摘要:

Anisotropic flakes dispersed in certain liquids are shown to remain suspended for periods of the order of months. Such particles represent an ideal flow visualization technique, especially for thermally driven flows such as Rayleigh–Be´nard convection.

ISSN:0031-9171    

DOI:10.1063/1.864702

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

The mechanics of two co‐rotating, entangled, slender vortex filaments are analyzed. An equation governing the motions of the vortices is derived on the assumption that their curvature is small. Particular solutions are obtained for two flow situations: one with and one without an external strain field.

ISSN:0031-9171    

DOI:10.1063/1.864703

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

The vertical overturns occurring behind a biplane grid placed in a continuously stratified water channel were measured with a high‐speed vertical density profiler. The resulting scale (LT)rms, known as the Thorpe scale is compared to the Ozmidov scaleLR=(&egr;/N3)1/2and the Eulerian turbulent scalel=2&rgr;′/(d&rgr;¯/dz). For buoyancy‐dominated or stratified turbulence,land (LT)rmsare linearly related, but when all turbulent overturning events have ceased, (LT)rmsis shown to decay at a faster rate. Vertical displacements larger than the Ozmidov scale are observed implying that some previously turbulent scales have become fossil turbulence.

ISSN:0031-9171    

DOI:10.1063/1.864704

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A method for optimizing stellarator vacuum magnetic fields is introduced. Application of this method shows that the stochasticity of vacuum magnetic fields can be made negligible by proper choice of the coil configuration. This optimization is shown to increase the equilibrium &bgr; limit by factors of two or more over that of the simple, ‘‘straight’’ coil winding law. This method is general and ought to be applicable to other systems in which stochasticity (1) presents a problem, yet (2) is affected by the design parameters.

ISSN:0031-9171    

DOI:10.1063/1.864692

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

The linear stability of a helical quasi‐equilibrium containing large‐amplitudeq=2 magnetic islands in a cylinder is investigated. Three‐dimensional tearing modes are driven unstable by the strong current gradient associated with this helical equilibrium.

ISSN:0031-9171    

DOI:10.1063/1.864693

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

Axisymmetric line‐tying, as may occur in anH‐mode discharge or in a toroidal limiter, is modeled through a rigid or conducting boundary condition. It is shown effective in reducing the linear growth rate of global free‐boundary magnetohydrodynamic modes in high‐ &bgr;pcircular cross‐section tokamaks. Various parameter dependencies are also examined.

ISSN:0031-9171    

DOI:10.1063/1.864694

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A class of semi‐analytical equilibria for rotating compact tori with toroidal current density vanishing at the separatrix is presented.

ISSN:0031-9171    

DOI:10.1063/1.864695

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

The stabilization mechanism of the spheromak tilting instability is investigated by means of a 3D magnetohydrodynamic simulation. Evidence that line‐tying can completely suppress a tilting instability is observed. It is also found that the stabilization effect of an induction current induced on a conducting wall is weaker than the line‐tying effect.

ISSN:0031-9171    

DOI:10.1063/1.864696

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

Numerical solutions of the linearized magnetohydrodynamic equations are used to investigate resonant energy absorption in the continuous frequency spectrum. Energy in the phase‐mixed surface waves resistively dissipates with the absorption time and width scaling as resistivity to the −1/3 and 1/6 powers, respectively.

ISSN:0031-9171    

DOI:10.1063/1.864697

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

Experimental measurements of internal energy in the ZT‐40M Reversed Field Pinch are presented that reinforce the interpretation of the soft x‐ray sawtooth oscillations seen in that device as indicating an internal energy loss. Soft x‐ray spectra are presented that support the contention that hot electron confinement, as well as energy confinement, is severely degraded by the presence of large scale sawteeth, presumably during the fall time of the soft x‐ray flux. The behavior of the equilibrium fields may be explained as the result of a combination of current redistribution and a decrease and recovery in internal &bgr;pduring a sawtooth.

ISSN:0031-9171    

DOI:10.1063/1.864705

出版商:AIP    

年代:1984

数据来源: AIP