摘要:

The mean flows induced by the interaction of a two‐ and a three‐dimensional wave are calculated for a profile consisting of two straight lines. Although this is a simplified model of an actual boundary layer, the results are consistent with the experimental work done at the National Bureau of Standards.

ISSN:0031-9171    

DOI:10.1063/1.1711201

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

A discussion is given concerning the effects of viscosity and large disturbance amplitude on the instability occurring at a slip interface between two parts of an incompressible fluid. In particular it is shown how an analysis by Carrier can be applied to explain the train of small vortices generated at a shearing edge, and comparisons with experimental results are given for a number of examples. In addition, the numerical method of Fromm has been applied to obtain complete solutions of the slip instability problem, and numerous results are presented to show additional comparisons with the linearized theory for viscous fluids, and to show in detail the structure of the late‐stage nonlinear flow in which the vortex sheet may tend to ``roll up.''

ISSN:0031-9171    

DOI:10.1063/1.1711202

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

The dissipation of turbulent energy is examined in incompressible isotropic fluids in which deformation depends only on current values of strain rate (Reiner‐Rivlin fluids). For isotropic, homogeneous, decaying turbulence, two special cases are examined exactly—the Gaussian process and the inertial subrange. Generalizing from these and from known properties of turbulence in Newtonian media, it is concluded that anomalous properties of turbulence observed in non‐Newtonian media (the Toms effect) cannot be expected for a Reiner‐Rivlin model (nor for a simple power‐law fluid, which is a subclass) and that the explanation for these observations must therefore be sought in visco‐elasticity (i.e., dependence on history of strain). It is shown in addition that the form of the probability density of the strain tensor is almost surely quite sensitive to the form of the stress‐deformation relation.

ISSN:0031-9171    

DOI:10.1063/1.1711203

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

A new method of analysis has been devised for determining the developing laminar flow and corresponding pressure drop in the entrance region of tubes and ducts. The method is formulated in a general manner which applies to ducts of any cross section. Specific application is made for flow in a circular tube and in a parallel‐plate channel, and the velocity distribution and pressure‐drop results are compared with experimental data and prior analyses. These comparisons lend strong support to the findings of the present analysis.

ISSN:0031-9171    

DOI:10.1063/1.1711204

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

The influence of viscosity on the hot flow lengthland the testing time &tgr; in shock tubes is investigated for the laminar and turbulent cases. Considering the case where the influence of viscosity can be treated as a perturbation of the ideal flow, it is shown that Mirels' theory, which takes into account shock‐wave attenuation and wave reflections, can easily be used to evaluateland &tgr;.The limitations of the present theory are discussed and the results compared with the previous investigations. For the laminar case, the type of solution obtained is similar to that of Roshko. A ``maximum'' hot flow length, whose significance is mathematical rather than physical, because of the breakdown of the perturbation theory, is found. This ``maximum'' length is approximately twice as large as the one Roshko obtains when using his empirical value of √3 for the boundary layer parameter &bgr;. For the testing time in the turbulent case, the results differ somewhat from Anderson's.

ISSN:0031-9171    

DOI:10.1063/1.1711205

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

Condensation of water vapor in a highly supersaturated state was studied with steady flow of moist air in supersonic nozzles of different temperature gradients. With measured centerline static pressures, known initial conditions, and known nozzle geometry, the equations of motion could be solved. From these results heat addition to the flow owing to condensation could be determined. By estimating latent heats, condensate mass fractions and condensation rates have been found. It was inferred that at temperatures from 200 to 220°K the condensate was ice. Classical steady‐state nucleation theories in conjunction with a droplet growth law were applied to solutions of the condensation integral equation. It was found that on this basis the onset of measurable condensation cannot be predicted from first principles. In a qualitative manner, however, the observations could be correlated with the theory. A contributing factor to the failure of nucleation theory is the lack of knowledge of material properties at the low temperatures in question. In conclusion, new work based on the findings of the conditions at the onset of condensation is suggested.

ISSN:0031-9171    

DOI:10.1063/1.1711206

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

The results of a study of fluid mechanics of a large linear magnetohydrodynamic generator with a field strength of 33 000G are presented. The experiment was designed to fulfill three requirements; predominant Lorenz force, important Hall effects, and substantial changes in the electrical and thermodynamic properties of the gas.Studies of the electrical properties of the fluid of the effects of the surface temperature and geometry of the electrodes are described. The performance of the generator is analyzed under varying conditions of mass flow, magnetic field, seed concentration, exhaust pressure and channel geometry. Finally a comparison between a simple theory and the experimental results shows good agreement, indicating the feasibility of predicting magnetohydrodynamic generator performance.

ISSN:0031-9171    

DOI:10.1063/1.1711207

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

The attenuation of ultrasonic waves in liquid sodium and potassium due to an external, de magnetic field has been measured between 2.25 and 40 MHz. The experimental results have agreed with the theoretical expression within experimental error, indicating a coupling of acoustic and hydromagnetic modes at low frequencies.

ISSN:0031-9171    

DOI:10.1063/1.1711208

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

According to Becker and Henkes, relatively fast molecular beams of heavy gases can be produced by having a mixture of the heavy gas and a light acceleration gas expand out of a nozzle and transferring the core of the nozzle flow into high vacuum. By mass spectrometric analysis of the collected beam, the degree of enrichment of the heavy gas is investigated for different argon‐hydrogen mixtures and for different inlet pressures. The particle flow density of the molecular beam is obtained by measurement of the pressure head. The acceleration of argon is investigated by a time‐of‐flight method. For an initial mixture of 1% Ar and 99% H2, the system yields a maximum of 40% for the argon mole fraction in the beam at an inlet pressure of 2 atm. The corresponding flow density is 1.3 × 1017Ar atoms per cm2per sec. at a distance of 60 mm from the nozzle; the beam velocity is 2100 m/sec corresponding to a kinetic energy of the argon atoms of about 1 eV.

ISSN:0031-9171    

DOI:10.1063/1.1711209

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

The collisionless expansions of spherical and cylindrical gas clouds into an ambient gas are investigated. General expressions for the higher moments are derived and evaluated. The solutions exhibit effects not apparent in previous work on collisionless expansions bounded by vacuum. Mass flow, temperature and velocity exhibit propagating maxima which decay in amplitude and diffuse with time. Time constants for the duration of the expansions are obtained as a rough criterion for possibility of shock formation. Comparisons are made with the Euler solution and a short time collisional solution obtained by numerical integration of the Boltzmann equation with a model collision term.

ISSN:0031-9171    

DOI:10.1063/1.1711210

出版商:AIP    

年代:1964

数据来源: AIP