This paper is concerned with the aerodynamic characteristics of flying insects. Some morphological parameters were presented for a variety of insects : mass, wing area and flapping frequency. The relationship between total wing area and flapping frequency was investigated. Dragonflies are used as examples in this report. The self-excited vibration of dragonfly wings was examined in a uniform smooth windstream, and the flow characteristics around a dragonfly were measured with a hot-wire anemometer. Dragonflies of two kinds, Sympetrum frequens and Sympetrum infuscatum, were tested in a wind tunnel. Galloping oscillation of the dragonfly wing was measured by use of an optical displacement detector system. Velocity fluctuations produced by the flying dragonfly in a uniform smooth windstream were measured with a hot-wire anemometer. It was found experimentally that the excitation amplitude of the wing vibration increased when wind velocity exceeded a certain value. It was also found that the waveform and the spectrum of the velocity fluctuation produced behind the dragonfly differed with the location along the wingspan.

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The INS 3 D-code, a finite-difference code originally developed to simulate incompressible flow past a single grid object, is modified to simulate flow into, through and around the oral cavity of the blackfish (Orthodon microlepidotus). The geometry of the mouth of the blackfish is represented by a cone with three slanted slits on each of two sides. These slits represent the gaps between the gill arches where fluid entering the mouth escapes. The computational domain is represented by its own grid placed inside O-type cylindrical grids representing the front and exterior of the mouth. Our simulations show that gill-arch structures direct the flow of water to the roof of the oral cavity, where feed particles are retained. The inclination of the gill arch and the effects of the Reynolds number determine the amount of flow directed upwards and thus the path of the food particles and the resistance on the fish due to the fluid.

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The application of dynamics of the living organism to the field of engineering is very instructive. To make an artificial bending-wave propulsion mechanism, a propulsion mechanism imitating the bending motion of organisms in water was developed. As the bending motion, a swimming snake's motion was employed. The bending wave of the organism was changed into a construction of the multilink mechanism. This model was defined as the "multilink imitated model". As the bending curve of the model, the serpenoid curve and sine curve were adopted. The thrust force of the model was measured. The characteristics of the thrust force with change in the ratio amplitude/wave-length, the frequency, the number of links and the bending curve were discussed.

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A terrestrial gastropod moves on highly viscous mucus with surface waves. The model presented in this paper considers the shear flow induced by surface velocity of the foot. According to the numerical analysis, the body moves in the same direction as the surface waves. The film thickness shows a wavy distribution due to the shear flow induced by the periodic stretch-shrink action. Consequently, the net traction becomes positive because of the phase difference between the film thickness and the surface velocity. The calculated result was compared with the measured result for a snail. Such a mechanism may be applied to operate endoscopes, catheters or medical robots in patient's bodies with minimum invasion.

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To understand the effect of wall elasticity on pulsatile blood flow, the structure of physiological pulsatile flow was studied in a rigid and elastic aortic bifurcation models by means of a flow visualization technique. In both models, flow separation was observed at the lateral wall of bifurcation during the accelerated and decelerated flow periods ; secondary flow existed inside the flow separation. Although flow in the rigid model was strongly disturbed during the decelerated and back-flow periods, flow disturbances were minor in the elastic model. The scale of the flow separation zone was larger in the elastic model than in the rigid model. According to these results, wall elasticity reduces flow disturbances in aortic bifurcation, and possibly affects wall shear stress which is an important factor in atherogenesis.

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Numerical simulation has been performed for three-dimensional viscous flows within a passage relating to intricate artery structure, i. e. stenosed, branched and curved tubes. The numerical scheme employed is based upon Finite Volume Method adopting the QUICK or QUICKEST upwind code of MAC algorithm. The results for a stenosed tube were compared with flow visualization experiments, which showed an excellent agreement. Flow trace revealed a complex structure of separated and spiral fluid motion at branch. Unstable flows were observed in a curved tube, so that an attempt was made to formulate the enstrophy transfer equation for the analysis of vorticity fluctuation. The present results are encouraging enough to carry out further three-dimensional biofluid internal numerical flow simulations.

