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

Approximations to energy and temperature dissipation rates, denoted as εap and χap, 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 x2/L ⩽ 1, local isotropy is approximately satisfied. When x2/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 εap is strongly correlated with ω32, the correlation between ω32 and χap is small.