摘要:

The differences among the various scalings in the transport calculations associated with the collisionless detrapping/retrapping orbits in a nonaxisymmetric torus are clarified. A simple random walk argument indicates that these differences are mainly due to an implicit assumption made about the retrapping rate of the toroidally trapped particles.

ISSN:0031-9171    

DOI:10.1063/1.864512

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A symmetric version of the regularized‐long‐wave equation is shown to describe weakly nonlinear ion acoustic and space‐charge waves. The equation possesses hyperbolic secant squared solitary waves and has four known invariants. Numerical solutions are compared with previous results on the regularized‐long‐wave equation.

ISSN:0031-9171    

DOI:10.1063/1.864487

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A new plasma‐dynamo mechanism is proposed, with application to the outer region of the reversed‐field pinch. The mechanism uses space‐charge electric fields associated with particle transport to drive steady‐state electrical currents which otherwise would resistively decay for lack of an externally applied electric field. The mechanism is suggested by recent observations during sustained discharges in the ZT‐40M experiment.

ISSN:0031-9171    

DOI:10.1063/1.864491

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

High‐beta tokamak equilibria in Torus II are studied both experimentally and computationally. Electron temperature and density profile measurements from the multipoint Thomson scattering system and line‐integrated density from a CO2interferometer show that an equilibrium is obtained with a volume averaged beta of 10%. The peak electron temperature is 80 eV and the density is 1×1015cm−3. A numerical computation of these equilibria is carried out using a 2‐D, free‐boundary, magnetohydrodynamic equilibrium code which is in good agreement with the experimental results.

ISSN:0031-9171    

DOI:10.1063/1.864497

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

The first spheromaks with Thomson‐scattering‐measured electron temperatures of over 100 eV are described. The spheromak is generated by a magnetized coaxial plasma source in a background gas of 30 mTorr of H2, and it is stably confined in an oblate 80 cm diam copper mesh flux conserver. The open mesh design allows rapid impurity transport out of the spheromak. The peak temperature, measured using multipoint Thomson scattering, is observed to rise from approximately 25 eV to over 100 eV in about 0.2 msec due to Ohmic heating from the decaying magnetic fields. Density (∼5×1013cm−3) and magnetic fields (approximately 2 kG) are measured using interferometry and magnetic probes.

ISSN:0031-9171    

DOI:10.1063/1.864495

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

One minimum‐Bmirror end cell of the Phaedrus tandem mirror was heated with up to 30 kW of electron cyclotron heating at &ohgr;=2&ohgr;ce. The plug electron temperature was increased from 18 to 23 eV while a smaller temperature increase was measured in the central cell. Changes in ion end loss energy and current were consistent with direct measurements of increases in the east plug plasma potential. Ion confining potential increases of up to 27 V were observed. These increases were much greater than theTe/eincreases and in excess of that predicted by the Boltzmann relation.

ISSN:0031-9171    

DOI:10.1063/1.864505

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

The deformation of an initially spherical liquid drop moving under the action of gravity in another fluid with which it is completely miscible is investigated under conditions of small values of the drop Reynolds number. It is found experimentally that such a drop evolves into an open torus which subsequently expands, and this phenomenon is examined theoretically for two limiting drop geometries: (i) a slightly deformed spherical drop, and (ii) a highly expanded, slender open torus. Under the assumptions of zero interfacial tension and creeping flow, the theory provides a qualitative description for the initial stages of the drop evolution [case (i)], but is unable to account for the observed drop expansion during latter stages of deformation [case (ii)]. On the other hand, if small inertial effects are retained in the analysis, the theory predicts that a slender open fluid torus possessing an arbitrary cross‐sectional geometry will expand without change of shape to first order in Reynolds number. Quantitative comparisons of theoretically predicted rates of expansion with experimental measurements suggest the possible existence of a small, time‐dependent interfacial tension across the drop interface.

ISSN:0031-9171    

DOI:10.1063/1.864511

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A theoretical investigation into (i) the motion of a spherical particle in a gas flow with a simple shear and (ii) the motion of a spherical particle in a gas flow over a wavy wall is described. The lift force on the particle due to the rate of shear of the gas is taken into consideration. Analytical solutions for the particle motion are obtained in both cases under the conditions that the gas properties are not affected by the presence of particles and also the gas is inviscid except for its interaction with solid particles. Sample calculations are carried out for a few typical conditions.

ISSN:0031-9171    

DOI:10.1063/1.864484

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A recent experiment by Banerjee and Korpel [Phys. Fluids25, 1938 (1982)] indicates that McGoldrick’s [J. Fluid Mech.21, 305 (1965)] theory of resonant interactions among deep water capillary‐gravity waves may require modification. The conclusions are reexamined, and it is found that the experimental results are in overall agreement with the theory. Some systematic differences remain at low and high frequencies. Possible reasons for these discrepancies are proposed.

ISSN:0031-9171    

DOI:10.1063/1.864485

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A previous numerical study by Davis and Moore of vortex shedding from rectangles in infinite domains is extended to include the effects of confining walls. The major changes to the numerical modeling are the addition of a direct solver for the pressure equation and the use of an infinite‐to‐finite mapping downstream of the rectangle. The parameters in the problem are now Reynolds number, rectangle aspect ratio, blockage ratio, and upstream velocity profile. As each of these is varied, the effects upon the forces acting on the rectangle and the structure of the wake are discussed. Streakline plots composed of multishaped passive marker particles provide a clear visualization of the vortices. These plots are compared with smoke‐wire photographs taken from a wind tunnel test. Strouhal numbers obtained both computationally and experimentally are compared for two values of the blockage ratio. Moving recirculation zones which appear between the wake and the walls are discussed.

ISSN:0031-9171    

DOI:10.1063/1.864486

出版商:AIP    

年代:1984

数据来源: AIP