The bi-directional impulse turbine and the bi-directional flow collector for tidal energy conversion is investigated in this paper. The bi-directional impulse turbine with fixed guide vanes is adopted because the turbine has a large efficiency. The turbine characteristics of the combined system of impulse turbine and collector are investigated by using the water tunnel. This system is proved to produce the power by a tidal flow experimentally. Three types of collector A, B and C are investigated, where the maximum radius of collector A is the smallest, and collector B has a straight part and a semicircular brim part. In addition, the effect of hub-to-tip ratio on the performance of the turbine system is investigated.

We proposed the new type turbine, double rotor turbine, for OWC to improve the performances of starting characteristics and efficiency. The splitter plate of the double rotor turbine is the most important part that divides the flow into Wells or Impulse rotor. It is discussed the influence of the splitter duct length to the performances. The original length is based from the estimation of oncoming flow coefficient to each rotor. The length is gradually shorter and 0.75, 0.5,0.25 and 0 times of the original duct length. A torque is gradually decreased with the splitter duct shorter, but the variation is small. The starting characteristics is improved from the wells turbine at all duct length. The efficiency becomes maximum at 0.5 length. The variation of the efficiency with the flow rate is almost same to the duct length.

In a wave energy plant with oscillating water column (OWC), an air turbine is adopted as an energy conversion device. The counter-rotating impulse turbine for wave energy conversion has been proposed by M. E. McCormick in 1978. In a previous study, authors investigated the effect of turbine geometry on the performance, and clarified that the efficiency of this turbine is higher than single rotor impulse turbine in the range of high flow coefficients. In this study, the pitch-controlled guide vanes were installed in order to achieve a further improvement in the performance of a counter-rotating impulse turbine, and the effect of guide vanes on turbine characteristics was investigated by using the computation fluid dynamic (CFD) analyses. As a result, it was found that the effect of the setting angle of the guide vanes has significant influence on the turbine performance, and inlet and outlet setting angle of θi=22.5° and θo=45°, respectively, obtained the better efficiency.

The Wells turbine has long been used as a secondary converter for wave energy conversion. In order to alleviate the stall problem of this turbine, the authors have proposed a Wells turbine with booster. In the present study, the counter-rotating impulse turbine for wave energy conversion, developed by M. E. McCormick of the United States Naval Academy, was proposed as a booster turbine. This turbine shown a better efficiency than an impulse turbine with single rotor in a previous numerical analysis. In this study, the Wells turbine with a counter-rotating impulse turbine was simulated to investigate the fluid dynamic performance by using CFD analysis. As a result, the stall characteristics of Wells turbine shown a little improvement by installing the counter-rotating impulse turbine. Further, it was found that, as a booster, the impulse turbine with single rotor is more efficiency than the counter-rotating impulse turbine.

The rotor of Wells turbine consists of several symmetrical airfoils positioned around a hub with their chord planes normal to rotational axis. In general, two-dimensional blade is used as the airfoil of Wells turbine. In the present paper the attention is focused on the effect of plasma actuator on aerodynamic sound radiated from two-dimensional airfoil. We measured the aerodynamic sound radiated from the airfoil with plasma actuator near the trailing edge of the airfoil. At the normal airfoil, discrete frequency noise clearly observed at small attack angle for Re=0.9×10⁵～1.2×10⁵. The plasma actuator was effective to reduce the discrete frequency noise radiated from airfoil. This noise depended on the actuator location, geometry of electrode, applied frequency, the electrode length of plasma actuator. We have discussed the effective geometry to reduce the discrete frequency noise.

In the recent years, coke drum application is increasing due to an urgent needs to convert the coke deposit into more valuable products. In this resea rch the performance of hot box attached at shell-to-skirt junction was investigated numerically. Hot box is a triangular cavity in the shell -to-skirt portion, which be added to enhance heat transfer from shell area to skirt area and reduce temperature diff erence between this two areas due to natural convection inside hot box. From the strain gauge and thermocouples data it was found that temperature difference between shell and skirt junction and strain history have the same trend. During preheating stage, maximum temperature with coke drum attachment is decreasing as well as minimum temperature during cooling stage. Because strain is the function of temperature difference and coefficient of thermal expansion, it is believed that the strain will be reduced a s well. From this research it was found that hot box can reduce temperature difference during preheating stage for about 30°C and 20°C during cooling stage respectively.

