Projects / Programmes
Transient two-phase flows
January 1, 2009
- December 31, 2014
| Code |
Science |
Field |
Subfield |
| 2.13.00 |
Engineering sciences and technologies |
Process engineering |
|
| Code |
Science |
Field |
| T200 |
Technological sciences |
Thermal engineering, applied thermodynamics |
| T210 |
Technological sciences |
Mechanical engineering, hydraulics, vacuum technology, vibration and acoustic engineering |
| T160 |
Technological sciences |
Nuclear engineering and technology |
| T130 |
Technological sciences |
Production technology |
| T121 |
Technological sciences |
Signal processing |
| Code |
Science |
Field |
| 2.11 |
Engineering and Technology |
Other engineering and technologies |
Two-phase flow, bubbles, cavitation, transient phenomena, complex systems, experimental techniques, numerical simulations, cascade modelling
Researchers (12)
| no. |
Code |
Name and surname |
Research area |
Role |
Period |
No. of publicationsNo. of publications |
| 1. |
03923 |
PhD Anton Bergant |
Process engineering |
Researcher |
2009 - 2014 |
392 |
| 2. |
05912 |
PhD Andrej Bombač |
Process engineering |
Researcher |
2009 - 2014 |
222 |
| 3. |
36852 |
Matic Cotič |
|
Technical associate |
2014 |
23 |
| 4. |
32071 |
PhD Jurij Gregorc |
Materials science and technology |
Researcher |
2009 - 2014 |
89 |
| 5. |
35623 |
Nejc Lojevec |
|
Technical associate |
2013 - 2014 |
10 |
| 6. |
31564 |
PhD Matevž Luštrik |
Pharmacy |
Researcher |
2012 - 2014 |
46 |
| 7. |
15259 |
PhD Jure Mencinger |
Computer intensive methods and applications |
Researcher |
2009 - 2014 |
43 |
| 8. |
04471 |
PhD Matjaž Perpar |
Process engineering |
Researcher |
2009 - 2014 |
128 |
| 9. |
36399 |
PhD Jernej Pirnar |
Engineering sciences and technologies |
Junior researcher |
2013 - 2014 |
19 |
| 10. |
01371 |
PhD Zlatko Rek |
Process engineering |
Researcher |
2009 - 2014 |
217 |
| 11. |
20661 |
Borut Stražišar |
Manufacturing technologies and systems |
Technical associate |
2010 - 2011 |
24 |
| 12. |
03544 |
PhD Iztok Žun |
Process engineering |
Head |
2009 - 2014 |
540 |
Organisations (1)
Abstract
The primary drive in the technical advances of heat and mass transfer being sought is to develop a deeper understanding of the physics of multiphase flow, and having acquired that insight, to develop appropriate mathematical models to predict the phenomena involved. Next, some if not all of the models will need to be incorporated into appropriate software (namely CMFD) ready for testing and validation against experimental data.
Research efforts will be particularly required on the interactions between the carrier phase turbulence and bubbles, between bubbles and boundaries (walls, free surface) and between bubbles (collisions and pair interactions, agglomerate formation and break-up, collective effects involving clusters of bubbles). There is a specific need for modelling of such meso-scale structures and for developing new measuring techniques adapted to such scales. In all these mechanisms, account should be made of interface deformations that have been scarcely considered so far, either due to limitations of the measuring techniques in experiments or due to limitations in terms of computational power in simulations.
It is envisaged that the multiphase flows considered will not be restricted to simple geometry only but will also include more complex systems including a variety of boundary types, moving surfaces (such as stirrers) which are common in industry. The approach could lead to developments in low dimensional models suitable for active control schemes.
Research actions are organised in three thematic addressing some of the key scientific issues of relevance in the process industry. These are:
(a) Development of cascade modeling
Our strategy distinguishes four steps to disassemble the complex system in different scales in order to obtain necessary information for multiscale modeling in the fifth stage. The steps are: (1) Structures identification which provides frozen details in spatial character, (2) Spatial relationships between frozen structures, (3) Time-space evolution of each structure, and (4) Statistical relevance. All four steps proved to serve well in cascade modelling that can be done in reassembling step (5) in order to mimic complex bubbly flows.
One of the goals of the program anticipates further development of intelligent instrumentation which contributes towards system optimization. Successful scale separation is going to be accompanied by further development of coupled numerical modelling, like two-fluid modelling with incorporated bubble distribution function or VOF technique imbedded in bubble tracking scheme.
(b) Cavitation phenomenon
Despite of numerous literature on cavitation, the details that describe a particular cavitating flow pattern, like cloud cavitation, are not sufficient to provide information that is indispensable for multi-scale numerical simulation. The aim of this part of the project is to perform a slow down experiment with expanded bubbles to the size to be able to obtain the data on meso- as well as on micro-scales.
A second complex treatment is going to be devoted to the transient flows in pipeline systems.
(c) Two-phase flow in microchannels
There is no doubt, that in the future the miniaturisation of technical equipment will be the most important task in engineering science. The rationalized material and energy consumption including the reduction in environmental pollution, are only some benefits of smaller components. It is even more important that a lot of applications are not conceivable without miniaturised systems, e.g. in medical technology or in space flight, where the size or the mass of the equipment is decisive.
The following objectives are going to be considered: (1) Experimental investigation of two-phase flow structures in simple and complex mini- and micro-channels, (2) Numerical modelling of two-phase flow phenomena and (3) Interface sharpening numerical requirements due to surface interface discontinuity.
