Showing papers in "Jsme International Journal Series B-fluids and Thermal Engineering in 1984"
TL;DR: In this article, an analysis of mean and periodical motion in the near-wake flow is performed around a finite circular cylinder on a flat plate, where the slenderness parameter of the cylinder is in a range of l/d=1∼8.
Abstract: Some flow visualization experiments and measurements of surface pressure, Strouhal number, etc. around a finite circular cylinder on a flat plate have been performed in order to study the effect of a three-dimensional flow. The slenderness parameter of the cylinder is in a range of l/d=1∼8, where the slenderness parameter influences remarkably the flow behavior. From an analysis of mean and periodical motion in the near-wake flow, the following results are obtained. (1) The separation velocity at the side wall is lower than that of a two-dimensional cylinder, and this decreases the drag coefficients. (2) A pair of trailing vortices exist right below the free-end. (3) Down-wash flow and the trailing vortex near the free-end dominate the behavior of Karman vortex shedding. Finally, based on these results, the flow models around the finite height cylinder are presented.
241 citations
TL;DR: In this paper, the conditions of the occurrence of the above flow patterns and their flow characteristics in more detailed were investigated and it was shown that the unstable flow is caused by the intermittent reattachment of the shear layer onto the downstream cylinder, the unique phenomenon on the Strouhal numner occurs in the range of 2.5×104≤Re≤6.5 ×104 and is a transition phenomenon due to interference between the two cylinders.
Abstract: In the previous paper, three flow patterns were found at small spacing between two cylinders arranged in tandem as follows: the first is a flow without reattachment of the shear layer separated from the upstream cylinder, the second is an unstable flow and the third is an unique flow like that the frequency of the vortex shedding is nearly constant regardless of the free stream velocity. The purpose of this paper is to investigate the conditions of the occurrence of the above flow patterns and their flow characteristics in more detailed. It becomes clear that the unstable flow is caused by the intermittent reattachment of the shear layer onto the downstream cylinder, the unique phenomenon on the Strouhal numner occurs in the range of 2.5×104≤Re≤6.5×104 and is a transition phenomenon due to interference between the two cylinders. Beyond Re=6.5×104, the Strouhal number becomes again constant.
129 citations
TL;DR: In this paper, a series of configurations of casing treatment were compared to obtain the optimum ones judged from above-mentioned two standpoints: larger stall margin improvement and smaller lowering of efficiency.
Abstract: Casing treatment is known to improve the stall margin of axial compressors. However, it is known as well that casing treatment lowers the efficiency of compressors. An experiment was planned in order to test a series of configurations of casing treatment which are supposed to have favourable effects and to obtain the optimum ones, if any, judged from above-mentioned two standpoints: larger stall margin improvement and smaller lowering of efficiency. The result shows that the relation between the stall margin imp improvement and the compressor efficiency for all of the tested configurations falls on some smooth curved-line, and thus, there exists no particularly superior treatment configuration to others. It rather shows that a certain amount of loss in efficiency is inevitable in order to obtain the required amount of stall margin improvement. Influence of rotor tip clearance on the effect of casing treatment was also examined. The result can be used as a guide for the selection of configurations in designing the casing treatment.
118 citations
TL;DR: In this paper, the authors investigated the characteristics of flow around a square prism at angles of attack (0°≤α≤45°) in the range of subcritical Reynolds numbers.
Abstract: Experimental investigations on the characteristics of the flow around a square prism at angles of attack (0°≤α≤45°) were carried out in the range of subcritical Reynolds numbers. For α<15°, the perfect separated regime may be further subdivided into synunetric and unsymuetric flows at α=5°. For 15°
91 citations
TL;DR: In this paper, a developed simulator on a rotational vibration and a strain at a root of a tooth, on a power transmission spur gear, is presented, which solves a differential equation with one degree of freedom in consideration of the behaviour of the stiffness around tooth tip meshing.
Abstract: This paper introduces a developed simulator on a rotational vibration and a strain at a root of a tooth, on a power transmission spur gear. The simulator solves a differential equation with one degree of freedom in consideration of the behaviour of the stiffness around tooth tip meshing. The stiffness function is discussed and determined with static and dynamic meshing tests under load. The developed simulator has one more distinctive feature that the errors of the gears are put into the simulator with a newly developed automatic gear accuracy measuring instrument. The simulated outputs depict precisely the experimental behaviours. Through the development of this simulator, the the discussion becomes easier on the effectiveness of a spur gear for the decrease of vibration.
