Distribution of blade load is one of the design parameter for cavitating inducer. For experimental investigation of thermodynamic effect on blade load, we conducted experiments in both water and liquid nitrogen. Pressure rising along the tip was measured. It was found that the shift of blade load to the trailing edge occurs at the lower cavitation numbers with increase of cavity length. However, the distribution of blade load can be indicated by the cavity length independent of thermodynamic effect.

抄録全体を表示

We investigate the dynamic response of cavitating flow field to the flow rate vibration in two-dimension cascade. As a result, under non-cavitation condition, the pressure and lift coefficients are oscillating with sine curve, as well as the flow rate vibration. Under the cavitation condition, the pressure and lift coefficients can not be simply expressed by the sinusoidal oscillation with a single frequency. This is caused by the combination of the inertia and the cavitation effects.

抄録全体を表示

In a liquid rocket engine, cavitations around the inducer of the turbopump sometimes cause the instability phenomena when the inlet pressure decreases. The cavitation surge, one of the instability phenomena, has been discussed mainly "the inertia model". A data of the surge mode oscillation on a experimental turbopump in JAXA showed that its frequency was not changed continuously related to the decrease of inlet pressure, but changed disconnectedly. In this article, aiming at explaining this phenomena, an one-dimensional analysis is examined applying "an acoustic model" combined the inlet line with the sonic velocity of liquid oxygen.

抄録全体を表示

In plant systems including high-pressure-ratio multi-stage axial compressors or gas turbines, transient flow phenomena and their influences on the system components caused by possible compressor surge should be critically examined. In the situation, the compressor internal working conditions, caused by stage stalling and affected by the transient flow-path conditions, will also give serious effects on the phenomena ; the fact has often been be neglected in the conventional analyses. This paper describes a practical method of compressor surge simulation over the transient behaviors both of the entire flow-path and the internal stages, in particular the latter on the basis of one-dimensional stage modeling and application of fundamental equations of mass, motion and energy.

抄録全体を表示

The effects of the tip clearance on the rotating stall inception in an axial flow compressor rotor have been investigated by an EFD/CFD hybrid analysis. It has been found that the tip clearance plays an important role in the rotating stall inception. In the compressor with small tip clearance, the concentration of low energy fluid on the blade suction surface and the leading edge separation at the blade tip crucially influence the rotating stall inception. On the other hand, in the one with large tip clearance, tip leakage vortices are dominant in the flow field and their breakdown causes the rotating instability.

抄録全体を表示

A floating type Backward-Bent Duct Buoy (BBDB) is a wave energy conversion device with an Oscillating Water Column (OWC) at the front side. The device captures the wave energy using the heaving, the pitching, the surging motion of BBDB and the heaving motion of OWC, and generates the reverse time-mean drift force reducing the mooring loads over specific frequency ranges. Investigations are carried out to find more reasonable devices than the traditional OWC type floating device. An eigenfunction expansion method is introduced for analyzing the BBDB with OWC. It is confirmed that these solutions give good agreement with several experimental results in this paper. It is shown in a design method how to make BBDB match the turbine characteristics.

抄録全体を表示

A ducted Darrieus-type turbine has been proposed for extra-low head hydropower utilization of total head less than 2m. Though the hydro turbine system, in general, might consist of an intake, runner section and the draft tube for higher efficiency operation, it was clarified in previous experiment that there was no need of the side-walls of runner section and a draft-tube for keeping the performance high, in the case of duct with an inlet nozzle, which yields a simplification of the structure of the turbine system. In order to reconfirm this result for large-sized turbine with 500×300mm duct, instead of small-sized one with 400×200mm, the side-wall effect on turbine performance was experimentally investigated for three- or four-bladed runner. In the present paper, the experimental results are shown with considering flow behaviors in the runner section.

抄録全体を表示

The aim of this investigation was to improve power performance of Savonius hydraulic turbine utilizing small stream for electric generation. An attempt was made to increase the power coefficient of runner by use of a flat shield plate placed upstream of the runner. It was clarified the relationship between setting condition of the runner with the shield plate and power performance by experimentally. As a result the best installation condition of the runner with shield plate was revealed, and then the maximum power coefficient of runner is achieved for 47%. In addition we considered effect of the shield plate and influence of installation condition on the runner performance with the shield plate by flow visualization around the runner.

