Near-infrared measurement of non-axisymmetric temperature and flow fields formed by free convection around a small heating sphere in water

Abstract

This paper presents a method for measuring simultaneously non-axisymmetric three-dimensional (3D) temperature and flow fields in water formed by free convection surrounding a 1-mm-diameter heated sphere. This method is based on the temperature dependence of the absorption coefficient of water at a wavelength of 1150 nm. In the experiment, two-dimensional (2D) images of absorbance in two orthogonal directions were acquired. To reconstruct the 3D temperature distribution, we applied a non-axisymmetric Abel inverse transform to the 2D images. In addition, the flow velocity distribution was obtained by using a particle tracking method with the Lucas-Kanade algorithms. The results demonstrated that the evolution of the non-axisymmetric temperature distributions involved with free convection, and the flow velocities and directions reflected circulating flow with an upward plume.