Lubrication by an extremely thin liquid film has become very important in micro machines, magnetic storage devices and so on. When the thickness of lubricant film is thinned to several nanometers, conventional theories of lubrication cannot be used any more. Molecular dynamics simulation was carried out in the present study to investigate the characteristics of the thin lubricant film confined between solid walls. The model used in this simulation is composed of two solid walls and fluorocarbon polymer lubricant confined between them. One of the walls is moving at constant velocity to shear the film. As a result, the lubricant film forms the adsorbed layers near thewalls and the quasi-fluid layer between them. Under a high shear velocity, the slip occuers between the adsorbed layer and the wall and between the adsorbed layer and the quasi-fluid layer. The orientation of molecule influences the occurrence of this slip.

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A particle method for the diffusion of matter in free turbulent flow is applied to the calculation in a plane mixing layer. The flow field is simulated by a vortex method, and the diffusion of matter is calculated through a method analogous to the vortex method. The numerical result demonstrates that the particle method can indeed simulate the entrainment of matter into the shear layer due to the rotating motion of the large-scale eddies. The calculated mean concentration and fluctuation intensity indicate the self-similarities in accordance with the existing numerical results. It is also shown that the mixing asymmetry due to the large-scale eddies is successfully simulated.

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The objective of this study is to clarify the effect of different thermal wall boundary conditions on turbulence statistics and structures in the compressible turbulent flow. We performed direct numerical simulation (DNS) of the compressible turbulent channel flow between isothermal walls with temperature difference (Case C1). The DNS data was compared with that of the compressible turbulent channel flow between adiabatic and isothermal walls (Case C2), and that of the incompressible turbulent channel flow between isothermal walls with temperature difference (Case I). The main results are as follows : (1) The mean velocity in the logarithmic region and the maximum of the RMS streamwise velocity fluctuation in wall units are smaller than those of Case I near the high temperature isothermal wall, while they are larger than those of Case I near the adiabatic wall. (2) Near the high temperature isothermal wall, the mean temperature profile has an additional maximum due to the friction work, and the RMS temperature fluctuation has the corresponding maximum. This is consistent with the fact the production term of temperature variance has the additional maximum in the region very close to the high temperature isothermal wall. (3) The correlation coefficient between streamwise velocity and temperature fluctuations of Case C1 is significantly different from those of Cases C2 and I in the region very close to the high temperature wall. (4) The direction of energy transfer due to pressure work near the high temperature isothermal wall is the same as that of near the adiabatic wall. (5) The compressible terms of the temperature variance transport equation are not negligible near the low temperature isothermal wall.

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A new calculation method of flowfield around supersonic/hypersonic vehicles is developed based on the finite element method (FEM) scheme. In the case of general simulations by the FEM, the pressure P is expressed by a differential form, and therefore, there occurs a considerable discrepancy. Moreover, it is generally said that the memories and the speed of the calculations are worse than the finite differential method (FDM). However, in this study, the pressure term is included in the flux vector expressing by the stress tensor. By this treatment, the pressure term can be expressed as a non-differential form by applying the weighted residual method. From this method, the flowfield around a supersonic/hypersonic vehicles can be successfully calculated with high speed, little discrepancies, and stability. The propriety of our method was examined by comparing the numerical results with the one of experiments obtained by the schlieren method and the electric discharge method. The comparisons were carried out under the conditions that the Mach number was 10, and a wedge model and a re-entry capsule were used to compare. From these comparisons, it was found that the calculated shock shapes and streamlines were in good agreement with the experimental results.

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Bouncing and coalescence between single rising bubble and free surface were experimentally and numerically studied. In experimental study, with Weber number of O (10^-2) -1.7 and Morton number of O (10^-9) -O (10^-4), it was observed that both liquid viscosity and bubble diameter are playing the dominant role in coalescence time and bounce/coalescence condition. It was clarified that Weber number is the important parameter in the coalescence time of bubble with free surface in low viscosity liquid. However, in high viscosity liquid, scale of coalescence time was observed significantly different from the one of low viscosity liquid. In numerical study, the full Navier-Stokes equation was solved, by defining two Level Set functions for bubble and free surface respectively. The pressure of liquid film between bubble and free surface, bouncing mechanism and difference of coalescence time scales are discussed.

