This can be achieved with a Profile Function. While the documentation only explains the use of spatial profiles, it can also be used for temporal profiles. This is an example profile file for a time-varying velocity: [Name] My Profile [Spatial Fields] t [Data] t [ s ], u [ m / s ] 0, 0 1, 0.5 2, 0.8 3, 1.2 This file can be loaded into CFX-Pre with Tools > Initialize Profile Data. In the boundary condition the function can be called to define the inlet velocity as follows: My Boundary.u( t) The specific values for the timesteps are interpolated from this profile. Keywords: transient, temporal, profile, 1D, boundary condition, interpolation