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over a supercritical aerofoil, would a shockwave move downstream with increase in angle of attack?

I thought yes as the top surface is flat?

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  • $\begingroup$ Haven't you already asked the same question some days ago? $\endgroup$
    – sophit
    Apr 23 at 11:40
  • $\begingroup$ Hi, so that question is concerning deflection, this one is concerning a supercritical aerofoil with angle of attack $\endgroup$
    – FlightWatcher
    Apr 23 at 13:24

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I do not think there is a single answer for all supercritical airfoils -- and the answer will also vary with Mach (and probably Reynolds number).

Some supercritical airfoils are designed to be shock-free. Are you operating one of those airfoils above the design mach number?

Generally speaking, increasing lift will increase acceleration at the suction peak (around the LE and front of the airfoil). The region of supersonic flow on the front, upper surface of the airfoil will grow -- the highest Mach number in that supersonic region will increase.

In general, I believe that will cause the shock to move forward and increase in strength.

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  • $\begingroup$ And I believe that will cause the shock to move backwards and increase in strength. A stronger shock means a larger change in speed and pressure, and that higher pressure is reached in the outer flow only further downstream. In other words, the air "does not see" a need to drastically change its parameters until further downstream. $\endgroup$
    – Peter Kämpf
    Apr 24 at 6:28
  • $\begingroup$ Hi Rob and Peter, sorry just to clarify, does that ‘forward’ mean towards the leading edge? Also why does increase in AOA increase the maximum Mach over the aerofoil? Wouldn’t increasing the aoa make it harder for the flow to travel over the aerofoil? $\endgroup$
    – FlightWatcher
    Apr 24 at 13:25
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    $\begingroup$ @PeterKämpf may be right (that I have my conclusion backwards). Without taking a stand on that (I'll have to do more work to be sure) -- Increasing AoA always causes more acceleration over the leading edge and a higher suction peak. The higher velocity is fundamentally how more lift is achieved. And yes, 'forward' means towards the leading edge. $\endgroup$
    – Rob McDonald
    Apr 24 at 16:06

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