UCL logo

UCL Discovery

UCL home » Library Services » Electronic resources » UCL Discovery

On the global instability of free disturbances with a time-dependent nonlinear viscous critical layer

Gajjar, J; Smith, FT; (1985) On the global instability of free disturbances with a time-dependent nonlinear viscous critical layer. Journal of Fluid Mechanics , 157 pp. 53-77. 10.1017/S0022112085002300.

Full text not available from this repository.

Abstract

A theoretical study is made of the global nonlinear growth or decay, in space and time, of an unsteady non-neutral disturbance/wavepacket when a time-dependent nonlinear viscous critical layer is present. The basic flow considered is a steady quasiparallel channel flow, boundary layer or liquid-layer flow at high Reynolds number. The unsteadiness with regard to the critical layer shows itself less in the internal dynamics than in the relatively slow movement of the layer across the flow, the temporal and spatial rate of movement discussed being sufficient to affect the nonlinear viscous balance in the layer. This greatly reduces the mean-flow distortions produced. The disturbance amplitude, in contrast, responds nonlinearly on faster time- and space-scales, both inside and outside the critical layer. These slower- and faster-scale properties inside the critical layer and outside, i.e. globally, are coupled together in general. The work addresses first the structure and nonlinear evolution equations for the growing or decaying free disturbance and the critical layer. But preliminary analysis in special cases suggests, among other things, the significant result that previous nonlinear studies based on quasineutral assumptions give unstable subcritical threshold amplitudes, above which increasingly fast disturbance growth takes place globally. © 1985, Cambridge University Press. All rights reserved.

Type: Article
Title: On the global instability of free disturbances with a time-dependent nonlinear viscous critical layer
DOI: 10.1017/S0022112085002300
UCL classification: UCL > School of BEAMS
UCL > School of BEAMS > Faculty of Maths and Physical Sciences
URI: http://discovery.ucl.ac.uk/id/eprint/1551307
Downloads since deposit
0Downloads
Download activity - last month
Download activity - last 12 months
Downloads by country - last 12 months

Archive Staff Only

View Item View Item