In this talk, I will first highlight some interesting results from the BNL Beam Energy Scan (BES) workshop which will be held on Feb. 26-27, 2015. The measured bulk flow observables at these collision energies and their collision energy dependence has not been understood on a quantitative level yet. This motivates us to improve our current theoretical modelling for the heavy-ion collisions at these low collision energies. I will then discuss our recent development of including baryon diffusion to model the relativistic heavy-ion collisions from 7.7 A GeV to 200 A GeV for the RHIC BES program. The consequences from the existences of baryon current propagation, baryon diffusion, and non-boost invariant initial conditions to the final flow observables will be discussed.
