In other embodiments, the rows 50 may be positioned generally orthogonal to {HEAD ~ a direction} of {TAIL ~ an average flow} of a gas 51 through the cavity 14 
of
In other embodiments , the rows 50 may be positioned generally orthogonal to { HEAD ~ a direction } of { TAIL ~ an average flow } of a gas 51 through the cavity 14
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH