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Westerberg, Lars-GöranORCID iD iconorcid.org/0000-0001-5294-1855
Publications (10 of 81) Show all publications
Schillings, A., Slapak, R., Nilsson, H., Yamauchi, M., Dandouras, I. & Westerberg, L.-G. (2019). Earth atmospheric loss through the plasma mantle and its dependence on solar wind parameters. Earth, Planets and Space, 71(70)
Open this publication in new window or tab >>Earth atmospheric loss through the plasma mantle and its dependence on solar wind parameters
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2019 (English)In: Earth, Planets and Space, Vol. 71, no 70Article in journal (Refereed) Published
Abstract [en]

Atmospheric loss and ion outfow play an important role in the magnetospheric dynamics and in the evolution of the atmosphere on geological timescales—an evolution which is also dependent on the solar activity. In this paper, we investigate the total O+ outfow [s−1 ] through the plasma mantle and its dependency on several solar wind param‑ eters. The oxygen ion data come from the CODIF instrument on board the spacecraft Cluster 4 and solar wind data from the OMNIWeb database for a period of 5 years (2001–2005). We study the distribution of the dynamic pressure and the interplanetary magnetic feld for time periods with available O+ observations in the plasma mantle. We then divided the data into suitably sized intervals. Additionally, we analyse the extreme ultraviolet radiation (EUV) data from the TIMED mission. We estimate the O+ escape rate [ions/s] as a function of the solar wind dynamic pressure, the interplanetary magnetic feld (IMF) and EUV. Our analysis shows that the O+ escape rate in the plasma mantle increases with increased solar wind dynamic pressure. Consistently, it was found that the southward IMF also plays an important role in the O+ escape rate in contrast to the EUV fux which does not have a signifcant infuence for the plasma mantle region. Finally, the relation between the O+ escape rate and the solar wind energy transferred into the magnetosphere shows a nonlinear response. The O+ escape rate starts increasing with an energy input of approxi‑ mately 1011W.

Place, publisher, year, edition, pages
Springer, 2019
Keywords
O+ outfow/escape, Plasma mantle, Solar wind, Interplanetary magnetic feld (IMF), Extreme ultraviolet (EUV), Coupling functions
National Category
Aerospace Engineering Fluid Mechanics and Acoustics
Research subject
Atmospheric science; Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-74886 (URN)10.1186/s40623-019-1048-0 (DOI)000472492500001 ()2-s2.0-85067844890 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-08-15 (johcin)

Available from: 2019-06-24 Created: 2019-06-24 Last updated: 2019-08-15Bibliographically approved
Schillings, A., Slapak, R., Nilsson, H., Yamauchi, M., Dandouras, I. & Westerberg, L.-G. (2019). Earth atmospheric loss through the plasma mantle and its dependence onsolar wind parameters. In: : . Paper presented at EGU General Assembly 2019, 7–12 April 2019, Vienna, Austria.
Open this publication in new window or tab >>Earth atmospheric loss through the plasma mantle and its dependence onsolar wind parameters
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2019 (English)Conference paper (Refereed)
National Category
Aerospace Engineering Fluid Mechanics and Acoustics
Research subject
Atmospheric science; Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-73466 (URN)
Conference
EGU General Assembly 2019, 7–12 April 2019, Vienna, Austria
Available from: 2019-04-05 Created: 2019-04-05 Last updated: 2019-04-05Bibliographically approved
Hamedi, N. & Westerberg, L.-G. (2019). Modelling of Flexible Fibres in Viscous Fluid Flow. In: : . Paper presented at IWNMNNF 2019, 19th International Workshop on Numerical Methods for Non-Newtonian Flows, Peso da Régua, Portugal, June 16 - 20th.
Open this publication in new window or tab >>Modelling of Flexible Fibres in Viscous Fluid Flow
2019 (English)Conference paper, Oral presentation with published abstract (Refereed)
Abstract [en]

