WP2

This WP deals with the development and assessment of a new approach for pressure field reconstruction from PIV velocity measurements.

The innovative and accurate procedure to compute the pressure field from PIV velocity measurements was based on the uncoupling of the velocity and pressure fields in the incompressible Navier–Stokes equations which relies on exact integral conditions for the pressure. By means of the Glowinski and Pironneau method, a set of linear PDE problems for the unknown pressure field has been derived and its numerical solution has been implemented by the finite element method. The performance of the proposed method has also been compared with that provided by other methods. The comparison shows a remarkable smoothing of the velocity error, which allows the proposed method to be significantly more accurate than the other techniques proposed so far.
Thus, the proposed method has been applied to phase averaged PIV measurements of a challenging aeronautical problem as the oscillating airfoil. The comparison between the computed pressure distribution and available pressure measurements on the airfoil surface showed pretty encouraging results. The reconstructed pressure field presents the expected structures of the examined cases (e.g. separated flow and reattaching flow). A direct comparison between the results obtained with the present method and those computed by the Poisson method for the pressure-field reconstruction showed an overall better performance of the proposed method. The validation of the proposed methodology represents an outstanding output of the present project compared to the state-of-the-art.

The PIV technique was then applied to the actual test-rig of the main rotor model in the large wind tunnel of Politecnico di Milano. A system to light the blade section both from up and down was designed, built and installed in the wind tunnel. A new set of passive blade (with interchangeable fixed Gurney flaps) was designed, manufactured, checked and finally used for the first series of tests that was at the same time the validation of the PIV system and the first test campaign of WP3.

The PIV system to light from the top (left) and bottom (right

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• Results: pressure computation from PIV measurements