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Multiple FFD box definition for shape optimization study

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Old   October 28, 2013, 02:19
Default Multiple FFD box definition for shape optimization study
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Anant Diwakar
Join Date: Jan 2013
Posts: 68
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Hi,

I intend to run shape optimization study for a flying wing configuration
for which I need to define 2 FFD box definitions.

I have defined the FFD box parameters as

Code:
FFD_NBOX= 2
FFD_NLEVEL= 1
FFD_TAG= 0
FFD_LEVEL= 0
FFD_DEGREE_I= 5
FFD_DEGREE_J= 4
FFD_DEGREE_K= 1
FFD_PARENTS= 0
FFD_CHILDREN= 0
FFD_CORNER_POINTS= 8
-10.0      0.0    -30
160    -130    -30
440    -130    -30
520     0.0    -30
-10.0      0.0    70
160    -130    70
440    -130    70
520     0.0    70
FFD_CONTROL_POINTS= 0
FFD_SURFACE_POINTS= 0
FFD_TAG= 1
FFD_LEVEL= 0
FFD_DEGREE_I= 5
FFD_DEGREE_J= 4
FFD_DEGREE_K= 1
FFD_PARENTS= 0
FFD_CHILDREN= 0
FFD_CORNER_POINTS= 8
160    -130    -30
480    -370    -30
580     -300    -30
440    -130    -30
160    -130    70
480    -370    70
580     -300    70
440    -130    70
FFD_CONTROL_POINTS= 0
FFD_SURFACE_POINTS= 0
I obtained the FFD box, as shown in the pics attached with the post.

I want to know the meaning of the FFD terms like FFD_NLEVEL,
FFD_LEVEL, FFD_PARENTS, FFD_CHILDREN etc. and what values
should to be taken for multiple FFD box definitions.

Also, for how to define the FFD parameters for the 2 FFD boxes
in the DEFINITION_DV option in the .cfg file ?

Thanks
Anant
Attached Images
File Type: jpg ffd_front.jpg (21.0 KB, 29 views)
File Type: jpg ffd_top.jpg (43.5 KB, 25 views)
File Type: jpg ffd_isometric.jpg (41.9 KB, 27 views)
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Old   November 5, 2013, 18:46
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Thomas D. Economon
Join Date: Jan 2013
Location: Stanford, CA
Posts: 270
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Hi Anant,

Thanks for the post. In terms of the extra options for the FFD boxes (LEVEL, PARENTS, CHILDREN, etc.), these are new features for defining nested FFD boxes (one inside another) so that you can more easily perform large scale and local deformations to your geometry. We will prepare more documentation on these features soon.

As for defining FFD control point variables on multiple boxes, note the format of the DV specification in the config_template.cfg file:

FFD_CONTROL_POINT ( FFD Tag, i_Ind, j_Ind, k_Ind, x_Disp, y_Disp, z_Disp )

The corresponding FFD box for a particular control point is given by the FFD Tag. This is the first entry for each control point variable.

Hope this helps,
Tom
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