摘要:

Studies of unexcited and excited elliptic jets reveal their characteristics to be noticeably different from circular jets, suggesting applications of excited elliptic jets for enhanced mixing and chemical reaction, and control of aerodynamic noise. The near‐field turbulence characteristics, jet spread, and locations of switching of major and minor axes of the jet cross section can be drastically altered by forcing. The preferred mode and the stable pairing mode of an elliptic jet scale with the exit equivalent diameter.

ISSN:0031-9171    

DOI:10.1063/1.864062

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

An instability characteristic of a fully developed laminar flow encountering a sudden expansion in a circular pipe is briefly described.

ISSN:0031-9171    

DOI:10.1063/1.864063

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Thek‐&egr; model admits an analytical solution for purely diffusive turbulence. A comparison with available experiments provides an improved measure of the Prandtl number fork, and suggests that turbulence models can profit from more definitive experimental studies of purely diffusive turbulence.

ISSN:0031-9171    

DOI:10.1063/1.864064

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

A set of nonlinear fluid equations which includes the effect of finite ion Larmor radius is derived to describe microturbulence [k⊥ &rgr;s&bartil;O(1),k∥R&bartil;O(1),n1/n0&bartil; &rgr;s/Ln, andB1/B0&bartil;&rgr;s/R] in an inhomogeneous plasma with a strong magnetic field of general geometry. Here &rgr;sis the ion Larmor radius at the electron temperature,Lnis the density gradient scale length,Ris the radius of curvature of the magnetic line of force,kis the wave vector, andn1/n0andB1/B0are relative levels of density and magnetic field perturbations.

ISSN:0031-9171    

DOI:10.1063/1.864065

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Lower‐hybrid waves at two different frequenciesf1andf2are launched simultaneously from two localized antennas, and a third wave is observed to arise near the plasma edge at the frequencyf=f2−f1. This phenomenon can be explained by an echo effect near the plasma surface.

ISSN:0031-9171    

DOI:10.1063/1.864066

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Expressions for the potential difference &Fgr;pbbetween the plug and barrier regions of a tandem‐mirror thermal barrier cell are derived in the limit of strong electron‐cyclotron heating. It is found that &Fgr;pbvaries as the 2/3 power of the ratio of the density of electrostatically trapped plug electrons to the density of thermal electrons at the barrier. Electric‐field requirements for validity of the solutions are presented.

ISSN:0031-9171    

DOI:10.1063/1.864067

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

The relativistic Fokker–Planck equation is solved with electron cyclotron resonance heating (ECRH) in a magnetic mirror for an assumed thermal barrier electrostatic potential profile. Two methods—a finite element technique and a Monte Carlo technique—give nearly the same results. Favorable comparison is made with recently obtained analytical expressions for the relation between axial density ratios and potential profile using parameters expected in the TMX‐U and MFTF‐B experiments.

ISSN:0031-9171    

DOI:10.1063/1.864068

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

One‐dimensional Vlasov simulations show that when an electron beam is suddenly injected into a plasma, a fast‐moving monotonic shock forms during the early stage of the transient plasma response. In the shock, the ions are nearly immobile. The shock appears to be an electrostatic electron‐beam–plasma mode. The shock evolves from an initial positive potential perturbation, which is supported by an ion burst. The steepening of the perturbation into a shock is characterized by an electron‐beam–plasma mode.

ISSN:0031-9171    

DOI:10.1063/1.864043

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Particle‐in‐cell simulations of the beam‐plasma instability confirm that the behavior of the interaction can be described as a wave packet that continually grows in both space and time. A consequence is that the energy deposition length of the instability becomes shorter in time, offering increased potential for this interaction to be used as an inertial fusion driver.

ISSN:0031-9171    

DOI:10.1063/1.864044

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Systems of linear partial differential equations with constant coefficients, like their ordinary differential equation counterparts, can be characterized by the properties of the matrices that form the coefficients of the differential operators. The question arises: Do the matrix operators that result from partial differential equations possess eigenvalues and eigensolutions in the same way that ordinary differential matrix operators do? The answer to this question is explored in some detail using as an example the linearized flow of a viscous fluid. It is shown that eigenfactors do exist for these equations, and that, of necessity, these involve hypercomplex algebra. This fact introduces significant new features to the problem. It is shown that eigenmodes exist and that each of these has its distinctive fundamental singularity. The fluid mechanical significance of these is examined in some detail. In addition, a representative group of other partial differential equations is examined and their eigenmodes and fundamental singularities are determined. It is shown that a number of basic differences exist between the eigenfunction theory for ordinary and for partial differential equations.

ISSN:0031-9171    

DOI:10.1063/1.864045

出版商:AIP    

年代:1983

数据来源: AIP