摘要:

Photography of tiny oil drop tracers carried by air flowing in a rectangular pipe has been used to measure the fluid velocity at various distances from the wall. Measuring accuracy of better than±0.5% over most of the profile yields agreement with the predicted parabolic profile. The measurements are carried out in an all‐glass section of pipe of cross section 9.5 × 102 mm; the pipe flow Reynolds number is 15, and the duration of the measurement is 0.2 sec.

ISSN:0031-9171    

DOI:10.1063/1.1762033

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

An asymptotic expansion of the Navier—Stokes equations is proposed which provides a new basis for previously stated free‐vortex equations. Two main parameters emerge from the description of vortex generation. One is a conventional Ekman number, and the other indicates that unless the product of the area of the updraft and the average vertical gradient of the vertical velocity greatly exceeds the kinematic viscosity coefficient, no localized vortical flow develops. Although the model is largely axially invariant, the isobars described by the model are easily shown to have a funnel‐cloud‐like shape. Finally it is proposed that the analysis (although laminar) may suggest the counterforces basic to the generation of concentrated geophysical vortices: a vertical updraft induces a radial inflow, which may concentrate ambient angular momentum into a vortex unless turbulent viscous forces counteract the intensification.

ISSN:0031-9171    

DOI:10.1063/1.1762034

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The problem of steady incompressible laminar flow of elasticoviscous liquids through a cylindrical annulus in the presence of suction and injection is considered. The rate of suction at one wall is taken to be equal to the rate of injection at the other wall of the annulus. Perturbation method is used for the axial velocity regardingS = R Rcas the perturbation parameter. For rapid convergence of the series solution,Sis taken to be equal to 0.1. The effects of cross‐flow Reynolds numberRand elastic numberRcon the components of velocity and the pressure fields are shown graphically.

ISSN:0031-9171    

DOI:10.1063/1.1762035

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

Nonequilibrium channel flow is analyzed for an arbitrary mixture of monatomic and diatomic gases with the assumption that the chemical and vibrational rate processes are not coupled. A new numerical formulation permits precise evaluation of the chemical and physical properties of the mixture in all regions of the flow. The special case of high enthalpy airflow in a hypersonic nozzle is examined, and a comparison is made with earlier results which use approximate equations in the near‐equilibrium region of the flow. The comparison shows that when chemical rates are accurately known in this region, the description of the chemical nature of the flow in downstream regions is altered.

ISSN:0031-9171    

DOI:10.1063/1.1762036

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A thermodynamic calculation of the change in superfluid velocity with temperature is described. It is shown that (a) thermodynamics is compatible with a temperature‐independent hydrodynamical criterion for superfluid flow, and (b) only discrete changes of superfluid velocities with the angular velocity of the container are consistent with thermodynamic equilibrium.

ISSN:0031-9171    

DOI:10.1063/1.1762037

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

An experiment is described in which a spatially periodic, time‐invariant electric field is used to create a spatially periodic cellular flow by the action of an electric shear stress in the region of a fluid‐fluid interface. The cellular motion is closely related to large‐amplitude interfacial deformations observed when an electric field stresses the interface between two fluids having nearly the same electrical conductivity. A simple theoretical model is developed for the cell streamlines, flow velocity, and distribution of electric potential, and this model is shown to be in agreement with the experimental observations.

ISSN:0031-9171    

DOI:10.1063/1.1762038

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A generalized eddy viscosity function &sgr;, is introduced in order that the Reynolds stress in an incompressible fluid be expressible as a linear combination of the Kronecker and rate‐of‐strain tensors. A transport equation for the eddy viscosity is derived from the general turbulence energy equation, thereby introducing two additional functions, the specific turbulence kinetic energyq, and a scale variables.To determine the three variables, a transport equation forsis postulated, and a modified Prandtl—Wieghardt relation among the three variables is accepted. The theory is expressed in universal, invariant form, and validity is demonstrated by application to several problems.

ISSN:0031-9171    

DOI:10.1063/1.1762039

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A linear theory of mechanical equilibrium of liquid crystals of the nematic type is developed and several solutions are given which illustrate the kind of effects predicted by the theory.

ISSN:0031-9171    

DOI:10.1063/1.1762040

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The influence of a transverse magnetic field on the Kapitza capillary wave traveling down the surface of a falling, conducting liquid film is investigated. It is shown that, for small magnetic Reynolds numbers the range of admissible dimensionless celerity becomes narrower as the Hartmann number increases. When the Hartmann number reaches 4.63 there is but one single admissible wave celerity (1.43). With still stronger field strength, a traveling wave is no longer possible within the linear scheme employed.

ISSN:0031-9171    

DOI:10.1063/1.1762041

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

Measurements of the mean velocity profiles of a free turbulent mercury jet in the presence of an axial magnetic field, with Reynolds numbers between 1 × 103and 6 × 103are reported. The Hartmann number, based on nozzle conditions, varied from zero to 40. It is found that the eddy viscosity divided by the square root of the kinematic momentum has a sharp maxima as a function of (Reynolds number)−1. A simple model which is consistent with the data is developed. The model suggests that, (1) the jet, although self similar, has a rate of energy dissipation which depends on phenomena occurring at the nozzle. (2) the maxima in eddy viscosity are caused by the excitation of a helical instability near the nozzle.

ISSN:0031-9171    

DOI:10.1063/1.1762042

出版商:AIP    

年代:1967

数据来源: AIP