Medical applications of ultrasound such as High Intensity Focused Ultrasound, Extracorporeal Lithotripsy and ultrasound contrast agent imaging have recently been the subject of much interest as the medical application of fluid dynamics. In these applications, nonlinear bubble motion facilitates the medical treatment by improving the image quality or enhancing the therapeutic effects through localized heating, erosion or acoustic emission. Utilizing those phenomena, a diagnostic and therapeutic integrated system can be developed. It is essential to understand ultrasound propagating and heating phenomena in a human body, which is inhomogeneous medium, and enhanced local heating phenomena by micro bubbles. In this paper, medical applications of ultrasound with microbubbles, acoustic cavitation and ultrasound propagation in human body are highlighted.

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This study develops an efficient parallel simulation of colliding particles in stationary isotropic turbulence. Flow is computed with a fourth-order finite-difference method and particles are tracked with the Lagrangian method. Particle collisions are efficiently detected by the cell-index method, which is often used in molecular dynamics simulations. The developed code is written in Fortran 90 in conjunction with MPI library. Auto-parallelization directives are inserted in the code for shared-memory parallelization, making it possible to run the code in the so-called hybrid-parallelization mode. The code is designed to minimize the MPI communication, which results in a high parallel performance. The present simulation has been run on up to 512³ grids with 10 million particles. The largest simulation has successfully obtained the collision frequencies for the Taylor-scale-based Reynolds number, Re_λ, of 209, which is much larger than previously attained maximum Re_λ of 85 in particle collision simulations. The collision frequencies obtained in this study have shown that a collision frequency model underestimates the frequency in high Re_λ flows.

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An experimental study of a three-dimensional (3-D) blade-type riblet has been performed. The lateral spacing of the 3-D riblet surface is periodically changed in the streamwise direction. The net drag reduction rate of about 9% has been confirmed in a low-speed wind channel at the bulk Reynolds number of 4000. The flow structure over the 3-D riblet was also analyzed in the velocity field by using 2-D Particle Image Velocimetry in x-z and x-y planes and was compared with the corresponding flow over the flat surface in an attempt to identify the physical mechanisms for drag reduction. Under the drag-reducing condition, the streamwise length of the streaky structures becomes shorter, which is the different phenomenon from those for well-known 2-D riblets. Moreover, quadrant analysis has been conducted to investigate the events contributing to the Reynolds shear stress. The second (ejection) and forth (sweep) quadrants are decreased, whereas it was interesting to note that the first (outward) and third (inward) quadrants are increased near the 3-D riblet.

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In many fluid-structure interaction problems, the virtual mass, namely, the added mass is one of important interests. In the present study, the authors investigate the validity of a numerical method previously proposed by them in order to specify the added mass coefficient of arbitrary two-dimensional solid bodies efficiently and conveniently. In this method, we consider a two-dimensional incompressible viscous fluid under the assumption of an infinitesimal oscillation amplitude of the body, and properly modify the Navier-Stokes equations into linear equations the Brinkman equations. The solving method is based on a discrete singularity method. In order to show the method's effectivity and validity, the authors compute some flows around the bodies with fundamental cross sections with/without sharp edges, which oscillate in infinite flow fields. In addition, the authors solve the full Navier-Stokes equations by a finite difference method, and compare with each other to specify the valid range of the method. Then, the authors confirm the nonliner amplitude effect and specify the valid range for the method.

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We investigate the flow between co-rotating disks with a narrow gap, enclosed by a stationary shroud at their circumferences, using flow visualisations with PIV analyses. Experiments are conducted at three values of non-dimensional hub radius κ in wide ranges of other two system parameters, namely, disk-tip Reynolds number Re and gap aspect ratio δ. As a result, we reveal stability diagrams concerning core-shape modes of the flow defined by the modal number m. Except for the m = ∞, m decreases with increasing κ, as well as increasing Re and increasing δ. Especially at δ > 0.2, the influence of κ upon m is remarkable. Besides, we find out a new core-shape mode with m of unity, at large Re, large δ and large κ. This core-shape mode 1 is the mode where there exists only one bulk of the fluid in rigidly-rotational motion, which is attached to the hub and travels in the azimuthal direction with a rotation speed less than the disks'.

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In this study, we experimentally deal with the tumbling, which is a rotating motion of a plate with its axis perpendicular to the falling direction. As the plate, we consider a rectangular-cross-section prism with a depth-to-width ratio λ = 0.3, an aspect ratio AR = 10, and inertia moment ratios I ^* = 0.75 - 43, together with a wide range of a non-dimensional control parameter C = 7.2×10¹ - 1.6×10³. As a result, we specify fundamental aerodynamic characteristics in terminal condition, like the reduced rotating rate Ω^*, the lift coefficient C_L, the drag coefficient C_D and the lift-to-drag ratio C_L/C_D as functions of both C and I ^*. Moreover, the relation between the actual Reynolds number Re and the Reynolds number Re(V_d) based on V_d can be approximately determined, being independent of C and I ^*. Eventually, we successfully propose a series of empirical formulae to predict Ω^*, C_L, C_D and C_L/C_D as functions of Re(V_d) alone, which is available for a wide parameter range except for large C and small I ^*.

