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Prahl Wittberg, Lisa, DocentORCID iD iconorcid.org/0000-0001-9976-8316
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Publications (10 of 60) Show all publications
Berg, N., Fuchs, L. & Prahl Wittberg, L. (2019). Blood Flow Simulations of the Renal Arteries - Effect of Segmentation and Stenosis Removal. Flow Turbulence and Combustion, 102(1), 27-41
Open this publication in new window or tab >>Blood Flow Simulations of the Renal Arteries - Effect of Segmentation and Stenosis Removal
2019 (English)In: Flow Turbulence and Combustion, ISSN 1386-6184, E-ISSN 1573-1987, Vol. 102, no 1, p. 27-41Article in journal (Refereed) Published
Abstract [en]

Patient specific based simulation of blood flows in arteries has been proposed as a future approach for better diagnostics and treatment of arterial diseases. The outcome of theoretical simulations strongly depends on the accuracy in describing the problem (the geometry, material properties of the artery and of the blood, flow conditions and the boundary conditions). In this study, the uncertainties associated with the approach for a priori assessment of reconstructive surgery of stenoted arteries are investigated. It is shown that strong curvature in the reconstructed artery leads to large spatial- and temporal-peaks in the wall shear-stress. Such peaks can be removed by appropriate reconstruction that also handles the post-stenotic dilatation of the artery. Moreover, it is shown that the effects of the segmentation approach can be equally important as the effects of using advanced rheological models. This fact has not been recognized in the literature up to this point, making patient specific simulations potentially less reliable.

Place, publisher, year, edition, pages
SPRINGER, 2019
Keywords
Atherosclerotic indicators, Stenosis, Segmentation, Non-Newtonian, Hemodynamics, CFD
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-251230 (URN)10.1007/s10494-019-00009-z (DOI)000463881000003 ()2-s2.0-85061181367 (Scopus ID)
Note

QC 20190523

Available from: 2019-05-23 Created: 2019-05-23 Last updated: 2019-05-23Bibliographically approved
Berg, N., Fuchs, L. & Prahl Wittberg, L. (2019). Flow characteristics and coherent structures in a centrifugal blood pump. Flow Turbulence and Combustion, 102(2), 469-483
Open this publication in new window or tab >>Flow characteristics and coherent structures in a centrifugal blood pump
2019 (English)In: Flow Turbulence and Combustion, ISSN 1386-6184, E-ISSN 1573-1987, Vol. 102, no 2, p. 469-483Article in journal (Refereed) Published
Abstract [en]

Blood clot formation can be initiated by local flow conditions where regions of high shear and long residence time regions, such as flow separation and stagnation, have been identified as risk factors. This study highlights coherent structures,some of which not yet considered in the literature that may contribute to blood clot formation in the ECMO (Extra Corporeal Membrane Oxygenator) circuit. The centrifugal ECMO pump investigated in this study is compact and delivers adequate volume of blood with relatively high pressure in order to compensate for the large pressure drop in the membrane oxygenator. These requirements lead to regions with high shear in several different parts of the pump. In the narrow gap between the pump house and the impeller body (the magnet) a Taylor-Couette-like flow is observed with azimuthally aligned wavy vortices, which are also pushed towards the bottom of the pump-house by the flow generated by the blades. At the bottom gap between the impeller house and the pump house one finds spiraling flow structures, due to the rotation of the former structure. Separation bubbles are found near the tongue of the pump and at the lee sides of the blades. Such vortical structures have in literature been identified as regions where platelets may be activated whereby clots may develop.

