Schlieren pictures over one period of shock wave oscillation

At this operating condition, the generic bump is controlled-oscillated in bending mode shapes at frequency between 10 and 200Hz. For each oscillating frequency, the synchronized data of the bump motion, shock wave movement and static pressure flictuations are acquired. The shock wave motion is mea­sured at one vertical location corresponding to 15mm (y/H = 0.25) over the top of the bump neutral position (it is symbolized by the white dashed arrows in Figure 3). Figure 5b shows successive pictures of this shock wave oscillat­ing at 10Hz oscillation frequency. A reference line indicates the mean location of the shock wave (67% of the bump chord). From t’=0 to t’=0.250, the shock wave moves through its mean position in an upstream direction. From t’=0.500 to t’=0.750, the shock wave moves again through its mean position in a down­stream direction. Due to the sinusoidal oscillation of the bump, the shock wave

stays a longer time in the two extreme positions (upstream and downstream) and crosses quickly its mean position during one period at 10Hz bump os­cillatory frequency. Figure 5a shows in the same way one oscillation of the vertical part of the shock wave at 200Hz excitation frequency. These pictures demonstrate a movement close to be sinusoidal.