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A Study of the Flow Structure of Tip Vortices on a Hydrofoil

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A detailed study of the tip vortices generated on a NACA-66 series hydrofoil is performed in the Purdue University towing tank. The investigation involves flow visualization experiments and pressure measurements performed under various test conditions. Laser induced fluorescence is utilized as the means of flow visualization. An argon ion laser beam is expanded into a thin sheet of light, which in turn slices a .vertical and lateral cross section of the flow field. Rhodamine dye is introduced into the field, either by injecting it from the surface of the model. As the model is towed through the tank, the dye became visible in the section illuminated by the laser sheet. The resulting image showed the vortex structure at that region, unobstructed by the rest of the flow. This image is recorded by a television camera which trails behind the model Pressure measurements are performed by using a system which includes a scanning valve and a pneumatic control mechanism. Ports are located on the model surface from which pressure information is obtained. The extensive number of ports warrants the use of a scanning valve, which pro rapid and efficient measurements. The pneumatic control device is necessary for data collection. Once collected, the information is routed through an analog to digital--- converter and sent to a personal computer to be stored and analyzed. Results obtained from the flow visualization experiments show several clear trends. First, the size of the tip vortex increases as it develops downstream along the hydrofoil chord. Second, the size of the tip vortex increases and its center line becomes more detached as the angle of attack is increased.

Subject Categories:

  • Civil Engineering
  • Marine Engineering
  • Fluid Mechanics

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