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 Hydraulic
structures installed in rivers are often supported
on pillars, which under certain conditions generate
vortex systems in the flow. Structural problems can
occur if local flows cause systematic movement of sediment
near the foundations of a pillar. A combination of
physical tests and 3D CFD modeling is required to provide
engineers with sufficient details of the flow to optimize
their structural designs.
Generally, depending on the shape of
the pillar and the Reynolds number, separation occurs
in the stream and two types of vortex systems are formed.
For pillars with blunt leading edges, a “horseshoe” vortex
is generated around the pillar. If the Reynolds number
of the flow is between 140 and 300,000 a “wake” vortex
system is established with separating vortices generated
on alternate sides of the pillar (Von Karman vortex
street).
We compared STAR-CD calculations with
physical model testing. For the latter we used a flow
channel (800 cm long and 134 cm wide) with a blunt
leading-edge pillar (width 28 cm, length 126 cm) installed
on an asymmetric flow bed. The flow rate was a constant
108 l/s at a water depth at the pillar of 32 cm.
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