Place, publisher, year, edition, pages
Springer Nature, 2019
Keywords
Coherent structures, Blood flow, ECMO, Centrifugal pump, CFD
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-239059 (URN)10.1007/s10494-018-9994-3 (DOI)000465588800014 ()2-s2.0-85058486537 (Scopus ID)
Note

QC 20181116

Available from: 2018-11-15 Created: 2018-11-15 Last updated: 2019-07-09Bibliographically approved
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
Fuchs, G., Berg, N., Broman, M. & Prahl Wittberg, L. (2019). Modeling sensitivity and uncertainties in platelet activation models applied on centrifugal pumps for extracorporeal life support. Scientific Reports, 9, Article ID 8809.
Open this publication in new window or tab >>Modeling sensitivity and uncertainties in platelet activation models applied on centrifugal pumps for extracorporeal life support
2019 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 9, article id 8809Article in journal (Refereed) Published
National Category
Applied Mechanics
Identifiers
urn:nbn:se:kth:diva-239061 (URN)10.1038/s41598-019-45121-2 (DOI)000472030000042 ()2-s2.0-85067567435 (Scopus ID)
Note

QC 20181116

Available from: 2018-11-15 Created: 2018-11-15 Last updated: 2019-07-29Bibliographically approved
Broman, L. M., Prahl Wittberg, L., Westlund, C. J., Gilbers, M., da Camara, L. P., Swol, J., . . . Lorusso, R. (2019). Pressure and flow properties of cannulae for extracorporeal membrane oxygenation I: return (arterial) cannulae. Paper presented at 8th Euro-ELSO Congress (EuroELSO), APR 10-13, 2019, Barcelona, SPAIN. Perfusion, 34, 58-64
Open this publication in new window or tab >>Pressure and flow properties of cannulae for extracorporeal membrane oxygenation I: return (arterial) cannulae
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2019 (English)In: Perfusion, ISSN 0267-6591, E-ISSN 1477-111X, Vol. 34, p. 58-64Article in journal (Refereed) Published
Abstract [en]

Adequate extracorporeal membrane oxygenation support in the adult requires cannulae permitting blood flows up to 6-8 L/minute. In accordance with Poiseuille's law, flow is proportional to the fourth power of cannula inner diameter and inversely proportional to its length. Poiseuille's law can be applied to obtain the pressure drop of an incompressible, Newtonian fluid (such as water) flowing in a cylindrical tube. However, as blood is a pseudoplastic non-Newtonian fluid, the validity of Poiseuille's law is questionable for prediction of cannula properties in clinical practice. Pressure-flow charts with non-Newtonian fluids, such as blood, are typically not provided by the manufacturers. A standardized laboratory test of return (arterial) cannulae for extracorporeal membrane oxygenation was performed. The aim was to determine pressure-flow data with human whole blood in addition to manufacturers' water tests to facilitate an appropriate choice of cannula for the desired flow range. In total, 14 cannulae from three manufacturers were tested. Data concerning design, characteristics, and performance were graphically presented for each tested cannula. Measured blood flows were in most cases 3-21% lower than those provided by manufacturers. This was most pronounced in the narrow cannulae (15-17 Fr) where the reduction ranged from 27% to 40% at low flows and 5-15% in the upper flow range. These differences were less apparent with increasing cannula diameter. There was a marked disparity between manufacturers. Based on the measured results, testing of cannulae including whole blood flows in a standardized bench test would be recommended.

Place, publisher, year, edition, pages
SAGE PUBLICATIONS LTD, 2019
Keywords
arterial, return, extracorporeal membrane oxygenation, cannula, pressure flow, blood, water, extracorporeal life support
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-251340 (URN)10.1177/0267659119830521 (DOI)000464422000008 ()30966910 (PubMedID)2-s2.0-85064316040 (Scopus ID)
Conference
8th Euro-ELSO Congress (EuroELSO), APR 10-13, 2019, Barcelona, SPAIN
Note

QC 20190521

Available from: 2019-05-21 Created: 2019-05-21 Last updated: 2019-05-21Bibliographically approved
Broman, L. M., Prahl Wittberg, L., Westlund, C. J., Gilbers, M., da Camara, L. P., Westin, J., . . . Lorusso, R. (2019). Pressure and flow properties of cannulae for extracorporeal membrane oxygenation II: drainage (venous) cannulae. Paper presented at 8th Euro-ELSO Congress (EuroELSO), APR 10-13, 2019, Barcelona, SPAIN. Perfusion, 34, 65-73
Open this publication in new window or tab >>Pressure and flow properties of cannulae for extracorporeal membrane oxygenation II: drainage (venous) cannulae
Show others...
2019 (English)In: Perfusion, ISSN 0267-6591, E-ISSN 1477-111X, Vol. 34, p. 65-73Article in journal (Refereed) Published
Abstract [en]

