Thanks for the reply. 

They are experimental work I am using to validate my CFD model, so no they are not using any software. This experimental work is reported in two papers entitled: Consequences of a 12-mm diameter high pressure gas release on a buried pipeline. Experimental setup and results (Houssin-Agbomson et al., 2018) AND Experimental study and modelling of the consequences of small leaks on buried transmission gas pipeline (Bonnaud et al., 2018) (If this is in anyway a helpful information) 

Here is some helpful information: 

This is the geometry I described in the previous post: the soil is down, the atmosphere is up. 

  Geometry Image

In this geometry, there is soil which includes everything down except the pipeline and the lower part of the hole. There is atmosphere upwards. There is the fluidinpipe which is the pipe itself that I patch as having methane since the beginning. The hole is constructed in a way that it has an upper part inside the soil (part of the soil) and a lower part inside the pipeline (as part of the pipeline) and the part that is crossing the pipeline is named as interface1 and interface2 from both sides and defined in the mesh interface and named hole. The cell zones and the named selections are shown in the following figures. 

Cell Zones Named Selections

For the boundary conditions, they are shown in the following pictures: inlet and outlet of the pipe are pressure inlet with only methane. The sides of the atmosphere are specified as pressure outlet of 0 barg. The sides of the soil are walls. Using this configuration made me achieve my goal to maintain the desired pressure that I need to test inside the pipeline. 

Boundary Conditions 1 Boundary Conditions 2

Thank you for your time and help,

Best regards,