摘要:

Lees’ method, combined with a generalized Grad’s moment procedure, is used to calculate the heat and mass transport to and from a droplet in a polyatomic gas. A near‐equilibrium and quasisteady situation is assumed. The results are represented by the transport coefficients of a symmetric Onsager matrix. The coefficients depend on the collision numbers of the internal degrees of freedom. Simple results are obtained by performing approximations analogous to the Mason and Monchick analysis for the case of the heat conductivity.

ISSN:0031-9171    

DOI:10.1063/1.864416

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

The separation of binary gas mixtures of carbon dioxide and hydrogen in sonic‐orifice‐generated free jets is investigated over a source Reynolds number range of 100 to 3000 using the well‐known electron beam fluorescence technique. The lighter species, hydrogen, is chosen as the minor species in order to examine the extent of the validity of Sherman’s first‐order diffusive separation theory for large separation. The diffusive separation of mixtures containing approximately 2%, 5%, and 20% hydrogen in carbon dioxide is investigated by experimentally determining the relative number densities of the two species as a function of centerline axial distance within the free jets. Sherman’s diffusive separation theory is applied to the jets using axial Mach number profiles which were a combination of experimental and analytical results for &ggr;=1.40 expansions. The &ggr;=1.40 expansion is shown to approximate the CO2–H2expansion quite well, and the calculated separation agrees remarkably well with the experimentally determined values.

ISSN:0031-9171    

DOI:10.1063/1.864392

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

The process of the spherical nonequilibrium expansion of a homogeneous metal liquid‐vapor cloud into a vacuum is considered for high initial entropies (up to 0.9Scrit) and high expansion velocities (several km/sec). Starting from phase equilibrium, the system successively passes through stages of increasing nonequilibrium, determined by the characteristic times of the expansion as well as heat and mass transfer and ends up in a state of maximum nonequilibrium, where there is no more contact between the phases. Results are discussed for different metallic fluids.

ISSN:0031-9171    

DOI:10.1063/1.864393

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Collisions are discussed for a pure electron plasma which is so strongly magnetized that the Larmor radius is small compared to the classical distance of closest approach. In this regime, the most important collisions are characterized by an impact parameter which is the order of the distance of closest approach. Assuming that this distance is small compared to the interparticle spacing, a Boltzmann‐like collision operator may be derived. In turn, this operator may be reduced to a Fokker–Planck operator, which is integrable. An interesting property of the collision operator results from an adiabatic invariant which is preserved during scattering. There is no energy exchange between the velocity components which are parallel to the field and the velocity components which are perpendicular to the field. This may have implications for a current effort to cool a pure electron plasma to low temperature by cyclotron radiation.

ISSN:0031-9171    

DOI:10.1063/1.864394

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

For a sufficiently high number of toroidal field periods (m/&igr;>l), the magnetic field of a multiple‐helicity torsatron can be reduced to a simple form such that the second adiabatic invariantJcan be calculated. It is found that the particle and the heat fluxes for a multiple‐helicity torsatron in the low‐collisionality (1/&ngr;) regime have the same geometric dependences. An optimization of both quantities is carried out for a given equilibrium constraint. It is shown that the transport fluxes can be smaller than those of the conventional stellarator by an order of magnitude. The effect of finite plasma beta on the neoclassical fluxes is also studied.

ISSN:0031-9171    

DOI:10.1063/1.864395

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

The effect of an equilibrium poloidal electric field on the neoclassical transport coefficients is studied in the banana regime, and a significant enhancement (a factor of 2 or more) is obtained for the physically interesting case where the magnitude of the electrostatic potential inhomogeneity is of the same order as the magnetic field inhomogeneity in a tokamak.

ISSN:0031-9171    

DOI:10.1063/1.864396

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

For resonant ions in the ELMO Bumpy Torus experiment (EBT), the width of the orbits near the resonance scales like (∂&OHgr;/∂r)−1, where &OHgr; is the precessional drift frequency. For (∂&OHgr;/∂r)≊0 over most of the plasma, the ions will drift vertically out of the machine due to the toroidal magnetic field. The problem of these directly lost particles is analyzed by considering collisional diffusion into a hole in velocity space. Particle and energy loss rates including boundary layer corrections due to marginally confined particles are obtained. It is shown that these direct loss rates can be comparable to diffusion rates based on banana transport.

ISSN:0031-9171    

DOI:10.1063/1.864397

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

The collisional fluxes of trapped electrons escaping from the plug, and the center cell electrons passing over the thermal barrier and becoming trapped, are evaluated for a simple thermal barrier model appropriate to present tandem mirror experiments.

ISSN:0031-9171    

DOI:10.1063/1.864398

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Charged particle motion near the null of a two‐dimensional magnetic field is studied. Specifically, the magnetic field is given by the vector potentialA=zˆ&psgr;0[(y/a)2+(&egr;x/a)2], in which &psgr;0,a, and &egr; are constants with &egr; parameterizing the ellipticity of the flux surfaces. Conservation of canonicalzmomentumpzreduces the number of nontrivial degrees of freedom to two. Scaling reduces the number of parameters in the system to two, &egr; and &sgr; (the sign ofpz). Analytical and numerical methods are used to study the nature of orbits. The results are expressed conveniently in terms of &egr; andQ≡(2mE)1/2/pz. When &egr; is unity, the additional symmetry implies integrability. When &egr; is less than unity (the case &egr;>1 is trivially related) three regimes are found: (1) For ‖Q‖≫1 particle orbits are regular, (2) for &egr;3/2≲‖Q‖≲1 most particle orbits are stochastic, and (3) for ‖Q‖≪&egr;3/2particle orbits are regular, with the third invariant being the magnetic moment.

ISSN:0031-9171    

DOI:10.1063/1.864399

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

The oblique propagation of fully nonlinear, slow ion‐acoustic solitary waves in a collisionless, low‐beta, magnetized plasma is examined. The analysis includes the effects of a finite ion pressure, electron trapping, and multicomponent particle populations. The existence of both compressive and rarefactive modes propagating obliquely to the magnetic field in a plasma with two distinct Boltzmann electron populations and cold ions is demonstrated. It is shown that paired electrostatic shocks observed over the Earth’s auroral zone may be closely related to the rarefactive modes. As a measure of the collisionless dissipation encountered by the solitary waves, the linear response of the plasma to slow ion‐acoustic waves is also examined.

ISSN:0031-9171    

DOI:10.1063/1.864400

出版商:AIP    

年代:1983

数据来源: AIP