Confined swirling flows of aqueous polymer solutions due to a partially rotating disc in a cylindrical casing have been investigated using a flow visualization technique. The ratio of rotating disc radius R_d to container radius R_c, σ=R_d/R_c, was 0.4, 0.6 and 1.0. As the aqueous polymer solution, 0.5, 0.8 and 1.0wt% polyacrylamide (PAA) solutions were used. It was observed that at σ=0.4 and 0.6, the ring vortex was formed near the partial rotating disc and it was shed periodically for all the solution concentrations C tested, as well as at σ=1.0. Regardless of σ, the period of the vortex shedding seemed to increase with the Reynolds number Re_0. The diameter of the ring vortex B, which increased with the increase of Re_0, was roughly between 0.2 and 0.4 times the outer diameter of the rotating disc. Regardless of C or σ, the height of the vortex h was about 0.1 times the diameter of the rotating disc. The relation between the lower-critical Reynolds number for the ring vortex (Re_0)_c and the elastic number E_0 could be expressed by the equation, (Re_0)_c=10E_0^<-3/5> which was independent of σ.

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Confined swirling flows of aqueous polymer solutions due to a partially rotating disc in a cylindrical casing have been investigated using a PIV measurement. The ratio of rotating disc radius R_d to container radius R_c, σ=R_d/R_c, was 0.4, 0.6 and 1.0. As the aqueous polymer solution, 0.5wt% polyacrylamide (PAA) solution was used. The fluid within the ring vortex formed near the rotating disc rotates with semi-rigid rotation, where the angular velocity of the ring vortex was about 0.9 times that of the rotating disc. A high shear layer existed at the boundary between the ring vortex and the outer large-scale secondary flow, where the radial and axial distributions of both mean azimuthal and radial velocities were varied significantly. Outside of the high shear layer, both mean azimuthal and radial velocities were very small. In the region outside the ring vortex near the rotating axis, the fluid was slightly flowing in the direction opposite to the rotating disc. These characteristic flow behavior on the ring vortex was independent of σ. It was noted that at σ=0.4 and 0.6, the mean azimuthal velocity at the axial location of the radial-azimuthal section including the ring vortex approached almost zero in the radial direction in the region outside the ring vortex, while at σ=1.0, it has almost the half of the angular velocity of the rotating disc.

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As the second report of liquid crystal flow induced by annihilation of a pair of defects, we have numerically investigated both the transient behaviors of two defects with different structures and the velocity field, and estimated the magnitude of the induced velocity, using the Doi theory with the Marrucci-Greco potential. A defect with negative strength moves faster than that with positive strength. The effect of the long range order of the molecular orientation field on the annihilation time is considerably large, and the annihilation time is reduced with the increase in the magnitude of the long range order. It is clarified that flows are induced during the annihilation of a pair of defects and that several vortices are generated in the vicinity of defects. The maximum velocity is predicted spatially between the two defects just after the annihilation. In the present simulation, the maximum of the induced velocity reaches an order of 10μm/s. The induced velocity becomes large with the increase in the values of the long range order and the nematic potential strength.

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We have investigated phase transitions and internal aggregate structures of a highly dense suspension composed of magnetic plate-like particles with a magnetic moment normal to the particle axis, by means of the Monte Carlo method. In the present study, we have considered a quasi-2D system in order to clarify the influences of the volumetric fraction of particles and magnetic field strength on particle aggregations and phase transitions. Internal structures of particle aggregates have been discussed quantitatively in terms of pair correlation and orientational pair correlation functions. The main results obtained here are summarised as follows. When the influence of magnetic interactions between particles is of the same order of the magnetic field strength, the particles form column-like clusters, and the internal structure of a dispersion shows solid-like structures. As the magnetic field strength becomes strong, the internal structure of a dispersion is transformed from solid-like structures into isotropic ones. However, as the volumetric fraction increases, the particles form brick wall-like structures under circumstances of a strong applied magnetic field, and the internal structure of a dispersion exhibits solid-like ones.

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An optical measuring method to evaluate the fiber concentration has been developed for flowing pulp-suspensions. This method was applied to a fully-developed steady flow in ducts with a square cross section. The obtained results clarify quantitatively, in a definite form, the distributions of the fiber concentration that has long been an interesting subject of discussion among researchers. And also that shows availability of the method. Furthermore, it is found that the flow mechanism of pulp-suspension in ducts can be classified into five patterns. The degree of uniformity of the fiber concentration, that is suggested as the standard deviation of its distribution, is decreased from 0.3 to 0.05 with an increase of velocity for the test pulp suspensions of C_s=0.4〜0.8%.

