Hello everybody.

I am confronted with the following problem. I want to model a truck whose motor is started in a hall and which then leaves the hall leaving the exhaust fumes behind. The aim is to study the flow of the exhaust fumes while and after the truck is leaving the hall, ultimately to place some ventilation equipment to control the exhaust spreading.

I started in 2D just for simplicity, represented the hall by a rectangle (bc type wall), the gate with a pressure inlet boundary condition. The truck is also represented by a rectangle (bc type wall; aerodynamic resistance is not the focus), and the exhaust pipe is a velocity inlet boundary conditon with specified mass fractions of the gases that I want to study. The truck has to move over a distance that spans several times its length.

I chose for dynamic mesh (local remeshing option) to model the movement of the truck. I managed to move the truck nicely towards the gate with the mesh adjusting accordingly, but as soon as the truck touches the gate (pressure inlet bc) some mesh cells become negative in volume and iteration aborts with an error message.

Does any of you have an idea of how I can handle the problem that the wall of the truck intersects the pressure inlet boundary condition of the gate.

I fear that you can't simply let the truck "exit" the domain. Probably you must model even the distance the truck runs along outside the gate.

Good luck

Edi.

Sorry, I forgot to mention that deforming the truck so that it does not touch the gate (making it shrink in length as it approaches) is not an option since I don't have Microsoft Visual Studio available which you need for compiled UDFs which as I understand are the only way to realize a deforming mesh.