超音速ノズルからの適正膨張乱流噴流の時間平均特性

抄録

Pitot impact pressure measurements on the correctly expanded supersonic jet from the axisymmetric nozzle have been performed along the jet centerline and radial direction. The test nozzle was designed by the characteristic method. Also, the flow visualizations have been performed with the three nozzles (these are bell and conical types, and another one is designed by the characteristics method). The design Mach number of these nozzles is 2.4, and the Reynolds number on the correctly expanded condition is 3.5× 10⁶. The total temperature of the jets is equal to the room condition, so we considered only the flow of the cold jet on the effect of temperature. In the present study, the aims are to obtain more knowledge of the mean-flow characteristics and investigate the effect of the nozzle geometry on the correctly expanded supersonic jets. The results are as follows. The progress empirical formulae on the potential core length x_core/D_e, the spreading rate δ_η and the spreading parameter σ were proposed by the investigation of present and previous experimental results, respectively. These parameters are important on the understanding of mean-flow characteristics of the correctly expanded supersonic jets. And the flow visualizations showed that the configurations of supersonic jets from these nozzles were different due to the nozzle geometry, even though the pressure ratios on the nozzles are same condition.