extract boundary surfaces

(Dimitris) #1

Hello there,

I have a 3D domain ( wing + flow field) and I want to extract the outer boundary surfaces without including the interior ones. I use the ExtractSurface filter but apart from the boundaries of the domain I always obtain and the surface of the wing, something that I dont want.

I have uploaded a screenshot of a clip of the ExtractSurface output.

Any suggestions how to solve this ?

(Cory Quammen (Kitware)) #2

High level: You can select the cells defining the wing, then invert the selection in the Find Data dialog to obtain the outer boundaries, then extract the selection. This will remove the wind from the resulting surface.

(Dimitris) #3

Thanks for the answer !!

Its helpful indeed but I still have a problem. The faces of my interior domain “fluid” overlaps with the outer boundary surfaces and the wing. So when I invert my selection in the Find Data dialog the wing surfaces are not included but the overlapped faces of the “fluid” on the wing are still there, forming again the surface of the wing. If I remove and the interior “fluid” domain I lose my downstream transverse plane (which is the output of the ExtractCellsByRegion).

To help you understand I need to develop a far-field drag post-processing method.

The option to manually select the faces of the cells on the wing (with the select cells through) is not suitable since I need to script my method and I cannot know a priori the id of the wing cells.

Is there any way to split the surfaces of the blocks (symmetry, far-field, wing) and the faces of the grid of the interior domain (fluid) ?


(Cory Quammen (Kitware)) #4

Is your data a multiblock dataset? Look in the Information tab if you aren’t sure.

(Dimitris) #5

Yes… it is a multiblock dataset !!

(Cory Quammen (Kitware)) #6

Ah, in that case, hopefully your wing is in a separate block. Open up the Multi-block Inspector (View menu -> Multi-block Inspector). Your wing block may be labeled as such in which case try unchecking that block in the Multi-block Inspector, otherwise try to hide the blocks until you’ve found it. Once you’ve identified the wing block, use the Extract Block filter to select all the boundary blocks and not the wing block. Then add an Extract Surface filter. The wing will be excluded, but you will have the other surfaces.

(Massimiliano Leoni) #7

A trick I used in this situation is to apply a clip filter to the extract surface filter, selecting a box or sphere clip. If the geometry is simple enough it should work.

(Dimitris) #8

First of all thanks a lot for your replies and sorry for my delay to answer.

@cory.quammen your tip is useful but unfortunately does not apply to me since the problem is still there. The problem arises due to the internal mesh (interior “fluid” domain) and the faces of its cells that overlap with the wing surface… as I explained in my previous message.

I believe that the trick of @Massimiliano_Leoni works for me… it is how I solved it !!

Thanks to all !!