Moving the vent location to either side of the vent follower causes fluid or {HEAD ~ gas} to escape from one or {TAIL ~ the other cell} 
Moving the vent location to either side of the vent follower causes fluid or { HEAD ~ gas } to escape from one or { TAIL ~ the other cell }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL REL REL OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL