Binary Image Cross-correlation Research Articles

A novel particle tracking algorithm using polar coordinate system similarity

A new algorithm using polar coordinate system similarity (PCSS) for tracking particle in particle tracking velocimetry (PTV) is proposed. The essence of the algorithm is to consider simultaneously the changes of the distance and angle of surrounding particles relative to the object particle. Monte Carlo simulations of a solid body rotational flow and a parallel shearing flow are used to investigate flows measurable by PCSS and the influences of experimental parameters on the implementation of the new algorithm. The results indicate that the PCSS algorithm can be applied to flows subjected to strong rotation and is not sensitive to experimental parameters in comparison with the conventional binary image cross-correlation (BICC) algorithm. Finally, PCSS is applied to images of a real experiment.

B201 PIV/PTV解析アルゴリズムの高度化と応用

The analytical algorithm of PIV and PTV has advanced in the last two decades from simple cross correlation method to binary image cross correlation method, Delaunay tessellation method, velocity, gradient tensor method, and recursive cross correlation method. In parallel, useful post-processing schemes for PIV/PTV such as ellipsoidal equation method and inverse analysis method were proposed so that detailed flow structure could be evaluated including pressure field. This paper concerns with such a history of the research and future possibility for further advance of the PIV/PTV.

A novel algorithm for particle tracking velocimetry using the velocity gradient tensor

Most particle-tracking velocimetry (PTV) algorithms are not suitable for calculating the velocity vectors of a fluid flow subjected to strong deformation, because these algorithms deal only with flows due to translation. Accordingly, it is necessary to develop a novel algorithm applicable to flows subjected to strong deformations such as rotation, shear, expansion and compression. This paper proposes a novel particle tracking algorithm using the velocity gradient tensor (VGT) which can deal with strong deformations and demonstrates that this algorithm is applicable to some basic fluid motions (rigidly rotating flow, Couette flow, and expansion flow). Furthermore, the performance of this algorithm is compared with the binary image cross-correlation method (BICC), the four-consecutive-time-step particle tracking method (4-PTV), and the spring model particle tracking algorithm (SPG) using simulations and experimental data. As a result, it is shown that this novel algorithm is useful and applicable for the highly accurate measurement and analysis of fluid flows subjected to strong deformations.

A new tracking algorithm of PIV and removal of spurious vectors using Delaunay tessellation

A new algorithm of Delaunay Tessellation Particle Tracking Velocimetry (DT-PTV in abbreviation) is proposed for tracking particles in images of a PIV system by making use of the Delaunay tessellation (DT). The algorithm is tested by using numerically simulated particle images. The calculation results based on DT are compared with those obtained by a conventional algorithm of Binary Image Cross-correlation method (BICC). The new algorithm shows higher performance of obtaining more identical particles in two consecutive images correctly with shorter computation time even if the images contain many particles. A further application of DT to elimination of spurious vectors is also discussed.

Research on the algorithm of binary image cross-correlation for unsteady flow field measurement

In the present paper, the algorithm of Binary Image Cross-Correlation (BICC) was developed to measure the unsteady flow field. A vortex flow field was used to test the algorithm by numerical simulation. The results show that BICC is an effective algorithm for particle identification from consecutive images, the accurate velocity vector field can be obtained. The real velocity field in a valve chamber was measured by BICC in this study. From the full-field velocity information, the pressure and vorticity fields were also extracted by post-processing.

Particle Imaging Velocimetry Measurement of Particle Number Rate and Velocity for Falling Particles.

The number of particles passing through the whole field of interest in a unit time, referred to as the articles particle number rate, cannot be measured accurately and easily by the conventional methods when the number density of particles is high. However, there are many demands for whole field measurement of the particle number rate in various industrial processes. The purpose of the present investigation is to develop a new method for measuring the particle number rate by introducing PIV (Particle Imaging Velocimetry). In the present work, particles coming out of a hopper, and then falling in air or water were treated. Images of the falling particles were taken by a high speed video camera. Particle velocities were measured by the PIV based on the Binary Image Cross-Correlation Method (BICC), and the particle number rate crossing a plane could be computed from the mean velocity of particles and the number of the particles in the image. The performance of the present method for measuring the particle number rate was evaluated by numerical simulations and experiments. The experimental results showed that the particle number rate of a cloud of particles could be measured with high accuracy by the newly developed methods. The measurement precision of the particle number rate depends on the number of sampling video frames. Several seconds of video frames can yield sufficient precision of the particle number rate. The present research can be applied to on-line measurement of particles in many industrial fields.

131 開水路壁面せん断力のPTVによる計測

Wall shear stress distributions of open-channel flows were measured making use of the binary image cross-correlation method (BICC), one of the PTV techniques. Flow fields close to the wall were visualized by a laser light sheet with small tracer particles and the particle images were recorded on a DV format tape using a digital video camera. The images were transferred to a personal computer as a movie file(an AVI file), divided into a series of bit map files(BMP files), and finally transformed to gray-scale binary data before the PTV analysis. Thousands of consecutive images were successfully captured by using this procedure. The shear stresses were estimated from the distributions of turbulence properties very close to the wall. Several estimation methods were compared and their accuracy was discussed in detail.

