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ABSTRACT OF PART I:
The behavior of an initially plane, strong shock wave propagating into a conical convergence is investigated experimentally and theoretically. In the experiment a [...] half-angle cone is mounted on the end of a pressure-driven shock tube. Shock waves with initial Mach numbers varying from 6.0 to 10.2 are generated in argon at a pressure of 1.5 torr. During each run local shock velocities at several positions along the cone axis are measured using a thin, multi-crystal piezoelectric probe inserted from the vertex. This technique produces accurate velocity data for both the incident and reflected shock waves. In the corresponding analysis, a simplified characteristics method is used to obtain an approximate solution of the axisymmetric diffraction equations derived by Whitham (1959).
Both the shock velocity measurements and the axisymmetric diffraction solution confirm that the incident shock behavior is dominated by cyclic diffraction processes which originate at the entrance of the cone. Each diffraction cycle is characterized by Mach reflection on the cone wall followed by Mach reflection on the axis. These cycles evidently persist until the shock reaches the cone vertex, where the measured velocity has increased by as much as a factor of three. Real-gas effects, enhanced in the experiment by increasing the initial Mach number and decreasing the pressure, apparently alter the shock wave behavior only in the region near the vertex. Velocity measurements for the reflected shock within the cone show that the shock velocity is nearly constant throughout most of the convergence length.
ABSTRACT OF PART II:
The thermodynamic conditions behind the incident and reflected shock wave close to the vertex of a convergent channel are investigated spectroscopically. The investigation was initiated in order to better determine the possible uses of such a geometrical device as a tool for high temperature plasma research. Using argon at an initial pressure of 1.5 torr, the shock Mach number prior to the entrance of the cone is 10.2. Two windows are mounted at x/1 = 0.9 in the cone, where the Mach number has increased to 24, and the emitted radiation is monitored for both time-resolved (Monochromator - Photomultiplier) and time-integrated (Spectrograph) analysis. The relative line intensity method is used to measure the electron te...