Ionospheric gas dynamics of satellites and diagnostic probes

The gas dynamics of interactions of a tenuous ionosphere with moving satellites and probes that have bearings on the diagnostics of the ionosphere are discussed. Emphasis is on the cases where the body is moving at mesothermal speeds, namely intermediate between the thermal speeds of ions and electrons of the ambient ionosphere. Methods of collision-free plasma kinetics with self-consistent field are used. The development of the topics for discussion starts with stationary Langmuir probe which entails the basic mechanism of body-plasma interaction that becomes further intricated as the body moves at a higher and higher speed. Applications of the theory of plasma interaction to meteors which move in the ionosphere are also presented.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43801/1/11214_2004_Article_BF00212707.pd

Non-equilibrium effects during the sudden vaporization of saturated water / Vaporization of superheated water under sudden depressurization

The vaporization of an entrapped mass of saturated water suddenly allowed to expand is studied both experimentally and theoretically. In the experimental set-up, the water is initially pressurized by a piston at the closed end of a cylinder and heated to the onset of vaporization, at which time the expansion is initiated by releasing the gas counterpressure acting on the back face of the piston. The initial depressurization rate is mainly controlled by the gas pressure releasing mechanism, which, in the present study, consists of either a fast opening electric valve or a diaphragm breaker. Pressure measurements along the path of the piston indicate a significant pressure undershoot when compared to the numerical finite element predictions based on a one-dimensional, homogeneous equilibrium flow. Pressure undershoots up to 290 kPa for a initial water pressure of 600 kPa have been measured and are caused by non-equilibrium vaporization delays which affect the whole expansion range tested (volume ratio up to 50). For the sake of comparison, reference is being made to the Simpson and Silver non-equilibrium prediction model. The vaporization process is illustrated by a high-speed movie taken through a transparent cylinder. A sharp separation front appears between the steam and water phases as the light high quality steam migrates faster towards the face of the moving piston