抄録
Flow structure in the near field of an annular jet is investigated by means of LDV for two inner diameters of the annular nozzle. The jet leaves the nozzle exit with an inward velocity component and a recirculating region is formed between the nozzle and anstagnation point licated on the jet center line near x/d_m=0.8 for both nozzles. The streamwise extent of recirculating region l_s/d_m is aractically constant; 0.8 for exit velicities greater than 12m/s and l_s does not go beyond D with approaching U_0 to zero.
