High speed stereoscopic shadowgraph imaging and its digital 3D reconstruction

Abstract

A stereoscopic shadowgraph system has been developed based on the conventional z-type schlieren configuration. The test volume is set at the intersection of two inclined converging beams formed by two pairs of parabolic mirrors. Two synchronized high speed cameras are applied to record the shadowgraph image pairs simultaneously. A precisely etched metal mesh plate is used to calibrate the stereoscopic shadowgraph system. By combining the calibration parameters and coordinates of the matching points in stereo images, the depth information and the 3D view of the shadowgraph images are obtained. A crystal block with internal 3D images created by laser etching is used as a model for static object reconstruction and validation. The 3D coordinates obtained by the digital 3D reconstruction are in good agreement with the real dimensions. The developed stereoscopic technique is then applied to investigate the bursting dynamics of a bubble. The time resolved bubble-bursting process has been reconstructed successfully. The quantitative velocity measurement reveals that the bubble collapses at a constant velocity of around 7 m s−1, which corresponds to a high Weber number. As a result, finger-like structures are observable around the rim of the collapsing bubble. The stereoscopic shadowgraph technique has been shown to be effective for 3D visualization and quantitative measurement.

A Comparison of Shadowgraphy and X-Ray Computed Tomography in Liquid Spray Analysis

“…In this X-ray X-ray Shadowgraphy Shadowgraphy capacity, X-ray CT scanning provides more detail of spray symmetry and changes in liquid distribution in various locations away from the nozzle. Shadowgraphy can provide spray cone angles and skew, and it has been shown the ability to produce 3D reconstructions with multiple cameras [11]. In principle, a tomographic reconstruction of shadowgraphy data could also be done if a rotation system was used to acquire images from many angles.…”

“…Due to this property, different orientations can result in slightly different results for nozzle symmetry or shape. Shadowgraphy can only help determine asymmetries in the plane normal to the camera's line of sight for single orientations, though 3D reconstruction is possible with multiple views on a spray [11].…”

Imaging Diagnostics for Jet Breakup into Droplets: A Review

“…The spray is then reconstructed by using a line-of-sight reconstruction technique. Stereoscopic shadowgraphy [38] uses four parabolic mirrors to form two inclined intersecting beams and the object is placed at the intersection. Two cameras synchronized in the masterslave configuration record the shadowgraph pairs automatically.…”

Experimental Techniques for Bubble Dynamics Analysis in Microchannels: A Review

“…Using two high-speed cameras at different angles and stereoscopic backlighting, it is possible to reconstruct 3D images from microbubbles. The 3D reconstruction of the bubble bursting process and the measurement of the bursting rims velocity was demonstrated by Wang and Zhang [63]. Voisin et al [64] reconstructed the 3D geometry of Taylor bubbles trapped inside hollow cellulose fibers from 2D shadowgraph images taken with only one camera.…”