Direct numerical simulation (DNS) for a turbulent channel flow is performed by the Vortex in Cell (VIC) method. The Reynolds number based on the friction velocity and the channel half width is 180. The improvements for the VIC method proposed in the prior study are used. Staggaerd grid is employed to ensure the consistency between the discretized equations as well as to prevent the numerical oscillation of the solution. A method correcting the vorticity is used so that the resultant vorticity field satisfies the solenoidal condition. A single-stage calculation method for the convection of vortex element is also utilized to reduce the computational time. The simulated turbulence statistics such as the mean velocity, the turbulence intensity and the Reynolds shear stress are favorably compared with the existing DNS results. The streak structures and the streamwise vortices near the wall are also successfully captured. These computational results demonstrate that the improved VIC method is indeed applicable to the DNS of wall turbulence simulations.

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Pressure-sensitive paint (PSP) is a useful measurement technique to obtain the pressure distribution on a surface, and has been applied to many measurements in wind tunnel testing. The measurement error of PSP has not been discussed in most reports, while the evaluation of the error is very important for quantitative measurements. In this study, we propose the calibration method which enables us to find the defect of PSPs or the failure of the calibration tests easily. Based on the first- and second-order polynomial Stern-Volmer equations, the propagation of error is analyzed. As a result, it is clarified that the experimental values must be fitted by the Stern-Volmer equations with the constraint condition of (p/p_ref, I_ref/I) = (1, 1) at T = T_ref , and the relative error in pressure can be reduced. It is also shown that the error becomes quite large when p/p_ref ≈ -B/2C in the second-order polynomial Stern-Volmer equation. We propose an indicator for the choice of the polynomial order of the Stern-Volmer equation at T/T_ref ≈ 1, p/p_ref ≈ 1.

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When a dragonfly (Pantala flavescens) on a stem in a wind tunnel was flapping in a flapping angle of 3～5° in a head wind with velocity of 1.14 m/s, flows which occurred by flapping were observed using smoke wire method. The flows passed through a forewing at the distance of about 32mm from the root of the forewing and a hind wing. Reynolds number was about 498 (based on a chord length of the forewing). The flapping frequency was 40～50Hz, the amplitude of 3～4mm and the phase difference of flappings between the fore- and hind wings of about 180° by observation of a high-speed video camera. Also, the configuration of the wings of the dragonfly was flexibly changing during the flapping. A street of vortices with two centers or various types of vortex according to the flapping state were observed downstream of the trailing edge of the hind wing. Moreover, the process of formation of each vortex in the street of vortices with two centers was clarified with time sequence. The ratio of vertical distance to horizontal one between each vortex in the street of vortices with two centers was about 0.31.

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To take up the three-dimensional axisymmetric gate slot concerining with the gate slot possessed in hydraulic equipment, such as, a gate valve, the state of cavitation of the gate slot was investigated by Acoustic Emisson (AE) measurement. The relationship between AE energy level and cavitation condition was analyzed by the root-mean-square (RMS) of acoustic wave. Moreover, a new AE parameter "relative accumulated intensity (RAI)" was defined in order to estimate the erosion tendency of cavitation. Combining with the result of impulsive pressure measurement, the relationship between the erosive damage and the high amplitude generation of AE wave is confirmed by using RAI. In consideration of deflector effect, the AE measurement showed that the conical shape installed on the upstream side of gate slot makes the cavitation erosion increased, and the offset shape on the downstream side of gate slot makes the cavitation erosion decreased significantly.

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Laundry wastewater is known to contribute to water pollution, and the need to reduce the amount of detergents used is recognized. Extensive research has focused on the washing effects of micro-bubbles and nano-bubbles, and mechanical work has been found to account for 50% of the washing effect. In the present research, a water/nano-bubble mixture and several types of surfactants were investigated in an alternating flow system. The nano-bubble water achieved a washing rate of about 5% greater than that of ion exchanged water. In addition, nano-bubbles mixed with an aqueous solution of surfactant exhibited a washing rate that depended on the ionization of the surfactant: the mixture of nano-bubbles and anionic surfactant exhibited a washing rate that was 10% higher than that of aqueous anionic surfactant solution without nano-bubbles. As measured by the du Noüy method, the surface tension of nano-bubble water and anionic surfactant/nano-bubble mixtures were lower than that of water and aqueous anionic surfactant solution, respectively. These results provide evidence of an enhanced washing effect for nano-bubble mixtures.

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The noise reduction radiated from a centrifugal compressor with vaned diffuser using hooked and tapered diffuser vane are discussed by experiments and CFD. Most dominant noise of the centrifugal compressor is interaction tone noise between impeller-discharged flow and diffuser leading-edge. Thus, the shape of diffuser leading-edge is important to reduce the noise level of interaction tone noise. In the experiments, the compressor performance by using hooked diffuser vane is deteriorated because of increase of the leakage-flow passing through the hooked portion while the hooked diffusers are able to reduce the noise level effectively. On the other hand, tapered diffuser vanes are able to reduce the noise and to maintain high compressor performance simultaneously. In the CFD, the twin vortices are generated by the leakage-flow passing through the tapered portion and the vortices induce secondary flow near the pressure surface at diffuser leading-edge and suppress the flow separation from the diffuser leading-edge.