Data center is a facility that consumes a lot of energy, and about half of energy is used for the cooling system. Therefore, in order to reduce the electricity consumed, we have been developing a cooling system that combines snow and spray. This research focused on spray cooling. Aiming at practical application to data centers requiring a large amount of air conditioning, micro mist which is easy to vaporize was used. Considering the use situation at the facility, We produced a spraying device aiming at a compact size and a vaporization efficiency of 100%.

The paper describes a new active controlled multi-fan wind tunnel with cost reduction to generate natural turbulence wind. We plan to use it for measuring wind turbine performance in laboratory. The wind tunnel is consisted of 100 driving fans that is controlled by an original ICT embedded system. The fluctuating velocity wind is successfully generated with mean velocity 7m/s, turbulent intensity 2% and turbulent integral scale 5, 10, 20m, which is based on Karman’s power spectrum density function. In particular, the wind is well satisfy the Kolmogorov’s -5/3 multiplication rule of inertial subrange with frequency 0.01~2.0Hz. Furthermore, performance of a wind turbine in steady and natural winds is shown as example of usage of the wind tunnel.

In this paper, numerical results of flow around a square cylinder and of cavity flow by using Lattice Boltzman Method (LBM) are reported. The calculation is performed with a two models of D3Q15 and D3Q19 under Reynolds number of 140 for the square cylinder flow and of 800, 1600, 3200 and 1.0 x 104 for the cavity flow. In the case of the square cylinder flow calculation, the results of LBM with the D3Q15 are compared to that of the calculation by finite element method based on Navier-Stokes’ equation (NS-FEM) for incompressible flow in the laminar flow field. In the case of the cavity flow calculation, the results of LBM with the D3Q15 and D3Q19 are compared to that of the calculation of the NS-FEM and the measurement by Parasad and Koseff in the laminar and the turbulent flow field.

Flow-induced acoustic resonances in steam piping with closed side branches cause severe structural vibration and fatigue damage of piping and components in many industrial applications such as power plants. The steam state in the steam piping of power plants is not only dry steam but also wet steam. From our previous experiments under low-pressure wet steam flow, the resonance frequencies, which is important parameter to predict acoustic resonance, under wet steam obtained by the theoretical equation and assuming a saturated sound speed were within ±6% of the measured values. However, the static pressure in practical steam piping is often higher than that in our previous experiments. In this study, we conducted experiments on acoustic resonance in a single side branch under a high-quality wet steam flow with the static pressure as parameters to investigate the effects of the static pressure on acoustic resonance frequency under wet steam flow.

It has been confirmed that the taper cylinder has large effect of aerodynamic noise reduction as compared with the circular cylinder. Then, the structure of wake which contributes to Aeolian tone was investigated in detail by using a hot wire anemometer. The integral length scale of the wake was calculated by the cross-correlation measurement and compared with the spectra of the aerodynamic noise. As a result, it was confirmed that in the tapered cylinder, the vortex scale changes depending on the span direction position. Also, it was considered that the von Karman vortices did not occur in the wake of the tapered cylinder and it was observed of decreasing of the peak level in the sound spectra.

In large-scale plants including oil refining plants, occurrence of accidents that cause crucial damage to piping systems has been reported so far. As one of the reasons for this phenomenon, acoustically induced vibration (AIV) is pointed out. AIV is vibration caused by a broad-band sound generated from a differential pressure regulating valve in the piping system. The pipe is excited by the sound and the pipe and the gas in pipe vibrate sympathetically, which leads tofatigue failure of the pipe. This study focuses on AIV phenomena and aims at clarifying the mechanism of AIV. A relation between wave numbers and vibration modes of air column in the pipe is analyzed as well as that of the pipe itself by a modal analysis using the finite element method. Additionally, a resonance phenomenon is discussed between the pipe and the air column.

This study deals with aerodynamic noise generated from perforated metal plate. Perforated metal plate has two flow direction and the aerodynamic noise are varied by flow direction. At the expansion direction, large prominent peak in the frequency characteristics is observed. That prominent peaks are observed in the experience by only one hole. In the experiment, velocity fluctuation of jet flow issuing from the hole is measured by a hotwire anemometer. Distribution of sound source is expected by numerical value of coherent output power (COP) calculated by velocity fluctuation and coherence function. Coherence function is defined between generated noise and velocity of jet flow. The result discovers distribution of sound sources are different by frequency of prominent peaks and interference of jet flow makes prominent peak disappeared and enlarged.

