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Publications (10 of 96) Show all publications
Öhman, J., Sjödahl, M. & Gren, P. (2019). Polarization Resolved Dual-View Holographic System for Investigation of Microparticles. In: OSA Technical Digest (Optical Society of America, 2019): . Paper presented at Digital Holography and Three-Dimensional Imaging 2019. , Article ID Th2A.5.
Open this publication in new window or tab >>Polarization Resolved Dual-View Holographic System for Investigation of Microparticles
2019 (English)In: OSA Technical Digest (Optical Society of America, 2019), 2019, article id Th2A.5Conference paper, Oral presentation with published abstract (Refereed)
Abstract [en]

A dual-view polarization resolved digital-holographic system is presented. The necessary calibration for both polarization and spatial coordinates are outlined. As an example the system is is used to track spherical microparticles in a cuvette.

National Category
Atom and Molecular Physics and Optics
Research subject
Experimental Mechanics
Identifiers
urn:nbn:se:ltu:diva-76066 (URN)10.1364/DH.2019.Th2A.5 (DOI)
Conference
Digital Holography and Three-Dimensional Imaging 2019
Available from: 2019-09-19 Created: 2019-09-19 Last updated: 2019-09-19
Öhman, J., Gren, P. & Sjödahl, M. (2019). Polarization-resolved dual-view holographic system for 3D inspection of scattering particles. Applied Optics, 58(34), G31-G40
Open this publication in new window or tab >>Polarization-resolved dual-view holographic system for 3D inspection of scattering particles
2019 (English)In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 58, no 34, p. G31-G40Article in journal (Refereed) Published
Abstract [en]

A novel dual-view polarization-resolved pulsed holographic system for particle measurements is presented. Both dual-view configuration and polarization-resolved registration are well suited for particle holography. Dual-view registration improves the accuracy in the detection of 3D position and velocities, and polarization-resolved registration provides polarization information about individual particles. The necessary calibrations are presented, and aberrations are compensated for by mapping the positions in the two views to positions in a global coordinate system. The system is demonstrated on a sample consisting of 7 μm spherical polystyrene particles dissolved in water in a cuvette. The system is tested with different polarizations of the illumination. It is found that the dual view improves the accuracy significantly in particle tracking. It is also found that by having polarization-resolved holograms, it is possible to separate naturally occurring sub-micrometer particles from the larger, 7 μm seeding particles.

Place, publisher, year, edition, pages
The Optical Society, 2019
National Category
Atom and Molecular Physics and Optics Applied Mechanics
Research subject
Experimental Mechanics
Identifiers
urn:nbn:se:ltu:diva-76067 (URN)10.1364/AO.58.000G31 (DOI)
Funder
Swedish Research Council, 621-2014-4906
Note

Validerad;2019;Nivå 2;2019-09-23 (johcin)

Available from: 2019-09-19 Created: 2019-09-19 Last updated: 2019-09-23Bibliographically approved
Tóth, P., Ögren, Y., Sepma, A., Vikström, T., Gren, P. & Wiinikka, H. (2019). Spray combustion of biomass fast pyrolysis oil: Experiments and modeling. Fuel, 237, 580-591
Open this publication in new window or tab >>Spray combustion of biomass fast pyrolysis oil: Experiments and modeling
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2019 (English)In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 237, p. 580-591Article in journal (Refereed) Published
Abstract [en]

