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How are shockwaves able to refract? As said in this,

When two shock waves collide, they interact with each other and produce complex patterns of compression, rarefaction, and reflection. The resulting behavior depends on the strength, speed, and direction of the shock waves, as well as the properties of the medium they are traveling through.

I understand how they might be able to pass through each other, but why would they refract? Light and optics are a bit different than aerodynamics at supersonic speeds I'd imagine.

Also, refracting meaning when a shockwave refracts off of another shockwave. I assume they have to be different densities to refract off of each other.

Wyatt
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    I'm not the down voter, but while the topic is interesting, as a Stack Exchange question this is currently low quality. If you hold a cursor over the down vote arrow the tooltip suggestion for that action is "This question does not show any research effort... Downvoting is exactly the correct action when a question does not demonstrate any effort to look for an answer first, before posting here. – uhoh Mar 31 '24 at 02:11
  • Also, do you mean a shock wave refracts around higher/lower density air some distance away, or another shock wave, or light is refracted by a shock wave? It's not even clear what you are asking. What would the density profile of this shock wave look like, roughly? and How is the camera positioned for these plane-to-plane Schlieren images of shock waves? and What do the components of a shockwave's visual artefacts represent? – uhoh Mar 31 '24 at 02:13
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    @uhoh I am mainly taking about the effect where shockwaves can refract off of each other. – Wyatt Mar 31 '24 at 02:15
  • @uhoh also how might this question be "low quality"? Besides missing the part explaining what I meant by refracting (added it just now), I fail to see how this is low quality. – Wyatt Mar 31 '24 at 02:18
  • Ah that's much better! +1 So refraction happens at gradients/interfaces, so probably what's most important is the angle between the two shock wave fronts, if it happens at all. For normal sound waves, the air response is linear so two waves pass through each other without affecting each other. But the shock wave response will be very non linear, and each can certainly interact (and maybe refract) the other. Interesting phenomenon! Add a link suggesting at least a little prior research (e.g. where you first read that shock waves can refract) and your question will be even better received. – uhoh Mar 31 '24 at 02:19
  • Oh, from a Stack Exchange community point of view, short questions, questions without research and questions that have ambiguity (are unclear) are all considered low quality. It's the question post itself - how it's written, not the underlying question. You've already made a big improvement with that edit! Now add some kind of link referencing refraction and the perceived quality of the post will be even higher! – uhoh Mar 31 '24 at 02:20
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    @uhoh I see. I was going to add something like a picture of it, but I personally couldn't find anything that looked acceptable. After a bit of research, I found where I initially got this idea from, adding it now! – Wyatt Mar 31 '24 at 02:43
  • Do you have any flat sandy beaches near you? Have or a lake where you can observe waves and ripples interacting with one another when they intersect? – Michael Hall Mar 31 '24 at 03:31
  • @MichaelHall do low amplitude gravity waves (i.e. ripples on a liquid surface under the influence of gravity) really interact with each other, or like normal sound waves do they pretty much pass through each other without interracting? (i.e. linear superposition -there are waves and ripples (and ducks!) in the first image and caption in that article. I don't think it's a good analogy for shock waves which are extremely high amplitude and very nonlinear. – uhoh Mar 31 '24 at 08:09

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The quote you cite does not say refraction. It says rarefaction.

Refraction (of light) is when light bends because it transitions from one material to another -- say air to water.

I do not think people talk about shocks refracting -- if you have an example, please post it and ask specific questions about it.

I found this image of a refracted shock. Here, an explosion occurred at the 'Source' above the ground. The initial shock spreads out spherically. When the shock hits the ground, there is both a reflection from the surface of the earth -- and also a transmission of the shock into the earth.

enter image description here

The shock will travel differently through earth than through air -- at a minimum, the speed of sound in a solid (or liquid) is much different than the speed of sound in a gas.

While this is a fascinating problem, I don't think it is what you're actually interested in.

Rarefaction is a process of becoming more rare -- spreading out -- weakening. Shocks can interact in a way that they weaken one another.

Instead of using the words Rarefaction, I believe I usually use the term 'Expansion Fan'

Here is an image of two shocks interacting that cause an expansion fan -- I think this could also be called a rarefaction zone.

enter image description here

As some of the criticism alludes, this question shows that you've put in very little effort. You're asking the answerer (us) to do more effort than you did. That is generally bad form. It is much better for you to come to us with small specific details after you've conducted extensive study.

Also, I saw that you posted this in Physics Stack Exchange. I believe it is bad form to cross post identical posts at the same time.

Unfortunately, there is no 'Aerospace Engineering' stack exchange. For the most part, Aviation SE is willing to tolerate us asking and answering Aerospace Engineering questions here, but we do occasionally get asked 'Is this Aviation'?

That said, Physics SE is not the right place either.

Rob McDonald
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    I see. So I understand that part, but if you look at the right diagram on this page from NASA, the shocks seem to bend as they cross. Is this considered rarefacting? - my usual way of asking questions is I will do my research (maybe not as much as I should), and then if I have specific questions I’ll come here and ask without providing evidence that I have done such research. I try to keep the question short and simple, but maybe I should – Wyatt Mar 31 '24 at 05:22
  • Start providing the research. – Wyatt Mar 31 '24 at 05:23
  • I rarely ask the same question twice, but sometimes I feel P.SE is more suited for some questions more related to physics (not that this one even is this time). Shouldn’t have done it, but at the time I thought it was a good idea. – Wyatt Mar 31 '24 at 05:28
  • One last thing: if shocks going into the ground refract, why wouldn’t they do that going through other shocks? The formula for sound speed is $c=\sqrt{\frac Kρ}$. If density is higher, (in shockwave) wouldn’t that change the speed of sound, making the shock refract? – Wyatt Mar 31 '24 at 15:41
  • (If the density was higher in the shock that a different one was going through) – Wyatt Mar 31 '24 at 15:48
  • Well actually never mind about that part; the shocks make destructive interference so they don’t have time to refract. – Wyatt Mar 31 '24 at 16:33
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    The figure at the right in your image from NASA. Those shocks bending is not called rarefacting or refracting. That is just bending a shock. These two examples have great descriptions in the text on that NASA page. That kind of thinking is exactly how you should approach problems like this. – Rob McDonald Mar 31 '24 at 22:35