摘要:

The wavelength of steady Taylor vortices established through a sudden start of the inner cylinder has been studied experimentally. The sudden start procedure gives the fluid a choice in the selection of the wavelength. It was found that the preferred wavelength of singly periodic vortices in the steady state after a sudden start is smaller than the critical wavelength, with a minimum at aroundT / Tc = 15. When the Taylor number to which the sudden start was made was increased to around 60Tc, then the preferred wavelength approached the critical wavelength. A wavelength once established through a sudden start did not change its value if afterwards the Taylor number was maintained for a very long time or if the Taylor number was varied over larger intervals, provided the flow was singly periodic. However, this rule does not hold when the critical Taylor number is approached from above with a flow created through a sudden start to a higher Taylor number. In this case the wavelength increases to approach the critical wavelength. Sudden starts to very high Taylor numbers created doubly periodic or turbulent flow with wavelengths larger than the critical wavelength.

ISSN:0031-9171    

DOI:10.1063/1.1694646

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The flow of air between a plate at rest and another one falling onto it either vertically or by folding is studied, and the infrequency of breakage of glass plates colliding in this way is explained. The falling plate may be two‐dimensional, circular, or elliptic, and the results for an elliptic plate give bounds for the motion of a falling rectangular plate.

ISSN:0031-9171    

DOI:10.1063/1.1694647

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The exact solution found previously is applied to rear stagnation‐point flow imposed on solid‐body rotation over a disk. Under normal circumstances, any radial flow reversal which occurs in the boundary layer is suppressed again by the spin up of the fluid outside.

ISSN:0031-9171    

DOI:10.1063/1.1694648

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Laminar natural convection induced in fluids by absorption of energy from a vertical laser beam is analyzed for two different configurations. In the first configuration, the vertical beam propagates in an unconfined fluid, and is modeled as a line source of thermal energy. Ordinary differential equations are obtained by a similarity analysis of the axisymmetric boundary layer equations, and approximate solutions of them are obtained. In the second configuration, the beam propagates in a fluid confined in a tall, isothermal vertical cylinder, and is assumed to have a Gaussian radial distribution of intensity. An exact solution of the Navier‐Stokes and thermal energy equations is obtained for the case of parallel flow. Representative numerical results are presented, and estimates are made of the parametric ranges of validity of the analyses.

ISSN:0031-9171    

DOI:10.1063/1.1694649

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The stability of time‐dependent flows is analyzed by the energy theory. Lower bounds as well as optimal results are obtained for modulated Be´nard and Taylor problems. It is found that the region of certain stability is reduced because of the basic flow modulation.

ISSN:0031-9171    

DOI:10.1063/1.1694650

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Results are presented of temperature measurements made in the slightly heated, plane turbulent wake at stations 400 and 500 diam downstream from a heated cylinder at a Reynolds number of 2800. The results include transverse distributions of the first four moments of the temperature obtained using both conventional and conditional sampling and averaging techniques, the downstream distribution of the root mean square temperature fluctuations on the wake centerline and the probability density function of the temperature. Additionally, there are obtained, as a function of distance from the interface, temperature moments which indicate that there is a definite thermal structure associated with the interface.

ISSN:0031-9171    

DOI:10.1063/1.1694651

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The two familiar functional formalisms in turbulence are applied to the simultaneous turbulent mixing and chemical reaction of scalar fields. One‐step, second‐order, irreversible, exothermic chemical reactions with an Arrhenius‐type rate constant are considered. The problem is formally posed in terms of initial and boundary conditions. For the special case of equal mass‐diffusivities and a Lewis number of one the functional equations are decoupled into a turbulent binary mixing study and a reactive problem. The Lewis‐Kraichnan formalism is used in order to obtain exact functional solutions of the binary mixing case in final period turbulence. Driving forces are included in the thermal energy equation. These solutions are used to obtain detailed information about the binary mixing problem and the behavior of very rapidly reacting species in the final period.

ISSN:0031-9171    

DOI:10.1063/1.1694652

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The determination of the rotational temperature in nitrogen using measurements of electron beam‐induced fluorescence, depends upon the formulation employed to calculate the temperature from the spectral data as well as upon the resolution of the spectrometer. The errors introduced in the measurements by the use of the prevalent forced semilogarithmic data analysis and by incomplete resolution of the rotational lines are examined and evaluated. An alternative method of data analysis is presented. When the errors are accounted for, the dependence of the measured temperature on the number of rotational lines used in the analysis is eliminated, and the apparent rotational temperature becomes less dependent upon the gas density and the true gas temperature.

ISSN:0031-9171    

DOI:10.1063/1.1694653

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A simple formalism yields a general expression for the enhanced induced emission in plasma influenced by a strong electromagnetic or electrostatic pump. Applications to subcritical Brillouin, Raman, and other resonant and nonresonant interactions are given.

ISSN:0031-9171    

DOI:10.1063/1.1694654

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The nonlinear propagation of an arbitrarily polarized electromagnetic wave in a uniform plasma is studied. It is shown that nonlinear effects cause precession of the polarization ellipse as the wave propagates. The ellipticity remains constant, but the orientation of the principal axes is rotated relative to its initial value. A relativistic Vlasov model is used to study nonlinear frequency shifts as well as self‐precession, in a plasma of arbitrary temperature. Even whenT3 ≫ mec2, the qualitative nature of these two processes remains unchanged, although their dependence on the plasma density is altered in significant ways. Implications of these effects for plasma instabilities driven by strong electromagnetic waves are briefly discussed.

ISSN:0031-9171    

DOI:10.1063/1.1694655

出版商:AIP    

年代:1974

数据来源: AIP