摘要:

An asymptotic method based upon the ray theory is extended to the study of planetary waves in a fluid of variable depth over the rotating earth. An asymptotic solution involving a phase function and an amplitude function is constructed. Application of the method to the study of wave resonance of a compressible fluid in a rotating spherical shell is considered.

ISSN:0031-9171    

DOI:10.1063/1.861005

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

The equations of Euler are integrated numerically for isotropic homogeneous box turbulence. The triple correlations build up, and the correlations of order five and seven show some evidence of strong phase relations near the end of the spectral range. The stretching of vorticity occurs mostly in directions perpendicular to local collision axis, and at points showing strong velocity gradients. These properties agree with experimental or analytical results. Some stability tests are described.

ISSN:0031-9171    

DOI:10.1063/1.861006

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

Solutions for uniformly‐sheared turbulence, in which the interaction of the turbulence with the mean shear dominates the turbulent self‐interaction, are compared with experiment. An anisotropic spectral tensor, which appears general enough to represent the initial experimental turbulence, is used for the initial condition in the calculations. The evolution of one‐point turbulence components and microscales, as well as two‐point velocity correlations, are considered. In most cases the agreement with experiment is good. The theory correctly predicts the presence of a negative region for two‐point longitudinal‐velocity correlations only for point separations in the direction normal to the flow and the mean gradient.

ISSN:0031-9171    

DOI:10.1063/1.861007

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

An exact turbulence dissipation equation in the generalized relative system is presented. Simplified forms of the equation are obtained for computational purposes in the high Reynolds number approximation. Modeling of the rotation term is proposed. Modeling of the other higher‐order terms is also presented in a generalized system using the tensor invariance technique. An estimate of the angular velocity is provided for the rotation term to be included in the turbulence dissipation equation. The associated significant curvature terms for turbomachinery flows are also identified.

ISSN:0031-9171    

DOI:10.1063/1.861008

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

The hierarchy of equations for the multipoint distribution functions is developed for compressible turbulent flow. The compressible equations reduce to previously published relations for incompressible fluids with constant transport under the appropriate approximations. Expressions for other types of incompressible fluids are also shown to be derivable from the compressible relations.

ISSN:0031-9171    

DOI:10.1063/1.861009

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

Analytical and experimental studies have been carried out on the behavior of strong shock tube diaphragms. These diaphragms exhibit large moments of resistance to opening due to stresses at the hinge line of the diaphragm petal. High speed shadowgraph photographs of the detailed opening process have been obtained and have been shown to compare well with the analytical model derived for flowfield‐diaphragm interaction. A nondimensional resistance parameter is shown to control the behavior of the thick diaphragm and the detailed flow process which controls the opening is identified.

ISSN:0031-9171    

DOI:10.1063/1.861010

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

The diffusion of a tracer gas from a plane, porous boundary into a steady, rarefied background is investigated using the BGK model to account for collisions between the tracer and the background molecules. In a limited region close to the central part of the wall the diffusion process is nearly one‐dimensional, and the resulting kinetic diffusion equation is shown to be identical to the shear flow equation in the Kramers problem of flow along an infinite wall. This observation suggests that density measurements, rather than measurements of velocity, can be used to assess the validity of the linearized BGK model in describing flows in kinetic boundary layers. Estimates of the required sensitivity of the experimental technique are given.

ISSN:0031-9171    

DOI:10.1063/1.861011

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

The spectrum of ideal magnetohydrodynamics in toroidal systems is shown to concentrate around three continua where the singular fast, the Alfve´n, and the slow modes become polarized purely normal and purely tangential to the magnetic surfaces. A new toroidal effect is encountered, viz., coupling of the Alfve´n and slow continuum modes by the presence of geodesic curvature. Due to this effect the slow and Alfve´n modes are no longer polarized purely parallel and purely perpendicular to the field lines as they are in the case of the diffuse linear pinch. The pure polarizations of these continuum modes are only found asymptotically when &ohgr;2→∞, which point turns out to be a clusterpoint of all three kinds of magnetohydrodynamic modes characterizing each of them uniquely.

ISSN:0031-9171    

DOI:10.1063/1.861012

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

The effects of electron inertia and mode conversion on the propagation of Alfve´n waves in toroidal magnetic fields are considered. When electron inertia is neglected, two singularities occur in the equation determining the radial and vertical wavefield dependencies. The inclusion of electron inertia resolves one singularity and is shown to lead to linear mode conversion in either a cold electron or warm electron approximation. The Alfve´n wave converts to an electrostatic wave which propagates back toward the inside of the torus in the cold electron approximation and through the ion cyclotron resonance toward the outside edge of the torus with warm electrons via the electrostatic ion cyclotron wave. Without damping, both lead to a discrete spectrum of eigenfrequencies, but with only weak damping, the electrostatic waves are absorbed and lead to a continuous spectrum of frequencies. The nature of the damping terms gives an indication of the type of energy absorption, whether Landau damping of electrons or ions or ion cyclotron damping. The second singularity in the equations is found to have only regular solutions and does not lead to mode conversion.

ISSN:0031-9171    

DOI:10.1063/1.861013

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

Equations of dissipative magnetohydrodynamics are solved numerically for an axisymmetric toroidal pinch. A circular cross‐section screw pinch is treated, although the method is general and extendable to other geometries. Calculated results are compared with experimental results of the SP‐1 machine at Jutphaas. Very good agreement is attained, indicating that on short time scales, magnetohydrodynamics gives a good representation of the physical phenomena.

ISSN:0031-9171    

DOI:10.1063/1.861014

出版商:AIP    

年代:1975

数据来源: AIP