摘要:

The classical Rayleigh‐Plesset equation of spherical bubble dynamics in an incompressible liquid is generalized to include the non‐Newtonian behavior of the liquid and mass exchange processes at the bubble interface.

ISSN:0031-9171    

DOI:10.1063/1.863775

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

Equations describing the resonant interaction between long internal waves and short surface waves are derived and represented in wavenumber space. Various evolution equations can arise depending on the slopes of the two wave fields and the ratio of their wavelengths. The existence of the internal waves will affect the stability of a short surface plane wave. A coupled set of transport equations is derived for deterministic internal waves and Gaussian random surface waves. The amplification rate of perturbations can be analyzed for a range of spectral bandwidths.

ISSN:0031-9171    

DOI:10.1063/1.863776

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

Steady two‐dimensional flow past a sail is considered. The sail is assumed to be supported by two masts. The flow and the shape of the sail are determined as functions of the direction &agr; of the flow at infinity and the Weber number &lgr;. The full nonlinear problem is formulated as an integrodifferential equation for the shape of the sail. This equation is discretized and solved numerically by Newton’s method. Sail profiles, the slack in the sail, and the lift coefficient are presented for various values of &agr; and &lgr;.

ISSN:0031-9171    

DOI:10.1063/1.863777

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

Hot‐wire velocity measurements in the free stream above turbulent spots generated in a laminar boundary layer on a flat plate show that the regions of largest positive and negative longitudinal potential flow disturbance occur at about 1.5 spot heights above the surface. These regions are located above the forward and rear primary foci previously identified as points of accumulation for particle paths and as extremal points for ensemble mean velocity and temperature perturbations. A three‐dimensional linearized quasisteady potential flow similarity solution for the flow field around a moving, growing bump on the wall, with a shape given by the measured unsteady boundary layer displacement thickness, exhibits the same main features as the measured potential flow field.

ISSN:0031-9171    

DOI:10.1063/1.863778

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

The transition from slightly viscous to viscosity‐dominated steady‐state, compressible, small‐disturbance flow is studied in the framework of the linearized Navier–Stokes equations. The classical picture of independent modes for vorticity, pressure, and temperature disturbances is preserved at all disturbance wavelengths down in the molecular scale. Particular transitions do, however, occur within the pressure mode itself, causing the governing equations to display new and qualitatively different features at the smaller disturbance wavelengths.

ISSN:0031-9171    

DOI:10.1063/1.863779

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

Self‐similar solutions for the nonadiabatic expansion of a gas in planar, cylindrical, and spherical geometry due to heating of a fairly general form are presented. The solution for an isothermal expansion which has previously been studied in the literature is recovered as a special case. Some additional examples of physical interest which reveal the variety of possible gas profiles resulting from the general solution are discussed.

ISSN:0031-9171    

DOI:10.1063/1.863780

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

The stability of hydromagnetic flow produced in a thin annular region between concentric cylinders by the interaction of a superimposed radial current and an axial magnetic field is examined both when the bounding cylinders are stationary and when rotating. After deriving the small gap approximation equations for the steady‐state one‐dimensional azimuthal flow and for the corresponding induced electric potential, the equations governing the growth of infinitesimal axisymmetric disturbances are obtained and solved at neutral stability by use of the Galerkin method. Stability results for the nonrotating cylinder case are shown to be expressible in terms of existing results for the stability of hydromagnetic flow produced by an azimuthal pressure gradient. It is found, in our thin film approximation, that the radial current must generally exceed a certain critical value before the one‐dimensional flow breaks down into a three‐dimensional pattern. Rotation of the outer cylinder enhances stability while rotation of the inner cylinder produces a greater tendency toward instability as reflected by lower Dean numbers at the onset of secondary flow.

ISSN:0031-9171    

DOI:10.1063/1.863781

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

An analytical model of a two‐phase liquid‐metal magnetohydrodynamic generator is developed. The model is based on the averaging equations governing the two‐phase flow in the channel of a liquid‐metal magnetohydrodynamic generator. The inhomogeneity of the distribution of the gas phase over the channel cross section is taken into account by introducing the correlation coefficients &bgr;1, &bgr;2, and &bgr;3: ⟨&agr;u⟩ = &bgr;1⟨&agr;⟩⟨u⟩, ⟨&sgr;u⟩ = &bgr;2⟨&sgr;⟩⟨u⟩, ⟨&rgr;u⟩ = &bgr;3⟨&rgr;⟩⟨u⟩. Expressions for these coefficients in terms of the correlation coefficient &bgr;1are obtained. The calculated characteristics of the generator were compared with experimental data obtained at the Argonne National Laboratory. The comparison shows that the calculated and measured characteristics are in fairly good (±15%) agreement.

ISSN:0031-9171    

DOI:10.1063/1.863782

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

A 140‐kJ theta‐pinch device originally constructed for spectroscopic investigations of highly ionized atoms is described. Atoms of solid elements are introduced into the initial plasma by laser‐driven ablation from solid targets. The stability of the field‐reversed plasma configuration is investigated with and without impurities. An inhomogeneous impurity distribution leads to the ejection of the plasma as a whole. This phenomenon is interpreted as the result of asymmetric field line reconnection at the ends.

ISSN:0031-9171    

DOI:10.1063/1.863783

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

Measurements are presented of the properties of lower‐hybrid waves excited at the edge of plasmas in the Alcator A tokamak by a two‐waveguide array operating at microwave powers up to 70 kW. The waves are studied directly in the plasma by measuring the small angle scattering of CO2laser radiation. A broadN∥spectrum is observed in the range 2⩽N∥≲8, with more intensity at lowerN∥(here,N∥is the parallel index of refraction). The waves are distributed throughout the minor cross section and do not appear to be localized in resonance cones. The wave amplitude is linear in net microwave power into the plasma. A power‐independent frequency width of several mega‐Hertz and a downshift in the frequency of the waves of the order of 1 MHz are observed. Finally, the wave amplitude is observed to be independent of the relative phase of the exciting, two‐waveguide array. Most of these results are explained by taking into account the scattering of the lower‐hybrid waves from the large‐amplitude, low‐frequency density fluctuations previously observed near the plasma edge.

ISSN:0031-9171    

DOI:10.1063/1.863758

出版商:AIP    

年代:1982

数据来源: AIP