The interaction between a shock wave and an air bubble attached to a gelatine wall was experimentally and numerically investigated to elucidate the mechanism of tissue damage caused by bubble collapse. The gelatine concentration was varied between 10 and 30% by weight. It is shown by means of highspeed photography that a shock wave of strength 0.45 MPa causes 0.3∼1.8 mm diameter bubbles to produce high velocity liquid microjets with penetration depths of approximately 0.5 ∼1.0 times the initial bubble diameter. Our results show that bubbles collapse violently in response to sudden changes in the ambient pressure generating high pressure and high temperature. Tissue damage due to bubble collapse is caused by the combination of impact and impulsive pressure and thermal effects.

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Application of a new finite element method to the two-dimensional square cavity flow of incompressible viscous fluid is discussed for the high Reynolds number regions. The finite element method is developed with the Petrov-Galerkin procedure using exponential-type test functions. The incompressible Navier-Stokes equations are discretized by means of a semi-explicit scheme in which velocity is treated explicitly and pressure is treated implicitly with respect to time variable. As the time-marching scheme, the fractional step method is used effectively in this study. The validity of the method is shown for unsteady flow with Re=10³-10⁴ through comparison with other existing numerical solutions. For unsteady flow at Re=10⁵ it is observed that the flow in a cavity is very complex using numerical results and simulation of the results.

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This paper deals with an experimental study on the unsteady performance in cylindrical choke of the oil hydraulic equipment. Experiments are performed under unsteady flow in which the outlet pressure P₂ of the cylindrical choke takes the form of a trapezoid varying with time, keeping the inlet pressure p₁ constant. It is found that as the absolute values of the rates of pressure change dp₂/dt increase, the incipient cavitation number k_ci shows a tendency to decrease, and the desinent one, k_cd, shows a tendency to increase with three geometric parameters : diameter, length and chamfered length of the choke. The values of k_ci, and k_cd with the chamfered length of chokes are smaller than those with the sharp edge of chokes for various dp₂/dt. As the larger absolute values o dp₂/dt further increase, the hysteresis between k_ci and k_cd becomes larger for each combination of the cylindrical choke.

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This paper deals numerically with nonlinear oscillations of spherical bubbles in a sound field. Governing equations of a cluster of interacting spherical bubbles are obtained by taking account of the compressibility of a liquid. These equations contain previous results for both single bubble and two bubbles as special cases. Bifurcation diagrams are computed for typical configurations of bubbles. It is shown that the bifurcation structure of bubbles which oscillate with the same phase in a sound field is similar to the structure of an isolated bubble driven by a higher frequency than that of the sound field. When bubbles with different initial radii oscillate, the independent oscillation of each bubble is suppressed by the interaction and the bubbles take on a collective behavior.

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Force measurements were conducted to obtain the basic data for the engineering practice of drag-reducing, which utilizes microbubble injection with two elliptic cylinders with slenderness ratios of 1/8 and 1/3 and a circular cylinder. Air was injected through a porous section flush-mounted on the surface of the test body in the neighborhood of the nose so as to form microbubbles. It was found that the drag increased unexpectedly due to the injection of the microbubbles, and it increased steadily with an increase in the airflow rate. The reason for the increase was supported by numerical analysis based on bubble dynamics.

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The steady motion of a spherically eccentric encapsulated liquid drop in an immiscible liquid was studied numerically for Reynolds numbers up to 200. An encapsulated drop consisting of a gas bubble completely coated by a thin liquid film was subject to the present research. Based on the experimental observations of the encapsulated drop motion obtained using liquid-liquid-gas systems developed by the authors, a model of the configuration and a numerical method for solution for the flow field were presented in the limit of large interface tensions by assuming two interfaces to be spherical. The development of the numerical code was based on the finite difference technique and the curvilinear coordinate transformation technique. The flows around and inside the encapsulated drop for a spherically eccentric configuration were investigated. Furthermore, the effect of eccentricity between the inner and outer interfaces on the drag coefficient or on the flow patterns of the encapsulated drop moving at finite Reynolds numbers was elucidated quantitatively.