75 citations
TL;DR: A detailed experimental investigation was carried out on the characteristics of the flow around three circular cylinders arranged in line as discussed by the authors, where three cases concerned with the behavior of the shear layers separated from the first cylinder on the downstream ones: the first is a case without reattachment (W), the second is one with reattraction (R), and the third is one rolling up in the front region of the downstream cylinders (J).
Abstract: A detailed experimental investigation was carried out on the characteristics of the flow around three circular cylinders arranged in line. There are three cases concerned with the behavior of the shear layers separated from the first cylinder on the downstream ones: the first is a case without reattachment (W), the second is one with reattachment (R) and the third is one rolling up in the front region of the downstream cylinders (J). The flow patterns were classified according to W, R and J as follows: patterns A(W, W), B'(W, WrW, , R), B(R, R), C(R, J), E(R, JrJ, J) and D(J, J). The characteristics of these flow patterns were clarified. The results were compared with conventional results on two and four circular cylinders arranged in line.
68 citations
TL;DR: In this paper, a new type of tool wear which should be referred to as "combing wear" was found in drilling of reinforced plastics (GFRP, CFRP and others).
Abstract: In recent years, the reinforced plastics (GFRP, CFRP and others) are used in a wide field of manufacturing industry. With an increase of the demand for such composite materials, the need to drill these products is increasing rapidly. This paper deals with drilling of GFRP and CFRP, using high speed steel (SKH9) and cemented carbode (KOl. PlO and ultra-fine grain) drills. Comparison of four drills is done by investigating tool wear pattern, flank wear width and cutting forces. A new type of tool wear which should be referred to as "combing wear" was found in drilling of CFRP. In addition, it was found that KOl has the highest wear resistance, FG shows the second highest and the wear of high speed steel drill is remarkably larger than that of carbide drills.
53 citations
TL;DR: In this article, the authors deal with the infiltration length of molten aluminum to a continuous glass fiber bundle for various squeeze conditions and show that the infiltrated length is proportional to the squeeze pressure, increases exponentially with an increase in the fiber temperature and does not depend on the ram speed.
Abstract: The present paper deals with the infiltration length of molten aluminum to a continuous glass fiber bundle for various squeeze conditions. The results show that the infiltrated length is proportional to the squeeze pressure, increases exponentially with an increase in the fiber temperature and does not depend on the ram speed. The empirical infiltration length was in good agreement with the calculated one, based on Darcy's law and a newly proposed infiltration model : molten aluminum infiltrates through the gap accompanied with the formation of a solidified layer on the fiber surface, and finally stops to solidify immediately when the heat quantity of the molten aluminum front is balanced to the released heat to fiber ahead of the front. Thus, a method to predict the infiltrated length for the practical squeeze casting is proposed.
42 citations
TL;DR: In this article, the effect of the plate contact angle to water on the formation of frost on a cooled plate was investigated and it was found that when the temperature difference between the cooled plate and the dew point of air stream, was less than about 1.50c the frost thickness might never build up greater than 0.5mm.
Abstract: Experiments have been performed to investigate the effect of cooled-plate characteristic on frost formation under the condition of forced convection. Two kinds of plates having the different contact angles to water, were utilized. Special attention was focused on the incipient phenomena of the effect of the plate contact angle to water on the frost forming on the cooled plate. It was found that when the temperature difference between the cooled plate and the dew point of air stream, was less than about 1.50c the frost thickness might never build up greater than 0.5mm.
36 citations
TL;DR: In this paper, the coupled lateral-torsional vibration of rotors trained by gears is investigated. But the authors assume that the tooth rigidity is assumed to be a linear spring, and backlash and tooth profile error are neglected, and the force acting on the contact line is only a function of rotations at gears.
Abstract: This paper is concerned with the coupled lateral-torsional vibration of rotors trained by gears. First, numerical calculation technique using transfer matrix method is presented to obtain both free and forced vibrations, where, for the simplicity of analysis, tooth rigidity is assumed to be a linear spring, and backlash and tooth profile error are neglected. Then the numerical calculations were carried out in three cases; (1) the force acting on the contact line is only a function of rotations at gears, (2) the force acting on the contact line is a function of both the rotations and the flexure at gears, and (3) two rotors are not coupled. The eigenvalues, eigenmodes, and the responses of unbalanced mass are calculated and the results are discussed.
36 citations
TL;DR: In this paper, a theoretical analysis of the harmonic oscillation as well as the subharmonic oscillation of order 1/2 was conducted using a shallow spherical steel shell, and the experimental analysis confirmed the validity of the theoretical analysis.
