This article presents a state-of-the-art review of flow and heat transfer characteristics in various liquid metal two-phase flows with and without magnetic field, paying particular attention to the flow regime map, local properties of two-phase flow such as phase distribution, bubble and slug velocity profile, film thickness, heat transfer characteristics in various flow regimes, and MHD effects on both fluid flow and heat transfer. In conclusion, remaining ambiguous and unsolved problems are pointed out in this article. Further studies are required to clarify and solve them through both theoretical and experimental approaches.

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Traveling bubble cavitation usually appears near the inception conditions of cavitation. During the violent collapse of the cavitation bubble a noise pulse is generated and this can be used to characterize the flow conditions. In this paper the scaling method developed by the first author is used to analyze the measurements of the number of pulse n_p generated in the center of a circular cylinder with/without a splitter plate. The scaling is done under the assumption of a characteristic process frequency F. By using the appropriate scaling relationship it is shown that the measurements from different test velocity and pressure will collapse into a single curve.

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The shape of the free surface and circulation velocity of a magnetic fluid induced by a rotating magnetic field were investigated. In the experiment, the shapes of the free surface were measured with an electrical contact probe, and the circulation velocity by the surface floating method. The deformation was increased with an increase in the strength of the applied current irrespective of the frequency. On the other hand, the induced flow velocity was almost proportional to that of the phase of the magnetic field. In the analyses, the shapes of the free surface were analyzed by a perturbation method neglecting the surface velocity and surface tension. The profiles of the rotational velocity were also calculated using Glazov's equation. The results agreed with the experimental ones and showed that the deformation was induced mainly by the radial gradient of the magnetic field and Maxwell's interfacial stress.

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Basic equations for micropolar fluids in an electromagnetic field have not been established yet. In this paper, relativistic electromagnetic interactions on micropolar fluids are investigated by electromagnetic exergy. We have obtained the results that electromagnetic momentum for micropolar fluid is well defined as g=D×B and an isotropic part of the Maxwellian stress tensor can be expressed by electromagnetic exergy. Then, as a result of thermodynamical consideration for micropolar fluids, Gibbs' relation for micropolar fluids equals that for nonpolar fluids. Using Onsagar's reciprocal theorem, the dissipative parts of the constitutive equations have been derived more generally and easily for micropolar fluids than theories previously presented.

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Laminar flow in the bends of a rectangular cross section is numerically simulated by a direct integration of the full Navier-Stokes equations. A detailed description of the flow near the entrance and the exit of the curved section is given based on t he numerical results for a strongly curved 90-degree square bend. The discrepancy between the experimentally visualized flow pattern and the actual flow field is also demonstrated, and the inclusion of the upstream history in the experiments is suggested. The numerical result of a 180-degree of aspect ratio 2 is compared with the recent LDV measurement. The agreement is quite reasonable.

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The secondary flow pattern was clarified experimentally by the visualization method for a fully developed pulsating flow through a circular curved pipe with a curvature ratio of 7.6. The experiments were carried out under the conditions of the Womersley numbers of α=5.5∼18, the mean Dean numbers of D^^-=90 and 200, and the flow rate ratios of η=0.5 and/or 1. Photographs were taken at four selected phase positions, i.e. Θ=0°, 90°, 180° and 270°. The instantaneous velocity profiles, the center of the vortices and the kinetic energy of the secondary flow were determined with the aid of the photographs and compared with the results obtained by the numerical analysis .For the experimental and analytical results, a discussion is given for the transition of the secondary flow patterns in a period and the effects of the Womersley number on the flow behavior.

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A series of measurements were made simultaneously by using arrays of hot-wire anemometers with X-probes. The data show the rows consisting of doughnut-type large-scale vortices and frequent pairing, which results in larger vortices. The interaction of these vortices beyond the jet centerline breaks the doughnut-type large-scale vortices and forms three-dimensional medium-sized and small-sized vortices. The flow is randomized through this process. Some large-scale vortices continue to pair and form the configuration of counterrotating vortices approximately alternating on opposite sides of the jet centerline in the region far from the nozzle.

