Furthermore, if the entropy of the flow remains as a constant, we can have the isentropic Euler system, and if the flow is assumed to be irrotational, we can have the potential flow equation.

• 如果再假设流体的熵保持为常数，那么我们进一步 得到等熵的欧拉方程组；如果再假设流体的速度场满足无旋条件，我们可以得到所谓的位势流方程组。