the UDF values are steady and within the range. since in the UDF, I defined kl(mass transfer coefficient in liquid phase) based on energy dissipation rate and a(interfacial area) is a function of air volume fraction and constant bubble size. They look ok.
Another problem is for the systems that dont overshoot and run til the steady state value, the max dissolved oxygen concentration that they reach is close to 0.0065. However, based on Henry's constant and absolute pressure it should go up to 0.008. I can not figure out why that happens