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Developments of vortices behind a circular cylinder with its impulsive start were investigated by flow visualization techniques. Special attention was paid to elucidating the relation between the structure of vortices and the Reynolds number Re from the viewpoint of the convection of the vorticity generated on the surface of the cylinder. The structure of the vortices varies considerably with the Reynolds number immediately after the start of the cylinder for the duration τ<1∼1.5, where τ is the nondimensional elapsed time .For a high Reynolds number, the separated shear layers roll up close to the separation points and form intense vortices near the rear surface of the cylinder. For Re>3000, the separated vortices induce not only secondary vortices but also tertiary vortices near the separation points. After a duration of τ>1.5, the variation of the structure of the vortices with Re was found to be small. The ratio of the circulation to the area of vortex region has a nearly constant value.

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This paper deals with the hydraulic transient generated in the prefill line at the beginning of the compression cycle of a pull-down-type hydraulic machine press. Experiments were carried out on a small-sized simulation hydraulic circuit dynamically similar to a real machine of the 20-MN class. It was found that the four types of hydraulic transients, inclusive of the states which fell into poor operation, might be dependent on the system parameters. The following four topics of industrial interest were examined : (1) the limiting condition of occurrence of a column separation, (2) the cavitation duration following a column separation, (3) the surge pressure at the collapse of the first cavity, and (4) the cause of poor operation and the limiting condition of its occurrence. The values calculated from the proposed mathematical model agree with the measured values for these four topics with errors within about 10% over a wide range of operation.

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To obtain the best performance and optimum geometries for a wide range of diffuser geometries, experiments have been performed on many conical diffusers having uniform inlet flow outside the thin inlet boundary layer and free discharge using air flow. Performance data for diffusers are represented comprehensively in a pressure recovery coefficient and effectiveness chart including optimum geometry lines. A comparison of present results with those in references related to the problems shows that there is appreciable difference among the contours of the performance charts and optimum geometry lines obtained in different investigations conducted under similar inlet and outlet conditions .the present performance chart and optimum lines give approximately average values of the results obtained by other investigators. For geometries of cone angle 2α between 6.8 and 30 degrees, the effectiveness may be expressed with a fair degree of accuracy by the relationship η_p=1-0.0415α when the area ratio is larger than 3.

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A method of automatic recognition of the reversed flow region in a digitalized path-line picture has been proposed. Flow direction is locally determined by calculating the vorticity at an average position among four neighboring pathlines in four different ways. The input image needed in this method is only one path-line picture taken with standard camera equipment. In order to examine the accuracy, this method is applied to determine the flow directions in a separated flow around a circular cylinder, using the velocity distribution obtained numerically by the MAC method. It is found that only 2% error occurs in this case. As an application of the method to a flow visualization picture, a reversed flow region in a square cavity is recognized by the method, and the result is in good agreement with that of other experimental methods.

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A supersonic radial flow in a disk channel is studied. Under the high stagnation pressure condition, effects of both the stagnation pressure and the channel height on the radial static pressure distribution are investigated. The pressure recovery through the pseudoshock, its length, the velocity profile and the thickness of the boundary layer were also measured. The results have shown that the supersonic region extends downstream with the increase of the stagnation pressure. However, the transition from the supersonic flow to subsonic flow occurs at the region further upstream than that predicted by the normal shock relation. The pressure recovery through the pseudoshock is found to be lower compared to that of a normal shock, particularly at a high, free-stream Mach number. In addition, the axially asymmetric form of the pseudoshock was observed. Furthermore, the measured static pressure, velocity distribution and the boundary layer thickness at the supersonic region agree well with the results of the two-dimensional calculation.

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In multistage axial compressors used for gas turbine engines, it is important to understand unsteady behaviors such as surge and rotating stall. The purpose of this study is to develop a practical analytical method for both surge and rotating stall in axial compressors. In this paper, firstly, some characteristics of the unsteady phenomena in axial compressors derived from the measurements of test compressors are summarized. Secondly, a numerical method for the unsteady phenomena is described, assuming incompressible flow. A feature of the method is solving the fluid equations by Galerkin's method with the circumferential flow distortion expressed in the form of a high-order Fourier series. Finally, we examine the usefulness of the method, using some results from parameter-vary computations and comparisons with the measured results in a 3-stage test compressor.

