The spatial resolution of hot-wire arrays for the measurement of small-scale turbulence

The measurement of small-scale turbulence quantities with hot-wire arrays has proven difficult due to the difficulty of measuring spatial derivatives of velocity and temperature fluctuations reliably. This paper reviews recent developments in accounting for spatial resolution effects on these arrays. In particular, the effects of wire length, separations between wires and effective wire inclinations are considered for an X-probe, parallel-wire arrays and vorticity arrays. Expressions for correcting spectra and variances of velocity (or temperature) derivatives and vorticity components are presented. Sufficient evidence is now available to validate these corrections, at least when local isotropy is a reasonable approximation. Data from direct numerical simulations (DNS) have played an important role in the context of this validation.