Affiliations: Dr., Water Resources Research Center, Disaster
Prevention Research Institute, Kyoto University, Goka-sho, Uji-shi, 611-0011,
Japan. E-mail: sameh.kantoush@a3.epfl.ch | Swiss National Fund for Scientific Research (SNSF),
Bern, Switzerland | Professor, Director, Ecole Polytechnique
Fédérale de Lausanne (EPFL), Laboratory of Hydraulic
Constructions (LCH), Station 18, CH -1015 Lausanne, Switzerland. E-mail:
anton.schleiss@epfl.ch
Abstract: Shallow depth flow fields and low velocity magnitudes are often
challenges for traditional velocity measuring instruments. As such, new
techniques have been developed that provide more reliable velocity measurements
under these circumstances. In the present study, the two-dimensional (2D)
surface velocity field of shallow basins is assessed by means of Large-Scale
Particle Image Velocimetry (LSPIV). The measurements are carried out at the
water surface, which means that a laser light sheet is not needed. Depending on
the time scales of the flow and the camera characteristics, it is even possible
to work with a constant light source. An experimental application of this
method is presented to analyze the effects of shallow basin geometry on flow
characteristics in reservoirs where large coherent two-dimensional flow
structures in the mixing layer dominate the flow characteristics. The flow and
boundary conditions that give rise to asymmetric flow are presented. Asymmetric
flow structures were observed starting from basin shape ratios that are less
than or equal to 0.96. By decreasing the basin length and increasing the shape
ratio to greater than 0.96, the flow structure generally tends towards a
symmetric pattern.