Since a rocket engine exhaust has a high Mach number and a high temperature, it is difficult to predict accurately acoustic characteristics. In this paper, we experimentally evaluated the acoustic characteristics of a hybrid rocket using N₂O self-pressurizing system. The sound power generated by the rocket engine was directly proportional to the cube of the effective exhaust velocity. The sound has dominant frequency of 100 Hz and 1300 Hz in the directions of 90 degree. During the firing of the hybrid rocket engine, two directional peaks of the sound pressure level were observed in the directions of 40 degree and 70 degree.

In this study, we clarify the influence of the total number and resolution of the computational grids on the accuracy of the numerical analysis by using the large eddy simulation for a small box fan. We analyze the accuracy by using four computational grids with different resolutions and total numbers of the grids. These grids have different resolution in the outlet region and the grid type near the blade-wall surface. As a result, application of the prism-type mesh near the blade-wall surface has been found crucial for resolving thin laminar boundary layers, and thus improving the prediction accuracy of the performance curve. The grid resolution in the wake region has less influence on the prediction accuracy of the aerodynamic noise.

Recently, it has been a problem of aerodynamic noise radiated from airfoils. Therefore, the authors made wind tunnel tests to measure airfoil noise and static pressure on an airfoil (NACA0012 model) in turbulent flow. In additon, the authors made Large Eddy Simulation to simulate vorticity distributions around airfoil and airfoil noise. In this study, the authors use an airfoil and a cylinder to examine influences of vortices with a particular size and fluctuation. Then, the authors measured and simulated airfoil noise and static pressure in varying position in the vertical direction (-10 to +10 mm) of the cylinder placed in the upstream side of the airfoil to change interference position. As a result, it has become clear that airfoil nose is increased when interference position is in the stagnation point. And the airfoil has larger pressure fluctuation at leading edge in this case.

The axial blower having a two dimensional stator at the inlet and the outlet of the rotor is used for a base model in this stydy. We designed the high performance model with higher pressure and higher efficiency than the base model. The inlet stator and the outlet stator of the high performance model is three dimensions to make high pressure and high efficiency. In addition, we investigate performance and an internal flow by using numerical flow analysis. Consequently, we aim for the development of the blower which is light weight and energy saving than a conventional axial blower.

IGV-less single stage centrifugal blower was developed to increase the total performance for lower-flow-rate operation condition. Recirculating casing treatment technique was used for the operation range enhancement. The casing treatment extended the operation range 11% than conventional case. The casing treatment could prevent the stall occurrence and extended the range. By using the casing treatment, the total blower efficiency on actual plant operation condition at lower-flow-rate operation was increased.

Axial Counter Rotating Fan is the technology that can obtain a high pressure ratio and high mass flow rate compared to a normal axial fan. However, there is no example that has been put into practical use because the adiabatic efficiency decreases in the supersonic region. Therefore, in this research, improvement of the adiabatic efficiency reduction phenomenon in the supersonic region is the final objective. Numerical analysis was carried out using ANSYS CFX. As a result, the efficiency characteristics in the region where the relative speed of the first stage fan and the second stage fan reaches supersonic speed are clarified.

In this paper, the turbulent flow field in a stator cascade of a multi-stage transonic axial compressor have been investigated using large-scale unsteady simulation including LES and DES analysis. The flow field was analyzed by data mining techniques including vortex identification based on the critical point theory and topological data analysis of the limiting streamline pattern visualized by the line integral convolution (LIC) method. It is found that hub-corner separation occurs in the first stator and interacts with the shock wave from the second rotor and the wake from the first rotor. Although only one hub-corner separation vortex is formed in the time-averaged flow field, hub-corner separation vortex is generated in multiple pieces in an instantaneous flow field and those pieces fluctuate with time violently, distorting the near-hub flow.

