Exact solutions to the unsteady equations of perfect gases through Lie group analysis and substitution principles

In this paper. we consider the unsteady equations that govern two- and thre e-dimensional flows of a perfect gas. We explicitly characterize various cl asses of exact solutions by introducing some invertible transformations sug gested by the invariance with respect to Lie groups of point symmetries and using suitable transformations known in literature as substitution princip les. (C) 2001 Elsevier Science Ltd. All rights reserved.