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Turbulence measurements in shallow shear flow using video imaging method

McGill University
Publication Date
  • Hydrology.
  • Engineering
  • Civil.
  • Engineering
  • Mechanical.


Quasi-two-dimensional turbulent flows were produced in a tank of small thickness to study confinement and friction effects on large-scale turbulent motion of small depth. The tank was constructed of two parallel walls. The space between the walls (4.4 cm, 1.57 cm and 0.59 cm) was small compared with the height (108 cm) and the width (210 cm) of the tank, and was varied during the experiments for different confinement and friction effects. Two series of experiments were conducted. In the first series turbulent flows were produced by the injection of water in the form of shallow jets into the tank filled with water of the same density. In the second series turbulent flows in the form of shallow plumes were produced by releasing saline solution from a line source, located at the top of the tank, into the tank filled with water. Dye was injected with the source fluid as the tracer. The concentration of the dye in the shallow turbulent flows was determined using a video imaging technique. From the initiation of the turbulent motion at the source to the final interaction of the jets and the plumes with the tank, the entire sequence of events was recorded by a video camera. The unsteady turbulent motions were analyzed using the recorded video images. The large-scale turbulent flow in the small space between the walls of the tank is confined to essentially two-dimensional motion, and the motion is retarded by the force of friction. The confinement effect was evaluated from the data of the shallow plume experiments, as the friction effect is neglible compared with the buoyancy effect in the case of the plume. Friction, however, is significant in the case of the jet. The effect of the friction, evaluated from the data of the shallow jet experiments, was found to have a profound effect on the entrainment processes. These findings are useful for turbulent modelling of the shallow shear flow and on its application to the large scale heat and mass exchange processes in the atm

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