Drag of turbulent flows over rough surfaces

Duration: 33 mins 19 secs

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Description:	Bettina Frohnapfel (Karlsruhe Institute of Technology (KIT)) 31/03/2022 Programme: TURW04 SemId: 35351


Created:	2022-04-06 22:48
Collection:	Mathematical aspects of turbulence: where do we stand?
Publisher:	Bettina Frohnapfel
Copyright:	Isaac Newton Institute
Language:	eng (English)


Abstract:	Rough surfaces occur widely in engineering and nature. Typically, these surfaces do not influence the drag (flow resistance) for laminar flows. However, under turbulent flow conditions the drag experienced by a rough surface can significantly exceed the one of smooth surfaces. From an engineering perspective, this drag increase due to surface roughness needs to be predicted since it determines energy expenditure and thus also related emissions. The existing predictive tools still carry a relatively large uncertainty with the biggest challenge stemming from the fact that the drag of a rough surface can presently not reliably be predicted by surface properties. A lot of ongoing research efforts are dedicated to improving the link between geometrical surface properties and the effective fluid drag. An additional challenge are inhomogeneous rough surfaces in which different roughness properties are found in different locations of a rough surface. This talk addresses in particular the drag properties of surfaces with spanwise variations of the surface properties.

Abstract:

Rough surfaces occur widely in engineering and nature. Typically, these surfaces do not influence the drag (flow resistance) for laminar flows. However, under turbulent flow conditions the drag experienced by a rough surface can significantly exceed the one of smooth surfaces. From an engineering perspective, this drag increase due to surface roughness needs to be predicted since it determines energy expenditure and thus also related emissions. The existing predictive tools still carry a relatively large uncertainty with the biggest challenge stemming from the fact that the drag of a rough surface can presently not reliably be predicted by surface properties. A lot of ongoing research efforts are dedicated to improving the link between geometrical surface properties and the effective fluid drag. An additional challenge are inhomogeneous rough surfaces in which different roughness properties are found in different locations of a rough surface. This talk addresses in particular the drag properties of surfaces with spanwise variations of the surface properties.

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