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Publications (10 of 16) Show all publications
Kékesi, T., Altimira, M., Amberg, G. & Prahl Wittberg, L. (2019). Interaction between two deforming liquid drops in tandem and various off-axis arrangements subject to uniform flow. International Journal of Multiphase Flow, 193-218
Open this publication in new window or tab >>Interaction between two deforming liquid drops in tandem and various off-axis arrangements subject to uniform flow
2019 (English)In: International Journal of Multiphase Flow, ISSN 0301-9322, E-ISSN 1879-3533, p. 193-218Article in journal (Refereed) Published
Abstract [en]

A Volume of Fluid (VOF) method is applied to study the interaction between two liquid drops with the same initial diameter in uniform flow. Various arrangements of the drops are studied, based on two parameters, namely the initial separation distance and the angle between the line connecting the centres of the drops and the free-stream direction. Initial separation distances of 1.5–5 drop diameters, and angles between β=0 ∘ and 90° are considered. Simulations for a Weber number of We=20, two Reynolds numbers Re=20 and 50, and density and viscosity ratios in the range ρ * =20–80 and μ * =0.5–50 are performed. The movement of the secondary drop with respect to the primary drop, and estimates on the time required for the breakup of the secondary drop as compared to those observed for single drops are evaluated. It is found that the drops collide only in cases corresponding to the shortest initial displacements, while in others they deform and break up independently, similarly or identically to single drops. The same behaviour is reflected in the time required for breakup. Cases where the drops behave independently show breakup times close to those observed for single drops.

Place, publisher, year, edition, pages
Elsevier Ltd, 2019
Keywords
Breakup time, Drop, Interaction, Off-axis, Regime map, Tandem, Reynolds number, Break-up time, Drops
National Category
Other Engineering and Technologies
Identifiers
urn:nbn:se:kth:diva-248149 (URN)10.1016/j.ijmultiphaseflow.2018.11.009 (DOI)000460717400014 ()2-s2.0-85059345769 (Scopus ID)
Note

QC 20190425

Available from: 2019-04-25 Created: 2019-04-25 Last updated: 2019-04-25Bibliographically approved
Heide, J., Karlsson, M. & Altimira, M. (2017). Numerical Analysis of Urea-SCR Sprays under Cross-Flow Conditions. Paper presented at 4 April 2017 through 6 April 2017. SAE technical paper series, 2017-March(March)
Open this publication in new window or tab >>Numerical Analysis of Urea-SCR Sprays under Cross-Flow Conditions
2017 (English)In: SAE technical paper series, ISSN 0148-7191, Vol. 2017-March, no MarchArticle in journal (Refereed) Published
Abstract [en]

Selective Catalytic Reduction (SCR) of NOx through injection of Urea-Water-Solution (UWS) into the hot exhaust gas stream is an effective and extensively used strategy in internal combustion engines. Even though actual SCR systems have 95-96% de-NOx efficiency over test cycles, real driving emissions of NOx are a challenge, proving that there is room for improvement. The efficiency of the NOx conversion is highly dependent on the size of UWS droplets and their spatial distribution. These factors are, in turn, mainly determined by the spray characteristics and its interaction with the exhaust gas flow. The main purpose of this study is to numerically investigate the sensitivity to the modelling framework of the evaporation and mixing of the spray upstream of the catalyst. The dynamics of discrete droplets is handled through the Lagrangian Particle Tracking framework, with models that account for droplet breakup and coalescence, turbulence effects, and water evaporation. All simulations have been run in the commercial code Ansys Fluent 16.0. Experimental validation of droplet size distribution is carried out through PDPA measurements. Through the present study we have identified suitable modelling setup that provides accurate results with a competitive computational cost. Results also show the importance of accounting for the effects of evaporation and turbulent fluctuations in the droplet phase.

Place, publisher, year, edition, pages
SAE International, 2017
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-216544 (URN)10.4271/2017-01-0964 (DOI)2-s2.0-85018420204 (Scopus ID)
Conference
4 April 2017 through 6 April 2017
Note

QC 20171108

Available from: 2017-11-08 Created: 2017-11-08 Last updated: 2017-11-08Bibliographically approved
Olin, L., Altimira, M., Danielsson, J. & Rosén, A. (2017). Numerical modelling of spray sheet deflection on planing hulls. Journal of Engineering for the Maritime Environment (Part M), 231(4), 811-817
Open this publication in new window or tab >>Numerical modelling of spray sheet deflection on planing hulls
2017 (English)In: Journal of Engineering for the Maritime Environment (Part M), ISSN 1475-0902, E-ISSN 2041-3084, Vol. 231, no 4, p. 811-817Article in journal (Refereed) Published
Abstract [en]

This paper considers the modelling of spray formation on planing hulls. The focus is on assessing the applicability of the prevailing theories and two-dimensional and three-dimensional Computational Fluid Dynamics (CFD) simulations in the investigation of different design factors for a novel spray deflection concept. The spray deflection concept is presented and its performance is evaluated by comparison with traditional spray rails. It is found that the prevailing theory where the spray field of a planing hull is represented by a two-dimensional flat planing plate will overestimate the spray thickness, whereas the theories that are based on wedge impact are correlating well with the results from the CFD simulations. Compared to a bare hull, adding spray deflectors reduces the viscous resistance by 28% for the studied cases. The spray deflectors further redirect the spray aftwards which reduce the total drag an additional 4%. The paper also discusses various aspects on CFD modelling of spray formation.

