Linearly salt stratified fluids of different Prandtl number were subjected to turbulent stirring by a horizontally oscillating vertical grid in a closed laboratory system. The experimental setup allowed the independent measurement of an rms turbulent lengthscale L_t, turbulent diffusivity for mass K_ρ, rate of dissipation of turbulent kinetic energy ε, stratification strength N and viscosity ν, for a wide range of turbulence intensities, ε/νN~2. The behaviour of both L_t and K_ρ was characterised in terms of this turbulence intensity and two regimes were identified. In the more energetic of these regimes (Regime E, where 300 < ε/νN~2 < 10~5), quantitative expressions for both L_t and K_ρ were identified. In this regime, L_t was found to be a function of only ν, κ and N, whilst K_ρ was a function of ν, κ and (ε/νN~2)~(1/3). Prom these expressions for L_t and K_ρ, a scaling relation for the root mean square turbulent velocity, U_t, was derived. This scaling relation showed good agreement with other data sets. In the weaker turbulence regime (Regime W, where 10 < ε/νN~2 < 300) a quantitative relationship was found for K_ρ as a function of ν, κ and ε/νN~2. Comparison was made between our expressions for K_ρ and the model of Osborn (1980). For 10 < ε/νN~2 < 1000, the model of Osborn (1980) differs from our experimental results by approximately a factor of 2. For higher turbulence intensities the model and experimental results diverge, such that at ε/νN~2 ≈ 10~4, there is approximately an order of magnitude discrepancy between the model and our measurements.
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