Volumetric measurements of a self-similar adverse pressure gradient turbulent boundary layer using single-camera light-field particle image velocimetry

Abstract

As a novel volumetric particle image velocimetry technique, single-camera light-field PIV (LF-PIV) is able to reconstruct three-dimensional flow fields with a single camera. The merits of LF-PIV lie in its concise hardware setup and minimum optical access requirement, its capability has been proved in many flow scenarios. In this study, LF-PIV is used to measure a self-similar adverse pressure gradient turbulent boundary layer (APG-TBL). Experiments were performed in a large water tunnel at the Laboratory for Turbulence Research in Aerospace and Combustion (LTRAC), Monash University. 20 independent batches of light-field PIV images were captured for both inner and outer flow, each consisting of 250 instantaneous image pairs. Instantaneous 3D velocity fields were reconstructed with the GPU accelerated DRT-MART and 3D cross-correlation methods and compared with two-dimensional PIV (2D-PIV) results. Initial results show that though limited by the experiment conditions and PIV algorithms developed in 2016, we still can have similar accuracy to 2D-PIV near and above the boundary layer. With the volumetric calibration method that compensates optical distortions caused by lens defect and misalignment between the micro-lens array (MLA) and image sensor, the resolution of LF-PIV is sure to have a large improvement.

Volumetric flow characterisation of a rectangular orifice impinging synthetic jet with single-camera light-field PIV

“…SV-I seems to merge together as one single elongated vortical structure instead of two pairs of the inclined elongated structures. This drop in resolution is similar to other measurement results of LF-PIV [47] and may be due to the limited resolution of single-camera LF-PIV near the focal plane [45,56,57], so the details of vortical structure cannot be resolved. As for SV-II and AV, in this paper, these two kind structures can be seen in 𝑍 < 0 volume while the symmetrical parts in 𝑍 > 0 volume are absent.…”

“…As an alternative, LF-PIV provides a new means for a convenient appreciation of volumetric flow field [43][44][45]. In a similar hardware setup as the traditional 2D-PIV, LF-PIV could provide snapshots of 3D velocity field for complex flows [46][47][48]. As such, the current study is made use of the phase-locked single-camera LF-PIV to study an AR = 10 rectangular impinging synthetic jet as a representative case.…”

Camera calibration algorithm development for a two-view collimated shadowgraph system

“…In recent decades, particle image velocimetry (PIV) has been widely adopted for 2D velocity measurements [1,2]. Quite a few 3D PIV velocimetry techniques have been proposed, including stereoscopic PIV [3,4], tomographic PIV [5][6][7][8], holographic PIV [9,10], lightfield PIV [11][12][13], etc. The PIV techniques resolve the Euler velocity field by applying the cross-correlation algorithm in a certain area or volume, which involves an averaging effect.…”

A novel single-camera approach to large-scale, three-dimensional particle tracking based on glare-point spacing

“…Cierpka and Kähler (2012) adapted both principles (defocusing and astigmatism) successfully to enable 3D measurements in micro-PTV applications. Another promising singlecamera approach demonstrated by Fahringer et al (2015) and Zhao et al (2019) is light-field PIV (LF-PIV), where the third dimension is reconstructed using the information gathered from a single plenoptic camera. However, the method is limited by depth resolution and elongation effects of the reconstructed particles.…”