Decay of Turbulent Swirl in an Annular Duct.
MINNESOTA UNIV MINNEAPOLIS HEAT TRANSFER LAB
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An experimental investigation was carried out to determine fluid dynamic properties of turbulent vortex flows i.e., flows with both tangential and axial mean velocities, in a concentric annular duct. The working fluid was air and the flow was incompressible. All measurements were made at a nominal Reynolds number of 130,000. The average axial velocity was on the order of 90 ftsec. Measurements were made with both a cylindrical pressure probe and a hot film probe. The swirl imparted to the flow in the inlet decayed as the flow moved down the test section. Extensive surveys of the velocity field were made for five different swirl rates with one of the swirl rates being that of zero swirl or straight flow. The term swirl rate refers to the relative magnitude of the inlet tangential velocity. Local axial skin-friction coefficients at the inner wall were determined at seven different axial locations for all five swirl rates. For the swirl rates tested, no regular shift in the skin-friction distribution is noted with increasing swirl rate except at the highest swirl rate where the distribution is considerably below the others. At the inner wall, axial velocity profiles were also presented in terms of law-of-the-wall variables. Good to relatively poor agreement with the universal velocity-distribution was achieved. Author
- Fluid Mechanics