Three-dimensional (3-D) velocity field reconstruction of oscillatory thermocapillary convections in a half-zone liquid bridge with a radius of O (1 mm) was carried out by applying 3-D particle tracking velocimetry (PTV). Simultaneous observation of the particles suspended in the bridge by two CCD cameras was carried out by placing a small cubic beam splitter above a transparent top rod. The reconstruction of the 3-D trajectories and the velocity fields of the particles in the several types of oscillatory-flow regimes were conducted successfully for sufficiently long period without losing particle tracking. With this application the present authors conducted a series of experiments focusing upon the collapse and re-formation process of the PAS by mechanically disturbing fully developed PAS.
Research Containing: Oscillatory flow regimes
Various flow patterns in thermocapillary convection in half-zone liquid bridge of high prandtl number fluid
Various flow patterns induced by a thermocapillary-driven convection in a half-zone liquid bridge of a high Prandtl number fluid (Pr = 0(10)) far beyond the critical condition were investigated experimentally. After the onset of oscillatory convection, one can observe several types of flow patterns with increasing a temperature difference between the both end surfaces of the bridge. The flow patterns were categorized through flow visualization, measurement of surface temperature variation and reconstruction of the pseudo-phase space.
Marangoni Experiment in Space (MEIS) has been conducted in the International Space Station (ISS) in order to clarify the transition processes of thermocapillary convection in liquid bridges. The use of microgravity allows us to generate long liquid bridges, 30mm in diameter and up to 60mm in length. Several flow visualization techniques have been applied to those large liquid bridges. 3-D PTV is used to reveal highly three-dimensional flow patterns that appear after the transition. Three CCD cameras are used to observe the motions of the tracer particles from different view angles through the transparent heated disk made of sapphire. Particle images are recorded in the HDD recording system in ISSand they are downloaded to the ground for data analysis. A conventional 3-D PTV technique and a newly-developed multi-frame particle tracking method are combined to obtain the results that can help better understanding of oscillatory 3-D flow fields in the liquid bridges. It is shown that the flow pattern changes from a 2-D axisymmetric steady flow to an oscillatory 3-D non-axisymmetric flow under the supercritical conditions.
Three-dimensional (3D) reconstruction of a unique particle motion in oscillatory thermocapillary convections in a small-sized half-zone liquid bridge with a radius of O (1 mm) was carried out by applying 3D particle tracking velocimetry (PTV). By placing a small cubic beam splitter above a transparent top rod, simultaneous observation of the particles in the bridge by use of two CCD cameras was realized. Reconstruction of the 3D trajectories and the particle velocity fields in several types of oscillatory flow regimes was conducted successfully for a sufficiently long period without losing particle tracking.