Chiara Pesci

Dr. Chiara Pesci

+49 6151 16-21470
+49 6151 16-21472

Alarich-Weiss-Straße 10
64287 Darmstadt

Office: L2|06 412

Computational Analysis of Fluidic Interfaces Influenced by Soluble Surfactant

Research Motivation

The project is concerned with the study of transport processes on moving and deforming fluid interfaces via mathematical and numerical modeling. The focus is on multiphase flows with the presence of surfactants. Surfactants are chemical substances essential in many technological processes such as foaming and emulsification. Due to their amphiphilic character they accumulate at fluidic interfaces and modify the respective interfacial properties. Direct Numerical Simulation (DNS) are performed to obtain valuable information about interfacial transport processes in systems with surfactants which would not be easily accessible through experimental investigations.

Scientific Project

The state-of-the-art for mathematical and numerical modeling of such flows consists of a numerical method based on interface tracking that enables to compute free surface flows with soluble or insoluble surfactant mixtures [1, 2], and two-phase flows with a soluble surfactant species [3, 4]. During the current project more attention will be given to two-phase flows contaminated by surfactants. The existing simulation tools will be enhanced and further developed in order to include the influence of surfactant on species transfer, partitioning in oil/water systems, improvement of the model based on the Gauss-Laplace equation in a dynamic scenario, and interface rheology. Moreover, the knowledge in terms of mathematical modeling and numerics related to free-surface flows with multicomponent non-dilute surfactant mixtures will be transferred to multiphase systems.

An Arbitrary Lagrangian Eulerian (ALE) Interface-Tracking method is employed. The model equations are discretized by means of collocated Finite Volume/Finite Area Methods for transport processes in the bulk and on the interface, [4]. The method supports a moving computational mesh with automatic mesh deformation and eventually re-meshing. Particular attention will be given to multicomponent mixture of surfactants diffusing and adsorbing at the interface. The description of the transport of surfactant in the bulk and on the interface is included in the model. To account for sorption processes, several sorption models are included. The overall numerical procedure will be validated and verified by comparison with analytical solutions and experimental data. Test cases then comprises growing droplets with soluble surfactants for free surface flows, [1], single rising bubbles in quiescent contaminated water [3,E1], Taylor Bubbles and Taylor flows for two-phase flows.

As a first test case, a single rising bubble in quiescent water with and without surfactant is considered. The comparison between the clean and the contaminated cases shows notable differences, for instance in terms of bubble path, shape and flow pattern inside and outside the bubble.

Fig. 1: Single rising bubble in quiescent liquid with and without surfactant. Image: M. Sc. Chiara Pesci
Fig. 1: Single rising bubble in quiescent liquid with and without surfactant. Image: M. Sc. Chiara Pesci

Acknowledgements

The author thanks the German Research Foundation (DFG) for financial support within the Priority Program SPP1506 “Transport Processes at Fluidic Interfaces” [BO1879/9-2].

Project References

[1] K. Dieter-Kissling, H. Marschall, and D. Bothe. Direct Numerical Simulation of droplet formation processes under the influence of soluble surfactant mixtures. Computers & Fluids, 113:93-105, 2015.

[2] K. Dieter-Kissling, H. Marschall, and D. Bothe. Numerical method for coupled interfacial surfactant transport on dynamic surface meshes of general topology. Computers & Fluids, 109:168-184, 2015.

[3] Z. Tukovi_c and H. Jasak. Simulation of free-rising bubble with soluble surfactant using moving mesh Finite Volume/Area method. In 6th International Conference on CFD in Oil & Gas, Metallurgical and Process Industries SINTEF/NTNU, Trondheim, Norway, 10-12 June 2008.

[4] Z. Tukovic and H. Jasak. A moving mesh Finite Volume Interface Tracking method for surface tension dominated interfacial fluid flow. Computers & Fluids, 55:70-84, 2012.

Publications

[E1] C. Pesci, K. Dieter-Kissling, H. Marschall, and D. Bothe. Finite volume/finite area interface tracking method for two-phase flows with fluid interfaces influenced by surfactant. In M.T. Rahni, M. Karbaschi, and R. Miller, editors, Progress in colloid and interface science. CRC Press, Taylor & Francis Group, 2015.

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