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In this paper, self-excited vibrations occurring in collapsible tubes are investigated on the basis of a lumped parameter model. The instability condition is theoretically derived and the unstable region is indicated, which almost coincides with that of the simplified model in the previous paper. It is shown that the collapsible tube system consists of two modes corresponding to the characteristic roots of the system, and that the higher frequency mode can be unstable but the lower frequency mode is always stable. The global behavior of the collapsible tube is numerically investigated.

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Simulation experiments in vitro related to flow through a vein and an airway of the lung were performed. The effect of longitudinal tension applied to thin-walled silicone rubber tubes on the relationship between the cross-sectional area of the tube and the transmural pressure, and on static and dynamic characteristic relationships between pressure drop and flowrate through the tube was investigated using five different kinds of specially designed tubes of same size with different applied longitudinal tensions. As a result, the following facts were clarified : By applying longitudinal tension to the tube, it became harder for the tube to be collapsed. Tube movement along the tube axis during the oscillation was restricted and the most largely collapsed portion shifted upstream. The amplitude of the oscillatory pressure drop was much larger than its time-averaged value. The time required for the tube to collapse gradually from a fully open state amounted to 80 to 85% of the period of the oscillation.

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A quasi-static model is assumed to be valid for volume change of the upstream half of the arterial segment under the cuff, according to our previous studies. The central portion of the segment is used for blood pressure measurement to avoid the effect of external pressure distribution of the artery. Based on the assumption and fluid dynamic consideration, cuff pressures corresponding to the start of volume fluctuation of the central artery under the cuff and blood flow resumption are adopted to elucidate approximate values of systolic arterial pressure. The cuff pressure corresponding to the maximum compliance of the artery segment is adopted to determine approximate values of diastolic pressure. The accuracy of these cuff pressure is examined analytically and in comparison with directly measured aortic blood pressures, and the values are shown to be reliable. Maximum compliance transmural pressure is known to be negative and to decrease with age.

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The motion of non-spherical suspended particles is analyzed by the Stokesian dynamics method using a dumbbell model. The precise prediction of the motion and interaction of cells in biological flows is required to design devices for cellular technology. Stokesian dynamics is a method for the simulation of a suspension of rigid micro spheres, which accounts for multiple body hydrodynamic interparticle interactions based on the Stokes equation. Many cells, however, are non-spherical, and each cell differs both in shape and size. In this study, we developed the Stokesian dynamics method for the dumbbells suspended in a fluid. The dumbbell consists of two rigid spheres of the same size connected by an infinitesimally thin rigid rod. The sedimenting processes of the high concentration region of particles are computed by this method. The structures of the wake in the dumbbell cases are completely different from those in the sphere cases. The formation of clusters, which are larger in size for dumbbell-like particles than spherical ones, is observed.

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The mechanism of arterial endothelial cell deformation and alignment was studied using a three-dimensional computational fluid mechanical model of the arteriolar wall with regularly arranged intraluminal undulation simulating endothelial cells. Endothelial cells were simulated using a 2D Gaussian distribution function, which had three parameters used to define the shape of the cells. They were the elongation factor, which is the correlation coefficient of the Gaussian distribution function, the height of the cells, and the cellular angle against the blood flow. The Navier-Stokes equations of the Newtonian fluid under steady flow conditions were solved using a finite volume method, and the absolute wall shear stress (WSS) at the summit of the cells was calculated. The WSS at the nuclear bulge varied in a complex manner, and the hypothesis that the endothelial cells change their shape and alignment to minimize the WSS at the nuclear bulge was presented to explain the computed results.

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The efficiency of axial dispersion of respiratory gases is improved by manipulating the flow wave form of oscillatory flow, e. g., the intermittent oscillatory flow, contributing to the advancement of ventilation by high-frequency oscillation (HFO). The purpose of this study was to investigate experimentally the effect of intermittent oscillatory flow on axial dispersion. An electromagnetic vibrator was installed at one end of a straight tube, via the bell mouth, with the inner diameter of 15. 6 mm and the total length of 4 m. Velocity was measured by a hot-film anemometer, and the concentration of carbon dioxide was measured by an infrared absorption CO₂ sensor. The effective diffusivity is dependent on the flow patterns, and the effective diffusivity increased significantly upon increasing the duration of stationary phase, with the maximum ratio of effective diffusivity to the molecular diffusivity double the that of sinusoidal oscillatory flow. Moreover, turbulence appears in the decelerating and stationary phase at high Reynolds numbers. In that case, the augmentation reached more than threefold. These results encourage effective use of intermittent oscillatory flow for ventilation by HFO.