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Previously proposed theories on the minimum-heat-flux-point (MHF-point) condition were examined using available data obtained from the immersion cooling experiments of spheres in water. The sphere diameter ranged from 9.5 mm to 30mm and the liquid subcooling from 0 K to 85 K. The limiting liquid superheat predicted by the Lienhard equation was compared with the wall superheat at the instant of liquid-solid contact at the MHF-point. The results showed that the wall superheat at the MHF-point was not limited by the limiting liquid superheat and its value was connected with the collapse mode of vapor film. The collapse mode was a coherent collapse at a low wall superheat and the mode changed to a propagative collapse as the wall superheat increased. The critical vapor film thickness obtained from the linear stability analysis of vapor film was compared with the calculated value of average vapor film thickness at the MHF-point. For all data, the ratio of the average vapor film thickness and the critical vapor film thickness was correlated well as a function of liquid subcooling. The ratio decreased with increasing liquid subcooling and tended to 0.8 to 1 depending on the experiments. This indicated that the MHF-point at a high liquid subcooling was determined by the critical vapor film thickness. A physical consideration was given to the effect of liquid-solid contact that occurred in the film boiling region on the calculated value of the vapor film thickness and the stability of vapor film.

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The recent development of information technologies due to advent of a new generation of semiconductor devices has brought us serious problems associated with high heat generation density. Conventional cooling methods such as fin heat sinks with blowing fans may not be sufficient to solve such serious heat related problems. Thus, in this study, we propose a new kind of heat sink as a solution to the problems, namely, a pin fin heat sink filled with metal foams. A series of exhaustive experiments have been conducted to confirm heat transfer enhancement as results of extended surface area and fluid mixing due to the presence of metal foams. Theoretical consideration has also been made so as to elucidate such heat transfer enhancement mechanism.

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We experimentally investigated the soot emission characteristics of the coflow diffusion flame undergoing periodic fluctuation of fuel and air flow rates. The flame has been acoustically forced using sine-wave excitation of a loudspeaker attached to the upstream side of the burner. A fuel (propane) and an air are supplied respectively from inner tube and outer tube. The obtained results are summarized as follows: (1) The soot emission characteristics of the unsteady flame are worse than that of the steady flame. (2)The air flow rate at the soot limit increases monotonously as the mean value of fluctuating fuel flow rate increases as for the soot limit curve when frequency f is small. However, the soot limit curve becomes S shape when f is large. (3)Bulge and the separation of the flame tip are observed at f =16Hz and the soot emission characteristics deteriorate further. (4) Soot limit curve of the air flow rate change flame is similar to that of the fuel flow rate change flame.

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Radiative characteristics of one-dimensional structured emitter was investigated through calculating emission of thermal radiation by solving the Maxwell's Equations using a FDTD method. The radiative simulation based on fluctuational electrodynamics enable to evaluate quantitative emission of thermal radiation. For a specular emitter made of nickel metal with a thin-transparent film, some interference was described through simulation solving emission of thermal radiation. For a shallow-grooved surface emitter made of silicon carbide, surface-phonon polaritons were coupled with a propagating-radiation by the periodic structure. Finally, the characteristics of emission controls by the specular metal with the thin-transparent film and the shallow-grooved surface emitter were illustrated and compared from a point of view of emission of thermal radiation.

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It is well Known that the conventional method to detect presence and strength of the knocking by the ion current using the band pass filter is effective up to now. However, as compression ratio increases, there is a stationary wave in the ion current waveform and its frequency components and amplitude of the waveform are almost same as that of the knocking. Therefore the distinction of knocking and the standing wave becomes difficult by the conventional detection method. In this study, a new knocking detection technique which based on the difference of time-frequency properties of knocking and the standing wave was proposed. It first constitutes two band-pass complex real-signal mother wavelets (BC-RMW), and then thereby takes out the knocking ingredient and detects a change share of the wavelet coefficient of the knocking by using them. Furthermore, the proposed method was applied to the distinction of knocking and the standing wave and its effectiveness was inspected.

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Integrating distributed energy resources can reduce power transmission losses, improve the efficacy of waste heat usage, and utilize green energy. To promote the spread of green energy, improve the method of supplying energy in times of disaster, and utilize waste heat more efficiently, a distributed energy system using a microgrid was examined in this study. Generally, the output characteristics of the power sources using a microgrid are nonlinear. Furthermore, because multiple power sources are used in microgrids, many variables must be considered to optimize the system. Although the operation of energy systems has been optimized before, nonlinear problems with many variables have only been approximated by linear formulas with mixed-integer-programming. Furthermore, in this study, a method of searching for the optimal solution with a genetic algorithm (GA) is also reported. Any method for obtaining the optimal solution will require a longer time if the number of variables is increased or a higher accuracy is required in the analysis. Otherwise, only quasi-optimal solutions and unsatisfactory solutions of the energy balance equations are obtained. Therefore, orthogonal arrays are employed in this paper to reduce the complexity of the problem to plan the optimal operation method of a compound energy system. The operation range of the system that is considered to include the optimal operation method is limited to narrow range with an orthogonal array. Next, a solution for the optimal operation is obtained within the range obtained by the factor-effect figure using a GA. An example is given in this paper to explain the GA-orthogonal array hybrid analyzing method. The proposed analysis method can be utilized to improve the design parameters and the accuracy of the performance analysis.

