Measurement and modeling of turbulent boundary layer excitation for naval and aeronautial applications

The correct characterization of wall pressure fluctuations (WPF) and of the response of an elastic structure subjected to turbulent boundary layer (TBL) represents one of the most challenging problems in the fluid structure interaction field. This kind of excitation for an elastic structure is encountered on a number of different engineering applications: in naval field WPF acting along the ship hull impinge on comfort on board high speed vessels and they are also responsible for strong vibrations of the sonar dome, which can degrade the correct functioning of the sensors mounted inside the dome itself. Moreover, the sound pressure levels produced by TBL load acting along the aircraft fuselage can be intense enough to result in an unacceptable cabin noise and can cause a reduction of the lifetime of fuselage panels due to structural fatigue. The study of WPF induced by TBL load in the naval and aeronautical fields are characterized by important differences in terms of both flow and structural characteristics, which provide highly different dynamical responses of a typical naval and aeronautic panel. Nevertheless, the characterization of the TBL load using model scale tests of a ship and an aircraft or sections of them have also strong similarities and for a great number of problems can be analysed using parallel experimental approaches in towing tanks, water channels and wind tunnels. The base of this approach is given by the identification of the most appropriate scaling laws for wall pressure fluctuation spectra and spatial models in the frequency domain, which allow to obtain in principle the full scale spectra from the sole knowledge of few mean flow parameters. Unfortunately, these models are based on very restrictive hypotheses on the nature of the flow and the structure, basically canonical flat boundary layer. Aim of this work is to show how some of the typical perturbations from the canonical flat plate boundary layer, encountered when studying a real structure in naval and aeronautical fields, can interfere in the modelling of this load and to show possible solutions to these specific problems. To examine these features for complex boundary layer, the results of three different experimental campaigns performed at CNR-INSEAN towing tank and CIRA PT-1 transonic wind tunnel are here discussed.