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One of the useful ways to measure the effect of the flow control devise is to use the wall-shear stress sensor to measure the wall-shear stress directly. The sensor used in this paper measures the wall-shear stress, which is influenced by the flow control devise. In this paper, the wall-shear stress of the plane shear layer with the plasma synthetic jet actuator (PSJA) is investigated. PSJA is a flow control device composed of electrodes with A.C. signal. The actuator uses electrohydrodynamic (EHD) effect and induces flow around the electrodes. PSJA has great advantage such as miniaturization, maintenance free, and easy to control compared to other actuators. In this paper, the wall-shear stress of plane shear layer in a low-speed turbulent wind tunnel is observed to measure the effect of the PSJA. The results show that the PSJA changes the flow condition of shear layer by accelerating the flow in shear layer. The wall-shear stress reduces and increases according to the displacement of the wall-shear stress sensor and the actuator.

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The authors have been developing Cascaded Multistage Impinging-jet (CAMUI) type hybrid rockets. A CAMUI type hybrid rocket uses a fuel grain consisting of several cylindrical fuel blocks with two ports. To minimize both of c^* loss due to O/F shifting and residual fuel weight after burning, an appropriate design of initial fuel grain shape is necessary. However, obtaining an optimum design of initial grain shape is not easy because there are many design variables influencing one another. To solve this problem, the authors employed Genetic Algorithm (GA) combined with a numerical model forecasting performance history of a CAMUI type motor. GA can acquire an approximate optimum solution for problems with a vast search space in practical time. The numerical model gives c^* loss and residual fuel weight to evaluate the degree of performance of each initial fuel grain shape. A fuel grain design proposed by this method showed residual fuel weight as small as 6.36% of the initial weight and c^* loss less than 1%.

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Furans such as 2-Methylfuran (2-MF) and 2,5-Dimethyulfuran (DMF) are not popular fuels so far. But they can be derived from biomass via sugars and have preferable fuel properties for spark ignition engines. In this work, the effect of furans on knock suppression was investigated. Firstly, auto-ignition delay of 2-MF blend fuel was compared with other biofuel blends such as ethanol and toluene blend known as high octane number fuel by using a rapid compression expansion machine. 2-MF suppressed cool flame reaction most effectively among tested fuels. As the result, auto-ignition delay of 2-MF blend fuel was quite longer than ethanol or toluene blend in spite of the fact that pure 2-MF had lower octane number and higher ignitability. Secondly, the impact of knock suppression was confirmed using a single cylinder research engine. The lower the RON of base fuel was, the higher the blending octane number was, when the base fuel was paraffin mixture.

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Electrofusion of Giant Unilamellar Vesicle (GUV) and living cell is a gentle method to deliver membrane impermeable cryo-/lyo-protective molecules into living cell for cryo-/lyopreservation. In this method, cellular fusion is believed to be triggered by the irreversible electical breakdown of the membrane at contact region. Nevertheless, as the time change of the membrane potential distribution during an electric pulse is still not clear, the length and strength of electric pulse are hardly designed. In this study, the GUV-Jurkat electrofusion ratios under various pulse strength and length were measured. In addition, we calculated the time change of membrane potential distribution of a deformed GUV-Jurkat pair during the electric field application by a finite element method (FEM)-electric field analysis. The measured cellular and GUV's electric properties and a GUV-Jurkat profile were used for the analysis to validate the quantitative calculation results. Both results of experiment and calculation suggested that; 1) GUV-Jurkat should be stretched for the electrofusion, 2) whole contact region of membrane should breakdown at the same time to process electrofusion, 3) after applying an electric field for around 1μsec, membrane potential in contact region becomes homogeneous, 4) after applying an electric field for around 10μsec, membrane potential is relaxed, 5) the irreversible electric breakdown is around 3V.

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The purpose of this study is to elucidate flame propagation behavior under the application of uniform and non-uniform electric fields by using a constant volume vessel. Two electrodes were attached to the ceiling and the bottom of the cubic shaped combustion chamber and electric fields were applied in the direction of the chamber's vertical axis. A Nd:YAG laser was used to apply laser-induced breakdown for igniting the mixture at the center of the combustion chamber. A homogeneous propane-air mixture was supplied at three equivalence ratios of 0.7, 1.0 and 1.5 and ignited under atmospheric pressure and room temperature. Under a uniform electric field, the premixed flame rapidly propagated both upward and downward, forming a cylindrically shaped flame front. The maximum combustion pressure decreased with increasing input voltage because the flame front reached the chamber wall rapidly and the heat loss to electrodes increased. However, the combustion duration was little affected by the input voltage. In a non-uniform electric field, the flame propagation velocity in the downward direction increased. The leftward and rightward flame propagation velocities were almost the same and were slightly larger than those of conventional combustion. Combustion was markedly enhanced when the input voltage was larger than 12 kV because a brush corona discharge occurs and intense turbulence was generated at the flame front. This indicated that both the electrical potential and corona wind affected combustion. The brush corona discharge caused by a non-uniform electric field enhanced combustion, and the enhancement effect was clearly seen for both lean and rich mixtures.

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