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Experimental
Three
facilities may be used for flow visualization and a number
of shapes, models of HPVs, or their components are available. The smoke tunnel
and the fish-scale water tunnel permit the flow to be visualized but are
not useful for quantitative measurements. The water channel and dye source permit
quantitative measurements to be made.
Use one of the visualization
facilities to explore the general flow behavior past a number of shapes.
Alter the orientation of these shapes with respect to the flow direction and
carefully observe how the flow changes. For a given shape orientation change
the velocity of the fluid and observe its effect on the flow around the object.
Is this behavior shape orientation dependent? If so, explore this effect.
Once
you have a feel of how flows are behaving, select a model to examine
in the water channel. For example, different models of tire-wheel combinations
are provided, a road bike configuration, a mountain bike configuration,
and an aerodynamic configuration that might be employed on a track bike.
Each of these may be mounted in the water tunnel and the flow around them visualized
by the injection of dye into the flow at various locations around the
model. The water speed may be varied up to a maximum flow of about 0.3 m/s.
Compute the Reynolds number for the system and compare with the values that are
expected for a bicycle wheel moving through air at realistic velocities.
Move the dye injector so that it can introduce dye into the boundary layer.
Start at the front of the model and move the injection point towards the rear.
Locate the position at which the dye no longer flows past the model but fills
a boundary layer region with color. The point at which this occurs is the
point at which the flow separates and turbulence starts. This position will
depend on the flow velocity and the shape of the model. For each tire model,
measure the velocity dependence of this point.
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