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98.4F November 15, 2000 04:32

Are characteristics shock waves?
When analysing flow through a supersonic nozzle we draw the characteristics which are at an angle to the streamlines. Are these characteristics nothing but shock waves?

Thank you

Nishikawa November 16, 2000 05:16

Re: Are characteristics shock waves?
No, they are not. A shock forms where the characteristics (from the same family) collide one another.

A. Taurchini November 16, 2000 09:01

Re: Are characteristics shock waves?
Characterstics are structure along which perturbation propagate (expansion, compression or contact discontinuity). Moreover it's not said that two impinging characteristic of the same family will generate a shock ... but more realistically you have to solve the so-called Riemann problem to obtain more information. E-mail me for further explanations. Bye

Rich E November 17, 2000 12:46

Re: Are characteristics shock waves?
A characteristic is a line along which an infintely weak shock, called a Mach wave, would lie if you placed a very small perturbation in the flow at the point of origin of the characteristic. You can draw two characteristics (a left running one and a right running one)eminating from any point in a (supersonic) flow field. They are useful because the govering equations describing the flow reduce from partial diffs to ordinary diffs along the characteristic. Hence by drawing a mesh of intersecting characteristics you can propagate an flow field solution from upstream to downstream. This is known as the method of characteristics

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