On Energy Separation by Aerodynamic Processes

Abstract

Expressions for Damping Matrices in Linear Vibration Problems P. LANCASTER 256 F RECENT CONTRIBUTIONS to the Readers' Forum have given further consideration to the heating effects in the Hartmann generator which were first investigated by Sprenger. Interest seems now to be concentrated on certain unsteady-flow phenomena associated with supersonic exciting jets: alternating swallowing and spilling of the jet accompanied by the movement of pressure pulses out of and into the resonator. Recent attempts to analyze the heating process' 4 have used models based on these unsteady phenomena and have hinged on the question of whether or not the pressure pulses steepen into shocks. I t seems judicious to recall at this time that Sprenger found very large heating effects for subsonic jets also—provided that turbulence was introduced into the jet. (He used a fine nylon thread across the nozzle to accomplish this.) This subsonic heating was also observed by Sibulkin and Vrebalovich. I t seems quite impossible to explain it using the shock-tube theories presently being formulated. Sprenger found too that the heating produced within a resonance tube by supersonic jets was increased (by a factor as great as four) by the introduction of turbulence. Another aerodynamic-heating effect was reported in the Readers' Forum by Glassman and John. They discovered that the total temperature increased along the center line of both supersonic and subsonic free jets, the ambient and jet total temperatures being equal. The rise in temperature began only at the end of the potential core of the jet. The nozzle used in the supercritical case was designed to produce a shockless jet.