Sm. Guo et al., COMPUTATIONAL PREDICTION OF HEAT-TRANSFER TO GAS-TURBINE NOZZLE GUIDEVANES WITH ROUGHENED SURFACES, Journal of turbomachinery, 120(2), 1998, pp. 343-350
The local Mach number and heat transfer coefficient over the aerofoil
surfaces and endwalls of a transonic gas turbine nozzle guide vane hav
e been calculated. The computations were performed by solving the time
-averaged Navier-Stokes equations using a fully three-dimensional comp
utational code (CFDS), which is well established at Rolls-Royce. A mod
el to predict the effects of roughness has been incorporated into CFDS
and heat transfer levels have been calculated for both hydraulically
smooth and transitionally rough surfaces. The roughness influences the
calculations in two ways; first the mixing length at a certain height
above the surface is increased; second the wall function used to reco
ncile the wall condition with the first grid point above the wall is a
lso altered. The first involves a relatively straightforward shift of
the origin in the van driest damping function description, the second
requires an integration of the momentum equation across the wall layer
. A similar treatment applies to the energy equation. The calculations
are compared with experimental contours of heat transfer coefficient
obtained using both thin-film gages and the transient liquid crystal t
echnique. Measurements were performed using both hydraulically smooth
and roughened surfaces, and at engine-respresentative Mach and Reynold
s numbers. The heat transfer results are discussed and interpreted in
terms of surface-shear flow visualization using oil and dye techniques
.