Supplementary Materials: Video footage for some example experiments is made available. Video S1: Slug_slow_Qgas11.5_Qliq7.3.mp4 (Qgas = 11.5 m3/h and Qliq = 7.3 m3/h), Video S2: Slug_fast_Qgas43.2_Qliq21.2.mp4 (Qgas = 43.2 m3/h and Qliq = 21.1 m3/h), Video S3: Wavy_Qgas46.1_Qliq2.6.mp4 (Qgas = 46.1 m3/h and Qliq = 2.6 m3/h), Video S4: Stratified_Qgas46.6_Qliq1.1.mp4 (Qgas = 46.6 m3/h and Qliq = 1.1 m3/h).