The space-time cross-correlation function $C_T\left(r,\tau \right)$ of local temperature fluctuations in turbulent Rayleigh-Bénard convection is obtained from simultaneous two-point time series measurements. The obtained $C_T\left(r,\tau \right)$ is found to have the scaling form $C_T\left(r_E,0\right)$ with $r_E={\left[{\left(r-U\tau \right)}^2+V^2{\tau }^2\right]}^{1/2}$, where $U$ and $V$ are two characteristic velocities associated with the mean and rms velocities of the flow. The experiment verifies the theory and demonstrates its applications to a class of turbulent flows in which the requirement of Taylor’s frozen flow hypothesis is not met.

• Received 11 February 2010

DOI:https://doi.org/10.1103/PhysRevE.81.065303