This paper describes a new mesh-free algorithm for computational fluid dynamics. The algorithm is based on the CIVA method, which is a CIP-type cubie interpolation technique formulated in volume / area coordinates with tetrahedron / triangle units and can be applied to mesh-free methods such as the gridless and particle methods. The CIVA-based mesh-free method will make it possible to simulate many types of problems involving complex geometries and complex phenomena with high accuracy, because the methods are based on a simple tetrahedron / triangle unit and can treat both resting and moving particles (computing points). To achieve high accuracy with the methods, however, it is important to evaluate particle movement correctly. Therefore an improved evaluation algorithm is also described in this paper.

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The geometry of flow patterns in numerically simulated compressible isotropic turbulent flows for high r.m.s. Mach numbers was studied using three-dimensional critical point theory. The solution trajectories for three first-order linear differential equations are used to classify the elementary three-dimensional flow patterns defined by instantaneous streamlines. Fluid motions characterized by high rates of kinetic energy dissipation and / or high enstrophy are of particular interest. It is found that motions corresponding to high rates of dissipation are characterized by a 3-D rate-of-strain topology which is of the saddle-saddle-unstable node type, similar to the compressible mixing layer. Fluid motions corresponding to a high rate of dilatation dissipation are characterized by a topology of the node-node-node type in particular. The influences of Mach number on the geometry of flow patterns are described.

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The fractal dimension on turbulent premixed flame based on HTA (Hyperbolic Tangent Approximation) model for fully developed turbulent field was evaluated. Main results are as follows : (1) The fractal dimension evaluated without flame stretch effect is 2.67. (2) The fractal dimension evaluated with flame stretch effect is 2.33. This value is in good agreement with experimental data.

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Velocity fluctuations in the near wake of an elliptic disk are analyzed by the wavelet transform with Morlet wavelet. The wavelet transform demonstrates two dominant periodic components in the velocity fluctuations. The periodic components, which correspond to an alternate vortex shedding in the minor plane and a meandering motion in the major plane, are found to have a low-frequency unsteadiness. The modulus of the wavelet transform reveals that the low-frequency unsteadiness has a central frequency of approximately one-fifth of the frequency of the corresponding periodic component in each plane. Moreover, the unsteadiness is in phase on both sides of the wake in the same plane but out of phase in the different planes. The unsteadiness is of large spatial extent in that the representative wavelength of the low-frequency unsteadiness is of the order of 30 minor diameters.

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This paper deals with an experimental study of a turbulent cylindrical wall jet with a front-facing step equipped at an arbitrary location on the cylindrical wall, in order to disturb the flow near the wall and to cantrol the thickness of the wall shear layer. This report is mainly concerned with our search for the effects on the separation and reattachment properties of the jet flow in the region before and after a step with various heights and locations. The variations in the static pressures on the cylindrical wall surface, jet half-widths and boundary layer thicknesses in the downstream direction were examined. The relationships among the separation point from the cylindrical wall, the reattachment point and the nozzle-step distance were obtained. The results were compared with those already obtained for an ordinary cylindrical wall jet without the step. Furthermore, the flow patterns in the x-y plane normal to the wall in the region before and after the step were visualized by an oil film method.

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The adoption of a ramp nozzle array in supersonic mixing chemical oxygen-iodine lasers is examined by simulating the mixing and reacting flow fields numerically. Then, the efficiency of the ramps in improving the resulting gain region is studied. The compressible Navier-Stokes equations with a detailed chemical kinetic model are solved using a full-implicit finite volume method. The numerical results show that streamwise vortices, which were not anticipated in the previous studies, are induced downstream of the base relief region of the ramp nozzle array and significantly accelerate the mixing and reaction. The contact surface between the reactant streams is stretched very rapidly due to the vortices, resulting in much higher laser performance.

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The direct simulation Monte Carlo method is applied to the study of supersonic jets through a thin orifice. The influence of roughness of the cell network and the number of molecules in a cell on the simulation results is examined. The structure of the jets can be characterized using the rarefaction parameter introduced by Muntz et al. (AIAA J., 1970). The temperature nonequilibrium between the directions parallel and normal to the jet axis is reproduced.

