An apparatus, designed to simulate bubbling of a sieve tray operated in froth regime, was employed. Bubble contact angles in and above the incipient weeping regime for an air-water-plexiglas system were investigated. The influence of both liquid cross-flow and gas up-flow upon bubble contact angles was examined. A model considering the influence of liquid cross-flow was developed to predict bubble size from a sieve hole in froth operation regime. The comparison shows that the bubble sizes predicted by the present model are consistent with our experimental values and the available published experimental data. An apparatus, designed to simulate bubbling of a sieve tray operated in froth regime, was employed. Bubble contact angles in and above the incipient weeping regime for an air-water-plexiglas system were investigated. The influence of both liquid cross-flow and gas A model considering the influence of liquid cross-flow was developed to predict bubble size from a sieve hole in froth operation regime. The comparison shows that the bubble sizes predicted by the present model are consistent with our experimental values ​​and the available published experimental data.