Kazunari Katagiri

Spreading behavior of an impacting drop on a structured rough surface

The spreading of water drops impinging on structured rough surfaces is studied experimentally. The rough surfaces are specially prepared with a regular pattern of surface asperities. The arrangement of the square-shaped surface asperities creates channel-like grooves on the surface. A video microscope along with a controlled light exposure system is used to construct the image sequences of the spreading process. The images are digitally analyzed to measure the temporal variation of the spreading drop diameter 2R. Results are obtained for three rough surfaces with varying asperity heights in the range of 100-500 \mu m and for different impact drop conditions with Weber number We in the range of 35-225. The results on the temporal variation of 2R show that, on the structured rough surfaces, the spreading occurs simultaneously both inside and above the texture pattern of the surfaces. For a given surface geometry, the volume of liquid flowing inside the grooves of the surface increases with increasing We.Consequently, the values of 2R measured inside the texture pattern are larger than those measured above the texture pattern, and their difference increases with increasing We. The arrangement of the surface asperities influences the spreading pattern of an impacting drop spreading axis symmetrically. For the texture geometry used in the present study, the spreading pattern resembles a regular rhombus shape for the impact of low We drops and becomes complex at high We. The spreading distances, measured both inside and above the texture pattern of the structured rough surfaces, are nearer to the measurements recorded on the smooth surface if the asperity height of the rough surface is smaller than the thickness of the spreading liquid lamella;however, the surface asperities influence the spreading pattern drastically and create a liquid splash.

Characteristics of Ozone Jet Generated by Dielectric-Barrier Discharge

The characteristics of ozone jet generated by atmospheric-pressure coaxial dielectric-barrier discharge has been experimentally clarified through the visualization of discharge and also by the measurement of ozone concentration for various operating conditions, such as applied voltage, frequency, and gas flow rate. It is shown that the ozone production is highly controllable with applied voltage, and 1500 ppm of ozone can be produced at the input power as low as 72 W.

Dynamic behavior of magnetic liquid drop on a solid base subject to magnetic field and vertical vibration

Abstract The surface responses of a single magnetic fluid droplet on a horizontal solid nonmagnetic base subject to magnetic field and vertical vibration have been investigated. It was found that the magnetic liquid droplet responds to the excitation in elongation and contraction. Non-linear responses were also observed at higher excitation levels.

Dynamic behavior of a magnetic fluid jet injected from a vibrating nozzle

Abstract This paper describes an experimental study of the dynamic behavior of magnetic fluid jets which are injected from a vibrating nozzle into the atmosphere. It was found that an intact liquid jet can be made to bifurcate continuously into a pronged jet by vibrating the nozzle with certain combinations of frequency and acceleration. The effects of the magnetic fields on the drops produced by the jet breakup are also revealed.

Magnetic field effects in the impact of a magnetic fluid drop

Abstract The impact phenomena between a magnetic fluid drop and paper on the hard rubber mat, subject to a magnetic field, have been investigated. Effects of a magnetic field on the spread area of a magnetic drop and on the velocity of radial flow were revealed with a three-dimensional motion analysis system.

Some studies of magnetic liquid sloshing

Abstract The results of the experimental studies of magnetic fluid behavior in the laterally vibrated rectangular and cylindrical containers subject to magnetic fields are presented. Some effects of applied fields on fluid surface responses in the rectangular container and disappearance of drops on the fluid surface in the cylindrical container are noted.

EVALUATIONS OF CLUSTER STRUCTURE AND MAGNETO-RHEOLOGY OF MR SUSPENSIONS

In the present study, we sysnthesize two types of MR fluids with different particle shapes and sizes. The magnetic functions are evaluated circulatingly by the analysis of cluster formation, rheological properties in the applied magnetic field and damping characteristics in the MR damper, comparing with those of commercial MR fluids. Final objective is to provide the fundamental data for the development of newly advanced MR fluids. The main topics consist of geographycal cluster formation depending on particle shapes and sizes, relating to the apparent viscosity and yield stress with magnetic flux density and further equivalent damping coefficient of two newly sysnthesised MR fluids comparing with those of LORD MR fluid.

The effect of target roughness on the impact phenomena of magnetic fluid drops

Abstract Experimental studies of the impact phenomena between a magnetic fluid drop and the rough solid surface under applied magnetic fields were performed using a high speed digital video camera system. The direction of applied magnetic fields are perpendicular to the target plane. Effects of the target roughness on the impact phenomena were found to be important for the spreading process of magnetic fluid flow. It was also found that the formation of spikes on the impact pattern left by magnetic drops is not clear at higher values of the roughness number.

Dynamics of magnetic fluid foam

Abstract The dynamics of magnetic fluid foams in two dimensions have been studied experimentally. The growth process for coarsening of magnetic fluid cells was observed under both a non-magnetic and a magnetic field. It was found that the foam growth depends on the intensity of the magnetic field.

Evaluation of Sealing Characteristics in MR Fluid Channel Flow Relating to Magneto‐Rheological Properties

Experimental analyses are conducted on the rheological properties of a commercial MR fluid in a rotating shear mode and on sealing characteristics of MR fluid with correlating the MR fluid structure in pressure mode. The time evolution of axial pressure distribution in pressure mode under a magnetic field and pressure loss at steady flow are also discussed in detail to provide the fundamental data for the novel application of MR seal to a medical or safety devices.