Experimental Study of Turbulent Heat Transfer in a Two-Dimensional Curved Channel. Time-Mean Temperature and Multiple Temperature/Velocity Correlations in the Entrance Section.

Full measurements of the temperature field have been made in a turbulent flow of air through the entrance section of a two-dimensional curved channel. According to the experimental results, the wall heat flux develops more rapidly than the time-mean temperature distribution, decreasing and increasing on the inner and outer walls, respectively. Since radial locations at which the time-mean temperature gradient and the radial turbulent heat flux become zero do not coincide, the eddy diffusivity of heat becomes negative in a wide region extending about 20% of the channel width. In the vicinity of the wall, the temperature fluctuation intensity normalized by the friction temperature is not affected by the wall curvature, whereas the cross-correlation coefficients, the skewness and the flatness of velocity and temperature fluctuations are appreciably affected. The triple correlations relating to the transverse diffusion decrease and increase markedly on the inner- and outer-wall sides, respectively.