A three-dimensional open-channel flow having a rectangular block on one side of the channel wall was measured by applying a conventional 2-D PTV technique to the vertical and horizontal images visualized by a laser-light sheet. A high-speed video camera with 200 fps was used to capture about 4500 consecutive images, from which the mean and the turbulent properties were extracted by applying the binary image cross-correlation method. The cross-sectional secondary flows were obtained by combining

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... the 2-D velocity vectors in the vertical and the horizontal planes. It was made dear that the three-dimensional mean velocity field can be obtained with a reasonable accuracy by the presented PTV procedure.