On 'spurious' eddies

D. Drikakis, L. G. Margolin, P. K. Smolarkiewicz

Research output: Contribution to journalArticlepeer-review


Recently, several papers have appeared in the CFD literature, proposing an idealized instability problem as a benchmark for discriminating among numerical algorithms for two-dimensional Navier-Stokes flows. The problem is a double shear layer simulated at coarse resolution and with a prescribed interface perturbation. A variety of second-order accurate schemes have been tested, with all results falling into one of two solution patterns-one pattern with two eddies and the other with three eddies. In the literature, there is no fast-and-firm rule to predict the results of any particular algorithm. However, it is asserted that the two-eddy solution is correct. Our own research has led to two conclusions. First, the appearance of the third eddy is tied up with small details of the truncation error; we illustrate this point by prescribing small changes that lead to reversal of the appearance/disappearance of the third eddy in several schemes. Second, we discuss the realizability of the two solutions and suggest that the three-eddy solution is the more physical. Overall, we conclude that this problem is a poor choice of benchmark to discriminate among numerical algorithms.

Original languageEnglish
Pages (from-to)313-322
Number of pages10
JournalInternational Journal for Numerical Methods in Fluids
Issue number1-2
Publication statusPublished - 10 Sept 2002


  • High-resolution methods
  • Unsteady flows
  • Vortices


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