In this work, we are the first to report a detailed comparison between the predictions of a current Computational Fluid Dynamics (CFD) model for describing Fast Pyrolysis Oil (FPO) spray combustion and results from a laboratory-scale experiment. The objectives were to assess the predictive power of the CFD model, evaluate its usefulness in a numerical optimization scenario and characterize the spray flame. The spray flame was produced by using an air-assist atomizer piloted by a CH4" role="presentation" style="box-sizing: border-box; margin: 0px; padding: 0px; display: inline-block; line-height: normal; font-size: 14.4px; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; position: relative;">CH4/air flat-flame. Pyrolysis oil from a cyclone fast pyrolysis plant was combusted. The flame was characterized by using two-color pyrometry, Tunable Diode Laser Absorption Spectroscopy and high-magnification shadowgraphy. Overall, the assessed model correctly predicted flame structure and seemed appropriate for engineering applications, but lacked predictive power in estimating droplet size distributions. Numerical results were the most sensitive to variations in the initial droplet size distribution; however, seemed robust to changes in the multicomponent fuel formulation. Several conclusions were drawn regarding FPO spray combustion itself; e.g., the amount of produced soot in the flames was very low and droplets exhibited microexplosion behavior in a characteristic size-shape regime.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Biomass fast pyrolysis oil, Spray combustion, Computational Fluid Dynamics, Optical diagnostics
National Category
Applied Mechanics
Research subject
Experimental Mechanics
Identifiers
urn:nbn:se:ltu:diva-71258 (URN)10.1016/j.fuel.2018.10.031 (DOI)000448573200054 ()2-s2.0-85054708357 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-10-18 (svasva)

Available from: 2018-10-18 Created: 2018-10-18 Last updated: 2019-03-27Bibliographically approved
Wahl, J., Gren, P., Bergström, P., Lindbäck, T., Magnusson, M., Domeij, K. & Sjödahl, M. (2018). Comparison between process simulation and deformation measured by defocused speckle photography. In: M. Kujawińska ; L. R. Jaroszewicz (Ed.), Speckle 2018: VII International Conference On Speckle Metrology. Paper presented at SPECKLE 2018: VII International Conference on Speckle Metrology, 9-12 September 2018, Janów Podlaski, Poland.. SPIE - International Society for Optical Engineering, 10834, Article ID 108341K.
Open this publication in new window or tab >>Comparison between process simulation and deformation measured by defocused speckle photography
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2018 (English)In: Speckle 2018: VII International Conference On Speckle Metrology / [ed] M. Kujawińska ; L. R. Jaroszewicz, SPIE - International Society for Optical Engineering, 2018, Vol. 10834, article id 108341KConference paper, Published paper (Refereed)
Abstract [en]

Defocused laser speckle photography is used as a tool to measure the heat responses in a titanium component during laser heating. The evolution of the response is compared with a set of preprocessed Finite Element Simulations of the corresponding process with the aim to verify the simulation model and to find the simulation settings that best resemble the experimental results. The titanium component consists of a 300 x 100 mm2 substrate of thickness 3.2 mm on which a 200 x 30 x 11 mm3 ridge is built up using the laser metal deposition by wire process. The component is heated on the top of the ridge by a 300 W laser for 10 s and the deformation of the subtrate is followed throughout the heating-cooling cycle. The simulated deformation gradient is shown to resemble the measured response, and the magnitude of the response indicates that about 70 % of the laser power transferres into heat in the metal.

Place, publisher, year, edition, pages
SPIE - International Society for Optical Engineering, 2018
Series
Proceedings of SPIE - the International Society for Optical Engineering, ISSN 0277-786X ; 10834
Keywords
Laser speckle, deformation, in-process measurement
National Category
Applied Mechanics Other Mechanical Engineering
Research subject
Experimental Mechanics; Computer Aided Design
Identifiers
urn:nbn:se:ltu:diva-71895 (URN)10.1117/12.2319384 (DOI)000455052600052 ()2-s2.0-85058383509 (Scopus ID)9781510622975 (ISBN)
Conference
SPECKLE 2018: VII International Conference on Speckle Metrology, 9-12 September 2018, Janów Podlaski, Poland.
Funder
VINNOVA
Available from: 2018-12-05 Created: 2018-12-05 Last updated: 2019-01-28Bibliographically approved
Dagli, D., Zeinali, A., Gren, P. & Laue, J. (2018). Image analyses of frost heave mechanisms based on freezing tests with free access to water. Cold Regions Science and Technology, 146, 187-198
Open this publication in new window or tab >>Image analyses of frost heave mechanisms based on freezing tests with free access to water
2018 (English)In: Cold Regions Science and Technology, ISSN 0165-232X, E-ISSN 1872-7441, Vol. 146, p. 187-198Article in journal (Refereed) Published
Abstract [en]

