There are many finned-tube banks in a Heat Recovery Steam Generator (HRSG). The development of finned-tube with the excellent heat transfer characteristic is demanded for decreasing the size of the HRSG. In this study, the influences of the flow rate and fin height on the local heat transfer coefficient were evaluated using the CFD analysis. The serrated finned tubes with the bare tube outside diameters of 38.1mm were used. As a result, the local heat transfer coefficients at the upstream side of each fin segment become larger with increasing the flow rate . Moreover, the distribution of the local heat transfer coefficients at the upstream side of each fin segment become more flat with increasing the fin height.

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We studied the effect of aspect ratio and contact angle on formation process of gas-liquid interface in a microchannel having hydrophobic cavity-shaped microstructures. The microstructures were fabricated on a test wall by wire electric discharge machining, and the test wall was coated with triazine thiol to induce hydrophobicity. We experimented with 5 different microstructures and 7 different concentrations of aqueous ethanol solutions in order to investigate the effect of the aspect ratio n/l_s and contact angle θ_ε. As a result, it was found that formation of gas-liquid interface was not observed in n/l_s < 1 and θ_ε < 50°. When n/l_s > 1 and θ_ε > 50°, formation of gas-liquid interface was observed. In this condition, the form of gas-liquid interface has changed on θ_ε = 70°.

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To investigate the synergistic drag-reducing effect of ribs and superhydrophobic surface, we perform direct numerical simulation (DNS) for a fully developed turbulent channel flow, in which the lower wall is superhydrophobic surface with ribs. In all computations presented here, a constant pressure gradient condition is employed, so that the positive drag reduction is evaluated as an increase of mass flux. For the case without ribs, the superhydrophobic property enhances the drag reducing effect, while for the case with ribs it reduces one.

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Skin-friction drag reduction effect by polymer additives in a turbulent channel flow is investigated by means of PIV and LIF measurements. We employed a fluorescently-labeled polymer in order to capture the polymer behavior in the flow. As a preliminary experiment, the fluorescently-labeled polymer is visualized in a rotating flow and compared with a dyed polymer. The fluorescently-labeled polymer shows to form thread-like structures for longer time than the dyed polymer. The PIV measurement of the turbulent channel flow with the dyed polymer shows the decrease of the Reynolds shear stress, which implies the skin-friction drag reduction.

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The prediction of the turbulent flow of a viscoelastic fluid is required for engineering applications. When the Reynolds stress model, is applied to a viscoelastic fluid flow accompanied by a frictional drag reduction of the wall turbulence, the model of an additional nonlinear term, Λ_<ij>, in the ensemble-averaged constitutive equation is an important issue. In the present model of Λ_<ij>, we recalibrated the values of the model parameters in order to adjust them to the adopted background Reynold stress model aiming at a better prediction of the mean velocity profile. Because the prediction accuracy of the mean velocity is improved by the present model, the Reynolds shear stress and conformation shear stress, which are directly related to the prediction accuracy of the mean velocity, were also confirmed to be well predicted. The optimal model parameter values were found to depend on either the Reynolds or Weissenberg number.

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It is known that turbulent frictional drag is reduced by adding polymer or surfactant into a turbulent flow. In the present study, the experimental analysis was performed in order to clarify temporal characteristics of turbulent fluctuation in surfactant solution flows. In various concentrations of surfactant solution, time series data of velocity fluctuations were measured by using a two-component LDV system at same Reynolds number. As a result of considering on temporal characteristics, it was found that the viscoelastic scale appears other than the scale of the turbulence vortex by adding the surfactant. The viscoelastic scale becomes longer as concentration levels increase and the turbulent vortex are disappeared obviously. Growing of the viscoelastic scale leads to the increase of frictional drag. It was also found that the small scale of turbulence vortex disappears near the wall region and buffer layer grows up.

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In this study, we conducted PIV measurements for a turbulent boundary layer with nonionic surfactant solution injection from wall surface at the momentum thickness Reynolds number up to 1500. The nonionic surfactant, AROMOX, which mainly consists of oleyldimethylamineoxide (ODMAO), was used. First, we compared mean velocity profiles from PIV measurements with those from LDV measurements for confirming the accuracy of the present PIV results. Then, we clarified turbulence structures in the maximum drag reduction region.