The current study relates to the development of a multiphase model of flexible fibre suspensions. An understanding of the rheology and dynamics of the deformation of such suspension is desirable in order to be able to fully disclose the flow behaviour from very low to very high shear rates. We present an approach for numerically simulating the dynamics of flexible fibres employing a particle-level method. This is performed by investigating the fibre dynamics against several orbit classes - i.e. rigid, springy, flexible and complex rotation of the fibres [1-3] enabling the model to have all degrees of freedom (translation, rotation, bending and twisting). The three-dimensional Navier-Stokes equations which describes the fluid motion are employed while the fibrous phase of the fluid is modeled as chains of fiber segments interacting with the fluid through viscous- and drag forces. The simulations are performed using OpenFOAM and the numerical outcomes are validated against experimental data.The purpose of the modelling framework applied in this work is to enable the numerical model to be extended to a 4-way coupling model, capturing shear thinning, shear thickening and the yield stress properties of a fibrous fluid suspension.

National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-74058 (URN)
Conference
IWNMNNF 2019, 19th International Workshop on Numerical Methods for Non-Newtonian Flows, Peso da Régua, Portugal, June 16 - 20th
Available from: 2019-05-29 Created: 2019-05-29 Last updated: 2019-05-29Bibliographically approved
Westerberg, L.-G. (2019). MR-fluid Technology for Reduced Wear in Windturbine Bearings. In: : . Paper presented at STLE Annual Meeting, Nashville, Tennessee, USA, 19-23 May.
Open this publication in new window or tab >>MR-fluid Technology for Reduced Wear in Windturbine Bearings
2019 (English)Conference paper, Oral presentation with published abstract (Refereed)
Abstract [en]

Magnetorheology (MR) is a technology to enable active control of the viscosity of a material - typically afluid, but also semi-solid materials such as lubricating greases. Magnetic particles of nano to micron scale aremixed with the fluid and when subjected to a magnetic field the particles are aligned with the field, inducing ashear resistance - i.e. the effect of an increased viscosity - if applied in appropriate direction. This technology isfor example used in active dampers in sports cars, where electromagnets activated by a sensor systemcontrols the viscosity of the damper oil and the pressure in the dampers. This paper proposes a method ofusing MR technology to reduce wear in wind turbine bearings by enhancing the lubricant film in the maximumHertzian contact. Electromagnets are used to control the sequence of demagnetization and magnetization ofthe lubricant. Here the wear particles existing in the lubricant acts as guiding particles.

Keywords
Applied Tribology:Power Generation, Lubricants:Ferrofluids
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-74087 (URN)
Conference
STLE Annual Meeting, Nashville, Tennessee, USA, 19-23 May
Available from: 2019-05-29 Created: 2019-05-29 Last updated: 2019-05-29Bibliographically approved
Karami, F., Nadooshan, A. A., Westerberg, L.-G. & Tadi Beni, Y. (2019). Nano-fluid flow in a catheterized tapered artery: Consistent couple stress-theory and wall slip. Journal of thermal analysis and calorimetry (Print), 137(1), 327-342
Open this publication in new window or tab >>Nano-fluid flow in a catheterized tapered artery: Consistent couple stress-theory and wall slip
2019 (English)In: Journal of thermal analysis and calorimetry (Print), ISSN 1388-6150, E-ISSN 1588-2926, Vol. 137, no 1, p. 327-342Article in journal (Refereed) Published
Abstract [en]

This study was conducted with the aim of investigating the Newtonian nanofluid flow in a catheterized tapered artery through using a completely consistent couple stress theory. In the process of carrying out this study, the slip condition at the arterial wall and the catheter, as well as, the permeability was taken into account. Further, the velocity, temperature, and concentration profiles were analytically modeled and the effect of the length scale on these profiles was well presented through the way it influences small-scale flows. The effect of the slip condition at the artery and catheter walls on the velocity was also investigated and revealed that any increase in the velocity leads to an increase in the slip velocity. Furthermore, the effect of other parameters such as the catheter diameter, shape, and height of the stenosis on these profiles was explored for all three artery geometries, i.e., diverging tapered artery, converging tapered artery, and non-tapered artery, respectively. The findings suggested that any increase in the catheter diameter and stenosis height can decrease the velocity and nanoparticle concentration profiles, while the temperature profile increases. It was also found that by increasing the stenosis shape parameter the velocity and concentration profiles increase and temperature decreases.

