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The formation of bubbles on an orifice plate involves a moving contact line, especially in case of poor wetting conditions. The dynamics of the moving contact line and contact angle have a significant impact on the bubble departure size. This work presents visualization and numerical simulations on gas bubble formation on submerged orifices of different wettabilities and diameters. The transient bubble shape (image), departure diameter, contact line diameter, apparent contact angle, neck diameter, and neck height are obtained under various conditions. Under certain wetting and flow conditions, the relationship between moving contact line and apparent contact angle can be relatively well defined. However, this relationship cannot be generalized for other conditions. Two kinds of contact line models have been re-evaluated against experiments, one is a contact line velocity dependent model (Model-A) and the other is a stick-slip model (Model-B). Numerical simulations were performed using Model-B and the results show good agreement with the experiments. The bubble formation data provided are useful for supporting and verifying the numerical simulations. [ABSTRACT FROM AUTHOR]