Development of the thermographic laser doppler velocimetry technique

Anthony O. Ojo, Benoit Fond, Christopher Abram, Berend G. M. van Wachem, Andrew L. Heyes, Frank Beyrau

Research output: Chapter in Book/Report/Conference proceedingConference contribution book

Abstract

Simultaneous measurements of flow temperature and velocity are crucial in characterising turbulent heat transport processes. The advancement of particle-based velocimetry methods has provided both qualitative and quantitative description of turbulent flows. In recent studies, the use of thermographic phosphors particles as flow tracers further supports these advancements due to the additional temperature information they provide. These particles have been employed to obtain planar measurements of flow temperature and velocity in an approach termed thermographic particle image velocimetry. Similarly, a point-based measurement approach has been demonstrated to achieve simultaneous measurements of these flow vector-scalar properties. This paper further describes and characterises the point-based joint measurement technique called thermographic laser Doppler velocimetry (thermographic LDV) technique for flow temperature and velocity measurements. The flow metrology uses both Mie-scattered light and the optical properties of the phosphorescence emission that results from successive interactions between continuous wave laser light and individual 2 µm BaMgAl10O17:Eu2+ thermographic phosphor particles, which are seeded into the flow as a tracer. Photomultipier tubes (PMTs) are used to detect the signals collected from the measurement volume. The flow velocity is determined from frequency of the Doppler bursts obtained when particles traverses the fringes of two crossed visible laser beams as in conventional LDV. Luminescence in the form of Gaussian bursts that occurs after excitation of the same particles by an overlapped UV laser beam is simultaneously detected. Flow temperatures are evaluated from these acquired luminescence signals using the two-colour ratio, where two PMTs, each fitted with interference filters, transmits different parts of the temperature dependent emission spectral profile. The ratio of the two detected intensities has a monotonic dependence on temperature and is used to infer the particle temperature using previously acquired calibration data. Potential cross dependencies that affect temperature measurements such as seeding density and laser fluence are investigated. The technique is then applied to acquire combined vector-scalar profile measurement at the exit of turbulent heated jet to evaluate the accuracy of the temperature measurements. A deviation better than 2% is achieved between mean temperature profile measurements obtained using a thermocouple and the point-based technique. Thermographic LDV is shown to serve as a valuable tool to turbulent heat transfer research.
LanguageEnglish
Title of host publicationProceedings of the 18th International Symposium On Application of Laser And Imaging Techniques To Fluid Mechanics
Subtitle of host publicationLisbon, Portugal, July 4 - 7, 2016
Place of PublicationLisbon, Portugal
Number of pages16
ISBN (Electronic)9789899877788
Publication statusPublished - 4 Jul 2016

Fingerprint

Velocity measurement
Lasers
Temperature measurement
Temperature
Phosphors
Laser beams
Luminescence
Volume measurement
Phosphorescence
Continuous wave lasers
Flow measurement
Thermocouples
Flow velocity
Turbulent flow
Optical properties
Calibration
Heat transfer
Color

Keywords

  • thermographic phosphors
  • flow thermometry
  • velocimetry
  • point-wise measurements

Cite this

Ojo, A. O., Fond, B., Abram, C., van Wachem, B. G. M., Heyes, A. L., & Beyrau, F. (2016). Development of the thermographic laser doppler velocimetry technique. In Proceedings of the 18th International Symposium On Application of Laser And Imaging Techniques To Fluid Mechanics : Lisbon, Portugal, July 4 - 7, 2016 Lisbon, Portugal.
Ojo, Anthony O. ; Fond, Benoit ; Abram, Christopher ; van Wachem, Berend G. M. ; Heyes, Andrew L. ; Beyrau, Frank. / Development of the thermographic laser doppler velocimetry technique. Proceedings of the 18th International Symposium On Application of Laser And Imaging Techniques To Fluid Mechanics : Lisbon, Portugal, July 4 - 7, 2016. Lisbon, Portugal, 2016.
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Ojo, AO, Fond, B, Abram, C, van Wachem, BGM, Heyes, AL & Beyrau, F 2016, Development of the thermographic laser doppler velocimetry technique. in Proceedings of the 18th International Symposium On Application of Laser And Imaging Techniques To Fluid Mechanics : Lisbon, Portugal, July 4 - 7, 2016. Lisbon, Portugal.

Development of the thermographic laser doppler velocimetry technique. / Ojo, Anthony O.; Fond, Benoit ; Abram, Christopher ; van Wachem, Berend G. M.; Heyes, Andrew L.; Beyrau, Frank.

Proceedings of the 18th International Symposium On Application of Laser And Imaging Techniques To Fluid Mechanics : Lisbon, Portugal, July 4 - 7, 2016. Lisbon, Portugal, 2016.

Research output: Chapter in Book/Report/Conference proceedingConference contribution book

TY - GEN

T1 - Development of the thermographic laser doppler velocimetry technique

AU - Ojo, Anthony O.