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A drag reducing flow was investigated for dilute cationic surfactant solutions in a rectangular channel. Laser sheet scattering due to micelles and shear induced structure (SIS) was observed for the channel cross section. If the Reynolds number was low, uniform scattering due to micelles was observed over the cross section. Increasing in the Reynolds number, the scattering became heterogeneous, and the dark sheet-like or thread-like SISs appeared on the cross section. The sheet-like SISs were observed upstream at a low Reynolds number. On the other hand, the thread-like SIS were observed downstream at a high Reynolds number. The dark SISs had gel-like elasticity, and the darkness was suggested to be due to their transparency.

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The purpose of this study is to experimentally reveal the effect of surfactant additives on the pressure loss of a microchannel with a height of 50 μm and on the Brownian motion of the nanoparticles in the vicinity of the wall surface. The tested surfactant solutions are a non-ionic surfactant, a cationic surfactant, and an anionic surfactant, and the density of the solutions is 1.0%. The Brownian motion is measured by an evanescent-wave microscopy system. As a result of the experiment, the pressure loss of the surfactant solutions increased compared to that of distilled water for 0.1 < Re < 9. In particular, the pressure loss of the non-ionic surface solution increased significantly. On the other hand, the zeta potential of the glass surface in the surfactant solutions was increased. Though the extent of the Brownian motion in the vertical direction was increased in the surfactants solutions, its extent in the horizontal direction was decreased compared to that in distilled water.

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We measured pressure drops and investigated flow properties of water and dilute aqueous polymer solutions of polyacrylamide (PAA) in capillary flows with bend section. Capillary sizes used as 125 μm and 410 μm. For PAA, dilute concentrations were used (in the range from 1 ppm to 100 ppm). For comparison, straight capillaries were investigated. Agreement between the water results and the predictions of laminar flow or Blasius expression was obtained, and pseudo-laminarization of PAA was suggested. Moreover, pressure drop increases were observed by bend section. However, pressure drop decreases were measured by using PAA. Thus, drag reduction for dilute polymer solutions was strongly suggested in capillary flows with bend section.

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The flow resistance of flat plates with hydrophilic gel wall in water tunnel were measured. A test hydrophilic gel was produced by using agar, which was prepared with concentration of 0.75, 1.0, and 3.0%. Experiments were performed in the range of flow velocity U of 0.04 < U < 0.3 m/s. Drag reduction was obtained for all values of the concentration. The maximum drag reduction was approximately 9.7%. Throughout the measurement range, the larger drag reduction was obtained with the smaller agar concentration. As the flow velocity increased, the drag reduction decreased.

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Some frictional drag reduction technologies were inspired from marine creatures. When dolphins swim at high-speed, we can see skin folds on its abdominal region. In this research, we use wavy plates with three different silicone rubbers as the models of different parts of dolphins' skins. We have conducted the experiments of open channel flow over there plates to measure the velocity field and total drag acting on the plates. The results show that the total drag and the pressure drag of the softest plate are lowest among the three plates and the deformation of the softest plate is the greatest.

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An experimental study is performed for channel flow over a backward-facing step with the burst wave induced plasma actuator (PA) as a flow control device adding a periodic disturbance. PA is installed on the corner edge of the step. The Reynolds number Re based on the mean velocity and the hydraulic diameter of inlet channel ranges from 2.0×10^3 to 5.5×10^3. The wall static pressure is measured, and the pressure improvement coefficient is evaluated. The velocity profiles around the step are measured using PIV system. The pressure improvement coefficient increases by the induced flow with PA. The effect becomes remarkable as the duty ratio increases. The reattachment length becomes shorter as the duty ratio increases. The reduction rate at burst frequency f_b = 100 Hz, duty ratio D = 75% and Re = 2.0×10^3 is larger than the continuous wave.

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In this study, AC DBD plasma actuator is applied to control the flow around NACA0015 and Ishii airfoils in a low Reynolds number condition (Re = 63,000). Here, the Ishii airfoil is a high performance airfoil at the low Reynolds number condition. The DBD plasma actuator is located at x/c = 5% and is actuated in burst mode with the nondimensional burst frequency F+ from 0.1 to 20. Maximum control authority is achieved with Vpp = 6kV and F+higher than 6 for both airfoils. Results show that different effect of separation control between NACA0015 airfoil and Ishii airfoil.

