The maximum sustainable heat flux in stably stratified channel flows

J. Donda, I. van Hooijdonk, A.F. Moene, G.J.F. van Heijst, H. Clercx, B. van de Wiel

Research output: Contribution to conferenceAbstractAcademic

Abstract

In analogy to the nocturnal atmospheric boundary layer a flux-driven, cooled channel flow is studied using Direct Numerical Simulations. Here, in particular, the mechanism behind the collapse of turbulence at large cooling rates is analysed. In agreement with earlier studies, the flow laminarizes at strong cooling rates. The mechanism for the cessation of turbulence is understood from a Maximum Sustainable Heat Flux (MSHF) theory, which is here tested against numerical 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 determined 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 field observations.
Original languageEnglish
Publication statusPublished - 2015
EventEGU General Assembly 2015 - Vienna, Austria
Duration: 12 Apr 201517 Apr 2015

Conference

ConferenceEGU General Assembly 2015
CountryAustria
CityVienna
Period12/04/1517/04/15

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    Donda, J., van Hooijdonk, I., Moene, A. F., van Heijst, G. J. F., Clercx, H., & van de Wiel, B. (2015). The maximum sustainable heat flux in stably stratified channel flows. Abstract from EGU General Assembly 2015, Vienna, Austria. http://meetingorganizer.copernicus.org/EGU2015/EGU2015-3861.pdf