The three-dimensional time dependent compressible Navier-Stokes equations are numerically solved to study acoustic emission nature in a supersonic round jet at high convective Mach number (M=2.0) using high-order compact upwind schemes. The numerical results provide new physical insights into Mach wave generation nature in a supersonic round jet. Upstream disturbance conditions play an important role for the emission of the Mach waves in a supersonic jet. The numerical results show that the jet forced with a pair of first helical modes can restrict emission angle of Mach wave due to the modes interference.

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When a low density gas compared with the ambient gas is discharged from a round nozzle, side jets that are radial ejections of jet fluid are generated at the initial region. The density ratio between the jet fluid and the ambient fluid is a main parameter for side-jet formation. Since the side-jet formation is also related to the instability of shear layer, another parameter is a ratio of the momentum thickness and the nozzle diameter at the nozzle exit. Compressibility suppresses the generation of the side jets. The variable-density jets were issued from two round nozzles, which have different area contraction ratio, with various jet-speed. Effects of the density ratio, the momentum thickness ratio and the Mach number, which is defined by the issuing conditions, on the side-jet formation are researched experimentally. An existence of side jets was confirmed by flow visualization using a laser sheet.

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In order to improve the performance of mixing with multiple impinging jet, we conduct the DNS (direct numerical simulation) of four round impinging jet arranged at an inflow of flow field. As control parameters, both the geometrical arrangements of jets and the separation between each jet are varied. From view of instantaneous vortical structures and time-averaged velocity distribution, it reveals that the generation of vortical structures are enhanced due to an interaction between each jet, compared to that of a single impinging jet, and that various type of upward flow which does not exist in the single one, appears according to the control parameter.

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Electro-rheological (ER) nano-suspensions based on titanium dioxide nano-particles with particle diameter on the order of 100 nm were prepared. Micro-gap flow behavior and microstructure were evaluated for the suspensions with a particle volume fraction of 8.8 vol%. For the sample based on a silicone oil, the ER effect and flow behavior were found to be stable during the sharing time on the order of 10_2s. The ER response measured at a given strength of the electric field for the sample based on a chemically-modified silicone oil was effectively induced by the electric field, especially with low strengths, and it was larger than that of the sample based on the silicone oil. Furthermore, the reversibility of the ER response was fairly well for the sample based on the modified silicone oil.

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Damping properties of a damper using magnetic compound fluids are investigated experimentally. In this study, we focus on the effects of frequency of forced vibration on the damper utilizing magnetic compound fluids containing a fibrous material such as alpha-cellulose. Increase of alpha-cellulose in the magnetic compound fluid increases the maximum damping force. However, adding alpha-cellulose to the magnetic compound fluid leads to the small magnification ratio of damping force by applying magnetic field.

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new type of semi-active TLCD called MF-TLCD is designed. In this device, A magnetic fluid is used as a working fluid of TLCD, and vibration characteristics of fluids column can be controlled. In this study, the frequency responses of structure and magnetic fluid column are measured and the influence of magnetic field on the natural frequency of magnetic fluid column is researched. When double electromagnets are used, the natural frequency change is larger than the case of single electromagnet, and also, the position of electromagnets h that natural frequency changes from increase to decrease decided about one point.

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Magnetorheological (MR) fluids behave like a Bingham fluid having yield stress which can be rapidly changed in a reversible manner by applying magnetic field, being expected the innovative applications to industrial devices such as damper, valve, clutch and brake. In applications of MR fluid damper to seismic isolation and suppression technologies, one of serious problems is the sedimentation of dispersed particles in the MR fluid in the off-working state. In this research, "MR fluid porous composite" made of porous materials pregnant with MR fluid has been fabricated to solve this problem. And also, a seismic linear motion MR damper utilizing MR fluid porous composite has been designed and developed, which mainly consists of a ball screw and a rotary MR brake. The rotary MR brake has multi-disks between which the sheets of MR fluid porous composites are installed, and an electromagnet. The ball screw works to convert the linear motion (damping force) of the MR damper to the rotation (braking torque) of the MR brake with almost no transmission loss. The damping properties of the developed seismic MR damper were investigated experimentally to be found that the damping force of 20 kN is produced when applying an electric current of 0.5 A as designed.