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If air bubbles or solid particles are entrained in a pump, they will cause poor pump performance and erode the pump itself. This paper concerns theoretical estimations of three-dimensional movements of air bubbles and solid particles entrained in a mixed-flow pump. The particle movements were numerically determined by integrating the equations of motion of an air bubble or a solid particle on a water flow field, which were solved by a finite element method under assumptions of potential flow. Although the air bubbles substantially follow the water streamlines, their trajectories near the pressure surface of the impeller blades shift considerably towards the hub. The solid particles tend to move straight ahead irrespective of water streamline curvature, and they collide with the hub surface.

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When employing a wedge nozzle with the CO² gasdynamic laser (GDL), it is necessary to consider generating an oblique shock wave at the nozzle exit. The translational temperature of the gas increases behind the oblique shock wave. Therefore, the population inversion becomes extinct and the small-signal gain is decreased .The laser medium gas is reheated by passing through the oblique shock wave. In this paper, two-dimensional numerical simulation, which considers the influence of the oblique shock wave, is carried out. In the shock wave configuration, good agreement between the schlieren photograph and the result of the calculation is obtained. The experimental value of the small-signal gain coefficient agrees well with the calculated one.

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The cavity flow field of a supersonic flow CO chemical laser is simulated numerically and the effects of the nozzle boundary layers, the cavity boundary layers and the mixing process on the laser performance are studied. The thin shear layer approximation is applied to the mixing region and the resulting equations are solved by the Crank-Nicolson predictor-corrector method. The numerical results show that the development of the mixing layer in the downstream direction is very gradual. The small signal gain coefficient begins to decay at a location where the mixing layer is still a small portion of the total flow width. The predicted distributions of the averaged gain along the flow agree fairly well with the experiment. It is clearly demonstrated that the presence of the boundary layers and the magnitude of the wall catalysis play decisive roles in determining the laser performance.

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Numerical prediction has been made of the turbulent heat transfer in a fully developed turbulent pipe flow heated with a constant heat flux for a wide range of Prandtl and Reynolds numbers ; i.e., 10^-2<Pr<5×10⁴ and 10⁴<Re<10⁵. The improved k-ε turbulence model of Myong and Kasagi is employed with turbulent Prandtl number assumptions. It is demonstrated that the distribution of eddy diffusivity of momentum is of dominant importance to predict the turbulent heat transfer and also to evaluate the turbulent Prandtl number Pr_t. The effect of the Reynolds number on Pr_t is comparatively weak in the whole Pr range studied. In addition, Pr_t remains almost constant with the value near unity at Pr>0.5 and increases gradually with decreasing Pr at Pr«1. An empirical equation of Pr_t is proposed as a function of Pr over a wide practical Pr range.

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Owing to mislocating of a temperature prove, an accident occurred in which all the eels in a heated fish pond covered with vinyl sheeting died in one night. On the process to make clear the circumstances of the accident it was found that the room temperature inside the vinyl sheeting-covered housing is close to the water temperature of the heated pond and is not greatly influenced by the ambient temperature, and stays relatively high even on a cold night. In this paper, experimental results using an actual fish pond are firstly reported. Temperature changes of the heated water and the room air above the pond are shown with time as well as the outdoor air temperature in the case of continuous heat input. Secondly, a simple analytical model of the system is proposed for the relationship between the water, the room air and the outdoor air temperature. Finally, it is shown that the analytical results coincide very well with the experimental data.

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The paper reports on an experimental study of heat transfer to single drops of an R113+R114 mixture evaporating in a stagnant medium of hotter water under a pressure of 0.10 to 0.43 MPa. The variation of the instantaneous heat transfer coefficient during the evaporation process of each drop is found to be strongly dependent on the temperature difference and the pressure, but the heat transfer performance averaged over the whole evaporation process shows much weaker dependencies on these parameters. The results newly obtained with the mixture drops are discussed in comparison with those obtained with pure R113 drops in our previous work using the same experimental facilities.

