5 Turbulence Scale Effect
Experiments
Introduction
A series of flow experiments was conducted using the CHL precision flow
table described in Chapter 2. The objective of these systematic tests was to
evaluate the turbulence scale effect in geometrically distorted physical models for
distinct flow situations were considered and discussed in the following
paragraphs.
Case 1: Unconstrained flow separation at vertical edge
These experiments reproduced flow separation and downstream entrainment
that occurs in the lee of a protrusion placed at right angle to the flow as illustrated
in Figure 18(a). The edge of the protrusion was vertical, and downstream the jet
expansion was unhindered by any boundaries. This configuration is typical of
the downstream edge of man-made structures such as retaining walls that extend
a considerable distance into the flow. It was expected this configuration would
produce horizontal turbulence components that are much more pronounced than
the vertical components.
Case 2: Constrained flow separation at vertical edge
These tests were virtually identical with the unconstrained flow separation
with the only difference being the flow-parallel boundaries downstream of flow
separation as illustrated by Figure 18(b). The intent was to gauge the influence
of these boundaries on flow entrainment.
Case 3: Flow separation at sloping edge
These experiments duplicated the conditions of unconstrained flow
separation at a vertical edge except the edge was sloped as represented by the
sketch of Figure 18(c). Gap distance between the two walls is closest at the toe,
and the opening width increases toward the water surface. Turbulence generated
by flow separation was expected to have horizontal and vertical components with
similar magnitudes, so a scale effect was anticipated.
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Chapter 5 Turbulence Scale Effects Experiments
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