Affiliation:
1. United States Naval Academy, Department of Mechanical Engineering, Annapolis, MD 21402
2. National Aeronautics and Space Administration, Glenn Research Center at Lewis Field, Cleveland, OH 44135
Abstract
Detailed velocity measurements were made along a flat plate subject to the same dimensionless pressure gradient as the suction side of a modern low-pressure turbine airfoil. Reynolds numbers based on wetted plate length and nominal exit velocity were varied from 50,000 to 300,000, covering cruise to takeoff conditions. Low and high inlet free-stream turbulence intensities (0.2 and 7 percent) were set using passive grids. The location of boundary-layer separation does not depend strongly on the free-stream turbulence level or Reynolds number, as long as the boundary layer remains nonturbulent prior to separation. Strong acceleration prevents transition on the upstream part of the plate in all cases. Both free-stream turbulence and Reynolds number have strong effects on transition in the adverse pressure gradient region. Under low free-stream turbulence conditions, transition is induced by instability waves in the shear layer of the separation bubble. Reattachment generally occurs at the transition start. At Re=50,000 the separation bubble does not close before the trailing edge of the modeled airfoil. At higher Re, transition moves upstream, and the boundary layer reattaches. With high free-stream turbulence levels, transition appears to occur in a bypass mode, similar to that in attached boundary layers. Transition moves upstream, resulting in shorter separation regions. At Re above 200,000, transition begins before separation. Mean velocity, turbulence, and intermittency profiles are presented.
Reference31 articles.
1. Hourmouziadis, J., 1989, “Aerodynamic Design of Low Pressure Turbines,” AGARD Lecture Series 167.
2. Mayle, R. E.
, 1991, “The Role of Laminar–Turbulent Transition in Gas Turbine Engines,” ASME J. Turbomach., 113, pp. 509–537.
3. Sharma, O. P., Ni, R. H., and Tanrikut, S., 1994, “Unsteady Flow in Turbines,” AGARD-LS-195, Paper No. 5.
4. Morkovin, M. V., 1978, “Instability, Transition to Turbulence and Predictability,” NATO AGARDograph No. 236.
5. Volino, R. J., and Simon, T. W., 1995, “Bypass Transition in Boundary Layers Including Curvature and Favorable Pressure Gradient Effects,” ASME J. Turbomach., 117, pp. 166–174.
Cited by
78 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献