ESDU Engineer

Full-Potential (FP) Method For Three-Dimensional Wings And Wing-Body Combinations - Inviscid Flow

ESDU 02013 PART 1: Principles and results (ESDU Data Item 02013)

ESDU 02014 PART 2: Use of FP and related programs (ESDU Data Item 02014)

These Items are the first two in a series dealing with the full-potential method, FP, and the later developments of FP.

FP is a CFD (computational fluid dynamics) method coded in Fortran for calculating the flow field and aerodynamic forces of a wing or wing-body combination in a subsonic stream, including the effects of shock waves. It utilises a numerical relaxation scheme to solve finite-difference forms of the full non-linear velocity-potential equation for the inviscid flow around the three-dimensional geometry. The method utilises three levels of grid density. As presented, the finest grid may have up to 160 mesh intervals around a wing section, 38 intervals in the spanwise direction, and 22 intervals normal to the sections.

FP was developed both at ARA Bedford and RAE (now QinetiQ, Farnborough) and is made available under an agreement with QinetiQ. Used originally on mainframe computers, FP has provided valuable data in the aerodynamic design of a number of aircraft. Recent advances in computers have made it possible to perform runs of FP on a PC within a few minutes.

For high Reynolds number conditions, such as those encountered in flight of most aircraft, FP may be used to study the flows of a wide range of wing-alone and wing-body combinations, in each case for a range of conditions - including those corresponding to the cruise. Shock onset conditions and conditions with weak shocks are among those likely to be successfully dealt with, but the large viscous effects occurring with flows with strong shocks can be expected to make the FP method less useful for direct prediction of such cases.

FP may be readily used to assess large numbers of configurations with differing geometries within a reasonable time. It thus provides an invaluable aid in the aerodynamic design process.

Mike Freestone is the Senior Engineer responsible for the Transonic Aerodynamics Series and he can be contacted at mfre@esdu.com.