An integrated measurement approach for the determination of the aerodynamic loads and structural motion for unsteady airfoils

The structural motion and unsteady aerodynamic loads of a pitching airfoil model that features an actuated trailing edge flap are determined experimentally using a single measurement and data processing system. This integrated approach provides an alternative to the coordinated use of multiple measurement systems for simultaneous position and flow field measurements in large-scale fluid-structure interaction experiments. The measurements in this study are performed with a robotic PIV system using Lagrangian particle tracking. Flow field measurements are obtained by seeding the flow with helium-filled soap bubbles, while the structural measurements are performed by tracking fiducial markers on the model surface. The unsteady position and flap deflection of the airfoil model are determined from the marker tracking data by fitting a rigid body model, that accounts for the motion degrees of freedom of the airfoil model, to the measurements. For the determination of the unsteady aerodynamic loads (lift and pitching moment) from the flow field measurements, two different approaches are evaluated, that are both based on unsteady potential flow and thin airfoil theory. These methods facilitate an efficient non-intrusive load determination on unsteady airfoils and produce results that are in good agreement with reference measurements from pressure transducers. (c) 2021 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Automated summary

An experimental method is used to determine the structural motion and unsteady aerodynamic loads of a pitching airfoil model, utilizing a single measurement and data processing system, which simplifies the process compared to using multiple systems simultaneously. Flow field measurements are conducted using a robotic PIV system and Lagrangian particle tracking with helium-filled soap bubbles, while structural measurements are achieved through fiducial marker tracking on the model surface. The determination of unsteady aerodynamic loads is based on two approaches using potential flow and thin airfoil theory, resulting in efficient load determination on unsteady airfoils with good agreement to reference measurements.