Schutz und Trocknung

Ohne Zusammenfassung     

Buchbesprechungen

Ohne Zusammenfassung     

Simulation of vorticity dominated flows using a hybrid approach. II: Numerical method

A family of numerical methods for the solution of the incompressible Navier–Stokes equations in cylindrical coordinates is developed. The formulation for hybrid spectral-finite difference discretizations in domains with cylindrical boundaries presented in Kollman, in press [Kollmann W, Simulation of vorticity dominated flows using a hybrid approach: I formulation, in press] forms the basis of the solvers. The solution methods use the Fourier-spectral approach for the azimuthal and a set of finite-difference operators for the radial and axial directions. The convective terms are discretized with a linear combination of upwind-biased and central difference operators applied to the non-conservative and conservative formulations, respectively. All other spatial derivatives are discretized with central operators. The time integration is specified as a minimum storage, state space, fourth order Runge–Kutta method. The convergence of the solvers as the formal accuracy of the finite-difference operators varies is tested for an axi-symmetric flow for fixed discretization and time integrator. The results show satisfactory convergence with respect to order of accuracy and the convective operators.     

Buchbesprechungen

Ohne Zusammenfassung     

A robust finite element solver for a multiharmonic parabolic optimal control problem

This paper presents the analysis of a distributed parabolic optimal control problem in a multiharmonic setting. In particular, the desired state is assumed to be multiharmonic. After eliminating the control from the optimality system, we arrive at the reduced optimality system for the state and the co-state that is nothing but a coupled system of a forward and a backward parabolic partial differential equation. Due to the linearity, the state and the co-state are multiharmonic as well. We discretize the Fourier coefficients by the finite element method. This leads to a large system of algebraic equations, which fortunately decouples into smaller systems each of them defining the cosine and sine Fourier coefficients for the state and co-state with respect to a single frequency. For these smaller systems, we construct preconditioners resulting in a fast converging minimal residual solver with a parameter-independent convergence rate. All these systems can be solved totally in parallel.     

Strategic homogenisation of energy efficiency measures: an approach to improve the efficiency and reduce the costs of the quantification of energy savings

With the ongoing efforts on the European level to promote energy efficiency, the need for the development of harmonised evaluation criteria for energy efficiency measures arises. Such criteria will allow extensive comparisons of the success or failure of the implementation of energy efficiency measures throughout Europe and will support the development of a first–best strategy for the realisation of energy savings targets in Europe. Two fundamental evaluation possibilities exist: bottom-up and top-down quantifications of energy savings. Bottom-up calculations give a more detailed view of the impact of energy efficiency measures but are much more costly and time consuming than top-down calculations. In our opinion, this effort can be reduced without losing precision in the savings calculations by the homogenisation of these energy efficiency measures. In this paper, we develop a framework specifying how such a homogenisation could look.     

Buchbesprechungen

Ohne Zusammenfassung