A Grid Overlapping Scheme for Flowfield Computations About Multicomponent Configurations

An efficient grid interfacing zonal algorithm has been developed for computing the transonic flowfield about three-dimensional multicomponent configurations. The algorithm uses the full-potential formulation and the AF2 fully implicit approximate factorization scheme. The flowfield solution is computed using a component- adaptive grid approach in which separate grids are employed for the individual components in the multicom- ponent configuration, where each component grid is optimized for a particular geometry. The component grids are allowed to overlap, and flowfield information is transmitted from one grid to another through the overlap region. An overlapping grid scheme has been implemented for an isolated wing and a noninteracting wing/pylon/nacelle configuration . Numerical results show that the present algorithm is stable, accurate, and promises to be effective in computing the flowfield about complex configurations. ELIABLE and efficient three-dimensional transonic analysis methods are needed to make realistic and cost- effective predictions of aircraft aerodynamics. Early efforts to predict the transonic flowfield about aircraft multiple- component configurations are based on the transonic small- disturbance formulation.1-3 This allows the geometry of the configuration to be greatly simplified and the surface boundary condition to be applied on a mean approximate surface. Accurate prediction of such flowfields, however, requires the use of the full-potential formulation and the generation of a suitable surf ace-fitted grid. Because each aircraft component (wing, nacelle, fuselage) requires, in general, a grid system that is usually incompatible with the grid systems of the other components, the generation of a single surface-fitted grid for the entire configuration is a difficult task. In such a global grid, control of grid point distribution, skewness, and clustering will be difficult to achieve. Efforts to predict the flowfield about a complete aircraft configuration using a single-grid approach have been made recently by Yu.4 In the present paper the alternate approach of using a component adaptive grid scheme is investigated. The basic idea of this approach is to develop a separate grird for each component of a complex configuration where each individual grid is optimized for a particular component. The flow solver for each component employs the AF2 fully implicit ap- proximate factorization scheme.5 Earlier studies in two dimensions showed that by allowing the component grids to overlap, fast convergence can be achieved.6 This approach has been generalized herein to three dimensions, where an overlapped grid scheme has been im- plemented for an isolated wing and a wing/pylon/nac elle configuration. The application of an embedded grid scheme to an isolated wing geometry was performed primarily as a proof-of- concept study to verify the grid interfacing logic in three dimensions and to determine if single-grid results could be replicated. The application to the wing/pylon/nacelle con- figuration represents a more realistic use of the grid em- bedding technique. The full interacting algorithm has been