Wind Tunnel Measurements of the Response of Hot-Wire Liquid Water Content Instruments to Large Droplets

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.

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Design and Finite Element Analysis of Airborne Cloud Liquid Water Sensors

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.301-303.1744 ◽

2011 ◽

Vol 301-303 ◽

pp. 1744-1748

Author(s):

Qing Quan Liu ◽

Wei Dai ◽

Xiao Wei Tang

Keyword(s):

Finite Element ◽

Wind Tunnel ◽

Water Content ◽

Liquid Water ◽

Signal Interference ◽

High Water Content ◽

Hot Wire ◽

Weather Modification ◽

Cloud Liquid Water ◽

Heat Transfer Theory

Airborne cloud liquid water content (CLWC) sensors have been used in weather observation and weather modification for years. However, traditional CLWC sensors are relatively bulky and heavy. Additionally, it is inconvenient to use wind tunnel to calibrate traditional sensors. In order to meet the need of wind tunnel calibration tests, reduce the wind signal interference and reduce the cooling effect of high water content cloud, two new types of hot-wire water meter content sensors are designed in this paper. Using steady-state heat transfer theory, a finite element method is used to simulate temperature distribution of the new water content sensors, including the scenario in which cloud water droplets evaporates as colliding the sensors. In order to minimize sensor error, convection is also considered in the finite element model. Through the numerical analysis of the two new types of hot-wire water content sensors, it is concluded that the sensors designed in this work are able to reduce the wind interference error and extend the CLWC measurement range of the instrument.

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Response of the Nevzorov hot wire probe in Arctic clouds dominated by very large droplet sizes

Atmospheric Measurement Techniques Discussions ◽

10.5194/amtd-2-1293-2009 ◽

2009 ◽

Vol 2 (3) ◽

pp. 1293-1320

Author(s):

A. Schwarzenboeck ◽

G. Mioche ◽

A. Armetta ◽

A. Herber ◽

J.-F. Gayet

Keyword(s):

Water Content ◽

Liquid Water ◽

Collection Efficiency ◽

Supercooled Liquid ◽

Liquid Water Content ◽

The Arctic ◽

Asymmetry Factor ◽

Pure Liquid ◽

Hot Wire ◽

Data Set

Abstract. During the airborne research mission ASTAR 2004 (Arctic Study of Tropospheric Aerosols, Clouds and Radiation) performed over the island of Svalbard in the Arctic a constant-temperature hot-wire Nevzorov Probe designed for aircraft measurements, has been used onboard the aircraft POLAR 2. The Nevzorov probe measured liquid water (LWC) and total condensed water content (TWC) in supercooled liquid and partly mixed phase clouds, respectively. As for other hotwire probes the calculation of LWC and/or TWC (and thus the ice water content IWC) has to take into account the collection efficiencies of the two separate sensors for LWC and TWC which both react differently with respect to cloud phase and what is even more difficult to quantify with respect to the size of ice and liquid cloud particles. The study demonstrates that during pure liquid cloud sequences the ASTAR data set of the Nevzorov probe allowed to improve the quantification of the collection efficiency, particularly of the LWC probe part with respect to water. The improved quantification of liquid water content should lead to improved retrievals of IWC content. Simultaneous retrievals of LWC and IWC are correlated with the asymmetry factor derived from the Polar Nephelometer instrument.

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A hot-wire instrument to measure liquid water content for use in the laboratory

Journal of Physics E Scientific Instruments ◽

10.1088/0022-3735/19/6/008 ◽

1986 ◽

Vol 19 (6) ◽

pp. 436-438 ◽

Cited By ~ 7

Author(s):

W D Keith ◽

C S Mill ◽

C P R Saunders

Keyword(s):

Water Content ◽

Liquid Water ◽

Liquid Water Content ◽

Hot Wire

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A Multiwire Hot-Wire Device for Measurment of Icing Severity, Total Water Content, Liquid Water Content, and Droplet Diameter

43rd AIAA Aerospace Sciences Meeting and Exhibit ◽

10.2514/6.2005-859 ◽

2005 ◽

Cited By ~ 14

Author(s):

Lyle Lilie ◽

Edward Emery ◽

J. Strapp ◽

Julia Emery

Keyword(s):

Water Content ◽

Liquid Water ◽

Droplet Diameter ◽

Liquid Water Content ◽

Total Water Content ◽

Hot Wire ◽

Total Water

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Response of the Nevzorov hot wire probe in clouds dominated by droplet conditions in the drizzle size range

Atmospheric Measurement Techniques ◽

10.5194/amt-2-779-2009 ◽

2009 ◽

Vol 2 (2) ◽

pp. 779-788 ◽

Cited By ~ 11

Author(s):

A. Schwarzenboeck ◽

G. Mioche ◽

A. Armetta ◽

A. Herber ◽

J.-F. Gayet

Keyword(s):

Water Content ◽

Liquid Water ◽

Collection Efficiency ◽

Supercooled Liquid ◽

Liquid Water Content ◽

The Arctic ◽

Asymmetry Factor ◽

Pure Liquid ◽

Hot Wire ◽

Data Set

Abstract. During the airborne research mission ASTAR 2004 (Arctic Study of Tropospheric Aerosols, Clouds and Radiation) performed over the island of Svalbard in the Arctic a constant-temperature hot-wire Nevzorov Probe designed for aircraft measurements, has been used onboard the aircraft POLAR 2. The Nevzorov probe measured liquid water (LWC) and total condensed water content (TWC) in supercooled liquid and partly mixed phase clouds, respectively. As for other hotwire probes the calculation of LWC and/or TWC (and thus the ice water content IWC) has to take into account the collection efficiencies of the two separate sensors for LWC and TWC which both react differently with respect to cloud phase and what is even more difficult to quantify with respect to the size of ice and liquid cloud particles. The study demonstrates that during pure liquid cloud sequences the ASTAR data set of the Nevzorov probe allowed to improve the quantification of the collection efficiency, particularly of the LWC probe part with respect to water. The improved quantification of liquid water content should lead to improved retrievals of IWC content. Simultaneous retrievals of LWC and IWC are correlated with the asymmetry factor derived from the Polar Nephelometer instrument.

Download Full-text