a plurality of air inlets 32 at {HEAD ~ the lower periphery} of {TAIL ~ the inner tube} 30, and 
of
a plurality of air inlets 32 at { HEAD ~ the lower periphery } of { TAIL ~ the inner tube } 30 , and
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH