A.01 Laser diodes have been introduced as an optical measurement method for two-phase flow pattern characterization in microtubes to determine the frequency of bubbles generated in a microevaporator, the coalescence rates of these bubbles and their length distribution as well as their mean velocity. Four flow patterns (bubbly flow, slug flow, semi-annular flow and annular flow) with their transitions were detected and observed also by high speed video. Bubble coalescence rates were observed as an important phenomena controlling the flow pattern transition in microchannels
COBISS.SI-ID: 9522203
A.01 Column separation refers to the breaking of liquid columns in fully filled pipelines. This may occur in a water-hammer event when the pressure in a pipeline drops to the vapour pressure. The liquid columns are separated by a vapour cavity that grows and diminishes according to the dynamics of the system. The collision of two liquid columns, or of one liquid column with a closed end, may cause a large and nearly instantaneous rise in pressure. This pressure rise travels through the entire pipeline and forms a severe load for hydraulic machinery, individual pipes and supporting structures.
COBISS.SI-ID: 8818203
A.05: Top 1% Cited Article: Trajectories of single air bubbles in simple shear flows of viscous liquids were measured to present a net transverse lift force CT. It was confirmed that CT for small bubbles is a function of the bubble Reynolds number Re, whereas CT for larger bubbles is well correlated with a modified Eotvos number Eo. The critical bubble diameter causing the radial void profile transition from wall peaking to core peaking in an air–water bubbly flow can be well predicted by the proposed CT correlation which is currently widely used by computer simulations of two-phase flow
COBISS.SI-ID: 5085723
A.01 Some evidences of complexity that may play a crucial role in flow regime transition of bubbly flow in vertical pipes of centimeter scale are reported. Such a complex nature most likely contributes to several unresolved questions about transient conditions.Different examples that were studied under this program are considered: bubbly to slug flow transition in a vertical pipe under adiabatic conditions, cavitating bubbly structures and suspended bubbles in forced mixing. Although different cases by nature, they enable a common approach that can be described roughly as a two-part process
COBISS.SI-ID: 8411931
Modeled with the volume-of-fluid (VOF) and discretized with the finite volume method, the discontinuous body force fields are represented as abruptly variable. Such variable can produce unphysical spikes in the velocity field when collocated arrangement is used. The spikes can be eliminated following a force field discretization rule. This is deduced by imposing a constraint requiring zero velocity solution when forces applied to the system are equilibrated with the gradient of pressure field. Gravity and continuum surface force (CSF) are considered for the free rising bubble in a liquid
COBISS.SI-ID: 9848347