To understand / evaluate behaviour of these complex jets freestream interactions, experiments were carried out in the freestream Mach number range of 0.6 to 1.8 varying jet pressure ratios in the range of 1 to about 15 on a twin jet afterbody configuration. Test results show that afterbodyudtotal drag in general increased (for the Mach number range of this investigation) with the increase in jet pressure ratios due to the entrainment effect of the twin supersonic nozzle jets flow for this afterbody configuration. Oil flow visualization studies also show the intense effect of twinudjets freestream interactions at transonic speeds as is indicated by large separated flow regions in and around the base region / nozzles external surface, resulting in relatively a higher transonic drag.ud
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