Small-scale turbulent fluctuations beyond Taylor's frozen-flow hypothesis

Abstract

The space-time cross-correlation function CT (r,τ) of local temperature fluctuations in turbulent Rayleigh-Bénard convection is obtained from simultaneous two-point time series measurements. The obtained CT (r,τ) is found to have the scaling form CT (rE, 0) with rE = [ ( r-Uτ ) 2 + V2 τ2 ] 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. © 2010 The American Physical Society.