Approximations to energy and temperature dissipation rates in the far field of a cylinder wake

Abstract

Approximations to energy and temperature dissipation rates, denoted as ε ap and χ ap, are obtained using a probe consisting of four hot wires and a pair of parallel cold wires. The performance of the probe in measuring velocity and temperature derivatives and vorticity has been checked satisfactorily by comparing with isotropic calculations. Local isotropy across the wake is examined. The results show that in the region of x 2/ L ⩽ 1, local isotropy is approximately satisfied. When x 2/ L further increases, the departure from local isotropy becomes apparent. The differences between the present approximations of the two dissipation rates and those obtained by using isotropic relations are discussed in terms of their corresponding spectra and the correlation coefficient with respect to different longitudinal separations r. The correlations between the two dissipation fields and the enstrophy are also examined. Whereas ε ap is strongly correlated with ω 3 2 , the correlation between ω 3 2 and χ ap is small.