Place, publisher, year, edition, pages
SAGE PUBLICATIONS LTD, 2017
Keywords
Planing hulls, spray formation, spray deflection, resistance reduction, CFD
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-217735 (URN)10.1177/1475090216682838 (DOI)000414468700001 ()2-s2.0-85032952538 (Scopus ID)
Note

QC 20171122

Available from: 2017-11-22 Created: 2017-11-22 Last updated: 2017-11-22Bibliographically approved
Altimira, M. & Casanueva, C. (2017). RAISING AWARENESS ON DIVERSITY AND EQUALITY IN STEM DEGREES IN HIGHER EDUCATION. In: Chova, LG Martinez, AL Torres, IC (Ed.), INTED2017: 11TH INTERNATIONAL TECHNOLOGY, EDUCATION AND DEVELOPMENT CONFERENCE. Paper presented at 11th International Conference on Technology, Education and Development (INTED), MAR 06-08, 2017, Valencia, SPAIN (pp. 1037-1041). IATED-INT ASSOC TECHNOLOGY EDUCATION A& DEVELOPMENT
Open this publication in new window or tab >>RAISING AWARENESS ON DIVERSITY AND EQUALITY IN STEM DEGREES IN HIGHER EDUCATION
2017 (English)In: INTED2017: 11TH INTERNATIONAL TECHNOLOGY, EDUCATION AND DEVELOPMENT CONFERENCE / [ed] Chova, LG Martinez, AL Torres, IC, IATED-INT ASSOC TECHNOLOGY EDUCATION A& DEVELOPMENT , 2017, p. 1037-1041Conference paper, Published paper (Refereed)
Abstract [en]

Higher education environments are becoming more and more diverse, regarding both gender and cultural background, which could pose significant challenges for both students and teachers. In order to raise the topic amongst STEM students, a lecture on Diversity has been implemented in the course Research Methodologies for Engineering Mechanics, where different concepts regarding equality have been introduced and unconscious bias have been explained to the students. The lecture was placed in the middle of the course so that students could reflect back on their previous evaluations and enable them to correct their biases in the second half of the course. Feedback of the whole course has also been compared between the 2016 and 2015 editions, where this lecture was not present. The results show that a lecture in Diversity and Equality is especially useful for female students, strongly supporting its inclusion in the course.

Place, publisher, year, edition, pages
IATED-INT ASSOC TECHNOLOGY EDUCATION A& DEVELOPMENT, 2017
Series
INTED Proceedings, ISSN 2340-1079
Keywords
higher education, diversity and equality, homosociality, unconscious bias, STEM
National Category
Educational Sciences
Identifiers
urn:nbn:se:kth:diva-217957 (URN)000413668601018 ()978-84-617-8491-2 (ISBN)
Conference
11th International Conference on Technology, Education and Development (INTED), MAR 06-08, 2017, Valencia, SPAIN
Note

QC 20171121

Available from: 2017-11-21 Created: 2017-11-21 Last updated: 2017-11-24Bibliographically approved
Altimira, M. & Fuchs, L. (2014). Effect of fuel flexibility on cavitation in injector-like flows. In: Proceedings of the 26th ILASS-Europe 2014: . Paper presented at 26th ILASS-Europe 2014, in Bremen.
Open this publication in new window or tab >>Effect of fuel flexibility on cavitation in injector-like flows
2014 (English)In: Proceedings of the 26th ILASS-Europe 2014, 2014Conference paper, Published paper (Refereed)
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-159899 (URN)
Conference
26th ILASS-Europe 2014, in Bremen
Note

QC 20150211

Available from: 2015-02-11 Created: 2015-02-11 Last updated: 2015-02-11Bibliographically approved
Nygård, A., Prahl Wittberg, L., Altimira, M. & Fuchs, L. (2014). Interaction between liquid pulses during intermittent injection. In: Proceedings of the 26th ILASS-Europe 2014: . Paper presented at 26th ILASS-Europe 2014; Bremen, Germany, 08/09/2014 - 10/09/2014.
Open this publication in new window or tab >>Interaction between liquid pulses during intermittent injection
2014 (English)In: Proceedings of the 26th ILASS-Europe 2014, 2014Conference paper, Published paper (Refereed)
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-159897 (URN)
Conference
26th ILASS-Europe 2014; Bremen, Germany, 08/09/2014 - 10/09/2014
Note

