Computational Fluid Dynamics

Computational fluid dynamic methods apply the power of modern digital comput­ers to the problem of estimating stability and control from drawings at the design stage. Finite-element methods are one form of computational fluid dynamics. The great power of computational fluid dynamics is its ability to deal with arbitrarily shaped airplanes. Even advanced handbook methods such as the DATCOM can fail to represent a truly unusual design.

Computational aerodynamics are not exactly new, in that approximate methods for the calculation of aerodynamic loads on arbitrarily shaped wings in subsonic flow have been available for many years. However, before the advent of the digital computer the number of unknowns in the mathematical solutions for the flow had to be kept low. As pointed out by Sven G. Hedman, one of the inventors of the modern vortex lattice method, the number of unknowns was kept low in the predigital computer era by assumptions for the wing’s chordwise and spanwise load distributions. That early work was done by Falkner (1943), who also coined the term vortex lattice theory.

Assumed load distributions are not needed for modern finite-element methods using the digital computer. The earliest applications of modern finite-element methods to the calculation of aerodynamic forces and moments appears to have been made at the Boeing Company in about 1960. This was the discrete loading vortex lattice method, developed independently by Sven G. Hedman and P E. Rubbert. The development of the vortex lattice method is a classic case of research people all over the world contributing steps to a remarkably useful result. For a detailed history, see De Young (1976).