Ryota Tsubaki1 and Ichiro Fujita2
1 Graduate School of Science and Technology, Kobe University, Rokkodai, Nada-Ku,
Kobe 657-8501, Japan
2 Department of Architecture and Civil Engineering, Kobe University, Rokkodai, Nada-Ku,
Kobe 657-8501, Japan
E-mail: ifujita@kobe-u.ac.jp
Received 21 December 2004, in final form 16 March 2005
Published DD MMM 2005
Online at stacks.iop.org/MST/16/1
Abstract
This paper presents a new innovative method for measuring two-dimensional
water surface configurations. This method uses a pair of sequential images
captured by two high-resolution CCD cameras arranged in a stereo position.
The idea of the method is to make the water colour white so that the
instantaneous water surface appears like a solid surface with a clear pattern
when an irregular pattern of light is projected onto it. It should be noted that
this method is suitable to measure waves with small amplitude accurately
and at the same time discontinuous surface robustly. First, we explain the
measurement principle and the experimental procedure for obtaining stereo
images. Secondly, we examine the measurement accuracy by applying our
technique to still water surface and calibrated wavy plates. Finally, we
represent applications of the technique applied to the actual flow field such
as surface waves and ripples generated in a shallow water box. The result
shows that we can trace the propagation of small waves as small as 1 mm. In
another application, we measure periodic surface fluctuation generated at an
asymmetric cavity installed in an open-channel flow, demonstrating
robustness of the technique applicable even when a discontinuous surface
with wave breaking occurs in the course of the measurement.
Keywords: water waves measurements