壁面湍流边界层压力起伏的高速层析PIV（Tomo-PIV）和直接数值模拟（DNS）的比较研究

In the present study it is attempted to use the 3D time-resolved velocity field measurements obtained by employing a high-speed tomographic PIV system on a flat plate turbulent boundary layer at Reθ=730. The main objective of the study is the estimation of the wall pressure coherence function for the prediction of aeroacoustic noise radiated by boundary layers and trailing edge flows. The reconstruction of the pressure field from velocity field measurements follows the approach of de Kat and van Oudheusden (2012), whereby the Poisson equation is integrated over the measurement volume in 3D. Due to restriction on the extent of the measurement volume, uniform pressure is applied as boundary condition on stream- and spanwise faces. A direct numerical simulation of the boundary layer at a similar Reynolds number is performed in order to produce reference data for the velocity statistics and for the properties of the spectral fluctuations. The tomographic data agree very well with DNS as far as mean and fluctuating velocity components are concerned. Velocity field results are compared to 2C-PIV and the DNS solution and a collapse of the data is demonstrated. An additional reference measurement is introduced in order to validate the procedure of pressure determination from time-resolved tomographic PIV. Time series of pressure and the scaled power spectral density at a single point are compared to the DNS solution and results available from literature and good agreement is found. The correlation coefficient with respect to pinhole microphone measurements reaches a maximum value above 50% for data band-pass filtered between 250Hz and 3.5kHz. Finally, the coherence of the pressure fluctuations and the resulting spanwise coherence length are computed compared.