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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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In order to calculate transonic flows in highly three-dimensionally twisted turbine blade cascades, the finite volume integral method of solving the governing equations is implemented for the treatment of boundary conditions and the discretization scheme. The developed scheme reduces the discretization error associated with the distorted gird configuration of highly three-dimensional blades. With the developed method, flows in two typical turbine blade cascades has been calculated with two kinds of treatment of energy equation.

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A numerical method (inverse method) was developed for a gas-particle supersonic flow past two-dimensional blunt bodies. This method is based on two transformations (von Mises and additional one), which are convenient for determining the shock layer flow fields and the body shapes. Using the present method, the pure gas flow field around a circular cylinder was first solved numerically for the freestream Mach numbers M_∞=2.0 and 3.0. Then the gas-particle flow in the shock layer around blunt bodies (nearly circular cylinders) was solved for freestream Mach number M_∞=3.0, with particle diameter d_p 2, 5, 10 μm and freestream loading ratios α=0, 0.2, 0.5 and 1.0, respectively. The effects of d_p and α on the shock stand-off distance, the body surface pressure and flow quantities along the stagnation streamline are discussed, and the flow patterns in the shock layers are also shown.

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A general numerical calculation scheme has been developed for the predictions of internal flows within ducts of arbitrary wall geometries. A general coordinate transformation procedure has been proposed so as to overcome the complexities associated with irregular wall boundaries. Navier-Stokes equations are reformulated into arbitrary coordinate and velocity systems through a vector analysis without resorting to any extensive tensor calculus. General finite difference equations are reduced upon discretizing the governing equations in the generalized velocity and coordinate system. As for practical applications, calculations are carried out for the developing flows and diverging-converging rectangular duct.

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Comparison with the theoretical analysis of the decay of a turbulent swirling flow in a pipe and the results of experiments are presented. An angular momentum equation is guided from Navier-Stokes equations. Here, Reynolds shearing stress is treated with Boussinesq's expression. The second derivative of angular momentum respects to radius needs to be negative from the decay of moment. Therefore, at the boundary of forced and free vortex, an attention to the solution of equation must be payed. Near the wall, shearing stress for laminer flow is applied. And angular momentum equations in each region are numerically solved and that solutions are connected smoothly on each boundary. As the results, the prediction of the decay agrees much with the results of experiments.

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The genesis of Korotkoff sound at high cuff pressure has been made clear by the model expreimental study using the thin walled silicon rubber tube being modified to have zero internal cross sectional area as an artery ehen compressed by the relatively higher external pressure than the internal one. The sound is generated by the steep pressure wave front formed in the course of pressure wave propagation through the completely collapsed tube segment under the cuff. The amplitude of the pressure wave penetrating into the collapsed tube segment and that of the steep wave front reaching to the distal end of the segment, measured from the artery also weakens correspondingly and, at some Peb, the sound becomes unaudible. The pressure wave form depends strongly on the transmural pressure at the distal end of the collapsed segment.

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Trapped air in a liquid conduit has a great influence on the fluid transient. In this paper, especially its effect on the transient flow rate is studied experimentally and analytically. Transient flow velocity, following a quick opening of a valve attached at the downstream end of the test pipeline, was measured experimentally. The experiments showed that the transient flow velocity often exceeds the final steady state flow velocity. The numerical calculation by means of characteristics method showed a good agreement with the experimental results. Maximum value of the transient flow velocity depends on the volume and the position of the trapped air, and the pressure loss of the pipeline and the valve, and the pressure at the downstream side of the valve. Five dimensionless parameters, which represent above-mentioned factors respectively, are derived, and the relations between the maximum flow velocity and these five parameters are expressed graphically.

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A numerical scheme is developed for use on two-dimensional time-dependent incompressible turbulent flows of thigh Reynolds number, and applied to the flow over an impulsively started 15% thickness elliptic airfoil at an angle of attack of 30° at a Reynolds number of 5×10⁵. The scheme divides the flow field around an airfoil into two regions, the boundary-layer region and its outer flow region. The Reynolds equations with vorticity and stream function as variables are solved in the outer flow domain. The equation of integrated form for the vorticity is solved using a combination of finite differences and grid-free point vortices, while that for the stream function is solved by a similar technique to "Cloud In Cell" method. Results for the problem which involved massive flow separation were compared with experimental data and flow fields and aerodynamic forces acting on the airfoil compared well with mesurements.

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The stalling characteristics of 15% thickness elliptic airfoils in incompressible turbulent flows at a Reynolds number of 5×10⁵ are investigated numerically by solving the Reynolds equations and the boundary-layer equations. Calculations were performed on the airfoils impulsively started at high angles of attack and oscillating in pitch with large amplitude. The development of the separated flows and the behaviour of the forces are studied in terms of patterns of streamlines, vectors of velocity and lines of constant vorticity, and normal force and moment coefficients it is observed from the results that the separated flows over impulsively started airfoils at high angles of attack show oscillatory behaviour.

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The early stage of the flows due to uniformly accelerated flat plate, elliptic and circular cylinders from rest in incompressible viscous fluids are numerically studied by the finite difference method. The time dependence of streamlines and equi-vorticity lines are shown in the flow patterns. The Dufort-Frankel technique is used for solving the vorticity transport equation and the finite Fourier transport equation and the finite Fourier transform for solving the stream function, which is applied to the analysis of a block tridiagonal matrix equation. The main conclusions are as follows ; (1) The Fourier series method is more than ten times faster than the SOR method. (2) Numerical experiments obtained here have very good agreements with real experiments for flat plates and circular cylinders. (3) The length of vortex pairs behind an uniformly accelerated elliptic cylinder at the attack angle 90° is obtained as a resultant of numerical experiments. (4) The growing process of the secondary vortexes behind a circular cylinder is revealed at Reynolds number 731.

