Dispersed Turbulent Two-Phase Flow

Purpose and focus of SIG

Dispersed turbulent multi-phase flows are found in daily life, in the environment and in numerous technical and industrial processes. Specifically, the environmental aspects are getting more and more of extreme importance, such as air pollution by aerosols and microplastics in the ocean. Other examples are: application of hair sprays, exhaust gas cleaning, sediment transport in rivers, aeolian sand transport, volcanic eruptions, cloud physics, swage water treatment, fuel injection in engines, pneumatic and hydraulic transport, bubble column reactors, spray driers for food processing and spray coating of pharmaceutical products, to name only a few. Hence, it seems that dispersed multiphase flows are of larger importance than single-phase flows, although of course the turbulent transport of the dispersed particles is an essential elementary process in nature and technology. The dispersed phase may consist of solid particles, liquid droplets and gas bubbles; generally termed “particles”. In the past, generally these dispersed elements were considered as being spherical and therefore could be easily represented as point masses. However, the real world generally includes non-spherical particles of regular or even irregular shape. Research in this field has largely expanded over the last two decades.

Due to the interaction between the phases and the involved different time and length scales as well as the numerous elementary transport processes for the particles (e.g., wall collisions, deposition, inter-particle collisions and coalescence and droplet/bubble breakup), multi-phase processes are rather complicated and a theoretically based design and optimisation of processes is almost impossible. Moreover, the scale-up of industrial processes is still a major challenge and not straightforward, often requiring experiments at different scale size.

All these demanding issues initiated the application of CFD to dispersed two-phase flows probably more than 40 years ago. However, for performing reliable numerical computations of two-phase flows, detailed models describing the interfacial transport and other relevant elementary processes, as for example, particle-wall collisions, inter-particle collisions, agglomeration and coalescence, are needed. Mostly, such a model development requires detailed experimental information. Nowadays, particle-resolved direct numerical simulation (DNS) with explicit resolution of particle surfaces and fluid-fluid interfaces, have also become a very powerful tool for analysing fundamental processes. Over the past decades, the fluid forces acting on non-spherical particles have also been derived from such PR-DNS and subsequently used in point-mass simulations of dispersed multiphase flows.

The major objective of SIG12 is the improvement of numerical prediction tools for dispersed turbulent multi-phase flows and the associated models. This includes specifically the Euler/Euler and the Euler/Lagrange approaches. Moreover, the elaboration of benchmark test cases for validating numerical simulation frameworks is an essential task of SIG 12. These goals are reached by involving the following aspects:

• Exchange of knowledge and results on elementary processes (experimental data and PR-DNS results).
• Development of models for the numerical computation of dispersed multi-phase flows and their validation (test case database).
• Definition and establishment of detailed benchmark test cases on dispersed multi-phase flows aimed at code validation.
• Organisation of workshops on the numerical prediction of dispersed two-phase flows for exchanging ideas and developments.
• Organisation of summer schools and courses on experiments and numerical predictions for dispersed multi-phase flows for the education of PhD students and other scientists from industry and academia.
• Collaboration with industry on model development, process design, and optimisation.

Activities of the SIG:

1. Best Practice Guidelines for Computational Fluid Dynamics of Dispersed Multiphase Flows,
(Eds. M. Sommerfeld, B. van Wachem and R. Oliemans) Version 1, Printed October 2008

2. Contributions to the ERCOFTAC Knowledge Base WIKI: https://www.ercoftac.org/products_and_services/wiki/

• Orifice/deflector flow (Ph.D. Thesis of An-Bang Wang, LSTM Erlangen, summarised by M. Sommerfeld)
• Spray evaporation in turbulent flow (M. Sommerfeld)
• Particle-laden swirling flow (M. Sommerfeld)
• Aerosol deposition in the human upper airways (P.Koullapis, F. Lizal, J. Jedelsky, M. Jicha, L. Nicolaou, S.C. Kassinos, O. Sgrott, M. Sommerfeld)
• Airflow in the human upper airways (P.Koullapis, J. Muela, O. Lehmkuhl, F. Lizal, J. Jedelsky, M. Jicha, T. Janke, K. Bauer, M. Sommerfeld, S.C. Kassinos)
• Polydispersed two-phase flow downstream of a confined bluff body (Pascal Fede, Olivier Simonin, Martin Sommerfeld)

