摘要:

A detailed comparison between experimental data and the predictions of ohmic heating theory is made over a wide range of axial magnetic confining field, electric heating field, and helium pressure. It is found that, in the early stages of the discharge, agreement between theory and experiment is good, and the predicted scaling laws are valid. However, experimentally it is found that it takes about 5 times longer to complete first ionization than predicted. Also, the current is seen to level off at a plateau at a time when theory predicts a continuous heating. These discrepancies are attributed to three energy sinks: cold neutral particles entering the discharge, runaway electrons leaving the discharge, and radiation from impurities. In addition, the electron density is observed to decrease during the length of the discharge (pump‐out). For the early current plateau observed at low ratios of heating field to pressure, it appears that the plasma density is about 15% less at 18 000 gauss than at 27 000 gauss as a result of this pump‐out. The hydromagnetic instability predicted by Kruskal and previously demonstrated to exist is given the physical characteristics of an increased rate of diffusion.

ISSN:0031-9171    

DOI:10.1063/1.1724392

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

The effect of a transverse magnetic field on the motion of a perfectly conducting fluid in a shock tube is examined. A generalized form of the Riemann invariant for the continuous motion of such a fluid is combined with the conservation equations for a magnetohydrodynamic shock to obtain an exact description of the fluid motion in a shock tube in terms of arbitrary initial conditions. The fluids are assumed to have constant specific heat ratios.Qualitatively, the effect of the magnetic field is equivalent to that of a pressure, but quantitatively the effect is always greater than merely the hydrodynamic pressure equivalent of the appropriate Maxwell stress. A magnetic field in the high‐pressure region alone can produce shocks having Mach numbers for typical laboratory conditions, of the order of hundreds, and in general is in agreement with available experimental results. A magnetic field in the low‐pressure region results in weaker, but higher velocity shocks.

ISSN:0031-9171    

DOI:10.1063/1.1724394

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

A stationary flame is stabilized in a two‐dimensional channel in such a way that it closely corresponds to the case of a flame propagating in a channel. The entire flow field of unburned and burned gases is mapped by taking stroboscopic photographs of small particles suspended in the combustible gases. The asymptotic flow field of the burned gases is analyzed in terms of flow conditions at the flame. The possibility of obtaining an analytic flow field on the basis of constant flame speed is examined. It appears that no solution exists unless the channel walls in the region of burned gases are displaced inward. This investigation, together with the previous work on the flow field of a Bunsen flame, leads to some general remarks about the structure and stability of laminar flames. The various predictions are in agreement with experiments. In particular, the convex flames are possible and concave ones impossible within the framework of the theory based on constant flame speed.

ISSN:0031-9171    

DOI:10.1063/1.1724395

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

Improved numerical results are obtained for the spectrum of turbulence based on Heisenberg's elementary theory during the stage of decay in a nonstationary process, which is discussed in Chandrasekhar's 1949 paper. The choice of the form of the differential equation is examined from the viewpoint of its sensitivity in numerical computations to variations of the basic parameter.

ISSN:0031-9171    

DOI:10.1063/1.1724396

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

Nonstationary temperature distributions and evaporation (or condensation) rates are calculated for the case in which the condensed phase is initially at uniform temperature, the latent heat is supplied (or absorbed) by the condensed phase, and the vapor is in the saturated state.

ISSN:0031-9171    

DOI:10.1063/1.1724397

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

The pressure dependence of the self‐diffusion coefficients of several normal paraffin hydrocarbons and the isomers of hexane have been determined. In addition, the temperature dependence of self‐diffusion coefficients has been measured for the isomers of hexane. Energies and volumes of activation have been calculated. With the exception of 2, 2‐dimethyl butane, these parameters do not change significantly with branching in the isomers of hexane. The volumes of activation are about 10–20% of the molar volumes in all cases. Diffusion coefficients computed from a semiempirical modification of an equation derived by Longuet‐Higgins and Pople are compared with the experimental results.

ISSN:0031-9171    

DOI:10.1063/1.1724398

出版商:AIP    

年代:1959

数据来源: AIP

ISSN:0031-9171    

DOI:10.1063/1.1724400

出版商:AIP    

年代:1959

数据来源: AIP

ISSN:0031-9171    

DOI:10.1063/1.1724401

出版商:AIP    

年代:1959

数据来源: AIP

ISSN:0031-9171    

DOI:10.1063/1.1724402

出版商:AIP    

年代:1959

数据来源: AIP