In order to improve the launch capability of a rocket, highly efficient turbine system is required. In this study optimization of the turbine system is made using an algorithm based on two-dimensional (2D) flow analysis. In addition, three-dimensional (3D) flow analysis is performed by selecting 30 test randomly case. Any big qualitative difference between two-dimensional (2D) analysis and three-dimensional (3D) analysis did not occur much. Due to the three-dimensionality, with high-efficiency blades, the detached shock wave at the leading edge of the first-stage rotor blade is weakened and the leakage flow increased. Since the increase and the decrease of the loss occurred at the same time, the turbine efficiency did not change.

In high speed turbopumps, various types of cavitations such as a blade surface cavitation, a tip leakage vortex cavitation, and a backflow vortex cavitation occur. When the cavitations response to encourage fluctuations of a pressure and a flow rate, the oscillation of the flow rate called a cavitation surge can occur. Therefore, clarifications of the dynamic characteristics of cavitations are desired to obtain higher reliability of turbopumps. Focusing on the blade surface cavitation as one of fundamental cavitations, we investigated unsteady characteristics of the blade surface cavitation in a flat plate hydrofoil, the Clark-Y 11.7% hydrofoil, and the NACA0015 hydrofoil in experiments. Several interesting characteristics of the blade surface cavitation were clarified.

For general use turbopump inducers, high suction performance is required in a wide flow rate range including the cutoff point. Reduction of the blade inlet angle for suppression of inlet backflow at low flow rates, while the inlet throat area should be kept large for high suction performance at high flow rates. In this study, to suffice these contradictory requirements, a splitter blade was adopted and its effect was investigated by CFD considering cavitation. As a result, the inlet back flow was successively reduced at low flow rates without significant suction performance deterioration.

When cryogenic fluid such as liquid hydrogen is transported by pump, the thermodynamic effect of the cavitation strikingly occurs. In addition, it is known that its suction performance shows characteristics different from that when water is used as working fluid has been done.

In this study, we developed a pump system pumping liquid nitrogen, and comparison the pressure distribution inside the pump when using water and liquid nitrogen as the working fluid, the purpose is to clarify the influence of the thermodynamic effect of cavitation on the suction performance.

In this report, outline of pump system capable of pumping liquid nitrogen is shown, and the pump suction performance when water is used as a working fluid, which is a reference when liquid nitrogen is used, was examined by experiment and CFD, respectively.

A mathematical model using bubble size distribution was developed for a cryogenic high-speed cavitating flow in turbomachinery. In this model, bubble growth/shrinkage is solved for each class of bubble mass (as an accurate expression of bubble size) when bubbles with various masses mix in the same spatially discretized calculation region. The bubble growth/shrinkage calculations employ a combination of two rigorous methods: a Rayleigh–Plesset equation for the bubbles’ oscillation, and a heat conduction equation for a thermal boundary layer around a bubble to evaluate the mass rate of evaporation or condensation. The mathematical model of cavitation has potential to contribute to fidelity in simulation for studying turbomachinery when considering a fluid with a strong thermodynamic effect.

This paper describes attempts to optimize flow control devices (Dimple), which was invented by one of the authors for achieving better film cooling performance of gas turbine cooling holes. In the past study, it was confirmed that film cooling performance can be improved by adding flow control devices (DFCD) which is a three-dimensional protrusion shape. However, it was also identified that DFCD did not perform well at high density ratio and low blowing ratio condition, i.e., DR=1.53 and BR=0.5. Therefore, in this research, we devised Dimple type device which is three dimensional dimple shape newly, and worked on Dimple shape optimization under high density ratio and low blowing ratio condition.

When using CFD for the designing of fluid equipment, turbulence model is frequently used. However the accuracy of analysis is not sufficient in some cases when complicated flow separation is occurred. Therefore, it is important to select appropriate turbulence model and consider boundary layer development. In this study, we conducted numerical analyses for turbulent flow in a square sectioned U-bend duct in which flow separation is occurred due to strong curvature and tested two turbulence models and two inlet boundary conditions. Then we compared computations and measurements and it was revealed that separation region tended to be overpredicted under uniform inlet flow conditions regardless of turbulence model.

This paper presents the vortex dynamics in a stirred tank mixer by rotating jet. Co-rotating vortices generated by neighboring jets merge into a single axisymmetric vortex. A short-wave perturbation during merging process provides an unstable counter-rotating vortex pair. The counter-rotating vortex pair generates a vortex shedding in the radial flow direction which gives oscillatory fluctuation on the flow field.