3​. Data Base for Dispersed Multi-Phase Flow Predictions:

Various test cases for validating numerical predictions of dispersed multi-phase flows, such as confined particle-laden jet, dispersion of particles in a shear layer, particle laden vertical and horizontal channel flows, particle dispersion in swirling flow, circulating fluidised beds, and evaporating sprays are available at: https://www.mps.ovgu.de/mps/en/home/Test+cases.html

4. Best Practice Guidance Seminars:

• Best Practice Guidance Series CFD for Dispersed Multi-Phase Flows”, Chalmers University of Technology, October 2007
• ERCOFTAC Best Practice Guidance Series: CFD for Dispersed Multi-Phase Flows, Innventia AB, Stockholm, Sweden, 7. – 8. June 2011
• ERCOFTAC Best Practice Guidance Series; CFD for Dispersed Multi-Phase Flows. University of Graz, Austria, 18. – 19. July 2012
• ERCOFTAC Best Practice Guidance Series; CFD for Dispersed Multi-Phase Flows. GE Global Research Center, Garching, 03. - 04. April 2014
• ERCOFTAC Best Practice Guidance Series; CFD for Dispersed Multi-Phase Flows. Imperial College, London, UK, 1 – 2 October 2015
• ERCOFTAC Best Practice Guidance Series; CFD for Dispersed Multi-Phase Flows. KTK Stockholm, Sweden, 10. – 11. October 2016
• ERCOFTAC Best Practice Guidance Series; CFD for Dispersed Multi-Phase Flows. OvGU University of Magdeburg, Germany, 20. – 21. November 2017
• ERCOFTAC Best Practice Guidance Series; CFD for Dispersed Multi-Phase Flows with problem shooting session. Warsaw University of Technology, Poland, 15. – 16. October 2018
• ERCOFTAC Best Practice Guidance Series; CFD for Dispersed Multi-Phase Flows with problem shooting session.; prior to ICMF2019 in Rio de Janeiro Brazil, May 2019
• ERCOFTAC Best Practice Guidance Series; CFD for Dispersed Multi-Phase Flows with problem shooting session.Sapienza Università di Roma, Rome, Italy, October 2021
• ERCOFTAC Best Practice Guidance Series; CFD for Dispersed Multi-Phase Flows with problem shooting session. Ecole Centrale de Lyon, France, October 2022
• ERCOFTAC Best Practice Guidance Series; CFD for Dispersed Multi-Phase Flows with problem shooting session. Czech Technical University, Prague, September 2024.

Past Technical Programme:

1. Workshops: (Report in ERCOFTAC Bulletin No. 95, June 2013)

• 13th Workshop on Two-Phase Flow Predictions, Halle (Saale), 17. to 20. September 2012, organised by Prof. Dr.-Ing. M. Sommerfeld, University of Halle

Test Cases:
- Sedimentation of a solid particle towards a plane wall; test case for fully resolved DNS (Ten Cate et al. 2002)
- Small-scale liquid-solid fluidised bed with about 2000 particles and a mean volume fraction of 30% (data from University of Toulouse)
- DNS data on droplet coalescence in homogeneous isotropic turbulence (data from IMF Toulouse)
- Pneumatic conveying of fine particles through a horizontal glass pipe with a length of 5.5 m and a diameter of 80 mm (experimental data of Huber and Sommerfeld 1994)

• 14th Workshop on Two-Phase Flow Predictions, Halle (Saale), 07. to 10. September 2015, organised by Prof. Dr.-Ing. M. Sommerfeld, University of Halle

Test Cases:
- Dense particle-laden free jet with different solids loading (Prof. J. Sinclair-Curtis)
- Dispersion of rod-like particles in a free jet, ejected from a narrow pipe (G. P. Romano, Roma; Prof. C. Marchioli)

2. Bulletin Contributions:

• THEME: Modelling of Dispersed Turbulent Two-phase Flows. (Ed. M. Sommerfeld and R. Perkins), Bulletin 36, 1998
• THEME: Dispersed multiphase flow: From microscale to macroscale numerical modelling (Ed. M. Sommerfeld), Bulletin No. 82, March, 2010
• THEME: Respiratory Airflows and Aerosol Deposition (Ed. S.C. Kassinos and J. Sznitman), Bulletin No. 128, September, 2021