Discussion Forum

I am trying to mode a CFD problem with a boundary having two different boundary conditions of its two sides: one side is open boundary, another is slip wall which will move in an opposite direction as prescribed displacement. And here I introduce the Moving mesh Mode to simulate the free displacement of open boundary and prescribed displacement of slip wall. I create pairs for this two boundaries and set slip wall boundary as source. Here I set boundary identity pairs condition as continuity. At first two boundary detached. but Once the open boundary began to recontact again the solver become hard to progress and stops due to error like "may reach a singularity"?
Then, I changing the model a little. I build two separated geometries one is fluid with free up and side boundary . another one is "solid"(I define high viscosity and density ) with all slip wall boundaries. I set there is a little distance between them. Here I create continue boundary identity pairs condition for open boundary and slip wall and set slip wall as source. here I introduce the Moving mesh Mode to simulate the free displacement of open boundary and slip wall geometry keep still. The simulation result is that the free open boundary will move toward slip wall due to gravity but once they began to contact, the solver become hard to progress and finally stops.
Help me out here, please! The attachment is my model.