Geoscience Reference
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Siphon for
introducing
dye streak
Float and scale
for measuring
discharge and
velocity
Glass-sided tank
containing
glass test tube
immersed in
water
b - Bell-shaped entrance
section to glass tube
ensures smooth intake
of water to minimize
inlet disturbance
b
Lever used to open
outlet valve and allow
variable throughflow
of water
Fig. 4.6
Reynolds' apparatus as presented in his 1883 paper.
Injected
dye-
streak
Flow
Laminar flow - dye streak passes downflow undeformed. You must imagine many such streaks, all
parallel in section view. Note: the effects of molecular diffusion in mixing water and dye molecules is
ignored at these flow velocities
Flow
Turbulent flow - dye streak passes downflow undeformed until a certain point when the dye streak
billows a few times and is then intermixed with the water by a system of flow-wide eddy motions
Flow
Turbulent flow - the dye streak billows shown above here are viewed with the aid of an instantaneous
electrical spark, providing a clearer view of the way that the billows spread and mix the dye through
the whole flow
Fig. 4.7
Details of flow patterns as sketched by Reynolds.
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