ISSN:0031-9171    

DOI:10.1063/1.4738810

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Hot electrons have been produced by second harmonic electron‐cyclotron resonance heating in axisymmetric end mirrors of the tandem mirror GAMMA10 [Phys. Rev. Lett.55, 939 (1985)] with an on‐axis density fraction reaching 80% and temperature of 25–50 keV, satisfying theoretically required conditions for the formation of thermal barriers. The successful control of the electron temperature may be attributed to the relativistic detuning of the second harmonic resonance for localized microwave power absorption. The time evolutions of relevant parameters are studied with extensive diagnostics.

ISSN:0031-9171    

DOI:10.1063/1.865473

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The temperature distribution in an ellipsoidal liquid inclusion in a soluble solid, with a constant gradient far away from the liquid, and the movement of the liquid inclusion as a whole, which results as a consequence, are investigated. Since the solid is soluble and its concentration in solution is temperature dependent, any temperature variation in the liquid induces a concentration variation, which will transfer mass by diffusion, eroding the wall where the temperature is high and depositing solid material at the wall where the temperature is lower. This erosion or deposition will cause the liquid inclusion to move, and will, through absorption or release of latent heat, in turn affect the temperature distribution. From the result obtained for the general ellipsoid, specific results for prolate and oblate ellipsoids of revolution, the sphere, and circular and elliptic cylinders are obtained.

ISSN:0031-9171    

DOI:10.1063/1.865474

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The moderate‐amplitude, three‐dimensional oscillations of an inviscid drop are described in terms of spherical harmonics. Specific oscillation modes are resonantly coupled by quadratic nonlinearities caused by inertia, capillarity, and drop deformation. The equations describing the interactions of these modes are derived from the variational principle for the appropriate Lagrangian by expressing the modal amplitudes to be functions of a slow time scale and by preaveraging the Lagrangian over the time scale of the primary oscillations. The equations describing the motion of axisymmetric resonant modes are integrable. Stochastic motions are predicted for nonaxisymmetric deformations starting from most initial conditions, even those arbitrarily close to the axisymmetric shapes. The stochasticity is characterized by a redistribution of the energy contained in the initial deformation over all the degrees of freedom of the interacting modes.

ISSN:0031-9171    

DOI:10.1063/1.865475

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The motion of a two‐dimensional bubble rising at a constant velocity in an unbounded fluid is solved by series truncation. It is assumed that there is a wake of stagnant liquid extending to infinity below the bubble. Both the effects of gravitygand surface tensionTare taken into account. It is shown that the problem is characterized by a continuum of solutions forT=0 and by a discrete set of solutions whenT>0. In addition a unique solution is obtained in the limit as the surface tension approaches zero. The corresponding profile of the bubble is found to be in good agreement with experimental data.

ISSN:0031-9171    

DOI:10.1063/1.865476

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Numerical solutions are presented for large‐amplitude interfacial waves of extreme form on the interface between two fluids of different densities in the Boussinesq approximation. The flow in the lower fluid is irrotational, but the upper fluid may have constant, nonzero vorticity. Only symmetric waves are calculated. The results suggest limiting wave profiles for which separate portions of the interface touch, forming stagnant zones of one fluid imbedded in the other fluid.

ISSN:0031-9171    

DOI:10.1063/1.865477

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

It is demonstrated that only two‐dimensional perturbations need be considered in determining the marginal stability boundary in the parameter space for the incompressible, parallel flow of two stratified, homogeneous, immiscible fluids, with constant interfacial tension, bounded by two (possibly moving) parallel plates.

ISSN:0031-9171    

DOI:10.1063/1.865478

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The nonlinear interactions of waves on the interfaces of two‐ and three‐layer flows are studied. It is shown that in both flows there are resonant triads in which three waves have the resonant interactions, and that these triads have interactions through their common waves. This is called the multiple resonance. The total energy of the waves which take part in the multiple resonance is conserved; however, it is not conserved in each triad, which is not the case when the triad does not have interaction with other triads, and the energy of a triad is transferred to others. The solutions of the evolution equations of the amplitudes are studied analytically and numerically. It is shown that soliton solutions exist, and that in some cases the evolution of the amplitudes becomes irregular and chaotic. In the three‐layer flow the interactions are either of the ‘‘explosive type’’ or of the ‘‘decay type.’’ These types can be switched by time from one to the other. On the other hand, all of the interactions in the two‐layer flow are of the ‘‘decay type.’’

ISSN:0031-9171    

DOI:10.1063/1.865479

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Standing waves of finite amplitude in an enclosed basin are considered. It is shown that the existing theory of Tadjbakhsh and Keller [J. Fluid Mech.3, 442 (1960)] breaks down at a critical value of the amplitude dependent upon the depth. By formal perturbation expansion it is found that the solutions change to cnoidal standing waves at this critical value of the amplitude. An experiment is constructed which verifies this theory and also elucidates the wavefield when the amplitude is much larger than the critical amplitude. Based on the experimental observations, a cascade theory is proposed to explain the transition to a traveling hydraulic jump.

ISSN:0031-9171    

DOI:10.1063/1.865480

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The laminar flow in an axisymmetric sudden expansion has been studied experimentally. Using a nominal diameter ratio of 0.5 and well‐defined inlet velocity profile conditions, data are presented that, for the first time, demonstrate clearly that the onset of shear layer instabilities is dependent on the inlet velocity profile. The reattachment length of the shear layer (normalized by the expansion step height) as a function of the inlet Reynolds number is linear with slopes of 0.096 and 0.068 for upstream velocity profile conditions of Poiseuille and nominal plug flow, respectively.

ISSN:0031-9171    

DOI:10.1063/1.865481

出版商:AIP    

年代:1986

数据来源: AIP