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Magnetorheological (MR) fluids have many attractive features, including high yield strength, low viscosity and stable hysteretic behavior over a broad temperature range. In general, low viscosity MR fluids are widely acceptable to the applications to industrial devices with low energy loss under no magnetic field. While, although high viscosity MR fluids are suitable for some applications such as torque converters, viscous couplings, and damping devices which need fail-safe, there is almost no research to investigate the properties of high viscous MR fluids. In this research, the rheological properties and particle settling rate of high viscous MR fluids have been investigated, focusing on the effects of the MR fluid viscosity on its induced yield stress, flow curves and particle settling rate. The tested MR fluids are suspensions of micron-sized carbonyl iron particles dispersed into high viscosity silicone oils and mineral oil. The rheological properties in constant rpm tests and oscillatory tests have been measured using a HAAKE RSI50 parallel disk rheometer with magnetic circuit. An effective means of producing a stable MR fluid is by the increase of viscosity and the addition of anti-settling agent.

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Experimental study on the optical input-output characteristics of a hole formed with magnetic fluid and thin annular permanent magnet in the alternating magnetic fields were performed by using the photodiode sensor system. The hole of magnetic fluid was driven by the Helmholtz coil. The expansion and contraction motions of magnetic fluid hole in high frequency region was measured with the photodiode sensor system. The light intensity through the magnetic fluid hole was measured by the photodiode sensor system. The output signal was analyzed by a FFT analyzer. The optical input-output characteristics of the magnetic fluid hole in alternating fields were revealed.

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At the fields of robotics and sensing for artificial arm and artificial leg, the sensor that is able to response for shear force as well as normal force should be developed. Our developed haptic sensor by combining metal particles in balloon crude rubber has high quality of sensing for 0.01 N order normal force. The rubber is one of our developed MCF rubber. The present sensor has the high response of the electric current flowing inner the MCF rubber to the shear, normal forces and the crook motion. In the present, we dealt with the walk motions of robot having the MCF rubber sensor as the case of active work by normal force on the sensor. We clarified the effect of temperature on the MCF haptic rubber sensor attached on a robot at the walking.

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Drag control allows energy saving, noise reduction and thus heat control. However the only mean to attain it is through Active feedback control system. This research focuses on magnetic fluid because its characteristics are dramatically changed by magnetic field control and it is possible to reduce the pipe friction. In this article, a study of the effect of external magnetic field control on magnetic fluid. Pressure difference and flow rate measurements have been conducted under different Reynolds numbers and non-uniform magnetic field. The experiments showed a drop of the pipe friction coefficient which goes up to 9.9 percent in the transition region (Re = 2770). Yet, this phenomenon vanishes at higher Reynolds number.

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TiO_2 doping with carbon has widely been studied for environmental applications due to higher photocatalytic activity than typical undoped TiO_2 under visible light irradiation. In this study, carbon doped TiO_2 was synthesized in a DC-RF hybrid plasma flow system by a solution precursor spraying method and high functionality was assessed with methylene blue solution degradation under visible light irradiation. The synthesized highly functional carbon doped TO_2 from 11 wt% TTB showed high UV-visible absorbance and higher methylene blue solution degradation estimated at a rate constant of 1.14 X 10_<-3>.

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MHD power generation is a direct-electricity-generation method involving no mechanical components, such as a turbine. Usually plasma and liquid metal such as mercury are often used in the MHD power generation. However, the power generation using plasma requires high temperature which makes system operation dangerous to environment. Therefore, considering safety, this research aims to use low-melting-point-alloy as a working fluid for the power generation. In this study, the MHD power generation characteristic using the liquid metal was investigated. The results show that the output voltage linearly increases with Rh and a difference of the trend between laminar flow and turbulent flow is hard to see. Moreover, the results show that the characteristics of the output are changed by considering Faraday's law under non-uniform magnetic flux density.

