Certification of a CFD Code for High-Speed Civil Transport Design Optimization

13th Aerospace Sciences Meeting and Exhibit
15-18 January 1996
Reno, Nevada

Duane L. Knill, Vladimir Balabanov, Bernard Grossman,
William H. Mason, and Raphael T. Haftka

Abstract

An investigation of the aerodynamic modeling requirements for HSCT design has been made. Studies have been performed to determine the effects of including Euler/Navier-Stokes calculations for the supersonic aerodynamic performance and structural loading of HSCT designs. Accuracy, computational effort, and ease of implementation are some of the considerations which are addressed. We quantify the increase in accuracy of the CFD calculations over linear supersonic methods through comparison with experimental data. As expected, it was found that the Euler and parabolized Navier-Stokes solutions are more accurate than those from linear theory. For relatively thick bodies, significant increases in the accuracy of the zero-lift wave drag prediction can be obtained using CFD in place of slender body results. However for more slender bodies and wings like those for our HSCT designs, this improvement is drastically reduced. Investigation into the force and moment data for wings and wing-fuselages show several consistent patterns. For our HSCT wings, parabolized Navier-Stokes predictions on the viscous drag matched closely with those predicted from algebraic skin friction estimates. The linear supersonic theory results consistently overpredict the lift and underpredict the drag as compared to CFD. These drag differences have a large effect on the HSCT range calculations. Another significant difference between the CFD and linear supersonic theory results comes in the wing stresses calculated from the aerodynamic loads. The HSCT carries large amounts of fuel in its wings, and consequently has large inertia relief that cancels most of the bending moments due to aerodynamic loading. As a result, the wing bending stresses are very sensitive to the predicted location of the center of pressure. Relatively small differences in the predicted center of pressure location between Euler and linear theory resulted in significant differences in the wing bending stresses and the structural weights.

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knill@aoe.vt.edu