Finite Element Analysis of Transonic Flow.
Abstract
The finite element technique is applied to steady incompressible, subsonic and transonic flow with the end objective being the analysis of unsteady transonic flow. A triangular cubic element is used and the Galerkin method of weighted residuals is adapted to control the error. The formulation is based on the small disturbance but nonlinear transonic equation for inviscid compressible flow. Full potential formulations with small disturbance assumptions are also investigated. The governing equations are cast into the Poisson type for which finite element analogs are constructed, and the solution is then obtained by iterative procedures. Boundary conditions involving the normal derivative of the unknown functions are conveniently cast into boundary integrals and added to the right-hand side of the equations. In the case where more than two unknown parameters are related, such as those along the branch cut, Lagrangian multipliers are used to introduce these constraints and a special equation solver is developed for these computations. Techniques are developed for analyzing lifting flow under free flight conditions with general provisions for surface tangency, wake and far field boundary conditions. This generality allows for computation of combinations of internal axd external flow (as an airfoil in a wind tunnel), as well as free flight, about arbitrary geometry. Unsteady transonic flow calculations are also presented for a NACA 64 A006 with an oscillating 25% chord control surface.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 01, 1974
- Accession Number
- AD0921922
Entities
People
- M. R. Brashears
- S. T. K. Chan
Organizations
- Lockheed Martin Missiles and Space