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In order to overcome the difficulties of conventional methods for measuring concentration of solid-phase in the solid-liquid two-phase flow in micro-devices, a unique measuring technique using electromagnetic induction with diluted magnetic fluid is applied to measure the solid-liquid two-phase flow in a micro-tube. In this method, 5 wt.% magnetic fluid diluted by distilled water was used. In order to verify the validity of the technique for measuring solid-liquid two-phase flow, experiments in actual solid-liquid two-phase flow with particle drop flow were performed. The present method has demonstrated a promising way of measuring the particles diameter with satisfactory accuracy.

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The micro-bubble generator with a venturi tube generates a large number of micro-bubbles by bubble breakup phenomena. The bubble breakup is caused by a shock with pressure recovery in the diverging region of the venturi. However, a profile of Mach numbers in the flow direction of the venturi has not been estimated experimentally. In the present study, the profiles are estimated by measurements of pressure and void fraction profiles in the flow direction. In the experimental results, Mach numbers are higher than 1 between the throat and the bubble breakup point, and the numbers are lower than 1 downstream of the breakup point. It is proposed that the shock is present at the bubble breakup point. In addition, the breakup from the top to the bottom of a bubble surface is observed. This results means that the shock with pressure recovery causes the bubble breakup.

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In order to reduce the amount of chemical solvent used in the washing process, the non-chemical washing technology with micro-bubble is required. In the present study, we focus on the micro-bubble generator with a venturi tube. To clarify washing effect by the micro-bubble generator, washing experiment with cutting oil, grease and oil paint are conducted. As a result, the behavior of bubbles separating from the washing target with oil was visualized through the high speed video camera in detail. Additionally, the relation between the oil detachment rate and the pressure on the washing surface suggested that the pressure wave and micro-bubble from the bubble breakup are the advantage of this washing technology.

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This paper describes the results of microscopic observations on the petal surface of dandelion by the 3D laser scanning microscope. The change in surface shape of the cells with the movement in folding and unfolding of dandelion flower head was recorded by the analysis based on the measurements of surface roughness. Time variation of the surface roughness in live petal cells was revealed. The relation between the plant cell growth and the water flow in the plant cell was discussed from the viewpoint of fluid mechanics.

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In recent years, the fin in heat exchanger has to be downsized because the necessity of the compact heat exchanger rises. In this case, the problem of production's becoming difficult and rising for output cost is caused by directly downsizing of louver fin used so far. So, the downsizing of the offset fin that can be produced at a low price is paid to attention. The purpose of the present study aims at an increase in the heat exchange efficiency by using the compact offset fin. The present study clarifies the change in the heat fluid characteristic for change in flow channel geometry and presence of offset fin by using numerical analysis that applies cycle boundary condition in the direction of the flow qualitatively and quantitatively.

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In order to predict and evaluate erosion of products with particle-gas flow, an Erosion simulator is developed.The simulator is constructed from (1)erosion prediction model, (2)erosion basic test, (3)particle movement analysis by CFD. In this research, the equations of Finnie and Bitter are adapted as the erosion prediction model. The experimental fixed values in the model are obtainable by a centrifugal erosion tester. In order to ascertain this method's validity, simulation was compared with erosion depth of 12x4 tube array erosion test. As a result, the prediction of erosion depth generally agree with those obtained by the experiment, and it is seen to be able to estimate the erosion characteristic of tube bundle.

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The cyclone separator has been used for the separation of particles or dust in a gas or liquid stream. High separation efficiency can be obtained at the high centrifugal region with a high nozzle velocity when the density of the separated material is much larger than that of the working fluid. The decrease of the separation efficiency at the low centrifugal region was studied using a liquid cyclone separator where the separated particle density is near that of the liquid. A special eddy breaker was proposed to increase the separation efficiency at the low centrifugal region. An improvement of over 20% was obtained with the insertion of an eddy breaker at the appropriate location in the liquid cyclone separator.

