The effect of the locations of pseudo-shock waves on the oscillations of pseudo-shock waves in a straight rectangular duct when the flows are choked at the duct exits has been experimentally investigated using high-speed schlieren films. The results show ; (1) the λ-type pseudo-shock wave which is produced at the upstream side of the duct oscillates with a small amplitude of 0.2D and low frequency (below 40 Hz), where D=50 mm is the width of the duct. (2) the X-type pseudo-shock wave which is produced at the downstream side oscillates with an amplitude of 0.3D and with frequencies below about 70HZ and high frequencies of 150 to 250 Hz. (3) The cause of the λ-type pseudo-shock wave oscillation is the boundary layer thickness oscillation in the pseudo-shock wave.

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In this paper the oscillations of pseudo-shock waves in a straight rectangular duct when the flows are choked at the duct exit have been investigated by wall pressure fluctuation measurements at five measuring points along the duct. The pressure signals are statistically analysed using a micro computer. The results show ; (1) The wall pressure at the first shock of a λ-type pseudo-shock wave oscillates with an amplitude of 0.35ΔP_psw and low frequencies below 40 Hz, where ΔP_psw is the whole pressure rise due to a pseudo-shock wave. (2) The wall pressure at the first shock of an X-type pseudo-shock wave oscillates with an amplitude of 0.5 to 0.6ΔP_psw and with low frequencies below 100 Hz and high frequencies of 150 to 250 Hz. (3) The wall pressure fluctuations in pseudo-shock waves are always induced by the pseudo-shock wave oscillations. (4) The frequencies of the pseudo-shock wave oscillations obtained experimentally are nearly the same as those of the oscillations of air columns in straight ducts behind the pseudo-shock waves.

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In a flow of solid-particle/water mixture in a circular pipe with a 77 mm diameter, the concentration of particles was varied continuously. The flow rate, the hydraulic gradient and the solid fraction were measured. Two kinds of plastic-beads with different densities and sizes were used as the sample. The conclusions are summarized as follows. (1) The pressure loss reduction effect due to the mixing of particles can be caused whether the density of particles is greater or smaller than that of water. (2) The reduction ratio of the hydraulic gradient is represented roughly as a function of the relative solid fraction and the Froude number F_d referring to the particle size. (3) The pressure loss reduction effect occurs when F_d>2000, and the maximum reduction ratio attained in this work is about 7%.

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Equations of motion of solid particles in a pump impeller having a low specific speed were solved numerically with assumptions of an inviscid and incompressible three dimensional potential flow, and the general movement of solid particles in the pump was clarified. The trajectories of the sand particles and manganese ores, with diameters ranging from 1 mm to 5 mm were obtained for different flow capacities. The locations and the velocities with which the particles impinge on the boundary surface of the pump were also discussed in order to estimate the erosion damage in pumps.

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Limitation of countercurrent gas-liquid flow has been investigated in horizontal flow path (HFP) connected to inclined flow path (IFP). The envelope model was applied to predict the gas velocity on initiation of liquid penetration from HFP to lower tank. The gas velocity and void fraction at dominant limitation (DL) could be predicted well for different scales of flow path by the model, using the following interfacial friction factor. That was 0.021 as average in HFP in the case where DL existed in HFP near the bend connecting HFP with IFP and 0.5 at DL in the case where DL existed in IFP near the bend.

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A water-channel experiment has been performed on the concentration in a recirculating region behind a backward-facing step. A plume of matter was issued from a circular hole on the surface located in the recirculating region. An optical-fiber probe was employed to measure fluctuating concentrations at a Reynolds number (based on the step height and the mainstream velocity) of 1250. The time-mean concentration in the recirculating region was found to be strongly dependent on the ratio of the effluent velocity and the mainstream velocity. When released matters are harmful or toxic, not only the time-mean concentration but the instantaneous concentration should be predicted. In order to meet this need, spatial distributions of the probability of finding a concentration higher than a particular value and the time when such concentration first appears at a given position are also presented and discussed.

