Coherent Structure Modeling of Viscous Sublayer Turbulence for Incompressible Flow with Heat Transfer.
STANFORD UNIV CA DEPT OF AERONAUTICS AND ASTRONAUTICS
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A Navier-Stokes computational model of the time-developement dynamics and heat transfer in a viscous sublayer had been developed. The main research objective is to determine the variation of turbulent Prandtl number across the sublayer. Experiments have been unable to define this variation, and existing theories differ greatly. The computational code uses prescribed temperature and velocity boundary conditions at the outer edge of the sublayer. Numerical computations of turbulent Prandtl number have been made for molecular Prandtl numbers ranging from 0.7 to 6 with zero pressure gradient, and for adverse, zero, and favorable pressure gradient with a Prandtl number of 0.7. The results show a strong effect of molecular Prandtl number on turbulent Prandtl number a very near the wall but only a relatively small effect of pressure gradient throughout the sublayer. For most practical computations of heat transfer, the simple assumption of the constant turbulent Prandtl number across the viscous sublayer appears adequate. Keywords Fluid mechanics Viscous sublayer Navier-Stokes equation Computational model.
- Fluid Mechanics