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In order examine the influence of the temperature diffusivity around a cavity bubble on the bubble growth and temperature depression, the bubble growth of a single bubble was numerically analyzed with Rayleigh-Plesset Equation and heat transfer model around the interfacial surface of a bubble and compared with experimental results.

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The authors consider the flow between co-rotating disks, namely, the disks which rotate co-axially in the same direction at the same angular velocity, with a narrow gap enclosed by a stationary shroud at their circumferences. The flow often accompanies an azimuthally-fluctuating instability; a non-axisymmetric secondary flow near the shroud. In this study, the authors experimentally research outer vortex modes, namely changing disk-tip Reynolds numbers Re and gap aspect ratio δ. The authors use the experimental apparatus which has a pair of co-rotating disks in the stationary cylindrical enclosure. So the experimental apparatus is filled up the 64wt% Nal aq. including silica oxide particles with fluorescent paint and YAG laser lightened up on the meridian plane (r-z plane) between co-rotating disks. Then, the authors conduct the visualisations of r-z plane using high-speed video camera at each experimental parameter and carried out Particle Image Velocimetry (PIV) analyses.

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The present paper presents the rotating instability around a rotating cylinder between two coaxial stationary circular disks experimentally and numerically. In the experiment, the hot-wire measurements were conducted. In the simulations, the calculations were performed which are corresponding to the experimental setup. The experimental and numerical results shows qualitatively good agreements with respect to the velocity fluctuations. These results indicate the rotating instability of one cell rotating in the circumferential direction.

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The existence of rotating instability region of the flow around a cylinder rotating between two stationary disks was founded in the previous research. In this paper, the peripheral velocity around the rotating cylinder in pipe was measured. In order to investigate the rotating instability, the flow of rotating cylinder in the pipe was calculated by the three dimensional numerical simulation. It was found that higher peripheral velocity region rotates with 12Hz frequency in both the experiments and the calculation. The vortices in the meridional plane between the rotating cylinder and the outer static wall was found.

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The purpose of this paper is to study the flow field of a lockup clutch inside a torque converter. The performance of a torque converter has been one of the most important areas of improvement for an automobile equipped with an automatic transmission. Improving the torque converter's performance and efficiency are key contributions to saving fuel, which is an important consideration with the recent increase in environmental awareness. Moreover, the lockup operation- or slipping control- of an automatic transmission is another good opportunity for improving fuel economy.

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General mixing machine which has rotor with blades have characteristics such as wide use in various fluids, short mixing time, low cost and so on. However, especially in high speed range, change of property of mixing fluids should be careful due to share force at blade tip and occurrence of cavitation. In addition, splash of fluids, higher power consumption and damage to mixing container also users and so on are also problems. Therefore in order to solve these problems, the mixing machine without blades called as M-Revo was developed. In this machine, the rotor shape is very simple, which have hemispherical shape and 3 through holes. And the fluids are mixed by jet from each hole. However the mixing performance is unknown. In the present study, the numerical analysis and small experiment were carried out to know the basic characteristic of M-Revo. As the results, it is found that M-Revo can mix the fluids.

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In the present experimental study, the authors try to clarify the characteristics of the flow around and inside a cross-flow fan in a typical geometry, over a wide parameter range of an aspect ratio L/D_2. In order to eliminate the complicated casing factors, the impeller rotates in open space without any casings. As a result, by using hot wire anemometer measurements and by conventional flow visualisations with a particle image velocimetry technique, the authors show that both the outflow rate and the maximum vorticity attain the maximum for L/D_2 = 0.6. In order to investigate the aspect-ratio effect, we further reveal minute fluctuating pressures on an impeller end wall for a singular L/D_2 = 0.6. Especially in these pressure measurements, the eccentric vortex is prevented to revolute by the insertion of a tongue, in order to consider the spatial structure of flow more precisely.