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The flow around a permeable square plate, normal to a stream, standing vertically against the flat wall on which the turbulent boundary layer was developing was investigated experimentally. The velocity profile of the wake, the vortex shedding from the permeable plate and the surface pressure distribution on both the plate and the fiat wall were measured for a permeable plate with various open area ratios. The profiles of wake velocity vectors and the flow visualization by both oil-film and smoke-wire techniques clarified that the circulation region behind the permeable plate was moved downstream by the bleed flow with increasing open area ratio, and that the circulation region disappeared for a large open area ratio. The vortex shedding can be found for the permeable plate with a small open area ratio. In addition, the drag coefficient shows a significant change at an open area ratio of about 0.2.

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An experiment was carried out on the aerodynamic characteristics of a circular cylinder with tangential blowing for various blowing positions. In the case that the blowing position is in the separated region, the separated shear layer is forced to reattach to the cylinder surface by the suction effect of the blowing jet. The reattachment takes place suddenly at a certain intensity of the jet depending on the blowing position and results in a discontinuous change of the aerodynamic characteristics. The forced reattachment is effectively promoted by increasing the Reynolds number and the intensity of turbulence in the case of a laminar shear layer but is independent of them in the case of a turbulent shear layer.

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In the present paper, the wall shear stress in a pulsating flow through a two dimensional stenosed channel has been studied. In the experiment, the wall shear stress behind the stenosis is measured by the electrochemical method. The measurement is conducted at a Reynolds number of 160, a non-dimensional frequency of 3.40 and a flow amplitude of 0.3 The wall shear stress is numerically estimated by calculating the continuity equation and the vorticity transferred equation. In steady flow, the wall shear stress behind the stenosis is a maximum at the upstream region of the reattaching point. In pulsating flow, the time variation of the wall shear stress is a maximum at the reattaching point corresponding to the steady flow. Consequently, it is clarified that the deterioration of an arterial wall with a stenosis is remarkably accelerated near the reattaching point corresponding to the steady flow.

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In the previous report, it was experimentally observed that liquid rising could occur in a suction pipeline containing an abrupt enlargement. However, the characteristics of liquid rising in such suction pipelines could not be estimated theoretically. The objective of the present study is to predict the characteristics of liquid rising theoretically. An advanced three dimensional theory based on pressure correct and additional mass has been developed. The experimental investigation of suction pipelines containing an abrupt contraction also has been made. Experimental results gave good agreement with the theoretical analysis.

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The effects of nonlinearity on unsteady force in two-dimensional potential flow are studied. The nonlinearities of airfoil thickness, camber and angle of attack have the effect to retarding the build-up of lift, whereas the wake-deformation has an opposite effect. The thickness and camber also have the effect of increasing the force of apparent mass which is proportional to the acceleration of the flow. The general formula to obtain the initial lift and drag of impulsively started airfoils of arbitrary-shape is derived and in the case of Joukowski airfoils, the solution is compared with Chow and Huang's approximate solution, which is valid when the camber is slight and angle of attack is small.

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Experimental studies are conducted to develop a method of predicting the pressure losses in multi-blade blowers. A loss model in constructed for the losses in the impeller and the losses. in the scroll separately. The losses in the impeller are supposed to consist of shock loss, separation loss, curvature loss, skin friction loss and mixing loss. On the other hand, the losses in the scroll are supposed to consist of shock loss of radial and peripheral directions, and skin friction loss. For the maximum efficiency flow, separation loss and shock loss are great at the impeller, and shock loss of radial direction and skin friction loss are great at the scroll. Those pressure losses in the scroll have tendency to increase remarkably with the increase of flow.

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Pressure and flow ripples of a variable displacement vane pump with a pressure compensator were experimentally studied. Experiments were carried out under a lock condition where a cam ring was fixed and an unlock condition where the ring was supported with a spring of a compensator. The effect of rotating speed, averaged eccentricity of the cam ring and averaged discharge pressure on the pressure ripple were examined, based on the results of Fourier analysis of pressure data, and we measured the pressure variation of a pumping chamber. eccentricity, reaction force on a cam ring and discharge flow rates, using a hot-wire anemometer.