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The significant effects of dielectric barrier discharge (DBD) driven by repetitive nanosecond (NS) pulse voltage on lift enhancement on stalled airfoils have been demonstrated. The essential effect of NS plasma is considered as thermal effect. The detailed effect of the thermal excitation on the vortex structures is, however, not fully understood. In the present work, a simple momentum model for incompressible Unsteady Reynolds-Averaged Navier-Stokes simulation was proposed, in which the effect of plasma was implemented as a wall velocity boundary condition on the airfoil. Although this simplified simulation does not take account of thermalization process and shock dynamics, the results showed discrete vortices generated by rolling-up shear layer over the leading edge. It qualitatively consisted with the trend of time-averaged pressure distribution obtained by the corresponding experiment.

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Flow control effects of string-type dielectric barrier discharge plasma actuators (DBD-PAs) on flat plate and NACA0015 airfoil were experimentally investigated. For the displacement (δs) between metallic wire coated with insulative resin and exposed electrode less than 1 mm, flow speed is enlarged according to increase of δs and velocity vectors are distributed uniformly in comparison with that for δs > 1 mm. Active control of flow separation on a NACA0015 airfoil was carried out by embedding the metallic wire with δs = 1 mm at x/c = 0.05. C_L and C_D are improved for Re = 3.3×10^4 by inducing jets by the string-type DBD-PAs under continuous injection and pulse modulation as with conventional DBD-PAs.

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Noise suppression is of importance for jet engines, and acoustic panels are set in the fan duct in order to reduce the noise emission from the fan component. However, it is apparent that duct loss increases due to the acoustic panels because of the rough surface. Therefore, we have to develop a new acoustic panel that can realize large noise suppression and low duct loss. There have been a few numerical studies on the fan duct with acoustic panels, since Mach numbers in the main stream and inside the panel cavity are largely different and thus ordinary CFD solver for a compressible flow cannot be adopted. In the present study, we employed an all speed Roe scheme to reproduce the flow field with large Mach number difference. Visualizing the numerical results, we investigated the flow field around the acoustic panel hole, the duct loss, and the influence of the number of panel holes.

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This paper deals with the aerodynamic characteristics of the concentrated photovoltaic system (i.e. CPV) of three-divided-panel type. A preceding experimental study indicates that the moment around the shaft supporting the panel decreases when the acceptance surface of the panel faces downstream ('downstream case'). To investigate the mechanism, we conducted measurements on the aerodynamic forces in a wind tunnel. It is found that as the slit width increases, the moment gradually decreases to small values when the acceptance surface faces downstream. This reduction probably comes from uniformity of the pressure distribution on the rear surface for the downstream case.

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A series of large-eddy simulations of the spatially developing turbulent boundary layer with uniform blowing or suction at moderate Reynolds number, based on the free-stream velocity and the momentum thickness, up to Re_θ = 2500 are performed. Similarly to the previous work of the direct numerical simulation at low Reynolds number [Kametani & Fukagata, J. Fluid Mech., vol. 681, pp. 154-172, 2011], uniform blowing achieves the skin friction drag reduction and enhancement of the turbulence, while uniform suction has the opposite trends. In spite of blowing at 0.1% of free-stream velocity, around 18% of drag reduction is achieved. The root-mean-squares of turbulent uctuations and the spectral analysis show that blowing/suction affect the turbulence at the outer region notably. The distributions of the power-spectral density of streamwise velocity uctuation and the cross-spectra of the Reynolds shear stress are strongly distorted in the outer region. The decomposition of the skin friction drag indicates that blowing has potential to reduce skin friction drag despite it increases the turbulence even at moderate Reynolds numbers.

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Experimental investigation for a periodically converging-diverging turbulent pipe flow is performed to examine drag reduction effect with LDV (Laser Doppler Velocimetry) and differential pressure experiment. A shape of the pipe is designed according to a result of a direct numerical simulation. Three periods of the converging-diverging are provided. At the bulk Reynolds number of 4000, maximum drag reduction rate is obtained: the drag reduction rates are 8%, 12% and 14 at the first, second and third period, respectively. Therefore, the drag reduction rate is found to develop in the downstream direction. According to LDV, the mean streamwise velocity and the RMS value of streamwise velocity show a similar tendency with the result obtained by the direct numerical simulation.

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It is known that the drag reduction is obtained from turbulent channel flow with spanwise traveling wavy wall. In this study, we conducted the DNS of turbulent channel flow with spanwise traveling wavy wall and investigated the relation between the drag reduction ratio and the wavy wall parameters such as wavelength, wave amplitude, and phase speed.