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Ducts containing a tube bundle undergo acoustic resonant vibration. It is considered that the acoustic vibration is a kind of forced vibration by means of Karman vortex. However, it will be more reasonable to think that the vibration is a kind of mutual excited vibration, because fluid dynamic force excites a sound pressure and the sound pressure also generates the new fluid dynamic force. Equation of motion of sound pressure was derived from the mutual excited mechanism with the unsteady fluid dynamic forces. It was revealed from the equation that the imaginary part of the fluid dynamic force acting on the tube bundle supplies the energy of sound and on the other hand, radiation of sound consumes the energy. By comparing the supplying and consuming energies, it became possible to calculate a boundary where the acoustic resonant vibration will occur. The mechanism of supplying and consuming energies is discussed in this paper.

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Pulsatile flow is a specific unsteady flow in which the resultant flow is composed of a mean component and a periodically varying time-dependent component. Oscillatory flow is a sub-branch of pulsatile flow with zero mean component. Pulsatile flows may appear in one of the flow regimes : laminar, transitional or turbulent. It this paper, the basic terminology and relationships for pulsatile flows are presented, based on published theoretical and experimental investigations to date. The available theory on laminar and transitional regimes is outlined. Although the primary purpose of the study is to determine the theory of pulsatile pipe flows, published papers on related flow fields are also reviewed.

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In this paper, the studies on turbulent pulsatile flows conducted up to now are presented as an extension of a previous paper dealing with laminar and transitional pulsatile flows. Turbulent boundary layer flows with a periodic free-stream, theoretical and experimental investigations on the structure of turbulent pulsatile flows, available classifications in turbulent pulsatile flows and both experimental and theoretical studies on frictional losses in turbulent pulsatile pipe flows are the basic headings discussed in the paper. Several basic gaps on the manner are determined and listed as further research topics.

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We developed an efficient numerical scheme to resolve the flow around a solid particle that is several times larger than the spacing of computational grid. The method was examined by applying it to the three-dimensional flow past a sphere in a uniform stream. For the case that the grid resolution is finer than 1 / 8 of particle diameter, out results agreed well with experiment up to Reynolds number 600. It evaluated exactly the momentum transfer due to pressure at the particle surface. The numerical error in the energy budget was less than 6% of the dissipation rate. Out method therefore has enough accuracy and efficiency to investigate the interaction between particle-induced eddies and fluid turbulence in particle-laden turbulent flows.

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The present work proposes simplified correlations between the turbulent structures of both phases so that the numerical simulation from first principles can be performed by using an Eulerian-Lagrangian approach. For the liquid phase, the conservation equations are solved by Eulerian approach. A Lagrangian, random walk approach is employed to determine the instantaneous velocities of gas bubbles, which are tracked by solving their equations of motion. The phasic distributions as well as mean and fluctuating flow fields are successfully predicted as compared to measurements. It is also found that turbulent properties of both phases are important to the phase distribution mechanism of two-phase bubbly flows. A correlation function is recommended to describe the relationship between the turbulent kinetic energies of the gas and liquid phases so that satisfactory prediction can be achieved.

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Ice formation phenomena as well as freeze-shut conditions of flowing water in an isothermally cooled parallel plate channel are examined. 4.6 wt% ethylene glycol solution is also used as a test fluid to compare the results with those of water. It is found that the thermal properties of ice formed in the solution flow are different from thhose of ice formed in water flow, and that a mushy ice formed in the solution at expanded flow regions significantly affects the freeze-shut conditions. The present analytical results for freeze-shut conditions of water as well as solution flows agree with the experimental data, and it is seen that the occurrence of freeze shut is more difficult in the case of 4.6 wt% ethylene glycol solution than in the case of water.

