The turbulent wake of a surface-mounted square-based finite bluff bodies is of heuristic interest. Estimating and synchronizing the planar velocity field obtained from the independent two-dimensional measurement (Particle Image Velocimetry) allows for the reconstruction of the three-dimensional coherent part of velocity field over a volume. In principle, this three-dimensional reconstruction makes it possible to investigate the global dynamics of coherent motions in turbulent wakes as a fundamental step towards understanding the energy transfer between scales of motion and ultimately the generation of the Reynolds Stress field.
In this work, the effect of sensor location on sensor-based estimation of the coherent velocity field in the wake of a surface-mounted pyramid obstacle is considered. Three different pressure sensor arrangements studied in this work are: (i) 6-sensor arrangement with the sensors on the obstacle (ii) 4-sensor arrangement which sensors are located in the wake on the base plate and (iii) 10-sensor arrangement with all 10 sensors.
Based on the discussion and results provided, a new time lag τ_1 is introduced to account for the convective delay between velocity field and pressure data sensors on the obstacle. Next, large-scale coherent structures of the wakes are analysed in terms of two main topological features. It was found that accounting for mode-specific lag is a very effective strategy for increasing the reliability of the estimation. At the end, three-dimensional reconstruction of the vortex structure is presented. Comparison of different cases of these three sensor arrangements shows the importance of the sensors on the base.