摘要:

A nonlinear mode‐coupling theory of the lower‐hybrid‐drift instability is presented. It is found that the instability saturates by transferring energy from the growing, long wavelength modes to the damped, short wavelength modes. The saturation energy, mean square of the potential fluctuations, and diffusion coefficient are calculated self‐consistently.

ISSN:0031-9171    

DOI:10.1063/1.864187

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

By considering electrostatic surface waves propagating along a plasma cylinder, it is demonstrated that solitary variations in the cylinder radius may appear. The properties of these slow perturbations are determined by the surface wave intensities.

ISSN:0031-9171    

DOI:10.1063/1.864188

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

The stability of layer modes is analyzed forz‐pinch and bumpy cylinder models. These modes have long wavelength across the layer and are flute‐like along the field line. The stability condition can be expressed in terms of the ratio of hot to core plasma density. It is shown that to achieve conditions close to the Lee–Van Dam, Nelson core beta limit, one needs a considerably smaller hot‐to‐core plasma density ratio than is required to achieve stability at zero core beta.

ISSN:0031-9171    

DOI:10.1063/1.864189

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Ion heating is studied in an unmagnetized and nonisothermal plasma (Te0≫Ti0). The ion temperature increases linearly with time while the ions sample the finite turbulence. The ions are significantly heated (Ti/Ti0≳10) when ion wave turbulence is large (&Dgr;n/n≳10%). The measured results agree with a simplified theory and one‐dimensional particle simulation results.

ISSN:0031-9171    

DOI:10.1063/1.864190

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Two wavy plates, separated by a viscous fluid, move relative to each other in a direction normal to the corrugations. Assuming small‐amplitude corrugations and low Reynolds number, the unsteady Navier–Stokes equations are solved by perturbations. It is found not only that the mean drag is increased, but that an unsteady drag and an unsteady lift are also induced by the corrugations. These fluid‐induced vibrations, predicted for the first time, may be important in the design of grooved sliders.

ISSN:0031-9171    

DOI:10.1063/1.864191

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

The problem of the laminar flow through a circular pipe, rotating with constant angular velocity about an axis perpendicular to the axis of the pipe, is studied. The full equations of motion are solved numerically, using a Fourier decomposition in the angular direction. As a test of the numerical scheme, the similar problem of flow through a loosely coiled pipe is also studied, and the results obtained are seen to agree well with the existing solutions.

ISSN:0031-9171    

DOI:10.1063/1.864192

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

A flow visualization study of the onset and behavior of secondary motions in laminar flow of a liquid film descending over a concave surface is presented. The observed secondary flow resembles the Go¨rtler vortices found in flow over a fully submerged concave surface. The dependence of the wavelength of the instability on flow parameters and the possibility that the instability mechanism is active in coating flows are discussed.

ISSN:0031-9171    

DOI:10.1063/1.864193

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

The equations governing melt stability during solidification of a binary alloy are shown to resemble those characterizing the Be´nard problem with permeable boundaries. Critical conditions for the onset of stationary convection are calculated for the case of a planar interface. Long wavelength modes are preferred when the segregation is small.

ISSN:0031-9171    

DOI:10.1063/1.864194

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

An analytic theory of the stability of thin ablation fronts is developed. Large wavenumbers are found to be stabilized by lateral heat conduction; this results in maximum growth rate of orderg/vat wavenumber of orderg/v2, wheregis the acceleration of the front andvthe ‘‘exhaust’’ velocity of the ablated material. For typical ablation front parameters the model predicts that implosions with shell aspect ratios of at least 20 should be viable.

ISSN:0031-9171    

DOI:10.1063/1.864175

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Convection induced by insulated boundaries in a tilted square cavity is analyzed for large external Rayleigh numberA. Two opposite walls of the cavity are insulated, and the other opposite walls are maintained at temperatures linear in &xgr;, the vertical coordinate. Two orientations of the cavity are analyzed in detail for &fgr;<A−1/2and &fgr;=&pgr;/2, &fgr; being the angle between the heated walls and the horizontal. For &fgr;<A−1/2, the flow consists of boundary layers of thicknessO(A−1/4) near the insulated wall andO(A−1/6) near the heated walls. For &fgr;=&pgr;/2, the flow consists of double boundary layersO(A−1/6) andO(A−1/8) near the insulated walls, but no boundary layer exists near the heated walls, except at the end points of the double boundary layers. The flows for &pgr;/4 are qualitatively described. The analogy between the flows considered here and those in a rotating container is also discussed.

ISSN:0031-9171    

DOI:10.1063/1.864176

出版商:AIP    

年代:1983

数据来源: AIP