Showing papers by "H. Bijl published in 2003"

Model error estimation in global functionals based on adjoint formulation

Abstract: In aerospace engineering Computational Fluid Dynamics (CFD) is often ap- plied to obtain values for quantities of interest which are global functionals of the solution of the CFD computation. For instance the lift, drag and control- and stability derivatives necessary in ight simulation models for ight simulators. In the application for ight simulation models it would require years of performing CFD computations to generate such a model. One way of reducing the computational time is to apply a mathemati- cal uid ow model which is suciently sophisticated to compute the quantity of interest with the required accuracy. The ultimate goal is to apply a model adaptive strategy which adapts the 'coarse' mathematical model (in parts of the computational domain) to a more sophisticated model when the modelling error in the quantity of interest is too large. This approach requires the application of adjoint techniques to couple the local modelling errors to the global quantity of interest. In this paper we study global modelling error estimation in a quantity of interest by a dual weighted residual method, as described in (2), to a simple linear, scalar model problem of which the analytical solutions are known exactly.

Efficient partitioned solution methods for the computation of fluid-structure interactions

Abstract: Publisher Summary This chapter reviews the efficient partitioned solution methods for fluid–structure interactions. Main ingredients of the solution method are higher order time integration schemes and a monolithic coarse grid correction. The partitioned approach is used for the coupling of the fluid and structure where their partitions are processed by different programs and are spatially and temporally discretized by methods tailored to the underlying mathematical models and geometrical complexity. For the partitioned iteration, convergence acceleration by monolithic coarse grid correction is restricted to a simplified test problem without a moving mesh: the classical one-dimensional linear piston. For an amplitude error of 1% higher for the linear piston problem, two versions of coupling are used: Gauss–Seidel type partitioned iteration of fully implicit methods and implicit integration of the fluid and explicit for the structure.

Comparison of two adjoint equation approaches with respect to boundary-condition treatment for the quasi-1D Euler equations

Abstract: For computation of nonlinear aeroelastic problems, an efficient error estimation and grid adaptation algorithm is highly desirable, but traditional error estimation or grid adaptation do not suffice, since they are insufficiently related to relevant engineering variables and are incapable of significantly reducing the computing time. The dual formulation however, can be used as an a-posteriori error estimation in the quantity of interest. However, derivation of the dual problem, especially the accompanying boundary conditions, is not a trivial task. This document compares a discrete and analytical ad joint equation method with respect to boundary-condition treatments applied on the quasi-1D Euler equations. Flux evaluation of the primal problem is do ne by a Linearised Godunov scheme. For our future goal, solving ftuid-structure problems, the discrete approach seems preferable.