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

Abstract

In this paper, non-intrusive imaging techniques for simultaneously measuring temperature and velocity fields of thermal liquid flows are described. The experimental methods for temperature imaging considered here are the thermo-sensitive liquid crystal tracers and the laser-induced fluorescence, which are combined with particle image velocimetry (PIV) to measure simultaneously the corresponding 2D and 3D velocity fields. The features of these experimental methods and characteristics are examined, covering the measurable temperature range, uncertainty of measurement, time response and so on. The successful examples of simultaneous measurement of temperature and velocity fields are described for turbulent Rayleigh-Bérnard convection of a horizontal fluid layer and turbulent buoyant plume issuing from a circular nozzle, and their physical mechanisms of transport phenomena are explained.

Temperature measurement of dilute hydrogen flame by digital laser-speckle technique

“…Such flame visualization technique is very effective to observe the reaction zone of the dilute hydrogen flame, which is invisible without visualization technique (Fujisawa et al , 2008. The visualized flame was taken by a color CCD camera having a spatial resolution 769x492pixels with 8 bits for each RGB.…”

Occurrence of asymmetric flow pattern behind a double

“…The vertical cross-section of the flow field was visualized at the center of the double orifice using the laser sheet illumination of 1mm thickness. The PIV analysis was carried out using a direct cross-correlation algorithm with sub-pixel analysis, where the interrogation window size was set to 31x31 pixels (Kiuchi et al 2005;Fujisawa et al, 2008). Measurements are carried out for 1,000 instantaneous velocity fields taken at every 1 sec.…”

A new method of temperature measurement using thermochromic liquid crystals (extension of measurable range based on spectral intensity in the narrow-band wavelength)

“…Thermochromic liquid crystals (TLCs) are increasingly being used as an accurate and convenient means of measuring surface temperature and heat-transfer coefficient because their optical properties are dependent on temperature in a predictable and repeatable manner [1][2][3][4][5][6]. TLCs, whose molecular structure changes with temperature, selectively reflect light at a wavelength characteristic of the local surface temperature.…”