Experimental studies are performed for the near- and far-field characteristics of a plug nozzle jet with the objective to see the effect of truncation of the plug on mean flow characteristics of the jet and its control using vortex generators (VGs). To this end, the plug is truncated at 50%, 40%, and 30% of the axial length from the throat, and mean flow characteristics are studied by the schlieren technique and a pitot pressure survey. Nozzle pressure ratio (NPR) is varied from 2 to 8 for a Mach 1.8 nozzle designed to give correctly expanded flow at NPR 5.74. During over-expansion mode, all the truncation levels are observed to increase core length and strengthen shock cells of the jet, whereas, during under-expansion, truncation up to 50% of the plug is not found to alter the core length. To promote mixing, two rectangular VGs of different aspect ratios but same blockage area of 2% are attached to the base of the truncated plugs. The influence of pressure ratio on the flow structure of controlled and uncontrolled jets is discussed in detail. Results have shown VGs to be effective in mixing enhancement and weakening of shock cells over the nozzle pressure ratios studied.

对塞子喷嘴射流的近场和远场特性进行了实验研究，目的是观察塞子的截断对射流的平均流量特性的影响及其使用涡流发生器（VG）的控制。为此，将塞子从喉部截断为轴向长度的50％，40％和30％，并通过schlieren技术和皮托管压力调查研究平均流量特性。对于Mach 1.8喷嘴，喷嘴压力比（NPR）从2更改为8，以便在NPR 5.74时提供正确扩展的流量。在过度扩张模式下，观察到所有截断水平都会增加芯长度并增强射流的冲击波，而在过度扩张过程中，未发现高达50％的塞子截断会改变芯长度。为了促进混合，将两个长宽比不同但阻塞面积相同为2％的矩形VG连接到截头的底部。详细讨论了压力比对受控射流和非受控射流的流动结构的影响。结果表明，在所研究的喷嘴压力比范围内，VGs可有效混合增强和减弱冲击单元。