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Direct numerical simulations have proven of inestimable help to ourunderstanding of the transition to turbulence in wall-bounded flows. While thedynamics of the transition from laminar flow to turbulence via localised spotscan be investigated with reasonable computing resources in domains of limitedextent, the study of the decay of turbulence in conditions approaching those inthe laboratory requires consideration of domains so wide as to exclude therecourse to fully resolved simulations. Using Gibson's C++ code ChannelFlow, wescrutinize the effects of a controlled lowering of the numerical resolution onthe decay of turbulence in plane Couette flow at a quantitative level. We showthat the number of Chebyshev polynomials describing the cross-stream dependencecan be drastically decreased while preserving all the qualitative features ofthe solution. In particular, the oblique turbulent band regime experimentallyobserved in the upper part of the transitional range is extremely robust. Interms of Reynolds numbers, the resolution lowering is seen to yield a regulardownward shift of the upper and lower thresholds Rt and Rg where the bandsappear and break down. The study is illustrated with the results of twopreliminary experiments.

On modelling transitional turbulent flows using under-resolved direct numerical simulations: The case of plane Couette flow