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Data center has been built with spread of cloud computing. Further, electric power consumption of it is growing rapidly. High power cooling fans are used for servers in the data center and there is a strong demand to increase power of it because of increase of quantity of heat from the servers. Contra-rotating rotors have been adopted for some of the high power cooling fans. It is important to clarify complicated internal flow condition and influence of a geometric shape of the cooling fans on performance and internal flow condition to achieve the high performance cooling fans. The performance characteristics and internal flow of the front and rear rotor of high power contra-rotating small-sized cooling fan is clarified by numerical analysis.

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In order to develop the low specific speed diagonal flow fan with good performance, low specific speed (Ns=670(rpm, m^3/min, m)) diagonal flow fan was designed using a quasi-three-dimensional aerodynamics design method, the fan test was carried out, and the internal flow fields were measured by the use of hotwire anemometer with a slant hotwire probe and sensor of pressure. From the result of the fan test, the test fan designed showed a good performance at design point. From the result of internal flow measurement, it is found at near design flow rate that the tip leakage vortex was occurred by high velocity deviation and low pressure on the casing wall.

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Internal flow in multi-blade centrifugal fan has been investigated with stereo-PIV measurement. A time mean flow structure in scroll casing has been reconstructed by traversing the interrogation section at several measuring locations. The sectional data to reconstruct three dimensional flow fields was acquired with the same spatial resolution as that of in-plane velocity. With these data, the fan efficiency and noise generation were discussed by comparing the stream-wise and cross sectional flows. Additionally, a passing flow between the blades has been observed with single PIV technique. The fluctuation in the passing flow shows the significant difference according to the fan driving modes.

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In an ultra micro centrifugal compressor (UMCC), the applicability of the two-dimensional blade has been investigated for the consideration of the productivity in the downsizing of impeller. On the other hand, the restriction of processing technology for the downsizing of compressor system relatively enlarges the size of tip clearance. Moreover, UMCC is required to operate at high rotational speed to establish the gas turbine cycle. Therefore, the blade thickness is enlarged by considering the stress acting on the blades due to the centrifugal force. In this study, the flow in the centrifugal impellers with the two-dimensional blade was analyzed numerically to investigat e the influence of the downsizing of compressor system on the similitude of aerodynamic performance. The computed results clarified that the compressor performance is remarkably decreased due to the relatively enlarged sizes of tip clearance and blade thickness by the downsizing of systems.

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In order to improve the performance and operating range of centrifugal compressors, it is indispensable to understand unsteady behavior of vortical flows. In this study, the flow fields at different rotational speed in a transonic centrifugal compressor with single splitter blades have been investigated by Detached Eddy Simulation(DES). The simulation showed that the detached shock wave ahead of full blade, which interacts with the tip leakage vortex as well as the suction surface of adjacent full blade, became strong with a rise in rotational speed, so that the shock wave caused the tip leakage vortex breakdown in almost all pitches. Moreover, it was found that early occurrence of the vortex breakdown at higher flow rate led to a reduction in operating range.

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In the blade design process, flow pattern prediction tools have an essential role to create a highly efficient blade shape. A viscous throughflow code, which can take into account the effects of boundary layer and blade thickness, was developed to evaluate axial turbine flows. In the present paper, the throughflow code is validated by applying it to a concentric annular tube flow. In addition* axial turbine internal flows were evaluated by the throughflow code. The simulation results showed that the throughflow code can predict the flow patterns very well if the effects of secondary flow are marginal.

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This paper details experimental and numerical studies on the secondary flow losses generated in highly loaded LPT (Low -Pressure Turbine) cascades. Secondary flow loss in LPT significantly contributes to its overall loss, especially in increased stage loading and high-lift airfoil cases. Hence it becomes more important to understand the secondary flow loss production mechanisms. The purpose of this study is to clarify the detail of secondary flow losses generated in LPT cascade and to investigate effects of highly loaded LPT airfoils on the secondary flow loss using LPT cascade whose solidity is changeable (RRS0% vs RRS15%). Detailed experiments using a 5-hole probe are carried out around endwall regions. In addition, a commercial software, ANSYS CFX is intensively used for the simulation of the flow fields to enhance the understanding of loss mechanism.

