Page 30 - Computational Fluid Dynamics for Engineers

1.2 Prediction of the Maximum Lift Coefficient of Multielement Wings 15

Fig. 1.15. Paneled narrow-body transport.

(C L)n

TEST DATA
PRESSURE DIFFERENCE RULE

0 2 4 6 8 10 12 14 16 Fig. 1.16. Variation of maximum lift coeffi-
cient with Reynolds number based on mean
R.X10 - 6 aerodynamic chord, R a.

must be determined for flight in icing conditions and in roughness conditions.
The roughness can be caused by ice, frost, de-icing and anti-icing fluids used
prior to take-off, insect contamination, paint and surface irregularities and lead-
ing edge damage such as that produced by a hail-storm. Roughness on the wing
leading edge affects the stall characteristics of an aircraft and its performance.
The method is based on a combination of the Pressure Difference Rule [6],
using a three-dimensional panel method, with results of a two-dimensional inter-
active viscous-inviscid CFD procedure developed by Cebeci [5] briefly described
in Chapter 7. The code is able to predict aerodynamic performance of single and
multi element airfoils, including stall, with and without surface roughness, with
sweep effects, for steady flows. The code uses a Hess and Smith panel method,
which is an extension of the panel method discussed in Section 6.4, to calculate
the inviscid flow field with a simple Karman-Tsien compressibility correction
formula. A two-dimensional compressible boundary layer code operating in an