HPC User Report from K. Nusser (Institute of Process Machinery and Systems Engineering)
Axisymmetric Turbulent Boundary Layers
The convex transverse curvature eﬀects in wall-bounded turbulent ﬂows were analyzed along a streamwise orientated circular cylinder with a large length to diameter ratio. In such ﬂows an axisymmetric turbulent boundary layer (TBL) develops that can deviate from the planar TBL.
Motivation and problem definition
Turbulent ﬂows that evolve over surfaces with a strong curvature normal to the mean ﬂow exhibit TBL that show different behavior than their well-known planar counterparts, like ﬂat plate or channel ﬂow. A classical research case with a strong transverse curvature is the ﬂow along a streamwise orientated circular cylinder with a large length to diameter ratio. In ﬂows
along such geometries an axisymmetric TBL develops that has a thickness much larger than the cylinder radius. In this kind of ﬂow curvature eﬀects become important, yielding to changes in TBL properties, especially on mean velocity proﬁles and turbulent ﬂuctuations, causing higher skin friction coefficients, different characteristics of wall pressure ﬂuctuations and
higher anisotropy in the near-wall ﬂow.
Methods and codes
The open-source code Openfoam (5.0) was selected as simulation platform. Several LES models were utilized to compare differences in the outcome. Among them are the Smagorinsky and One-Equation model with Van-Driest wall damping and the Wall-Adapting Local Eddy-Viscosity (WALE) model. A ﬁnite volume formulation was used with fully orthogonal O-type grid with up to 15 · 106 control volumes.
Resulting mean velocity proﬁles, turbulent ﬂuctuations, skin friction coefficient and TBL thickness are in good agreement with limited literature data. LES models show different results but none deviates signiﬁcant from validation data. Gathered data can now be used as groundwork for further detailed investigations and the clarification of open research questions in connection with convex transverse curvature eﬀects in wall-bounded turbulent ﬂows.
Researcher’s Bio and Affiliation
Katrin Nusser studied Computational Engineering and is now a Ph.D. student in the group of Prof. Dr. Stefan Becker at the Institute of Process Machinery and Systems Engineering.