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Recent advanced film-cooling techniques tend to be multipurpose, e.g. cooling and flow control, and therefore the total performance is difficult to be evaluated. This paper has proposed a numerical method to estimate local rate of mean entropy generation based on the flow statistics obtained by large eddy simulation. The method is applied to evaluate the effectiveness of a novel film cooling concept, which not only cools the endwall region upstream a leading-edge of turbine vane but also suppresses the formation of horseshoe vortex, which is known to be responsible for overheating and aerodynamic losses by the legs of the vortex downstream. As a result, it is clearly suggested that the film coolant injection upstream the leading edge has a potential both to cool the enwall and to reduce aerodynamic losses simultaneously.

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This paper presents the numerical simulation of steam-droplet flows through a three stage steam turbine. The fundamental equations of compressible wet-steam flow in this study consist of conservation laws of the density of water vapor, the momentums, the total energy, the density of water liquid, and the number density of water droplets and they are coupled with SST turbulence model with relative velocities in general curvilinear coordinates. Compressible Navier-Stokes equations and mathematical models for equilibrium condensation are solved using the high-order high-resolution finite-difference method based on the fourth-order compact MUSCL TVD scheme, Roe's approximate Riemann solver, and the LU-SGS scheme. On the other hand, as the equation of motion of the droplets, the drag force, the unsteady drag force, the centrifugal force and the Coriolis force are calculated.

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This paper deals with an application of Computational Fluid Dynamics, CFD, to partial arc admission stages in an axial flow turbine. Unsteady 3-dimensional CFD analysis of a partial arc admission stage in an air turbine is conducted to investigate unsteady forces applied to rotor blades due to partial arc admission. Through the CFD analysis, fluctuations of aerodynamic forces are revealed. In order to verify the accuracy of the CFD analysis, an experiment of the air turbine is carried out under the same conditions as the CFD analysis. The comparison of turbine efficiency between the CFD analysis and the experiment is also discussed and they show good agreement.

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In order to prevent rain erosions of moving blades in a low-pressure stage of a steam turbine, removal of the water film by suction slots on the preceding stationary blades is generally considered to be one of the most effective methods. In this study, the efficiency of water film separation for several types of slits in different pressure conditions were thoroughly examined using an air blower test rig.

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The performance of variable speed radial inflow hydraulic turbines is affected by Coriolis forces. With increasing flow and rotational speed, the influence of the Coriolis force on hydraulic efficiency and performance stability becomes more significant. The performance equation for variable speed turbines is based on Newton's Law of Conservation of Energy and describes the balance between the static and the kinetic fluid energy. To define the influence of each form of energy the kinetic fluid energy is divided into translatory, rotatory and Coriolis energy. A desirable result it is that the Coriolis energy increases the hydraulic efficiency, but it is shown that Coriolis forces also cause the performance curves for constant rotational speed to cross each other, generating undesirable regional instabilities.

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It has been found in our past studies that the installation of asymmetric plate at the inlet of inducer is effective for the suppression of cavitation surge phenomenon. In the present study, the suction performance of 2-bladed helical inducer with an inlet asymmetric plate is experimentally investigated. It is observed that the suction performance in large flow rate conditions is not largely influenced by the asymmetric plate, whereas the head of inducer with the asymmetric plate increases just before head breakdown in partial flow conditions. The mechanism of this additional head is iscussed by one-dimensional streamtube model, which takes account of the inertia effect as well as cavitation characteristics of inducer such as mass flow gain factor.

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Mini turbo-pump is used in a wide range of fields, such as water-cooler for personal computer, fuel cells, and ventricular assist device. And there is demand for more compact and higher performance. But the design method for the mini turbo-pump is not established because the internal flow condition for the small-sized fluid machineries is not clarified and conventional theory is not applicable to small-sized pumps. In this study, the impeller having large blade outlet angle and splitter blades was designed and manufactured. The performance test was performed by the experiment and the numerical analysis. From the results, the performance and the internal flow were investigated about the rotor with and without splitter blades.

