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811.
Lung-an Ying 《计算数学(英文版)》1999,17(1):73-88
1.IntroductionDifferentkindsoffractionalstepmethodshavebeenappliedtosolvetheinitialboundaryvalueproblemsoftheNavier--Stokesequationsforviscousincompressibleflow.Thevortexmethoddevelopedin[5]byChorinisaschemewiththreeintermediatestepswheretheeffectsofconvectionandviscosityareseparated,andvortexsheetsarecreatedalongtheboundary.Asetofvortexblobsisintroducedtoapproximatethevorticityfield.Thesevortexblobsmovealongtheparticletrajectoriesintheconvectionstep,andtheymoverandomlyinthediffusionstep.The… 相似文献
812.
We investigate the stability of a quantized vortex in a weakly interacting Bose gas, trapped in a toroidal container with hard walls. Calculating the excitation spectrum numerically and determining the stability condition by the Landau criterion, we examine the effect of reducing the confinement region of the condensate on the vortex stability. We find that tight confinement of the condensate increases the stabilization of the quantized vortex because an increase in the zero sound velocity due to tight confinement prevents the emergence of the elementary excitation which breaks superfluidity of the Bose system. We also discuss the experimental setup to observe such an effect. 相似文献
813.
A. Lemaire K. Zhringer T.R. Meyer J.C. Rolon 《Proceedings of the Combustion Institute》2005,30(1):475-483
In highly fluctuating flows, it happens that high values of the strain-rate do not induce extinction of the flame front. Unsteady effects minimize the flame response to rapidly varying strain fields. In the present study, the effects of time-dependent flows on non-premixed flames are investigated during flame/vortex interactions. Gaseous flames and spray flames in the external sheath combustion regime are considered. To analyse the flame/vortex interaction process, the velocity field and the flame geometry are simultaneously determined using particle imaging velocimetry and laser-induced fluorescence of the CH radical. The influence of vortex flows on the extinction limits for different vortex parameters and for different gaseous and two-phase flames is examined. If the external perturbation is applied over an extended period of time, the extinction strain-rate is that corresponding to the steady-state flame, and this critical value mainly depends on the fuel and oxidizer compositions and the injection temperature. If the external perturbation is applied during a short period of time, extinction occurs at strain-rates above the steady-state extinction strain-rate. This deviation appears for flow fluctuation timescales below steady flame diffusion timescales. This behaviour is induced by diffusive processes, limiting the ability of the flame to respond to highly fluctuating flows. With respect to unsteady effects, the spray flames investigated in this article behave essentially like gaseous flames, because evaporation takes place in a thin layer before the flame front. Extinction limits are only slightly modified by the spray, controlling process being the competition between aerodynamic and diffusive timescales. 相似文献
814.