Wow @Buckeye !
That is BEAUTIFUL !
Could the CFD model somehow be factoring in the stall angle for the fins ?
Both the NACA 0012 and a flat plate stall at about the same AoA as your 'anomolous data' ...
-- kjh
Hmmm ... so maybe you could write a paper like, say ... "What Barrowman and Galejs left out"<<snip>>
The CFD, minus the 12 degree anomaly, matches the linear trend of the Galejs equations. The y-axis scale purposely runs out to 1.0 caliber to illustrate the absurdly- small movement of CP with angle of attack. This is why short, stubby rockets are very stable with low CP-CG margins.
View attachment 635340
A look at streamlines at 12 degrees and a little bit on either side should be illuminating. It seems odd that the CP would shift back to the original spot if the fins lost lift due to stall, though.Oh, wow! I did not consider that. CFD is picking up the stall. That is a good explanation!
Would surface pressure plots show the stall on the fins? This is really juicy stuff!
I was just curious what the surface pressure plot on the windward and leeward sides looked like. I marked up your diagram from earlier. I've long been curious about Openfoam when a colleague at work recommended it. I'm not a Linux user, and tried to run a bootable Ubuntu session but could not get OF to install properly...I gave up then. My career work has been structural FEA, but I dabbled with CFD at work. Since I retired, I've lost access to the software.Yes, anything is possible in CFD post-processing. Is there anything in particular you want to see on the rocket surface?
Here ya go. Leeward and windward sides at 12 degrees angle of attackI was just curious what the surface pressure plot on the windward and leeward sides looked like. I marked up your diagram from earlier. I've long been curious about Openfoam when a colleague at work recommended it. I'm not a Linux user, and tried to run a bootable Ubuntu session but could not get OF to install properly...I gave up then. My career work has been structural FEA, but I dabbled with CFD at work. Since I retired, I've lost access to the software.
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