NQC  2015

Available from: 2015-02-11 Created: 2015-02-11 Last updated: 2016-05-04Bibliographically approved
Nygård, A., Altimira, M., Prahl Wittberg, L. & Fuchs, L. (2014). Quantifying primary breakup in pulsating liquid. In: A. Eriksson, A. Kulachenko, M. Mihaescu and G. Tibert (Ed.), : . Paper presented at 27th Nordic Seminar on Computational Mechanics; Stockholm, Sweden, October 22-24, 2014.
Open this publication in new window or tab >>Quantifying primary breakup in pulsating liquid
2014 (English)In: / [ed] A. Eriksson, A. Kulachenko, M. Mihaescu and G. Tibert, 2014Conference paper, Oral presentation with published abstract (Refereed)
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-159959 (URN)
Conference
27th Nordic Seminar on Computational Mechanics; Stockholm, Sweden, October 22-24, 2014
Note

QC 20150330

Available from: 2015-02-12 Created: 2015-02-12 Last updated: 2015-03-30Bibliographically approved
Altimira, M., Rivas, A., Ramos, J. C. & Anton, R. (2012). On The Disintegration Of Fan-Shaped Liquid Sheets. Atomization and sprays, 22(9), 733-755
Open this publication in new window or tab >>On The Disintegration Of Fan-Shaped Liquid Sheets
2012 (English)In: Atomization and sprays, ISSN 1044-5110, E-ISSN 1936-2684, Vol. 22, no 9, p. 733-755Article in journal (Refereed) Published
Abstract [en]

This paper presents a combined experimental and theoretical investigation of the disintegration of fan-shaped liquid sheets produced by industrial fan-spray atomizers. The disintegration regimes observed for different geometries and operating conditions are described, proving the paramount role of nozzle flow on the final characteristics of the spray produced. The concept of breakup length is redefined to account for the stochastic nature of liquid stream disintegration. An analogy is established between the breakup of a liquid sheet dominated by the wave mode and a radial sheet, obtaining good agreement with the experiments. However, in those cases where several disintegration regimes coexist, the breakup length cannot be given by an analytical expression. Finally, the influence of the disintegration regime on both the droplet size and the spatial distribution of the droplets is investigated, confirming the strong influence of rim breakup.

Keywords
atomization, experimental characterization, visualization techniques, liquid sheet, primary breakup, rim breakup
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-119426 (URN)10.1615/AtomizSpr.2012006220 (DOI)000315170100002 ()2-s2.0-84874916787 (Scopus ID)
Note

QC 20130314

Available from: 2013-03-14 Created: 2013-03-14 Last updated: 2017-12-06Bibliographically approved
Altimira, M., Rivas, A., Ramos, J. C. & Anton, R. (2011). Disintegration regime of industrial fan-spray atomizers through CFD simulations. In: ILASS – Europe 2011, 24th European Conference on Liquid Atomization and Spray Systems, Estoril, Portugal, September 2011. Paper presented at ILASS – Europe 2011.
Open this publication in new window or tab >>Disintegration regime of industrial fan-spray atomizers through CFD simulations
2011 (English)In: ILASS – Europe 2011, 24th European Conference on Liquid Atomization and Spray Systems, Estoril, Portugal, September 2011, 2011Conference paper, Published paper (Refereed)
Abstract [en]

Among all the literature devoted to the investigation of sprays, very few works deal with the influence of the nozzle’s geometry on the characteristics of the spray produced, even though it has been proved to play a crucial role in certain operating regimes. The present paper presents criteria for the determination of the dominant disintegration regime in industrial fan-spray atomizers through CFD simulations accounting for the atomizer’s geometry.

National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-78485 (URN)
Conference
ILASS – Europe 2011
Note
QC 20120214Available from: 2012-02-14 Created: 2012-02-08 Last updated: 2012-02-14Bibliographically approved
Altimira, M. (2010). Analysis of Atomization Systems through Mathematical Modeling and Experimentation: Application to Industrial Fan-Spray Atomizers. (Doctoral dissertation). University of Navarra
Open this publication in new window or tab >>Analysis of Atomization Systems through Mathematical Modeling and Experimentation: Application to Industrial Fan-Spray Atomizers
2010 (English)Doctoral thesis, monograph (Other academic)
Place, publisher, year, edition, pages
University of Navarra, 2010. p. 272
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-78497 (URN)
Public defence
(English)
Supervisors
Note
QC 20120208Available from: 2012-02-08 Created: 2012-02-08 Last updated: 2012-02-08Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-6242-4739

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