The use of extracorporeal life support devices such as extracorporeal membrane oxygenation in adults requires cannulation of the patient's vessels with comparatively large diameter cannulae to allow circulation of large volumes of blood (>5 L/min). The cannula diameter and length are the major determinants for extracorporeal membrane oxygenation flow. Manufacturing companies present pressure-flow charts for the cannulae; however, these tests are performed with water. Aims of this study were 1. to investigate the specified pressure-flow charts obtained when using human blood as the circulating medium and 2. to support extracorporeal membrane oxygenation providers with pressure-flow data for correct choice of the cannula to reach an optimal flow with optimal hydrodynamic performance. Eighteen extracorporeal membrane oxygenation drainage cannulae, donated by the manufacturers (n = 6), were studied in a centrifugal pump driven mock loop. Pressure-flow properties and cannula features were described. The results showed that when blood with a hematocrit of 27% was used, the drainage pressure was consistently higher for a given flow (range 10%-350%) than when water was used (data from each respective manufacturer's product information). It is concluded that the information provided by manufacturers in line with regulatory guidelines does not correspond to clinical performance and therefore may not provide the best guidance for clinicians.

Place, publisher, year, edition, pages
SAGE PUBLICATIONS LTD, 2019
Keywords
drainage, cannula, pressure, flow, extracorporeal membrane oxygenation, extracorporeal, life support, venous
National Category
Basic Medicine
Identifiers
urn:nbn:se:kth:diva-251339 (URN)10.1177/0267659119830514 (DOI)000464422000009 ()30966909 (PubMedID)2-s2.0-85064320258 (Scopus ID)
Conference
8th Euro-ELSO Congress (EuroELSO), APR 10-13, 2019, Barcelona, SPAIN
Note

QC 20190523

Available from: 2019-05-23 Created: 2019-05-23 Last updated: 2019-05-23Bibliographically approved
Fuchs, A., Berg, N. & Prahl Wittberg, L. (2019). Stenosis Indicators Applied to Patient-Specific Renal Arteries without and with Stenosis. FLUIDS, 4(1), Article ID 26.
Open this publication in new window or tab >>Stenosis Indicators Applied to Patient-Specific Renal Arteries without and with Stenosis
2019 (English)In: FLUIDS, ISSN 2311-5521, Vol. 4, no 1, article id 26Article in journal (Refereed) Published
Abstract [en]

Pulsatile flow in the abdominal aorta and the renal arteries of three patients was studied numerically. Two of the patients had renal artery stenosis. The aim of the study was to assess the use of four types of indicators for determining the risk of new stenosis after revascularization of the affected arteries. The four indicators considered include the time averaged wall shear stress (TAWSS), the oscillatory shear index (OSI), the relative reference time (RRT) and a power law model based in platelet activation modeling but applied to the endothelium, named endothelium activation indicator (EAI). The results show that the indicators can detect the existing stenosis but are less successful in the revascularized cases. The TAWSS and, more clearly, the EAI approach seem to be better in predicting the risk for stenosis relapse at the original location and close to the post-stenotic dilatation. The shortcomings of the respective indicators are discussed along with potential improvements to endothelial activation modeling and its use as an indicator for risks of restenosis.

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
renal artery stenosis, blood flow simulation, atherosclerosis, reconstructed arteries, stenosis indicators
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-251364 (URN)10.3390/fluids4010026 (DOI)000464457900001 ()2-s2.0-85063386762 (Scopus ID)
Note

QC 20190513

Available from: 2019-05-13 Created: 2019-05-13 Last updated: 2019-05-23Bibliographically approved
Lacagnina, G., Szász, R.-Z., Prahl Wittberg, L. & Fuchs, L. (2018). Experimental study on the forcing design for an intermittent injection. Experiments in Fluids, 59(8), Article ID 123.
Open this publication in new window or tab >>Experimental study on the forcing design for an intermittent injection
2018 (English)In: Experiments in Fluids, ISSN 0723-4864, E-ISSN 1432-1114, Vol. 59, no 8, article id 123Article in journal (Refereed) Accepted
Abstract [en]

