摘要:

The dilute Bose gas is considered in the Bogoliubov approximation for the purpose of accounting for the quantization of circulation for the entire superfluid. It is found that the states of lowest energy have the motion of the entire system governed by the condensate.

ISSN:0031-9171    

DOI:10.1063/1.1762139

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The linear stability of a symmetrical two‐dimensional parabolic flow is investigated. A parameter is included so that the primary flow can be varied from the parabolic Poiseuille flow with zero‐velocity gradient at the centerline to the linear symmetrical flow. The results show that all flows for which this parameter exceeds a critical value are stable at all finite Reynolds numbers.

ISSN:0031-9171    

DOI:10.1063/1.1762140

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The solution of the two‐dimensional gravity waves in a plane stratified ocean previously calculated by the authors is rectified. By formulating a corresponding initial value problem, the steady‐state solution becomes completely determinate without using the radiation condition.

ISSN:0031-9171    

DOI:10.1063/1.1762141

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

An experimental study of the effect of tube length‐to‐diameter ratio,L/d0, on the expansion and contraction of jets of Newtonian liquids into air is described. For Reynolds numbers based on tube diameter, Red, above 16 the jets contracted. Jet diameter correlated with the degree of development of the velocity profile in the tube, a function ofL/d0, and was unaffected by viscous dissipation. At Red= 16 the jet diameter was equal to the tube diameter and was independent ofL/d0. When Red< 16 the jets expanded. Jet diameter was affected by viscous dissipation. Most of the data in this range could be correlated as a function of the Reynolds number based upon tube length, ReL, and of the ratio of the Brinkman number to the product of the Prandtl number and ReL. How the stresses acting in the jet and in the tube are influenced by profile development and by viscous dissipation and affect jet diameter is discussed.

ISSN:0031-9171    

DOI:10.1063/1.1762142

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A general solution of the linearized Boltzmann equation with the Bhatnagar‐Gross‐Krook model for the problem of a rarefied gas flowing between two parallel, infinite plates is developed based on the discrete ordinate method. Analytic expressions of the perturbed distribution function, the velocity profile, and the gas volume flow rate, particularly suitable to numerical calculations, are thus obtained. These make possible obtaining the numerical solutions to any desired degree of accuracy. The results are compared with the analytical solutions of the half‐range moment method and with the numerical solutions of Cercignani.

ISSN:0031-9171    

DOI:10.1063/1.1762143

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A theory of surface nucleate boiling complying with recent evidence of significant heat extraction from the ebullition surface during bubble growth, but not presuming an evaporating liquid film at the bubble base.

ISSN:0031-9171    

DOI:10.1063/1.1762144

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

Higher‐order time‐correlations and the associated skewnesses and flatnesses were measured in a turbulent field downstream of a grid using high‐speed computing techniques. The results were obtained using samples of 160 020 digitized data recorded at time intervals of 1/12 800 sec during time periods of approximately 12.5 sec. Comparison is made between the measured correlations and the higher‐order correlation curves corresponding to a Gaussian probability density distribution of turbulent velocities. The departures from Gaussianity are shown, and non‐Gaussian probability distributions are proposed which correspond considerably better to experimental reality. Several relations between correlation coefficients of different orders are obtained for the non‐Gaussian probability distributions and confirmed by comparison with the measured correlations, skewnesses, and flatnesses.

ISSN:0031-9171    

DOI:10.1063/1.1762145

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The fluorescence stimulated by a 17.5‐kV electron beam probe was used to obtain measurements of rotational temperature and gas density in supersonic nitrogen jets expanding from room temperature. The parameterP0d(whereP0is the stagnation pressure in Torricelli anddis the orifice exit diameter in millimeters) was varied from 15 to 480 Torr‐mm. Density measurements were made using an interference filter‐photomultiplier combination. The experimental density data follow the axial isentropic density distribution in regions of rotational nonequilibrium. Rotational temperature measurements were obtained from rotational spectra of the 0–0 band of the N2+first negative system. The experimentally determined rotational temperatures, which initially follow the axial isentropic temperature distribution in a free jet, depart from the isentropic curve at low temperatures and freeze at a constant value, indicating a substantial degree of nonequilibrium in the expansion. A shock holder was inserted in the jet and a number of shock waves in the rangeM= 4 toM= 15 were investigated. Rotational spectra indicate a large departure from a Boltzmann distribution in the rotational levels in the center of a shock front. An apparent non‐Boltzmann rotational distribution in the jet expansion was also observed.

ISSN:0031-9171    

DOI:10.1063/1.1762146

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The one‐dimensional phenomena which occur when shock‐induced flows in ideal gases interact with transverse magnetic fields of finite extent are analyzed from both the steady‐state and transient viewpoints. The steady‐state analysis assumes steady flow exists within the interaction zone. It is shown that there are four types of interactions. These involve the presence or absence of standing or upstream‐propagating reflected shock waves, and rarefaction waves on the downstream side of the interaction zone. The types of interactions are functions of the initial Mach number of the shock‐induced flow, the interaction parameter, the magnetic Reynolds number, and the amount of electrical energy withdrawn from the flow. The method of characteristics is used to analyze transient phenomena. The transient problem is described by a five‐characteristic network, which is reduced to four characteristic directions when the flow velocity is small compared to the electromagnetic signal velocity. The transient analysis can be used to determine the position where the reflected shock wave forms and the length of time required for the flow within the interaction zone to approach steady‐state conditions.

ISSN:0031-9171    

DOI:10.1063/1.1762147

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A model for a turbulent shock wave with a structure determined by ion wave instabilities is discussed. Quasi‐linear theory for spatially growing waves is used to examine the spatial buildup of the turbulent spectrum in the leading edge of the shock transition. Although the principal calculations are made for an electrostatic shock, the response of a weak magnetic field in the plasma to such a thin ion‐wave shock is also discussed. It is suggested that the earth's bow shock in the supersonic solar wind may sometimes have a structure of the type described here and a comparison with satellite data for this shock wave is made.

ISSN:0031-9171    

DOI:10.1063/1.1762148

出版商:AIP    

年代:1967

数据来源: AIP