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Viscous couplings, which are mainly used in the power train of four-wheel-drive vehicles, normally operate in the viscous mode, where torque is transmitted by viscous shearing force between sets of disks alternately coupled to the input and output. Under an extreme condition, in which relative speed between the disks is largely increased, two disks come into contact with each other, resulting in a torque amplification called the hump mode. Although some theoretical and experimental studies have been made to explain the hump phenomenon, they seemed to be inadequate. In this paper the effects of the camber of the inner disk blade on the hump phenomenon were examined by means of numerical calculations. A slight camber of the disk was found to cause considerable torsional moment on the blades, resulting in an increase of the attack angle of the blade and axial thrust on the inner disk.

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Concerning the vortex shedder used in the Karman vortex flowmeter, the flow resistances of cylindrical bodies having various cross sections in a circular pipe are given by the general equation in the previous paper. In the present paper, it is confirmed that the equation holds for the vortex shedder having a large blockage ratio. Then, the same idea is applied to the hydraulic losses of flow control components asymmetrical to the cross section of the pipe, such as a slice valve, a butterfly valve and a cock. Consequently, these hydraulic losses hitherto given by a chart or a table are given the following general equation : ζ=C[(1-β)/β²]ⁿ, where β is the open ratio.

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Analogy between the developing laminar flows in a curved pipe and in an orthogonally rotating pipe is discussed. Two governing parameters and the nondimensional axial distance Z are properly obtained for the respective flows. When the second parameters become large, it is shown that flow patterns, friction factors and flow characteristics become very similar for the same values of governing parameters if they are correlated with Z.

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When a coiled pipe rotates about the coil axis, the effect of rotation interacts with centrifugal and viscous effects to complicate the flow characteristics beyond those seen in stationary curved ducts. Fundamental characteristics are given for fully developed laminar flows by similarity consideration and by numerical computation. An empirical formula is presented for the friction factor.

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A numerical analysis has been performed on fully developed turbulent flow in a square duct with two roughened facing walls using an algebraic stress model. The calculated results where compared with the experimental date and other published numerical results. In a smooth duct, as is well known, a pair of vortices is observed in a quadrant of the duct cross section. In this rough duct, however, both the present method and the experiment indicated formation of only one vortex in a quadrant. Moreover, the present method can predict more accurately the location of the center of secondary flow than other numerical methods. The calculated results of the distributions of normal stresses and turbulent energy are in reasonably good agreement with the experimental data. However, the different sign region of the shear stress, which is generated by the secondary flow of the second kind, is not shown in the present calculated results.

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Experimental and numerical studies of turbulent flow in a non-circular duct with a rough wall are very scarce. Therefore, numerical analysis has been carried out in this study for fully developed turbulent flow in a square duct with a roughened wall using the Reynolds stress model. Calculated results are compared with the experimental data available. The present method can predict well a large eddy caused by the secondary flow of the second kind in a half cross section and a small eddy is observed in the upper wall corner region. However, a small eddy which appeared in the calculated results is not recognized in the experimental data. Calculated results of normal stresses and turbulent energy are in comparatively good agreement with the experimental data. These examinations suggest that the present method utilizing the Reynolds stress model, which is classified by an anisotropic turbulent model of high Reynolds number, is able to predict the turbulent flow in a square duct with roughened walls.

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The two-dimensional velocity and shear stress distributions of the uniform and laminar flow in a rectangular open channel were obtained analytically, and the manner in which their distributions were varied by the aspect ratio (channel width/water depth) was examined. As a result, it was shown that when the values of discharge were calculated using one-dimensional formulas, the calculation error became more than l0% in the case where aspect ratio was less than 14.

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With the rapid progress of technology in supercomputers and numerical analysis, it became possible to apply these technologies to complex flow phenomena in turbomachinery not only for research but also as design tools in industries. To catch up with this trend, we have developed a 3-dimensional NS (Navier-Stokes) numerical analysis cord for turbomachinery based on the outer flow cord for aircrafts (the Reynolds averaged Navier-Stokes equations are solved using an implicit finite-volume TVD upwind scheme with a 2-equation turbulence model). Verification by experiment is indispensable for all numerical cords, but there are not sufficient reliable experimental data, especially for the 3-dimensional case. So, we first conducted 2-dimensional compressor cascade tests with solid side walls, measured their 3-dimensional flow patterns, then compared 3-dimensional viscous flow analysis with the test data. The computed results show good agreement with experimental data, such as blade surface static pressure distribution, total pressure loss distribution at outlet of cascade, and pitchwise-averaged exit flow angle distribution under design conditions. As for higher inlet Mach number conditions, computed results show good agreement with experimental data qualitatively, but a slight quantitative discrepancy remains.

