# changing geometry

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 February 12, 2006, 13:45 changing geometry #1 yann Guest   Posts: n/a Does anyone know how to change the geometry of a design without re-creating it from the biginning? How could we modify the parameters in the folder .geom, if it is the way to do so? Thank a lot, Yann

 February 13, 2006, 10:53 Re: changing geometry #2 Ben Guest   Posts: n/a can you be a bit more specific as to the term "geometry change" are you talking parametric changes, mesh changes, boundary changes etc etc?

 February 14, 2006, 09:53 Re: changing geometry #3 yann Guest   Posts: n/a Hello Ben, Yes, sorry for the lake of details. I meant that I need to do several computations with the same model, keeping the same boudary condition, but changing some dimension parameters such as the lengh of the object, the thickness: all the different sizes of the object, actullay. However, as the model is pretty much long to build, I wanted to know if there was a way to keep the same boudary conditions, just changing the different sizes, and consequentrly the meshing... Thanks in advance, Yann

 February 16, 2006, 09:17 Re: changing geometry #4 Zamir Rashid Guest   Posts: n/a Changing geometry is possible only if you prepare the mesh very carefully from the start. For example, if you want to make a certain pipe shorter or longer, this can be done by changing the type of material, i.e. from fluid to solid and vice versa, or by adding baffles etc. But to do this your mesh must be created with those changes in mind. Hex meshes also helps to make those changes easier, but that doesn't mean you can't do it with Tet meshes. I always spend the maximum amount of time in creating the initial mesh, with all the minor changes to the model being considered as well. Another tip that might be useful, if the whole geometry takes a long time to mesh and you only have minor changes at the same area of the geometry, then you could create a different mesh just for the that area, and couple the different meshes together in your solver. For example, I had to do steady state inlet port flow analysis for a certain engine. The valves only moved a couple of mm from each test case. So I created an enclosed volume surrounding the valves, and just remeshed the volume for each test case. It was a whole lot easier than having to mesh the entire model from scratch every time. Hope that helps.

 February 16, 2006, 13:43 Re: changing geometry #5 yann Guest   Posts: n/a Thanks very much for your help Rashid, but I don't really understand how changing the type of material will change the size of a pipe or anything else. Once I changed the material, nothing allowed me to change the size of the object, and if I do so in the "extent of domain" window, it then creates another object, but doesn't remplace the previous one. Regards, Yann

 February 16, 2006, 19:57 Re: changing geometry #6 Zamir Rashid Guest   Posts: n/a Here's an example of how changing the material type can change thickness of a pipe. If you created a pipe with hex mesh in cylindrical coordinates, making the pipe thicker can be done by changing a layer of cells in the radial direction from fluid to solid. Now your pipe's thickness has increased by the thickness of the additional layer of cells. If you defined your pipe geometry just by using baffles, then you can make the pipe shorter by deleting some baffles, and you can make it longer by adding them. Having said these things, they only can be done if you prepared your initial mesh to be able to do these things in the first place. Hope that helps.

 February 17, 2006, 04:35 Re: changing geometry #7 yann Guest   Posts: n/a Thanks a lot Rashid, that's great!! You've just saved me a lot of time, thank you again, Yann

 February 17, 2006, 06:40 Re: changing geometry #8 Zamir Rashid Guest   Posts: n/a My pleasure!

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