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Mixing/diffusion enhancement is one of the key technologies in various aspects, and is needed in chemical reactors, heat exchangers, burners/combustors, air conditioners and so on. Jets are known to be useful for such mixing/diffusion enhancement. We research the jet from an asymmetrical two-dimensional nozzle, especially concerning the effect of the lip length of the nozzle. Experiments are conducted at a Reynolds number of 1000 and 6000. The aspect ratio of the nozzle exit is fixed to 300. And, the lip length is 0, 2.0h, 3.3h, 4.0h, 5.0h, 6.0h, 7.3h, 8.0h and 10h, where h denotes the height of the nozzle exit. We show mean-velocity and turbulence-intensity profiles at various downstream sections, in order to reveal fundamental characteristics of the jet. Furthermore, in the near downstream, we visualize the flow by olive oil smoke or ethylene glycol smoke so as to get quantitative information using a PIV technique, and perform the dominant-frequency measurements to reveal flow-instability characteristics.

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The assessment of a numerical method for vortex method has been performed in the flow caused by an impulsively starting circular cylinder and the flow around a moving at plate, which represents the fundamental model of flapping flight. The temporal development of the drag force of the cylinder agreed well with the reference data, whereby the consistency and converging behavior of the scheme were confirmed as well. The force exerted on the plate was found to be plausible, in terms of the force time developments for different Reynolds number, despite some scattering in the data.

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In this study, unsteady aerodynamical effects of 2-D airfoil (NACA0012) at the attack of angle 7deg under acceleration or deceleration condition was numerically investigated using a grid-free vortex method. The aerodynamical forces and vortical flow field were compared with each accelerated or decelerated condition at Re=4.0×10^5. In this analysis, firstly, airfoil was moved at a constant speed, and then, each acceleration or deceleration condition was given to the airfoil from the non-dimensionless time T* = 7.5 at which the fluctuation of fluid forces became stable. The result showed that the aerodynamical forces changed compared with the steady condition. In addition, pressure distribution affected by the change of the vortex structure on the airfoil appeared.

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In this study, DNS of flow around a stationary sphere under the isothermal conditions with the high Mach numbers and low Reynolds numbers flow were conducted by solving three-dimensional compressible Navier-Stokes equations for investigation of the influence of the Mach number and temperature ratio on the vortex structures. From calculation result, we clarified the following facts that the Mach number and temperature ratio effect on the wake of the sphere: (1 the vortex shedding is decreases in the case of high Mach number or high temperature ratio, (2 the sphere releases strong vortex in the case of high Mach number or low temperature ratio and (3 turbulent kinetic energy at the wake of the sphere increases in the case of high Mach number or low temperature ratio.

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Two-dimensional numerical simulation is carried out to investigate the leading edge receptivity of a at-plate boundary layer. It is shown that velocity fluctuations inside the boundary layer at an elliptic leading edge is suppressed by changing the local viscosity limited to velocity fluctuations. The amplitude of the velocity fluctuation in the boundary layer increases rapidly right after the junction between the elliptic leading edge and the at plate, which also depends on the frequency of the vortical disturbances given upstream.

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Vortex structures in the wake behind three-dimensional bluff bodies cause various problems such as vibration, drag and sound noise. We dealt with a circular disk wake, as a representative of three-dimensional bluff body wake in order to understand the fundamental characteristics of vortical structures. The purpose of this study is to extract vortex structure in the wake behind the circular disk by Particle Image Velocimetry processing. Instantaneous velocity and vorticity distributions showed a meandering motion of the wake in a section parallel to main flow. Also, time-averaged vorticity distributions presented hairpin vortices in sections normal to main flow.

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In this research, the flow characteristic from two circular cylinders which are oscillating by the different mode of vibration was investigated by numerical simulation at the Reynolds number Re = 500, with varied the distance ratio L/d and the amplitude ratio 2a/d. As a result of the numerical experiments, the flow aspect and change of fluid force which become complicated were shown. In the A-mode oscillation cylinder and the S-mode oscillation cylinder, it was found that the A-mode oscillation cylinder tends to receive mutual interference. In the case of such a complex state, it became clear to completely differ from the result obtained when the aspect and fluid force of the flow are single.