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Turbulence measurement was carried out in the self-preserving region of an axisymmetric free jet with the aid of the three-dimensional particle tracking velocimeter. Approximately 420 instantaneous velocity vectors on average were acquired from each of 126000 TV fields. The self-similarity and axisymmetry of turbulence statistics distributions are confirmed. The power-law requirements are fulfilled for the streamwise evolutions of the mean centerline velocity and the velocity half width. Detailed radial distributions of the turbulent statistics are obtained, which include mean velocities and all the one-point velocity correlations up to the fourth-order. Skewness and flatness factors of velocity fluctuations and the invariants of the Reynolds stress anisotropy tensor are also calculated. The mean radial velocity agrees with that calculated from the continuity equation and the mean streamwise velocity. The Reynolds shear stress is also in good agreement with that estimated from the momentum equation. These results demonstrate the accuracy and consistency of the present data.

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Results of the measurement of flow properties in a two-dimensional turbulent wall jet which is injected into the turbulent boundary layer in the direction opposing the boundary layer flow are presented. The specifics of a tandem hot-wire probe manufactured in order to measure the flow in the recirculating or low-speed-flow region are first examined, and the validity of its use is confirmed. With the use of this probe, the change in the jet-reached distance from the nozzle with the velocity ratio is investigated. Measured mean velocity, fluctuating velocity and static pressure reveal the variation in the flow field with the velocity ratio. In particular, it is clarified that there exist two regimes of flow patterns. Streamlines, turbulent intensity contours and static pressure contours for two regimes are presented.

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In the present study, a two-phase flow model based on local relative velocity, which had been previously proposed by the authors, was extended to a model for gas-liquid-solid three-phase flows. The extension was carried out by utilizing a hypothetical two-phase flow, which is conceived by removing one phase of the three phases. In order to examine the usefulness of the extended model, the measured area-averaged volumetric fractions of gas-liquid-solid three-phase bubbly or slug flows in vertical pipes were correlated based on the basic equations of the model. The accuracy of the obtained correlation was compared with the drift-flux correlation, the correlation based on a multiplier method and the correlation based on a gas-liquid-solid three-phase slug flow model. Consequently, it was confirmed that the extended model gives simpler and more accurate correlations for the area-averaged volumetric fractions of the gas-liquid-solid three-phase flows.

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In order to enhance stability of the implicit scheme for the initial stress rate method, a nonlinear source term is usually approximated by a linear function with a negative gradient. This analytical procedure is not always possible for a complicated problem such as a solidification simulation. Here, a numerical procedure for linearization is proposed which is theoretically based on the penalty method. A fastening of degrees of freedom and solidification simulation by the temperature recovering method are demonstrated to show the appropriateness of the proposed method.

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The resistance force of a sphere moving through air towards a plane surface is associated with the mechanism of particle deposition. In the continuous fluid, the resistance force increases infinitely near the plane surface. However, there has been no investigation on the effect of discontinuous fluid, for instance, air for fine particles whose diameters are as small as several micrometers. In air, the resistance force of the fine particles near the surface does not seem to increase infinitely and thus fine particles would be deposited more easily. It was extremely difficult to measure the resistance force of fine particles directly, so we measured the resistance force of a 6.3 mm foamed styrene ball under reduced pressure. At 10 Pa, the mean free path of air is 670 μm and the Knudsen number of the styrene ball is equivalent to that of a 0.6μm particle in the atmospheric air. The experimental data show that the increment of the resistance force acting on a 6.3 mm sphere near the solid wall under reduced pressure decreases with decreasing air pressure. Hence, it would be concluded that the resistance force of the fine particles near the solid wall in the air is much less than that acting in the continuous fluid.

