Particle Tracking Flow Visualization Research Articles

Fracture-Healing Kinetics of Thermoreversible Physical Gels Quantified by Shear Rheophysical Experiments.

The fracture-healing behavior of model physically associating triblock copolymer gels was investigated with experiments coupling shear rheometry and particle tracking flow visualization. Fractured gels were allowed to rest for specific time durations, and the extent of strength recovered during the resting time was quantified as a function of temperature (20-28 °C) and gel concentration (5-6 vol %). Measured times for full strength recovery were an order of magnitude greater than characteristic relaxation times of the system. The Arrhenius activation energy for post-fracture strength recovery was found to be greater than the activation energy associated with stress relaxation, most likely due to the entropic barrier related to the healing mechanism of dangling chain reassociation with network junctions.

Gap-flow patterns behind twin-cylinders at low Reynolds number

The flow structures, drag coefficients (Cd) and vortex shedding characteristics around a single square cylinder and twin side-by-side square cylinders were experimentally investigated with various Reynolds numbers (Re) and gap ratios (g*) in a vertical water tunnel. The Reynolds number (Re) and gap ratio (g*) were 178 < Re < 892 and 0 ≤ g* ≤ 2.5, respectively. The flow patterns and vortex shedding frequency were determined using the particle tracking flow visualization (PTFV). The flow structures, velocity properties, and drag coefficients were calculated using the particle image velocimetry (PIV). The topological flow patterns of vortex evolution processes were plotted and analyzed based on critical point theory. Furthermore, the flow structures behind twin side-by-side square cylinders were classified into three modes — single vortex-street mode, gap-flow mode and couple vortex-streets mode. The maximum Cd occurred in the single vortex-street mode, and the minimum Cd occurred in the gap-flow mode. The highest Strouhal number (St) occurred in the single vortex-street mode, and the lowest St occurred in the gap-flow mode.