2 Coastal and Hydraulics
Laboratory Flow Table
Flow Table General Description
The precision flow table at CHL is used to examine flow problems related to
tidal flows in estuaries and currents interacting with inlet jetty structures. The
system maintains a constant flow discharge across a horizontal portion of the
table through a recirculating system regulated by valves. Water depth is
controlled by a downstream adjustable weir. Small-scale models depicting either
idealized flow boundaries or portions of actual projects are placed on the glass
horizontal test section of the flow table. Complex flow patterns created by the
scale model solid boundaries, such as regions of flow separation and turbulence
beneath the horizontal section of the table. The laser beams pass through the
glass bottom and measure two horizontal components of velocity at the vertical
elevation where the laser beams intersect. Complex flow patterns can also be
visualized using traditional techniques of dye injection, surface tracers, and
bottom tracers.
For Corps projects where 3-D flow structures are thought to be significant,
the flow situation can be clarified by fabricating a scale model of the actual
bathymetry and shore boundaries for use on the flow table. Changes to
bathymetry or upstream boundaries are easily simulated, and the impact is
immediately observed. Because many complex flow phenomena such as
separation and turbulence are reliably reproduced in small-scale physical models,
the flow table can be used as a validation tool in conjunction with development
of advanced hydrodynamic numerical models that incorporate these features.
Flow Table Details
The CHL flow table, shown in the photograph of Figure 3 and represented
schematically in Figure 4, is approximately the size of a billiards table. Flow of
water from the constant head tank (HT) is controlled by a valve, which assures
a steady flow rate feeding the upstream basin (IN). Water flows across the
horizontal 2.44 m 1.22 m (8 ft 4 ft) glass bottom of the flow table and spills
over the adjustable-height weir into the catchment tank (OUT), which in turn
overflows into the reservoir (RES). The reservior is detached from the flow
table to isolate vibrations of the pump as water is recirculated to the head tank.
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Chapter 2 Coastal and Hydraulics Laboratory Flow Table
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