Turbulent separated reattached flow in a two-dimensional curved-wall diffuser
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A turbulent separation-reattachment flow in a two-dimensional asymmetrical curved-wall diffuser is studied by a two-dimensional laser doppler velocimeter. The turbulent boundary layer separates on the lower curved wall under strong pressure gradient and then reattaches on a parallel channel. At the inlet of the diffuser, Reynolds number based on the diffuser height is 1.2×105 and the velocity is 25.2m/s. The results of experiments are presented and analyzed in new defined streamline-aligned coordinates. The experiment shows that after Transitory Detachment Reynolds shear stress is negative in the near-wall backflow region. Their characteristics are approximately the same as in simple turbulent shear layers near the maximum Reynolds shear stress. A scale is formed using the maximum Reynolds shear stresses. It is found that a Reynolds shear stress similarity exists from separation to reattachment and the Schofield-Perry velocity law exists in the forward shear flow. Both profiles are used in the experimental work that leads to the design of a new eddy-viscosity model. The length scale is taken from that developed by Schofield and Perry. The composite velocity scale is formed by the maximum Reynolds shear stress and the Schofield-Perry velocity scale as well as the edge velocity of the boundary layer. The results of these experiments are presented in this paper.
Key Wordsseparating flow boundary layer turbulent flow turbulence model Laser Doppler Velocimeter two-dimensional diffuser
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- Kline S J, Ferziger J H. Prediction of Complex Turbulent Flows: An overview-1985. In: Progress in Astronautics and Aeronautics S. B. Murthy ed, 1986, 102: 14–39Google Scholar
- Nakayama A. Measurements of separating boundary layer and wake of an airfoil using Laser Doppler velocimeter. AIAA, 1985, 85–0181Google Scholar
- Patrick W P. Flowfield measurements in a separated and reattached flat plate turbulent boundary layer. NASA, 1987, CR-4052Google Scholar
- Wadcock A J. Simple turbulence models and their application to boundary layer separation. NASA, 1980, CR-3283Google Scholar
- Culter A D, Johnston J P. An experimental investigation of the effects of initial shear stress distribution on a separating turbulent Layer. AIAA, 1984, 84–1583Google Scholar
- Schofield W H. Two-dimensional separating turbulent boundary layers.AIAA J, 1986, 24 (10): 1611–1620Google Scholar
- Lakashminarayama B. Turbulence modelling for complex flows. AIAA, 1985, 85–1652Google Scholar