抄録全体を表示

This report includes an experiment on the Savonius rotor having sub fins or sharp cornered bend blades and the empirical formula of effect of the sub fin or cornered bend. By adding fin or cornering blade, it is considered that the coefficients of fluid forces and the tip speed ratio in the smaller phase angle region of the blade will be increased to develop the frontal substantial area to the wind. In the experimental results, the maximum output power coefficient was increased about 12 percent and the tip speed ratio of the rotor also became somewhat larger in comparison with that of the normal rotor.

抄録全体を表示

This paper investigates application of CFD and Brooks' model to noise prediction of wind turbine. We calculate flow around NACA0012 using LES and predict aerodynamic noise by FWH. Also we predict the noise using Brooks' model and compare them with experiment. As a result, model prediction is good agreement with experiment. But it probably difficult to predict aerodynamic noise of airfoil of wind turbine properly, if flow has large eddy structure.

抄録全体を表示

The rotor torque of straight-blade vertical axis wind turbines fluctuates periodically, because the relative wind velocity experienced by the blade varies with the azimuth angle of the rotor. The objective of this study is to clarify the torque fluctuation on blades of vertical axis wind turbines. The wind tunnel experiment was performed with actual size vertical axis wind turbine and the torque fluctuation was observed by using strain gages. In addition, the torque fluctuation was analyzed by CFD. This paper describes the comparison between the experimental results and the numerical results. And the relation between wind turbine design conditions and the torque fluctuation is clarified.

抄録全体を表示

By using oscillating wind generated by an unsteady wind tunnel, response of rotational speed of a small vertical axis wind turbine, the moment of inertia of which is variable by attaching some weights to the axis, has been investigated varying the wind cycle as a parameter. The results showed that ratio of the time delay in rotational speed to the wind cycle hardly depends on the moment of inertia and that ratio, which is divided by the wind cycle, of the rotational speed width to the average rotational speed can be approximated by a curve of inverse proportion and that energy efficiency hardly has dependence on both the moment of inertia and the wind cycle.

抄録全体を表示

Some wind collectors for the Darrieus-type wind turbine were tried numerically by 3-D LES(Large Eddy Simulation) analysis. The aim of this study is improvement of power coefficient. The main parameters of wind collector are curvature of foil and its width. Another important parameter is foil setting angle. The rotor is constructed by 3 or 2 blades (chord length are 15% of diameter). The equations are discretized by Finite volume method for space and Fractional step method for time. As a result of analysis, The best setting position was the 25degree upwind the axis. The wind collector was effective to 2 blades rotor than 3blades rotor, its maximum power coefficient was 0.452.

抄録全体を表示

The objective of this study is to show the effect of guide vane solidity on the performance of straight-bladed vertical axis wind turbine with a directed guide vane row. The experimental study was carried out by a wind tunnel. The wind tunnel with a diameter of 1.8 m is open jet type. The rotor has 3 straight blades with a profile of NACA4518, a chord length of 100mm, a diameter of 600mm and a blade height of 700mm. The guide vane consists of some arc plates. The wind velocity is constant at 8m/s. As a result, it has been concluded that the turbine performance depends on the guide vane solidity.

抄録全体を表示

The objective of this study is to show the effect of inner guide vane on the performance of straight-bladed vertical axis wind turbine. The experimental study was carried out by a wind tunnel. The wind tunnel with an exit of a square of 500mm is open jet type. The rotor has 5 straight blades with a profile of NACA0018, a chord length of 50mm, a diameter of 200mm and a blade height of 200mm. The guide vane consists of arc plate. The wind velocity is constant at 10m/s. As a result, it has been concluded that the inner guide vane is slightly effective in improving the turbine performance.

抄録全体を表示

A prototype 3kW horizontal upwind type wind turbine generator of 4m in diameter has been designed and examined under real wind conditions. Usually the machine is controlled at several stages depending on both the measured rotational speed and the calculated wind speed. Two control methods have been applied: the variable pitch angle, and regulation of the generator field current. To improve the control program on a high wind speed stage, the pitch angle controller adopted a LQG (Linear Quadratic Gaussian) control method. This paper describes the LQG controller and shows a numerical simulation result. The control program varied the pitch angle and maintained a optimum rotational speed to prevent over rotation past 400 rpm.

抄録全体を表示

It is important to reduce the change of the output of wind turbine to spread wind power generation more. Then, we aimed to look for the method of a better control of wind turbine to reduce the change of the output. Concretely, we examined the change in the aerodynamic characteristic of the wind turbine when the pitch angle and the rotational speed were changed by the numerical analysis. The acceleration potential method was used for the numerical analysis. As a result, when the pitch angle or rotational speed is changed linearly, it has been understood that the torque decreases greatly at once afterwards and then gradually approaches a regular value. In addition, damping time and the magnitude of the overshoot at that time is large like time when the velocity of the wind is low.

