Simultaneous visualization of surface and flow field for a projectile

This paper reports establishment of the simultaneous measurement of the flight attitude and flow field visualization for the near-field pressure measurement experiments in a ballistic range. To measure the flight attitude and flow field visualization for a spherical projectile, the simultaneous visualization method, which is combination of the shadowgraph method and the direct photography, was utilized. It is possible to visualize both the flow field around the projectile and the projectile surface. The angles of pitch, roll and yaw can be calculated from the displacement of line markings on the projectile surface. The image of the projectile by the direct photography is distorted because of the aberration of the optical arrangement, the camera lens and the non-uniform thickness of acrylic windows. Image distortion was calibrated by taking images on actual set-up, so that the accuracy of the angles was improved. In addition, the diffuse reflection light from the projectile surface was confirmed not to influence the flow field visualization. This method is useful for the near-field pressure measurement experiments in a ballistic range. The flight attitude affects the near-field pressure value strongly. Since the near-field pressure with a detailed flight attitude is obtained, its influences can be evaluated using the method which has ability of the flight attitude measurement. In addition, a shock interaction around a projectile can be captured. Graphical Abstract: [Figure not available: see fulltext.]