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Pressure and flow ripples of a variable displacement vane pump with a pressure compensator were theoretically analyzed by numerical calculations. The variations of the leakages were clarified in a detail. It was proved that the apparent leakages due to a fluid compressibility affect definitely the ripples of pressure and flow of both compression and expansion processes of a confined displacement chamber, and that the time-variation curve of the pressure and the bulk modulus in the chamber are dominant factors.

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Static characteristics of a new type poppet valve which has series restriction chokes are studied analytically and experimentally. It has been definitely shown that the valve has the valuable characteristic for a proportional control, that is, the lift of the poppet and the total flow rate are proportional to the opening of a pilot valve. The influence of the load pressure on the flow rate can be reduced by the newly presented "Area Compensation Method". The new type poppet valve is available for a proportionally and remotely controllable element in a hydraulic system.

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In this series of studies, so far, transient response solutions have been investigated for various line systems. These analysis, however, were always made under one of the extreme conditions of the pipe-end such as closed-end or open-end. Under an extreme condition like this, the value of the wave reflection coefficient which is estimated for the pipe-end usually takes a real number 1 or -1, for example. On the other hand, the corresponding value for an actual line system, which is connected with a hydraulic-cylinder or motor, takes a complex number. Load systems of this kind, basically, can be modeled by a mass-spring system. In this paper, therefore, an analysis is made for a line system with a mass-spring load, and a transient response solution is derived by practicing inverse Laplace transformation in terms of Laplace transformation pairs. To show the validity of the solution, calculated results are compared with the ones obtained with a digital simulation method.

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Systems to control the rotational speed of a Savonius-type wind turbine and to allow the Savonius rotor to stop the rotation in a strong wind are presented. It is known that the performances of a Savonius rotor changes greatly by varying the location of a deflecting plate which is placed in front of the rotor. The output of the rotor increases when the deflecting plate is located at an optimum place, while the rotor torque becomes nearly zero when the plate is located just in front of the rotor. Hence, in this work, the rotational speed of the Savonius rotor is controlled by turning the deflecting plate around the rotor. As the device to let the deflecting plate turn around the rotor, tail wings are used at first, and then, electronic devices, that is, an A/D converter, personal computer and a stepping motor are applied to control the rotational speed of the rotor more precisely than the control by the tail wings.

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Heat exchangers consisting of finned tubes are commonly employed in air conditioning systems. which are used at low Reynolds number because of the needs of low noise, saving energy, etc. The effect of the construction of the heat exchanger on the heat transfer and friction characteristics was reported in the former reports. In the present work, the row by row performance of single-and multi-row tube and plate fin heat exchangers was evaluated. Their performance is dominated by three regions : a developing flow region for the first row, a transition region for the second row and a vortex region for the downstream row from the third row. For each region, dimensionless equations on the performance were obtained and a generalized correlation was obtained.

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A new proposal for closing the energy equation is presented at the two-equation level of turbulence modelling. The eddy diffusivity concept is used in modelling. However, just as the eddy viscosity is determined from solutions of the k- and ε-equations, so the eddy diffusivity for heat is given as functions of temperature variance, <t²>^^-, and the dissipation rate of temperature fluctuations, ε_t, together with k and ε. Thus, the proposed model does not require any questionable assumptions for the "turbulent Prandtl number". Modelled forms of the <t²>^^-- and ε_t-equations are developed to account for the physical effects of molecular Prandtl number and near-wall turbulence. The model is tested by application to a flat plate boundary layer, the thermal entrance region of a pipe, and the turbulent heat transfer in fluids over a wide range of the Prandtl number. Agreement with experiment is generally very satisfactory.

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This paper presents experimental results on the real value of the minimum-heat-flux (MHF) -point temperature for subcooled pool boiling of water from a horizontal cylinder and an advanced form of the correlation for subcooled film-boiling heat-transfer proposed in the previous paper. First, experiments to observe the collapse process of film boiling were conducted by using a high speed video. The experimental results show that the collapse mode is classified into the propagative collapse with a precursory local-collapse and the coherent collapse. Second, the propagation velocity of collapse front and the mean surface temperature upon the local collapse followed by the propagative collapse were measured. The experimental results show that, for higher propagation-velocities, the MHF-point temperature decreases and approaches the value upon coherent collapse which has only a slight dependence on liquid subcooling. Finally, an advanced form of the correlation for subcooled film-boiling heat-transfer reported in the previous paper is proposed. This equation is in good agreement with the present data of of water at subatmospheric pressures and the existing data of liquid sodium and freon R-11 at atmospheric pressure and pressurized water.

