1. F/1 Laboratory studies of the form and oscillations towards breakup of falling raindrops in the Mainz Wind Tunnel Stephan Borrmann, Subir K. Mitra, Karoline Diehl, Miklós Szakáll

2. Objectives Measurement of the time averaged axis ratio of oscillating millimetre size drops with equivalent diameters (Do) above 3 mm Evaluation of the time averaged axis ratio of oscillating drops with equivalent diameters lying between 1.1 mm and 3 mm Experimental determination of the oscillation frequency of all millimetre size drops Comparison of the experimentally obtained dynamic average axis ratios against results of various drop deformation models Evaluation of the dynamic time average form of millimetre size drops after inducing oscillations through collisions

3. Mainz Vertical Wind Tunnel Hauptkammer Netze Strömungsgleichrichter Kontraktionssektion Beobachtungssektion Vakuumpumpe Schalldüse Partikelfilter Heizung/Kühlung Befeuchtung/Trocknung

4. Axis ratios ~ 0.97 @ 1mm ~ 10 µm

5. Oscillation frequencies ~ 300 Hz max. ~ 2000 fps

6. The camera MotionPro X-3 Redlake Inc.  2000 fps @ 1280x512 resolution  12x12 µm pixel size  10-bit CMOS monochrom sensor  16 GB memory (~12 sec)  Ethernet interface, analog VideoOut

7. Camera in use

8.  constant lighting  measurements for drops D 0 >3 mm  axis ratio and  oscillation frequency determination Next steps…