摘要:

An approximate solution to the problem of an intense point‐source explosion at the interface separating two different fluids is described; in particular, it is applied to a nuclear explosion initiated on the surface of the ocean. Of special interest is the position of the deformed ocean surface as a function of time during the initial phase of the explosion. The equations of motion for an inviscid fluid with no heat conductivity are written in terms of the verticle angle and a similarity variable. The solution is valid for the early phase of the explosion, during which the counterpressure remains insignificant. It is found that the influence of the free surface on the vacuum interface propagated in the water is confined to a 45° sector adjacent to the original free surface. Below this, the vacuum surface retains very nearly its spherical form. This picture of the flow‐field form is seen to be in good qualitative agreement with the type of flow fields calculated by Brode and Bjork for a megaton burst on the surface of the earth.

ISSN:0031-9171    

DOI:10.1063/1.1691988

出版商:AIP    

年代:1968

数据来源: AIP

摘要:

The effect of an explosion due to the rupture of a pressurized sphere, centered at the ocean surface, is determined. The field of disturbance near the vertical axis through the center of the explosion is determined by Friedman's analytic approach, based on a perturbation of the linear‐shock‐tube solution. The interaction of the main blast wave with the ocean surface is determined by fitting a locally plane shock with a Prandtl‐Meyer expansion, which reduces the shock pressure to atmospheric value. The main object of the calculation is to determine the shape of the distorted ocean surface (or crater). Calculations are made for initial sphere pressures of 619 and 7000 atm, respectively. The shape of the disturbed ocean surface flattens at the base as the strength of the explosion increases, in agreement with the behavior found for intense point source explosions.

ISSN:0031-9171    

DOI:10.1063/1.1691989

出版商:AIP    

年代:1968

数据来源: AIP

摘要:

Betchov and Criminale found certain singularities in the eigenvalue relations for the combined stability problem in space and time. It is shown why these singularities must occur, and how they influence the perturbation generated by a pulse.

ISSN:0031-9171    

DOI:10.1063/1.1691990

出版商:AIP    

年代:1968

数据来源: AIP

摘要:

Experiments are described which show that the waveform at onset of instability in rotating Couette flow may be asymmetric about the rotational axis. Thus, the prediction of Krueger, Gross, and DiPrima is verified. The waveforms have been observed using various cylinders with gap ratios ranging from 0.20 to 0.96. The data covers the complete range where simple asymmetric modes occur. A complicated transient motion is described which leads to the spiral waveforms observed at onset. All predictions of Kruegeret al. are in accord with experiment and previous experimental work can be reconciled with both the theory and the present observations. A waveform which is subharmonic in the axial direction is also studied.

ISSN:0031-9171    

DOI:10.1063/1.1691991

出版商:AIP    

年代:1968

数据来源: AIP

摘要:

Shock waves propagating through sec‐butyl alcohol and carbon tetrachloride vapor produce condensation of the vapor molecules on the shock‐tube walls in the form of a thin liquid film. Electrostatic voltage changes in the potential of narrow metal foils wrapped around the outside of a glass shock‐tube section are associated with the passage of the shock wave through the vapor. The electrostatic signals have been attributed to the shear at, or in the liquid film, due to the presence of the laminar vapor boundary layer established by the shock. The observed signals are consistent with a cylindrical sheet of positive charge which originates at the shock and extends behind the shock for a length equal to that of the laminar boundary layer.

ISSN:0031-9171    

DOI:10.1063/1.1691992

出版商:AIP    

年代:1968

数据来源: AIP

摘要:

A one‐dimensional, inviscid, multifluid model is employed to describe a constant velocity, steady‐profile, ionizing electron‐fluid‐dynamical wave propagating into a pure atomic gas subjected to an applied electric field E0. It is demonstrated that the electron‐fluid equations can be decoupled from the remaining equations allowing description of the wave in terms of electron variables only. Wave speed and resultant degree of ionization are derived as functions of applied field and initial gas pressure. Certain limiting conditions governing the existence of such steady‐profile waves and comparison with the experimental work on breakdown waves are also presented.

ISSN:0031-9171    

DOI:10.1063/1.1691993

出版商:AIP    

年代:1968

数据来源: AIP

摘要:

Fan's treatment [Phys. Fluids 10, 1756 (1967)] of the plane flow of a moderately good conductor is here extended to the more realistic axially symmetric case, for two reasons: to substantiate the algebraic decay of the transient motion; and to clear up an apparent contradiction which would have invalidated the perturbation analysis used in both. The magnetic field diffuses in from a solenoid wound round the circular tunnel in which potential flow past the slender body has been set up. The ultimate flow is found to be essentially Lary's steady motion when the tunnel is very wide, thus substantiating the practical relevance of his work.

ISSN:0031-9171    

DOI:10.1063/1.1691994

出版商:AIP    

年代:1968

数据来源: AIP

摘要:

The onset of the instability of an incompressible, viscous and electrically conducting fluid heated from below and confined within a vertical, rectangular channel is investigated when a uniform magnetic field is applied normally to one side of the channel. The condition for the stability revealed by the critical Rayleigh number is found to be dependent upon both the Hartman number which is a measure of the magnetic effect and the aspect ratio of the channel.

ISSN:0031-9171    

DOI:10.1063/1.1691995

出版商:AIP    

年代:1968

数据来源: AIP

摘要:

The expansion of the Boltzmann collision term up to second order in small deflections is shown to agree with the corresponding expansion of the Smoluchowski equation for arbitrary potentials. A general relation is obtained for the nth Fokker‐Planck coefficient and (velocity) derivatives of higher coefficients.

ISSN:0031-9171    

DOI:10.1063/1.1691996

出版商:AIP    

年代:1968

数据来源: AIP

摘要:

A Lagrangian computer model consisting of 1000 electron rods has been used to investigate the long‐wave diocotron instability in a low‐density(&ohgr;p2≪ &ohgr;c2), re‐entrant, crossed‐field electron beam. A thick and thin beam were found to be stable and unstable, respectively, as predicted by theory. Excellent agreement was obtained between the theoretical growth rate and that observed in the model. The computer model was able to follow the nonlinear behavior of the system. The unstable beam broke up into a vortex street which remained for a long time. The size of the vortex was not enough to transport electrons to the wall of the system and the beam remained confined to the interior.

ISSN:0031-9171    

DOI:10.1063/1.1691997

出版商:AIP    

年代:1968

数据来源: AIP