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The effects of surface roughness and inclination on pool boiling heat transfer in saturated liquid helium at atmospheric pressure were experimentally established. It was found that the nucleate boiling heat transfer increased as the surface roughness increased. Furthermove, increasing the surface inclination increased the nucleate boiling heat transfer in the low heat flux region. The two-phase boundary-layer analysis of saturated film boiling was found to underestimate the heat transfer coefficient, but by modifying the heat transfer surface length, the effects of surface superheat and the surface inclination could be correctly predicted. The surface roughness does not affect the critical heat flux, but the surface orientation has a pronounced effect on it. The existing correlations predict the orientation dependency of the critical heat flux reasonably well. The temperature at the minimum-heat-flux is affected by neither the surface roughness nor the orientation.

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The two-dimensional, steady-state, laminar film boiling heat transfer from a horizontal circular plate facing downward to a stagnant saturated liquid is studied theoretically based on that the flow of vapor beneath the circular plate is induced by the hydrostatic pressure gradient due to the change in the vapor film thickness. In the present analysis, the effect of plate edge and contribution of radiation heat transfer are taken into account. The boundary-layer equations for the vapor film are solved by the integral method and the solution is obtained for water at atmospheric pressure. The vapor film thickness, coefficients of convection heat transfer and contribution of radiation heat transfer are examined. The present analysis is compared with the experimental data in terms of total wall heat flux.

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For thermal energy storage utilizing an aquifer, the selection of a suitable site is the most important process. Based on previous field experiments and analysis, further investigation to determine the most appropriate process for site selection has taken place. This paper reports the following : (1) a process for the selection of a site suitable for aquifer thermal energy storage ; (2) a proposal for a new method for determining the most suitable site in terms of values of the apparent thermal diffusivity of the aquifer. This model is based on the analytical results of temperature recovery in the well after a stepwise injection of warm water into the aquifer ; (3) the experimental results showed good agreement with those obtained from the method proposed above.

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A model of the reaction rate in a turbulent premixed flame, based on the local three eddy scales of turbulence (TEST reaction model), is proposed to predict time-averaged profiles of the velocity, temperature and species concentration in combustion systems dominated by intense turbulence. The fundamental features of the model consist of a combustion reaction in the dissipating eddies of the Kolmogorov scale, clinging on the surfaces of Taylor's microscale eddies, and flames propagating within the microscale eddies. The mixing and flame spread in a large-scale flow field are dominated by the length scale derived from the k-ε turbulence model.

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In order to confirm the performance and characteristics of plasma jet ignition quantitatively, combustion tests were carried out by varying the governing parameters of the plasma jet ignition. Three plasma cavities of 37, 75, and 170 mm³, two orifices with diameters of 1 and 2.5 mm, and three discharge energies of 0.3, 1.5, and 6.7 J were tested in two different types of combustion vessels with lean hydrogen-air mixtures at equivalence ratios of 0.3 and 0.4. From a series of tests, the combustion enhancement by the plasma jet ignition is revealed only in the initial stage of combustion. Then a comparing parameter for the performance of plasma jet ignition in its initial stage of combustion is proposed by comparing the pressure diagram of plasma jet ignition with that of conventional single-point center ignition. The performance and the characteristics of plasma jet ignition are revealed quantitatively by the comparing parameter.

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A single cylinder engine with the combustion chamber mounted on the piston was designed to allow visualization in the direction of the cylinder axis. By using this engine, the evaporating process of the fuel injected into the combustion chamber was observed. High-speed Schlieren, shadowgraph, and back-illuminated photographs were taken for detailed observation of the combustion chambers with a single hole injector and a swirl injector which have different atomization characteristics. The chamber with a single hole injector showed strong collision of the spray with the bottom of the chamber and fast evaporation. That with a swirl injector showed no evidence of such collision and relatively slow evaporation.

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