Estimating the Full Pressure Field Immediately Downstream from a Propeller Using Stereoscopic PIV

Experimental flow-field pressure data has long been acquired by employing pitot probe arrays. These arrays have poor time-response capabilities rendering them inadequate for time-resolved or high-speed flow applications. They are also intrusive and can cause perturbations that disrupt the flow field. However, experimental data from velocity-based measurements, such as particle image velocimetry (PIV), can be combined with the governing flow equations to derive high-resolution and time-resolved pressure fields in a non-intrusive manner. A multi-plane stereo-PIV system was used to determine the unsteady pressure field across a plane of the wake of an isolated propeller of diameter 9.5 in that was rotating at 4860 RPM. The measurement plane was located 0.01 propeller diameters downstream of the propeller and the PIV measurements were synchronized with the propeller rotation to allow the pressure field to be phase-resolved, without requiring high frame rate acquisition. The time-varying pressure fields were also phase-averaged to allow direct comparison to traditional averaged pitot probe pressure data, with good agreement. The unsteady pressure data were also compared to time-varying data from a RANS simulation of the same propeller geometry with very good agreement.