Micro-machined super-miniature hot-film multi-array probe for field experiments with sub-Kolmogorov resolution

Abstract

This is a report on the first successful experiments with a unique micro-hot-film multi-array probe. The main aim of this part of the project was to design, fabricate, implement and test in laboratory conditions a micro-hot-film multi-array probe for measurements in turbulent flows in field experiments with sub-Kolmogorov resolution. The key feature is that the probe is enabling to access, along with all three components of turbulent velocity fluctuations, also all nine components of the spatial velocity gradients tensor, including the option of obtaining the stream-wise velocity derivatives without employing the Taylor hypothesis, as well as velocity temporal derivatives. Hence the multi-array probe (typically five arrays) is built with each array consisting of four hot-film sensors, similarly to that of larger multi-array probe, based on arrays with four hot wires used in the atmospheric surface layer at Taylor micro-scale Reynolds number up to Re_λ ≈ 10⁴. This part of work relates to Reynolds numbers Re_λ < 500 and employs several laboratory flows including flow in a channel of rectangular cross section, in its bulk and in the boundary layers in the proximity of its smooth and rough walls, and in the confined jet of circular cross section.

Keywords:

• turbulent flows
• velocity gradients tensor
• sub-Kolmogorov resolution

Acknowledgements

The authors are grateful to the Meadow aerodynamic laboratory, Tel-Aviv University, for allowing to use their wind tunnel facility.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported in part by the Israel Science Foundation (ISF) [grant number 316/11], in part by the German Israeli Foundation for Scientific Research and Development (GIF) [grant number 1072-6.14/2009] and in part by EuHit project of FP7.