A freezing test apparatus was supplemented with a camera to allow for recording and monitoring one-dimensional freezing tests to analyze the development of ice lenses via particle image velocimetry (PIV) in the laboratory. Two tests on disturbed, partially saturated samples of silt loam were conducted. Image recording and correlation analyses provided detailed information about frost front penetration and ice lens formation(s) under varying temperature boundary conditions. Thawing has also been regarded in further studies.

Results of the image analyses were compared to readings from conventional displacement measurements during the same test. Significant agreement between the results of image analyses and displacement measurements has been found. Test results were also used to establish a qualitative relationship between heat extraction and heave rates. Advantages and disadvantages of utilizing image analysis methods were discussed. Potential remedies for overcoming the drawbacks of using image analysis are suggested.

Image analysis is shown to be a viable method in further understanding of frost heave mechanisms.

Place, publisher, year, edition, pages
Elsevier, 2018
National Category
Geotechnical Engineering Applied Mechanics
Research subject
Soil Mechanics; Experimental Mechanics
Identifiers
urn:nbn:se:ltu:diva-66263 (URN)10.1016/j.coldregions.2017.10.019 (DOI)000423963300021 ()
Note

Validerad;2018;Nivå 2;2017-12-21 (andbra)

Available from: 2017-10-25 Created: 2017-10-25 Last updated: 2018-04-19Bibliographically approved
Amer, E., Gren, P., Ramser, K. & Sjödahl, M. (2018). Measurement of selective species concentration using spectroscopic holography. In: M. Kujawińska ; L. R. Jaroszewicz (Ed.), Speckle 2018: VII International Conference on Speckle Metrology. Paper presented at Speckle 2018: VII International Conference On Speckle Metrology 9-12 September 2018 Janów Podlaski, Poland. SPIE - International Society for Optical Engineering, 10834, Article ID 108340P.
Open this publication in new window or tab >>Measurement of selective species concentration using spectroscopic holography
2018 (English)In: Speckle 2018: VII International Conference on Speckle Metrology / [ed] M. Kujawińska ; L. R. Jaroszewicz, SPIE - International Society for Optical Engineering, 2018, Vol. 10834, article id 108340PConference paper, Published paper (Refereed)
Abstract [en]

Spectroscopic holography refers to techniques in which the detected hologram contains information about specific species in the medium under study. In general, at least two lasers are required with wavelengths chosen carefully to fit the interaction process utilized. In this process, energy from the shorter wavelength laser beam is transferred to the longer wavelength coherently through the process of stimulated emission. Two interaction mechanisms are considered; Stimulated Laser Induced Fluorescence (LIF) and Stimulated Raman Scattering (SRS), which both are species specific with the ability of coherent interaction. In this paper, the fundamental properties of spectroscopic holography is presented and demonstrated with a few idealized experiments. These validation experiments are performed in a gas chamber in which different gases may be blended and the gas pressure changed between 1-12 bars. In addition, two examples of applications are presented. In the first set of experiments, LIF holography is used to image light absorption and laser heating in a dye simultaneously. The second set of experiments is performed in a ow of methane gas. It is demonstrated that the combination of holographic phase measurements and SRS gain images may be used for calibration. This calibration may further be used to measure absolute concentration in a burning flame.

