0 Replies Latest reply on Jun 26, 2012 3:50 PM by Dan Hofstetter

    boundary condition problem

    Dan Hofstetter

      I'm working on a model of a tank with a 1cm thick slotted lid.  The tank is 5.49m long X 2.74m wide X 1.83m tall.  The fan is located at the centroid of the lid, and is blowing down into the tank.  Air exits through the 9 equally-spaced 0.12m wide slots in the lid.  The first and last slot are adjacent to the end walls.  The problem I am having is that the slots don't seem to offer any flow resistance, i.e. I get nearly identical results for gas decay over time with slot widths of 0.12m and 0.06m (same flow rate, 2.67 m^3/s).  I built the model by cutting the slots into the lid, then creating lids for each slot and applying the Environmental Pressure boundary condition to the inside face of the lids.  I'm using 100 kPa for environmental pressure and also for the initial conditions inside the tank since it is open to air. 

       

      Am I doing something wrong?  Is there something else I need to specify when doing this type of simulation?  Would having the fan opening directly adjacent to the center slot cause any issues?  The fan essentially sits directly over one slot, cutting it into two pieces.

       

      The other thing I have noticed is that if I use Inlet Volume Flow at 2.67 m^3/s, I get different results than when using an External Inlet Fan with a fan curve that is essentially flat, 2.67 m^3/s at each value of pressure.  Shouldn't the results be the same?

       

      Thanks,

       

      Dan