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Axial dispersion in oscillatory flow is one of the important factors influencing the gas transport during HFO. Recently, the requirements for HFO have become diversified. The mucus clearance is one of the important steps for HFO. It was proven that the difference of flow rates between inspiration and expiration of oscillation was effective for mucus clearance. According to our latest study, the dispersion in an oscillatory flow can be improved by introducing a stationary period right after the diffusing particle experiences the largest movement, because of its lateral mixing effect during the stationary period. In this study, the numerical simulation of gas transport in an asymmetrical oscillatory laminar flow in a straight circular pipe was carried out for improvement of gas transport. The presence of the stationary period enhances axial gas transport in an asymmetrical oscillatory flow, and the maximum ratio of effective diffusivity to molecular diffusivity is double that of sinusoidal oscillatory flow.

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Magnetically suspended centrifugal blood pump has no valve and operates differently from pulsatile heart. Therefore, it is important to grasp the fluid transients in the cardiovascular system induced by the change of rotational speed of the pump. At first, unsteady characteristic of the pump was studied and unsteady factor was shown to be negligible at 1 Hz. Secondly step-wise change was given to the rotational speed of the pump in the Mock circulation, and the response in the Mock circulation was studied. On the characteristic curves of pumps and resistances the operating points shifted almost as expected. Moreover, from the corresponding variations observed in the flow rate and in the pressure at the inlet and outlet the compliances and resistances in the circulation were shown to be evaluated.

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When blood flow is partially blocked by external pressure, heat transport by blood flow is reduced proportionally to the blood flow rate. However, heat generated by metabolism is not reduced as that of the heat transport by blood flow because hemoglobin releases more oxygen to tissues due to the shift of the oxygen dissociation curve which is induced by changes in the tissue oxygen content, pH and temperature. The temperature variation of tissues subject to such reduction of blood flow rate is analyzed numerically using the Pennes' bio-heat equation. In the equation, the heat transport by blood flow and the metabolic heat generation are assumed to be proportional to the blood flow rate, and the metabolic heat generation is estimated from the existing oxygen dissociation curve. As the result, the difference between the decrease of heat transport by blood flow and that of oxygen release by hemoglobin has been found to result in the shift of the equilibrium tissue temperature to a higher temperature when the tissues are thermally insulated from outside.

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The paper is concerned with a model of the human body which is made from high molecular gel containing a nonionic surface active agent. The physical model is used to visualize thermal phenomena related to heat generation or heat transfer in the human body. The model shows good transparency below the specific temperature called the "clouding point". However, if temperature is increased as a result of absorbing energy, the region of elevated temperature becomes white and opaque due to segregation of the nonionic surface active agent. In this paper, a method used to develop the model that has the desired physical properties such as the clouding point, electric and thermal conductivity, viscoelasticity and other characteristics, is presented. The high molecular gel model should be useful for visualizing thermal phenomena in the human body.

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Time-resolved spectroscopy is expected to be developed for optical imaging of biological tissues which strongly scatter and weakly absorb light. It is strongly required to establish the temporal behaviors of the reflectance and/or transmittance of light impulses incident on such scattering and absorbing media. One of the analytical methods to solve the photon diffusion equation numerically is the finite element method (FEM). This paper reports the FEM results of temporal profiles of the transmittance of light impulses through scattering slabs and cylinders. Time courses of transmittances through homogeneously scattering and absorbing slabs are obtained by FEM and compared with those obtained by the Monte Carlo method which is believed to provide more accurate results with much longer computation time. The results of cylinders with homogeneous scattering and in-homogeneous absorption coefficients are also presented. Temporal variations of the cross-sectional profiles of the fluence rate generated by impulses incident on a surface are shown by contour plotting, and the effect of the location and size of the localized absorbing volume on the transmittances are discussed.