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A ring-type obstacle, which simulated a spacer in a light water reactor or a flow obstruction supporting heat exchanger tube, was set in an upward air-water two-phase flow in a vertical tube to investigate the effects of the obstacle on liquid film thickness in relation to the drypatch generation. We measured simultaneously the time varying liquid film thickness at several axially different locations near the obstacle under the conditions of the superficial water velocity ranging from 0.06 m/s to 0.4 m/s and the superficial air velocity from 0.5 m/s to 36 m/s and discussed the effects of the opening area ratio of the obstacle on the liquid film thickness. The results are summarized as follows : (1) The minimum film thickness near the obstacle becomes thinner as the clearance between the obstacle and the inner surface of tube becomes smaller. (2) The obstacle makes the disturbance wave smooth and it makes the base film thick downstream of the obstacle when the clearance is small.

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A three-dimensional one-way bubble tracking method is one of the most promising numerical methods for the prediction of a developing bubble flow in a vertical pipe, provided that several constitutive models are prepared. In this study, a bubble shape, an equation of bubble motion, a liquid velocity profile, a pressure field, turbulent fluctuation and bubble coalescence are modeled based on available knowledge on bubble dynamics. Bubble shapes are classified into four types in terms of bubble equivalent diameter. A wake velocity model is introduced to simulate approaching process among bubbles due to wake entrainment. Bubble coalescence is treated as a stochastic phenomenon with the aid of coalescence probabilities that depend on the sizes of two interacting bubbles. The proposed method can predict time-spatial evolution of flow pattern in a developing bubble-slug flow.

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The verification of the three-dimensional one-way bubble tracking method (BTM) proposed in our previous report is carried out through the comparisons between measured and predicted developing bubble-slug flows in a vertical pipe. The approaching process of two large bubbles in various liquid flow conditions is well predicted by a wake field model implemented in BTM. Good predictions are also obtained for the spatial evolutions of flow patterns, mean void fractions, void fluctuations, radial void profiles, mean pressure drops and pressure drop fluctuations under stagnant, laminar and turbulent flow conditions, provided that the bubble coalescence probability between two small bubbles and the inlet distributions of bubble size and bubble position are appropriately given.

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In order to improve the reliability of two-phase flow characterization by correlation dimension, several estimation methods are tested and their reliabilities are evaluated. The estimation procedure of the correlation dimension involves following steps : attractor reconstruction and fractal dimension estimation. There are many improvements for each step. However, they have been individually proposed and have not used simultaneously. Using numerically obtained quasiperiodic time series, we evaluate their combinations. Analysis results show that a point correlation dimension method with constant time window reconstruction is more reliable than the widely used Grassberger-Proccacia method with constant delay time reconstruction for ill-conditioned time series : data size is small and dimension is high. The estimation using experimentally obtained noisy chaotic pressure fluctuation time series also shows similar results, so we believe that the proposed procedure is reliable for various kind of time series.

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In a therapeutic ultrasound field, cavitation frequently forms a bubble cloud that consists of many microbubbles. A method to control the violent collapse of cloud cavitation is being developed. It is comprised of two frequency ultrasound forcing. The first is a higher frequency ultrasound waveform that makes cloud cavitation at the surface of the object. The second is a lower frequency waveform that produces a violent collapse of the cloud cavitation. If the phenomena is well controlled in time and space, it can be utilized for the stone crushing mechanism in lithotripsy. From a numerical simulation, the controllability of the cloud cavitation is predicted. A stable bubble cloud at the solid surface and the shock wave from the violent cloud cavitation collapse are observed by using a high-speed photography. The occurrence time of the collapsing phenomena of cloud cavitation is controlled within 100 ns and the area is controlled within several hundreds micrometers. Using the present method, stones are chipped away such that scoop-like indentations are achieved.

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To investigate the effect of inlet flow distortion on cavitation instability, unsteady pressure and blade stress fluctuation were observed in a 3-bladed inducer. The inlet flow distortions were generated by using screens installed upstream of the inducer. In addition, the effect of the frequency of the fluctuation of the angle of attack caused by the inlet flow distortion was examined with three screens. The following results were obtained : (1) The present inlet flow distortions have almost no effect both on the pressure and cavitation performances. (2) The conventional and higher order rotating cavitations were suppressed by the present inlet flow distortion. However, the occurrence of the conventional cavitation surge was enhanced at lower cavitation number. (3) Amplitude of the blade stress fluctuation caused by the inlet flow distortion decreased with increasing of the frequency of the fluctuation of the angle of attack. (4) The phase difference between the blade stress fluctuation due to the inlet flow distortion and the fluctuation of the angle of attack increased as decreasing of the cavitation number.

