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A massively parallel hybrid scheme for direct numerical simulation of turbulent viscoelastic channel flow. (English) Zbl 1452.76075
Summary: This paper describes in detail a numerical scheme designed for direct numerical simulation (DNS) of turbulent drag reduction. The hybrid spatial scheme includes Fourier spectral accuracy in two directions and sixth-order compact finite differences for first and second-order wall-normal derivatives, while time marching can be up to fourth-order accurate. High-resolution and high-drag reduction viscoelastic DNS are made possible through domain decomposition with a two-dimensional MPI Cartesian grid alternatively splitting two directions of space (‘pencil’ decomposition). The resulting algorithm has been shown to scale properly up to 16384 cores on the Blue Gene/P at IDRIS-CNRS, France.
Drag reduction is modeled for the three-dimensional wall-bounded channel flow of a FENE-P dilute polymer solution which mimics injection of heavy-weight flexible polymers in a Newtonian solvent. We present results for four high-drag reduction viscoelastic flows with friction Reynolds numbers $$Re_{\tau 0} = 180, 395, 590$$ and 1000, all of them sharing the same friction Weissenberg number $$We_{\tau 0} = 115$$ and the same rheological parameters. A primary analysis of the DNS database indicates that turbulence modification by the presence of polymers is Reynolds-number dependent. This translates into a smaller percent drag reduction with increasing Reynolds number, from 64% at $$Re_{\tau 0} = 180$$ down to 59% at $$Re_{\tau 0} = 1000$$, and a steeper mean current at small Reynolds number. The Reynolds number dependence is also visible in second-order statistics and in the vortex structures visualized with iso-surfaces of the $$Q$$-criterion.

MSC:
 76F65 Direct numerical and large eddy simulation of turbulence 76A10 Viscoelastic fluids 65Y05 Parallel numerical computation 82D60 Statistical mechanical studies of polymers
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