Thesis--Wisconsin. / Vita. Includes bibliographical references (leaves 153-156).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1965. / Abstracted in Dissertation abstracts, v. 25 (1965) no. 10, p. 6000-01. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1968. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliography.

Graduate

No description available.

The flow conditions in a low attenuation electromagnetic shock tube are discussed and compared with those in pressure driven shock tubes and conventional electromagnetic shock tubes. The low attenuation electromagnetic shock tube differs from the conventional electromagnetic shock tube in that it incorporates a diaphragm separating the high pressure driver section from the low pressure expansion section. It was shown that the shock tube gives a plane shock front and a region of shock heated gas separated from the driver gas by a non-plane contact surface. The electrical conductivity of shock heated argon was measured for shock speeds of from Mach 8 to Mach 35, and downstream pressures of from 0.01 to 2.0 mm Hg, and was found to agree with theory at the higher downstream pressures but to fall below the theoretical values at the low pressures. The low values of conductivity were attributed to a non-attainment of equilibrium behind the shock front due to the greater relative importance of electron diffusion at low densities. The shock heated gas was used as the working fluid in two magnetohydrodynamic power generators. In the first the internal resistance of the generator was measured as a function of electrode area and generator current. It was concluded that at high currents a cathode spot was formed, and the measured resistances were related to a theory of cathode spot conduction. In the second generator some effects of the non-scalar conductivity of the plasma at high magnetic fields were investigated. It was shown that the values of Hall voltages in a magnetohydrodynamic generator agree with theory, and can be used to obtain an estimate of the electron density in the plasma. The reduction of the generator current by Hall currents was measured. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

This thesis is concerned with a theoretical and experimental investigation of Alfvén waves in an ionized medium, and magnetic interaction effects between a moving plasma and a magnetic coil external to the plasma. Methods for generating Alfvén disturbances for varying conditions of gas density and magnetic fields are considered and various means for measuring any effects that may be produced. It will be seen that for propagation of m.h.d. waves, extremely strong coupling between the plasma and field is necessary with consequent necessary high fields and Alfvén speeds. The effect of an axial magnetic field modifying the shock speed in the plasma is investigated and also the effect of the field on incident and reflected shock speeds by placing a plain obstruction in the shock tube which blocks the plasma flow. A further study of magnetic interaction effects between a moving plasma and a localized radial field was undertaken with the desire of correlating mechanical momentum transfer with varying conditions of applied field and gas pressures in the plasma (hence conductivity, density, and shock speed variations). Mechanical and electrical measurements of momentum transfer are compared with theory, and it will be seen that the mechanical method offers a fairly reliable means of measurement. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The propagation of a shock wave into a general inhomo-geneous flow field is studied. The equations for the shock velocity through such a region are developed in a general manner. A consequence of these equations is the development of the shock wave as a probe into unknown flow fields. The shock velocity is measured and the initial parameters ahead of the shock are calculated. The unique advantage of the shock probe is that it does not perturb the gas ahead of the front. An experimental application is described in which the shock probe is used to analyze the unknown flow field created by a constricted arc light source. The flow field is subsequently identified as a radiation front at the Chapman-Jouguet point. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The formation and propagation of laser-driven shock waves has been observed by optical shadowgraphy in fused quartz, α-quartz and sodium chloride. Target materials were irradiated with a 0.53 µm , ~ 2.5 ns FWHM laser pulse at intensities ranging between 0.2 — 2 x 10¹³ W/cm², producing peak pressures varying from 0.3 — 3 Mbar at the shock front. Observations in both varieties of quartz reveal transient, high-speed shock propagation followed by deceleration towards a steady asymptotic shock speed. Similar high-speed transients were not seen in sodium chloride. The results in quartz were found to be in significant disagreement with both one-dimensional and two-dimensional hydrodynamic calculations based on equilibrium equations of state. The non-steady shock propagation is interpreted as being due to a relaxation process in the phase transformation of quartz into the high-pressure stishovite phase which occurs at the shock front. The effects of such a relaxation process on the shock dynamics and shock compression process are considered for the case of a direct relaxation from quartz into stishovite, as well as for an indirect relaxation process in which the -transformation of quartz into stishovite is preceded by shock-induced amorphization of the quartz. It is shown that either scenario would result in higher shock speeds and less compressible shock states than those obtained under equilibrium conditions. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Standing shock waves in a supersonic flow field produce density gradients across which an electrical potential is established. If electrodes are mounted upstream and downstream of the standing shock, an electrical current can be extracted. The electrical power output by such a system (called a bow shock generator) has been measured. To produce the supersonic flow an overdriven detonation shock tube, capable of producing Mach 12 shocks in 5 Torr argon, was constructed and used as a short duration supersonic wind tunnel. The open circuit voltage of a single bow shock generator with a 2 cm electrode separation was measured to be 0.95 V, and the maximum power output to 53 mW. By reducing the electrode separation to 1 cm the maximum power output was increased to 90 mW, while the open circuit voltage remained unchanged. It was found that when two bow shock generators are mounted side by side in the flow a parallel connection of their outputs produced a small increase in current. However no increase in output voltage was observed when the generators were connected in series. It was also found that when an oblique shock and its reflection from the wall were connected together in series, the output voltage was less than that of the oblique shock alone. However this was likely due to a short circuit path between the electrodes through the boundary layer. Some of the measurements were inconclusive due to an insufficiently long test time. A preliminary analysis was done on a system in which a set of bow shock generators is used as a topping system for a conventional electrical generation system. It was shown that the bow shock generators must be operated at very low Mach numbers if they are to be efficient in this application. / Science, Faculty of / Physics and Astronomy, Department of / Graduate