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The effects of nozzle geometry on the acoustic waves from Mach 1.9 supersonic jet are experimentally investigated. PIV and microphone measurements are conducted to analyze the relationship between flows and acoustic waves. In this study, three different nozzles of conical nozzle, convergent-divergent nozzle (C-D) nozzle, and tab C-D nozzle in which tab is attached in nozzle inlet to generate disturbance are considered. Three noise sources are identified. Conical nozzle case shows screech and broad band shock noise spectra because of the existence of strong shock train in flow. For the other two cases (C-D nozzle and tab nozzle), there are not clear shock associated noise spectra due to nearly ideally expanded condition by the nozzle geometries so that turbulent mixing noise should be dominant. Tab nozzle case shows higher frequency acoustic spectra than that of C-D case. This is because inflow become turbulent flow from the very beginning by the existence of tab so that smaller scale turbulence is generated.

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In this study, a direct numerical simulation is carried out for the flow that the particle passes a shock wave to investigate interference between the particles and shock wave. The flow simulation based on three-dimensional compressible Navier-Stokes equations is conducted by Cartesian mesh method with immersed boundary method to deal with multiple moving boundaries by Euler-Euler approach. This flow solver is developed for the purpose of accurate prediction of the acoustic field around a rocket launch site. The objective of this study is to investigate a flow containing shock waves and moving multiple particles. The shock Mach numbers are 1.2, 1.5, 2.0, and 2.5. When multiple particles pass the shock wave, characteristic vortex structure is formed in the wake. The vortex structure may be a key factor of the interference.

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A mechanism for transonic tones generated in an over-expanded two-dimensional nozzle is studied experimentally using a high-speed video camera. Transonic tones in low nozzle pressure-ratios are distinguished from screech tones in high nozzle pressure-ratios and have characteristic peak acoustic frequencies. A series of successive images captures a large shock oscillation inside the nozzle, which takes place between the throat and the nozzle exit. Shock-induced separation is observed and the separated shear layer reattaches to the nozzle wall. A separation bubble-induced vortex sheds when a shock wave reaches the nozzle exit. Then, a generation of pressure waves from the nozzle exit, meaning transonic tones, is found from schlieren images. We deduce that vortex shedding or a shock wave at the nozzle exit is a key factor of a generating mechanism for transonic tones.

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The three-dimensional time dependent compressible Navier-Stokes equations are numerically solved to study development of a pair of third helical modes in a supersonic round jet at high convective Mach number (M=2.0) using high-order compact upwind schemes. Numerical results show that staggered structures of positive radial velocities are generated between the regions which lambda-shape vortices are closed in the supersonic jet. Therefore, the early developments of the lambda-shape vortices are affect rapid jet shear layer expansion. Moreover, the viscosity effect on the growth of the pair of third helical modes becomes significant as Reynolds number is less than 3000.

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Navier-Stokes analysis code was developed for the comprehension of the shock modulation phenomena due to the interaction between the shock wave and the temperature modulated field. The shock wave modulation was qualitatively suggested which was also reported from the experiment.

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The convective Mach number and density ratio dependences of sound sources and flow structures in a compressible mixing layer are investigated by direct numerical simulations. Characteristics of sound sources are analyzed using the source terms of Lighthill equation. As the Mach number increases sound source strength decreases, because vortex motion is weakened by compressibility. For density ratio dependence, the emission angle of Mach waves becomes shallower and vortices show sparse structures as density ratio increases. In addition, larger vortex structures appear at lower density side for higher density case.

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Speedup of the DSMC calculation has been investigated by the parallel processing using a CPU with multiple cores or threads and using the intermolecular collision scheme U-system which enables coarse cell networks for calculations near atmospheric pressure condition. According to my recent analysis, it has been demonstrated that physical properties in each cell of the U-system alter in accordance with a location within the cell. The underexpanded jet through an orifice, upstream stagnation pressure 101300 Pa and pressure ratio 50, 10, 7 or 4, is calculated by Bird's collision scheme and by the U-system. An effect of the upstream calculation region of the orifice is also examined.

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The aerodynamic force enhancement effect occurs by applying magnetic field around a reentry vehicle in a weekly-ionized flow behind the strong detached shock wave. Recently, this force enhancement effect was experimentally investigated using an expansion tube which can produce high speed and high enthalpy flow. Because aerodynamic force measurement is difficult due to short test flow period in expansion tube, drag measurement system which employed a piezofilm with fast responsiveness was developed in this study. This drag measurement system was calibrated using CO2 pulse laser and applied to experimental investigation on the aerodynamic force enhancement effect in expansion tube. The aerodynamic force acting on simple models in the flow produced by the expansion tube can be measured in this system. Additionally, the increase of the drag force due to magnetization in a weekly-ionized flow was observed.

