ISSN:0031-9171    

DOI:10.1063/1.3480118

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

When a thin layer of liquid flowing down an inclined solid surface becomes unstable, a dry region may appear. It is of general engineering interest to identify the parameters which control the ability of the liquid to rewet the solid so that a uniform film of liquid can be reestablished. The role played by the contact angle in the rewetting process is investigated by performing a specific set of experiments of the type introduced by Huppert [(Nature300, 427 (1982)]. It is found that a small static advancing contact angle promotes rewetting, while a large value of the angle does not.

ISSN:0031-9171    

DOI:10.1063/1.865410

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

We have made precision measurements of the vortex pair size and wavy mode amplitude of vortices in wavy Taylor–Couette vortex flow. These results are compared to a model advanced by Park and Crawford to account for expulsion of vortex pairs as the Reynolds number is increased in the wavy‐vortex regime.

ISSN:0031-9171    

DOI:10.1063/1.865129

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Qualitative arguments suggest that the Kolmogorov 1941 (K41) inertial range for space dimensionality D3 corresponds to a maximum attractor size if compared with alternative inertial ranges in which intermittency increases as a power of wavenumber. Therefore upper bounds on attractor size consistent with K41 do not either rule out or imply intermittency corrections to the −5/3 law. In contrast, the K41 inertial range corresponds to minimum attractor size ifD>4.

ISSN:0031-9171    

DOI:10.1063/1.865189

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The development of a highly unidirectional lower‐hybrid wave source would improve the electron current drive efficiency in tokamaks. Lower‐hybrid waves launched from a phased wave array are shown to be reflected from a grid placed in a cold, low‐density plasma. The antenna–grid combination results in highly unidirectional lower‐hybrid waves.

ISSN:0031-9171    

DOI:10.1063/1.865413

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Anomalously enhanced fast‐electron losses are observed on relativisticElayers in the RECE‐Christa device when the applied toroidal magnetic field decreases to zero in times shorter than ring lifetime. These losses consistently occur in a certain region of the field‐reversal parameter and the ratio of applied toroidal to axial magnetic fields at the ring position. The critical parameter range is independent of the radial gradient of the applied mirror field, the background gas pressure, and the rate‐of‐decay ofB&thgr;; however, it depends on the axial length of the rings, and there may be a threshold indB&thgr;/dt. The observed parameter dependence as well as the absence of any kink or tilt motions point to new orbital resonances as the cause of these losses.

ISSN:0031-9171    

DOI:10.1063/1.865174

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The linear mode conversion of a plasma wave to a light wave in a magnetized plasma has been examined theoretically and by computer simulation. This conversion is the inverse of resonance absorption exhibiting an identical dependence on magnetic field and density scale length with an optimum conversion efficiency of approximately 60%. Radiation from this source may contribute to the harmonic spectra observed from laser‐irradiated plasmas.

ISSN:0031-9171    

DOI:10.1063/1.865177

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Thermal self‐focusing of laser light may be significant when a plasma is irradiated with short‐wavelength laser light. Self‐focusing magnifies the light intensity which can increase absorption by plasma waves (producing hot electrons which may cause preheat), could increase scattering, and could be a perturbation source for the Rayleigh–Taylor instability. We use two‐dimensional hydrodynamic simulations to characterize thermal self‐focusing for parameters of interest to laser fusion applications, and present a simple model. A diverging beam is shown to reduce the self‐focusing.

ISSN:0031-9171    

DOI:10.1063/1.865180

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A viscous jet is not usually observed to separate from a sharp edge in the manner expected theoretically. In the present paper the separation of a creeping jet emerging from a tube with a rounded exit is considered. As a separation criterion, in the absence of surface tension, we propose that the traction normal to the nozzle surface drops to zero at the separation point. Boundary‐element calculations then show a behavior that agrees with experimental data and with previous finite‐element computations. They also permit the Michael condition to be observed at separation, so that the discrepancy between finite‐element calculations and theory is removed.

ISSN:0031-9171    

DOI:10.1063/1.865185

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Unstable, two‐fluid miscible displacements in a Hele Shaw cell of plate spacingbare analyzed by considering viscous dissipation of energy. A perturbation theory is presented that predicts the wavelength of fingers, &lgr;, as &lgr;≊4b. Experiments with a circular Hele Shaw cell are shown to support this result. In a porous medium, the analogous fingers are demonstrated to be the size of a pore, which is much larger than the corresponding fingers in the analogous Hele Shaw cell. These results provide the lower limits of finger wavelength for the theories of Saffman and Taylor, and Chuoke, van Meurs, and van der Poel.

ISSN:0031-9171    

DOI:10.1063/1.865195

出版商:AIP    

年代:1985

数据来源: AIP