The production of pulsed nozzle flows in a shock tube

Abstract

Firstly, I would like to thank my supervisor, Dr. R. J. Stalker, for the invaluable help and guidance which he has given me during the time that we have worked together. I am also indebted to him for the design of the hardware for the modification to the shock tunnel and for the original concept for the modification. I would also like to thank Dr. Hans Hornung and Dr. John Sandeman for their generous assistance, given on innumerable occasions. There are many other people to whom I am indebted: to Mr. Roland French, Mr. Vic Adams and Mr. Gavin Spackman for their help in performing the experiments, maintaining the equipment and running the tunnel and shock tube safely and efficiently; to Mr. Ken Smith for his photographic work and the helpful advice he has given in this field; to Mr. Len Batt and Mr. David King for repair and mainten ance of the electronic equipment; to the workshop staff of the Physics Department for the production of several pieces of apparatus all of which have been of high quality. My thanks go also to my fellow post-graduate students, notably Doug Kewley, Nizar Ebrahim, Graham Caldersmith, John Baird and Mike Daffey, for the many stimulating and helpful discussions we have had. I extend my thanks to Ms. Julie Faux, not only for typing this thesis, but for going, with me, through all the traumas of its compilation. Finally, I wish to express my appreciation to the Australian Government for their provision of a Commonwealth Scholarship and to the Australian Research Grants Committee for the funding of the research.

Unsteady shock propagation in a steady flow nozzle expansion

“…In order to explain the observed features of the flow, to identify other features, and to explore the mechanisms by which they arise, a series of perfect gas calculations was performed using the unsteady one-dimensional method of characteristics (Mudford 1976). Following Rudinger (1955) the calculations were conducted with the speed of sound, the specific entropy, and the flow speed as dependent variables.…”

“…For strong shock waves, the required density distribution in the resident gas can be approximated by providing a st.eady flow through the nozzle prior to arrival of the shock wave, and t,his situation is studied in this paper. As indicated in a previous paper (Mudford & Stalker 1976) the reduction in the duration of the transient effects is sufficient to allow this prior steady flow method t o be as effective as more conventional methods in ensuring rapid establishment of steady flow in an expansion nozzle in a shock tube, but with an important advantage. Conventional methods minimize the impedance of the gas initially resident in the nozzle by pre-evacuating the nozzle volume, providing a diaphragm between the shock tube and the nozzle in order to ensure that the initial shock tube density remains a t the correct value.…”

Modern developments in hypersonic wind tunnels

“…Figure 15(c) displays a time resolved spectrum of the radiation from the shock layer in the stagnation region of a hemisphere at an inertia of any practical diaphragm is too large for it to be removed from the test flow in the few tens of microseconds of test time available in a high performance shock tube. The diaphragm can be rendered unnecessary by arranging that, immediately prior to a test, a steady flow of test gas is established in the nozzle (56,57) . This allows the nozzle starting process to be completed as rapidly as with a pre-evacuated nozzle and a massless diaphragm.…”