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Experimental study of transitional flow behavior in a simulated low pressure turbine
| Content Provider | NASA Technical Reports Server (NTRS) |
|---|---|
| Author | Sohn, Ki Hyeon DeWitt, Kenneth J. |
| Copyright Year | 1998 |
| Description | A detailed investigation of the flow physics occurring on the suction side of a simulated Low Pressure Turbine (LPT) blade was performed. A contoured upper wall was designed to simulate the pressure distribution of an actual LPT airfoil onto a flat lower plate. The experiments were carried out for the Reynolds numbers of 35,000, 70,000, 100,000 and 250,000 with four levels of freestream turbulence ranging from 1% to 4%. For the three lower Reynolds numbers, the boundary layer on the flat plate was separated and formed a bubble. The size of laminar separation bubble was measured to be inversely proportional to the freestream turbulence levels and Reynolds numbers. However, no separation was observed for the Re = 250,000 case. The transition on a separated flow was found to proceed through the formation of turbulent spots in the free shear layer as evidenced in the intermittency profiles for Re = 35,000, 70,000 and 100,000. Spectral data show no evidence of Kelvin-Helmholtz or Tollmien-Schlichting instability waves in the free shear layer over a separation bubble (bypass transition). However, the flow visualization revealed the large vortex structures just outside of the bubble and their development to turbulent flow for Re = 50,000, which is similar to that in the free shear layer (separated-flow transition). Therefore, it is fair to say that the bypass and separated-flow transition modes coexist in the transitional flows over the separation bubble for certain conditions. Transition onset and end locations and length determined from intermittency profiles decrease as Reynolds number and freestream turbulence levels increase. |
| File Size | 5976303 |
| Page Count | 216 |
| File Format | |
| Alternate Webpage(s) | http://archive.org/details/NASA_NTRS_Archive_19980218173 |
| Archival Resource Key | ark:/13960/t9n34sk2t |
| Language | English |
| Publisher Date | 1998-08-01 |
| Access Restriction | Open |
| Subject Keyword | Fluid Mechanics And Heat Transfer Turbulent Flow Turbine Blades Flat Plates Reynolds Number Flow Measurement Pressure Distribution Flow Characteristics Computerized Simulation Transition Flow Intermittency Shear Layers Bubbles Emission Spectra Vortices Low Pressure Flow Visualization Boundary Layer Transition Separated Flow Bypasses Ntrs Nasa Technical Reports Server (ntrs) Nasa Technical Reports Server Aerodynamics Aircraft Aerospace Engineering Aerospace Aeronautic Space Science |
| Content Type | Text |
| Resource Type | Technical Report |
