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Old   May 9, 2014, 15:40
Default Optimization objective
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Sreekanth
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Hi,

In the configuration file, there is an option to specify objective function with the scale. Objective functions are drag , lift etc. How does the solver know whether its a minimization or maximization problem.

In my case , i am interested in minimizing the force on an object. So how should the objective function be specified?

Thanks,

Sreekanth
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Old   May 15, 2014, 16:13
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Sean R. Copeland
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Hello Sreekanth,

Generally, objective functions in SU2 are always minimized (there are some exceptions like efficiency). For an example on how to specify a design problem in SU2, visit the TestCases/euler/naca0012 and look at the optimal design settings in the NACA 0012 configuration file provided.


Hope that helps,
Sean
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Old   May 16, 2014, 02:11
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Sreekanth
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Hi,
Thanks for the reply.
You say there are some exceptions.
1. By default, is "Lift" being minimized or is it maximized?
2. If its being maximized, can i convert it to minimization problem by multiplying with -1 ?
3. Can i have a linear combination, or a ratio of the two terms, say (LIFT + 10* DRAG )? I tried giving like that, but it doesn't work.

Sreekanth
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Old   May 16, 2014, 03:10
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Trent Lukaczyk
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hey sreekanth,
lift is maximized by default. you can set the scale to be negative to change that --
OPT_OBJECTIVE = LIFT * -1.0
You can't combine objectives here at the moment, tho be sure to explore posing your problem with constraints, like lift constrained drag minimization. You can also take a look inside of shape_optimization.py to see how you can build your own objective functions in python.
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