B214 液中気泡挙動のファジィ推論に基づくPIV計測

The conventional PIV or PTV systems cannot work well in the measurement of bubbly flow. Neither the gray level cross-correlation method and binary image cross-correlation method nor fourframe PTV can track bubble properly because whole image of each bubble cannot be always recorded due to illumination problem. High velocity and random motion of bubble are also the causes for the problem. The behavior of bubble in image sometimes causes an uncertainty to a degree and therefore cannot be measured well by the previous PIV methods. Fuzzy logic has proven to be a simple and robust method for process control. In this paper, the fuzzy logic has been applied in the measurement of bubbles in a gas-liquid two-phase flow. Two frames of digitally recorded, single exposure particle images are used. The purpose of current research is to establish a novel PTV method based on fuzzy logic to measure the bubble behavior from bubble images with uncertainty.

131 相関係数に関する検討

Cross-correlation coefficient used in the binary image cross-correlation method for PIV has been used without mathematical strict proof, although the method is thought to be convenient and efficient to analyze the particle images due to the high speed algorithm for particle identification. In the present study, the basic equation of image cross-correlation coefficient and its extension to Delaunay tessellation method are derived from mathematical foundations, and the generality is discussed.

HIGH POTENTIALITY AND APPLICABILITY OF 2-D AND 3-D PARTICLE IMAGING VELOCIMETRY

In a calculation of an image cross-correlation coefficient, an identification of each particle is calculated based on the similarity of the particle distribution pattern between two-consecutive images using the cross-correlation coefficient. The calculation of the cross- correlation coefficient for 8-bit image data is time consuming. However, its calculation time using the binary image data is shorter. Consequently, the binary image cross-correlation method has the advantage of the high speed algorithm for the particle tracking. The mathematical fundamentals of the binary image cross-correlation are given and generalized. Secondary applications of the method are presented, ie, two-dimensional measurements of unsteady flows inside and outside a hollow circular cylinder, a torque converter internal flow, a flow with a bubble, a heart muscle movement, and also a three-dimensional measurement of a two-phase flow in a bubbling-jet water vessel. Finally, the high potential and applicability of the method are described.

239 トルクコンバータ内部流れのPIVによる研究

The present study deals with the torque converter (T/C) internal flow which is used for automatic transmission car. The T/C internal flows are visualized by the particle tracer technique. The technique, called the binary image cross-correlation method is applied to measure the flow velocity distributions. Since the velocity vectors are computed discretely at the particle positions in the PIV, some rearrangement methods are needed to get the velocity vectors at any point in order to extract the other physical informations. In this study, three new methods for velocity vector rearrangement using the equation of continuity, boundary element method (BEM in abbreviation), and the least square method are applied to the PIV results of T/C internal flow, and the performance of the new methods are examined.

223 一様流中で急回転急停止する中空円筒の内外流れのPIVによる計測

The purpose of the present study is to measure and investigate unsteady flows inside and outside a hollow circular cylinder with sudden rotating and stopping in a uniform flow and finally in order to obtain some fundamental data about the virtual mass effect. The flows inside and outside a hollow cylinder which is made of transparent acrylic resin are visualized by the particle tracer technique and analyzed using the PIV technique based on the two-dimensional binary image cross-correlation method. As a result, the unsteady whole field flows are discussed.

246 二値化画像相関法に基づく3時刻3-D PTV計測

This paper proposes a new three consecutive time picture cross-correlation 3-D PTV (Particle Tracking Velocimetry), which is based on the combination of the binary image cross-correlation 2-D particle tracking between two projected screens, stereo pair matching and 3-D particle identification on three consecutive time pictures at regular time intervals. The present technique is applied to measure the flow structure of a weak bubbling-jet two-phase flow, and as a result, about one-hundred and fifty particle velocity vectors in the liquid motion and several higher velocity vectors of air bubbles are successfully measured.

110 二値化画像相関法PTVに関する二・三の数学的考案

Cross-correlation function used in the binary image cross-correlation method developed by Uemura, T., Yamamoto, F., and Koukawa, M. is used without mathematical strict proof, although their method is thought to be convenient and efficient to analyze the particle images due to the high speed algorithm for particle identification. In the present study, the binary image crosscorrelation function is derived from mathematical foundations, and the generality is discussed. Since the velocity vectors are computed discretely at the particle positions, some interpolation methods are needed to rearrange the velocity vectors at the grid points in order to extract the other physical informations. The three following new mathematical interpolation methods (differential form of equation of continuity, integral form of equation of continuity, and boundary element method) are proposed in the present paper.