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COHERENT MOTIONS IN TURBULENT FLOWS THROUGH CURVED PIPES

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Turbulent flow in curved pipes occurs in a variety of industrial applications such as heat exchangers, nuclear reactors and components of internal combustion engines (e.g. exhaust manifolds), and has attracted the interest of the fluid-dynamics community both from a fundamental and an applied point of view. One of the main characteristics of this flow case is the imbalance between the cross-stream pressure gradient and the centrifugal force induced from the bend which causes a secondary motion in the form of a pair of counter-rotating vortices, so-called Dean vortices. The observable turbulent structures are pushed towards the outer side of the curved pipe due to the centrifugal force, correspondingly the turbulence on the inner side is highly reduced. Moreover, Dean vortices may reorganise the near-wall turbulence and yield a more complex system compared to the straight pipe configuration. In the present work, direct numerical simulations (DNS) are combined –for the first time– with experiments in order to obtain a proper understanding of the coherent motions and large-scale structure dynamics of the turbulent flow in a curved pipe.

Author(s):

Philipp Schlatter    
KTH Mechanics
Sweden

Azad Noorani    
KTH Mechanics
Sweden

Athanasia Kalpakli    
KTH Mechanics
Sweden

Ramis Örlü    
KTH Mechanics
Sweden