A comparison of single-time relaxation lattice Boltzmann schemes with enhanced stability

In the recent years the entropic version of the lattice Boltzmann method (ELB) has made proof of significantly enhanced numerical stability as compared to the standard single-time relaxation form of the lattice Boltzmann equation. In this paper, we compare ELB with a more empirical procedure, based on the idea of modifying the value of the relaxation time in such a way as to enforce the positivity of the kinetic distribution function (fix-up method). The stability enhancement due to ELB and fix-up are compared for the case a two-dimensional lid-driven cavity flow. It is shown that ELBM offers higher stability at a moderate price in terms of computational overhead. On the other hand, even the simple fix-up procedure can provide significant savings over the standard single-time relaxation method, virtually cost-free in terms of computational requirements.