Ability of circular shaped sublayer plate has been examined for simultaneous measurement of magnitude and orientation of the local wall shear stress. Improvement of angular resolution was proposed with multiple 6 pressure taps around the circular shaped sublayer plate. A single calibration curve successful represents relation of the wall shear stress and pressure difference for 2.4<h⁺<14.9 and D=10[mm]. If the plate is submerged in the linear sublayer, detection sensitivity of the sublayer plate is slightly larger than Razor blade method. Defining ratio of static pressure of the multiple pressure taps, the angular resolution can be improved around 0 degree in attack angle of wall flow.

It is known that when the wind flows at the upper part of the cavity at high speed, a resonance sound is generated in the cavity. We found that resonance sound was derived from the position of the groove aligned at the bottom of the cavity on the surface of rotating body. For this phenomenon, the flow characteristics in the cavity at a time when resonance sound was generated were clarified, and the shape of the cavity which did not generate the resonance were investigated. This paper describes some of the results of the investigation based on a CFD(Computational Fluid Dynamics) analysis.

Internal flow of an engine for a supersonic aircraft is complicated path with merge and branch. In the previous research, we have tried to build 1-D internal flow network to grasp and evaluate internal flow conditions. We also conducted cold run tests to investigate pressure, temperature and rotor vibration of the engine. Improvement of prediction accuracy of internal flow rate of each paths and making appropriate flow direction are required for the engine test driven by hot gas in the future. In this study, the design concepts for improvement of the internal flow network built in the previous report and the investigation progress of the internal flow is reported.

In this study, a new temperature modulation model based on the heat transfer analysis was constructed for CFD analysis of the interaction phenomena between the shock wave and the discharge plasma. The constructed temperature modulation model was compared with the conventional simple Gaussian model. As a result, in the newly constructed model, the higher temperature region between the upper and lower wall was observed. This is caused by the heat conduction due to the heat flux originated from the electrodes. Based on the present results, by implementing this developed temperature modulation field model in CFD analysis, it is expected that more precise results to reproduce the actual phenomena can be obtained.

In this study, the feasibility study for the temperature measurement method of the discharged field was conducted by using the CFD analysis. As a result, the estimated temperature by applying the Riemann problem can reproduce the temperature given as a initial condition for the CFD within at most 10% error. From this investigation, it is expected to apply this method to the experimental measurement. Especially, by combing with the high-speed camera visualization, it is expected to improve the experiment efficiency by conducting the two-dimensional measurement. Also, it is necessary to investigate the experimental accuracy of this technique by comparing the other measurement method such as the spectroscopic technique for the representative region.

Hot-wire anemometer is used for turbulence measurements in the incompressible flow. To apply to the compressible flow, hot-wire anemometer was calibrated in jet of the compressible flow. Using it, Influence of geometry on mixing effect of gas injecting supersonic flow was clarified. TypeB Tips promoted mixture at x=10mm, y=10mm and x=30mm, y=15mm. TypeA and TypeB Crest showed similar mixing characteristic.

In this study, as a preliminary step of supersonic nozzle performance prediction for designing the cleaning device with air nozzle, numerical analysis of two-dimensional nozzle flow was conducted. In this paper, CFD analysis of supersonic flow in two dimensions was performed as a preliminary stage. As a result of comparison between theoretical solution and numerical result, agreement between the numerical and the theoretical results can be observed, even though some slight discrepancy appeared. This discrepancy is caused by the fact that the theoretical solution is quasi-one-dimensional, whereas the numerical solution is two-dimensional. In the future, incorporation of subsonic boundary conditions into simulation code should be conducted for the extension of the robustness for the analysis code.

The present study numerically investigates the formation mechanism of a tulip-shaped flame observed in a high aspect ratio rectangular channel. The compressible Navier-Stokes equations are solved with a detailed chemical kinetics mechanism of hydrogen. The result indicates that a first trigger for the tulip flame formation is a vortex generation near the left end-wall during the initial stage of a finger-shaped flame development. A large vortex structure produced in the burnt region interacts with the propagating flame front and the vortex-induced acceleration and deceleration of the flame front consequently forms the tulip-shaped flame. The interaction of pressure waves with the flame front affects a flame instability and flame propagation behavior. However, the flame instability may have no significant influence on the formation of tulip-shaped flame in the present condition.

