Surface oscillations in flow past a side cavity using stereoscopic measurement and POD
R. Tsubaki
COE program researcher, Graduate School of Science and Technology,
Kobe University, Rokkodai, Nada, Kobe, Hyogo, Japan
and
I. Fujita
Professor, Department of Architecture and Civil Engineering,
Kobe University, Rokkodai, Nada, Kobe, Hyogo, Japan
Journal of Hydroscience and Hydraulic Engineering
Vol. 24, No. 2 November, 2006, 41-51.
SYNOPSIS
When a relatively large side cavity is created in an open channel, the influence of vortices in the shear layer
and circulatory flow is exerted on the main flow, causing surface oscillations and increased water levels. The
mechanism of the oscillation is still not clearly understood because of the complexity of the phenomena. In this
research, by using a stereoscopic surface measurement system developed by the authors, time-dependent water
surface configurations are successfully measured at a sampling rate of 12 Hz, from which general features of the
surface oscillation are made clear for a wide range of Froude numbers. Then, we applied the proper orthogonal
decomposition (POD) method to measure results. We found that the surface oscillation can be clearly decomposed
into a seiche-like major mode and sub-modes with smaller wavelengths.