Dresden 2014 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 37: Fluid Dynamics and Turbulence

DY 37.5: Vortrag

Donnerstag, 3. April 2014, 16:00–16:15, ZEU 146

Generation of turbulence with an active grid — •Lars Kröger, Nico Reinke, Gerd Gülker, and Joachim Peinke — ForWind, Center for Wind Energy Research, University of Oldenburg, D-26129 Oldenburg, Germany

Turbulent fluid flows are omnipresent in our everyday life. Especially turbulence in the atmospheric boundary layer is a very important topic for wind energy research. As experiments in nature are somewhat limited and could mostly not take place under reproducible circumstances, wind tunnel measurements are necessary. Placing grids behind the wind tunnel nozzle is a common way to generate turbulence in a laboratory experiment. So called active grid consisting of horizontal and vertical oscillating rods with flaps are used in some investigations providing an improved option to generate dynamically driven turbulence with a wide range of statistical behaviour. Reproducible and statistical well defined turbulence could be generated with defined excitation protocols of the active grid flaps. In our experiments, we are using active grids in two wind tunnels with different dimensions. In this presentation hotwire and PIV measurements of the grid wakes are presented in order to investigate the scaling ability of the turbulent flow. For this, the decaying turbulence of different excitation protocols of the two mentioned grids is characterized by measurements of the velocity, the power spectra and turbulence intensity.