# Explanation of supersonic flow differences between a 2D wedge and a 3D cone

I know that in case of wedge we have a 2D behavior which creates a discontinuity across the shock, but I am unable to understand why this discontinuity is not present in the case of a conical surface. I have a vague idea that the continuity equation ensures this as, due to increase in the flow area, the velocity must increase.

But still it would be great help if I could get a proper explanation, I couldn't find one in books and net.

I would also like to know which 2D constraints are actually relieved which causes the 3D relaxation effect.

EDIT:- I think i need to reiterate the question, I wanted to ask why does the supersonic flow bend toward the surface in case of being obstructed by a cone unlike in case of wedge, and as per its reasoning i have also read that the flow is more free in case of cone, due to presence of 3 dimensions, commonly known as 3D relaxation, so it would be nice if someone could comment upon it too.

• Really vague and unclear question. Could you edit it to explain all the context? Without the comments it could even be asking about hammering a spike into wood/concrete. Apr 5, 2015 at 21:03
• With your edit, what do you mean by "bend toward the surface"? Both the wedge and the cone are "bending" in a very similar way at the shock front. Are you asking why one is drawn as straight lines (wedge) and one has some curves (cone)?
– hazzey
Apr 6, 2015 at 14:00
• yes exactly, thats what i want to know, why parallel in one case and not in other. Apr 6, 2015 at 16:27
• I think the best way to get a "heuristic" understanding is to jump over to [Nasa] (grc.nasa.gov/WWW/k-12/airplane/shock.html). They have a nice simulator which solves the equations for you and does not only draw stream lines but also rays (which are the answer to your question). Apr 18, 2015 at 17:36