". In this research, we clarified that the sensitivity of the dual-layer PSP/TSP in low-speed flow fields against pressure and temperature is comparable to that of mono-layer PSP or TSP, showing the feasibility of the dual-layer PSP/TSP for the measurement in low-speed flow fields.

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It is important to understand the behavior of oxygen concentration distribution inside micro-channels for the improvement of micro devices or fuel cells. Most of oxygen sensors such as galvanic or polaro-graphic type cannot be used for unsteady measurements in a small system because of their long response time and large probe heads. We focused on pressure sensitive paint (PSP) for the measurement of the oxygen concentration dissolved in the water in a small system. Up to the present, the PSP techniques have been mainly applied to gas-flows. However, the PSP technique is based on the oxygen quenching of luminescent molecules and would be used in both gas and liquid-flows. In this paper, we investigated the oxygen sensitivity of three types of PSP in the water, and selected a suitable polymer for a binder of PSP.

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The molecular tagging velocimetry (MTV) is applied to a supersonic micro jet issuing from the orifice whose diameter is 500um. This velocimetry uses the forth harmonic of the Nd:YAG laser (266nm) as a light source to excite the acetone molecules seeded in the flow. The numerical flow simulation is performed to check the experimental result. As a result, the velocity profile measured by the present MTV system are found to agree with that calculated by the numerical flow simulation.

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In order to clarify the mechanism of aerodynamic sound generation, aerodynamic sound source was measured with a dynamic PIV system. The acoustic analysis that used the time series data of the vortices field and the acoustic analysis that used Howe's vortex theory using by a compact Green's function were carried out. The estimated sound level is in good agreement with experimental measurement data. Although the scattering effect was small at the formation region of Karman vortex, a strong sound source was observed. It revealed that the dynamic PIV is useful tool for evaluation of aerodynamic sound source.

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Effect of the form of a miniature static pressure probe on simultaneous measurements of fluctuating velocity and pressure with hot-wire probes is experimentally investigated. Ten probes with different probe diameters and lengths are tested for their fundamental performance, e.g. the frequency response and the optimal distance between a pressure probe and a hot-wire probe in velocity-pressure measurements. The frequency response depends mainly on the probe diameter and the length from the pressure holes to the sensor and slightly on the length from the tip to the pressure holes, L_1 when the probe diameter is large. The optimal probe distance in combination with hot-wire probes is investigated in a turbulent wake of circular cylinder, and it is found to depend on the probe diameter but not on L_1. However, the significant effect of L_1 is observed in measured distributions of the correlation between the transverse-wise velocity and the static pressure.

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The multi-blade fan is used for an air conditioner widely because of the high flow rates and high pressure as compared to its size. For the permeation of the multi-blade fan, the noise reduction would required as the comfortable air conditioning supplier. The purpose of our development is to decrease the noise of multi-blade fan used for air conditioner. In the present study, we assembled a small pressure sensor on the fan blade directly, and we measured a pressure fluctuation on the blade surface. And we discussed the relations of a pressure fluctuation between the blades and the noise generation. As a result, a remarkable pressure fluctuation was observed before the tongue passage and was able to confirm that pressure fluctuation were different by flow rate.

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This paper discusses the feasibility of multi-wavelength method in image reconstruction of digital holography for particle measurement. In particle measurement based on digital holography, it is the most important for higher accuracy to reduce the elongation of reconstructed particle image along depth direction. An effective technique of multi-wavelength method is proposed in this paper for suppressing the particle image elongation by reconstructing images with some light waves of different wavelengths. Numerical simulations are carried out to check the performance of the proposed technique. The results of numerical simulations show that the elongation of particle image can be much reduced as compared with conventional single-wavelength method. The application results of the present method to air-bubbly flow demonstrate to show the possibility of successful tracking of a lot of tiny air bubbles in a time-series of numerically reconstructed volume.

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In this paper, we report flow dynamics of λDNAs in nanochannels under DC electric fields. λDNAs which are labeled by a fluorescent dye are suspended in an electrolyte solution and injected into nanochannels which have different depths ranging from 330 nm to 650 nm. By applying DC electric field in the nanochannels, λDNAs flow due to electrokinetic phenomena, such as electrophoresis of λDNAs and electroosmosis flows of the electrolyte solution. The experimental results reveal that the velocity of λDNAs decreases as the degree of the confinement increases in the shallower nanochannels. A simple theoretical model to predict the flow velocity of λDNAs is developed by taking into account effects of confinement due to the nanochannels. The model is developed based on Langevin equation which includes forces due to electrophoresis and electroosmosis. The validity of the model is discussed by comparing a coefficient for the degree of the confinement with those experimentally obtained from the electrophoretic mobility and the diffusion coefficient.

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The aim of this study is to investigate the behavior of ions in the axisymmetric jet. The experiment was performed in the flow measurement by hot wire anemometer and the density measurement with an ion counter which was able to measure the number of ions in air. The distribution of the ion density was similar with the velocity profile in the axisymmetric jet. This suggests that the behavior of ions was influenced by fluid force rather than by the coulomb's force.

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In order to analyze high Knudsen number flows, it is important to understand the interactions of gas molecules and solid surfaces. Molecular beams have been used to study these interactions. Properties such as the translational energy and momentum of a molecular beam have been analyzed very well; however, there are very few reports analyzing the rotational energy of diatomic or polyatomic molecular beam experimentally. Resonantly enhanced multi-photon ionization (REMPI) is a spectroscopic technique, which is able to measure molecular internal energy distribution in very low density gas flows. In this study, we have detected and analyzed the rotational energy distribution in a nitrogen molecular beam by 2R+2 REMPI.

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A thixotropy model was developed for the highly loaded and agglomerative suspensions. As the industrial application, this suspension model was applied for the spin coating process to predict the cluster size of PMMA particles. Spin coating process of PMMA particle suspension was experimentally investigated. Comparison of model predictions with experimental results indicated that good correlations between the model prediction for dispersion characteristics and the optical characteristics of coated film were obtained.

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A particle dispersion model calculating local particle agglomeration characteristics of a solid/liquid suspension has been developed. In a model, not only the effects of Brownian and shear agglomerations and shear break-up but also the convective effects by local velocity components in a flow were taken into consideration. With this model, the local agglomeration characteristics in a suspension with various solid fractions were computed for a flow between parallel plates. The present model shows that the high agglomeration causes in a center region of the flow between parallel plates where low shear is added, and that the viscosity becomes high there. From this, it is concluded that the present model leads to a reasonable result on the particle agglomeration characteristics and a promised tool for estimating local particle agglomeration and viscosity characteristics in a flow.

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