取N=3 1000/3/3600 12.86m/s 0.06×0.12 dln/dn=√uB/B=√13.89×0.06/1286×0.1=0.805 dC=6.491m7 <33~5 5 534%38.0%100%→n=90.34% D=0.24m,N=3取N=3 1000 / 3/ 3600 12.86 / 0.06 0.12 u m s i = =  / / 13.89 0.06/12.86 0.1 0.805 C C i i d d u B u B    = =   =  = d m C  6.49 <3 3～5 >5 5.34% 38.0% 100% →η=90.34% ∴ D=0.24m，N=3