Place, publisher, year, edition, pages
Springer, 2019
Keywords
Catheterized artery, Couple stress, Nanofluid, Slip velocity, Galerkin method
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-71601 (URN)10.1007/s10973-018-7930-3 (DOI)000470338100029 ()
Note

Validerad;2019;Nivå 2;2019-07-01 (johcin)

Available from: 2018-11-15 Created: 2018-11-15 Last updated: 2019-07-01Bibliographically approved
Hamedi, N. & Westerberg, L.-G. (2019). On the Interaction of Side-By-Side Circular Cylinders in Viscoplastic Fluids. Fluids, 4(2), Article ID 93.
Open this publication in new window or tab >>On the Interaction of Side-By-Side Circular Cylinders in Viscoplastic Fluids
2019 (English)In: Fluids, ISSN 2311-5521, Vol. 4, no 2, article id 93Article in journal (Refereed) Published
Abstract [en]

In this paper, the static interaction of a train of three cylinders in a Bingham fluid is studiednumerically using Computational Fluid Dynamics. The variation of drag forces for the cylinders inseveral configurations is investigated. Positions of the particles in relation to the reference particleare recognized by the separation distance between the cylinders. A steady state field is considered,with Bingham numbers between 5 and 150. Several separation distances (d) were considered, such that2.0D d 6.0D where D is the cylinder diameter. The Reynolds number was chosen in the range of5 Re 40. In particular, the eect of the separation distance, Reynolds number and Bingham numberon the shape and size of the unyielded regions was investigated. The functional dependence of thisregion and the drag coecient is explored. The present results reveal the significant influence of thegap between the cylinders on the drag force and the shape of the unyielded regions surrounding thecylinders. It was found that there are several configurations in which the drag forces over the first andthe third cylinders are almost equal depending on variation of the Bi, Re and the separation distance.

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
particle interaction, viscoplastic fluid, Bingham fluid, computational fluid dynamics
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-74059 (URN)10.3390/fluids4020093 (DOI)000475331700035 ()2-s2.0-85069779541 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-05-27 (oliekm)

Available from: 2019-05-27 Created: 2019-05-27 Last updated: 2019-08-21Bibliographically approved
Slapak, R., Schillings, A., Nilsson, H., Yamauchi, M. & Westerberg, L.-G. (2018). Corrigendum to Atmospheric loss from the dayside open polar region and its dependence on geomagnetic activity: Implications for atmospheric escape on evolutionary time scales, published in Ann. Geophys., 35, 721–731,2017 [Letter to the editor]. Annales Geophysicae
Open this publication in new window or tab >>Corrigendum to Atmospheric loss from the dayside open polar region and its dependence on geomagnetic activity: Implications for atmospheric escape on evolutionary time scales, published in Ann. Geophys., 35, 721–731,2017
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2018 (English)In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576Article in journal, Letter (Refereed) Published
Place, publisher, year, edition, pages
Copernicus Publications, 2018
National Category
Aerospace Engineering Fluid Mechanics and Acoustics
Research subject
Atmospheric science; Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-68587 (URN)10.5194/angeo-35-721-2017-corrigendum (DOI)
Available from: 2018-05-02 Created: 2018-05-02 Last updated: 2018-11-20Bibliographically approved
Duenas Dobrowolski, J., Gawlinski, M., Paszkowski, M., Westerberg, L.-G. & Höglund, E. (2018). Experimental Study of Lubricating Grease Flow inside the Gap of a Labyrinth Seal Using Microparticle Image Velocimetry. Tribology Transactions, 61(1), 31-40
Open this publication in new window or tab >>Experimental Study of Lubricating Grease Flow inside the Gap of a Labyrinth Seal Using Microparticle Image Velocimetry
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2018 (English)In: Tribology Transactions, ISSN 1040-2004, E-ISSN 1547-397X, Vol. 61, no 1, p. 31-40Article in journal (Refereed) Published
Abstract [en]