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The shock shapes around slender diamond cones were obtained using the law of conservation of mass and the equivalence principle for hypersonic flows passing slender bodies. Theoretical shock shape obtained by this method agreed well with the experimental result obtained by the first electric discharge method. It was confirmed that this method is effective in calculating the shock shape around an arbitrary slender body traveling at hypersonic speed.

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Unstarted supersonic flutter in a cascade is characterized by the existence of a detached bow shock wave ahead of each airfoil. To study the influence of the bow shock wave on this flutter, analysis is performed on the corresponding flow field, with use of the semiactuator disk theory. We investigate oscillation in the bending mode with the interblade phase angle, considering the effect of reflection of the pressure wave and production of a vorticity wave and an entropy wave by the bow shock wave. The results show that the existence of detached bow shock waves greatly destabilizes bending oscillation, and the flutter boundary drastically extends to a high-frequency region.

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The unsteady convection-diffusion equation is one of the most important equation in heat and fluid analysis. One of the authors developed the modified Galerkin method (MGM) for the one-dimensional convection-diffusion equation. In this paper, this modified Galerkin method was proposed for three-dimensional convection-diffusion equation using an error analysis technique based on the Fourier series. The correction coefficients of several numerical methods were obtained for various kinds of three-dimensional nodes, and they were used for correcting numerical methods using the implicit and explicit methods. Then all of these methods were investigated from the viewpoints of phase error and dissipation error. The MGM for a regular hexahedra element was proven to be the most efficient numerical method. Through numerical experiments using the implicit and explicit methods, we confirmed the effectiveness of our correction method and the general correspondence between the error analysis and numerical simulation.

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Numerical simulations for every flow, need enormous computing time during iterations. In order to solve this problem several techniques have been proposed, for example, a multigrid technique. A method using qualitative reasoning is one such technique. Qualitative reasoning regards two situations, which are different quantitatively but same qualitatively. as the same. Thus it produces a discrete expression for a physical phenomenon. To compensate this discreteness fuzzy logic can be introduced into the reasoning. We studied the possibility of computational acceleration with fuzzy logic and qualitative reasoning in numerical simulations. Some rules were constructed and applied to incompressible backward-facing and forward-facing step flows. It was found that our procedure can realize a considerable acceleration.

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Performance of a vane compressor used for automotive air conditioners is affected greatly by frictional losses on sliding parts of the vane. In order to estimate these losses exactly, analysis taking account of lubricating characteristics is needed, because the friction has a close relation with the lubricating condition which changes from boundary lubrication to hydrodynamic lubrication on some conditions. In this paper we elucidated the lubrication on the vane tip of a through-vane compressor by measuring coefficient of friction on that point, and evaluated the lubricating characteristics on sliding parts of the vane by applying the measured result, and then estimated frictional losses. As a result, we identified that lubricating condition is severe at low rotational speed, and that frictional loss at the vane tip under the variable condition of the coefficient of friction is smaller than that under the constant coefficient condition.

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Computer simulation of refrigerating cycles for automotive air conditioners is effective in predicting performance of the cycle. To predict the performance exactly a proper mathematical model of a compressor is needed. In this study, the mathematical model of a vane compressor for the automotive air conditioning cycle is developed. The model consists of two control volumes, a cylinder and a rear case, and a compressor body. It takes account of influences of lubricating oil and heat transfer between refrigerant and the compressor body. Validity of the model is confirmed by comparison between calculated results and experimental ones. Propriety of the compressor modeling in the cycle simulation influences transient behavior of the cycle greatly.

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The production system of compressed air in wave energy conversion, in which the self-rectified air turbine is installed and the principle of oscillating water column is utilized, is proposed and discussed. Actual sea conditions such as the variation of wave height are taken into account. Wells turbine is the most advantageous for the proposed system due to its simple structure, satisfactory efficiency and actual achievements in former projects. The screw compressor in positive-displacement-type fluid machinery is introduced here, because the required performance of the compressor in one unit is more than 6 ata in pressure increase and less than 200 kW in power, and because the pressure should be constant in the air tank submerged at the bottom of the sea irrespective of the variance in wave energy power. As for the connection between the turbine and the compressor, the CVT (continuously variable transmission) can provide us with the most efficient system among the transmissions discussed here such as the fluid torque converter, the gear system and the direct connection between the air turbine and compressor in the turbomachinery.

