275 . Periodic waves from a supersonic jet.

2. 255. Airplane model in free flight at M=1.L Shadow­graphs show a winged model launched into atmospheric air from a gun, as in figure 252. The bow wave is margin­ally attached at this slightly supersonic speed. In the plan view above, the wings are lifting, as shown by trailing vortices from the tips. In the side view below, the herringbone pattern is produced by pressure pulses from grooves in the wing that trip the boundary layer to make it turbulent over the rear half. NASA photography courtesy of W. G. Vincenti

3. 259. Cone-cylinder in supersonic free flight. A cone-cylinder of 12.5 semi-vertex angle is shot through air at M = 1.84. The boundary layer becomes turbulent shortly behind the vertex, and generates Mach waves that are visible in this shadowgraph. Photograph by A. C. Charters

4. 260. Shock-free forebody. At Mach number 2.1 the concave nose of this body of revolution shows the smooth compression required for a shock-free diffuser. The bow shock wave forms only away from the body, as the axisymmetric counterpart of figure 227. The tip was unfortunately bent during firing, which generated the weak shock wave there. Photograph from Transonic Range, U. S. Army Ballistic Research Labora­tory

5. 266. Sphere at M=l*53. A shadowgraph catches a V^-inch sphere in free flight through air. The flow is subsonic behind the part of the bow wave that is ahead of the sphere, and over its surface back to 45. At about 90 the laminar boundary layer separates through an oblique shock wave, and quickly becomes turbulent. The fluc­tuating wake generates a system of weak dis­turbances that merge into the second shock wave. Photograph by A. C. Charters

6. 269. Sphere at M = 4.0L This shadowgraph of a V2-inch sphere in free flight through atmospheric air shows boundary-layer separation just behind the equator, accompanied by a weak shock wave, and the formation of the N-wave that is heard as a double boom far away. The vertical line is a refer­ence cord. Photograph by A. C. Charters

7. 270. Sphere at M = 7.6. A nylon sphere is flying through atmospheric air. At this high Mach number the bow shock wave is forced close to the front of the body. Mach waves run­ning downstream from the surface indicate the end of the subsonic region. U.S. Navy photograph from Naval Surface Weapons Center, Silver Springy Maryland

8. 273. Hypersonic flow past power4aw bodies* Shadow­graphs show the bow wave in air at M = 8.8 for bodies of revolution whose radius varies as a power of axial distance.The exponents are ¾,1/2 (a paraboloid of revolution), !/3, and 1/10. Freeman, Cash & Bedder 1964, courtesy of Aero­dynamics Division, National Physical Laboratory

9. 275. Periodic waves from a supersonic jet.

10. 276, Long* and short-duration photographs of a supersonic jet. Dry air flows from a converging conical nozzle with an exit diameter of 1 cm. The ratio of stagna­tion to atmospheric pressure is 3.13, giving an axisymmetric jet of Mach number 1.4. The upper shadowgraph, with an exposure time of 10"2 s, shows the mean flow, with a series of expansion and compression waves. The lower photograph, at 0.5 x 10"6 s, shows the more complicated instantaneous structure. Photographs by N. ]ohannesen

11. 278. Starting process in a nozzle. The incident shock wave, traveling at a shock Mach number of 3, has just passed through a plane nozzle. Behind it are several con­tact surfaces containing vortices (cf. figure 240). Between them and the nozzle throat is a second shock wave, directed upstream but being swept downstream, and caus­ing the boundary layers to separate. Mach waves from the walls show the supersonic flow established downstream of the throat. Amann 1971