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Subject: Two phase flow ×

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Now showing 1 - 4 of 4
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    Dynamics of droplet formation at T-shaped nozzles with elastic feed lines
    (Heidelberg : Springer, 2010) Malsch, D.; Gleichmann, N.; Kielpinski, M.; Mayer, G.; Henkel, T.; Mueller, D.; Van Steijn, V.; Kleijn, C.R.; Kreutzer, M.T.
    We describe the formation of water in oil droplets, which are commonly used in lab-on-a-chip systems for sample generation and dosing, at microfluidic T-shaped nozzles from elastic feed lines. A narrow nozzle forms a barrier for a liquid-liquid interface, such that pressure can build up behind the nozzle up to a critical pressure. Above this critical pressure, the liquid bursts into the main channel. Build-up of pressure is possible when the fluid before the nozzle is compressible or when the channel that leads to the nozzle is elastic. We explore the value of the critical pressure and the time required to achieve it. We describe the fluid flow of the sudden burst, globally in terms of flow rate into the channel and spatially resolved in terms of flow fields measured using micro-PIV. A total of three different stages-the lag phase, a spill out phase, and a linear growth phase-can be clearly discriminated during droplet formation. The lag time linearly scales with the curvature of the interface inside the nozzle and is inversly proportional to the flow rate of the dispersed phase. A complete overview of the evolution of the growth of droplets and the internal flow structure is provided in the digital supplement. © The Author(s) 2009.
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    A numerical study on deformation of Newtonian droplets through converging cylindrical dies
    (Berlin : de Gruyter, 2013) Mostafaiyan, M.; Saeb, M.R.; Ahmadi, Z.; Khonakdar, H.A.; Wagenknecht, U.; Heinrich, G.
    In this work, the dynamic deformation of a viscose Newtonian droplet passing through cylindrical converging dies has been studied. The changes in the interfacial area between two immiscible Newtonian fluids have been considered as a variable representing the time-dependent deformation of a circular droplet along converging dies. To do so, a surface tracking method has been incorporated into a finite element code, developed by the authors, which quantifies the deformation of the droplet through the converging path, and where the surface area of the deformed drop has been consequently chosen as a criterion for a two-phase interface. In this study, it has been revealed that by changing both rheological and geometrical parameters it is possible to manage the value of interface area between two phases. Ultimately, a unique curve is developed for each droplet to primary phase viscosity ratio which can correlate drop deformation with geometrical parameters.
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    Development of a numerical workflow based on μ-CT imaging for the determination of capillary pressure–saturation-specific interfacial area relationship in 2-phase flow pore-scale porous-media systems: a case study on Heletz sandstone
    (Göttingen : Copernicus Publ., 2016) Peche, Aaron; Halisch, Matthias; Bogdan Tatomir, Alexandru; Sauter, Martin
    In this case study, we present the implementation of a finite element method (FEM)-based numerical pore-scale model that is able to track and quantify the propagating fluid–fluid interfacial area on highly complex micro-computed tomography (μ-CT)-obtained geometries. Special focus is drawn to the relationship between reservoir-specific capillary pressure (pc), wetting phase saturation (Sw) and interfacial area (awn). The basis of this approach is high-resolution μ-CT images representing the geometrical characteristics of a georeservoir sample. The successfully validated 2-phase flow model is based on the Navier–Stokes equations, including the surface tension force, in order to consider capillary effects for the computation of flow and the phase-field method for the emulation of a sharp fluid–fluid interface. In combination with specialized software packages, a complex high-resolution modelling domain can be obtained. A numerical workflow based on representative elementary volume (REV)-scale pore-size distributions is introduced. This workflow aims at the successive modification of model and model set-up for simulating, such as a type of 2-phase problem on asymmetric μ-CT-based model domains. The geometrical complexity is gradually increased, starting from idealized pore geometries until complex μ-CT-based pore network domains, whereas all domains represent geostatistics of the REV-scale core sample pore-size distribution. Finally, the model can be applied to a complex μ-CT-based model domain and the pc–Sw–awn relationship can be computed.
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    Simulation and control of a nonsmooth Cahn--Hilliard Navier--Stokes system with variable fluid densities
    (Berlin : Weierstraß-Institut für Angewandte Analysis und Stochastik, 2019) Gräßle, Carmen; Hintermüller, Michael; Hinze, Michael; Keil, Tobias
    We are concerned with the simulation and control of a two phase flow model governed by a coupled Cahn--Hilliard Navier--Stokes system involving a nonsmooth energy potential.We establish the existence of optimal solutions and present two distinct approaches to derive suitable stationarity conditions for the bilevel problem, namely C- and strong stationarity. Moreover, we demonstrate the numerical realization of these concepts at the hands of two adaptive solution algorithms relying on a specifically developed goal-oriented error estimator.In addition, we present a model order reduction approach using proper orthogonal decomposition (POD-MOR) in order to replace high-fidelity models by low order surrogates. In particular, we combine POD with space-adapted snapshots and address the challenges which are the consideration of snapshots with different spatial resolutions and the conservation of a solenoidal property.