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Mobile or stationary fluid power systems require no leak valves with proportional flow controllability. Following the development of a proportional seat valve with feedback solts, the authors have designed an electrohydraulic seat valve with a momentum flowmeter which compensates the flow fluctuation of the valve due to load pressure changes. The flow control seat valve operated by a PWM(Pulse Width Modulation) switching pilot valve controls flow rates to 80 L/min within 0.1 s. The paper shows transient characteristics of the valve and its simulation results by bond graph analyses including PID controllers.

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The blade-passing frequency noise of a low specific speed centrifugal blower is discussed by separating the intensity of the noise source and the response of the transmission passage. The frequency-response function in the transmission passage has previously been evaluated by the authors using a plane wave model, and the results have indicated various effects of the blower speed, blade number and inlet duct length. In the present study, the effective location of the noise source is determined by analyzing the cross correlation between measured data of the blower suction noise and pressure fluctuations on the scroll surface. Then, the surface density distribution of a dipole source is determined from the pressure fluctuation which is expressed by the quasi-steady dynamic pressure of the traveling blade wake. By integration of the surface density spectrum of the noise source over the effective source area, the free-field noise level is obtained. The blower suction noise level is finally predicted by operating the frequency-response function. The results agree well with the measured data, and the effect of the distance between the impeller and the scroll cut off is accounted for satisfactorily.

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When an open-type impeller was operated near the flow rate for shockless entry, a large component in the velocity fluctuation spectrum was observed outside the impeller. The frequency of this component was equal to that of the impeller rotation. The origin of this component was studied experimentally. The flow conditions near the flow rate where the large component was observed were determined for an open impeller and for a closed impeller. From the experiment, it became clear that the flow pattern including a back flow region in the open impeller was changed near the above mentioned flow rate, and at that particular flow rate, two types of velocity distributions existed in the impeller channels. Thus, the large component of the velocity fluctuation was observed outside the impeller. In this paper, the flow pattern which caused the velocity fluctuation is discussed.

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This paper presents a numerical analysis method for a separated unsteady flow in a centrifugal impeller. Considering the influence of the boundary layer, the flow. which is assumed to be two-dimensional, inviscid and incompressible, is analyzed using both the boundary element method and the discrete vortex method. Based on Karman's momentum and Poisson's equation, the changes in the displacement thickness are solved and the separation point on the boundary layer is determined automatically by the shape factor H of the turbulent flow. The velocity field and the pressure distributions are solved for the discharge coefficient C_e=Q/Q_n (in this paper, C_e=0.6).

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The internal flow in a cross-flow turbine is nonuniform because the water passes through only part of the runner. Therefore, the unsteady fluid forces act on a blade through rotation. The experimental and theoretical studies for determination of fluid forces on the blade in a cross-flow turbine are conducted. In the experiment, the tangential and radial forces are measured on a test blade using the strain gauges and slip rings. On the other hand, in the theoretical study, they are calculated numerically using the unsteady momentum theory. The calculated results are compared with experimental data and good agreement between them is demonstrated. Furthermore, the maximum forces are found to occur immediately before the blade leaves the nozzle exit in both the experimental and theoretical results.

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As a new type of actual-sized cryopump with high pumping speed, a parallel-louvre-blind type cryopump of a rectangular cross section with opening distance B, width C and depth D, is proposed and is produced as a trial pump unit designed as actual size. The influence of pump depth size ratio R_d(=D/B) and number of secondary cryopanels on the transmission Probability P_bc of the pump unit is calculated by Monte Carlo simulation, and the hydrogen pumping speed is measured by experiments. The following results are obtained. (1) The transmission probability of a cryopump designed with dimensional ratio of R_d=1.3 is calculated to be 0.66 at ratios of R_c(=β/C)=0.88, which means that hydrogen pumping speed of cryopumps of this size can attain 294 m³·s^-1/m² per opening area. (2) The real hydrogen pumping speed of the trial pump unit with 30 secondary cryopanels is measured as 295m³·s^-1/m².

