The process of bubble formation from an orifice submerged in liquid with constant gas flow is studied by numerical simulations using an OpenFOAM volume-of-fluid solver named interIsoFoam. The computed results show that the detached bubble size tends to increase with the gas flow rate, orifice size, surface tension, liquid contact angle, etc. in qualitative agreement with most previous authors. For a given orifice size and liquid properties, there exists a critical gas flow rate above which detached bubbles will combine via coalescence known as bubble pairing. The detached bubble size seems insensitive to the contact angle when the liquid adequately wets the orifice wall, but can increase substantially if the contact angle is increased beyond a critical value resulting in contact line motion on the horizontal orifice surface. The value of such a critical contact angle increases with the orifice size as well as gas flow rate. Such revelations would logically suggest that the usage of reduced orifice size for generating smaller bubbles could be more challenging and practically difficult with constant gas flow for sub-millimeter orifices.