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The effects of trip wires and a round-rod grid on the reactive-diffusive mechanism in a liquid plane mixing layer with a chemical reaction were experimentally investigated. Instantaneous velocity and concentration were simultaneously measured using the combination of a laser-Doppler velocimeter and a laser-induced fluorescence method. The results show that turbulent mixing and chemical reaction are significantly promoted by installing trip wires and a grid. The amount of chemical product in the mixing layer with a grid is larger than that in the mixing layer with trip wires, despite the same turbulence level of the intensity in the vertical direction around the centerline of the test section in the two flows. The distributions of velocity and concentration statistics in the mixing layer with a grid are fairly symmetric, whereas they are asymmetric in the mixing layer with trip wires. In addition, self similarity is also observed in the mixing layer with a grid.

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While researches to reduce a broadband noise from wind turbine rotor blade had been conducted successfully, a generation mechanism of the noise particularly from around the tip area is yet to be elucidated and thus a further research for the noise reduction is expected. For this purpose, we had developed microphone array systems to evaluate acoustic performances of the 15 m diameter experimental wind turbine rotor blade and conducted the acoustic tests of the blade. Results of the tests revealed that the blade emits strong high frequency broadband noise from its extreme tip and the mid frequency noise from the trailing edge. This result suggests that the generation mechanism of the high frequency noise is believed due to the stream wise vortices shed directly from the extreme tip which is different from results of wind tunnel tests of three dimensional airfoils.

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The flow field in a turbulent jet impinging on a flat plate is studied. When the two dimensional free jet impinges on the wedge object, so called the edge tone is generated. This accompanies a loud noise and coherent motions. Although most attention has been paid to reveal its mechanisms and control the coherent motions in order to reduce the sound noise, we are interested in the effect of coherent motions on the typical length scale. Adopting the three-component analysis, it was found that coherent motion has a great influence on the integral scale and Taylor micro scale, but has little on the Kolmogorov length scale. Also we focus on the area where the coherent motions survive after impinging on the edge of flat plate. By way of conditional sampling procedure, both the periodic component caused by coherent motions and the non-periodic component are analyzed. The periodic component remains close to wall even far from the top of the plate, but the non-periodic component indicates the large values only around the edge.

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In this report we present the experimental study on the instability of the two-fluid Taylor vortex flow with a small aspect ratio. The immiscible two fluids between annulus construct with upper positioned silicon oil and lower positioned aqueous solution of glycerol. Water glycerin is on a bottom solid surface and with a top free surface as a boundary condition. On the other hand silicon oil is with two free surfaces on the bottom and top surfaces. The instability of the Taylor vortex flow with the immiscible two fluids is assumed to being influenced by the boundary surface between them. This experimental study shows the pictures of sectional flows and clarifies the configuration of the vortices. The variation of the cell heights with increasing Reynolds number is shown. The instability for wavy Taylor vortex flow is clarified. Finally the routes of the bifurcation between secondary modes and/or between a primary mode and secondary mode are shown and the relationship of the instability of the two-fluid Taylor vortex flow is discussed.

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We propose a method of three dimensional curvature analysis for the rotor surface of screw compressors. By applying this method, we can calculate a normal curvature, that is perpendicular to a sealing line. Such a curvature is required to calculate internal leak flow and contact stress between rotors. Internal leaks reduce compressor efficiency, and contact stress is an important parameter for inspecting the reliability of a rotor's surface strength. The leak flow for each cross section is computed by cubic interpolated propagation (CIP), a type of numerical fluid dynamics. Our results show that when a sealing line gap is uniformly 50 μm and the fluid is compressed air, the curvature difference on the sealing line doubles leak flow. The total leak flow of the trailing side leak is 2.5 times that of the leading side.