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The mass transfer characteristics of gas diffusion layer (GDL) are closely related to cell performance in polymer electrolyte fuel cell (PEFC). It is necessary to characterize the liquid water distribution, the microscopic conformation, and the oxygen diffusion coefficient in a GDL containing moisture. The configurations of a novel hybrid type GDL, in which two porous media with different wettabilities are arranged alternately ^(1),(2) and two porous media with different pore size distributions were alternately arranged ⁽³⁾, have been proposed with the aim of improving the oxygen diffusivity by controlling the moisture distribution in GDL porous media. However, the basic principles of hybrid type GDLs were examined in the former reports as a pilot study by using thicker media than those used in practice. It is thus necessary to elucidate the performance of the hybrid type GDLs with thinner sizes for the practical use. The present study examined a hybrid type GDL to control the liquid water behavior in the porous media. A carbon paper GDL used in practice for PEFCs with a wettability distribution due to adjacent hydrophilic and hydrophobic region was used as a test material. The measurement of oxygen diffusivity and visualization of liquid water in the GDL with wettability distribution were performed simultaneously using a galvanic battery type oxygen absorber and X-ray radiography, respectively.

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This paper presents an investigation of the influence of nitrogen addition on the thermoelectric conversion performance of diamond-like carbon (DLC) films on glass substrates using RF plasma chemical vapor deposition. The respective thermoelectric conversion performances and Hall effect of the DLC films were evaluated and compared as a function of Nitrogen concentration. And film composition and atomic bond structure were characterized using Raman spectroscopy and XPS. At temperature of 473.2K, absolute value of Seebeck coefficients of the DLC films decreased concomitantly with increasing nitrogen concentration at 0—4.0at.%. However, the Seebeck coefficients of 4.0—8.1at.% were almost identical. At temperature at 298.2K, the Seebeck coefficients of 0—8.1at.% were almost identical regardless of the concentration of nitrogen. At temperature of 298.2K, specific resistance of the DLC films decreased concomitantly with increasing nitrogen concentration at 0—4.0at.%. However, the specific resistance of 4.0—8.1at.% was almost identical. The power factor of the DLC films increased concomitantly with increasing nitrogen concentration below the temperature of 398.2K. Hall effect measurements revealed that the difference by nitrogen concentration of Seebeck coefficient and specific resistance are expressed as a function of the carrier density and the carrier mobility respectively. Considering the results of Raman spectroscopy and XPS revealed that the sp³ bond in the DLC film increases with increasing nitrogen concentration. Thus, it was suggested that the electrical properties and semiconductor properties of DLC films depend on the sp²/sp³ fraction in the films.

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The purpose of this research is to clarify the requirements for the high output power density of SMA engine. In order to put the SMA engine in practical use, maximizing the output power density is most important from the viewpoint of economical efficiency. The output power of the SMA engine highly depends on the diameter of the SMA belt and the radius of the high temperature wheel. In this study we will change the diameter of the SMA belt and theoretically explain whether there is a relational expression between it and the radiuses of the high temperature wheel and the low temperature wheel of the SMA engine. If the radius of the low temperature wheel (R) is determined, the equipment width (W) of the SMA engine is also determined (W=2R). Next, the height of the SMA engine is determined experimentally by the cooling conditions of the SMA belt. Finally, the depth of the SMA engine is determined by the diameter of the SMA belt(D=d).Since the output power of the SMA engine can be calculated by the theoretical formula, we can divide it by the volume of the SMA engine and thus, calculate the output power density of the SMA engine. As the result, changing the diameter of the SMA belt, we can calculate the most appropriate value, at which the output power density of the SMA engine is maximal.

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Reduction of CO₂ emissions and energy saving are the urgent issues for many fields of industries at present. Hot water, occupying considerable energy consumption rate in the whole industry, is generally generated using combustion gas being higher than 1,000 centigrade at boilers. However, the temperature loss is large at boiler process. Accordingly, we thought that energy saving could be accomplished if hot water could be generated using heat pumps. This presentation reports field test of a newly developed turbo heat pump for hot water in an actual factory. The heat pump is characterized by high efficiency and large amount of heat output, which equals approximately steam of 1,000 kg / hour, using turbo compressor. As a result of the field test, it was confirmed that the performance of the heat pump was the same as that of design.

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