Flow Velocity Measurements in a T Tube

Abstract

The flow velocity of a T-tube plasma has been measured by recording the attenuation of a known shock wave propagating through the T-tube flow. This technique yields results with typical accuracies of 0.1 km/sec which is about 10% of the velocity of the probing shock. The interpretation of the results invites a comparison of the T-tube flow field with an overexpanded detonation or breakdown wave in the high-velocity regime and with a radiation driven shock front in the low-velocity regime.

Overdriven Supersonic Heat Waves

“…The luminous front (which can be interpreted as a heat wave; Strachan et al 1972) is the leading front up to tl = 4 JlS. A shock wave develops at t 1, when a perturbation has caught up with the heat wave.…”

“…The change in the mode of propagation occurs at the instant that the evolution of the heat wave intersects the CJ (Chapman-Jouguet) line. Physical examples of such decaying heat waves include the radial expansion of HII regions around hot young stars, as discussed in the astrophysical literature (Axford 1961); expanding laser sparks (Daiber and Thompson 1967); the expanding fire ball of a nuclear explosion (Zeldovich and Raizer 1966); the plasma produced by exploding wires, and the plasma which escapes out the end of a pulsed capillary arc (Cross et al 1971). These decaying heat waves exhibit the same general fluid behaviour (treating the flows by arguments similar to the onedimensional) although the scale lengths vary from a few millimetres and tens of nanoseconds for decaying laser sparks to light year distances and 10 6 yr time intervals for interstellar radiation fronts.…”