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This report is concerned with results of the systematic experiment which aims to clarify the relation between the behavior of the wake from a circular cylinder within a laminar boundary-layer and the boundary-layer transition. Main results are as follows. The behavior of wake is different according to the gap size, the boundary-layer thickness and the distance from the origin of boundary-layer to the elements, and is classified into-three regions. First, in the region I, no vortex shedding is found and the process of transition is substantially same as the process caused by the roughness elements which is laid on the surface In region II, the periodic laminar vortex shedding is observed to be died out in downstream and the transition process is similar to one in region I. In region III, the regular vortex shedding develops rapidly to turbulent wake and causes the boundary-layer transition.

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The paper presents the behavior of a separating shear layer and its reattachment when an additional centrifugal body force due to streamline curvature is imposed on the shear layer. A curved channel is attached to a backward-facing step to obtain such a flow situation. In addition to he inherent stability within the conventional straight channel, the stabilizing and destabilizing effects on the reattachment process are given according to the direction of curvature. Three different surface configurations are used (flat, convex, and concave); with weak, mild, and strong surface curvature, the measurements were performed for seven separated cases. The reattachments point was determined by a thermal tuft probe. A hot-wire anemometer was used for the measurements of mean velocity and turbulence. Flow visualization of the shear layer was made by means of a smoke-wire method. Reynolds number based on step height was 8×10⁴, curvature paramenter being in the rage -0.04<δ/R<0.05.

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Organized structures to make clear bursting phenomenon of turbulent boundary layers with injection and suction through a slit have been investigated experimentally. Conditional sampling with VITA and quadrant analysis have been applied and space-time correlation has been measured. Moreover, the relationship between bursting phenomenon and wall pressure has been investigated. These results show that the contribution from ejection of bursting phenomenon to mean Reynolds stress - <uv>^^- near the wall decreases by injection through the slit and increases by suction through the slit. This in the reason that mean Reynolds stress near the wall decreases by injection and increases by suction. Space-time correlation of velocities indicates that coherent structure with oblique angle to the wall exists in boundary layer. The oblique angle to the wall becomes larger with injection.

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This paper discribes the influence of wall roughness on the transition from laminar to turbulent flow occurred in the redial flow of a thin liquid film. Visual observations on the properties of liquid surface were performed on the plates with the following three types of distributed roughness; (a) saw-toothed roughness and (b) trapezoidal shaped roughness, both of which were regularly constructed in a concentric configuration, and (c) irregularly distributed sand roughness. It was found that the point of transition moved upstream as the height of wall roughness in creases under otherwise identical conditions, and that the transition occurred in each of the three regions of flow, namely, (1) the stagnation flow, (2) the region in which the laminar boundary layer grows, and (3) the region in which the whole flow is the laminar boundary layer. Furthermore, experimental results showed that the critical local Reynolds number decreases according as the height of wall roughness increased.

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Experimental investigations on the characteristics of the flow around rectangular cylinders were carrded out is the range of subcritical Reynolds numbers. The width to height ratio (C/d) of the sections was varied from 0.1 to 4.0. The fluctuating pressure coefficient has a maximum in the same tendency as that of the drag coefficient when C/d=0.67. The differences in flow patterns between the two critical values of the ratios C/d=0.67 and 2.8 become clear. The flow around the cylinder around the leading edge corners have been found to indicate a good agreements with that around the cylinder with larger value of the ratio of C/d.

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This paper describes some experimental values of aerodynamic resistance of perforated plates in natural convection, providing basic thermal data necessary for designing electronic equipment casings. In the conventional measuring method which measures only in the higher region of Reynolds number, there is a disadvantage that the utmost precision cannot be attained in measurement due to the values of pressure loss and velocity being unidentifiably small. Io our new method, however, it is designed to evaluate a fluid resistance coefficient depending on the air temperature elevated by the combined effect of motive power of natural convection and fluid resistance and consequently to elucidate the influence of Reynolds number, coefficient of porosity, and thickness of plates/diameter of holes on resistance coefficient of perforated plates.

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Simplified correlations for estimating characteristic parameters are presented with reference to a transient slug flow, which is induce by an abrupt increase in a volumetric gas flux in a horizontal two-phase shear flow. The correlations are available in the range of tube diameter : 20-40 mm, initial gas flux : 0.3-1.0 m/s, final gas flux : 0.9-3.2 m/s. and liquid flux : 0.04-0.08 m/s.

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As the continuation of the research to improve the suction performance of a high-head axial-flow pump, composed of tandem impellers (an inducer and an impeller), the present study was aimed to make clear the three-dimensional periodic flow field in the pump. The KIII type pump, a bigger model of the KII type, was constructed and used to examine the flow field, which was measured by traversing a combined five-hole Pitot probe with high-frequency response at the inlet and the exit of each impeller. Adopting the "phase locked ensemble averaging" technique, the sampling date were analyzed with the aid of a digital computer, and the time averaged distributions of pressure and components of velocity with respect to the impeller passages were obtained. Each efficiency of components, such as the inducer, the impeller and the guide vanes was also obtained to evaluate the relationship among them.

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Externally pressurized supersonic gas thrust bearings whose generation of load capacity is substantially independent of the viscosity of working fluids, have been proposed and analyzed by the authors. This report presents the experimental results of the static characteristics of this new type of bearings. The experimental results including load capacity, stiffness, mass flow rate and pressure distributions in the bearing clearance, generally show a good agreement with the theoretical predictions and verify the validity of this new bearing. The effect of an orifice to improve the stiffness is also examined. Some problems which should be solved to put the bearing in practical use are pointed out.

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