STUDY ON EXPLANATION OF DIGITAL IMAGE-PRESSURE MEASUREMENT TECHNOLOGY AND SELF-EXITED OSCILLATION OF FLOW WITH SHOCK WAVES BY THE WAY

本文通过流动显示、压力测量和噪声测量等方法，研究了扩张喷管射流的振动、自激振荡和噪声之间的关系。采用纹影法进行瞬态流动显示。总压的压力波动是由一个压力传感器组装到一个总压探头，并进一步测量线性标尺的声压级的噪声测量。利用FFT分析仪对压力和噪声的频率进行了分析。结果表明，总压脉动对喷流噪声有一定的影响。并对汽车消声器模型二维管道内的激波结构进行了研究。通过数值模拟得到的密度分布图与纹影法得到的可视化照片进行了比较。研究了各消声器内的压力、密度、速度分布，并对激波结构进行了分析。结果表明，各模型在激波结构作用和衰减方面存在差异。

In this study, the relation between vibration the self-induced oscillation and noise of jet flow issuing from divergent nozzle were studied by the flow visualization, pressure measurement and noise measurement. The instantaneous flow visualization were taken by schlieren method. The pressure fluctuation of total pressure was measured by a pressure transducer assembled into a total pressure probe and further, the noise of sound pressure level for the linear scale was measured. The frequency of the pressure and noise was analyzed by FFT analyzer. As a result, it was found that the jet noise was influenced by the total pressure fluctuation. Furthermore, the structure of the shock wave occurred in the two dimensions pipe of a muffler model for automobile was studied. The density distribution chart that was obtained by numerical simulation was compared to the visualization photograph by the schlieren method. The distribution of the pressure, density, speed of flow in each muffler was investigated, and shock wave structure was illuminated. As the result, the differences of the shock wave structure action and decrease of each model were clarified.