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Near-infrared light is promising for measuring oxygenation of living bodies. Understanding of photon migration through living bodies is necessary, because light is strongly scattered by biological tissues. Among various simulation methods, a Monte Carlo method is regarded to be accurate because it can simulate all the paths of photon migration in strongly scattering media. Picosecond time-resolved transmittance measurement has been carried out to validate the Monte Carlo simulation results. However, differences have been observed between the measured and the Monte Carlo results where the reflection at the cell interfaces was neglected. In this research, a Monte Carlo simulation with consideration of reflection at the cell interfaces is carried out. The results are compared with the results of the time-resolved measurement, and good agreement is observed.

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Three-component hydraulic models have been proposed to represent the energy flows during human exercise. These models were accompanied by sketches indicative of the graphical solution but had not been solved mathematically. The purpose of the present report is to extend the original model analysis of the bioenergetics based upon the theory of optimal control. In this hydraulic model, the Lohmann reaction is represented by the myocybernetic performance criterion which minimizes the integral of the time derivative of the ATP concentration deflection to a constant equilibrium level. According to the optimal control hypothesis, the bioenergetic system is formulated by 8-degree-of freedom ordinary differential equations. Qualitative comparisons between the predictions of the model and the findings that other experimental investigators indicate the the model reproduces the major features of the energy flows (i. e., ATP concentration, phosphocreatine reservoir, lactic acid concentration, and oxygen consumption).

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A three-dimensional transversely isotropic constitutive model of cardiac muscle is proposed. Stress in the cardiac muscle is first divided into the sum of passive and active parts. The passive part is represented by a strain energy density function of the exponential type, while the active part is formulated by introducing internal variables describing the degree of activation and the sarcomere length. The evolution equation of the activation parameter is established by taking account of excitation-contraction coupling. Comparison of the simulation results with those of experiments in the literature shows that the present model can describe qualitatively the mechanical properties of cardiac muscle.

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A numerical calculation method of dynamic motion analysis is used to predict the characteristics of pedaling performance during bicycle ergometry. For this analysis, a simulation model which has a 3-link mechanism and is driven by muscles at waist and knee joint, is proposed. A two element muscle model is considered, that is, one which involves the contractile component #(CC) and parallel elastic component #(PEC). Two types of monoarticular muscles and biarticular muscles are also considered in the model. This paper compares experimetal results and results of analysis of a bicycle ergometer, and clarifies bicycle ergonometer pedaling effects on CC characteristics and PEC characteristics of monoarticular muscles and biarticular muscles.

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An optimal control theory was applied for analysis of transportation of biological substances through a biological membrane. The performance function minimized the rate of change in the number of particles involved in each layer of the membrane. Rapid changes were manifested in the layer facing the outer boundary of the cell and inner surface. The effects of changes in the rate of absorption, desorption and transportation through each layer of the membrane evpanded to all of the layers composing the biological membrane. The present theory would be applicable for creating artificial biological membranes.

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This study aims at clarifying fundamenentally the influence of antifreeze proteins (AFPs) on the cryopreservation of biological cells. AFPs are antifreeze agents present in Antarctic fishes and some north-temperate fishes, which protect them from freezing. The process of directional solidification of suspensions of human red blood cells was investigated microscopically, using physiological saline including 20%v/v glycerol with and without 20mg/ml AFPs. The red blood cells after freezing and thawing were also observed. Due to the addition of AFPs, the morphology of the ice crystal growing in the suspension changed dramatically from dendritic into spicular. The spiculate ice crystal caused mechanically strong interactions between the ice crystals and the red blood cells, and the resultant complete destruction of the red blood cells. This result suggests that the morphology of the ice crystal and its interaction with the cells are among the factors influencing cell survival through freezing.