抄録全体を表示

For the improvement of rotor performance of the micro horizontal axis wind turbines (HAWT), the coning angle has been introduced to the turbine rotor blade in the downstream direction. It can move the shedding position of the tip vortices away from the principal parts of blade, which decreases the axial induced velocity, leading to the increase of incoming velocity to the rotor. A series of experiments conducted by using model rotors installed on the top of the building shows that the power coefficient of the micro-HAWT with coning angle is smaller than that of the original-HAWT without coning angle, especially in low Reynolds number conditions. The effects of coning angle and Reynolds number are discussed in the present paper, focusing on the flow around the rotor blades.

抄録全体を表示

The authors invented the unique wind power unit composed of the large-sized front wind rotor, the small-sized rear wind rotor and the peculiar generator with the inner and the outer armatures. The rotational torques of both armatures/wind rotors are counter-balanced, while the rotational speeds and the directions are adjusted automatically in response to the wind conditions. The prototype unit is composed of the tandem wind rotors, whose front and rear diameters are 2 m and 1.33 m, and the double rotational armatures type synchronous generator. The unit was setup at the roof of an isolated building at Kitakyushu city in Japan. The field test results proved that this type unit may be effective to get the sufficient output if the profiles of the wind rotors and the peculiar generator are optimized.

抄録全体を表示

A quasi-three-dimensional aerodynamics design method for the wind turbine with brimmed diffuser has been developed. The design method is based on two-dimensional blade data and an axisymmetric meridional flow analysis. In the meridional flow analysis the axisymmetric flow is computed on a meridional plane, including the viscous forces and the aerodynamic blade loading modeled by the blade forces, in order to take the spanwise distribution of the inlet flow into account. The flow fields in the wind turbine designed by the present method have been investigated by three-dimensional Reynolds-averaged Navier-Stokes (RANS) simulations. It is shown that the performance of the wind turbine depends on the blade loading.

抄録全体を表示

This paper shows the results of analysis for NEDO guideline measurement data to develop the wind condition model in complex terrain. NEDO guideline measurement has been performed in seven different sites to obtain the wind characteristics in complex terrain such as mountainous area in Japan. Parameters of normal turbulence model (NTM) described in the IEC 61400-1 are compared and evaluated using the guideline data.

抄録全体を表示

Wind tunnel experiments of street canyon were conducted in a uniform flow. A heated street was located between an upstream and a downstream buildings. The effects of street width and flow structure on cooling effect of the street surface were investigated experimentally. A circulation flow just behind the upstream building contributed the uniform of temperature difference on the street surface. The cooling effects of a separated flow from the upstream building around reattached point were confirmed experimentally. In the near future, street canyon phenomena elucidate also in a large turbulent shear flow by a Makita-type active turbulence generator by our research group.

抄録全体を表示

Large-eddy simulation was conducted to investigate mechanism of gas exchange in and above a two-dimensional canopy layer. A tracer gas was released as a ground-level continuous gas line source at the center between blocks. The results show that a low-momentum region (LMR), defined as a region in the flow where instantaneous streamwise velocity is lower than the local mean velocity, was appeared as a turbulent organized structure above the canopy layer. The LMR has strongly influence on removal of gas from the street canyon to the free surface.

抄録全体を表示

The effects of rain on CO_2 transfer across the wavy-sheared air-water interface were investigated through reaeration experiments of CO_2 in a wind-wave tank with a rain generator. The CO_2 transfer coefficient on the liquid-side k_L was measured by applying the mass-balance method. The results show that CO_2 transfer across wavy-sheared air-water interface was promoted by rain. The measured values were not in good agreement with the empirical formula proposed in previous paper, since the impinging velocity of raindrops was not considered in the literature.

抄録全体を表示

In this study, in order to investigate the characteristics of natural wind for the purpose of the application to improvement in small wind turbines, triangle-like wind speed patterns have been detected from the wind data measured by a propeller-type anemometer. As a result, we observed that a Λ-type pattern tends to have the peak at one-third from the beginning and a V-type pattern tends to have the peak at one-third from the end.

