# SU2_GEO - strange outputs when using FUSELAGE geometry

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April 29, 2019, 09:55
SU2_GEO - strange outputs when using FUSELAGE geometry
#1
Member

Cameron
Join Date: Jul 2012
Posts: 33
Rep Power: 9
I'm testing a case to eventually use for shape optimisation, just to find the minimum drag geometry.

To start with I'm doing a Euler simulation, but will hopefully do a full viscous RANS simulation if resources allow.

Right now however I'm having dificulty with the SU2_GEO outputs. It seems to correctly find the extents of my geometry, however it doesn't correctly calculate the widths and heights at each station. It also calculates a length, which I don't understand.

Below is the fuselage_description output for my geometry. The x measurements make sense, some of the height and width values make sense, but then they suddenly become very small at about x=0.

Can anyone help explain some of this output? The length values don't make sense to me for a fuselage, and I'm not sure what it means by the axis curve (the geometry is symmetric about the xz plane, with the axis along the x direction at y,z=0).

Code:
``` "x (m)","Area (m^2)","Length (m)","Width (m)","Waterline width (m)","Height (m)","Curvature (1/in)","Generatrix Curve X (m)","Generatrix Curve Y (m)","Generatrix Curve Z (m)","Axis Curve X (m)","Axis Curve Y (m)","Axis Curve Z (m)"
-0.391666, 2.0572e-06, 0.0107867, 0.00233133, 0, 0.0104941, 0.000580435, -0.391666, 0.0380485, -0.0107661, -0.391666, 0.0392142, -0.00551907
-0.337499, 2.2235e-06, 0.0195423, 0.000836897, 0, 0.00770312, 11.5096, -0.337499, 0.108548, -0.00860205, -0.337499, 0.108967, -0.00475049
-0.283332, 0.000498456, 0.151218, 0.0983626, 0, 0.111776, 15.3905, -0.283332, 0.0430669, -0.109861, -0.283332, 0.0922482, -0.0539724
-0.229166, 0.000274447, 0.149868, 0.0789213, 0, 0.115905, 14.358, -0.229166, 0.0827403, 0.115058, -0.229166, 0.122201, 0.0571055
-0.174999, 0.000190178, 0.140332, 0.0710254, 0, 0.120144, 10.8545, -0.174999, 0.104153, -0.11851, -0.174999, 0.139665, -0.0584383
-0.120833, 0.000329543, 0.147292, 0.0737461, 0, 0.126231, 12.6581, -0.120832, 0.110108, -0.125257, -0.120832, 0.146981, -0.0621417
-0.0666659, 8.04237e-06, 0.0376818, 0.000667993, 0, 0.0129337, 11.4911, -0.0666658, 0.187772, -0.013628, -0.0666658, 0.188106, -0.00716115
-0.0124992, 4.6593e-06, 0.0332159, 0.000633628, 0, 0.0130676, 0.0336452, -0.0124992, 0.188566, -0.0127798, -0.0124992, 0.188883, -0.00624605
0.0416675, 1.31539e-06, 0.0190956, 0.000594027, 0, 0.0129945, 12.3311, 0.0416675, 0.186328, -0.0119269, 0.0416675, 0.186625, -0.00542971
0.0958341, 0.000584583, 0.189552, 0.0900109, 0, 0.142377, 12.9921, 0.0958344, 0.0919278, -0.140776, 0.0958343, 0.136933, -0.0695871
0.150001, 0.000421042, 0.17877, 0.102838, 0, 0.144463, 10.4573, 0.150001, 0.0717813, 0.146362, 0.150001, 0.1232, 0.0741307
0.204167, 0.000416058, 0.181969, 0.109646, 0, 0.14333, 4.41099, 0.204167, 0.0555976, 0.145297, 0.204167, 0.11042, 0.0736327
0.258334, 0.000151298, 0.130896, 0.0600619, 0, 0.115696, 7.04878, 0.258334, 0.0939299, 0.117497, 0.258334, 0.123961, 0.059649
0.312501, 0.000577989, 0.186855, 0.128959, 0, 0.131756, 12.2512, 0.312501, 0.0120511, 0.13315, 0.312501, 0.0765305, 0.0672724
0.366668, 0.000212571, 0.138837, 0.0713514, 0, 0.109143, 11.7738, 0.366668, 0.0550459, -0.108348, 0.366668, 0.0907216, -0.0537769
0.420834, 0.000328104, 0.137141, 0.0760334, 0, 0.100087, 1.74348, 0.420834, 0.0341859, -0.0999613, 0.420834, 0.0722026, -0.0499178
0.475001, 0.000117446, 0.104337, 0.0573863, 3.24177e-05, 0.0807455, 1.02177, 0.475001, 0.0351131, -0.0811942, 0.475001, 0.0638063, -0.0408214
0.529168, 0.000201647, 0.102995, 0.0639467, 0, 0.0681053, 10.3901, 0.529168, 0.00924431, -0.0688659, 0.529168, 0.0412177, -0.0348132
0.583334, 8.16991e-05, 0.070826, 0.0496978, 0, 0.0491163, 14.428, 0.583334, 0.00248699, 0.0483997, 0.583334, 0.0279359, 0.0238539
0.637501, 1.89978e-05, 0.0361603, 0.023899, 0, 0.0266037, 1.17887, 0.637501, 0.00539012, 0.0262555, 0.637501, 0.0173396, 0.0129537
0.691668, 7.50935e-07, 0.0053006, 0.00296616, 0, 0.00349867, 0.811744, 0.691668, 0.00102289, -0.0034512, 0.691668, 0.00250597, -0.00170187```
I also keep getting some strange pressure fluctuations on the fuselage surface, they consistently appear with different meshes so I suspect it's a numerical issue. If anyone has any idea about those that would be good too.
Attached Images
 Screenshot from 2019-04-29 14-52-03.png (66.8 KB, 9 views)
Attached Files
 fairing_opt_inv.cfg.txt (17.9 KB, 4 views)

Last edited by c_dowd; April 29, 2019 at 10:18. Reason: Fixed code formatting a little

 April 29, 2019, 12:33 #2 Member   Cameron Join Date: Jul 2012 Posts: 33 Rep Power: 9 So on further inspection it seems to be due to the fact that it's a symmetry geometry, as the functions work properly for the Ahmed body example. Not sure of the easiest way to fix this, as I want to have the width and height of the body at various stations as constraints for my optimisation.

 September 4, 2019, 05:18 SU2_GEO stange outputs #3 New Member   Angu Praveen Join Date: May 2019 Posts: 13 Rep Power: 2 Hello, I am also facing a similar issue. I'm working on the optimization of a BWB aircraft. Unfortunately, every time I run SU2_GEO to determine the wing thickness for constraints, I get wrong values. The thickness is in the order of 5-6 meters. Is there a fix to this problem?? Kind regards Angu

 Tags su2, su2 geometry, su2 shape optimisation, su2_geo