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This work studies wave motions and mixing phenomena in an interfacial surface of two immiscible fluids between rotating cylinders, the inner cylinder is rotating and the outer cylinder is fixed. This report clarifies a series of waving and mixing phenomena by flow visualization technique. When the Reynolds number was increased, the interfacial surface became unstable due to the centrifugal force and consequently the surface swelled up around the inside wall of the outer cylinder. At last the swelled part of the surface was torn off and a droplet of a liquid penetrates into the other liquid. It was clarified that the amplitude of the swelled film of surface in axial direction was increased up to a certain value with the Reynolds number. The critical Reynolds number for the onset of the mixing was decreased with aspect ratio. However it was not depended on the ratio of the viscosities of the two-liquids.

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A second-moment closure proposed by Shima and Kobayashi (2007) is applied to turbulent boundary layers in adverse pressure gradients. The computation adopts a very simple 'standard' model for the ε transport equation. In spite of the simple scale-determining equation, the closure reproduces a case that is often used for testing turbulence models, i.e. the Samuel-Joubert flow in which a standard log law region exists. The model is also tested in equilibrium boundary layers of a recent DNS, in which the velocity profile in the log law region shifts downward from the standard law and the slope in that region becomes higher than that for the zero pressure gradient flow. The present model gives reasonable predictions for mild and moderate pressure gradient cases, but fails to capture a mean velocity profile for a strong gradient case. The Launder-Sharma k-ε model is also tested in these cases, and the performance is discussed.

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A turbulent plane jet with a chemical reaction (A+B→R) in a liquid is investigated experimentally. The instantaneous concentrations of all species (A, B, and R) are measured simultaneously by using the light absorption spectrometric method and the mass conservation law. Statistics of reactive scalar field are compared with those of nonreactive case (frozen limit) and those of instantaneous reaction case (equilibrium limit). It is ascertained that, in comparison with the frozen limit, the mean concentration of reactants A and B decrease while the mean concentration of product R increases in the downstream direction because of the chemical reaction. With regard to scalar fluctuations, it is also observed that, in the region near the exit of the jet, the r.m.s. values of species A become larger than those in the frozen limit, whereas the r.m.s. values of species B become smaller than those in the frozen limit, and vice versa in the downstream and outer region. Furthermore, the concentration correlations between species A and B have negative values. The segregation coefficients show the values between 0 and -0.3 on the jet centerline, and have minimum values at the location separated from the centerline in the cross-stream direction. The present data provide very useful and important information for modeling concentration correlation and the chemical source term in a turbulent reactive flow.

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The objective of this study was to clarify the unsteady characteristics of the fluid force acting on limbs during swimming. For this objective, an underwater robot arm, which has five degrees-of-freedom in order to perform the various complicated limb motions during swimming, was developed. In the previous study, an experiment to measure the unsteady fluid force was conducted for four swimming strokes of the upper and lower limbs. In this paper, the unsteady fluid force model was firstly formulated. Second, the simulation of experimental conditions was conducted. Two fluid force coefficients, which are the parameters in the fluid force model, were identified using optimizing calculation, so that the discrepancy of the forces and moments between the experiment and simulation was minimized. In addition, the fluid force models which depend only on limb's shape were determined. A good agreement between the experiment and simulation with the determined fluid force model indicated validity of the determined model. The identified fluid model will be useful for mechanical analyses of various swimming motions in the future studies.

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Single-blade centrifugal pump is used as a sewage pump widely. However, hydraulic losses increase because the impeller width is large as for single-blade centrifugal pump. It is extremely complicated, besides, because the internal flow of single-blade centrifugal pump changes greatly by an impeller position and changes by the flow rate. Therefore, a quantitative prediction and the elucidation of the generation mechanism of unsteady hydraulic losses are expected to make this kind of pump high efficiency. In this study, loss analysis was performed about two kinds of single-blade centrifugal impeller with different impeller outlet angle. As a result, the effect of the impeller outlet angle which gave it to performance and hydraulic losses was clarified. Furthermore, the momentary behavior of performance and hydraulic losses was shown, and their relations with the impeller inlet and outlet flow became clear.

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Numerical simulations have proved that spatially coherent wave power energy can be accumulated in a special transducer by using multiple, small, globally coupled oscillators that can implement the Grover wave algorithm. The most efficient power concentration can be achieved under temporarily random but simultaneous spatially uniform external forces. However, in the case of spatially random external forces, no power concentrations was observed in the calculation. Since the fluctuation of wind and wave power have exhibit spatial correlation, this mechanism can be utilized to increase the efficiency of power generation by concentrating spatially distributed natural power into one localized generator.