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This paper presents an active flow control using synthetic jets with fluidic nozzle. The control system is composed of particle tracking velocimetry (PTV), neural network computing and Pyragas delayed feedback control theory. Synthetic jets are set on both side of primary flow, and connected to fluidic nozzle. The actuators can easily vector a primary flow upward or downward by synthesizing suction and blowing actions. This system is applied to water flow with free surface in a rectangular tank having an inlet on the right side wall and outlet at the bottom. Two flow patterns are found to be stable in this tank. Under one condition, inlet flow goes directly to outlet and clockwise circulating flow is observed. Under the other one, while, inlet flow is attached to free surface, resulting in counterclockwise circulating flow. Any other flow pattern is unstable and stabilized to either two stable ones. A target flow pattern is stabilized by the present system although it is naturally unstable.

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This paper presents a new method, namely pseudo-viscosity particle model for numerical simulation on flow control using plasma synthetic jet actuator (PSJA). Using the method, effect of PSJA is added to Navier-Stokes equation as an appearance viscosity in addition to turbulent eddy viscosity computed from LES, and its influence is traced as Lagrangian particles start from position of PSJA. The appearance viscosity caused PSJA is named pseudo-viscosity. Result of simulation using our model is compared with experimental result about a flow around NACA0012 airfoil with PSJA when angle of attack is 0 and 7 degrees, and agreed qualitatively on profile of streamwise velocity defect on wake. We also suggest there is some possibility that PSJA reduce effect of turbulent eddy viscosity.

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In the present paper, the experimental and numerical investigations are performed to clarify the mechanism of the side load in the 2 D dual bell nozzles using two types of nozzle models. In the experiments, the flow field was visualized by the schlieren method and asymmetric one-side-attached jet patterns were observed. The asymmetric flow field produced the asymmetric wall pressure distributions, resulting in the side load occurrence. The numerical simulations show that the jet oscillations result in the asymmetric jet patterns. The jet oscillations are induced by the alternate vortex shedding from the shear layer between the jet and the atmosphere, resulting in the asymmetric movements of the separation points on the 2 nd nozzle surfaces.

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We clarified the effect of the gas-phase film on the fall velocity of a highly water-repellent sphere in Newtonian fluids. Experiments were carried out for the measurements of physical properties of the gas-liquid interface and the fall velocity by the falling sphere method in the Reynolds number range of 93.2<Re<10032. The thicknesses of the gas-phase films around the sphere were about 61-91μm. The terminal velocity of the highly water-repellent sphere decreased more than that of the normal smooth sphere and the maximum drag reduction ratio was 14.6% for the highly water-repellent surface at Re=93.2.

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The liquid in a capillary pipe with a closed upper end falls spontaneously when the pipe is inclined by a certain critical angle from the vertical direction. A theoretical investigation was conducted to analyze the unstable phenomenon from a thermodynamic viewpoint. The system energy is calculated by considering the potential energy and the surface energy of the three-dimensional liquid meniscus formed under the pipe end, and the energy change due to wetting between liquid and solid surface. The system becomes unstable if the energy change is negative when the attaching point of meniscus is displaced by infinitesimal distance. The critical angle of pipe inclination is obtained by the above condition based on an approximate solution for the three-dimensional meniscus profile. The results agree with those obtained by experiment using glass and Teflon pipes for various test liquids.

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Numerical analyses were performed for the effect of local inner heating on the mixing flow in a horizontal square duct. Three-dimensional governing equations were solved for Re=100, Pr=0.72 and six kinds of inner heating sizes in a duct, with insulated walls or uniform temperature walls. Local inner heating induced the local buoyancy force and produced four recirculating flows across a section in a thermally insulated duct. In a horizontal square duct with uniform wall temperature, the interaction of the buoyancy induced flows by temperature difference between the fluid and the local inner heating and between the fluid and the walls reduced the maximum intensity of the secondary flow. Two recirculating flows were generated in a downward region. Heat transfer was locally enhanced or depressed corresponding to the flow situation.

