3D Particle Tracking Velocimetry to the Wall in a Zero Pressure Gradient Turbulent Boundary Layer with a Single Plenoptic Camera*

Using a single plenoptic camera we demonstrate 3D Particle tracking velocimetry (PTV) with velocities resolved down to the wall of a zero pressure gradient (ZPG) turbulent boundary layer. The unique plenoptic architecture creates four non-overlapping images of a scene directly on the camera sensor. Each image is a different orthographic view of the same scene with a maximum angle between views of 24^○. The four images can be separated then treated independently for calibration. This arrangement allows three dimensional triangulation and reconstruction of a volume up to 11×11×2.5 mm. The commercial software DaVis with the "Shake-the-Box" add-on was used to perform 3D PTV. This imager was used to take measurements in the viscous sublayer and buffer layer of the turbulent boundary layer at the bottom of a wind tunnel. The tunnel was designed with an adjustable ceiling that allows for the pressure gradient to be adjusted. For these measurements only a ZPG test case was looked at. Measurements were taken at one wind speed. Hot wire was used to estimate a Reynolds number based on momentum thickness of 6,100 and a viscous Reynolds number of 1,600. For validation the recovered velocities and turbulence statistics from the 3D PTV are compared with the hot wire data as well as test cases from the literature.