there are two techniques which were used in the boundary conditions for the simulation of flow regimes and especially slug flow.

In the first technique, the initial condition is set in such a way that the gas-liquid volume fraction has a 50-50 share in volume with only liquid occupying the bottom of the pipeline and gas phase filling the top of the liquid surface.

The second technique, the perturbations were as a result of the volume fraction of liquid phases entering the pipe as a function of time

y1=y0+Asin((2*pi*x/m)+pi)

How can we use the second technique in Ansys Fluent?(need udf? how write?)