Stagnation points on vortex lines in flows of an ideal gas

In this paper, using the Euler equations, we investigate stationary vortex flows of an ideal gas. We consider flows in which either entropy or total enthalpy is constant. For both types of flows, we prove that if on a certain segment of the vortex line the vorticity does not turn to zero. Then the value of the fluid velocity in this segment is either identically equal to zero or nonzero at all points of the segment of the vortex line. Using this result, a new (simpler) proof of the well-known property is given. This property implies that in the general spatial case of a stationary flow around a body with a smooth convex bow, the vorticity at the stagnation point is equal to zero.