Comparison of different droplet measurement techniques in the Braunschweig Icing Wind Tunnel

Abstract. The generation, transport and characterization of supercooled droplets in multiphase wind tunnel test facilities is great importance for conducting icing experiments to better understand cloud microphysical processes such as coalescence, ice nucleation, accretion riming. To this end, a spray system has been developed, tested calibrated the Braunschweig Icing Wind Tunnel. Liquid size range 1 150 µm produced by pneumatic atomizers were accelerated velocities between 10 40 m s?1 temperatures 0 ?20 ?C. Thereby, liquid water contents 0.07 2.5 g m?3 obtained section. conditions stable reproducible within 3 % standard variation median volumetric diameter (MVD) 7 deviation content (LWC). Different instruments integrated measuring particle distribution (PSD), MVD LWC. Phase Doppler interferometry (PDI), laser spectroscopy with fast droplet probe (FCDP) shadowgraphy systematically compared present conditions. MVDs measured three agreed 15 8 35 showed high coefficients determination (R2) 0.985 FCDP 0.799 respect PDI data. Between 56 MVD, data exhibit low bias PDI. instruments' trends biases selected are discussed. LWCs determined from mass flow calculations 0.07–1.5 measurements bulk phase rotating cylinder technique (RCT) above-mentioned single-particle instruments. For RCT, agreement approximately 20 LWC was achieved. 84 measurement points LWC<0.5 agree ±0.1 m?3. Using different techniques, comprehensive calibration achieved, which prerequisite providing well-characterized tests aerospace, turbines power networks.