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A newly developed pumping system is presented. The pumping effect was experimentally obtained using a vibrating choke nozzle in a stationary liquid. The relationship of pump performance to the input vibration conditions was investigated experimentally. By the flow visualization of inflow and outflow bubbles, the flow mechanism in the actual pump operation was investigated. It has been confirmed from the experimental observation that this pumping effect can be utilized as actual pump machinery.

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A molecular dynamics (MD) study was performed on water in wide ranges of temperatures and densities. The vapor-liquid coexistence region and near-critical region are intensively studied. By applying the Carravetta-Clementi (CC) potential model for the intermolecular potential function, the pressure and enthalpy responses to temperature and density were obtained. Microscopic information on the molecular structure and behavior, including the velocity auto-correlation and the formation of dimers and clusters, is also presented.

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Similarity solutions for free-convection condensation of an air-steam mixture, where the bulk air mass concentrations W_1V∞ are 0.1, 0.01 and 0.001 and the bulk temperatures T_V∞ are 100, 65.56°C and 26.67°C, are presented. From the solutions, a new correlation equation for the gradient of W_1V at the vapor-liquid interface is obtained. It is confirmed that this equation agrees well with the similarity solutions not only for an air-steam mixture with large W_1V∞ values but also for mixtures of ethanol-water and CFC114-CFC11. The algebraic solution using the equation compares well with existing experimental results, even for a helium-steam mixture when the absolute value of the buoyancy term is taken. It is also discussed that the discrepancy between the theoretical solution and the experimental results by Slegers and Seban may be caused by the choice of the representative value of the bulk mass concentration rather than by the effect of forced convection.

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This paper presents a comparison of measured condensation heat transfer coefficients for refrigerant CFC-11 and its proposed replacement HCFC-123 flowing down a 3×15 (columns×rows) in-line bundle of horizontal finned tubes. The vapor velocity at the tube bundle inlet (based on minimum flow cross section) ranged from 0.9 to 10 m/s, and the condensation temperature difference from 1.3 to 19K. Heat transfer measurements were made on a row-by-row basis. Generally, the heat transfer coefficient for HCFC-123 was about 10% lower than that for CFC-11. The heat transfer enhancement due to vapor shear was much smaller than that in the case of a smooth tube bundle. At a high vapor velocity, the enhancement was most significant for the top row and decreased sharply with increasing row number. The decrease in the heat transfer coefficient due to condensate inundation was also much smaller for the finned tube bundle. The measured heat transfer coefficient for the smallest vapor velocity agreed well with the theoretical prediction for a stagnant vapor.

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Solid/liquid phase-change heat transfer in porous media has been extensively studied in the past several years, and effects of various parameters on the heat transfer have been examined. In the melting process, natural convection plays an important role to determine the melting rate and the phenomenon becomes complicated. This is quite different from the solidification problems in which heat conduction usually dominates the process. As far as the authors could determine, no studies appear to have been reported on the effect of the orientation of a hot surface with fins, which is reliable and effective for the heat transfer enhancement, on the melting process, despite of the fact that it greatly affects the natural convection and the melting rate. In the present study, calculations have been performed for melting processes around a hot wall with fins using a numerical method which the authors recently proposed. And, the effect of the orientation of the hot surface on the effectiveness of the attached fins has been examined.

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In order to provide higher cooling performance for transformer windings which use nonflammable coolant, conductors wound with thread spacers were applied to the windings to enlarge cooling surface area. Since coolant would flow in the narrow spaces around the conductors, it was necessary to clarify the How and cooling characteristics in the thread spacer windings. Using a two-dimensional winding model, the pressure drop in the windings and the temperature rise in the conductors were measured for different heat fluxes and flow rates. The winding model consisted of model conductors in which thermocouples and thin heater pins were soldered and wrapped in insulating papers. The conductors were wound with thread spacers of 0.75 mm diameter. The temperature rises in these thread spacer windings were found to be significantly lower than those in conventional baffle plate windings. The maximum difference in the temperature rises in the windings was also small and overheating of conductors did not occur at low flow rates in the present test. The pressure drops for the thread spacer windings were predicted as being almost equal to those in baffle plate windings for commercial transformers.

