Simultaneous measurement of temperature and three velocity components in planar cross section by liquid-crystal thermometry combined with stereoscopic particle image velocimetry

Abstract

In this paper we describe a method for simultaneously measuring the temperature and the three velocity components in a planar cross section. The measurement of temperature field is carried out by analysing the colour image visualized by liquid-crystal particles, which changes colour with the variation of local temperature of the fluid. In contrast, the three velocity components of the flow field are simultaneously evaluated by the small tracer particles added to the fluid using stereoscopic particle image velocimetry. The uncertainty analysis has indicated that the accuracy of velocity measurement is improved by increasing the number of tracer particles. However, it deteriorated the accuracy of the temperature measurement, which suggests the presence of an optimum amount of tracer particles for the simultaneous measurement. This new method has been successfully applied to a turbulent Rayleigh-Bénard convection of a horizontal fluid layer between heated and cooled walls and the variation of the temperature and the velocity field created by the interaction of the hot and cold plumes was quantitatively visualized.

Simultaneous imaging techniques for temperature and velocity fields in thermal fluid flows

“…The three-components of velocity field in a planar section are measured by the stereo PIV analysis using the three-dimensional calibration algorithm. For details see Funatani and Fujisawa (2002).…”

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

“…Once the color images are taken from three 3CCD cameras, images are transformed into HSI color format (Funatani and Fujisawa, 2002). In the temperature analysis, the color to temperature transformation is conducted using the calibrated relationship between the color and the temperature, which is obtained from a uniform temperature field in the test section.…”

“…Then, the temperature is evaluated by solving the approximated relations of H, S, I with temperatures using a least square method. Note that the non-uniformity of the illumination and the viewing-angle effect of liquid crystals are considered in the measurement using the multi-point calibration technique (Funatani and Fujisawa, 2002). The uncertainty of measurement is 0.08 K at 95 % interval.…”

“…In recent years, the thermal turbulence has been studied using visualization techniques (Dabiri and Gharib, 1996;Funatani and Fujisawa, 2002;Banerjee et al, 2006;Inagaki et al, 2006). The three-dimensional temperature and velocity field in Rayleigh-Bernard convection is measured using scanning liquid-crystal thermometry and a stereo velocimetry (Fujisawa et al, 2005).…”

Non-encapsulated thermo-liquid crystals for digital particle tracking thermography/velocimetry in microfluidics

“…Up to this day, all of the reports on this flow diagnostics technique are based on acquiring color images of flows, with high concentrations of TLC material, and reconstructing planar temperature fields. Extensions of this principle like scanning methods (Fujisawa and Funatani 2000;Fujisawa et al 2005;Lutjen et al 2001) and stereoscopic arrangements (Funatani and Fujisawa 2002;Fujisawa et al 2004Fujisawa et al , 2005 have also been used to reconstruct three-dimensional temperature flow fields. All of these measurements rely on the concept of breaking the color images into sections and evaluating the mean temperature of the flow in each section.…”