Significance for science
Research actions were organised in three thrust areas addressing some of the key scientific issues of relevance in the process industry. These are: The principles of complex fluid dynamics, Flow-induced materials problems, and Fluid-structure interaction. Binary mixtures that have a coexistence between the two phases are regarded as complex fluids. They exhibit unusual mechanical responses to applied stress or strain due to the geometrical constraints that the phase coexistence imposes. Their mechanical properties can be attributed to characteristics such as high disorder, caging, and clustering on multiple length scales. The interfacial area concentrations are considered in our view as the essence of all fluid-fluid flows in connection to the underlying processes of interfacial breakup and coalesence. Especially for coalescence, the proximity of interfaces is important, and thus we need the actual distributions of phase concentrations (volume fractions) and length scales. This is the essence of the notion of Flow Regimes, as extended from the classical pipeline “maps” that are being used for more than three decades with a limited success. While the various practical situations outlined have hitherto been approached largely in isolated, more-or-less ad hoc, approaches, there is sufficient indication and promise that a more generic, far reaching approach is appropriate at this time [COBISS.SI-ID 12534811]. This judgement is based on the following consideration: (a) Availability of computational resources, including computing power, advanced CFD algorithms, especially in interface tracking; (b) Sophisticated experimental and non-intrusive diagnostic techniques made possible recently by digital technologies) Our program group has now original results on multifluid CFD (Eulerian and Lagrangian with Top 1% citations, see COBISS.SI-ID 5085723), and very promising recent results on fundamentally-based predictions of mixing characteristics at the inlet of a mini manifold. Two mixers were used as a benchmark test: a porous media mixer and cross-junction mixer. In our 2009 to 2014 program, we have succeeded in developing a numerical algorithm of inlet conditions with continuous flow rates of both phases that produce interfacial flow patterns comparable with experimentally observed cases [Chem. Eng. Science, 2013, vol. 102, pp. 106-120; COBISS.SI-ID 13081371]. Similarly promising initial results have been obtained for mixing of thermally stratified water layer by a free rising wobbling air bubble [Chem. Eng. Science, 2012, vol. 72, pp. 155-171, COBISS.SI-ID 12220187].
Significance for the country
Direct significance for businesses and publicly-provided services: Multiphase flow systems are crucial in most sectors of the process industry, such as chemical, biochemical, food, pharmaceutical, paper, and hydrocarbon production. All these are traditionally strong industries in the EU and account for a major part of economic turnover. For example, the EU chemical industry is one of the European Union’s most international, competitive and successful industries, connected to a wide field of processing and manufacturing activities. The output of the chemical industry, which includes all 28 EU member states covers a wide range of chemical products, supplies virtually all sectors of the economy and provides 20% of the world production (the latest statistics date from 2013, http://www.cefic.org/Facts-and-Figures/). Significance for development of research (sub)segments in short supply: Similar trends can be shown for pharmaceutical and chemical industry in Slovenia. To ensure the competitiveness or even technological advantage, Slovenia is forced to develop new production methods and innovative materials in a sustainable manner. There is no doubt, that in the future the miniaturization of technical equipment will be the most important task in engineering science. The reductions of the material and energy consumption, including the reduction in environmental pollution, are only some benefits of smaller components. Such a development is possible only when based on sound theoretical and empirical analytical tools which by no doubt includes also the prediction of transient characteristics of multiphase processes. Potential impacts and effects of results: The research group has been well involved in industrial applications, having direct contracts with the following companies: Rhodia (Solvay), France (gas-liquid interface instability), Lek (Sandoz Group), Slovenija (gas-liquid forced mixing), Gorenje, Slovenija (rational energy use in kitchen appliances), Energetiko Ljubljana, Slovenija (heat losses in wet porous insulation), Litostroj Power (unsteady skin friction modelling in hydraulic piping systems), University Medical Center Ljubljana (OSAS), Faculty of Pharmacy, University of Ljubljana and Brinox (peletization). An example of good practise: Besides sound applications in Gorenje and Energetika Ljubljana, the originality and relevance of our research has been proven so far also in system design in pharmaceutical industry. We are working here in collaboration with the Faculty of pharmacy, University of Ljubljana, on technology based fluidization technique for solid particle coating purpose. Effective particle coating is possible only if particles entering the coating process are suspended in the upflowing fluidization gas. This enables the droplets of coating liquid to be deposited onto the particle surface and in the evaporate stage the solvent to be removed due to heated fluidization air. We have succeeded in patenting a new process coating device that falls within the field of chemical and pharmaceutical technology. [see US Patent 8689725 (B2), 2014-04-08, COBISS.SI-ID 12184091]. Examples of effective dissemination: - Lectures at the Faculty of Mechanical Engineering, University of Ljabljana, second and third Bologna cycle - In Lausanne, we have established together with EPFL and Kobe University the Virtual International Research Institute of Two-Phase Flow and Heat Transfer (ViR2AL) with a mission to improve and foster international collaboration between world class two-phase flow and heat transfer laboratories (see http://2phaseflow.org/). The goals of the Virtual Institute are to: share and preserve experimental data sets on two-phase flow and heat transfer and to share and preserve numerical two-phase simulation data sets.
Audiovisual sources (1)
Most important scientific results
Annual report
2009,
2010,
2011,
2012,
2013,
final report,
complete report on dLib.si
Most important socioeconomically and culturally relevant results
Annual report
2009,
2010,
2011,
2012,
2013,
final report,
complete report on dLib.si
