Drag reduction in heated channels

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalNot applicablepeer-review

9 Scopus Citations
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Author(s)

Detail(s)

Original languageEnglish
Pages (from-to)353-395
Journal / PublicationJournal of Fluid Mechanics
Volume765
Online published23 Jan 2015
Publication statusPublished - 25 Feb 2015
Externally publishedYes

Abstract

It is known that the drag for flows driven by a pressure gradient in heated channels can be reduced below the level found in isothermal channels. This reduction occurs for spatially modulated heating and is associated with the formation of separation bubbles which isolate the main stream from direct contact with the solid wall. It is demonstrated that the use of a proper combination of spatially distributed and spatially uniform heating components results in an increase in the horizontal and vertical temperature gradients which lead to an intensification of convection which, in turn, significantly increases the drag reduction. An excessive increase of the uniform heating leads to breakup of the bubbles and the formation of complex secondary states, resulting in a deterioration of the system performance. This performance may, under certain conditions, still be better than that achieved using only spatially distributed heating. Detailed calculations have been carried out for the Prandtl number Pr = 0.71 and demonstrate that this technique is effective for flows with a Reynolds number Re < 10; faster flows wash away separation bubbles. The question of net gain remains to be settled as it depends on the method used to achieve the desired wall temperature and on the cost of the required energy. The presented results provide a basis for the design of passive flow control techniques utilizing heating patterns as controlling agents.

Research Area(s)

  • drag reduction, flow control

Citation Format(s)

Drag reduction in heated channels. / Floryan, Daniel; Floryan, J. M.

In: Journal of Fluid Mechanics, Vol. 765, 25.02.2015, p. 353-395.

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalNot applicablepeer-review