24 Aug 2022
24 Aug 2022

Icing Wind Tunnel Measurements of Supercooled Large Droplets Using the 12 mm Total Water Content Cone of the Nevzorov Probe

Johannes Lucke1,2, Tina Jurkat-Witschas1, Romy Heller1, Valerian Hahn1,3, Matthew Hamman4, Wolfgang Breitfuss5, Venkateshwar Reddy Bora6, Manuel Moser1,3, and Christiane Voigt1,3 Johannes Lucke et al.
  • 1Deutsches Zentrum für Luft- und Raumfahrt (DLR), Institute of Atmospheric Physics, 82234 Wessling, Germany
  • 2Faculty of Aerospace Engineering, Delft University of Technology, 2629 Delft, Netherlands
  • 3Institute of Atmospheric Physics, University of Mainz, 55881 Mainz, Germany
  • 4Collins Aerospace, Uniontown, OH 44685, USA
  • 5Rail Tec Arsenal, 1210 Vienna, Austria
  • 6Institute of Fluid Mechanics, Technical University of Braunschweig, 38108 Braunschweig, Germany

Abstract. Supercooled large droplet (SLD) icing can occur behind the protected surfaces of an aircraft and create severe aerodynamic disturbances, which represent a safety hazard for aviation. Liquid water content (LWC) measurements in icing conditions that contain SLD require instruments that are able to sample unimodal and bimodal droplet size distributions with droplet diameters from 2 to 2000 µm. No standardized detection method exists for this task. A candidate instrument, that is currently used in icing wind tunnel (IWT) research, is the Nevzorov probe. In addition to the standard 8 mm total water content (TWC) collector cone, a novel instrument version also features a 12 mm diameter cone, which might be advantageous for collecting the large droplets characteristic of SLD conditions. In the scope of the two EU projects SENS4ICE and ICE GENESIS we performed measurement campaigns in SLD icing conditions in IWTs in Germany, Austria and the USA. We obtained a comprehensive data set of measurements from the Hotwire, the 8 mm and 12 mm cone sensors of the Nevzorov probe and the tunnel reference instrumentation. In combination with measurements of the particle size distribution we experimentally derive the collision efficiency curve of the new 12 mm cone for median volume diameters (MVDs) between 12 and 58 µm and wind tunnel speeds from 40 to 85 µm. Knowledge of this curve allows us to correct the LWC measurements of the 12 mm cone (LWC12) in particular for the inevitably high decrease in collision efficiency for small droplet diameters. In unimodal SLD conditions, with MVDs between 128 and 720 µm, LWC12 generally agrees within 20 % with the tunnel LWC reference values from a WCM-2000 and an Isokinetic Probe. An increase in the difference between LWC12 and the WCM-2000 measurements at larger MVDs indicates better droplet collision properties of the 12 mm cone. Similarly, the favorable detector dimensions of the 12 mm cone explain a 7 % enhanced detection efficiency compared to the 8 mm cone, however this difference falls within the instrumental uncertainties. Data collected in various bimodal SLD conditions with MVDs between 16 and 534 µm and LWCs between 0.22 and 0.72 g m-3 also show an agreement within 20 % between LWC12 and the tunnel LWC, which makes the Nevzorov sensor head with the 12 mm cone the preferred instrumentation for measurements of LWC in Appendix O icing conditions.

Johannes Lucke et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2022-647', Anonymous Referee #1, 24 Aug 2022
  • RC2: 'Comment on egusphere-2022-647', Alexei Korolev, 15 Sep 2022

Johannes Lucke et al.

Data sets

Icing Wind Tunnel Measurements of Supercooled Large Droplets Using the 12 mm Total Water Content Cone of the Nevzorov Probe: Measurement Data Johannes Lucke, Tina Jurkat-Witschas, Romy Heller, Valerian Hahn, Matthew Hamman, Wolfgang Breitfuss, Venkateshwar Reddy Bora, Manuel Moser, Christiane Voigt

Johannes Lucke et al.


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Short summary
Flight testing in icing conditions requires instruments that are able to accurately measure the liquid water content of supercooled large droplets (SLD). This work finds, that the 12 mm cone of the Nevzorov hot-wire probe has excellent collection properties for SLD. We also derive a correction to compensate for the low collision efficiency of small droplets with the cone. The results provide a procedure to evaluate LWC measurements of the 12 mm cone during wind tunnel- and airborne experiments.