[hollyflame]

Hello,
I am a student of Mechanical Engineering and I am new this forum. I have been working on CD nozzle design using MOC along with my colleague. We formulated a method adapting the approach of John and Keith to develop the curve for the expansion region of a minimum length CD nozzle to achieve a Mach no. 3 at exit. Characteristic lines originate from the throat height and are reflected from the central axis to reach wall. For Mach 3, Nu is 48.76 which meant that maximum deflection angle for minimum length nozzle was 24.88. We did initial work on excel and got results for 25 lines, i.e. taking one degree increment for alpha. The results achieved for that sheet were very satisfactory, A/A* at exit corresponded to Mach No.3. After we developed a matlab code, we found that the result converges when the no. of characteristic lines are lesser than 25 and diverges when no. of characteristic lines are greater than 25. The results varied as much as to give nearly double the exit height and length for 100 characteristic lines (only the size of increment was decreased while keeping all constraints constant). We are thus unable to improve the accuracy of our profile. We are practically stuck at this point. Any help would highly be appreciated.
Excel Sheet and Matlab code have been attached.
Thanking you in anticipation.
Regards.