摘要:

The particle density of a simple model of the exosphere is obtained by solvingexactlythe collisionless Boltzmann equation. The main point of the solution is that it is a discontinuous, multivalued function of the constants of motion. Results, of course, agree with those of other methods based on Newtonian mechanics.

ISSN:0031-9171    

DOI:10.1063/1.1724466

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

The rate of dissociation behind strong shock waves in N2and O2is calculated using a revised model for the coupling of vibration and dissociation. In previous calculations a model which coupled the rate of dissociation to the degree of vibrational excitation was used. The present model adds to the coupled vibration‐dissociation model the fact that the rate of vibrational excitation is in part determined by the rate of dissociation. Since the average energy of molecules which are dissociated is greater than the average energy of the remaining molecules, this coupling results in a drain on the average vibrational energy. It is shown that this coupling reduces the strong overshoot in vibrational energy that was previously obtained, and decreases the rate of dissociation behind strong shocks.

ISSN:0031-9171    

DOI:10.1063/1.1724467

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

Exact similar and nonsimilar solutions for axisymmetric wakes with small swirl in a constant‐property medium are derived. Emphasis is placed on the similar solutions, particularly those associated with the swirl. A unique similar solution for the axial velocity is distinguished from a possible infinite set by invoking the auxiliary condition of invariance of the axial momentum defect. Likewise, for the circumferential velocity only one of the large number of possible similar solutions is shown to satisfy the conditions that the circumferential mass flow, momentum flux, and higher moments are bounded.

ISSN:0031-9171    

DOI:10.1063/1.1724468

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

A variational method valid for the creeping‐flow regime is used to calculate an upper bound for the pressure drop associated with viscous dissipation near the ends of a long round tube. The result states that this pressure drop, which is an additive correction to that given by the Poiseuille formula, is not greater than 1.154 times the pressure drop through a thin orifice. The orifice pressure drop, in terms of the fluid viscosity &mgr;, the volumetric flow rateQ, and the radiusa, is found to be 3&mgr;Q/a3, in confirmation of a previous calculation of Roscoe by a different method.

ISSN:0031-9171    

DOI:10.1063/1.1724469

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

A nonlinear formulation of electrohydrodynamic and magnetohydrodynamic surface interactions is developed which, in the absence of magnetic or electric fields, becomes the classical ``long'' gravity‐wave theory. The results are valid for a shallow highly conducting fluid that interacts strongly with a rigid highly conducting plate in such a way as to either conserve an electric potential difference or a magnetic flux. The growth of surface discontinuities from compression and depression waves is discussed, with transition electrohydrodynamic waves originating from timelike data given to illustrate waves that are partly controlled by gravity and partly by the electric field. Waves initiated from spacelike data are also described, and the integral jump conditions derived.

ISSN:0031-9171    

DOI:10.1063/1.1724470

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

The flow behind a shock wave that propagates through a perpendicular magnetic field along a flat plate of high conductivity is analyzed under the assumption of small magnetic Prandtl number. Under such circumstances the regime of influence of magnetic diffusion is much thicker than the viscous boundary layer and the flow can be treated as essentially inviscid. On this basis it is shown that the problem becomes analogous to the Rayleigh problem, insofar as the velocity distribution along the wall is concerned, provided that the velocity of flow behind the shock wave is exactly equal to the Alfve´n velocity.

ISSN:0031-9171    

DOI:10.1063/1.1724471

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

A clear experimental observation of Rayleigh‐Taylor, flute‐type instability in a high‐temperature plasma expanding across a magnetic field has been made with time‐delay, Kerr cell, sequence photography. The wavelength and growth rate of the instability are measured as a function of time for various values of external magnetic field and background gas pressure. With interface decelerations of about 109m/sec2the instability develops in 1–4 &mgr;sec with wavelengths of about 10−2m. After 1–4 &mgr;sec the flutes grow with constant velocity.

ISSN:0031-9171    

DOI:10.1063/1.1724472

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

The instability of a radially accelerated cylindrical shell in a magnetic field has been investigated. It was assumed that the shell was of infinitesimal thickness. For perturbations which do not bend the lines of the magnetic field, the growth rate was found to bew= (gk)½, wheregis the acceleration of the shell andkis the wavenumber. This growth rate is independent of the shell thickness. Perturbations which do bend the lines of the field were also found to be unstable. From a supplementary calculation, it was concluded that these instabilities were effective only for wavelengths greater than 8&pgr;awhere 2ais the shell thickness.

ISSN:0031-9171    

DOI:10.1063/1.1724473

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

A formalism for representing helically invariant hydromagnetic systems is introduced. Such systems are the most general two‐dimensional configurations in three‐dimensional space, since they include translation‐invariant and rotation‐invariant configurations as special cases. Expressions for the magnetic field and, when the system is in equilibrium, the current are given in terms of an appropriate nonorthogonal coordinate system. An energy integral is given which forms the basis of a numerical relaxation procedure for obtaining equilibria. The relationship between this formalism and that in which the equilibrium problem is reduced to solving a partial differential equation for the stream function is established. The necessary and sufficient condition for the stability of helically invariant systems with respect to localized displacements is obtained.

ISSN:0031-9171    

DOI:10.1063/1.1724474

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

A plasma containment device has been constructed in which an attempt has been made to combine the basic stability advantages of a four‐pole line cusp with the low loss rate of a mirror field. The magnetic field was produced by the addition of the mirror field orthogonally to the cusp field. Using pulse techniques an ionized gas was created within a biconical chamber and a magnetic field produced transiently with the mirror field along the axis of the chamber (Zaxis) and the cusp field in theX‐Yplane. Measurements with magnetic probes and light pipes show that a disturbance in the magnetic field accompanied by an increase in light intensity started at the periphery of the plasma chamber and was propagated inward at two velocities to the central axis. Detailed measurements made on the magnetic‐field configuration indicate that, at the time of arrival of the second wave at the axis, the mirror field had been to a large extent separated from the cusp field so that mostly mirror field existed throughout the central region, while mostly cusp field existed in the outer region. The intensity of the field at this time in the central region indicates that the cusp field was compressing the plasma and mirror field so that the intensities of the mirror field in this region were even larger than the maximum intensity of the applied mirror field.

ISSN:0031-9171    

DOI:10.1063/1.1724475

出版商:AIP    

年代:1962

数据来源: AIP