how to know if a deflection in a supersonic isentropic flow causes compression (oblique shock) or expansion (Prandtl-Meyer expansion) Thanks in advance.

an example of a problem that is related to my problem

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  • $\begingroup$ define the deflection? $\endgroup$ – Solar Mike May 19 '19 at 16:45
  • $\begingroup$ Deflection means that when the flow changes its direction to become parallel to a surface of a wedge or any similar thing that intercepts the flow. $\endgroup$ – صهيب أبو ريدة May 19 '19 at 17:48
  • $\begingroup$ converging or diverging? $\endgroup$ – Solar Mike May 19 '19 at 17:49
  • $\begingroup$ I added a link of a problem that may help make my question clear. $\endgroup$ – صهيب أبو ريدة May 19 '19 at 17:59
  • $\begingroup$ Add it as an image - many of us don't follow links... $\endgroup$ – Solar Mike May 19 '19 at 18:00

Really easy: Calculate the deflection angle beta. If the angle is positive, then it's an oblique shockwave, but if it's negative, then you have an expansion. If the angle beta is zero, then there's neither compression nor compression and if beta is 90º (π/2) you have a normalmente shockwave.

An expression that may help you (I did a report on this and demonstrated the formulæ):

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