Abstract: Axisymmetric forced oscillations of a shallow spherical shell subjected to harmonic excitation are investigated. Based on modal equations derived from the von Karman dynamic equations, a theoretical analysis is conducted of the harmonic oscillation as well as the subharmonic oscillation of order 1/2. The theoretical analysis reveals that in certain cases the response curve of the harmonic oscillation is of soft spring type, that the subharmonic oscillation of order 1/2 can occur, and that the characters of the subharmonic oscillation are greatly influenced by internal resonance. An experimental analysis is also conducted with use of a shallow spherical steel shell. The experimental analysis confirms the validity of the theoretical analysis.
TL;DR: In this article, the instantaneous blade surface pressure distributions affected by volute pressure distributions are measured on the suction cover surface of a pump with an open-type centrifugal impeller having one blade, and a difference between actual radial thrust and the integrated value of static pressure along the impeller outlet is discussed.
Abstract: Although single-blade centrifugal pumps are frequently used to handle waste water with solids, they have poor durability because they show severe vibration caused by a fluctuating radial thrust. Very few reports on the fluctuating radial thrust of turbo-machines have been published to date. Hence, details of the behavior and mechanism of the fluctuating radial thrust remain unclear, and a method for reducing the fluctuation is not established. In this report, instantaneous blade surface pressure distributions affected by volute pressure distributions are measured on the suction cover surface of a pump with an open-type centrifugal impeller having one blade. The fluctuating radial thrust mechanism is then clarified on the basis of these measurements, and a difference between actual radial thrust and the integrated value of static pressure along the impeller outlet is discussed. Furthermore, the radial thrust is separated into dynamic and static radial thrust vectors and a method for reducing the dynamic components, which are the cause of pump vibration, is demonstrated.
TL;DR: In this paper, a dual dynamic absorber is proposed to reduce the transmissibility across a main vibration system at resonance, and optimum values for its tuning and damping parameters are specified in graphical forms and by formulas for designing.
Abstract: In order to eliminate the drawbacks of a conventional dynamic absorber whose damping performance is very sensitive to the variation of parameters, use of a dual dynamic absorber is proposed in this paper. To reduce the transmissibility across a main vibration system at resonance, the optimum design procedure of the dual dynamic absorber is described, and optimum values for its tuning and damping parameters are specified in graphical forms and by formulas for the designing. Utilizing the design formulas, the effectiveness of the dual dynamic absorber in reducing the transmissibility at resonance is studied and shown to be considerably greater than that of the conventional dynamic absorber. Also, it is shown that by use of the dual absorber, it is possible to avoid a decrease of damping performance with the change of the natural frequency of the main vibration system and of damping in its absorbers.
TL;DR: In this paper, the wall static pressure fluctuation was measured along the duct and statistically analyzed to make clear the mechanism of the pseudo-shock vibration, and the result showed that the vibration had two main frequencies, high and low ones.
Abstract: Vibration of a pseudo-shock in a duct often causes noise, vibration and breakdown of the duct. In the present study the wall static pressure fluctuation was measured along the duct and statistically analyzed to make clear the mechanism of the pseudo-shock vibration. The result showed that the vibration had two main frequencies, high and low ones. The former was the natural frequency of the air column in the divergent passage attached downstream of the duct, and the pressure fluctuation propagated in the upstream direction. The latter was the natural frequency of the air column in the duct downstream of the pseudo-shock and this disturbance propagated in the downstream direction. Each vibration was maintained by the interaction of themselves.
TL;DR: In this article, the authors reported the results of studies on cable kink phenomenon using potential energy method and showed that cable deformation changes from torsional deformation to bending deformation.
Abstract: Cable kink is well recognized as a significant problem in use of submarine cables. Cable kink occurs when a cable loop forms due to torsion and tension action, and then tightens under subsequent tension increase. However, few investigations have been reported on this cable kink phenomenon. The relation between cable mechanical properties and cable kink has not been clarified. This paper reports the results of studies on cable kink phenomenon using potential energy method. It was made clear that cable kink occurs when cable deformation changes from torsional deformation to bending deformation. Results also revealed that cable kink phenomenon is controlled by only four parameters; cable slack, cable twist, cable diameter and ratio of bending rigidity to torsional rigidity.
TL;DR: In this paper, the performance characteristics of elliptical journal bearings in turbulent flow regime are studied theoretically and experimentally, and it is found that the turbulence affects significantly the static and dynamic characteristics of such bearings and the stability limits of the bearings become larger with an increase of ellipticity ratio.
