What Are the Key Concepts Behind Compressible Shock Waves and Their Curves?

[stephane]

Hi all,

I have some prob to undestand the shock wave in compressible flow, more precisely the "theta, beta, Mach curve)

- Why when "theta" exceeds theta (max) there is no oblique shock? (how we can explain this physicaly)?
- What is the difference betwwen weak shock and strong shock?
- why in weakv shock the flow is supersonic ahead and subsonic when we have a strong shok?

Please could you explain? thanks

 

[boneh3ad]

- Why when "theta" exceeds theta (max) there is no oblique shock? (how we can explain this physicaly)?

Mathematically, the solutions to the $\theta$-$\beta$-$M$ equation become imaginary at this point. Physically, it means that there is no longer enough space between the surface and any attached shock to pass the mass flow required to maintain continuity, so the shock detaches.

- What is the difference betwwen weak shock and strong shock?

One (strong) results in $M_2>1$ downstream and one (weak) results in $M_2<1$ downstream. It may be easier to call these two cases the extraordinary and ordinary solutions, respectively, rather than strong or weak. It isn't as common to do this but it may make more sense to you given that it is almost always the weak shock that develops in the real world.

- why in weakv shock the flow is supersonic ahead and subsonic when we have a strong shok?

I am not really sure what you mean here. Before passing through the shock, the flow must be supersonic in both cases.