Berlin 2008 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe

DY: Fachverband Dynamik und Statistische Physik

DY 26: Fluid dynamics II

DY 26.4: Vortrag

Donnerstag, 28. Februar 2008, 15:00–15:15, MA 001

A new method for measuring lift forces acting on an airfoil under dynamic conditions — •Gerrit Wolken-Möhlmann and Joachim Peinke — Institute of Physics, University of Oldenburg, Germany

Wind turbines operate in a turbulent atmospheric boundary layer and are exposed to strong wind fluctuations in time and space. This can induce the dynamic stall, a phenomenon that causes extra loads.

Dynamic stall occurs under fast changes in the angle of attack (AoA) and was determined in detail in helicopter research. But in contrast to helicopter aerodynamics, the changes in the AoA of wind turbine airfoils are in general non-sinusoidal, and thus it seems to be difficult to use these measurements and models. Our goal is to acquire lift data under conditions more comparable to real wind turbines, including non-periodic changes in the AoA.

For this purpose a closed test section for our wind tunnel was built. An airfoil with a chord length of 0.2m will be rotated by a stepping motor with angular velocities of up to 300^∘/s. With a maximum wind velocity of 50m/s, Reynolds numbers of Re=700 000 can be realized. The lift force is determined by the counter forces acting on the wind tunnel walls. These are measured by two lines of 40 pressure sensors with sampling rates up to 2kHz.

The results show distinct dynamic stall characteristics. Further experiments with different parameters and foils will give a better insight in dynamic stall and a verification and improvement of existing models.