Abstract: In this paper, the performance characteristics of elliptical journal bearings in turbulent flow regime are studied theoretically and experimentally. Solving the turbulent lubrication equation by the semi-analytical finite element method, the static and dynamic characteristics such as the Sommerfeld number, the locus of shaft center, the friction coefficient and the whirl onset speed are obtained for various mean Reynolds' numbers and ellipticity ratios, and the results are compared with the experimental ones. It is found that the turbulence affects significantly the static and dynamic characteristics of such bearings and the stability limits of the bearings become larger with an increase of ellipticity ratio.
TL;DR: In this paper, a mixed average Reynolds equation for the rough surface is derived, where mixing ratios for averaging film thickness can be determined by using the unit roughness with symmetrical film thickness.
Abstract: A new method is presented for simulating hydrodynamic lubrication with two-dimensional roughness. As a result of utilizing the concept of flow conductance in lubricating film with a unit two-dimensional roughness or a regular series of the unit roughness, it is found that a smooth surface equivalent to the rough one is given by mixed average film thickness of arithmetic and harmonic average film thickness. A mixed average Reynolds equation for the rough surface is derived, where mixing ratios for averaging film thickness can be determined by using the unit roughness with symmetrical film thickness. The equation is justified by comparison with results computed from real rough film thickness. This method is applied to some selected isotropic and anisotropic roughnesses. The most important conclusion is that micro topography of a unit roughness governs the total surface roughness effects.
TL;DR: In this paper, the radial flow of a thin liquid film was studied experimentally and the experimental results about laminar flow were compared both with the theory of Watson and with the approximate solution for a film flow formed by a water jet falling vertically onto a horizontal plane, by using an equivalent length of opening instead of a radius of water jet.
Abstract: The radial flow of a thin liquid film is studied experimentally. The liquid film was obtained by a water discharge from the thin cylindrical opening formed by a circular nozzle and a flat plate. The film thickness was measured by means of a point gauge method. The experimental results about laminar flow are compared both with the theory of Watson and with the approximate solution for a film flow formed by a water jet falling vertically onto a horizontal plane, by using an equivalent length of opening instead of a radius of water jet. About the liquid film in which the transition from laminar to turbulent flow occurs, the approximate solution for turbulent region is compared with experimental results.
TL;DR: In this article, an experimental study of the laminar-turbulent transition in the radial flow of a thin liquid film on horizontal plane was performed using a stroboscope.
Abstract: This paper describes an experimental study of the laminar-turbulent transition in the radial flow of a thin liquid film on horizontal plane. The film flow was obtained by a water discharge from the thin cylindrical opening formed by a circular nozzle and a flat glass plate. The transition mechanism could be clearly observed in a visual observation using a stroboscope, since a turbulent motion in the thin layer of water disturbed the water surface. A sequence of experiments revealed the existence of a critical discharge Reynolds number Ret, cr, based on the equivalent length of opening, above which the transition takes place. The relation between Re and the dimensionless radius rt* of the point of transition and the relation between rt* and the local Reynolds number Rer based on the film thickness at rt are established.
TL;DR: In this article, experiments of the collection efficiencies with fly-ash particles of the arithmetic mean diameter Xp=2.06μm for the returned flow type (D1=90 mm), the axial flow type and the cone type of the tangential inlet cyclones were done.
Abstract: The experiments of the collection efficiencies with the fly-ash particles of the arithmetic mean diameter Xp=2.06μm for the returned flow type (D1=90 mm), the axial flow type (D1=90 mm) and the cone type (D1=100 mm) of the tangential inlet cyclones were done. The feed concentrations of the particles were Co=5 - 45 g/m3. The best collection efficiencies were obtained by the ordinary returned flow type the cyclone and the worst collection efficiencies were obtained by the axial flow type of the cyclone. The main differences of those collection efficiencies were elucidated by the generation of the couple circulation zones based upon the analysis of the equi-flow rate lines in the axial flow cylindrical cyclone.
TL;DR: In this article, the authors classified pulsatile pipe flows into four categories, such as laminar, transitional, conditionally turbulent, and fully turbulent flows, and determined the limits between these four flows experimentally as functions of the dimensionless frequency, time-averaged Reynolds number, and Reynolds number based on the velocity amplitude.
Abstract: Pulsatile pipe flows are classified into four categories, such as laminar, transitional, conditionally turbulent, and fully turbulent flows. The limits between these four flows are determined experimentally as functions of the dimensionless frequency, time-averaged Reynolds number, and Reynolds number based on the velocity amplitude. The conditions describing the generation and decay of turbulence can be specified in the present experimental range by the parametric criterion K introduced for an accelerating steady flow. This fact implies that there exists a similarity between the effects of spatial acceleration and temporal one on the onset ofrelaminarization as well as the occurrence of turbulent bursting.