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Thermocapillary convection in a liquid bridge is induced by non-uniform surface tension distribution over the free surface owing to a temperature difference between two cylindrical rods sustaining the liquid bridge. The induced flow is usually visualized by using fine particles as tracers. Under certain flow conditions, the tracer particles were found to form particle accumulation structures (PAS). Four types of PAS were found in different flow fields. The conditions for the occurrence of PAS were investigated carefully with focusing on the Twisted String PAS (TS-PAS) in which the particles gathered along a closed single path. Various particles were employed as tracers. Most of the tested particles were accumulated on the orbit of the TS-PAS independently of their diameter, density and material. The TS-PAS exhibited several types of closed path lines. In the present study, the relation between the TS-PAS and the flow field was revealed. The flow field itself exhibited the structure quite similar to the TS-PAS and the particle followed the flow field. Thus, the particle-particle and the particle-flow interaction were not a dominant factor to form the TS-PAS.

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In this study, investigation of the turbulent structures and heat transfer across the air-liquid interface was conducted by DNS data of wind-driven turbulent flow. The streamwise dynamic process, which was the interaction between coherent turbulent structures in gas layer and large horizontal scale shaped the water surface waves, dominated momentum and heat transfer across the air-liquid interface. On the other hand, wall-normal transfer was inactive under the vertical turbulent restraint effects of the water surfaces similar with the turbulent open-channel flows at low Froude number on the turbulent motion. Thermal boundary condition was almost constant temperature condition at the air-liquid interface, because temperature fluctuations were caused from surface waves as well as wall-normal turbulent intensity.

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The conventional boundary element method (BEM) uses internal cells for the domain integrals, when nonlinear problems or problems with domain effects are solved. In the conventional BEM, however, the merit of the BEM, which is easy preparation of data, is lost. This paper presents numerical integration for a meshless BEM, which does not require the internal cells. This method uses arbitrary internal points instead of internal cells. In this paper, a three-dimensional interpolation method is proposed. Furthermore, three-dimensional numerical integration is proposed using the above three-dimensional interpolation method. This method is based on an improved multiple-reciprocity BEM (triple-reciprocity BEM) for heat conduction analysis with heat generation. In order to investigate the efficiency of this method, several numerical examples are given.

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Design-point and part-load characteristics of a gas turbine-solid oxide fuel cell hybrid micro generation system, of which total power output is 30 kW, are investigated for its prospective use in the small distributed energy systems. A cycle analysis of the hybrid system has been performed to obtain general strategies of highly efficient operation and control. The method of analysis has been verified by comparison with previous results, of which power output was assumed in the range from 259 to 519 kW. Then, the part-load performance of the 30 kW system has been evaluated. Two typical operation modes, i.e., constant and variable rotation speed gas turbine operation, are considered. It is found that the variable speed mode is more advantageous to avoid performance degradation under part-load conditions. Operating under this mode, despite 10% adiabatic efficiency drop in the gas turbine components, the generation efficiency can be maintained over 60% (LHV) in the power output range from 40 to 100%. The turbine exhaust temperature, however, is increased with decreasing the power output under the variable speed mode with the constant SOFC operating temperature, so that the thermal durability of recuperator material becomes a critical issue. Finally, the effect of compressor/turbine operating lines on the system performance is evaluated.

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The chromosome model showing system operation pattern is applied to SGA (simple genetic algorithm), and the method of optimization operation planning of energy system is developed. The optimization method of this operation planning was applied to the compound system of methanol steam reforming type fuel cell, geothermal heat pump and the electrolysis tank of water. The operation planning was performed for the energy system using the energy demand pattern of the individual residence of Sapporo city. From analysis results, the amount of outputs of a solar module and the relation of the operation cost of the system which are changed by the weather were clarified. The representation day in February of the ratio of the operation cost in case of (0% of output rates) the rainy weather to the time of fine weather (100% of output rates) is 1.12. And the representation day in July is 1.71. Furthermore, the optimal capacity of accumulation-of-electricity and thermal storage was estimated, and they are 308 MJ and 23 MJ, respectively.

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A low emission pre-vaporization pre-mixing lean (PPL) combustor for a 100 kW automotive ceramic gas turbine (CGT) has been developed to meet the Japanese 10-15 mode regulations without after treatment such as catalysts. Emission characteristics of the combustor on a test bench, and installed in the engine were obtained under steady state and transient conditions. Transient NO_x characteristics were dominated by the primary air ratio in the same manner as the steady state NO_x characteristics. Empirical equations for NO_x and CO characteristics were proposed for the PPL combustor. NO_x, CO and THC emissions for the Japanese 10-15 mode were predicted, and all of them fully satisfied the emission targets.

