Coupled measurements of fluid velocity using Tomo-PIV and wing deformation for the investigation of fluid-structure
This work aims at performing fluid and structure coupled measurements on a rigid and a flexible wing. The investigated experimental configuration corresponds to a NACA0015 wing placed at high angle of attack in a water tunnel, reproducing the flow around a foil or a simplified appendage at a Reynolds number of 105. The measurements carried out are volumetric Tomo-PIV and Stereo-PIV measurements associated to wing displacement measurements.
In order to improve the velocity measurements through thick windows and prepare a volumetric measurement of the wing displacement, a new camera model, combining an analytical model and a local discrete correction, has been implemented. These developments have been assessed on a numerical and an experimental case.
The measurements performed around a rigid wing are compared to DES (Detached Eddy Simulation) results and are used as a reference case to analyze the flexible case, which is used to examine the fluid-structure interaction.
The expected flow topology at such high angle of attack, has been observed with the formation of strong shear layers originating from the leading edge and the trailing edge, associated to a wide recirculation bubble. The development of a tip vortex has also been observed. The displacement of the wing exhibits mainly bending with no measurable torsion. Areas of coupling between the fluid and the structure have been identified using temporal correlations between the wing displacement and the flow velocity. Early results tend to show that the structure bending is forced by the flow dynamics but no feedback has been observed, probably due to the low amplitude of the structure dynamical displacements.
These coupled volumetric measurements, performed for the fluid structure interaction investigation, are the first ones carried out in the institute and open new capabilities for applications using flexible structures, such as flexible water turbine blades.