Make a heavy fluid flow through a space

Hi, 

This may be hard to explain. Essentially my class are doing material studies on actual materials. Once we do our study we have to replicate it in grasshopper.  I'm using hot wax and pouring it through a 1/4" x 1/4" mesh. Some areas are cut out so it would be 1/4" x 1/2" or 1/2" x 1/2". Through the bigger openings more wax falls through. I'm trying to create a definition that articulates this. Then I could move the opening sizes and the flow would change accordingly. Attached are some pictures of my studies. The grasshopper definition doesn't have to look like this, it could be simplified, however, it needs to take on similar properties. I don't even know how to start, help!!!! 

Thanks, 

Jordan