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Polymer electrolyte fuel cells (PEFCs) generally have external humidifiers to supply humidified hydrogen and oxidant gases. If a PEFC could be operated under very low humidity condition, external humidifiers may be removed, resulting in a very simplified PEFC system with increased total efficiency and reduced cost. The present study was carried out to clarify the influence of anode gas recirculation on the PEFC performance under no-humidification at the cathode. Increasing the flow rate of anode gas recirculation is effective to improve water transport from the anode gas to the membrane electrode assembly (MEA), enhancing the PEFC performance. Increasing humidity of the anode supplied gas is also effective to enhance the PEFC performance without an increase in concentration overpotential caused by flooding at high current densities. For the cathode GDL, it is important to maintain humidity and prevent drying-out of the MEA. A microporous layer (MPL) coated GDL is effective for enhancing the PEFC performance. For the anode GDL, it is important to increase water transport from the humidified anode gas to the MEA. The anode GDL without the MPL is effective for enhancing the PEFC performance.

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Gas diffusion layers (GDLs) coated with a microporous layer (MPL) have been commonly used to improve the water management property of polymer electrolyte fuel cells (PEFCs). In the present study, the influence of the PTFE content in the MPL on hydrophobicity and PEFC performance was evaluated. The maximum pore diameter of the GDL was measured using an air permeability test apparatus in which a low surface tension wetting liquid filled the pores of the GDL. A water permeability test was also carried out using the same apparatus. When the maximum pore diameter measured using the water permeability test was assumed to be the same value as that measured using the air permeability test, the contact angle inside the GDL pore could be accurately estimated. Increasing the PTFE content in the MPL extends the contact angle, which enhances the hydrophobic property of the GDL. Under low humidity conditions, decreasing the PTFE content is effective for preventing drying-out of the MEA, enhancing PEFC performance. Under high humidity conditions, increasing the PTFE content to 20 mass% is effective for preventing flooding, enhancing PEFC performance. However, when the PTFE content becomes too high, PEFC performance tends to decrease.

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Instantaneous and simultaneous measurements of two-dimensional mixing behavior of air and fuel and temperature distributions was conducted by combining acetone LIF and Rayleigh scattering methods. This technique was applied to a partially premixed turbulent flame of CH_4/N_2 fuel using a single pulse and a 266nm beam of Nd: YAG laser. The measured fuel concentration distribution corresponds to the temperature profile in each reaction zone. That is a useful way of investigating characteristics of the reaction zone. Comparing the measured results and the CH_4 concentration which is derived by assuming to mix fuel and air homogeneously and the adiabatic flame temperature in chemical equilibrium, we cleared the validity of the measurement method. Additionally, in a reaction zone where variations of temperature and species concentration affect LIF intensity, we predicted the CH_4 concentration corresponding to the measured temperature assuming perfectly premixed laminar flames, and confirmed the predicted values are close to the measured ones.

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Based on the qualitative consideration that the flow continuance in the combustor may play an important role not only in combustion enhancement but also in heat transfer enhancement, main attention will be paid on it in the cooling period after the pressure in the combustion chamber attains its maximum. Three types of constant volume combustors are used; a cylindrical combustor with a hemi-sphere-shaped divided chamber, a cylindrical combustor with a pan-cake-shaped divided chamber, and a fan-stirred combustor. A simple cylindrical-shaped combustor is also used for obtaining standard combustion characteristics. Enhancement behaviors of combustion and heat transfer are examined by analyzing the pressure histories after the spark ignition. Flow visualization is also made of the flow pattern in the fan-stirred combustor. It is found that the fan-stirred combustor can realize and maintain a complex flow pattern in the cooling period, and that it combines strong heat transfer enhancement effects with moderate combustion enhancement effects.

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In recent years, athletic humanoid robots have been popular, but the electrical motors equipped in their joints and heavy batteries do not allow them the more quick actions. Another type of actuators of light, compact and no-auxiliary, are required to bring them more quick motion. In this study, novel combustion linear actuator, which stores once a combustion driving force to springs as mechanical energy, was developed. First, a high-speed direct observations of the combustion behavior in a model constant volume chamber was carried out for a high performance combustion condition. Second, to verify the performance of the actuator for heavy load, an operational test of lifting was made. The test showed the successful lift performance for 27kg mass par an unit. Prototype model of full-scale jumping robot, which is planed to be driven by the actuators, is also shown in this paper.