Place, publisher, year, edition, pages
SPIE - International Society for Optical Engineering, 2018
Series
Proceedings of SPIE - the International Society for Optical Engineering, ISSN 0277-786X ; 10834
National Category
Applied Mechanics
Research subject
Experimental Mechanics
Identifiers
urn:nbn:se:ltu:diva-72430 (URN)10.1117/12.2319386 (DOI)000455052600021 ()2-s2.0-85058412906 (Scopus ID)9781510622975 (ISBN)
Conference
Speckle 2018: VII International Conference On Speckle Metrology 9-12 September 2018 Janów Podlaski, Poland
Available from: 2019-01-03 Created: 2019-01-03 Last updated: 2019-01-28Bibliographically approved
Khayamyan, S., Lundström, S., Hellström, G., Gren, P. & Lycksam, H. (2017). Measurements of Transitional and Turbulent Flow in a Randomly Packed Bed of Spheres with Particle Image Velocimetry. Transport in Porous Media, 116(1), 413-431
Open this publication in new window or tab >>Measurements of Transitional and Turbulent Flow in a Randomly Packed Bed of Spheres with Particle Image Velocimetry
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2017 (English)In: Transport in Porous Media, ISSN 0169-3913, E-ISSN 1573-1634, Vol. 116, no 1, p. 413-431Article in journal (Refereed) Published
Abstract [en]

Particle image velocimetry (PIV) has been used to investigate transitional and turbulent flow in a randomly packed bed of mono-sized transparent spheres at particle Reynolds number, (Formula presented.). The refractive index of the liquid is matched with the spheres to provide optical access to the flow within the bed without distortions. Integrated pressure drop data yield that Darcy law is valid at (Formula presented.). The PIV measurements show that the velocity fluctuations increase and that the time-averaged velocity distribution start to change at lower (Formula presented.). The probability for relatively low and high velocities decreases with (Formula presented.) and recirculation zones that appear in inertia dominated flows are suppressed by the turbulent flow at higher (Formula presented.). Hence there is a maximum of recirculation at about (Formula presented.). Finally, statistical analysis of the spatial distribution of time-averaged velocities shows that the velocity distribution is clearly and weakly self-similar with respect to (Formula presented.) for turbulent and laminar flow, respectively

Place, publisher, year, edition, pages
Springer, 2017
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-60561 (URN)10.1007/s11242-016-0781-0 (DOI)000394167300019 ()2-s2.0-84994430906 (Scopus ID)
Note

Validerad; 2017; Nivå 2; 2017-02-01 (andbra)

 

Available from: 2016-11-20 Created: 2016-11-20 Last updated: 2018-09-27Bibliographically approved
Khayamyan, S., Lundström, S., Gren, P., Lycksam, H. & Hellström, G. (2017). Transitional and Turbulent Flow in a Bed of Spheres as Measured with Stereoscopic Particle Image Velocimetry. Transport in Porous Media, 117(1), 45-67
Open this publication in new window or tab >>Transitional and Turbulent Flow in a Bed of Spheres as Measured with Stereoscopic Particle Image Velocimetry
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2017 (English)In: Transport in Porous Media, ISSN 0169-3913, E-ISSN 1573-1634, Vol. 117, no 1, p. 45-67Article in journal (Refereed) Published
Abstract [en]

Stereoscopic particle image velocimetry has been used to investigate inertia dominated, transitional and turbulent flow in a randomly packed bed of monosized PMMA spheres. By using an index-matched fluid, the bed is optically transparent and measurements can be performed in an arbitrary position within the porous bed. The velocity field observations are carried out for particle Reynolds numbers, (Formula presented.), between 20 and 3220, and the sampling is done at a frequency of 75 Hz. Results show that, in porous media, the dynamics of the flow can vary significantly from pore to pore. At (Formula presented.) around 400 the spatially averaged time fluctuations of total velocity reach a maximum and the spatial variation of the time-averaged total velocity, (Formula presented.) increases up to about the same (Formula presented.) and then it decreases. Also in the studied planes, a considerable amount of the fluid moves in the perpendicular directions to the main flow direction and the time-averaged magnitude of the velocity in the main direction, (Formula presented.), has an averaged minimum of 40% of the magnitude of (Formula presented.) at (Formula presented.) about 400. For (Formula presented.), this ratio is nearly constant and (Formula presented.) is on average a little bit less than 50% of (Formula presented.). The importance of the results for longitudinal and transverse dispersion is discussed.

