The flow field and mixing in an expansion-ramp geometry is studied using large-eddy
simulation (LES) with subgrid scale (SGS) modelling. The expansion-ramp geometry
was developed to investigate enhanced mixing and flameholding characteristics while
maintaining low total-pressure losses. Passive mixing was considered without taking
into account the effects of chemical reactions and heat release, an approximation
that is adequate for experiments conducted in parallel. The primary objective
of the current work is to validate the LES–SGS closure in the case of passive
turbulent mixing in a complex configuration and, if successful, to rely on numerical
simulation results for flow details unavailable via experiment. Total (resolved-scale
plus subgrid contribution) probability density functions (p.d.f.s) of the mixture fraction
are estimated using a presumed beta-distribution model for the subgrid field. Flow
and mixing statistics are in good agreement with the experimental measurements,
indicating that the mixing on a molecular scale is correctly predicted by the LES–
SGS model. Finally, statistics are shown to be resolution-independent by computing
the flow for three resolutions, at twice and four times the resolution of the coarsest
simulation