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We examined relations between the shape of the staged air nozzle (after air port) and the mixing performance in the furnace for two staged combustion. Four different shapes of ports, 1 hole, 4 holes, 9 holes, Lobe shape, with the same open area of nozzle outlet were used to examine the effect on the NO_x and CO performance. The gas velocity in the furnace and the air ratio were fixed at the values near the operating condition of the actual boilers as much as possible. NO_x and CO performance was correlated with the mixing performance in the downstream side of the after air port. CO decrease when the standard deviation of the local air ratio in the furnace become small. This is because extremely low oxygen concentration region is hard to be formed in the furnace. On the other hand, NO_x increase if the standard deviation of that is small. The overall air ratio was set at 1.15 for the experimental condition. Under this condition, improvement of mixing performance brings an increase of thermal NO_x because of higher gas temperature. We also examined the nozzle design criteria in order to predict its mixing performance beforehand. It was found that the circumference length of the jet flow had a good correlation with the standard deviation of the local air ratio. When a nozzle has a longer circumference length, mixing performance of it becomes better.

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Aiming to understand applicable component of biomass gas to HCCI engines, combustion characteristics were investigated experimentally for mock biomass gas with varying fuel components. Mock biomass gases consisted of H_2, CH_4, CO, N_2 and CO_2 were used assuming wood pyrolysis gases. Using modified gas engine with air inlet heaters and high compression ratio pistons, experiments were carried out. Auto-ignition timing is temperature domain regardless of fuel component, ignition temperature is about 1000K as same as hydrocarbon fuels. Combustion speed following auto-ignition is influenced largely on H_2 and CO_2 content, it is clarified that combustion speed is proportional to H_2 and CO_2 ratio of fuel. Meanwhile CO of fuels does not effect on combustion speed. H_2 and CO_2 ratio of fuel is also largely concerned with knock, and it is one of index of minimum IMEP that knock yield. About Exhaust emissions, THC and CO is higher level because of lower cyclic maximum temperature for inert component of fuel, in another hand, NO_x is near zero regardless of fuel components and operation conditions.

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The purpose of this study is to investigate combustion robustness of HCCI engines at retarded combustion phasing operation by going through numerical analysis with multi-zone model. The reason of calculation with the multi-zone model is to examine the mechanism of combustion phasing retard to reduce an excessive pressure-rise rate and keep combustion robustness with thermal stratification. It is found that excessive combustion phasing retard causes cyclic dispersion and misfire. With thermal stratification, combustion robustness at retarded combustion phasing operation is analyzed. As a result, in case of same initial mass averaged gas temperature as larger thermal stratification was set, 50% heat release timing of high temperature heat release (HTHR) was advanced because higher initial gas temperature zone was auto-ignited in turn. It was confirmed to trade off between pressure-rise rate and 50% heat release timing in HTHR.

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In order to improve the fuel properties and diesel exhaust emissions of waste vegetable oil methyl ester (WME), the blend fuels (BWME) of WME with 1-butanol are tested using a DI diesel engine. The 1-butanol content in BWME is 5 to 20 mass%. The pour point of BWME with 10 mass/1-butanol is-12.5℃ and the same as that of JIS No. 2 gas oil. There is no problem in the startability and stability of the engine operation with BWME. Thermal efficiency of BWME is almost the same as that of the gas oil. Although BWME has longer ignition delay compared with gas oil and WME due to the low cetane number of 1-butanol, the combustion end timing of BWME is same. The smoke emissions decrease with increasing 1-butanol content although the HC and CO emissions of BWME increase due to the longer ignition delay. From the experimental results, it is concluded that BWME is an alternative diesel fuel and is better than WME because of the lower pour point and the lower smoke emissions.

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In order to clarify the effect of heterogeneity of distributions of temperature and oxygen concentration in a combustion chamber induced by EGR on the soot and NO emissions from the diesel engine, the combustion characteristics and emissions of diesel spray flame achieved in a rapid compression machine (RCM) at various patterns of temperature and oxygen concentration distributions in the chamber are investigated. Results indicate that the NO_x and soot emissions from diesel combustion are governed mainly by the amounts of oxygen and enthalpy entrained into the spray upstream the ignition region, when the temperature distribution and oxygen concentration distribution in a chamber are changed with keeping the total amounts of oxygen and enthalpy of surrounding gas in a chamber at constants.

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We have investigated fluid flow characteristics of liquid film flow rising along the outer surface of the rotating cone. The fluid is given a centrifugal force due to the rotation of cone, while strong surface tension maintains the centrifugal force at the outer surface of the liquid film flow. Therefore, the fluid does not spread outward the cone, but goes up along it. We have visualized the interesting flow phenomena with a high-speed video camera. In addition, we have measured the correlation between the wetted radius, rotation and flow rates of rising film flow.

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