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