This paper reports a preliminary experimental result of a supersonic free-flight ring-shape model for understanding of flow field in stunted Busemann intakes by using ballistic range at Institute of Fluid Science, Tohoku University. The ring-shape model is launched by the ballistic range. The flow field around a supersonic free-flight ring-shaped model is visualized by shadowgraph method, and recorded by a high-speed camera. The ring-shaped model is separated from the sabot, shock wave is generated thorough a supersonic free-flight ring-shaped model.

High order Euler simulations are conducted to investigate suppressing method of jet winds associated with shock waves generated by a blast wave generator, and occurrence factors of the jet winds and influences of a volume of the driver section and the nozzle angle are discussed. The results show that the jet wind is caused by a vortex which occurs at the nozzle edge and can be reduced by decreasing the volume of the driver section. Furthermore, in the present computational cases, using the moderate nozzle angle (1.71 deg.) reduces the jet wind near the nozzle exit and using the large nozzle angle (6.51 deg.) reduces jet wind at the place distant from the nozzle exit. These result show reducing the driver section and using the proper nozzle angle depending on the distance from nozzle exit are effective for reducing the jet wind.

The objective of this study is to investigate the decreasing ambient pressure at nozzle exit. If there is a sudden expansion section in supersonic ow at the Laval nozzle exit, phenomenon of decreasing pressure will occur at the downstream. Using this phenomenon to decrease the ambient pressure, the cover that can expand the tube area is placed at nozzle exit. Mach number of ow through the inside of nozzle and cover increase as the ratio of stagnation pressure and ambient pressure rise up. In this paper, we present the results obtained from numerical analysis of ow expansion and increasing of Mach number by the cover and the decrease of the pressure at nozzle because of the difference in pressure ratio.

A supersonic oscillatory flow is controlled using a small oscillatory jet. The jet is discharged from a small orifice whose diameter is 1.4 mm. The jet oscillation is induced by a cylindrical cavity placed upstream from the orifice. A Mach 1.84 supersonic flow past a rectangular cavity is selected as a test flow and the pressure oscillation is measured using a semiconductor-type pressure transducer placed downstream from the trailing edge of the cavity. All the sharp peaks observed in the pressure oscillation spectrum are weakened adding the oscillatory small jet to the flow although only two peaks are weakened using a non-oscillatory jet.

Marine creatures in ballast water of a ship may destroy the marine ecosystem. Abe et al. proposed a ballast water treatment system using the interaction between air bubbles and shock waves. We develop a numerical method on compressible air-water two-phase flow by using the Volume of Fluid Method (VOF) and Ghost Fluid Method (GFM), and the Riemann solver with surface tension term, we simulate the interaction with and without surface tension with various bubble radius. As a result, we clarify the surface tension effect for small micro-bubble.

In this study, drag efficient was calculated based on the DSMC method, for the investigation of the flight path analysis of the aerocaputure mission. In DSMC method, rotational and vibrational energy exchange for CO molecules was considered. In the free molecular region, drag coefficient is calculated with canceling the collision routine of the DSMC method. As a result, in the free molecular region, the drag coefficient calculated by the DSMC method agreed with the theoretical one. Also, the relationship between the Knudsen number and the drag coefficient was observed.

A thin-membrane inflatable aeroshell has been developed as one of the innovative reentry technologies. A suborbital reentry demonstration using a sounding rocket was conducted in 2012. Contrary to the result of a preliminary study, the vehicle always had an angle of attack (AoA) during its reentry. In addition, attitude instability such as increase in amplitude of AoA and vertical rotation was observed. To clarify the cause of attitude instability, we numerically investigated the dynamic stability of a forced oscillating vehicle, where a large eddy simulation technique with the standard Smagorinsky model was applied. In the trajectory of the CM with respect to AoA, hysteresis in one cycle was observed. The discussion of detailed stability and the analysis for the subsonic region are future works.

