Gas Dynamics

 

The lecture gas dynamics deals with flows where significant changes in density occur, compressible flows. In the case of air this effect becomes relevant for Mach numbers greater than 0.3.

Within the lecture subsonic and supersonic flows are discussed including shock and expansion waves. The understanding of gas dynamic processes is the basis for different application relevant problems in for example high speed aerodynamics, flows in jet engines, ballistics but also in combustion engines, gas dynamic lasers or even in medicine technology.

First, thermodynamic fundamentals are introduced followed by a discussion of one dimensional stationary flows including the important case of quasi one dimensional nozzle flows. Further, the occurrence of normal and oblique shock waves in supersonic flows is analyzed. In contrast to shock waves which induce a change in entropy and losses respectively, isentropic compressions and expansions are also possible called Prandtl-Meyer flow. The presented theoretical approaches are used in a next step to derive expression for the drag and lift coefficients of simple profiles in supersonic flows.

Next the theory of characteristics is derived on the basis of Crocco’s theorem and the fundamental gas dynamic relation and applied to different supersonic flow problems. In the case of small disturbances the linearized potential theory can be derived for subsonic and supersonic flows from which also the laws of similarity are deduced. Frequent tutorials will help to gain a deeper understanding of the content of the lectures.