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An experimental study has been made of saturated boiling heat transfer for water and R 113 in a narrow vertical rectangular channel (2 mm space, 20 mm wide, and 200 mm long) at atmospheric pressure, in which the vertical heated surface (10 mm long, 20 mm wide) is located on one side at a position 150 mm from the entrance and bubbles are forcibly passed through it at designated period of 0.033 to 1.0 sec. The experiment shows that the heat transfer coefficients are increased by the bubble passing through the heated surface for the value of thermal diffusivity, a, times period, T₀, of the passing bubble above about 6×10^-9 m² (aT₀<6×10^-9), while for aT₀<6×10^>-9>m², the heat transfer coefficients become independent of the period.

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In order to study the mechanism of critical heat flux of pool boiling, measurement of heat flux fluctuation and high speed photographic observation were carried out simultaneously on a constant temperature surface heated by electrically controlled Joule heating, in the vicinity of a critical heat flux point. They revealed the following : (1) when the surface is covered by a coalesced bubble, heat flux begins to increase because evaporation is enhanced ; (2) heat flux begins to decrease either while the surface is covered by a coalesced bubble due to dryout of the liquid on the surface, or just after nucleation begins under the rising bubble due to a relatively low heat transfer rate of nucleation ; and (3) heat applied from the time the surface is covered by a bubble until the time heat flux begins to ducrease does not vary widely and corresponds to latent heat of liquid about 11 -μm thick.

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This paper treats laminar film condensation of vapours in the subcritical region. The similarity solusions for gravity controlled condensation of pure vapours of water and carbon dioxide on a vertical plate are numerically obtained. The effects of small latent heat, low ρ-μ ratio and high Prandtl number on the boundary values, temperature distribution in the liquid film and velocity distribution in the boundary layer are revealed. The dimensionless expressions for the heat transfer coefficient and the condensate mass flux are derived, which contain the characteristics of Nusselt's theory as a special case. When the reduced temperature of the vapour approaches unity and the temperature difference between vapour and wall is large, the effect of the convection term in the liquid film appears markedly and the heat transfer coefficient becomes independent of H, but depends on Gr_Lx and Pr_L.

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The steady laminar free convection flow around a uniformly heated circular cylinder which is placed horizontally in an infinitely extended incompressible fluid otherwise at rest is numerically investigated at high Grashof numbers. The Boussinesq approximation is assumed and the fluid flow with Pr=0.72 is calculated for Gr_d=8×10⁵, 8×10⁶ and 8×10⁷ using Leonard's difference approximation scheme, where Pr is the Prandtl number and Gr_d the Grashof number based on the diameter of the circular cylinder and the temperature difference from the surrounding fluid. From the calculated result the flow separation bubble present at the upper stagnation point is observed to gradually extend as the Grashof number increases. Corresponding values of the Nusselt number are also evaluated and are found to be consistent with those given by existing empirical formulas.

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The unsteady streamwise pseudo-vortical motion model developed by Kasagi et al. (1985) is used in a numerical analysis of the turbulent heat transfer near the wall for various Prandtl-number fluids under the wall boundary conditions of constant heat flux and constant temperature. Unlike the typical methodology based on Reynolds decomposition, the algebraic expressions of three fiuctuating velocities given by the model are directly introduced into the governing energy equation. From the numerical solution of the unsteady thermal field, the near-wall behavior of statistical quantities is obtained. Both the predicted turbulent heat flux and turbulent Prandtl number are appreciably dependent upon the Prandtl number under the strong influence of the prescribed wall boundary condition. In addition, the production and diffusion of temperature fluctuation associated with coherent turbulence structure are calculated and are qualitatively in good agreement with the experiment.

