Two-point turbulence measurements downstream of a heated grid

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Abstract
Two‐point turbulence data from hot and cold wire anemometry are presented which describe the temperature and velocity fields downstream of a heated grid in a low speed wind tunnel. The velocity and temperature statistics are found to differ in that (a) the velocity energy spectrum has no inertial subrange while the temperature spectrum displays a significant region of −5/3 slope and (b) for lateral probe displacements the temperature coherence is larger than that of velocity. This result is surprising since both fields were generated by the same grid, and since the temperature field appears to have been passive. Phase measurements indicate that at least the lower turbulence wavenumbers move with equal convection velocities, thereby supporting Taylor’s hypothesis of quasi‐frozen pattern, but this convection velocity appears to be slightly greater than the mean fluid velocity. Cross correlations from the signals of two spatially separated probes are presented for both the velocity and temperature fields. In general, they agree with expectations derived from the theory of isotropic turbulence.