摘要:

The viscous damping of the capillary oscillations of a simple drop in rotation in air is evaluated in the small viscosity limit.

ISSN:0031-9171    

DOI:10.1063/1.865364

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Based on a nonlinear, local mode–mode coupling relation, the resonant interaction of flute‐interchange modes with radio frequency (rf ) wave fields in the ion‐cyclotron range of frequencies (ICRF) is studied. It is shown that interchange modes can be stabilized because of resonant coupling to electrostatic ion‐cyclotron sidebands. Stabilization takes place if the frequency of the rf field is somewhat higher than the local ion‐cyclotron frequency, as observed in contemporary experiments on mirror devices.

ISSN:0031-9171    

DOI:10.1063/1.865365

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Low Reynolds number flow over rectangular cavities is analyzed. The problem is posed to simulate towing tank experiments of Taneda [J. Phys. Soc. Jpn.46, 1935 (1979)]. A very good agreement exists between numerical and experimental results. The dividing streamline separates from the cavity side wall below the upper corner. The separation point moves toward this corner when the aspect ratio decreases. Flow structure inside the cavity changes considerably with the aspect ratio. Only corner vortices exist in a cavity of aspect ratioW/h=4.0. A decrease of the aspect ratio leads to the enlargement and eventual merger of these vortices. The merger begins with the formation of a stagnation point separating two vortex centers inside the cavity. These vortex centers become progressively weaker and merge to form a single central vortex in a cavity of aspect ratioW/h=2.0. Further decrease of the aspect ratio results in the enlargement of the new corner vortices and their eventual merger. This process begins in a cavity of aspect ratio between 0.6 and 0.575 and is finished in a cavity of aspect ratio 0.5, where two central vortices have been identified. The further decrease of the aspect ratio leads to the sequential repetition of this process and creation of additional central vortices.

ISSN:0031-9171    

DOI:10.1063/1.865366

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The question is addressed as to the dependence of sedimentation of a homogeneous suspension on the shape of the container. It is demonstrated, by comparing calculations for spherical and plane geometries, that shape‐dependent contributions to the sedimentation velocity remain in the limit of infinitely distant container walls. Upon transformation from the laboratory reference frame to a local frame of reference that moves with the average volume velocity, this shape‐dependence is found to disappear.

ISSN:0031-9171    

DOI:10.1063/1.865367

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The linear stability of liquid film flow, when the viscosity depends exponentially on temperature, is investigated here for the case of heating or cooling from below by means of an analysis valid for long waves. It is shown that cooling stabilizes the flow, while heating destabilizes it. For the case of cooling, a cutoff Prandtl number exists, above which the flow is stable with respect to long waves.

ISSN:0031-9171    

DOI:10.1063/1.865368

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The propagation of undamped transverse thermal waves in a layer of binary mixture is investigated. It is shown that when the thermal diffusivityKTis equal to the mass diffusivityKS, such waves do not exist. But whenKT>KS, these waves may exist provided the layer is heated from below (such that thermohaline instability does not occur) and the concentration of the solute in the mixture decreases vertically upward. The analysis also reveals the interesting result that whenKT<KS, undamped waves can propagate even if the layer is heated from above provided the concentration increases vertically upward. It is further shown that as in a homogeneous fluid, weakly damped low‐frequency waves can propagate and the regions in the parameter space where such propagation is possible are delineated. High‐frequency waves are shown to be always strongly damped.

ISSN:0031-9171    

DOI:10.1063/1.865369

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A method of extracting the behavior of velocity/vorticity fields caused by the low‐frequency, or infrared (IR), portion of nonlinear interactions in arbitrary spatial dimensions is transcribed from the Schwinger/Fradkin representation of Green’s functions in quantum field theory to problems of viscous Navier–Stokes fluids. The general IR formalism is developed and applied to certain simple, two‐dimensional situations involving point vortices and vortex sheets. As an illustration point vortices inserted into a viscous fluid are shown to perform a finite number of revolutions about each other before they dissipate and disappear.

ISSN:0031-9171    

DOI:10.1063/1.865370

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Anisotropy of the diffusion of a passive scalar is studied statistically by means of the direct‐interaction approximation incorporated with the multiscale expansion method. The scalar flux generated by turbulent shear flows is calculated up to the second order of a scale parameter. As a result, a relation between the anisotropy of scalar diffusion and the inhomogeneity of turbulent flows is shown.

ISSN:0031-9171    

DOI:10.1063/1.865371

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The dynamics of a mixture ofNrarefied gases is studied by analyzing the set of nonlinear continuity equations for the number densities. Removal and regeneration effects are also taken into account. Various physical situations are considered, corresponding toN=2 andN=3. The relevant diagrams (trajectories in the phase space and curves of the single densities as functions of time) are reported and briefly discussed on physical grounds.

ISSN:0031-9171    

DOI:10.1063/1.865372

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The effect of internal degrees of freedom and of a class of boundary conditions on inverted temperature profiles between evaporating and condensing parallel plates is considered. It is found that such inverted profiles are present also in the case of polyatomic species and for most (but not all) modifications of the boundary conditions.

ISSN:0031-9171    

DOI:10.1063/1.865373

出版商:AIP    

年代:1985

数据来源: AIP