Computational fluid dynamics simulations of thermovibrational flows in a square cavity filled with a waterisopropanol mixture has shown that inaccurate density calculations can predict very different flow behaviours. Specifically, comparison has been made between two density calculation models, viz., a weighted-average scheme and the Perturbed Chain Statistical Associating Fluid Theory equation of state. While the latter approach predicts a stronger flow in the cavity due to the convective instabilities that are induced by the large spatial gradients in density, the weighted-average scheme cannot predict this since it does not explicitly depend on the temperature of the mixture. (c) 2012 Canadian Society for Chemical Engineering