抄録全体を表示

We tried to generate a gust front in a multi-fan type wind tunnel in order to clarify the detailed structure of a gust front. Velocity fluctuations after the passage of the gust front were investigated. The conditioning measurements of velocity fluctuations were also made with two X-wire probes. Fully developed turbulent flow was observed in the upper layer of the gust. A periodic pattern like K-H instability wave was embedded in the turbulent fluctuation near Z=200mm. On the other hand, only turbulent motion was observed near ground. Though the strong gust was found to correspond to sweep motion, it does not exist only in the lower shear layer but correlate with large scale turbulent motion across over the whole layer of the gust.

抄録全体を表示

Traveling microbursts were experimentally simulated by salt water dropping from a tank settled in water flow. The density dependence of its property was investigated. The flow pattern of the traveling microburst was filmed with a hi-speed camera and the velocity field was measured with a dynamic PIV method. The maximum horizontal velocity of the traveling microburst at the windward side depended on the density of the salt water whereas that at the leeward side did not depend of the density well. Such density dependence was not described through the scaling law for the stationary microburst.

抄録全体を表示

Effects of the wave mode on turbulence generation were experimentally investigated in a strongly stably-stratified flow. Turbulence generation in the collapse process of the waves was clarified through implementing the analyses of the kinetic energy and the potential energy derived from the instantaneous temperature gradients determined by the vertically arranged multi-point sensors. The frequency range of the vertical heat flux against the local temperature gradient was expanded from the low-frequency region toward the higher frequency region through the energy cascade process induced by the non-linear wave-wave interactions. Counter-gradient heat flux was produced with the potential energy exceeding the kinetic energy around the wave-crest. The random components of velocity fluctuations were produced accompanied with the counter-gradient heat flux due to the production of the potential energy of the harmonics through the non-linear effects of the waves.

抄録全体を表示

Various meteorological phenomena are introduced at the viewpoint of fluid dynamicists. Many phenomena having a similar structure compose hierarchy at various scales. The concept of coherent structure is expected to describe such meteorological phenomena. The highly advanced experimental and numerical knowhow of fluid dynamicists having grinded in the field of mechanical engineering will be usuful for solving many problem on meteorology.

抄録全体を表示

In order to obtain effective viscosity in bubbly liquid, which changes with transient bubble deformation, spatio-temporal velocity distributions of transient shear flows in a rotating cylinder is measured by using Ultrasonic Velocity Profiling (UVP) synchronizing of bubble deformation measurement. For Silicone oil of 1000 cSt as a test liquid, velocity distribution during spinning up has been found to be different from the liquid without bubbles. We have compared the circumferential acceleration of liquid with time serial images of bubble deformation to reach the conclusion that the maximal stretched bubbles the strongest drive the shear flow contrastively to the conventional equilibrium deformation theory of effective viscosity.

抄録全体を表示

Bubble nucleation and growth processes in high-viscosity fluid during rapid decompression have an important role in volcanic eruption. In the present study, the rapid decompression experiments with one-phase fluid of silicone oil are conducted to investigate the influence of volatile substance on bubble nucleation. Bubble number density is measured from the observed images and compared with the previous study which has been experimented with two-phase fluid of silicone oil and acetone as volatile component. It is confirmed that volatile component have little effect on bubble nucleation in silicone oil.

抄録全体を表示

This experimental research concerns an air-bubble-jet flow in water. We apply a three-dimensional particle-tracking-velocimetry (3D-PTV) technique to the flow, in order to obtain both air-bubble and ambient-liquid (water) velocities. In bubble-velocity measurements, we regard air bubbles as tracers. And, in liquid-velocity measurements, we regard polyethylene particles suspended in the liquid as tracers. Then, we visualise the three-dimensional motions of air bubbles and ambient liquid. As we record stereo images using two high-speed video cameras, we can get timely-consecutive information of air-bubble and ambient-liquid motions. As a result, we quantitatively reveal the three-dimensional unsteady flow of a simple bubble-jet plume near an air nozzle exit.

抄録全体を表示

In a single-stage classification system using an almost rigidly rotating flow in which very small feed-powder particles suspended in water with a low mass-concentration are accurately classified into fine and coarse products by the difference in centrifugal force and fluid drag acting on each particle due to the particle-size difference, with the aim of raising throughput by increasing flow rate, we have conducted classification experiments. Consequently, we have reached the following conclusions. (1) In raising throughput with increasing Rossby number by decreasing Ekman number for a constant centrifugal-effect parameter, 50% and larger-particle-side cut sizes scarcely change and smaller-particle-side ones become large, so that classification accuracy becomes better. (2) In raising throughput with increasing feed-ratio for constant values of centrifugal-effect parameter and Ekman number, 50% cut size do not change so much, smaller-particle-side cut sizes become small and, larger-particle-side cut ones tend to become large, so that classification accuracy becomes worse.

