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- Title
On the Use of Hot-Wire Anemometers for Turbulence Measurements in Clouds.
- Authors
Siebert, Holger; Lehmann, Katrin; Shaw, Raymond A.
- Abstract
The use of a hot-wire anemometer for high-resolution turbulence measurements in a two-phase flow (e.g., atmospheric clouds) is discussed. Experiments in a small wind tunnel (diameter of 0.2 and 2 m in length) with a mean flow velocity in the range between 5 and 16 m s-1 are performed. In the wind tunnel a spray with a liquid water content of 0.5 and 2.5 g m-3 is generated. After applying a simple despiking algorithm, power spectral analysis shows the same results as spectra observed without spray under similar flow conditions. The flattening of the spectrum at higher frequencies due to impacting droplets could be reduced significantly. The time of the signal response of the hot wire to impacting droplets is theoretically estimated and compared with observations. Estimating the fraction of time during which the velocity signal is influenced by droplet spikes, it turns out that the product of liquid water content and mean flow velocity should be minimized. This implies that for turbulence measurements in atmospheric clouds, a slowly flying platform such as a balloon or helicopter is the appropriate instrumental carrier. Examples of hot-wire anemometer measurements with the helicopter-borne Airborne Cloud Turbulence Observation System (ACTOS) are presented.
- Subjects
ANEMOMETER; METEOROLOGICAL instruments; CLOUDS; TURBULENCE; WIND speed measurement; WIND tunnels
- Publication
Journal of Atmospheric & Oceanic Technology, 2007, Vol 24, Issue 6, p980
- ISSN
0739-0572
- Publication type
Article
- DOI
10.1175/JTECH2018.1