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Old   June 10, 2013, 09:27
Default Shape Sensitivity
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Roberto Pieri
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Hi developers,

I have a question about shape sensitivity. I am simulating laminar subsonic flow around NACA0012 airfoil, at same flow conditions of Castro et al. paper "Systematic Continuous Adjoint Approach to Viscous Aerodynamic Design on Unstructured Grids":
  • M = 0.3
  • Re = 1000
  • AoA = 2.5^o
  • T_{\infty} = 273.15

I have simulated two adjoint cases: the first with J=DRAG, the second J=LIFT.

Attached below you find shape sensitivity of both simulations. Regarding drag sensitivity you can see that signs are opposite with respect to the paper. Is it due to different normal vectors conventions?

Concerning shape optimization, I noticed that the code, after adjoint simulations, writes the file of_grad_cd.plt or of_grad_cl.plt; in these files I see gradient values (with opposite signs) at design variables declared in the configuration file.
Then, in order to deform the geometry, the code writes config_MDC.cfg, but in this case signs are inverted only if DRAG objective function is declared, while in case of LIFT objective function signs are not inverted. So my question is: does the code change deformation direction in order to maximize LIFT and minimize DRAG, in any case?

Best regards,
Roberto
Attached Files
File Type: pdf SensCD.pdf (55.9 KB, 25 views)
File Type: pdf SensCL.pdf (56.6 KB, 6 views)
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Old   June 11, 2013, 17:48
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Trent Lukaczyk
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Quote:
Originally Posted by robyTKD View Post

Concerning shape optimization, I noticed that the code, [...] signs are inverted only if DRAG objective function is declared, while in case of LIFT objective function signs are not inverted. So my question is: does the code change deformation direction in order to maximize LIFT and minimize DRAG, in any case?

Best regards,
Roberto
Hi Roberto,

indeed, shape_optimization (and the Design() class if anyone is using it) is programmed maximize LIFT, EFFICIENCY, THRUST and FIGURE_OF_MERIT

if you would like to minimize, you can change the sign of the scale parameter, for example

OBJ_FUNCTION = LIFT * -1.0

- Trent
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Old   June 13, 2013, 18:52
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Francisco Palacios
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Could you please send us the config file that you are using. This kind of laminar flows work very well in SU2.

Cheers,
Francisco
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Old   June 13, 2013, 19:05
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Roberto Pieri
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Quote:
Originally Posted by rktchip View Post
indeed, shape_optimization (and the Design() class if anyone is using it) is programmed maximize LIFT, EFFICIENCY, THRUST and FIGURE_OF_MERIT
Thank you for the reply Trent. Now I understand the behavior of shape optimization. But I don't understand why, in files of_grad_*.plt, signs of shape sensitivity are inverted.

Attached below you find the configuration file of the case.

Best regards,
Roberto
Attached Files
File Type: txt lam_NACA0012.cfg.txt (10.3 KB, 9 views)
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