Anti-PIV type 2, 3 Polyclonal antibody

The authors have presented results of an experimental investigation into the velocity field in a turbulent boundary layer behind a thin (0.00045 m) three-dimensional plate. The chord of the plate (streamwise length) was equal to 0.55 delta (delta is the boundary-layer thickness), and its width, to 1.0 delta. The plate was installed at a zero angle of attack at the center of a water channel at a distance of 0.09 delta from the surface. Velocity-field measurements have been performed by the Particle Image Velocimetry method at the Reynolds number Re-h = 7750 calculated from the channel half-width and the velocity at the center of the channel. It has been shown that the average velocity increased in a logarithmic region of the boundary layer at a distance of its three thicknesses behind the plate. Longitudinal-velocity pulsations decreased in the buffer region of the boundary layer, but grew in the logarithmic region. Vertical pulsations only decreased to a distance of 0.8 delta behind the plate, but downstream they were higher than in an unperturbed boundary layer. The high resolution of the velocity field (50.10(-6) m) has made it possible to determine shear stresses on the wall from the velocity gradient in a laminar sublayer. Shear stresses on the surface behind the plate decreased in the interval where a growth in the average velocity in the logarithmic region was noted. Maximum reduction in the shear stresses occurred at a distance of 1.8 delta and amounted to similar to 33%. The influence of edge effects was manifested in the less intense reduction on shear stresses in the shorter interval behind the plate.

The present work concentrates on the reconstruction of the time-resolved turbulent flows from probe signals and low sampling rate flow fields using linear stochastic estimation (LSE) and sequential data assimilation (DA). The separated and reattached flow over a blunt plate is used as the benchmark configuration. Experimental data are acquired with a microphone array (34 probes) installed on the plate surface to capture the pressure fluctuation at a sampling rate 1000 Hz, and with planar particle image velocimetry (PIV) measuring the two-dimensional two-component (2D2C) velocity fields synchronized with the microphones at 1 Hz. LSE is conducted first to estimate the raw temporal sequence of the flow field from PIV and microphone data. This temporal sequence then serves as the observations for the DA process based on continuous adjoint formulation for the flow field correction and pressure determination. The LSE results show that an appropriate size of proper orthogonal decomposition (POD) database should be evaluated considering the combined error induced by the truncation of the mapping function M, the size of the POD database, and the scaling of the model coefficient for the compensation of M truncation. Subsequently, the LSE reconstructions using the POD database of size N-t = 100 are employed as the observations in the DA process. The mean flow field is recovered quite well, while the normal Reynolds stress also has a significant improvement compared to large-eddy simulation. The temporal variation of the LSE reconstruction is significantly improved, and the resultant fluctuating pressure coefficient distribution agrees reasonably well with the microphone measurement.