Tomomasa Uemura

High-speed algorithm for digital PIV analysis of multiple-exposure pictures

In order to realize the high speed analysis in the incoherent high particle density PIV (IHD- PIV), the further advancement in both hard and soft wares is expected. Assuming the high resolution digital pictures, a new algorithm for the PIV is proposed. Although, spatial resolutions of existing video cameras are not sufficient for the PIV, the device is still useful for the purpose, since its the real-time recording and the future advancement is expectable. Assuming that a lot of tracer images are not clearly separated in the PIV pictures on a low spatial resolution medium, a new algorithm is developed which is based on the binary-image correlation method and the velocity vector histogram method. The whole analysis process could be performed by a personal computer and its can be finished in practically short seconds.

Mixing Flow in a Cylindrical Vessel Agitated by a Bubbling Jet - Application of Image Processing Velocimetry

A mixing flow in a cylindrical vessel agitated by a bubbling jet is measured quantitatively applying the binary cross correlation method, which is one of the particle tracing methods. With this method, not only flow patterns, but also quantitative measurements such as instantaneous velocity distributions, velocity fluctuations and particles paths can be obtained easily in a short time.

News 3D-PTV Algorithms Based on Correlation Between Binary Images

Two new algorithms of three-dimensional binary correlation method (BCM) are proposed for particle tracking velocimetry. The principal part of the method is an algorithm to evaluate a similarity between two local patterns of distributed particles in a three-dimensional space. Introducing a function, which represents a degree of closeness of two particles, the similarity with a reduced consumption of computer resources. Another method compares distributions on a two-dimensional plane by tranforming the coordinates of original patterns. The performances of the methods are examined by computer simulations.

2D PTV Based on Binary Correlation Method and Its Application to Fluctuating Flows

A two-dimensional particle tracking velocimetry (2D-PTV) based on binary correlation method which has been proposed by the authors before is applied to measure fluctuating flows around two circular cylinders. The experiments are carried out in the three types of tow cylinder arrangements: (a) tandem, (b) side by side, and (c) staggered. Analyzing the pictures of the flows visualized by the hydrogen bubble technique, instantaneous velocity distribution, root mean square (RMS) values of the fluctuating parts of the flows, streamlines and vorticity contours are obtained. From these experimental data the flow mechanism are discussed.