Jens-Dominik Müller

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We report on field trials using CoMP transmission in the downlink of a mobile radio network. Two new features enable over-the-air CoMP transmission from physically separated base stations and terminals. These are distributed synchronization and a fast virtual local area network. Using VLAN tags, terminals feed back the multi-cell channel state information(More)
A multigrid method has been developed for the Euler and Navier-Stokes equations on unstructured hybrid grids in two and three dimensions. The coarse grids are automatically generated from the nest grid through element collapsing. This has been used in preference to a previous edge-collapsing technique to preserve as much structure as possible within(More)
The objectives of this paper are the description of azimuthal instability modes found in annular combustion chambers using two numerical tools: (1) Large Eddy Simulation (LES) methods and (2) acoustic solvers. These strong combustion instabilities are difficult to study experimentally and the present study is based on a LES of a full aeronautical combustion(More)
The main approaches of discretising the viscous operator of fluid flow on hybrid meshes are analysed for accuracy, consistence, monotonicity and sensitivity to mesh quality. As none of these approaches is fully satisfactory, a novel method using an approximated finite element approach is presented and analysed. The methods are compared for the linear heat(More)
A new implicit time-stepping scheme which uses Runge-Kutta time-stepping and Krylov methods as a smoother inside FAS-cycle multigrid acceleration is proposed to stabilise the flow solver and its discrete adjoint counterpart. The algorithm can fully converge the discrete adjoint solver in a wide range of cases where conventional point-implicit methods fail(More)
Sensitivity analysis is a research area of increasing interest within CFD. Recent developments in Automatic Differentiation software (AD) make the discrete adjoint methods particularly attractive. We outline the theory of adjoint sensitivities and discuss how to use AD to derive adjoint versions from CFD codes. In particular we review the properties of the(More)
Algorithmic differentiation (AD) by source-transformation is an established method for computing derivatives of computational algorithms. Static dataflow analysis is commonly used by AD tools to determine the set of <i>active</i> variables, that is, variables that are influenced by the program input in a differentiable way and have a differentiable(More)
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