Study of Oscillation Characteristics of Shock Trains Formed in Supersonic Internal Flow and its Suppressing Method

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(1)Shock trains and pseudo-shocks have been formed insupersonic internal duct flows due to the interaction between a normal shock wave and a turbulent boundary layer. The three dimensional flow structure of the shock trains and pseudo-shocks has been investigated numerically and experimentally, and the complicated shock structure was made clear.(2)Multiple shocklets generated in a two-dimensional transonic diffuser was observed with a high speed camera combined with schlieren method, and the motions of each shock wave have been recorded. The experimental results were compared with the calculated values assuming a pressure disturbance given by the sine function at the channel exit, and it is shown that the experiments agree well with the calculated results.(3)From the above study, it is concluded that the multiple shocklet pattern appears when the amplitude of disturbance is not large and the diverging part of the channel downstream of the ordinary shock wave is long.(4)The self-excited shock wave oscillation in two-dimensional supersonic and transonic diffusers was investigated experimentally. The results show that a pressure disturbance is generated near the stem of the shock wave and it moves downstream. In the downstream region where the boundary layer becomes highly turbulent, another disturbance is generated and it causes the shock wave oscillation.