Comparative Study of Three Flow Diagnostic Techniques Applied to a Nearbody Flowfield

A comparative study of three Particle Image Diagnostic Techniques (PIDT\u27s) is performed while investigating the near-body flowfield of a gas turbine particulate sampling probe. Tests were conducted at small Fields Of View (FOV), 10.5 ~ 14.5 mm, and large Reynolds number (Re) (22,000, with respect to the 14.3 mm diameter of the probe). Particle Shadow Velocimetry (PSV), Volume Illuminated Forward Scatter Particle Image Velocimetry (VIFS-PIV) and Particle Image Velocimetry (PIV) experiments were conducted at the University of Dayton Low Speed Wind Tunnel (UD-LSWT). This research documents the challenges associated with the experimental setup of each method at the UD-LSWT, compares the results of the three methods and uses the best result to correlate the results from the numerical investigation conducted on the probe at US Air Force Research Laboratory (AFRL) Propulsion Directorate. PSV experiments showed that the size and density of the seed material used in the experiments were large resulting in a large Stokes number (≫1) and large response time (0.1 to 7.55 msec) compared to the characteristic time (13 μsec). Results from VIFS-PIV showed the scattering of light from out-of-plane particles. This scattered light was captured as a speckle image resulting in the loss of useful data limiting resolution to 32 pixels. PIV experiments provided results with better resolution (16 pixels). When comparing the data from the two PIV variants to the computational investigation it was observed that the computational investigation likely underpredicted the flow velocity ahead of the probe. Results from the experiments also indicate that PSV can be a versatile method for application to near-body flowfields due to its low power, low hazard, and low cost method of illumination