Saburo Komura

On the Accuracy of the Correlation Method

The correlation method, which is one of the image processing techniques, have been widely used for obtaining velocity distributions from visualized images of flow. The accuracy of this method, which has not been discussed in detail so far, is examined by simulating tracer-particle images of some simplified flows.

An Image Processing System for Analyzing Flood Photographs Using Correlation Technique

An image processing system for analyzing aerial flood photographs is constructed using the correlation method. The system, composed of a personal computer and an image scanner, efficiently uses a mouse for improving the human interface. The two-dimensional velocity distributions obtained for the Yodo River represented streaklike velocity patterns near the river-bank, which corresponds well with the surface flow patterns of the photographs.

Investigation of Large-Scale Separated Eddies at Confluence by Using Image Processing Technique

Kinematic characteristics of large-scale eddies at a two-dimensional confluence are examined by using a correlation method, one of the image processing techniques. In this paper, a method for detecting and correcting erroneous velocity vectors, calculated by the correlation method is presented and it is used to obtain successive velocity fields of the water duct confluence flow of the discharge ratio Qr=0.2 and 0.4 at Re=3-104. When a reverse flow region decreases, the results show that several small scale eddies are created and they are convected at a speed nearly equal to the mean flow velocity.

Experimental Study of Hydraulic Functions of Arched Weirs

Effects of the plane shape of a weir on the downstream flow structures are experimentally examined. Arched weirs having different curvatures, an arched one set in reverse direction and a straight type weir, are used for experimental study. Mean and turbulent velocity distributions and shear stress distributions are measured in the downstream region of each weir. It is found that arched weirs converge the flow to the center portion of the channel, while a reverse-arched type diverges the main stream to the side portions of the channel. Deduced structures of the flows are also presented.

Analysis of the flow at a right-angled confluence by a discrete vortex method.

Two-dimensional discrete vortex method is applied to the flow at an open-channel confluence. Mean and turbulent velocity characteristics together with the size of a recirculating region are calculated with a reasonable accuracy and compared with open-channel experimental results. Also, unsteady large scale struc-ture of the flow in the recirculating region including formation and decomposition of vortices is favorably simulated by the proposed model.