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A two-dimensional numerical computation was performed for the unsteady flow and heat transfer in a channel obstructed by a square rod mounted in an asymmetric manner. The displacement of the rod position from the center plane of the channel, e, and the rod size, d, were changed in several steps. The channel Reynolds number was also changed in several steps in the case of d/H=0.3. When e/H becomes larger, the flow tends to be more stable. Even in the cases where flow instability is incurred, enhancement of heat transfer due to the unsteadiness of the flow becomes less remarkable as the value of e/H increases. In the present flow situation, it is concluded that the unsteadiness of the flow does not enhance the heat transfer from the walls effectively.

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The heat transfer characteristics of an oblique impinging round jet with confined wall were investigated experimentally. The parameters investigated were Reynolds number in the range 2000-20000, the jet angle at 45, 60°and 90°measured from the horizontal and dimensionless distance between nozzle and impinged surface, h/D=1.0. The local temperature distribution on the impinged surface was obtained in detail by a thermocamera using liquid crystal. The local heat flux was compensated by using the detailed temperature distribution and numerically solving the equation of heat conduction. Two-dimensional profiles of local Nusselt number and temperature changed with jet angle and Reynolds number. They showed the peak shift and plateau of the local heat transfer.

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Carbon-cabon composites are important structural materials at high temperature. Their thermal properties and microscopic structures change with the temperature and the time required for heat treatment. It is expected that the thermal diffusivity and porosity show different values at every moment during heat treatment. The objective of this study is to evaluate the time dependence of the thermal diffusivity and porosity simultaneously using the electromagnetic ultrasonic technique. This report describes the principles of measurement of the properties and the experiment to confirm the principles separately at room temperature. The longitudinal ultrasonic velocities of aluminum and carbon brick in the evaluation of porosity are 6350 m/s and 2530 m/s with precision of ±1.6% and ±0.4%, respectively. Is was confirmed that the aluminum and the carbon electrodes were able to be heated by the electromagnetic ultrasonic transducer. The thermal diffusivity of carbon brick measures 8-9 mm²/s but the accuracy of measurement will have to be investigated using the standard material in the future.

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Since solid/liquid phase-change heat transfer in porous media occurs in many systems, extensive studies have been conducted in the past several years. In such systems, the heat transfer coefficient is usually very small due to a small thermal conductivity in the systems and a large resistance to the fluid flow due to a porous matrix. Therefore, some means to enhance the heat transfer is needed for the systems. In the present study, the effect of fins attached to a heat transfer surface on the heat transfer enhancement for the solidification process has been examined using a simple quasi-steady model and an accurate finite diffence method. The applicability of the quasi-steady model has been checked by comparing the calculated results with experimental ones. In addition, the effects of important nondimensional parameters appearing in the governing equations have been examined using the finite difference method.

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An experimental study has been carried out to clarify the characteristics of the liquid film thickness of air-water two-phase flow in a helically coiled tube placed horizontally. The distribution of the time-averaged local liquid film thickness around a tube periphery varies along the circumference of the coil at low gas velocities. A subsidiary peak of the film thickness forms on the outer side of the coil for large liquid flow rates. The mechanism of peak formation varies with magnitude of the gas velocity. The peripherally averaged liquid film thickness of a tube section in a coiled tube is thicker than that in a straight tube at high gas velocities. When the superficial gas velocity exceeds 20∼30 m/s, the centrifugal force of the gas-phase is dominant on the distribution of the film thickness around the tube periphery at the lower section. At a high gas velocity, it is expected that the characteristics of the liquid film on the downward or upward section of the coil are similar to those in a microgravity environment.

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Interaction between a detonation and the Prandtl-Meyer expansion is an interesting problem in connection with disappearance or continuance of the fish-scale pattern. In this study, seven kinds of reflection nozzles were utilized in order to produce the Prandtl-Meyer expansion effects at various levels. Stability and behavior of detonation propagating in a reflection nozzle incorporating with a parallel channel part were experimentally observed with the initial pressure as a parameter using optical measurement methods such as open-shutter and schlieren photographic techniques. It was found that in the case of a nozzle at the half-vertical angle of A=18 degrees without the throat length, an initial pressure of at least 5.3 kPa is needed for sustentation of detonation configuration during passage through this nozzle.