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The microscopic structure during directional solidification of human red blood cell suspensions with a hematocrit of 10% was investigated, using three different solutions : physiological saline, physiological saline with 20% v/v glycerol, and physiological saline with 20% v/v glycerol and 20mg/ml antifreeze proteins, and to understand the influence of hematocrit it was compared with the result for the hematocrit of 1% reported previously. The ice crystal structure and the ice-cell interaction were found to be different between the three solutions. This result is basically similar to that for the hematocrit of 1%. While the hematocrit of 1% rarely causes cell-cell interaction in all the solutions, the hematocrit of 10% remarkably causes cell-cell contacts and the resultant cell-cell interaction in physiological saline alone. These results show that the degree of cell-cell interaction depends upon the morphological characteristics of ice crystals, the manners of the ice-cell interaction, and the hematocrit strongly.

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This paper describes development of the shock tube for bio-tests (a non bursting-diaphragm-type double cylindrical shock tube with slit). The purpose of this apparatus is to execute bio-tests and the injury experiment of living tissues by shock waves. The device can generate a saw tooth pressure wave. The effect of slit on flow field in the shock tube is also confirmed by numerical simulation. Animal experiments show that injury of living tissue depend on maximum pressure and durauion time of exposure.

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This paper describes pressure wave analysis to examine effects of shock waves on living tissues. From the comparison of the displacement of the living Tissue model by FEM with that obtained by the experiment, the dynamic properties of the kidney are determined. Using these properties of the living tissues in the solid-state equation, the flow field in two layers that consist of air and living tissue, and that in three layers that consist of air, water, and living tissue is numerically obtained. It is found that gradient of pressure waves is living tissue is smaller than that of pressure wave in air and water. Hence, the effect of living tissue depends on the relaxation of pressure waves and duration time of exposure.

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In this paper, we apply stress stimulation to a rabbit's tibia under the same conditions as the previous paper using an improved apparatus in which the applied load is measured and controlled automatically by a personal computer. We apply not only compressive load but tensile load to the rabbit's tibia in order to clarify the difference in the influence on bone formation. The bone formation around the circular defect is estimated accurately by using a image processing technique. We discuss the relationship between the bone apposition and stress stimulation quantitatively from the experimental result. Furthermore, the computer simulation of the bone apposition in the experiment is carried out using an algorithm based on the theory of time-dependent bone remodeling proposed by Beaupre' et al. and the effectiveness of the theory is discussed compared with the experimental results.

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The effect of water discharge through a slit on cavitation suppression of a blade is studied experimentally. The slit is made vertically or obliquely to the suction surface and the position is at a distance of about a 10% chord from the leading edge. With increasing discharge rate, the length of the cavity on the suction surface becomes shorter and the vibration of blade and the noise become smaller. The observations by a high-speed video camera and by the pressure gauge buried in the blade surface show that the scale of unsteady behavior of cloud cavitation becomes small due to the water discharge. Moreover, the pressure on the suction surface becomes large due to the water discharge. It seems that this pressure increase contributes to the suppression of cavitation.

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Resonance behaviors of two-dimensional cavity flow around a rectangular cylinder, accompanied by severe vibration at some values of cavitation number, were experimentally studied by measuring the fluid dynamic forces and surface pressures, and by the flow visualization. The width-to-height ratio of the cylinder tested is 2.8, which is called the critical value. Periodic fluctuations of the surface pressure were investigated using a phase-averaging technique. Severe vibration occurs at a cavitation number, in which the fixed-type cavitation is formed in the separation bubble on the side surface and the surface pressure fluctuates during the time when a cloud of bubbles is shed from its cavity termination.

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In general, three-dimensional flow structures are observed in the Karman vortex street behind a circular cylinder when Reynolds number ≥ 200, and it is pointed out that three-dimensional analysis is necessary to simulate such flow structures. In this study, incompressible flow past a stationary circular cylinder at Reynolds number 1100 is computed by finite difference method, and the three dimensional computation shows good agreement with experimental values. Furthermore, a phenomenon that periodic lift and drag forces acting on a cylinder cause a beat frequency can be simulated. This phenomenon cannot be observed in the two-dimensional calculation, and the mechanism is explained on the basis of the relationship between the fluctuating fluid forces and the flow structures in the three-dimensional calculation.

