Abstracts - KTH Mechanics

Numerical study of turbulence in a rotating pipe using Large
Eddy Simulation
J. Revstedt ∗ , C. Duwig ∗ ,L.Fuchs ∗
Today, many industrial devices are making use of swirling flows. The main advantages
of adding swirl to, for example, a jet is to increase turbulence and mixing.
Modeling and understanding the swirling flows is then a key issue. However, despite
of more than 40 years of research, the mechanisms of vortex break down are only
partially understood. The main difficulty of the problem is the unsteady behavior of
this type of flow 1 : Large structures resulting from vortex breakdown and the swirling
shear-layers, affect directly the flow.
In the present work, we consider an infinitely long rotating pipe. The rotation adds
some swirl to the turbulent jet flow. Additional tangential shear is also added. It
modifies the mean velocity profiles as well as the characteristic of turbulence. The
present study aims to capture the large structures in a rotating pipe flow and understand
how they are affected by swirl and Reynolds number.We use performed at
three Reynolds numbers (Re =12000, 24000, 36000) and at three rotational speeds
(S= 0.2, 0.5, 1.0). The influence of these parameters on the mean velocity and mean
turbulent stress fields is investigated. In addition vortex tubes visualization will be
presented and turbulent energy spectra will be analyzed. Mean velocities and stresses
are compared also to the experimental data 2 . LES captures well the shear-layers and
the ‘smoothing’ effect of turbulence. Strong vortex tubes are visualized using the λ2
technique. Figure 1 shows the instantaneous vortex stuctures using this technique.
∗Energy Sciences/Fluid Mechanics, Faculty of Engineering, Lund University, P.O. Box 118, SE-
221 00 Lund, Sweden
1Lucca-Negro and O’Doherty, Progress in Energy and Combustion Science 27, 431 (2001).
2Facciolo, TRITA-MEK Tech. Rep. 2003:15 KTH, Stockholm (2003).
Figure 1: Visualization of the vortex tubes using the λ2 technique. Re = 36000,
S =1.0
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