Place, publisher, year, edition, pages
Springer, 2017
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-61843 (URN)10.1007/s11242-017-0819-y (DOI)000395621700003 ()2-s2.0-85009872759 (Scopus ID)
Note

Validerad; 2017; Nivå 2; 2017-03-06 (andbra)

Available from: 2017-02-07 Created: 2017-02-07 Last updated: 2018-10-04Bibliographically approved
Tatar, K. & Gren, P. (2016). Estimation of the in-plane vibrations of a rotating spindle, using out-of-plane laser vibrometry measurements (ed.). Paper presented at . Mechanical systems and signal processing, 72-73, 660-666
Open this publication in new window or tab >>Estimation of the in-plane vibrations of a rotating spindle, using out-of-plane laser vibrometry measurements
2016 (English)In: Mechanical systems and signal processing, ISSN 0888-3270, E-ISSN 1096-1216, Vol. 72-73, p. 660-666Article in journal (Refereed) Published
Abstract [en]

A method for estimating the in-plane vibrations of a rotating spindle using out-of-plane laser vibrometry measurements is described. This method enables the possibility to obtain the two orthogonal radial vibration components of a rotating spindle. The method uses the fact that the laser vibrometer signal is a total surface velocity of the measurement point in the laser direction.Measurements are conducted on a rotating milling machine spindle. The spindle is excited in a controlled manner by an active magnetic bearing and the response is measured by laser vibrometer in one of the two orthogonal directions and inductive displacement sensors in two orthogonal directions simultaneously. The work shows how the laser vibrometry crosstalk can be used for resolving the in-plane vibration component, that is the vibrations in the laser vibrometer cross direction. The result is compared to independent measurement signals from the displacement sensors.The measurement method can be used for vibration measurements on rotating parts, for example, where there is lack of space for orthogonal measurements.

National Category
Applied Mechanics
Research subject
Experimental Mechanics
Identifiers
urn:nbn:se:ltu:diva-13485 (URN)10.1016/j.ymssp.2015.11.023 (DOI)000369196200040 ()2-s2.0-84955689577 (Scopus ID)cb4fee6a-0714-443a-b523-7948cf765153 (Local ID)cb4fee6a-0714-443a-b523-7948cf765153 (Archive number)cb4fee6a-0714-443a-b523-7948cf765153 (OAI)
Note
Validerad; 2016; Nivå 2; 20151202 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Khayamyan, S., Lundström, S., Lycksam, H., Gren, P. & Hellström, G. (2016). PIV measurements within a randomly packed bed of spheres (ed.). Paper presented at Interpore 2016 : 8th International Conference on Porous Media & Annual Meeting 09/05/2016 - 12/05/2016. Paper presented at Interpore 2016 : 8th International Conference on Porous Media & Annual Meeting 09/05/2016 - 12/05/2016.
Open this publication in new window or tab >>PIV measurements within a randomly packed bed of spheres
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2016 (English)Conference paper, Oral presentation only (Refereed)
National Category
Fluid Mechanics and Acoustics Applied Mechanics
Research subject
Fluid Mechanics; Experimental Mechanics
Identifiers
urn:nbn:se:ltu:diva-27624 (URN)11f2898d-c1e8-4ad1-9fb2-2c2b0a30f10d (Local ID)11f2898d-c1e8-4ad1-9fb2-2c2b0a30f10d (Archive number)11f2898d-c1e8-4ad1-9fb2-2c2b0a30f10d (OAI)
Conference
Interpore 2016 : 8th International Conference on Porous Media & Annual Meeting 09/05/2016 - 12/05/2016
Note
Godkänd; 2016; 20160511 (stlu)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2017-11-25Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-8355-2414

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