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Method of Characteristics for underexpanded flows

  1. Jun 4, 2013 #1
    So I have, what I believe is a pretty specific problem. I am coding up a program in matlab for a 2D or axisymmetric MOC (it does both). This code does not use an isentropic nozzle, but rather allows the user to select two angles to describe the nozzle wall, the beginning angle as well as an ending angle at the lip of the nozzle exit (the user also inputs other necessary values to describe the geometry). The program creates a second order polynomial to describe the wall from this input. The reason for this is because it is much simpler to machine these types of nozzles. Past experiments have used conical nozzles which I intend to validate my code with.
    My problem lies with the use of the conical nozzle, or any nozzle which does not produce uniform flow. Due to the diverging angle at the exit, an 'intercepting shock' occurs directly after the last expansion wave at the end of the nozzle. This intercepting shock is of variable strength, 0 at the free pressure boundary and very large at the centerline. Does anyone have any experience with this or know how to calculate the values across the shock? Once I can get past the shock, the flow should still be supersonic and the MOC can finish.
  2. jcsd
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