In this study, the flow of lubricating greases in a labyrinth seal geometry is studied using microparticle image velocimetry (µPIV). The aim is to evaluate the grease velocity distribution inside the gap of a labyrinth seal and to find a relationship between the grease consistency and the transferred speed from the rotating ring in order to choose the correct grease as a sealing medium. In addition, the grease flow characteristics are important for the understanding of fracture due to grease layer displacement. For these purposes, four greases with different rheological properties were used in µPIV experiments. It was found that the grease consistency plays a crucial role in speed development as well as the grease composition and presence of a slip effect at the grease–rotating wall interface.

Place, publisher, year, edition, pages
Taylor & Francis, 2018
National Category
Fluid Mechanics and Acoustics Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Fluid Mechanics; Machine Elements
Identifiers
urn:nbn:se:ltu:diva-61056 (URN)10.1080/10402004.2016.1271928 (DOI)000432222500004 ()
Note

Validerad;2018;Nivå 2;2018-01-31 (rokbeg)

Available from: 2016-12-13 Created: 2016-12-13 Last updated: 2018-06-04Bibliographically approved
Sarkar, C., Westerberg, L.-G., Höglund, E. & Lundström, S. T. (2018). Numerical simulations of lubricating grease flow in a rectangular channel with and without restrictions. Tribology Transactions, 61(1), 144-156
Open this publication in new window or tab >>Numerical simulations of lubricating grease flow in a rectangular channel with and without restrictions
2018 (English)In: Tribology Transactions, ISSN 1040-2004, E-ISSN 1547-397X, Vol. 61, no 1, p. 144-156Article in journal (Refereed) Published
Abstract [en]

This article presents numerical simulations of the laminar flow of lubricating greases in a channel with rectangular cross section. Three greases with different consistencies (NLGI grades 00, 1, and 2) have been considered in three different configurations composed of a rectangular channel without restrictions, one rectangular step restriction, and one double-lip restriction. The driving pressure drop over the channel spans from 30 to 250 kPa. The grease rheology is described by the Herschel-Bulkley rheology model, and both the numerical code and rheology model have been validated with analytical solutions and flow measurements using micro-particle image velocimetry.

Place, publisher, year, edition, pages
Taylor & Francis, 2018
National Category
Fluid Mechanics and Acoustics Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Fluid Mechanics; Machine Elements
Identifiers
urn:nbn:se:ltu:diva-61479 (URN)10.1080/10402004.2017.1285090 (DOI)000432222500015 ()
Note

Validerad;2018;Nivå 2;2018-02-01 (rokbeg)

Available from: 2017-01-17 Created: 2017-01-17 Last updated: 2018-06-04Bibliographically approved
Schillings, A., Slapak, R., Nilsson, H., Yamauchi, M. & Westerberg, L.-G. (2017). Atmospheric loss during major geomagnetic storms: Cluster observations. In: : . Paper presented at European Geosciences Union General Assembly 2017, Vienna, Austria, 23-28 April 2017.
Open this publication in new window or tab >>Atmospheric loss during major geomagnetic storms: Cluster observations
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2017 (English)Conference paper, Oral presentation with published abstract (Refereed)
National Category
Fluid Mechanics and Acoustics Aerospace Engineering
Research subject
Fluid Mechanics; Atmospheric science
Identifiers
urn:nbn:se:ltu:diva-62336 (URN)
Conference
European Geosciences Union General Assembly 2017, Vienna, Austria, 23-28 April 2017
Available from: 2017-03-08 Created: 2017-03-08 Last updated: 2017-11-24Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-5294-1855

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