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A relatively simple device for cavitation testing was developed, with the view to investigating the mechanism of and effects of physical properties of liquids on cavitation. This device is based on the principle that a longitudinal stress wave is generated at one end of the cylindrical rod by an impact given at the other end, causing negative pressures and thus cavitation in the liquid surrounding the lower end of the rod. The results of the investigation can be summarized as follws : (1) By installing a cylinder around the testing rod, it is possible to suppress the generation of the ring cavitation and to realize a nearly one-dimensional pressure field under the bottom face of the testing rod ; (2) Decreasing the air content in the liquid can reduce cavitation inception pressures.

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In order to clear the mechanism of the vapor explosion, two kinds of experiments were performed. In the experiment 1, an upper side-open transparent vessel filled with molten metal (solder, tin, lead and zinc) was immersed in the water tank. It was found that vapor cavities were generated in the metal and the vapor bubble connected with a cavity collapsed just before the occurrence of a vapor explosion. In the experiment 2, the apparatus consists of a water tank and a heated vessel with a cavity. Subcooled water in the water tank flows into the vapor cavity, immediately after the pressure in cavity is abruptly reduced because of the vapor condensation. Then the pressure rises rapidly by the vaporization of water in the cavity. A chain of phenomena, the generation of vapor cavities, the pressure descent due to vapor collapse, the water inflow into the cavity, and the rapid pressure rise, can be a part of the process of vapor explosion. The relation between the metal temperature just before the occurrence of a vapor burst and the minimum film boiling temperature criterion of Dhir and Purohit was investigated.

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This paper describes a vortex structure at the inlet of an inducer which appears on the boundary of backflow region. The vortex structure was visualized by the cavitation voids found by operating at cavitation number of σ=0.050 and recorded by a high speed video. It was measured quantitatively by two laser displacement sensors. The passing frequency and the shape of vortex filaments were determined from the outputs of the laser displacement sensors which respond to the passage of the vortex cavitation. The results show that the number of vortex filaments, their propagation angular velocity and radial location depend on the steady velocity profile at the inlet.

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A three-dimensional linear analysis of rotating stall is carried out to clarify the effects of spanwise distribution of cascade characteristics. A semi-actuator disk model of annular cascade is employed. Linear spanwise distributions of the local performance slope are considered to examine the effects of the three-dimensionality in the cascade characteristics. Many eigenvalues were found corresponding to various kinds of radial mode. It was found that the 0th order radial mode is more unstable than higher order modes. It was also found that uneven spanwise distribution of cascade characteristics makes the 0th mode more unstable, and makes the amplitude of the disturbance larger at radial locations where the positive slope of the performance is larger.

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Passenger car torque converters have been designed with an increasingly lower profile in recent years for the purpose of achieving weight savings and a more compact size. However, flatter designs have tended to result in reduced hydrodynamic performance. The major cause of this performance deterioration is the pump, where relatively higher loss occurs at the core and suction surfaces. In this study, the internal flow characteristics of four torque converters having pump impeller passages with different contraction ratios were investigated numerically using a CFD code. The results show that there existed an optimum contraction ratio of the pump meridional passage in terms of efficiency. The four torque converters were then manufactured and tested in order to evaluate the change in their overall performance relative to the contraction ratio. The measured overall efficiency and visualized flow patterns tended to coincide well with the computation results.

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Detailed measurements in the flow behind a highly forward-swept axial-flow fan at three operating conditions were performed using three-dimensional LDV system. Various phenomena related to the leakage flow, leakage vortex, hub vortex and wake were investigated. At the design condition, where no distinct leakage vortex appears behind trailing edge, the leakage flow interacts with the boundary layer of the pressure side inside the blade passage, which directly influence the wake characteristics behind the trailing edge. At the low loading condition, the leakage vortex has the characteristics of the velocity defect and this vortex induces radially inward flows at both the suction and pressure sides in the wake near the tip region. As the loading increases, radially-outward velocity component increases and the position of the maximum value in the wake is closer to the tip region. At the design and high loading condition, hub vortex induces radially inward flow at the pressure side and wakes near the hub region decays very quickly due to the interaction with the large hub vortex.

