Jostein Kolaas

Visualization and measurements of flows in micro silicon Y-channels

Velocities and accelerations are measured and visualized in silicon microchannels using particle tracking velocimetry (PTV). Both pulsatile and stationary flows are generated in channels with different geometry. Distinct differences between flow regimes and geometries are shown. Flow separation occurred at Re = 84 for the channel with an expanded bifurcation shown by streamlines from long exposed images. Moving least squares are used to find the ensemble-averaged positions of the measured velocities from tracking. This is needed to find the local and convective accelerations.Graphical abstract

Lagrangian Measurements of Two-Phase Pipe Flow Using Combined PIV/PTV

Measurements of two-phase particle suspension consisting of a liquid carrier phase and a solid particle phase are presented. Large diameter (d = [0.95−2.00] mm) and nearly neutral buoyant (ρp = 1050 kg m−3) particles are suspended in a turbulent fluid flow. The concentration of particles, φ ∼ 10−3, is slightly higher than previously reported in the literature. The carrier fluid is measured using particle image velocimetry (PIV), while the particle phase is measured with particle tracking velocimetry (PTV). There was found no evidence of turbulence modification within measurement accuracy, which is different form other studies using slightly heavier particles. Furthermore, challenges that arise with the use of combined PIV/PTV measurements at this flow regime and how these affects the measurements are discussed. GRAPHICAL ABSTRACT