A Two-Phase Cinematic PIV Method for Bubbly Flows

Abstract

A cinematic particle image velocimeter (PIV) for measurement of time varying fields in two-phase flow is described. This system has the capability to track detailed characteristics of individual bubbles moving through a turbulent flow field, e.g., size, shape, velocity, and acceleration, and simultaneously to measure the instantaneous fluid velocity field on a two-dimensional plane. The system employs an argon-ion laser, a rotating polygonal mirror and a single 35 mm movie camera. Two features of this technique are the ability to capture bubble trajectories for long periods of time and the use of bubble images which appear as two fine point images for each instant, from which centroid and diameter can be deduced. The instrument is evaluated in an experiment on the dispersion of nominally 3.5 mm diameter bubbles from a point source in a two stream, turbulent, planar free-shear layer. Characteristics of the fluid field and the bubble motion are described.

Laser Doppler anemometry (LDA) and particle image velocimetry (PIV) for marine environments

“…Masking techniques have been extensively documented in the literature by for example Gui (1996), Jakobsen (1996), Oakley (1997), Palero (1998), Kiger (2000), Khalitov (2002), Lindken (2002), Gui (2003), and Poelma (2006b). Poelma (2006a) gives a review of research on two-way coupling between turbulent fl ow and particles.…”

Forces on ellipsoidal bubbles in a turbulent shear layer

“…12 It produced a high-speed velocity of 0.425 m/s and a velocity ratio of 0.23, yielding an average liquid velocity (U ave ) of 0.26 m/s. This results in a high Reynolds number of 26 000 based on the thickness of the shear layer, which yields a fully developed turbulent flow ͑Oakley et al 13 ͒. Further details of the water tunnel and splitter plate design can be found in Loth and Cebrzynski.…”

“…Use of a triple pulse ͑instead of just a double͒ eliminates the need for precise synchronization between the shutter and the scanning mirror and increases the signal-to-noise ratio of the PIV correlation ͑Keane and Adrian 17 ͒. Further details of this design, as well as the results of both the single-phase shear layer and bubbly flows, can be found in Oakley 20 and Oakley et al 13,21 The seeding particles used in this study are 8 hollow glass sphere tracer particles ͑specific gravityϭ1.1͒ manufactured by Potters Industries. The particle concentration was approximately 0.002 g/l, which is enough to ''contaminate'' the water but an order of magnitude below the minimum value which denotes ''grossly contaminated'' systems.…”

“…It was observed by Oakley et al 13 that the instantaneous image of an ellipsoidal bubble illuminated by a perpendicular scanning laser beam is two points of light. This is consistent with the more general scattering optics of bubbles described by Langley and Marston.…”

A modified cross-correlation algorithm for PIV image processing of particle-fluid two-phase flow

“…V u v , = ( ⌢ ⌢ ) The displacement vector obtained by calculation images of two-phase flow is to separate the continuous and dispersed phase images firstly, and then a corresponding PIV operation is performed. However, some algorithms are too complicated, such as spatial frequency method [22] and shape discrimination method [23] which not only have a strict requirement for trace seeds or solid particles but also become very complex by using spatial filters.…”