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The effect of the initial pressure ratio on the piston trajectory of the gun-tunnel was numerically investigated. By lowering the initial pressure ratio, the critical piston mass which is defined to begin to deviate from the maximum piston distance predicted from the ultimate light-mass-piston theory becomes lighter.

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Preliminary test results were reported about the free-piston driven expansion tube facility in JAXA Kakuda. The facility originally built as the free-piston shock tunnel HEK was modified to the expansion tube HEK-X. Over-all length of the facility was 37m and expansion tube diameter was 72mm, in which test models up to 40mm diameter can be used. The facility was designed to produce 14km/s hypervelocity free-stream (stagnation enthalpy 100MJ/kg). In the present shakedown test campaign, shock speed of 8.5km/s (stagnation enthalpy 70MJ/kg) in expansion tube was successfully obtained. Free-stream Pitot pressure at the exit of expansion tube was also measured.

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This study is a numerical analysis considering the transport phenomena (i.e. diffusion, viscosity and heat conduction) on the detonation propagating in the rectangular tube. The purpose of this study is to evaluate effects between the crosssectional shape of the tube and transport phenomena. The numerical calculation for Navier-Stokes equation has been approximated by the finite difference method which is composed of the semi-implicit MacCormack TVD scheme, considering a stoichiometric gas mixture of hydrogen and oxygen. In the tube cross section of the aspect ratio 1.25, the propagation behavior of detonation has been shown. In addition, some behaviors of pressure, temperature and density of HO_2 have been clarified.

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Snow properties are influenced by climate or region. For the efficient development of a snowblower, stable and quantitative performance evaluation method is required. In this study, we developed snow property model and tried to reproduce the snow removal work using Discrete Element Method (DEM). We developed snow compaction model and air drag model to consider the properties of actual snow. And we have improved the snow property model for fallen snow simulation. The obtained computational results were compared with the experimental results, and found that both results exhibit reasonable agreements. Therefore, we have succeeded in the computational reproduction of quantitative snow behavior in a snowblower using new snow property model.

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In recent years, the utilization of computational fluid dynamics (CFD) in various industrial fields has broadened following developments in computer technology. Although mainstream CFD is currently based on a grid method in an Eulerian framework, it is difficult to apply this to the simulation of problems in which large deformations of interfaces between phases occur. For this reason, particle methods are now receiving attention. In this study, we developed a numerical method to couple the particle and grid methods in order to simulate a gas-liquid two-phase flow. We conducted numerical tests on present numerical method with an impingement-jet to the liquid surface and the results show reasonable agreement with the experimental data. Thus, we confirmed that our numerical method can reproduce gas-liquid two-phase flow including interactions between different phases without being affected by the numerical diffusion and instabilities.

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The innovative characteristics of the cryogenic single-component micro-nano solid nitrogen (SN_2) particle production using super adiabatic Laval nozzle and its application to the ultra-high heat flux cooling process are investigated by a new type of integrated measurement coupled computational technique. Furthermore, cooling characteristics and impingement behavior of cryogenic micro-solid nitrogen (SN_2) particles in relation to a heated wafer substrate were investigated for application to next generation cooling technology. It is especially found that high-speed ultra-fine SN_2 particle is continuously generated due to the freezing of liquid nitrogen (LN_2) droplet induced by rapid adiabatic expansion of subsonic subcooled two-phase subcooled nitrogen flow passing through the Laval nozzle.

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Icing phenomenon occurs where super-cooled water droplets impinge and accrete on a body due to heat transfer under rime or graze ice conditions. In the graze ice condition, water film on ice surface is moved by gravity, shear stress, pressure gradient and so on. Recently, the water movement on the ice surface is computed accurately and its effect is clarified. In the present study, we use the CFD code named as UPACS (Unified Platform for Aerospace Computational Simulation, JAXA). We employ the water flow model proposed by Myers (Phy. Fluids, 14 (2002), pp.240-256). Results show a reasonable agreement with experimental data in the case of NACA 0012. It is confirmed that the water flow model reproduces the icing phenomena accurately as compared with the other model (i.e. one grid point moving method).