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The flow and heat transfer characteristics of pooled water with a supercooled region have been studied experimentally using a real-time holographic interferometry technique. Pure water initially at room temperature (293.15 K) in a rectangular container is cooled on the top or bottom until the release of supercooling. The time-dependent sequential flow patterns and heat transfer of natural convection have been obtained for cases, where cooling is effected both below and above, using test containers of various heights. Furthermore, the factors affecting the release of supercooling are investigated taking into full consideration the influences of cooling wall conditions, the degree of supercooling and the heat transfer characteristics evaluated by Nusselt numbers. As a result, it is clarified that the turbulence induced by the bulk convective flow is considered to be highly important, in addition to the existence of bulk flow.

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Particle sizing and characterization in hot air streaming were studied by using a particle sizer based on the Fraunhofer diffraction principle. The most important problem is a noise signal induced by the flickering phenomena of incident light through hot air. A calibration reticle was used for analyzing the noise signals, and a data kill method for compensation was presented. Alcohol fuels such as methanol, ethanol, etc, were injected in hot air streaming and their characteristic diameters were estimated by the presented method.

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The distribution of film cooling effectiveness on both suction and pressure surfaces of a gas turbine blade was measured for several density ratios of injectant and main stream. The coolant was injected from a rectangular hole located near the leading edge of the blade. As a result, it was clarified that the film cooling effectiveness is mainly governed by the momentum flux ratio of injectant and main stream on both suction and pressure surfaces independent of density ratio, and the optimum momentum flux ratio is about 1.0 on the suction surface and about 0.01 or less than 0.01 on the pressure surface.

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The heat transfer rates of SUS 316 L stainless steel/sodium heat pipes having 2 Iayers, 4 Iayers and 6 Iayers of wicking material of 50 mesh screen at sodium vapor temperatures ranging from 500 to 700°C are shown. The heat transfer rates of the sodium heat pipes were obtained experimentally and by using the formula for effective thermal conductivity based on the series model. The calculation results agreed fairly well with the experimental results.

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Consecutive studies has been carried out for the purpose of clarifying spray performances of highly concentrated CWM and for obtaining a guide for the design of practical twin-fluid atomizers. Disintegration mechanisms and spray characteristics were investigated using plain-jet type of CWM atomization, and compared with those of single phase liquids. Furthermore, those disintegration phenomena and spray characteristics were considered in the proposed disintegration model. In the disintegration of a CWM jet by high speed air, atomization phenomena become similar to those of low viscosity liquids. Spray is generated basically by the tearing off of irregularly shaped small drops from the jet surface and splitting up of the unstably fluctuating jet into spherical drops. The change in Sauter's mean diameter of spray for air velocity changes its tendency at a certain velocity.

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A determination of temperature distributions in an axisymmetric propane-air premixed flame by holographic interferometry is described. In order to quantify the flame temperature from interferometric data, it is necessary to separate the effect of temperature changes and gas composition changes on refractivity. The gas composition profiles are estimated from the assumption of similarity between temperature and gas concentration fields. The relations between fringe number and temperature are derived for combustion gases and the factors that control the accuracy are discussed. The results show that the corrected temperature using estimated gas concentration agrees well with one using measured values.

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The catalytic reduction process of NO_x by NH₃ has been applied mainly to the clean combustion flue gases of LPG or LNG, which do not contain the harmful component which reduces the catalyst activity. This paper describes the experimental results of a survey for the catalytic reduction removal of NO_x from dirty gas containing higher concentrations of HCl, SO_x and dust emitted from a municipal refuse incinerator. The effects of reaction temperature, space velocity and the NH₃ injection amount on the NO_x removal efficiency are studied experimentally, and the change of V₂O₅-TiO₂ catalyst performance with time is examined, and the regeneration techniques for catalysts are also discussed on the basis of the results of the heat treatment.

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Internal combustion engine has characteristic of non-linearity and time-variability. Therefore, optimalizing control is the best way to realize the maximum value of relevant perforemance index of internal combustion engines. Optimalizing control brings, however, a variation in indicated work of the combustion chamber as well as a variation in the performance index itself. So, the regulator system to compensate such a variation is essential for these control system. Reported here is an application study of the model reference adaptive control theory for a regulator system, carried out with both aspects of model simulations and real engine operations. As a result, smooth real engine operation by the model reference adaptive control and a good agreement between the model simulation and real engine operation behaviors were confirmed.

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