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Near-wall bursting phenomena have been detected both by the VITA technique and by quadrant analysis. In addition to these detection schemes, visual burst detection has been performed in order to characterize the difference between VITA events and Q2 (second quadrant)events. It is shown that the yaw angle of visualized low-speed streaks for VITA events is greater than for Q2 events. Based on the experimental results and Euler equation, quasi-streamwise vortex models are proposed, and the results are compared with the experiments. Fluctuating velocity signals computed from the models are in good agreement with the experimental data for VITA events. Contour plots of the calculated streamwise velocity, spanwise vorticity and instantaneous Reynolds shear stress are presented. The generation processes of shear layer structures and Q2 and Q4 motions are shown.

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Assessment of subgrid-scale models in large eddy simulation was conducted by using direct numerical simulation data of a temporally developing turbulent mixing layer. The direct numerical simulation data which were used for comparison of subgrid-scale models were carefully calculated by means of a spectral method. In this paper, various models for SGS stresses were tested and we obtained the following conclusions. (1) In the turbulent mixing layer, the Smagorinsky model, the Bardina model and the GNS model predict the mean value of Raynolds stress terms very well, whereas the local structures of the Reynolds stress cannot be well represented by the models. Among the three models, the Bardina model predicts the local structure best. (2) As for the cross terms, the Bardina model shows high correlation with DNS data. (3) The dynamic eddy viscosity model for total SGS stress is capable of predicting very small stress which is close to the Reynolds stress term.

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An experimental study was conducted to investigate the effects of acoustic waves on the development of the turbulent statistics of a plane mixing layer using a novel experimental technique in a towing tunnel. The mixing layers were generated downstream from a splitter plate towed in a straight long tunnel. Acoustic forcing was applied to excite the shear layer and also to induce wave resonance in the free shear layer. The mixing layer large-scale structures/turbulent statistics in the transitional regime at Re_m ≈ 100 based on the momentum thickness were investigated by means of the visualization/flying hot-wire technique. We found that turbulent quantities of the spanwise velocity component were homogenized and reduced because of the subharmonic resonance. These results are close to the observations of simulated mixing layers at Re_m=112.

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The aim of this paper is to clarify the turbulence characteristics of the supersonic boundary layer which is reattaching downstream of a backward-facing step. The boundary layer flow was analyzed by a two-dimensional laser Doppler velocimeter and flow visualizations. The results showed that there was a higher level of momentum exchange between the reattaching boundary layer flow and the main supersonic stream than that of over a flat plate case. Numerical simulation was conducted in this flow field, and the results were compared with the experimental ones. It was clarified that the present CFD code exhibits good performance of simulation for the mean characteristics of flow field, and it was suggested that the improvement of the compressible turbulence model was needed.

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The present study deals with the unsteady characteristics of flow concerning flow-induced vibration due to fluid discharge over a flexible cylindrical weir, which occurred in the French demonstration fast breeder reactor, Super Phenix-1. The theoretical analysis of sloshing in a double cylindrical vessel and the drop of the free surface at the fall-in section and the numerical analysis of the inner flow were carried out. In the numerical analysis, unsteady and 2D inner flow with periodic vortex formation and shedding were simulated using the boundary element method and the discreet vortex method. As a result, it was obtained that the frequency of simulated unsteady flow was in good agreement with the natural frequency of sloshing, and the value of frequency converted into the case of the 1/5-scale test model of the Japanese demonstration FBR was about 6 Hz, which is near the frequency of the fluid elastic mode of unstable vibrations.

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In this paper, the effect of compressibility on the growth of a spatially developing plane free shear flow was studied for various values of the convective Mach number. The linear stability equations of compressible shear layers are solved using a direct spectral method. The mapped spectral method (mapped Fourier method) for the free shear flow of the unbounded boundary conditions was employed. Numerical results reveal that oblique modes (3-D modes) are significant in the mixing layer as the convective Mach number M_c increases. Above M_c = 0. 6, the most unstable modes are oblique waves. The unstable modes at M_c. = 0. 6 are found to be characterized by sobsonic and supersonic fast/slow waves. The fundamental eigenfunctions at M_c =0. 3 and M_c = 0. 6 are presented in this paper, whose profiles are affected by the magnitude of the convective Mach number. Finally, we find that the maximum growth rate of the spatial instability mode is approximately proportional to the Pitot-thickness growth rate obtained by Papamoschou and Roshko.

