Pressure fluctuations from large-scale PIV over a serrated trailing edge

Abstract: Measurements of distributed surface pressure fluctuations over trailing-edge serrations at a Reynolds number Re _θ = 4900 are performed with time-resolved 3D particle imaging velocimetry using helium filled soap bubbles as flow tracers. The sparse velocity vector field obtained with Lagrangian particle tracking is densely reconstructed using VIC+, a data assimilation technique based on the vortex-in-cell method. The instantaneous pressure distribution is inferred by invoking the momentum equation. Experiments are performed first over a flat plate, as assessment of the technique, where the properties of the convecting turbulent boundary layer are assessed and surface pressure fluctuations are validated against synchronous surface microphone measurements. The analysis of the flow over the trailing-edge serration focuses on the characterization of the spatial distribution and spectral coherence of surface pressure fluctuations, i.e. the flow features responsible for the acoustic scattering. Present results indicate that the measurement technique is suited to describe the spatio-temporal development of the pressure fluctuations over the serration surface at the proposed scale of the experiments. Graphic abstract: [Figure not available: see fulltext.].