Dynamic instability of Hayabusa-type reentry capsule, which is one of the severe problems during atmospheric reentry, was observed in transonic and subsonic regimes. To investigate aerodynamic instability, numerical analysis of flow fields around the capsule was carried out for a case of freestream Mach number of 1.1. In this analysis, large eddy simulation (LES) technique was performed and the standard Smagorinsky model was applied. According to results of the relation between angle of attack and pitching moment coefficient (Cm), it was clarified that the higher frequency component of Cm behavior, which is attributed to turbulence of the wake, is important for aerodynamic instability. Therefore, it was indicated that detail investigation for turbulence fluctuation is necessary.

For accurate landing/splashing down in atmospheric reentry phase, it is required to mitigate radio frequency blackout, which is a communication cut-off phenomenon. So far, various mitigation methods have been proposed. In this study, mitigation of radio frequency blackout using surface catalytic effect was investigated by numerical analysis of plasma flow. Plasma flows around ESA ARD were reconstructed using a computational fluid dynamics technique. Computed results between non-catalytic and fully-catalytic wall cases were compared. For the fully-catalytic wall case, it was indicated that number density of electrons in wake of the ESA ARD largely reduces.

Injection flow characteristics of visco-elastic fluids from a nozzle into air have been investigated. As viscoelastic fluids, the dilute solutions of polyethylene oxide, of hydroxypropylcellulose and of polyacrylic acid were used. The injection filaments formed in the downstream of primary droplet from a nozzle with the diameter of 0.5 mm injected by a piezoelectric element were observed by a high-speed video camera. Injection velocity was changed from 0.32 to 4.76 m/s, where the apparent extensional rate ranged from 276 to 5,270. From the results, it was found that each filament length of each fluid increases monotonically as a function of the capillary, Ohnesorge and Weissenberg numbers and all data can be plotted in one curve independently of materials.

Each experiment and numerical simulation in fluid flow analysis has advantages and disadvantages. In the numerical simulation of non-Newtonian fluids such as a viscoelastic fluid, although detailed flow information can be obtained, the relationship between fluid additive concentration and the dimensionless number of viscoelastic parameters is not necessarily known. In order to estimate the actual stress and/or pressure fields affected by fluid elasticity, a promising method would be data assimilation, which is a simulation with successive corrections by measurement data. In this study, we have estimated the flow fields of a cylinder wake confined in a channel for a surfactant solution and a viscoelastic fluid based on Giesekus model, in the framework of data assimilation. The viscoelastic force given by the Giesekus model and the body force estimated by data assimilation reveals a good agreement in the high shear region.

The rheology of a suspension would vary with motion and dispersion of the suspended particles. In this study, 2-dimensional numerical simulation of a suspension flow with rigid elliptical particles in a channel was conducted. The governing equation of fluid was the regularized lattice Boltzmann equation, and in order to describe curved boundary on a Cartesian grid, the virtual flux method was applied. As a result, the effective viscosity varies in time because of the rotational motions of the particles. In the case of weak confinement (particles are relatively small compared to the channel width), spatial variation of the effective viscosity was more dominant than the temporal one.

Viscoelastic fluids have the characteristic of both viscosity and elasticity, and their physical characteristics are very complicated. As familiar examples of them, there are toothpaste, paint, mayonnaise, concrete, and etc. Various constitutive equations in the past decades have been proposed to describe such kind of fluids theoretically, and the proposed equations are aimed to be applied in the piping design in production plants. However, it is difficult to show the real flow behavior of viscoelastic fluid by numerical analysis, and many unsolved subjects are left behind to restraint their practical applications. To solve this problem, in this study, fundamental steady flow behavior characteristics of viscoelastic fluid at low Reynolds numbers is investigated by numerical analysis assuming Giesekus model and applying the viscosity with shear-thinning.

To evaluate material properties of highly viscous fluid is important subject in various kind of industries. Highly viscous fluid sometimes shows much complicated behaviors, and it makes difficult to evaluate properties such as viscosity. Some of them has rheological properties, and the behavior is affected not only by shear deformations but also by compressive or tensile deformations. The purpose of this research is to evaluate rheological properties of highly viscous fluid by separating stress components. In previous works, it was found that components of viscosity coefficients were evaluated independently. However, it was difficult to ignore effects of experimental device edge. In this research, advanced device and system were proposed. To exclude effects of the edge, experimental device design was converted from rectangular to cylindrical type. Therefore, analyzation procedures were also converted in a same manner. It was found that components of viscosity coefficients were evaluated more accurately.