Higher-order passive scalar (temperature) structure functions are measured in the turbulent wake of a circular cylinder at a Taylor-microscale Reynolds number ($R_{\lambda }$) of 370. The scalar is injected by two different means: (i) heating of the cylinder and (ii) use of a mandoline. Even though the second-order statistics (e.g., power spectra, second-order structure functions) of the scalar field are experimentally indistinguishable in the inertial and dissipative ranges, we observe notable differences in the inertial-range scaling exponents (${\xi }_n$) of the scalar structure functions at higher orders. The implication is therefore that the variations in previous estimates of ${\xi }_n$ may be attributable to differences in the scalar field initial conditions (and may not be deemed characteristic of a universal nature of the small-scale statistics of turbulent passive scalars).

• Received 28 January 2009

DOI:https://doi.org/10.1103/PhysRevLett.103.034501