Investigation of steady and pulsed energy addition into supersonic flow

The influence of steady energy addition into the flow was investigated at Mach numbers 3 and 5 by a low-voltage DC-arc discharge located upstream of conically-nosed and spherically-blunted bodies. The flow-field structure arising due to the bow-shock/heated-wake interaction and the effects of the bow-shock intensity and of the heating power on the drag reduction of different non-slender bodies are analyzed numerically and experimentally. Results demonstrate the existence of an optimum heating rate, providing a maximum effectiveness of energy addition. The influence of various parameters characterizing the single- and double-pulse energy addition upstream of a blunt body (distance between the deposition point and the body, amount of the energy and time delay between the pulses) on the topology of the supersonic flow was studied experimentally and numerically at Mach 2. The obtained pressure-time diagram at the upstream stagnation point of the body as well as some significant topological properties of the bow-shock / heated-bubble interaction, like shock deformation and reflection, as well as the evolution of the heated bubble into vortex rings downstream, are analyzed as resulting from the shock-decelerated spherical “light-gas” inhomogeneity. The evolution and topology of the interfering heated bubbles by double-pulse ED show the significance of vorticity generation initiated by blast-waves coming from the neighboring bubbles