The maximum sustainable heat flux in stably stratified channel flows

Judith Donda, Ivo van Hooijdonk, Arnold Moene, Gertjan van Heijst, Herman Clercx, Bas van de Wiel

Research output: Contribution to conferenceConference paper

Abstract

In analogy to the nocturnal atmospheric boundary layer a flux-driven, cooled channel flow is studied using Direct Numerical Simulations (DNS). Here, in particular, the mechanism behind the collapse of turbulence at large cooling rates is analyzed. In agreement with earlier studies, the flow laminarizes at large cooling rates. The mechanism for the cessation of turbulence is understood from a Maximum Sustainable Heat Flux hypothesis, which is here tested against simulations. In stratified flow the maximum heat flux that can be transported downward by turbulence at the onset of cooling is limited to a maximum, which, in turn, is limited by the initial momentum of the flow. If the heat extraction at the surface exceeds this maximum, near-surface stability will rapidly increase, which further hampers efficient vertical heat transport. This positive feedback eventually causes turbulence to be fully suppressed by the intensive density stratification. It is shown that the collapse in the DNS-simulations is successfully predicted by the MSHF-theory. Apart from formal analysis, also a simplified methodology is presented, which is more useful in practice for prediction of regime-transitions in atmospheric field observations.

Original languageEnglish
Publication statusPublished - 1 Jan 2015
Event15th European Turbulence Conference, ETC 2015 - Delf, Netherlands
Duration: 25 Aug 201528 Aug 2015

Conference

Conference15th European Turbulence Conference, ETC 2015
CountryNetherlands
CityDelf
Period25/08/1528/08/15

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    Donda, J., van Hooijdonk, I., Moene, A., van Heijst, G., Clercx, H., & van de Wiel, B. (2015). The maximum sustainable heat flux in stably stratified channel flows. Paper presented at 15th European Turbulence Conference, ETC 2015, Delf, Netherlands.