Kiyoji Kaneko

Flow visualization and image analysis of gas-phase AC corona discharge induced electrohydrodynamic liquid flow in a stratified fluid

A phenomenon of AC gas-phase needle-plate corona discharge induced electrohydrodynamic (EHD) liquid flow in a stratified fluid has been investigated experimentally. The flow visualization of flow pattern is carried out by a fluorescent dielectric liquid tracer, where the steady EHD liquid motion induced by the corona discharge is presented in visual impressions. The results show that the EHD liquid flow direction on an electrode axis is not from needle to plate electrodes axis when the needle position was above the liquid layer. For the case of the needle electrode tip immersed into the dielectric liquid, it is well known that the dielectric liquid flows in anticlockwise rotation by contraries. The flow velocity distribution is experimentally obtained by a particle image velocimetry with image processing, where the measurement system takes sequential digital images of flow field illuminated by a laser light sheet for computed tomography. The mechanistic model based on interfacial momentum transfer effects on liquid-phase fluid motion is discussed in detail.

An experimental study of the optical characterization of AC electrohydrodynamic fields by particle image velocimetry

This paper describes the optical characterization of electrohydroctynamic (EHD) fields in liquid dielectrics subjected to AC high voltage. The velocity fields are obtained by a particle image velocimetry (PIV). The EHD fields are formed in 10 cSt silicon oil and ethanol with different dielectric constants. The PIV requires illuminated tracer particles for the fluid flow visualization. For the requirement, particles of aluminum powder with good conductivity and polyethylene powder with high resistivity are suspended in the liquids and are not related to electrification because of the AC electric fields. From the viewpoint of EHD flow visualization, the main purpose of this study is velocity measurements of the tracer particles moved by electrostriction in the fields. The PIV applied to the measurements gives us an interesting experimental result of velocity fields for the EHD phenomena.

Experimental study on space and time correspondence of traveling particles for three-dimensional particle image velocimetry by genetic algorithms

An image analysis method is proposed for space and time correspondence of discrete traveling particles and is intended for a 3D velocity measurement by particle image velocimetry (PIV). In a principle of the PIV, the particles illuminated for fluid flow visualization are tracked during time fixed, and the velocity is obtained by a computational analysis of moving distance and direction of the tracked particles. This study is based on a thought that the purpose of particle tracking is accomplished by space and time correspondences of the particles The time correspondence is a combination process to find identical particles from particle distributions in two optical images captured with the time difference. Also the space correspondence is a combination process to find identical particles from plural images captured in more than two directions at same time. This process is a suitable image analysis for space position measurement of particles, it is though that the analysis method becomes a conventional technique overcoming the difficulty. In this method, the particle velocity is directly obtained from an optimum correspondence of the discrete particles in space and time. This study devises an application of genetic measurement of particles flowing around a rectangular column and shows the effectiveness of 3D image analysis with genetic algorithms.

Measurements of unsteady electrohydrodynamics flow from injection charges on free surface by particle image velocimetry

The authors have been researched on the velocity field measurements of the electro-hydrodynamics (EHD) flow caused by AC corona discharges. From the experimental results for several kinds of dielectric liquids with some viscosity it has been found a transition process from the steady EHD fluid flow toward the turbulent flow. Since this process depends significantly on the viscosity of EHD fluid, it has a threshold determined by the Reynolds number. This paper describes about the experimental results of this transition process obtained from the silicone oil with different viscosities. To understand the fluid flow structure of EHD caused by the corona discharges, the velocity fields of the unsteady EHD fluid flow are successfully obtained by means of the flow visualization technique and the particle image velocimetry (PIV) technique.

Experimental flow measurements of electrohydrodynamic convection fields by particle image velocimetry

A method of particle image velocimetry has been proposed for measuring flow velocity of electrohydrodynamic (EHD) convection fields in dielectric liquids. The flow velocity is calculated from the average moving distance and direction of the tracer particles traveling along with the fluid flow. The method has the great advantage that it enables the continuous measurement of the velocity distribution of unsteady flow fields. Some interesting velocity distributions are obtained for silicone oil which is electrically and thermally stressed under non-uniform electric fields. The experimental results show an analogy between natural convection and the EHD convection. We conjecture that the EHD convection is formed as a driving action causing energy release at the tip of the electrode.

PIV Measurements of Electrohydrodynamic Flow from Injection Charges on Free Surface of Dielectric Liquid

We have been researched on the velocity field measurements of EHD flow. Thus paper describes PIV measurements of the EHD flow that is created by injection charge motion on free surface of dielectric liquid. Some experimental results show steady EHD flow with an interesting vortex for lugh resistivity dielectric liquid such as silicone oil. The velocity fields of the EHD flow are successfully obtained by means of the flow visualization technique and the PIV technique.

Experiments for Verifying Performance of 3-Dimensional Particle Image Velocimetry on Genetic Algorithms

This particle image velocimetry has been studied to find velocity vectors of illuminated particle motion by combinations for identifying particles between two sequential digital flow images. The authors propose the method of applying genetic algorithm to the particle image velocimetry. It is enable us to get the plural of velocity vector at the same time. This paper explains the application of this method to 3-dimensional particle image velocimetry. This method is based on a space correspondence for calculating 3-dimensional particle positions and a time correspondence for calculating the particle velocity vectors. In addition, this paper ijntroduces the results of a numerical simulation using flow model around a prism.

Estimation of Accumulated Charge on Complex Insulator Surface by using Axisymmetric Three Dimensional FM with Fixed Sand-Bed.

The surface of insulators accumulates charge during subject to high voltage stresses electrically.The surface charging causes deteriorations of electrical performance and durability of high voltage insulators in gas. In this paper, we describe a result of visual analysis of electric fields with accumulation charge on complex insulator surface to clear the effect of surface charging on the dielectric strength. Moreover, the accumulated surface charge on insulators is estimated by flow patterns obtained from axisymmetric three dimensional fluid flow mappers with fixed sand-bed.