Comparison of Finite Difference Calculations of a Large Region of Recirculating Flow Near an Airfoil Trailing Edge,
IMPERIAL COLL OF SCIENCE AND TECHNOLOGY LONDON (ENGLAND) DEPT OF MECHANICAL ENGINEERING
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Calculations are presented for a turbulent boundary layer which separates upstream of a sharp trailing edge and results in a large region of recirculating flow and a curved downstream wake. The solutions obtained from two procedures that solve finite difference equations formulated with hybrid combinations fo upwind central and bounded skew upwind central difference approximations for convective terms, are compared. Numerical error was smaller, and accordingly less false diffusion was apparent, in the bounded skew calculations although there was no significant improvement in the agreement with experiment. Agreement between measured and calculated values of the lift coefficient was within 3 per cent and required representation of momentum transport and pressure gradient normal to the surface, but the measured drag coefficient was less than 80 per cent of that obtained in both calculations. Deficiencies are attributable, in part, to turbulence-model assumptions which do not represent the effects of stabilizing and destabilizing streamline curvature and the complex interaction of the backflow, pressure side and curved suction-side boundary layers in the vicinity of the rear stagnation point downstream of the trailing edge.