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An advanced design concept of the gas-firing combustion chamber for boilers and its application to actual boiler development are presented in this paper. The concept brings about a drastic reduction of the boiler size while limiting the NO_x concentration of the exhaust gas. The key is the accelerated and temperature-controlled combustion in the jaggy-fireball generated in the tube-nested combustor. The proof test of the concept was carried out using small-scale test equipment. Application to actual boilers is under way.

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To improve the burning conditions of the residual fuel in the combustion chamber of a diesel engine, visualization and combustion diagnoses of the residual fuel spray were carried out. First, physical effects of the impingement of spray on the combustion chamber wall and the air swirl were verified. Next, the effect of increase of air temperature in the combustion chamber on the ignition delay and combustion conditions were examined. As a result, it was made clear that some means of improving the evaporation rate is necessary for the residual spray. But it is difficult to improve the evaporation rate of the residual components themselves. So, as an alternative means, the acceleration of the combustion of the distillate components included in the residual fuel must be achieved to promote the combustion of the residual components.

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A Single-action rapid compression machine was developed to observe soot formation and oxidation processes in a diesel spray flame. The two-color method was applied to analyze the flame temperature and KL factor from the flame image taken by a high-speed camera. Variation in the surrounding gas-oxygen concentration was achieved by adding differing quantities of pure oxygen, nitrogen, carbon dioxide and argon gases in charging air ranging from 17 to 25 vol% of oxygen concentration to examine the effect of flame temperature. The initial gas temperature has a great effect not only on the ignition delay but also on soot formation speed. Higher oxygen concentration resulted in higher flame temperature and faster soot oxidation speed in the flame. Carbon dioxides have a soot-reduction effect in spite of its lower flame temperature.

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The near wall K-ε turbulence model of Chien is applied to simulate the flow in the intake port of an automotive engine. In order to investigate the improvement in prediction accuracy due to incorporation of this model, the effects of changes in port curvature on the mass flow rate were computed, and the predictions were compared to our computational results without turbulence model and test results. It is demonstrated that Chien's K-ε model has the potential for improving the prediction accuracy of the flow in an intake port.

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The measurement system for the oxygen permeable resistance in cultured endothelial cells has been developed. Permeable resistance has been defined as thickness/permeability, (atm·sec/cm). The values of oxygen permeable resistance were measured using a quasi-steady method. Porcine endothelial cells were cultured on a collagen membrane cup. The membranes were placed as a diffusion barrier between two chambers. Chamber 1 was ventilated using a standard gas mixture with low oxygen partial pressure and chamber 2 was filled with phosphate buffer saline [PBS(+)] having high oxygen partial pressure thereby creating on oxygen partial pressure difference across the membrane. After the steady state was reached, the ventilation in chamber 1 was discontinued, and the change of oxygen partial pressure in the chamber 1 was monitored by O₂ electrode. The values of oxygen permeable resistance were obtained by deducting the value of oxygen permeable resistance in the collagen membrane. In this study, the oxygen permeable resistance was measured with the maximum predictable error of 9-10%.

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Optical-CT (Computed Tomography) imaging of living bodies poses the difficulty caused by strong scattering of light by tissues. In our previous paper, time-resolved spectroscopy was shown to have potential for realization of optical-CT imaging. In this second paper, it is shown that utilization of the characteristics of strong scattering makes fan-beam-type optical-CT imaging possible. The Monte Carlo method is employed to simulate the strongly scattering and weakly absorbing media. Hybrid scattering calculation is proposed to simulate the highly forward-directed scattering to avoid unrealistic sharp peaks at the shortest time of flight observed when only isotropic scattering approximation is employed. The temporally extrapolated absorbance method is employed for the object and reference cylinder, as in the previous paper. Fan-beam-type optical-CT imaging is numerically shown to be capable of reconstructing an image of the difference in the absorption coefficient with satisfactory accuracy and spatial resolution.

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