Referring to the description of different regimes for the simultaneous flow of gas and liquid in vertical pipes introduced by Y. Taitel and A. Dukler in 1980. The results are shown in the form a crossplot or map with the superficial gas velocity, v_gs, on the x-axis and the superficial liquid velocity, v_ls, on the y-axis. Different maps are constructed for different pipe sizes and fluid properties. The Taitel-Dukler map defines the transition between different flow regimes more closely than other models. Taitel and Dukler also described flow transitions in horizontal pipes.

Reference:
Taitel Y, Barnea D and Dukler AE: 鈥淢odelling Flow Pattern Transitions for Steady Upward Gas-Liquid Flow in Vertical Tubes,鈥?AIChE Journal 26, no. 6 (May 1980): 345-354.