In this paper we consider the effects of acceleration and deceleration on the forcing of an intermittent jet. This experimental study specifically focuses on the effect of the acceleration and deceleration on the mixing of an intermittent jet with the ambient fluid and on the growth of disturbances that may lead to turbulence. The influence of different injection strategies has been evaluated. The results show that the deceleration phase may be able to contribute significantly to enhance the mixing of the jet with the ambient fluid. This effect is manifested primarily around the tail of the jet, towards the end of injection. The acceleration phase on the other hand has mainly impact at the leading part of the jet, where the leading part of the jet forms a mushroom shaped structure with minor mixing effect.

Place, publisher, year, edition, pages
Springer, 2018
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-231138 (URN)10.1007/s00348-018-2574-4 (DOI)000437308700001 ()2-s2.0-85049526339 (Scopus ID)
Funder
Swedish Research Council
Note

QC 20180626

Available from: 2018-06-22 Created: 2018-06-22 Last updated: 2019-01-28Bibliographically approved
Fuchs, G., Berg, N., Broman, M. & Prahl Wittberg, L. (2017). Blood clots in the ECMO-system - a theoretical platelet activation study. Acta Anaesthesiologica Scandinavica, 61(8), 964-965
Open this publication in new window or tab >>Blood clots in the ECMO-system - a theoretical platelet activation study
2017 (English)In: Acta Anaesthesiologica Scandinavica, ISSN 0001-5172, E-ISSN 1399-6576, Vol. 61, no 8, p. 964-965Article in journal, Meeting abstract (Other academic) Published
Place, publisher, year, edition, pages
Wiley, 2017
National Category
Anesthesiology and Intensive Care
Identifiers
urn:nbn:se:kth:diva-243510 (URN)000407231100018 ()
Note

QC 20190211

Available from: 2019-02-11 Created: 2019-02-11 Last updated: 2019-02-11Bibliographically approved
Nygård, A., Altimira, M., Semlitsch, B., Prahl Wittberg, L. & Fuchs, L. (2016). Analysis of vortical structures in intermittent jets. In: Springer Proceedings in Physics: . Paper presented at 5th International Conference on Jets, Wakes and Separated Flows, ICJWSF2015, 15 June 2015 through 18 June 2015 (pp. 3-10). Springer Science+Business Media B.V.
Open this publication in new window or tab >>Analysis of vortical structures in intermittent jets
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2016 (English)In: Springer Proceedings in Physics, Springer Science+Business Media B.V., 2016, p. 3-10Conference paper, Published paper (Refereed)
Abstract [en]

The manipulation of jets has since long been subject to research, due to the wide range of industrial applications in which they are used. A vast number of numerical and experimental studies concerning the physics of the breakup process of continuous jets have been published. Improvements in mixing and ambient gas entrainment have been reported experimentally when using intermittent injection, although the responsible mechanisms have not yet been completely revealed. This work presents a systematic analysis of the mechanisms of jet breakup and mixing with the surrounding fluid and its relation to vorticity generation and transport. Comparisons aremade between the redistribution of vorticity and the engulfment of ambient fluid into the core region for different injection strategies. © Springer International Publishing Switzerland 2016.

Place, publisher, year, edition, pages
Springer Science+Business Media B.V., 2016
Keywords
Industrial research, Mixing, Transport properties, Vorticity, Wakes, Ambient fluids, Ambient gas, Continuous jets, Intermittent injection, Numerical and experimental study, Systematic analysis, Vortical structures, Vorticity generation, Fighter aircraft
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-195137 (URN)10.1007/978-3-319-30602-5_1 (DOI)000387431400001 ()2-s2.0-84978998403 (Scopus ID)9783319306001 (ISBN)
Conference
5th International Conference on Jets, Wakes and Separated Flows, ICJWSF2015, 15 June 2015 through 18 June 2015
Note

Correspondence Address: Nygård, A.; Department of Mechanics, KTHSweden; email: alexander@mech.kth.se. QC 20161116

Available from: 2016-11-16 Created: 2016-11-02 Last updated: 2019-01-28Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0001-9976-8316

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