Heat Transfer and Flow Structure in End-Wall Boundary Layers.
Final rept. Oct 93-May 97,
LEHIGH UNIV BETHLEHEM PA DEPT OF MECHANICAL ENGINEERING AND MECHANICS
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Analytical, numerical, and experimental stndies have documented the flow development and surface heat transfer for several three dimensional end-wall flows, and indicate the presence of highly unsteady vortex formation within the end-wall boundary layer. This vortex formation process leads rapidly to the evolution of three dimensional separation effects which have a profound influence on the surface heat transfer. Analysis of the three dimensional behavior indicates the presence of persistent and strong interactions between the end-wall boundary layers on both the surface and the side-wall boundary layers of the obstacle. A detailed series of Navier-Stokes calculations have been carried out for a vortex-induced motion similar to that encountered in turbulent boundary layers. As the Reynolds number is increased, a new type of instability associated with surface layer separation was found which leads to brealmp of the surface layer. Experimentally, laminar approach flows always develop discrete, periodic necklace vortices in the junction region, whereas a turbulent approach yields a dominant necklace or horseshoe-shaped vortex that moves chaotically. Examinations of the complex fluidheat transfer processes using PIV and thermochiomic liquid crystals shows that these junction vortices undergo very strong surface interactions, which creates strongly focused eruptions of surface fluid these studies show a direct correlation between the eruptive processes and local regions of high heat transfer.
- Fluid Mechanics