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Recently, various terrorisms come about and threaten people in the world. Because of the high fatality rate, biological and chemical weapons are recognized as the most dangerous weapons in all other ways of terror. For these reasons, research and development of measures for decontaminations are emergent and key issues on a world scale. However, the experiments are highly risky and legally prohibited in many cases. Therefore, computational fluid dynamics (CFD) is useful to research and develop the decontamination methods. In order to simulate decontaminations, it is necessary to know chemical agent (CA) behaviors. In the present study, we propose the three-dimensional volatilization model which can estimate the volatilization from a contaminated substrate by using CFD. The model predictions give good agreements with the experimental data.

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Megasonic cleaning, which uses higher frequency wave at and above 1 MHz, have been studies for efficient cleaning without pattern damage in semiconductor industry. To clarify multi bubble dynamics in megasonic field, in the present study, numerical simulations of two and three oscillating bubble near wall boundary in megasonic field are performed using a compressible locally homogeneous model of a gas-liquid two-phase model. In the calculation of two bubbles with the initial radii of 2.0 μm, the oscillating amplitudes of the bubbles grow, the bubbles approach, coalesce, and induce the higher pressure. It is found that in the cases of two bubbles, the induced pressures in the case of R_0 &ge; 2.2 μm are smaller than these in the case of single bubble and these in the case of R_0 &le; 2:0 μm are larger than these in the case of single bubble.

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Recently, nano-particle deposition attracts much attention in a wide variety of engineering fields. Nano-particle technology has various utilities, while the nano-particle deposition often exerts a bad influence. In the present study, we made a numerical simulation of a duct flow and observe the nano-particle deposition phenomenon on a flat plate mounted on the bottom wall. The Euler-Lagrange coupling method is employed to reproduce interaction between the particle deposition and the flow field. An isothermal condition is imposed on the bottom and top surfaces of the channel and the flat plate surfaces in order to investigate the thermophoresis effect,. It is indicated that the nano-particle trajectory is drastically affected by the thermophoresis. The deposit layer is formed at the high temperature gradient region. The wake region behind the flat plate creates also a thick deposition layer. Therefore, it is confirmed that the nano-particle deposition is strongly controlled by the flow and thermal fields.

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Particle image velocimetry (PIV) has become a powerful tool for flow velocity measurements in wind tunnel testing. However, it is difficult to apply the PIV technique to supersonic flows because of unreliable particle traceability. In the present study, in order to evaluate the particle traceability, PIV and molecular tagging velocimetry (MTV) are applied to underexpanded jets, in which the gas rapidly accelerates and decelerates. Particle drag coefficients are also estimated from the velocity data measured by the two velocimetries for the particle Reynolds numbers lower than 〜4 and the relative Mach numbers ranging between 〜0.2 and 〜1. The results demonstrate that the estimated drag coefficients are reproduced reasonably well by the Stokes drag law although the compressible and rarefaction effects have been expected to appear for the present Reynolds and Mach numbers.

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Thermal transpiration (thermal creep) flow, which is induced only by temperature gradient along a channel, is one of the most interesting phenomena in micro gas flows. The thermal transpiration flow has been studied both numerically and experimentally; however, the detailed condition inside a channel has not been enough studied experimentally, and it makes difficult to compare numerical and experimental results directly. In this study, the pressure distribution on a micro channel surface in thermal transpiration flow was measured by means of the Pressure-Sensitive Paint (PSP) technique. And the pressure distribution was a convex profile along the channel.

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This paper describes the visualization for unsteady fluid phenomena occurring on shock-tube wall by means of Temperature-Sensitive-Paints (TSP). TSP measurement used in this research has been developed for heat-flux estimation in hypersonic shock tunnels which have a few milliseconds test duration, thus TSP has to measure temperature in a few hundred kHz of sampling frequency for highly-accurate heat-flux estimation. Results measured by TSP show a detailed flow structure on the wall, where temperature/heat-flux variations by the incident/reflected shocks, the laminar to turbulent boundary-layer transition, the streak in turbulent boundary-layer, the shock/boundary-layer interaction and the interference between the reflected shock and the contact surface, are clearly visualized and accurately quantified.

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In this study, we conducted preliminary experiments to visualize unsteady pressure field caused by shock waves from free-flight projectiles which is launched by ballistic range. For this purpose, we visualized shock-wave propagation on sample plate by using ultrafast-response PSP and high-sensitivity high-speed video camera. Visualization results were well agreement qualitatively compared with past results.

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