Friday, 14. December 2018

Decay and amplification of turbulence in oscillatory pipe flow

Many industrial and physiological flow problems are characterized by reciprocating fluid motions bounded by cylindrical walls of tubes or branching pipe systems. Respiratory airflow (oscillatory) and vascular blood flow (pulsatile) are usually laminar, since the shear forces acting on the physiological system ought to be small. On the other hand, in combustion engines or other thermal/chemical process devices involving a reciprocating piston, turbulence might enhance or even control mixing processes as well as mass and heat transfer.
Within this project, we perform direct numerical simulations (DNS) of oscillatory pipe flow by using a high-order finite-volume method to solve the incompressible Navier-Stokes equations. Our DNS cover a wide range of Womersley (Wo) numbers and high Reynolds (Re) numbers, where Wo and Re form the set of non-dimensional parameters characterising the oscillatory pipe flow. Starting from fully-developed turbulent or disturbed laminar velocity fields, the oscillatory flows either relaminarise or reach different conditionally or fully turbulent states, strongly depending on the combination of Wo and Re. Analysing the DNS data, we focus on the decay and amplification of shear- flow turbulence in pipe flows during the oscillatory cycle and its impact on frictional losses, transport properties and mixing efficiency.


Colour encoded contour plots of the azimuthal (left) and the axial (right) velocity components in a longitudinal and a cross-sectional plane obtained by DNS of an oscillatory pipe flow at Wo = 13 and Re = 12 000.


D. Feldmann & C. Wagner: Direct numerical simulation of fully-developed turbulent and oscillatory pipe flows at
Reτ = 1440; Journal of Turburlence, Vol. 13 N32, p. 1-28, 2012 



Prof. Dr. Claus Wagner
German Aerospace Center (DLR)
Institute of Aerodynamics and Flow Technology, Department Ground Vehicles
Phone: +49 551 709-2261


German Aerospace Center (DLR), Institute of Aerodynamics and Flow Technology, SCART
Bunsenstraße 10, 37075 Göttingen, Germany