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A numerical method using the pseudo-compressibility method is applied to the analysis of the two-dimensional flow of power-law fluids. Based on the method of lines, the rational Runge -Kutta time integration scheme is combined with the central finite difference approximation for spacial discretization. The residual averaging is incorporated into the basic scheme in order to accelerate the convergence rate to a steady-state solution. The pseudo-compressibility parameter is adjusted corresponding to Reynolds number and computational grids so that the stability of computation can be significantly enhanced especially for low-Reynolds-number flow. Two kinds of 2 to 1 contraction flow through two-dimensional passages are analyzed with power indices 0.1 ≤ n ≤ 2.0, and at Reynolds number Re=100 and Re=0.01. The numerical results for velocity and pressure gradient profiles and for shear stress at the wall are in agreement with theoretical ones.

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For solution of dissipation energy minimization problems in a steady-state viscous flow field domain we applied the traction method that was proposed as a solution to domain optimization problems including a variation-constrained boundary in elliptic boundary value problems. Comparing this method to the mathematical programming method directly using the shape gradient function we can easily apply this method to domain optimization problems including the variation-constrained natural boundary. Also, we can easily implement this method with general-purpose FEM programs or BEM programs. We show the successful results of two-dimensional Stokes flow problems of a bending channel and a channel in which an isolated body exists.

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Based on the explanation of one dimensional draft tube surge induced by the cavitated vortex rope, i.e., it occurs when the rotating frequency of the vortex rope at the elbow portion coincides with the resonance frequency of the vibrating system of the draft tube with a cavitation region, we developed a theoretical method to predict the occurrence of severe pressure fluctuation. In the present study, a partially rolled-up vortex model was proposed to calculate the rotating frequency of the vortex rope, and a method was presented to estimate the cavitation volume in the draft tube, which is the main parameter to determine the resonance frequency of the vibrating system. The calculated and experimental results were compared, and reasonable agreement was obtained.

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This study is concerned with an underexpanded free jet flowing from an axisymmetric convergent nozzle and its impingement on a flat plate placed perpendicular to the jet axis. In the experiment, shadow photography was used to visualize the flow field and the sound pressure level of the noise generated in the jet was measured. As a result, the relation between the location and shape of the plate shock in the jet and the nozzle-plate spacing was established. Furthermore, we found how the sound pressure level of the noise changes with the jet structure, or the nozzle-plate spacing.

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An experimental study of pressure oscillation in a single vent tube due to vapor condensation into pool water was performed. The objectives of the work are to establish the character of the dominant frequency and the progression of the pressure wave in the condensation oscillation (CO) -chugging transition region, and to confirm the relationship between vapor velocity and pressure oscillation in chugging. In CO region, most of the pressure wave component had progressive character, and some, a stationary character of resonance in vent tube. In the CO-chugging transition region, the dominant frequency of the progressive wave component increased with vapor mass flow rate and water subcooling temperature. The effects of these parameters on the dominant frequency was explained well by a cylindrical bubble model. In chugging, the maximum vapor velocity was lower than that expected from a simulation model, and the pressure wave had no progressive component.

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A high-resolution finite difference method to simulate the gas-liquid two-phase flow is proposed taking account of the apparent compressibility which characterizes high -speed two -phase flow phenomena. The speed of sound and the total energy for the gas-liquid two-phase fluid flows are re-estimated based on the assumption of homogeneous and the thermodynamic relations. Here, the homogeneous two-phase flow model assuming a local equilibrium is adopted. The basic equations for the two-phase mixture flow similar to those of the ordinary single-phase compressible gas flow are solved using the upwind finite difference scheme based on the theory of characteristics. To elucidate the applicability of the present scheme, some numerical calculations of wet-steam nozzle flows with condensation were implemented. The calculated results are in good agreement with the existing experimental data.

