Thrust and Drag in Supersonic Flow with Heat Addition

Abstract

The concepts of drag and thrust and of their influence on the wake of a body at first were developed for subsonic flow processes only. If we disregard in this context the special case of the induced drag of an airfoil, the drag manifests itself mainly in the wake of the body, where the air flows downstream with a reduced velocity but at practically the ambient pressure p =p _∞ . On the other hand, thrust is obtained if one succeeds to generate increased wake velocities. This concept is derived from the fact that the pressure downstream of the body adjusts very fast to the ambient pressure. With the assumption p = p _∞ one gets from the momentum equation the well known relation for the thrust S

$$S{\text{ }} = {\text{ }}G\left( {w - {w_{\infty }}} \right) $$

((1))

where w _∞ is the approach velocity, w is the downstream velocity, and G means the mass flow per unit of time which experiences a velocity increase of w−w _∞ . The upstream and downstream velocities are assumed to have the same directions. Eq. (1) can be used also as equation for the drag.

Translated by D. Rues from K. Oswatitsch, „Schub und Widerstand bei Wärmezufuhr in Überschallströmung“, Acta Mechanica 3 (1967), 237–247.