On the periodic gas motions

Two-dimensional periodic gas motions are considered that are described by a class of the rotational and rotational-symmetric exact solutions of gas dynamics equations. The study is based on construction of the first integrals and a lemma about existence of periodic functions defined by the special-type quadratures. The concept is introduced of limit relationships enabling to find approximate connections between entering parameters and giving a qualitative knowledge about the form of studied periodic gas motion.