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Dynamic response of the fluid force acting on an axially oscillating radial impeller was numerically investigated. The impeller of a rocket engine turbopump was modeled to oscillate in the axial direction. The flow field around the impeller was divided into front and back clearance between rotor and casing, and each flow field was simulated using unsteady CFD simulation changing the oscillating frequency. From the fluid force of the simulation results, dynamic haracteristic coefficients, i.e., m, k, c, were calculated and compared between front and back shroud. It was found that the dynamic characteristic coefficients of fluid force acting on the front shroud were much smaller than back ones with balance piston.

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The rotordynamic fluid forces on a closed type centrifugal impeller in whirling motion were measured and simulated for two types of seal, a face seal and a wear ring seal. The rotordynamic fluid forces are destabilizing in the ranges of 0<Ω/ω<0.5 for the face seal and 0<Ω/ω for the wear ring seal, where Ω and co are a whirling speed and a rotational speed of the shaft, respectively. The characteristics of the rotordynamic fluid forces could be understood in consideration of a squeeze effect and the change of resistance of seal due to the eccentricity of the impeller for a swirling flow in the clearance between the front shroud of the impeller and the casing. In a low flow rate, a rotating stall occurred and changed the rotordynamic fluid force drastically around Ω/ω=0.7 for the face seal, 0.6<Ω/ω<0.9 for the wear ring seal.

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Fluid machineries for fluid food have been used in wide variety of field i.e. transportation, the filling, and improvement of the quality of fluid food. Although, flow conditions of it are quite complicated because fluid food is different from water. Therefore, the design method based on the internal flow conditions is not conducted. In this research, centrifugal pump for fluid food having semi-open impeller and small blade number was used to decrease shear loss and keep wide flow passage. In this paper, performances and internal flow conditions of pump having a general outlet blade angle 22.5 deg. using low viscous fluid were clarified by experimental and numerical analysis results.

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The machine Reynolds number and the specific speed of centrifugal blood pumps are lower than conventional pumps, therefore, it is difficult to apply a general design method to such centrifugal blood pumps. In this research, the influence that each part shape exerted on adult and pediatric blood pump performance were examined, moreover, the method of the design of pump that is appropriate for low specific speed and low mechanical Reynolds number pump were xamined. As a result, the efficiency of these pumps can be estimated using the specific speed considering viscosity.

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In our current research, the efficiency of a centrifugal blood pump for infants is about 30% or less at 2.0L/min. It is important to improve efficiency and to prevent blood trauma. In general, a positive displacement pump is suitable for the low specific speed. In this research, a single screw pump which has narrow gap between a rotor and a stator was designed to prevent blood trauma. The fundamental performance such as pump characteristic, leakage characteristic, and pump efficiency of this single screw blood pump was investigated.

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Left ventricular assist centrifugal blood pump is a kind of low specific speed pump. The improvement of efficiency is difficult. In general, a positive displacement pump is suitable for the low specific speed region. Three kinds of single screw pumps, which have narrow gap between a rotor and a stator, were designed to prevent blood trauma. In this research, the experiment and the numerical analysis were carried out for these pumps, and also the pump characteristics and the leakage characteristics were investigated.

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Displacement type pumps are often applied for micro-chemical plants, while the inherent pulsation natures of these pumps are undesirable to obtain efficient and continuous chemical reaction. We have proposed a multiple-disc pump as an alternative pump and have shown its effectiveness with much less pressure pulsations. In the present study, the effects of the shroud gap between the front disc and the casing on hydraulic performances and pulsation characteristics are investigated. It is found that pressure performance is not affected by the shroud gap, whereas there seems to be an optimal gap for the torque performance. Furthermore, the required torque with the smaller gaps significantly increases near the shut off condition, which is caused by partial collision of the front disc to the casing wall due to the insufficient stiffness of the front disc. The pressure pulsation with rotational frequency is also increased in this flow regime.

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