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Opposed flame spreading over ETFE (ethylene-tetrafluoroethylene co-polymer) insulated wire, which is used for actual wire in space, in low air flow velocity has been investigated under microgravity environment. The experiments were performed with Japan Microgravity Center (JAMIC) 10 s dropshaft and NASA's KC 135 parabolic flight. Experiments were performed with changing O₂ concentration, 35 and 40%, external air flow velocity, 0 (quiescent) -22 cm/s and dilution gas, N₂, CO₂, He. The sample of 0.32 mm inner core diameter with 0.15 mm insulation thickness was used. The results showed that flame spread rate over wire insulation was strongly affected by air flow velocity and the dilution gases. Flame spread with N₂ dilution had maximum value in a low flow velocity region. However, CO₂ dilution resulted in monotonic increase in flame spread rate with decrease in air flow velocity and the maximum flame spread at V_e=0 cm/s (quiescent). The different dependency of the spread rate on flow velocity with different dilution gas was explained by the reabsorption effect of CO₂ gas ahead of flame front. Reabsorption of radiation heat with CO₂ gas recovers the radiation heat from the flame and prevent the flame temperature decrease even in very low flow velocity region, which is known as radiation control region for optically thin gas.

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In this paper, separation of laser-induced fluorescence (LIF) due to PAHs and incandescence (LII) due to soot by time-resolved measurement was demonstrated for the propane diffusion flame. Laser-induced fluorescence method for the measurement of polycyclic aromatic hydrocarbons (PAHs) in diffusion flame was developed. A KrF excimer laser was used for excite the PAHs. Strong laser-induced incandescence due to soot was appeared with fluorescence signal due to PAHs. In order to separate the signals into LII and the PAHs-LIF detected from diffusion flame, time-resolved measurement was carried out. A pico-second gate CCD camera with a image intensifier was used taking a time-resolved image. From the two different images, which were taken at different time-delay, PAHs-LIF and LII were obtained. Intensity distributions of PAHs-LIF and LII were measured on the flame axis. Overlap region of the LIF and LII was observed around the onset position of the yellow flame. In this region, LIF intensity decreased and LII intensity increased along the flow direction. It seemed that this region was transition region from the PAHs to soot and was attributed the presence of soot precursor.

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Perfluorocarbons (PFCs) and hydrofluorocarbons (HFCs), are being regulated internationally because their gases cause green effect and their global warming potential (GWP) are several thousands times higher compared with that of CO₂. PFC is used as wafer etching and clean-up agent of chemical vapor deposition (CVD) chambers. CF₄ is one of the most stable gas among PFCs and their decomposition is extremely difficult. Low pressure (-80Pa) inductive coupled plasma (ICP) reactor was used to investigate the CF₄ decomposition. The reason we took this approach was to utilize the ICP power supply for generating remote plasma in both wafer etching process and chamber cleaning at the same time. When the total flow rate was below 0.189 L/min, the complete CF₄ decomposition was achieved for a given power (1.2 kW). The optimum O₂ addition was in the range of 1.0-1.45 stoichiometric ratio of CF₄. Argon addition enhanced the CF₄ decomposition significantly. But, helium addition was insignificant.

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In this study, firstly it was demonstrated that the absorption of NO₂ by condensed water in the sampling system might lead to considerable errors in the measurement of NO_x for combustion gases containing relatively high concentration of NO₂. Secondly, the loss of NO₂ into water was systematically measured using bubblers in series or an NO₂ absorption tube (a horizontal tube partly full of water). NO₂/air mixtures were passed through the bubblers or the NO₂ absorption tube and then analyzed by a chemiluminescent NO_x analyzer. The initial NO₂ concentration and water temperature were varied in the ranges 20-300 ppm and 0-30°C, respectively. The ratio of the decrease in the concentration of NO₂ to the initial value Δ [NO₂] / [NO₂] ₀ is found to be proportional to the surface area of water and inversely proportional to the volume flow rate of the mixture but practically independent of the residence time in the NO₂ absorption tube. Also, Δ [NO₂] / [NO₂] ₀, gradually increases with increasing the initial concentration of NO₂ but it is independent of those of NO and O₂. The temperature dependence of Δ [NO₂] / [NO₂] ₀ is found to be negative and of an Arrhenius relationship. The species balance between the gaseous and liquid phases was also verified. Finally, based on a simple model and the present experimental data, an equation for estimating the magnitude of the loss of NO₂ was developed.

