摘要:

An analysis is presented of third‐order resonant interactions in capillary‐gravity waves. When dissipation is accounted for, the theory predicts the amplitude of the third harmonic near the resonant frequency and at the early stage of the interaction. A more detailed account of the viscous effects is needed when these effects dominate the interaction.

ISSN:0031-9171    

DOI:10.1063/1.861793

出版商:AIP    

年代:1977

数据来源: AIP

摘要:

The energetic isotropic turbulence generated by a waterfall of low head was found to be developed in part through the unstable two‐phase flow of entrained air bubbles. The resulting turbulent field had a turbulent Reynolds number of ≳2×104and maintained a self‐similar structure throughout the decay period studied. The present study may provide some insight into the structure of turbulence produced by the breaking waves over the ocean.

ISSN:0031-9171    

DOI:10.1063/1.861794

出版商:AIP    

年代:1977

数据来源: AIP

摘要:

Using measurements of all three components of the temperature dissipation &khgr; in a laboratory boundary layer, the measured probability densityp(&khgr;r) of &khgr;r, or &khgr; averaged over a distancer, is found to be closely log‐normal over a significant range ofr. The variance &sgr;2of ln&khgr;rfollows the relation &sgr;2=A+&mgr;ln(L/r), with &mgr;=0.35, whereLis an integral scale of turbulence. High order moments, up to order 5, of &khgr;rshow a power‐law variation withr/L. With increasing order of the moment, the power‐law exponents become increasingly smaller than the corresponding values implied by assumed log‐normality ofp(&khgr;r) but are consistent with the bounds given by Novikov’s theory. It is suggested that the observed close agreement with log‐normality ofp(&khgr;r) may be misleading when sufficiently high order moments of &khgr;rare considered.

ISSN:0031-9171    

DOI:10.1063/1.861795

出版商:AIP    

年代:1977

数据来源: AIP

摘要:

The thermal slip of a binary mixture of gases along a spherical surface having a small curvature is studied. The Boltzmann equation with a model collision integral is used. The thermal slip coefficient obtained coincides with the result derived earlier in the limiting case of the thermal slip of the binary mixture along a flat surface.

ISSN:0031-9171    

DOI:10.1063/1.861796

出版商:AIP    

年代:1977

数据来源: AIP

摘要:

The problem of an arbitrarily conducting porous sphere moving slowly through a current‐carrying, incompressible, and viscous fluid is studied. The effect of permeability on the flow has been studied analytically at low Reynolds number by means of matched asymptotic expansions. The drag force up to order Re is reduced by a factor 1+K/2,Kbeing the permeability associated with the porosity of the sphere. Further, the permeability as well as the current tend to increase the length of eddies behind the porous sphere.

ISSN:0031-9171    

DOI:10.1063/1.861797

出版商:AIP    

年代:1977

数据来源: AIP

摘要:

Mass motions of a plasma are numerically analyzed for a discharge from a central small screen electrode of circular cross section and two other screen electrodes covering the two ends of a circular tube. In effect, there are two oppositely directed discharges from the central electrode and this simplifies the analysis. Rotational electromagnetic forces cause two large eddies, each with a region of high velocity or a jet on either side of the central electrode. The case is further computed where the plasma is allowed to flow from one end to the other through the tube and the screen electrodes. The plasma entering the end screen electrode flows around the eddy lying between the electrode and the central electrode. This provides a recirculating and confined motion associated with the first discharge. As the plasma flows farther downstream, it is drawn to the axis of the second discharge and becomes a part of its jet.

ISSN:0031-9171    

DOI:10.1063/1.861798

出版商:AIP    

年代:1977

数据来源: AIP

摘要:

The steady diffuser flow of a viscous incompressible fluid with a finite electrical conductivity in the presence of an external magnetic field is analyzed by means of similarity theory. Power series expansions for the velocity and induced magnetic fields are presented, and discussed as dependent on the Reynolds, Hartmann, magnetic Reynolds numbers, and duct angle. Short‐circuit current and the critical values of magnetic Reynolds number and duct angle for flow separation are calculated. It is shown that the induced magnetic field changes the velocity profile and considerably reduces the critical duct angle at which flow separation occurs. The critical magnetic Reynolds number for flow separation becomes smaller as the Reynolds number increases.

ISSN:0031-9171    

DOI:10.1063/1.861799

出版商:AIP    

年代:1977

数据来源: AIP

摘要:

The problem of coupled thermal and chemical relaxation in a nitrogen‐argon plasma mixture is studied for the case of thermodynamic nonequilibrium. Firstly, the equations which describe the time evolution of macroscopic quantities such as temperature and concentration are studied; then, the computation of some plasma evolutions is performed. As a result, the coupled thermal effect on the reaction and the chemical effect on thermal relaxation are shown.

ISSN:0031-9171    

DOI:10.1063/1.861800

出版商:AIP    

年代:1977

数据来源: AIP

摘要:

Linear Langmuir wave damping by collisions is studied in the limit of collision frequency &ngr; approaching zero. In this limit, collisions are negligible, except in a region in velocity space, the boundary layer, centered about the phase velocity. If &kgr;, the ratio of the collisional equilibration time in the boundary layer to the Landau damping time, is small, the boundary layer width scales as &ngr;1/3, and the perturbed distribution function scales as &ngr;−1/3. The damping rate is thus independent of &ngr;, although essentially all the damping occurs in the collision‐dominated boundary layer. Solution of the Fokker–Planck equation shows that the damping rate is precisely the Landau (collisionless) rate. The damping rate is independent of &kgr;, although the boundary layer thickness is not.

ISSN:0031-9171    

DOI:10.1063/1.861801

出版商:AIP    

年代:1977

数据来源: AIP

摘要:

The stability of coupled Langmuir and ion‐acoustic solitons has been investigated by means of numerical computations. Using the Zakharov equation to describe the envelope of the oscillating electric field, and the Korteweg–de Vries equation with the ponderomotive driving term, to describe the low‐frequency electron density variation, it was found that (1) Langmuir waves and short scale sound waves do not affect the soliton; (2) two solitons destroy each other when colliding; and (3) a long scale sound wave or ion‐acoustic soliton break up a coupled soliton in the interaction. Moreover, no initial condition far from a soliton state was found which would create a coupled soliton.

ISSN:0031-9171    

DOI:10.1063/1.861802

出版商:AIP    

年代:1977

数据来源: AIP