摘要:

A theory of the electrohydrodynamic induction pump is described which includes charge convection, inhomogeneous fluid properties caused by temperature gradients, and harmonics in the electric traveling wave. The case of stable laminar flow in a wide reentrant rectangular channel is presented as an examle. Results are more realistic than earlier models. A limiting synchronous speed appears, as in magnetic induction devices. Velocity profiles become flatter than a parabolic profile as operating conditions of practical significance are reached.

ISSN:0031-9171    

DOI:10.1063/1.864623

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A numerical simulation of the final stages of transition in plane chnnel flow is presented. Investigation of various flow field quantities provides some new insight into the breakdown stage and the formation of spot‐like packets of turbulence.

ISSN:0031-9171    

DOI:10.1063/1.864624

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A system of Lorenz‐type equations is derived for the axisymmetric Taylor–Couette flow problem. It is found there is typically no Hopf bifurcation as the Reynolds number increases beyond the transition Reynolds number.

ISSN:0031-9171    

DOI:10.1063/1.864625

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

The study of ambipolar electrostatic confinement of central cell ions requires equilibrium models in which the electrostatic forces are treated on an equal footing with the magnetostatic ones. The three‐dimensional guiding center fluid equilibrium model has been generalized to include these ambipolar effects; quasineutrality is used to obtain the potential &fgr;. There is no restriction to low‐beta or long‐thin approximations. In this multiregion, multicomponent model omnigenity is required for each species seprately; this is the less stringent requirement of multigenity.

ISSN:0031-9171    

DOI:10.1063/1.864626

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

It is shown theoretically that long‐wavelength, rf fields in the ion cyclotron frequency range can stabilize low‐frequency, electrostatic interchange modes. Stabilization does not require specified gradients in the spatial distribution of rf energy. This offers an appealing alternative to ponderomotive stabilization of curvature driven modes, and may help explain recent observations on the Phaedrus tandem mirror experiment.

ISSN:0031-9171    

DOI:10.1063/1.864627

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

Previous work [Yu, Shukla, and Tsintsadze, Phys. Fluids25, 1049 (1982)] on intense laser pulse propagation in plasmas is generalized to include nonlinear ion motion which can be of importance in the slow plasma response.

ISSN:0031-9171    

DOI:10.1063/1.864628

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

The first observation of microwave generation at the sixth harmonic of the electron cyclotron frequency using a 17 kV, 0.6–1.0 A, 3 &mgr;sec electron beam is reported. This device, which is called a cusptron, produces radiation from the resonant interaction of a nonrelativistic rotating electron beam and a magnetron‐type conducting boundary with six vanes by the negative mass instability. The observed radiated power is approximately 500 W at 4.38 GHz.

ISSN:0031-9171    

DOI:10.1063/1.864629

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

The linearized spatial stability of adiabatic flat plate flow to the first mode of oblique disturbances is computed numerically, using finite difference techniques, in the Mach number range M=1.6 to 6.0. The most unstable wave angle &psgr; is found in the range &psgr;=46° to 60°. Stability maps, in the form of curves of constant spatial amplification rate, are presented on the frequency‐Reynolds number diagram. The criticalx‐Reynolds number is found to decrease monotonically with M, and is best fit with the expression R1/2x=579.34M−1.18. This decrease is found to correspond with the outward displacement of the minimum critical layer and the ‘‘inflection’’ point,yat (U′/T)′=0, fromy=0.248 and 0.231 at M=1.6 to 0.754 and 0.842 at M=6.0. No transition from viscous to inviscid instability is found with increasing Mach number, rather viscous instability persists to M=6.0. Some of the results agree with those obtained earlier by Mack, but others differ, particularly computations for M>3.0.

ISSN:0031-9171    

DOI:10.1063/1.864630

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

Past work on the influence of Mach number on the viscous and inviscid instability of flat‐plate boundary layers is reviewed, and new spatial calculations are presented. These calculations support the previous view that viscosity is only stabilizing for both two‐ and three‐dimensional first‐mode waves aboveM1=3.0, and for second‐mode waves at all Mach numbers. It is concluded that the calculations of Wazzan, Taghavi, and Keltner that show viscous instability atM1=6.0 for first‐mode 50° waves, and atM1=3.0 for two‐dimensional second‐mode waves, are not correct.

ISSN:0031-9171    

DOI:10.1063/1.864631

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

Laser‐Doppler anemometry is applied to study the dynamics of small‐diameter carbon dioxide and air bubbles rising in a quiescent liquid. Primary data include bubble velocity and diameter as functions of position above a generating nozzle. Direct observation of decreasing bubble diameter provides instantaneous mass transfer results for carbon dioxide bubbles, presented in terms of Sherwood versus Reynolds and Peclet numbers. The range of velocity measured is 1.0 to 35.0 cm/sec, and the range of diameter measured is 0.07 to 1.20 mm, corresponding to a Reynolds number range from less than unity to over 500. Bubble oscillations, observed through direct diameter measurements, are recorded for bubbles with initial diameter greater than 0.80 mm. Fourier transforms of the instantaneous diameter profiles result in a frequency of oscillation of about 10 Hz for most test runs. Drag studies indicate that bubbles with Reynolds number greater than 40 follow correlations developed for fluid spheres with attached boundary layers and wakes. Transition from solid‐sphere to fluid‐sphere drag behavior is observed for increasing Reynolds number in the range 10 to 40.

ISSN:0031-9171    

DOI:10.1063/1.864619

出版商:AIP    

年代:1984

数据来源: AIP