TL;DR: In this article, the authors measured and correlated pressure fluctuations at two points along the duct in the form of correlation factors and coherences, and investigated the propagation of the pressure fluctuation.
Abstract: In the 1st report pressure fluctuation at each point in the duct was measured and analyzed. In the present study pressure fluctuations at two points along the duct were simultaneously measured and correlated statistically in the forms of correlation factors and coherences. Thereby the propagation of the pressure fluctuation was investigated. The variation of a pseudo-shock had two main frequencies, high and low ones. The former, the vibration of the air column in the divergent passage propagated upstream as a pressure wave, while the latter propagated covectionally with the main flow.
TL;DR: In this article, the performance of a centrifugal pump with an air-water two-phase inlet flow and the distribution of void fractions in the impeller was measured by the electric resistivity probe method.
Abstract: The interrelationship was experimentally studied between the performance of a centrifugal pump with an air-water two-phase inlet flow and the distribution of void fractions in the impeller Void fraction was measured by the electric resistivity probe method at twenty-four locations in the impeller, ie, eight needle tip void probes adjustable in their positions from the boss to the shroud-side were introduced The distribution of void fractions is closely related with the pump performance, especially with the transition process to a 'breakdown', under which the performance drastically degrades The slip ratio estimated from the information on void fraction decreases to less than unity with increasing volumetric inlet quality, which implies not only an increase of the amount of air dwelling near the inlet of the impeller, but also is an indication of breakdown A possibility is suggested that parameters linked with void fraction will be effective as a quantitative tool for analyzing the pump performance
TL;DR: In this article, the electrical resistance between a nozzle and a fine wire detector located in a spray jet was measured and the breakup length of a high speed jet was studied by measuring the electrical resistances between the nozzle and the wire detector.
Abstract: The breakup length of a high speed jet was studied by measuring the electrical resistance between a nozzle and a fine wire detector located in a spray jet. The maximum injection velocity was 190 m/s and the maximum Reynolds number was 6.4×104. In the spray flow region, the breakup length of a liquid jet which was injected at high injection pressure into a chamber has a finite value. As the injection velocity increased, the breakup length progressively decreased and reached a constant value. As the ambient pressure increased, the breakup length decreased. The effect of L/D (the ratio of nozzle length to the diameter) upon the breakup length was great at atmospheric ambient pressure, but not so great at a high ambient pressure.
TL;DR: In this paper, the influence of pressure angle error and normal pitch error on the vibration of profile-corrected spur gears has been investigated using the simulator developed by the authors, whose outputs depict precisely the experimental behavior.
Abstract: In this study, a power transmission spur gear is preferably a profile corrected spur gear. Supposing it is allowable that the given value deviates about ten-odd percent from the actual acceleration, it is synthesized how a pressure angle error and a normal pitch error influence the vibration of profile corrected spur gears, using the simulator developed by authors, whose outputs depict precisely the experimental behavious. The influence of these errors is revealed to depend on a rotational speed and a contact ratio as influence degree for each error. The influence degrees are shown on an influence chart of the performance of the rotational vibration by contour lines. A practical equation for the vibration of profile corrected gears having some errors is proposed.
TL;DR: In this paper, the causes and characteristics of lateral vibrations occurring when a rotating shaft is driven by a universal joint (so-called Hooke's joint) are the subject of a study.
Abstract: The causes and characteristics of lateral vibrations occurring when a rotating shaft is driven by a universal joint (so-called Hooke's joint) are the subject of this study. Dynamical considerations are made in relation to the mechanism of a moment transmitted by the universal joint. The analytical results regarding a secondary moment generated by the universal joint show that a driven shaft has a number of forced vibrations owing to the secondary moment. Each of these vibrations maked a resources when an angular velocity of the drive shaft coincides with one of the even integer submultiples of natural angular frequencies in the driven shaft system. The experimental results show good coincidence with the analytical results, so the validity of the analyses is confirmed.
TL;DR: In this article, the effects of thinning out of scanning lines and the relation between moire fringes and strain are studied by the sampling theorem, where deformed model gratings are sampled by a television camera and they are thinned out properly by using an image processing system.
Abstract: A master camera. scanning-moire method is a moire method in which the grating is replaced by the scanning lines of a television In the present paper, the principle of moire pattern appearance. the effects of thinning out of scanning lines and the relation between moire fringes and strain are studied by the sampling theorem. If deformed model gratings are sampled by a television camera and they are thinned out properly by using an image processing system, the strain distribution in a wide strain range can be analyzed from one picture.