摘要:

The theory of the ideal shock tube was first given by Hubert Schardin in 1932 and some of the earliest studies of shock tube performance were then made. These early studies are recalled as well as more recent studies initiated by Schardin on the topic of shock tubes. His other contributions to the physics of rapidly occurring events are also described.

ISSN:0031-9171    

DOI:10.1063/1.1692623

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

Fastshock waves inlightgases can be produced simply by electromagnetic acceleration. Unlike rail spark gaps or magnetic annular tubes, which produce quasistationary, shock‐wavelike phenomena, T tubes and conical theta pinches or Z pinches generatenonstationaryshock waves of the blast wave type if the plasma of the driving discharge does not advance right into the shock front and appreciably influence the plasma formed there. The investigations of free‐running shock waves and the distributions of the parameters in the plasmas behind these shock fronts are discussed. Shadowgraphs, interferograms, microwave interferograms and probe measurements have afforded a fairly complete picture of such nonstationary waves revealing their uses and limitations.

ISSN:0031-9171    

DOI:10.1063/1.1692587

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The application of the shock tube to transition probability measurements is discussed, with particular attention to determination of the thermodynamic state of the radiating gas. Specific examples from earlier work on the spectrum of neutral chromium and from current measurements for light atoms clarify the need for redundant temperature determinations and illustrate the value of a new technique of data analysis which circumvents the sensitive dependence of level populations on temperature.

ISSN:0031-9171    

DOI:10.1063/1.1692622

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

An assessment of the shock tube as an instrument for research in radiation gas dynamics is presented. Principal results obtained since Kantrowitz and Laporte first observed luminous fronts are described and the roles of impurity and nonequilibrium radiation, spectral intensities, rate processes, and continuum radiation are discussed. Spectroscopy was originally used as an aid to understanding problems in gas dynamics at moderate temperatures. More recently the shock tube has been used as a tool for spectroscopic research. The present trend is toward a fusion of these two interests in studying radiation‐coupled flows where radiant energy transport affects the flow field. Present day shock tubes with arc‐heated drivers attain thermodynamic conditions typical of superorbital speeds—the regime where radiant energy transfer becomes important. The current interest is in determining the radiative properties of gases at these high temperatures (10 000‐20 000°K). Here the presence of significant amounts of vacuum ultraviolet radiation causes instrumentation problems which hamper investigations at present. However, solutions have been devised. Shock‐tube results are compared to current theoretical predictions for the spectrally integrated total radiant intensity of high‐temperature air. These reveal differences on the order of a factor of 2 and also clarify certain important areas of future endeavor. These include thermodynamic state measurements of gases shocked to temperatures above 10 000°K, additional measurements of the total intensity, and measurements of the spectral radiant intensity of high‐temperature gases. An extensive bibliography is included.

ISSN:0031-9171    

DOI:10.1063/1.1692624

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

During the last decade the study of the interaction between normal shocks and boundary layers in the shock tube has been carried out by many research workers. This interest has been fostered by the requirement to understand the effects that this phenomenon may have on the flow properties in the region between the reflected shock and the end of the tube. This so‐called reflected shock region is important in chemical kinetics studies and as a reservoir of gas for hypersonic shock tunnels. In this paper a review is given of the various analyses of the problem together with the results of experimental studies. Reflected and transmitted shock bifurcation, the rate of growth of the bifurcated foot, and the effects of transition to turbulence are discussed. The influence of bifurcation on the flow in the shock tube is assessed, especially as a mechanism for transporting cold driver gas to the end plate, causing early cooling of the gas on the reflected shock region.

ISSN:0031-9171    

DOI:10.1063/1.1692625

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The widths of van der Waals broadened Si I spectral lines were measured by using a conventional shock tube and a scanning Fabry‐Perot interferometer. The experiments have been performed by using argon as the perturbing gas in the reflected region of the shock wave at a temperature of about 5500°K and over a pressure range of 2‐10 atm. The temperature was determined by a line reversal technique; the pressure was measured using a quartz transducer. The scanning Fabry‐Perot was driven by a piezoelectric crystal operating at its resonant frequency (10.5 kc/sec); the line profiles were detected photoelectrically and displayed on an oscilloscope for photographing and analyzing. A set of calculated curves was used to obtain the contribution of the pressure broadening to the widths of the spectral lines. The experimental widths thus determined are within a factor of two of the results obtained from theory.

ISSN:0031-9171    

DOI:10.1063/1.1692626

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

Strong shocks at Mach numbers from 10 to 15 and at initial pressures between 1 and 10 Torr are produced in a conventional diaphragm shock tube. The effect of radiative energy loss from the plasma behind the shock is studied by quantitative measurement of the decay of continuous emission at&lgr; = 4000 A˚. It is shown that for high electron densities the maximum emissivity deviates remarkably from Unso¨ld's theory. The variation of flow parameters with increasing distance from the shock front is calculated using an iterative method developed by Pomerantz. The results indicate that the observed luminosity decay cannot be explained by losses of continuous radiation alone. The influence of resonance radiation and line emission on the plasma cooling rate is briefly discussed.

ISSN:0031-9171    

DOI:10.1063/1.1692627

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

Ion density profiles for low Mach numbers (7‐9) have been obtained in a pressure‐driven shock tube. In this Mach number range the ionization process is strongly influenced by small amounts of impurities. Various techniques for minimizing the impurity level due to outgassing from the shock tube walls and back diffusion of pump oil are discussed. Preliminary results for argon are described. For air new results for the ionization relaxation time are obtained.

ISSN:0031-9171    

DOI:10.1063/1.1692628

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

Details are presented of an experimental determination of the Gladstone‐Dale constants for dissociating high‐temperature oxygen. The hot dissociating gas was obtained by shock heating (M = 8.8‐16.6, p1 = 4‐54Torr), and the index of refraction of the hot gas relative to room temperature gas was determined by photographing the shock wave with an interferometer. The change in density across the shock was obtained from normal shock calculations and, thus, the Gladstone‐Dale constants could be determined. The results were:1.93 cm3/g ± 1%for the oxygen molecule, and2.04 cm3/g ± 2%for the oxygen atom, which were in agreement with the results obtained by Alpher and White. Details are presented of the high‐speed photographic techniques employed, of the method used to reduce the data, and of the problems encountered during the investigation.

ISSN:0031-9171    

DOI:10.1063/1.1692629

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The construction and operation of a heated shock tube (often called mercury shock tube due to its immediate application) are described in some detail. Experimental observations of strong shocks in mercury gas are presented and discussed in the light of preliminary theoretical investigation. An observation of reflected shock bifurcation in the monatomic gas of mercury is also reported.

ISSN:0031-9171    

DOI:10.1063/1.1692630

出版商:AIP    

年代:1969

数据来源: AIP