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Evaporation of an argon liquid layer exposed in a vacuum is analyzed by the molecular dynamics method. The detailed structure of the liquid-vapor interface and angular distribution of evaporated molecules are examined and compared with the results based on the kinetic theory. In equilibrium, a thin transition layer in which density changes continuously appears between the two phases. Upon this density transition layer, another thin layer is found. In this layer, molecules interact with those in the liquid layer, and flow velocity changes quickly but continuously. The angular distribution of evaporated molecules, which is initially close to the cosine distribution, rapidly changes just above the interface because of the interaction among evaporated molecules ; they much prefer the normal direction.

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This numerical study focuses on optimization of the rotor geometry and influences of flow variation on the fuel distribution inside an LDISC (Low Pressure Direct Injection Stratified Charge)rotary engine system consisting of all three combustion chambers and both intake and exhaust port. A Chakraverthy third-order scheme devised in the numerical code has successfully solved the Compressible Navier-Stokes equations with binary diffusion between air and propane. Keeping the engine speed at 3000 rpm and without throttling, five cycles for one rotor geometry and one for another are calculated. The results show that one rotor geometry is quite favorable for stratification while the other is not, hence the choice of rotor shape is found to play a significant role in forming stratification. Although it is also observed that cycle-to-cycle variation of the flow fields often works against stratification, the paper concludes that an application of the LDISC to a rotary engine may extends it lean-limit dramatically.

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Safe conveyance of high-temperature molten materials is an essential facter for some advanced industries. The authors developed a new prototype pump for such applications. The pump utilized the pumping effect of a vibrating pipe system and featured a simple and novel configuration. Its structural and hydrodynamic features are different from those of previous conventional pumps. The pump structure constitutes a short vibrating pipe with a nonreturn valve, a long connecting rod and a cylindrical casing. It was driven by an air actuator. Tests were carried out with this prototype pump using high-temperature molten salt of 473 K to 673 K as a test fluid. Test results indicated that the air actuator was suitable to drive the pump and the pump performance was stable even at such high temperatures.

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An experimental study was made of air entrainment into water flowing downwards in a vertical pipe. The static pressure distributions along the pipe axis and the volocity distributions in a water layer formed on the wall of pipe were precisely measured to examine the behaviors of flows and air entrainment. The amount of air entrained through the water passage was also measured at the exit of the pipe, as the water flow rate was varied. Moreover, flow visualization was conducted to ascertain flow patterns in the pipe. The results obtained indicate that, with steady overflow being maintained, such flows as annular, mixing and bubbly flows are observed along a pipeline. Air entrainment takes place predominantly in annular flows adjacent to the wall of the pipe.

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Heat conduction analysis without heat generation under a steady state can be easily treated by the boundary element method. However, for the case with heat generation, a domain integral is necessary. This paper shows that the problem of steady heat conduction with heat generation can approximately be solved without the domain integral by the improved multiple-reciprocity boundary element method. The multiple-reciprocity boundary element method is not suitable for the complicated heat generation. In the improved multiple-reciprocity boundary element method, the domain integral in the each step is divided into point, line and area integrals. In order to solve the problem, the contour lines of heat generation, which approximate the actual heat generation, are used.

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Fully developed laminar forced convective heat transfer in a circular tube with internal longitudinal fins is analyzed by using the finite difference method under two kinds of thermal boundary conditions at the outer tube wall (i. e., constant wall temperatures and uniform heat fluxes). Extended Nusselt numbers based on the outer wall temperature are compared for a wide range of geometrical parameters and the following results are obtained : (1) For small values of the ratio of tube-material-to-fluid thermal conductivities heat transfer augmentation by fins is not effective. (2) When the thermal conductivity ratio lies in the order of 100, the effect of the wall thickness on the heat transfer coefficient can be neglected. Furthermore in the case that the ratio is greater than 500, the thermal resistance of the fin can be ignored in respect to the heat transfer.

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The present paper presents a numerical analysis of two-dimensional steady separated and reattached flow and heat transfer in a symmetrically enlarged channel. Of particular interest is asymmetric flow in a symmetric channel, which was experimentally observed even at very low Reynolds numbers. The details of local heat-transfer characteristics along with flow behaviors accompanying two different separated flow regions on two downstream walls are clarified. It is found that the present results predict the measured ones reanonably well. Local heat-transfer distributions on the two walls differ greatly and their profiles are extremely different from results for Symmetric flow.

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