Prof. Stefan Becker, Christoph Scheit, Lehrstuhl für Prozessmaschinen und Anlagentechnik, Universität Erlangen-Nürnberg

Title: Aeroacoustics of Small Vertical Wind Turbines: Simulation and Experiment

Abstract:

The contents of the presentation is to validate two different numerical methods for noise prediction of the H-Darrieus wind turbine using a complementary approach consisting of experimental measurements and numerical simulations. The acoustic measurements of a model scale rotor were performed in an anechoic wind tunnel. This data is the basis for the validation of the computational aeroacoustic simulations. Thereby, we have applied two different numerical schemes for noise prediction using hybrid methods. As usual in hybrid aeroacoustic approaches, flow field and acoustic calculations are carried out in separate software packages. For both schemes the time-dependent turbulent flow field is solved with SAS. In the first scheme the acoustic source terms are computed according to Lighthill’s acoustic analogy which gives source terms located on the original CFD grid. The second scheme uses the Ffowcs Williams-Hawkings (FW-H) method which is based on a free field Green’s function. The scheme uses a porous integration surface and implements an advanced time formulation. Both methodologies are compared with experimental data.

Title: Parallelization and Optimization of Fastest-3D for Multicore Systems

Abstract:

In this case study, we demonstrate in detail how the performance, scalability, and flexibility of an existing, vector computer based CFD Code, namely Fastest-3D, could be improved to make it compatible with modern, highly parallel cluster systems. First, a node-level performance analysis is carried out in order to pinpoint the main bottlenecks and identify sweet spots for energy-efficient execution. In addition, a single-precision version of the solver for the linear equation system arising from the discretization of the governing equations is devised, which significantly increases the single-core performance. Then the communication mechanisms are analyzed and a new communication strategy based on non-blocking calls is implemented. Performance results with the revised version show significantly increased single-node performance and considerably improved communication patterns along with much better parallel scalability.