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When a coiled pipe rotates about the coil axis, the fluid flowing in it is subjected to both Coriolis and centrifugal forces. These combined effects complicate the flow characteristics beyond those seen in stationary curved pipes. Following a previous paper on the flow characteristics, a combined theoretical and numerical study on forced convective heat transfer is made for a fully developed laminar flow in rotating curved pipes. The similarity analysis reveals that convective heat transfer in loosely-coiled rotating pipes is characterized by four parameters : the Dean number K_LC, the body force ratio F, the Rossby number Ro and the Prandtl number Pr. The Prandtl number determines the sensitivity of heat transfer to the secondary flow ; limiting behaviours of the temperature field are discussed for various Pr based on the dimensionless energy equation. The variations of temperature structure with K_LC, F and Pr are shown, and the effect of Ro on heat transfer is described. Semi-empirical formulae for average heat transfer rate are given for a wide range of these parameters by using a new dimensionless variable.

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In order to examine the effect of entrance and exit areas on the velocity distribution in stacked wire screens, which are the most familiar regenerator matrices of Stirling cycle machines, the pressure drop across them and the velocity distribution at their exit are measured for different mesh numbers, flow rates, entrance areas, exit areas and stack thicknesses. The results show that the effective flow area ratio, which is an index for the uniformity of the velocity, is independent of the mesh number and the Reynolds number but dependent on the entrance and exit areas and the stack thickness. In addition, a simple theoretical flow model has been formulated based on the isotropy of the friction factor, which is confirmed by the measurement of axial and radial friction factors. The calculation using this model gives an effective flow area ratio and a velocity distribution that agree well with experimental ones.

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This paper describes the numerical simulation of a GM refrigerator operating at about 4 K. The simulation model is composed of a regenerator, an expansion space, and a cooling stage. The volumetric change of the expansion space and the actual thermophysical properties of the working fluid, helium are considered. The basic equations are mode up of one-dimensional fluid equations and an energy equation of the regenerator material and the cooling stage. The fluid equations are expressed in the general coordinate system of which a coordinate axis moves with time to take account of the volumetric change of the expansion space. These basic equations are differentiated by using the TVD MacCormack method. In order to verify the simulation model, the theoretical validity of the calculation results was checked and calculation results were compared with results of experiments. As a result it was confirmed that the simulation model is appropriate.

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This research focused on the light emission behavior of the OH radical (characteristic spectrum of 306.4[nm]) that plays a key role in combustion reactions, in order to investigate the influence of the residual gas on autoignition. The test engine used was a 2-stroke, air-cooled engine fitted with an exhaust pressure control valve in the exhaust manifold. Raising the exhaust pressure forcibly recirculated more exhaust gas internally. Emission measurements were made under three conditions : normal combustion without any forced application of internal EGR, forced application of light internal EGR and forced application of heavy EGR. When a certain level of internal EGR is forcibly applied, the temperature of the unburned end gas is raised on accout of heat transfer from the hot residual gas and also due to compression by piston motion. As a result, the unburned end gas becomes active and autoignition tends to occur.

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The existence of two distinctly different combustion regimes are shown by the extinction limit. The effective Karlovitz number KaS was proposed to predict extinction. Using measured data, coming from the counterflow laminar flames, the laminar flame thickness and burning velocity were assessed. This flame thickness is much larger than the Zel'dovich characteristic length. Four different calculation methods of extinction Karlovitz number were presented. At the state of extinction of laminar flame, the effective Karlovitz number ranged around unity. On the other hand, in the opposed jet burner, impinging jets produce a strong tufbulence with small scale. In this burner, a stable annular turbulent flame is established at the stretch rate of 20 times greater than that of the laminar flame extinction. Although the distributed reaction zone is produced by extremely small scale eddies compared to the laminar flame thickness, there remains unclear how the transition occurs from the wrinkled laminar flame to the distributed reaction zone. In the present paper, a new model that includes the real flame property was suggested.

