Grid-size reduction in flow calculations on infinite domains by higher-order far-field asymptotics in numerical boundary conditions

An error analysis is presented of the numerical calculation of the steady flow on an infinite domain around a given airfoil by a domain-splitting (= zonal) method. This method combines a fully-conservative finite-difference approximation on a finite domain around the airfoil with an approximate asymptotic solution outside this finite domain. The errors are analyzed as a function of the accuracy of the approximate asymptotic expansion, of the distance to the airfoil of the far-field boundary of the finite domain and of the mesh size. The numerical experiments show that, for a given desired accuracy level, large reduction in grid sizes are possible, if the usual far-field asymptotic approximation (uniform flow plus first-order perturbation by a circulation vortex at infinity) is augmented by only a few extra terms in the approximate asymptotic far-field solution. In this way, considerable numerical efficiency improvements can be realized. It is expected that this conclusion can be generalized to many other applications where computations on infinite domains are performed

Static and dynamic numerical simulations of a generic UCAV configuration with and without control devices

A contribution for the assessment of the static and dynamic aerodynamic behavior of a generic UCAV configuration with control devices using CFD methods is given. For the CFD simulations the unstructured grid based DLR TAU-Code and the structured grid based NLR solver ENSOLV are used. The numerical methods are verified by experimental wind tunnel data. The current investigations should provide a contribution to assess the prediction capability of control device effectiveness using CFD methods. The presented computational results for the assessment will be validated by dedicated experimental data. Furthermore, it should support the understanding of the flow physics around the trailing edge control devices of highly swept configurations with a vortex dominated flow field. Design requirements should be able draw by analyzing the interaction between the vortical flow and the control devices. The present work is part of the NATO STO/AVT Task Group AVT-201 on Stability and Control prediction method