抄録全体を表示

In a single-stage classification system using an almost rigidly rotating flow in which very small feed-powder particles suspended in a liquid medium (water) are accurately classified into fine and coarse products by the difference in centrifugal force and fluid drag acting on each particle due to the particle-size difference, with the aim of raising throughput by increasing concentration of feed suspension, we have made dense-slurry classification-experiments in order to pursue suitable classification-conditions in high-concentration processes. Consequently, we have reached the following conclusions. (1) In a large-particle classification both higher feed-ratio at the initial water-feed for a dense classification than that for a dilute one and resetting the feed-ratio of slurry to that of water just before classification allow an accurate dense classification with the same cut size as that for a dilute one. (2) In a small-particle classification, the difference in classification conditions causes little difference in classification performance.

抄録全体を表示

With the final aim of theoretically and numerically analyzing the performance in a dilute concentration of the particle classification using almost rigidly rotating flow, in the present study we have verified and improved theoretical linear solutions of a Stewartson-layer flow including inner and outer layers and their Ekman extensions derived in our previous studies, using numerical solutions. Also, we have considered the influence of the Saffman and rotation lifts and Basset force in the translation of a particle (Basset-Boussinesq-Oseen equation) on the particle trajectory derived by neglecting the lifts and force. Moreover, we have considered the influence of rotating motion of a particle on the particle trajectory derived by neglecting the motion.

抄録全体を表示

In a triple-product classifier using an almost rigidly rotating flow in which very small feed-powder particles suspended in a liquid medium (water) with a low mass-concentration are accurately classified into fine, medium and coarse products by the difference in centrifugal force and fluid drag acting on each particle due to the particle-size difference, with the aim of improving the performance of a medium product by controlling the classifier-shape, flow-rate distribution and governing parameters, we have considered the performance by numerically simulating the liquid-medium flow with the Navier-Stokes and continuity equations and the particle motion with the Basset-Bousinesq-Oseen equation. Consequently, we have reached the following conclusions. (1) When the width of medium-product outlet is varied, the mean diameter of the medium product changes. However, it is kept constant by suitably controlling the flow-rate distribution and governing parameters. (2) Narrowing the medium-product outlet brings better uniformity of particle and lesser yield.

抄録全体を表示

The present study reports the mechanism of particle deposition onto a channel wall in numerically simulated turbulent pipe flows. Large eddy simulation of the incompressible Navier-Stokes equations was performed to calculate the time-dependent turbulent flow field of continuous gas phase. The particles were placed at random initial locations in the pipe, assuming that the initial velocities in the lateral direction equaled to zero. The subsequent motion of particles was tracked individually using a simple Lagrangian equation. The particle relaxation time effect and particle concentration effect on the rate of particle deposition were investigated. Small particles were deposited onto the wall mainly due to the contribution of the lift force. Both the inertial and lift forces were of importance for the deposition of medium-sized particles. In the case of large particles, inertia acted as the resistance rather than the driving force of the deposition. Under high droplet concentration conditions, the turbulence modulation in the continuous gas phase is one of the primary causes of the reduction of the deposition mass transfer coefficient observed.

抄録全体を表示

We calculated tracer diffusion in a sheared suspension of non-Brownian rigid spheres and propose a new numerical method based on a boundary element method and Stokesian dynamics method. We present details of the numerical method and examine the accuracy of the method. The limitation of semi-diluteness is due to the accuracy of tracer velocity calculation. The results show that the diffusivity of fluid tracers is greater than that of suspended spheres in the semi-dilute regime. The diffusivity of velocity gradient direction is about threefold greater than that in the vorticity direction. Simple scaling demonstrates that the diffusivity of fluid tracers increases with the square of the volume fraction of spheres in the semi-dilute regime, which is confirmed numerically.

抄録全体を表示

Measurement of particle dispersion has been made in stationary turbulence with nearly zero mean velocity, which is generated by four sets of rotating grid. Particles examined are sufficiently small compared with Kolomogorov length and terminal velocity is greater than turbulent velocity. Under these conditions, particle dispersion exhibits the effect of crossing trajectories and it is found that velocity field seen by particle is anisotropic.

