Experiments with super-miniature hot-film probe for sub-Kolmogorov resolution in high-Reynolds-number turbulence

This is a report on implementation of the next stage of a project motivated by the discovery of far more important role played by the sub-Kolmogorov scales than commonly believed in high Reynolds number turbulence such as manifestations of nonlocal nature of turbulence involving direct and bidirectional coupling of conventionally-defined inertial and dissipative ranges showing (a) that both concepts are ill-posed and (b) that further progress requires sub-Kolmogorov resolution. The main results and issues that prompted the present work are in [1]-[2] and references therein. The final goal is manufacturing a multi-sensor probe of much smaller scale than available today with access to quantities like vorticity and strain at sub-Kolmogorov scales in high-Reynolds-number flows such as performed by Gulitski et al. [3] in the atmospheric surface layer at Re_λ~10⁴. This requires manufacturing a single-sensor probe of length of the order ~50 μ or even smaller to be used as a building block for the above multi-sensor one. The main theme of the present report is performing a number of experiments with single-sensor micro-probes of different lengths in a laboratory jet flow and comparison of experimental results obtained with such probes and the conventional hot-wire probe.