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A combustion chamber partially coated with ZrO₂ / Ni functionally graded materials (FGM) was cyclically tested, using a bipropellant of nitrogen tetroxide (NTO) / monomethyl hydrazine (MMH) at a chamber pressure (P_C) of 0.9 MPa, to show the effect of such coatings on the life span of the chamber. This thermal barrier coatings were applied using a process that employed the electroforming method. The C^* efficiency (ηC^*) for the durability tests of the partially ZrO₂ / Ni FGM-coated chamber was 97% at P_C=0.9 MPa and mixture ratio (MR) of NTO / MMH=1.65. At the cylindrical section of the chamber, the thermal barrier coating subsequent to composed of pure ZrO₂ remained partially intact. However, the inner surface coating of the chamber throat section suffered premature delamination. The typical damage mode observed in a carbon fiber-reinforced carbon matrix (C / C) chamber of a bipropellant engine in our previous study was also seen near the injector face. In the cycle durability tests, the damage to the coating was inspected by means of the Replica method. After a total of 260 firing tests, a profile of the coating damage was obtained by means of a computer-aided micro-analyzer (CMA) system.

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Linear stability analysis was carried out for a hydrocarbon liquid fuel jet (n-butane) that was issued into a stagnant gas (nitrogen) whose pressure and temperature exceeded the thermal critical values of the fuel. Within this high pressure / high temperature environment, the liquid fuel jet undergoes sub-to-supercritical transition due to heat addition, changes the method of mass transfer at the gas-liquid interface, and loses surface tension. As a result, we obtained two types of flow instabilities : one is the Rayleigh type and the other is the Taylor type. We numerically calculated the maximum amplification rate of the Rayleigh-type instability, which depends on the square root of the Weber number and the thermodynamic phenomena, such as phase equilibrium and evaporation. Calculation results showed that fluid dynamic and thermal processes are highly coupled ; therefore, the fuel jet instabilities in a supercritical environment are strongly affected by thermodynaamic conditions and physical properties.

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In this study, a method for two-dimensional temperature measurement based on O₂-LIPF (laser-induced predissociative fluorescence) using a broad band ArF excimer laser is proposed. In this method, temperature is measured by the use of temperature dependence of ratios between fluorescence intensities integrated in two spectral region including peaks. To reduce the measurement time and improve the measurement accuracy, we develop a stereo-viewer, which can put two images passed through two different filters on a picture frame. This technique is applied to heated air jet, and radial temperature profile at x / D=6(x:distance from nozzle; D:nozzle diameter) is compared with that obtained with a thermocouple. Two-dimensional temperature image of the jet is also measured successfully.

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The stability of a magnetically levitated nonmagnetic liquid column in a magnetic fluid and a nonuniform magnetic field is studied theoretically and experimentally. The angular velocity equation of the interfacial wave is derived by assuming that (1) the fluids are inviscid, (2) the undisturbed interface between the levitated fluid and the surrounding fluid is an infinitely long cylindrical surface, (3) the amplitudes of the disturbances are very small, and (4) the magnetic susceptibility of each fluid is much smaller than 1. The stable conditions of different modes are discussed. The experimental study is performed with two very long magnetic north poles set face to face to form the nonuniform magnetic field, using water as the levitated fluid and a diluted oil-base magnetic fluid as the surrounding fluid.

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The critical osmotic pressure that can be endured by biological cells is measured. Optimal parameters of the freezing process as well as the prefreezing process are restricted by the critical osmotic pressure, which can be translated into the critical normalized volume of the cell. Viability of the cells is measured after the cells are exposed to a certain osmotic pressure, and the viability can be estimated from the viewpoint of biophysical functions. In this study, endothelial cells and smooth muscle cells comprising porcine arteries are selected as samples. The viability of endothelial cells is estimated by a dye-exclusion test, and that of smooth muscle cells is estimated by measuring the contraction-relaxation rate. Optimal parameters of the freezing process as well as the prefreezing process can be obtained by estimating the normalized volume of the cell. The critical normalized volume of cells can be estimated from the measured critical osmotic pressure.

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