[NumericalGuy]

In Star CCM, I want to use surface injector for lagrangian water droplets. Under surface injector, Star CCM wants me to define surface where droplets are injected, injection velocity and mass flow rate. However, when we consider water's density is constant, which is the case for our problem, we should not give all of these three variables because of conservation of mass. For example, when you define surface area and velocity, you don't need to define mass flow rate. My question is why does Star CCM ask all of these three variables? I wonder if Star CCM does not use one of these parameters as we think? And also why program does not give an error when we use parameters not satisfying conservation of mass (f.e., mass flow rate= 10 kg/s, velocity= 20 m/s, area=1 m^2, I can give all of these parameters and program contiinues to work, why?)