Study of strong temperature mixing in subsonic grid turbulence

This is the authors' abstract. We don't add key points for this paper.

Strong temperature mixing in subsonic air turbulence is studied in an open-circuit wind tunnel with a 0.5 m cross section. The specially constructed heating grid consumes up to 300 kW of electric power at a mean flow velocity of 11 m/sec. The highest mean absolute temperature 〈T〉 reaches 370°K, while the rms temperature fluctuation θ′ at midtunnel is typically 6°K. Basic statistics of the temperature field are measured and discussed. It is found, in particular, that (i) the streamwise decay of the normalized mean-square temperature fluctuation (θ′ / < T >)2 is not sensitive to the applied heating rates, suggesting that so far buoyancy contributes little to the dynamics of the turbulence; (ii) the observed decay rates are much higher than those reported by others in the literature and are consistent with the higher drag characteristics of the present grid; (iii) the temperature fluctuation spectrum, when normalized by local fluid properties and dissipation rates, retains a universal form and show an inertial-convection subrange of limited extent; (iv) the one-dimensional universal scalar inertial Kolmogoroff constant, β1, determined from such subrange has a value of 0.60±0.06.