摘要:

A method is outlined for the calculation of the wakes of small cylinders in hypersonic, collision‐free, cold‐ion plasma flow. No applied magnetic field is considered. Results are presented for a cylinder with a radius of 0.005 Debye lengths in a flow with a Mach number (based on the ion‐acoustic speed) of 8, and a comparison is made with available experimental data.

ISSN:0031-9171    

DOI:10.1063/1.1694616

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The problem of propagation of a two‐dimensional shock wave in water over a submerged rigid structure (semicylinder) due to a nearby underwater explosion has been solved numerically using a method of characteristics based upon a curvilinear co‐ordinate system fixed in successive shock wave positions. Maximum surface pressures occur at the transition from regular to irregular reflection, and nonlinear theory appears essential there, even for shocks of Mach number close to unity. Results are given for a range of explosive strengths, distances from the structure, and structural dimensions.

ISSN:0031-9171    

DOI:10.1063/1.1694618

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A super‐Alfve´nic and supersonic flow in a plasma wind tunnel were studied experimentally. The wind tunnel was constructed for the studies of the magnetohydrodynamic shock waves and wakes, and has features such as quasisteady flow and low fluctuation level. The Alfve´n Mach numberMAand ion acoustic Mach numberMcovered in the present experiment areMA = 1−4andM = 2−6A standing shock wave was found downstream of the magnetic‐nozzle exit. The shock wave is collision free and the normal of the wavefront is parallel to the magnetic field. Macroscopic features of the shock wave were discussed with reference to the theoretical predictions of the magnetohydrodynamic and collision‐free shock waves.

ISSN:0031-9171    

DOI:10.1063/1.1694619

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The two‐dimensional Navier‐Stokes equation and the drift approximation to the Vlasov equation are equivalent. An analytical theory of the turbulent state of this system is developed which contains no ad hoc assumptions. The theory is not strictly valid for the largest eddies and in the inertial range is restricted to large Reynolds numbers. A vorticity flow to large wavenumbers and an energy flow to small wavenumbers is predicted. In the inertial range the theory has a similarity solution whose spectrum agrees with that obtained from dimensional arguments. Diffusion coefficients are derived and the extension to shear turbulence and more general plasma turbulence is discussed.

ISSN:0031-9171    

DOI:10.1063/1.1694571

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Electric field autocorrelations for the two‐dimensional electrostatic guiding‐center plasma are calculated numerically. It is concluded that the autocorrelation, averaged over a thermal equilibrium ensemble, is damped in an approximately exponential fashion, as predicted by Taylor and McNamara. Oscillatory behavior of the type predicted by Taylor and Thompson is not observed.

ISSN:0031-9171    

DOI:10.1063/1.1694572

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Neoclassical diffusion in a stellarator is investigated in detail by introducing a consistent expansion in&lgr;1/3(where&lgr;is the inverse aspect ratio of the torus) for the magnetic fields and particle distribution function. As a result of the expansion, the various characteristic bounce and transit frequencies of the particle orbits appear in different orders, and various regimes of collision frequency (analogous to the “banana”, and “plateau” regimes of the axisymmetric analysis) are considered separately. It is found that over most of the range of collision frequencies the diffusion is the same as that of an equivalent axisymmetric configuration with the sole role of the helical fields being that of supplying the rotational transform. At sufficiently low collision frequencies particle trapping in the helical field modulations becomes important and localized particle diffusion dominates. Expressions for the diffusion flux and ion heat flux are derived in this limit.

ISSN:0031-9171    

DOI:10.1063/1.1694573

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Through the addition of an axial current‐carrying conductor (hard core), helical fields and magnetic shear have been added to the elongated toroidal plasma generated in a&thgr;‐pinch device operated with antiparallel bias field. Two‐dimensional(r, z)photographs indicate the presence, from the beginning of the discharge, of a persistent luminous helical structure imbedded in the annular plasma.

ISSN:0031-9171    

DOI:10.1063/1.1694574

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The axial flow and heating of an argon plasma in a pinched plasma column of a pulsed, linearz‐pinch device was experimentally examined with a unique pressure sensing instrument capable of resolving mass flow properties. Transient(∼ 5 &mgr;sec)axial pressure profiles identify periods of intense flow (4 × 104m/sec) and heating(Ti ∼ 70 eV);mechanisms generating such effects are considered.

ISSN:0031-9171    

DOI:10.1063/1.1694575

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The heating of a deuterium plasma created from solid granule (∼ 100 &mgr; diam; ∼ 1017particles) confined by strong magnetic fieldsB0up to 1 G is studied. Taking into account the inverse bremsstrahlung absorption process, an inhomogeneous hydrodynamic model is used to describe the plasma dynamics. The skin depth due to the diffusion of the magnetic field inside the plasma is calculated. Ohmic heating is taken into account. The magnetic body force for a diffusion plasma is given byJ × Bwhile for the infinite conductivity model the force is calculated from the magnetic pressureB02/2&mgr;0on the plasma boundary. The efficiencies for CO2lasers and neodymium glass lasers are compared. It is important to feed energy slowly to obtain a high efficiency of incident laser energy to the plasma thermal energy.

ISSN:0031-9171    

DOI:10.1063/1.1694576

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Based on the conservation equations for mass density, momentum, and energy, the coupled distributions of viscous flow and temperature in a wall‐stabilized arc in a transverse magnetic field are calculated. By means of Green's function of the biharmonic and the Laplace operator, respectively, the relevant equations are converted to integral equations which can be solved by an alternating iteration procedure. Examples are given for an argon arc and are compared with the experimental results.

ISSN:0031-9171    

DOI:10.1063/1.1694577

出版商:AIP    

年代:1974

数据来源: AIP