Riccomi M, Alberini F, Brunazzi E, Vigolo D (2018) Ghost Particle Velocimetry as an alternative to μPIV for micro/milli-fluidic devices. Chem Eng Res Des 133:183–194.
Abstract:
Ghost Particle Velocimetry (GPV) has only been recently introduced and has already been proven useful in small scale phenomena investigations, such as the study of the flow field during single droplets generation in microfluidic devices. In this work, GPV was used to experimentally investigate fluid flow close to a T-shaped branched junction in a millimetre sized device. The experimental setup allowed for the first time, the study of complex fluid dynamic structures such as vortices and recirculation zones. Several experiments were performed to exploit the capability of GPV in carrying out flow field measurements, at different Reynolds numbers within the laminar flow regime and for two channel sizes. The results were validated by verifying the steady state and stability conditions and by comparing them with results obtained using the well-established micron-scale Particle Image Velocimetry (μPIV). Differences between these two velocimetry techniques were analysed in terms of qualitative and quantitative parameters, to attain a performance comparison and understand the strengths and weaknesses of each respective method.
Ariane M, et al. (2018) Using Discrete Multi-Physics for studying the dynamics of emboli in flexible venous valves. Comput Fluids 166:57–63.
Abstract:
Emboli, which are parts of blood clots, can be stuck in the vasculature of various organs (most frequently, lungs) and cause their malfunction or even death. In this work, using mathematical modelling, different types of emboli-like structures are studied in a double venous valve system. The model is implemented with a fully Lagrangian Discrete Multi-Physics technique and the flow is governed by flexible walls. The study shows the effect of different diameters and lengths of a free embolus in the flow surrounding the valve. The presence of an embolus strongly affects the dynamics of both the fluid and the leaflets in venous valves and the permanence of the embolus in the valve chamber is narrowly linked with its length.
Kovalchuk NM, Chowdhury J, Schofield Z, Vigolo D, Simmons MJH (2018) Study of drop coalescence and mixing in microchannel using Ghost Particle Velocimetry. Chem Eng Res Des 132:881–889.
Abstract:
The coalescence of drops formed in a flow focusing microfluidic device at Reynolds number 0.1 < Re < 1 was studied experimentally using high speed video-recording and Ghost Particle Velocimetry. It was shown that in the confined microfluidic geometry the presence of both ionic and non-ionic surfactants can facilitate drop coalescence for surfactants dissolved in either the dispersed or the continuous phase. Drop merging was accompanied by strong convection inside the drops with maximum velocity exceeding the superficial liquid velocity by one order of magnitude. Intensity of convection increased with a decrease of drop size and decreased with a decrease of interfacial tension between continuous and dispersed phase. Effect of drop size was particularly strong when the drop size exceeded 80% of the channel width due to the considerably thinner film of continuous phase separating dispersed phase from the channel wall, slower expelling of continuous phase surrounding growing neck between merging drops and therefore slower neck thickening. When merging drops of different sizes was considered, the convection was much stronger in the small drop and movement of the contents of the smaller drop towards the larger drop was observed.