抄録全体を表示

The sedimentation of partially suspended particles in fluid has been studied experimentally. We have examined whether collective or individual motion of particles is dominant during sedimentation, i.e., whether the particles settle as a continuous suspension or they settle individually relative to surrounding fluid. We observed the settling of a stratified suspension which has both the upper and lower interfaces of concentration in quasi-two dimensional vessel. The experimental observation shows that the gravity-induced instability of suspension-fluid interface governs the particle motion and the suspension behaves as a continuous fluid for high concentration and small particle size. However, individual motion of particle relative to fluid stands out in case of large particles with low concentration. The transition from their collective to individual behaviors can be predicted quantitatively by a new parameter which expresses the border resolution of the concentration interface.

抄録全体を表示

Recent progress of an immersed-boundary (IB) method to deal with multiple moving interfaces is introduced. Our IB method of body-force type has extensibility by the combination with finite-element method (FEM), volume-of-fluid (VOF) method, discrete-element method (DEM) and so on. In this review article, some results are briefly demonstrated: IB-FEM for multiple soft particles; IB-VOF for gas-liquid-solid three phase flows; IB-DEM for the formation of particle agglomerates. Further developments for high Reynolds number flows and heat-transfer will be mentioned.

抄録全体を表示

An IBM approach for the direct numerical simulation of convective heat transfer in particle-laden flows is proposed. An immersed boundary method (IBM) used in this research is body-force type, which has been developed by the authors. It can effectively deal with multiple moving boundaries and solve the temperature field not only of fluids outside solids but also inside solids. It is assumed that the fluid is incompressible and Newtonian, and buoyancy caused by density difference is calculated with the use of Boussinesq approximation. In calculating the heat flux between fluids and solids, its continuity is particularly considered. The applicability of this method is demonstrated through the simulation of simple two-phase flows.

抄録全体を表示

The behavior of flows containing dense particles is very complex. Due to the particle-particle collision effect and hydrodynamic effect caused by the fluid existing in-between particles, particles make spontaneous structures. Flow characteristics are heavily depending on these internal structures and it is important to know why and what sort of structure is formed in the flow field. In the present study, internal flow structures of the flow containing dense particles are calculated by coupling Full-resolved DNS and DEM (Discrete Element Method).

抄録全体を表示

The lattice Boltzmann method with an elastic model is applied to the simulation of two-phase flows containing deformable bodies with viscoelastic membranes. In the model, not only shear deformation of the membrane but also change in the total volume and the total surface area of the membrane are considered. In addition, the present method enables us to give different viscosity of the fluid inside the membrane from that of the fluid outside the membrane. By using the method, the deformation of a body under shear flows is simulated to investigate the effect of the viscosity ratio of the fluids. It is found that the deformability of the body decreases with relative increase in the viscosity of the interior fluid. Also, the behavior of two biconcave bodies in a square pipe flow is simulated. It is seen that circular flows appear in the gap between the bodies.

抄録全体を表示

Cahn-Hilliard (CH) method is one of the interface-tracking method for two-phase flows. An advantage for CH method is that it can simulate complex behavior of interface relatively easily. On the other hand, the simulation for two-phase flows including fine disperse phase requires more accuracy of interface-tracking. The accuracy of interface-tracking due to diffusion by CH equation should be improved. Hence, in the present paper, the characteristics of diffusion of order function by CH equation is investigated. We focus on the mobility which means the anisotropic characteristic of diffusion in CH equation, and evaluated accuracy of interface-tracking for 2D and 3D single rising bubble.

抄録全体を表示

Using an Interface-Tracking Method coupled with an Immersed Boundary Method (IBM), a bubble-wall collision problem under the effect of gravity is resolved. The gas-liquid interface is captured by the Interface-Tracking Method, and the whole fluid field is described by the body (the interface) fitted coordinate system. Implementation of the wall in the fluid is based on the IBM. This coupled method enables us to investigate the dynamics of the flow between the bubble and the wall in detail. In the present study, the bubble-wall collision is analyzed, and a flow in the liquid film between the bubble and the wall is discussed.

抄録全体を表示

The present study aims to numerically investigate gas-liquid flows in a micro-channel. In such flow conditions, surface tension forces exerted on gas-liquid interface and wettability on the channel walls are dominating factors. We selected VOF (Volume of Fluid) method for capturing gas-liquid interfaces. Instead of using CSF (continuum surface force) model, Phase-Field method is introduced to calculate surface tension forces. This combined method preserves volume of each fluid and at the same time, we can easily impose boundary conditions to consider a contact angle.

抄録全体を表示