AU - Fond, Benoit

AU - Abram, Christopher

AU - van Wachem, Berend G. M.

AU - Heyes, Andrew L.

AU - Beyrau, Frank

PY - 2016/7/4

Y1 - 2016/7/4

N2 - Simultaneous measurements of flow temperature and velocity are crucial in characterising turbulent heat transport processes. The advancement of particle-based velocimetry methods has provided both qualitative and quantitative description of turbulent flows. In recent studies, the use of thermographic phosphors particles as flow tracers further supports these advancements due to the additional temperature information they provide. These particles have been employed to obtain planar measurements of flow temperature and velocity in an approach termed thermographic particle image velocimetry. Similarly, a point-based measurement approach has been demonstrated to achieve simultaneous measurements of these flow vector-scalar properties. This paper further describes and characterises the point-based joint measurement technique called thermographic laser Doppler velocimetry (thermographic LDV) technique for flow temperature and velocity measurements. The flow metrology uses both Mie-scattered light and the optical properties of the phosphorescence emission that results from successive interactions between continuous wave laser light and individual 2 µm BaMgAl10O17:Eu2+ thermographic phosphor particles, which are seeded into the flow as a tracer. Photomultipier tubes (PMTs) are used to detect the signals collected from the measurement volume. The flow velocity is determined from frequency of the Doppler bursts obtained when particles traverses the fringes of two crossed visible laser beams as in conventional LDV. Luminescence in the form of Gaussian bursts that occurs after excitation of the same particles by an overlapped UV laser beam is simultaneously detected. Flow temperatures are evaluated from these acquired luminescence signals using the two-colour ratio, where two PMTs, each fitted with interference filters, transmits different parts of the temperature dependent emission spectral profile. The ratio of the two detected intensities has a monotonic dependence on temperature and is used to infer the particle temperature using previously acquired calibration data. Potential cross dependencies that affect temperature measurements such as seeding density and laser fluence are investigated. The technique is then applied to acquire combined vector-scalar profile measurement at the exit of turbulent heated jet to evaluate the accuracy of the temperature measurements. A deviation better than 2% is achieved between mean temperature profile measurements obtained using a thermocouple and the point-based technique. Thermographic LDV is shown to serve as a valuable tool to turbulent heat transfer research.

AB - Simultaneous measurements of flow temperature and velocity are crucial in characterising turbulent heat transport processes. The advancement of particle-based velocimetry methods has provided both qualitative and quantitative description of turbulent flows. In recent studies, the use of thermographic phosphors particles as flow tracers further supports these advancements due to the additional temperature information they provide. These particles have been employed to obtain planar measurements of flow temperature and velocity in an approach termed thermographic particle image velocimetry. Similarly, a point-based measurement approach has been demonstrated to achieve simultaneous measurements of these flow vector-scalar properties. This paper further describes and characterises the point-based joint measurement technique called thermographic laser Doppler velocimetry (thermographic LDV) technique for flow temperature and velocity measurements. The flow metrology uses both Mie-scattered light and the optical properties of the phosphorescence emission that results from successive interactions between continuous wave laser light and individual 2 µm BaMgAl10O17:Eu2+ thermographic phosphor particles, which are seeded into the flow as a tracer. Photomultipier tubes (PMTs) are used to detect the signals collected from the measurement volume. The flow velocity is determined from frequency of the Doppler bursts obtained when particles traverses the fringes of two crossed visible laser beams as in conventional LDV. Luminescence in the form of Gaussian bursts that occurs after excitation of the same particles by an overlapped UV laser beam is simultaneously detected. Flow temperatures are evaluated from these acquired luminescence signals using the two-colour ratio, where two PMTs, each fitted with interference filters, transmits different parts of the temperature dependent emission spectral profile. The ratio of the two detected intensities has a monotonic dependence on temperature and is used to infer the particle temperature using previously acquired calibration data. Potential cross dependencies that affect temperature measurements such as seeding density and laser fluence are investigated. The technique is then applied to acquire combined vector-scalar profile measurement at the exit of turbulent heated jet to evaluate the accuracy of the temperature measurements. A deviation better than 2% is achieved between mean temperature profile measurements obtained using a thermocouple and the point-based technique. Thermographic LDV is shown to serve as a valuable tool to turbulent heat transfer research.

KW - thermographic phosphors

KW - flow thermometry

KW - velocimetry

KW - point-wise measurements

UR - http://ltces.dem.ist.utl.pt/lxlaser/lxlaser2016/

M3 - Conference contribution book

BT - Proceedings of the 18th International Symposium On Application of Laser And Imaging Techniques To Fluid Mechanics

CY - Lisbon, Portugal

ER -

Ojo AO, Fond B, Abram C, van Wachem BGM, Heyes AL, Beyrau F. Development of the thermographic laser doppler velocimetry technique. In Proceedings of the 18th International Symposium On Application of Laser And Imaging Techniques To Fluid Mechanics : Lisbon, Portugal, July 4 - 7, 2016. Lisbon, Portugal. 2016