Decay of Temperature Variance in the Presence of Nonhomogeneous Strain

Abstract

The effect of nonhomogeneous strain caused by two-dimensional objects on single point statistical properties of the turbulent velocity and turbulent scalar (temperature) and their cross moments are investigated experimentally. The heated turbulent flow is produced by means of a biplane array of round rods and a biplane array of heated, thin wires placed downstream of the turbulence producing grid. The experiments are performed for three different ratios of the integral scale, L0 , to the object dimension, D, of 0.38, 1.90 and 3.1. Measurements of time resolved temperature and longitudinal and transverse velocity components are obtained using a triple wire probe consisting of a cold wire and two hot wires. Results indicate that, for L0 =1.9 and 3.1, the decay rate of temperature variance is nearly the same in the region of maximum shear stress (mss) and near the centerline. However, the decay rate in these regions is less than the decay rate of the temperature variance outside the cylinder wake. For L0 /D = 0.38, the decay rates of temperature variance are the same in the regions of mss, near the centerline and outside the wake. Transverse growth of the wake is found to be either increased or nearly unchanged depending on, respectively, whether the free stream integral scale is larger or less than that of the wake.