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It is expected to manufacture new materials under the micro-gravity environment. Under the micro-gravity environment, holding technology of molten metal is important to manufacture new materials. In the present study, the technology to handle the material in space by the ultrasonic wave is developed. However, it is difficult to hold a high temperature object by ultrasonic standing wave due to temperature gradient. Moreover, it is also important to measure the physical properties of the material by non-contacting. Therefore the followings are the purposes of present study. At first, the characteristics of droplets holding by the ultrasonic standing wave under normal gravity environment is investigated. Secondly, the surface tension of the droplet is estimated by measuring surface oscillation. Thirdly, the viscous coefficient of liquid droplet is calculated by the damping constant of the droplet. Finally, numerical calculation is conducted to clarity the characteristics of the high temperature object holding in space.

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At first, the accuracy of the scattering patterns predicted for typical examples by a direct finite-difference solution technique was examined by comparing them with the analytical solutions. Comparisons with regard to the scattering patters formed by a single cylinder, a pair of cylinders or a single true sphere showed good agreement. Based on this confirmation of accuracy of the direct finite-difference solution method, the influence of multiple-scattering and three-dimensionality of scatterer on the diffraction was discussed. Even if the volume fraction of particles is same, larger number density of scatterers leads to more remarkable distortion of scattering pattern and subsequent erroneous measurement of particle size distribution. When a cylindrical scatterer is long in the direction of optical axis, its scattering pattern is remarkably different from that formed by a true sphere of the same diameter. That is, the diffraction pattern is affected by the three-dimensionality of scatterer.

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Laser Doppler Velocimeter (LDV) is one of the most useful method to measure the flow velocity of fluid flow such as swirl velocity in an engine. The laser as the light source of LDV has been usually used high power gas laser because of the weak scattering light from particles as in case of back scattered LDV system or loss of light through the optical fibers. In recent years, laser diode of rather high power output and holding coherency was developed. Suggestion of using laser diode as the light source of LDV was shown, but the ability of its utility has not been clearly examined. In this paper, laser diode was examined to use the light source of LDV and was confirmed to be valid when it was correctly controlled. As the proof of validity of laser diode system, measured examples of mean velocity and turbulence intensity were shown in an engine.

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A swirling flow and rich fuel concentration near the center were produced in a vessel by tangentially charging air and fuel injection. Propane was used as fuel. Fuel concentration distribution was measured with laser induced fluorescence (LIF) method using acetone as a tracer. It was confirmed that the center-rich stratified fuel concentration was produced. In order to estimate the pattern of the fuel concentration field, the Gaussian fitting method was applied to the equivalence ratio profile. Fuel distribution history obtained from LIF measurement agreed with the calculation result using axisymmetric diffusion equation. The initial stage of combustion was greatly affected by the fuel concentration distribution in the vicinity of the spark location. The stronger turbulence intensity accelerated combustion and main combustion became shorter under the same fuel distribution conditions.

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The effects of mixture equivalence ratio on knock in SI engines were investigated by a numerical simulation using the Lievengood-Wu integral in combination with a detailed chemical kinetic model of n-butane. This method could save the time-consuming of predicting knock and good validations were achieved on various operating conditions of a SI engine. The results showed that lean mixture did not always suppress knock in engines because the knock tendency depended not only on equivalence ratio but also on the pressure and temperature history of the unburned mixture.

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It is necessary to elucidate the noise generating mechanism for reducing engine noise. In a running engine, various impacts in the engine cause excitation sources for structural vibrations and engine noises. Engine noises are classified into the combustion noise, the combustion induced mechanical noise, and the mechanical noise depending on their excitation source. However, it is difficult to measure such noises separately because some impacts generate closely together in time and space. In order to separate the combustion noise from the total engine noise, a transient noise generation model that considers the vibration transmission and the damping effect of the engine structure was proposed. The newly proposed model was verified by conducting the single explosion excitation experiment of a stationary engine. In addition, it was clarified that the time histories of the combustion noise of both gasoline and diesel engines could be estimated at firing condition.

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