Visualization of turbulence structure in unsteady non-penetrative thermal convection using liquid crystal thermometry and stereo velocimetry

Fujisawa, Nobuyuki; Watanabe, Masataka; Hashizume, Yuji

doi:10.1007/bf03181932

Cited by 7 publications

(5 citation statements)

References 21 publications

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“…Careful calibration is therefore essential to achieve measurements with a small uncertainty. Many reviews and papers have been published around the topic of LC thermography [7,[40][41][42][43][44][45][46][47][48][49][50][51][52][53][54]. Fujisawa N. and his group have produced many papers concerning this field [42][43][44][45]54].…”

Section: Liquid Crystal (Lc)mentioning

confidence: 99%

“…Many reviews and papers have been published around the topic of LC thermography [7,[40][41][42][43][44][45][46][47][48][49][50][51][52][53][54]. Fujisawa N. and his group have produced many papers concerning this field [42][43][44][45]54]. To study the transfer of heat and momentum in thermal fluid flow, the simultaneous measurement of temperature and velocity plays an important role in determining the physical properties of the transport phenomenon.…”

Section: Liquid Crystal (Lc)mentioning

confidence: 99%

“…From the 1990s to the early 2000s, there was significant progress in quantitative simultaneous measurements using LC, subsequently to the rapid progress of the PIV. Dabiri and Gharib [7,[65][66][67] and Fujisawa, N. and his group [42][43][44][45]54] performed many studies on the temperature calibration of LC and the extension of the application to three-dimensional simultaneous measurement. Segura et al [68] successfully used an emulsion of non-encapsulated LC micro droplets in order to measure temperature and velocity three-dimensionally, capturing circularly polarized emissions from the droplets produced to block background noise.…”

Section: Mtt With Mt)mentioning

confidence: 99%

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Particle-based temperature measurement coupled with velocity measurement

Someya

2020

Meas. Sci. Technol.

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This review article focuses on the simultaneous particle-based measurement of velocity and temperature. The thermographic PIV with phosphor particles is included in the scope. However, there are many other dye-doped particles that can be used in these methods, some of which are more suitable for measurements of liquid flow and low temperature flow.This review summarized the methods for fabrication, applications, optical properties, and limitations of temperature sensitive particles, and the extensive coverage of the field provided by this review renders it useful as a base for further experimentation. Dopant sensor molecules are also summarized in this review make it possible to fabricate functional particles that are suitable for the aims of an individual researcher. These particles are excited by a UV-laser and several kinds of them can be excited using a common green laser.Several approaches to velocity and temperature measurements, mono-color intensity-based method, the ratiometric method and the lifetime method are explained. The combined methods are limited by velocity conditions; therefore, decoupling the temperature measurement from the velocity measurement is sometimes reasonable. However, combined measurements were also considered in this review.There are many possible sources of error when using these methods; however, the most important factor is the following capacity of the particles, especially in gaseous flow. The deformation of particle images because of the long exposure inherent in the lifetime-based method was discussed quantitatively.Applications of liquid/gas/multiphase flow measurements were introduced. Micro capsules or microbeads are often used for a liquid flow and a microchannel flow. Many previous works use a phosphor for a high temperature gas flow. Uncertainties are different on a case-by-case basis. Accurate calibration is very important in suppressing errors. The development of easy calibration methods or calibration free methods while retaining high accuracy is an important issue in future work.

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Section: Liquid Crystal (Lc)mentioning

confidence: 99%

Section: Liquid Crystal (Lc)mentioning

confidence: 99%

Section: Mtt With Mt)mentioning

confidence: 99%

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Particle-based temperature measurement coupled with velocity measurement

Someya

2020

Meas. Sci. Technol.

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“…However, even more relevant for the present work is the combination of PIT and PIV used in [20][21][22] to measure the temperature and two components of the velocity fields in planes of a natural convection sample. The extension to the measurement of all three components of the velocity field simultaneous to the temperature field in planes was realized in an experiment with water by combining PIT with stereo PIV [23]. Fujisawa et al investigated the convection patterns by means of POD analysis and identified a large-scale motion.…”

Section: Introductionmentioning

confidence: 99%

Simultaneous tomographic particle image velocimetry and thermometry of turbulent Rayleigh–Bénard convection

Schiepel¹,

Schmeling²,

Wagner³

2021

Meas. Sci. Technol.

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This paper presents a non-intrusive measurement technique for the simultaneous assessment of the three-dimensional (3D) velocity and temperature fields in thermal convection. The technique is based on the combination of tomographic particle image velocimetry and particle image thermometry. Thermochromic liquid crystal particles serve simultaneously as both flow tracers and thermometers. The velocity fields were measured in a volume of 62 500 cm 3 and the temperature fields in a subvolume of 20 000 cm 3 . Turbulent Rayleigh-Bénard convection in a water-glycol mixture at Ra = 7.0 × 10 9 and Pr = 18 was used as a model system to measure the instantaneous 3D velocity and temperature fields at the same time. Uncertainties of σ v ⩽ 0.66 mm s −1 for the velocity and σ t ⩽ 0.095 K for the temperature measurement were estimated corresponding to dynamic ranges of 24 and 21 levels, respectively. Correlating the measured temperature and velocity fields, it is shown that the obtained large-scale structure reflects a region of warm rising fluid which is well-known from the literature.

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“…Although 3-D velocity, concentration and temperature fields can be measured in a laboratory (Reungoat፧ et al, 2007;Fujisawa et al, 2008), the whole flow field measurement is very difficult in a real space such as a hospital room, which is always occupied by patients, or a domed baseball stadium, which has a large volume. Airflow distributions are usually measured with some sensors whose measured points are limited in the 3-D space.…”

Section: Introductionmentioning

confidence: 99%

Neural-net based modeling of velocity and concentration fields

Kimura

Yoke

Kaga

et al. 2009

J Vis

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This paper proposes a novel algorithm using an artificial neural network for modeling simultaneously both a 3-D flow velocity vector and a concentration field. The neural network is trained so that four outputted values of the network, three components of a 3-D velocity vector and a concentration of substances such as air pollutants or bacilli, agree with measured ones and additionally the continuity and diffusion equations are satisfied in the flow field. An approximate model for the velocity and concentration field can be constructed in the neural network from sparsely measured data. When any 3-D position, (x, y, z), is inputted to the neural network model, it outputs a 3-D velocity vector and a concentration at the position. The entire 3-D velocity vector and concentration field, therefore, can be easily estimated using the model. To validate the algorithm, the smoke concentration distribution estimated from a very limited set of measured data is compared with the measured one in which most of the data is unused for the modeling. Even from sparsely measured velocity vectors and smoke concentrations, the novel algorithm gives the entire concentration distribution whose flow characteristics are almost similar to the experimental result.

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Visualization of turbulence structure in unsteady non-penetrative thermal convection using liquid crystal thermometry and stereo velocimetry

Cited by 7 publications

References 21 publications

Particle-based temperature measurement coupled with velocity measurement

Particle-based temperature measurement coupled with velocity measurement

Simultaneous tomographic particle image velocimetry and thermometry of turbulent Rayleigh–Bénard convection

Neural-net based modeling of velocity and concentration fields

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