  We investigate the shock-induced turbulent mixing between a light and heavy
gas, where a Richtmyer-Meshkov instability (RMI) is initiated by a $\Ma = 1.5$
shock wave. The prescribed initial conditions define a deterministic multimode
interface perturbation between the gases, which can be imposed exactly for
different simulation codes and resolutions to allow for quantitative
comparison. Well-resolved large-eddy simulations are performed using two
different and independently developed numerical methods with the objective of
assessing turbulence structures, prediction uncertainties and convergence
behaviour. The two numerical methods differ fundamentally with respect to the
employed subgrid-scale regularisation, each representing state-of-the-art
approaches to RMI. Unlike previous studies the focus of the present
investigation is to quantify uncertainties introduced by the numerical method,
as there is strong evidence that subgrid-scale regularisation and truncation
errors may have a significant effect on the linear and non-linear stages of the
RMI evolution. Fourier diagnostics reveal that the larger energy containing
scales converge rapidly with increasing mesh resolution and thus are in
excellent agreement for the two numerical methods. Spectra of gradient
dependent quantities, such as enstrophy and scalar dissipation rate, show
stronger dependencies on the small-scale flow field structures in consequence
of truncation error effects, which for one numerical method are dominantly
dissipative and for the other dominantly dispersive.
