Design Modeler 2D surface refinement

avidanoavidano Member Posts: 14
edited January 13 in Preprocessing

Hi to all!

I am new to cfd and am struglling with preparing the model for meshing. I want to refine the rectangle around the cylinder, but I cannot get 1part and 2 bodies to the Ansys Meshing.

I have surface made from 2d cylinder inside a circle domain (sketch1) and surface made from rectangle and cylinder(sketch3) as shown in the attached figure. Is cylinder in sketch3 excess?

I tried with several different methods but either I end up with the meshed cylinder interior either whole rectangle mesh-free.

Can someone tell me the steps I need to do? I have lost a lot of time struglling with this issue.

2d_cylinder_refinement.jpg


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Comments

  • RobRob UKForum Coordinator Posts: 8,395

    Please can you post the image so we can see it? Staff aren't permitted to open attachments. If it's 2d have you built the model on xy plane and set the workflow to 2d before opening Meshing?

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  • avidanoavidano Member Posts: 14
    2d_cylinder_refinement.jpg

    Hi Rob, here is the image.

    Under the geometry options I have put the 2D analysis. Also, it is built in xy plane as shown in the image.

    Thank you for the effort!

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  • peteroznewmanpeteroznewman Member Posts: 11,072

    @avidano

    You need to start a New Sketch on the XY plane and draw a rectangular body. You need a rectangular hole in the first body.

    Review this discussion: https://forum.ansys.com/discussion/432/how-i-can-split-surfaces

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  • avidanoavidano Member Posts: 14
    edited January 17

    Thank you @peteroznewman. To sum up for others: create plane, make surfaces, use slice operation, use boolean operation where necessary and in the end just select all surfaces to make new part. Result is 1 part with multiple bodies.

    Below I attach my drive link to wbpz as file size did not reduce much when mesh was cleared. I would be thankful if someone could check if I did it right way and answer my doubts.

    1. Did I prepare geometry well? I did not use share topology action and didnt apply any thickness (1m as per default)
    2. There is no solid body under the part as I substracted it. Can that be a problem?
    3. Why my bodies in ansys meshing have a mix of check and cross sign?
    4. As shown in image, structured mesh seems as a better idea. In order to get boundary layer, I would like to use edge sizing with biasing but I am not sure how to divide my geometry and how many divisions to use? I saw in one disscusion to use 4 divisions, but why not 2?

    PS I have abandoned rectangles and used circles instead...

    https://drive.google.com/file/d/1TnjYG7ciIoNudlpQHnEB7nXcrld3VC63/view?usp=sharing
    unstructured.png
    structured.png


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  • peteroznewmanpeteroznewman Member Posts: 11,072

    @avidano

    You did not clear your mesh, that is why the archive file was much larger than necessary. Here is how you clear the mesh.

    image.png
    1. You did use Shared Topology when you did Form New Part.
    2. Solid bodies are not needed for a 2D analysis
    3. They are all checked.
    4. Use Split Face with the ZX plane to make an edge to apply bias along.
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  • peteroznewmanpeteroznewman Member Posts: 11,072
    image.png
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  • avidanoavidano Member Posts: 14
    edited January 17

    Excellent @peteroznewman, thank you very much!

    1. However, as shown in image there are some problems with checked signs.
    2. To get wanted first layer thickness, I need to raise bias factor up to around of 230. Is that a valid value? I mean, the local grid is now streched on one side by that factor. Are there any consequences for doing it?
    3. Very often message (selective body meshing) down there appears and disappears? What is it for? It is followed by the change of some values...
    bias.jpg


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  • peteroznewmanpeteroznewman Member Posts: 11,072

    @avidano

    1. The crossed check mark just means that is is meshed. When there is no mesh it is uncrossed. If there is a problem with the geometry such as a missing thickness or material, it is red.
    2. Bias factor is irrelevant. Element quality is relevant. You can look at mesh metrics for Aspect Ratio and Skewness. High aspect ratio in the boundary layer is appropriate because the velocity gradient is so high near the wall.
    3. Selective meshing means you are manually choosing what to mesh first. If you clear the mesh and just click the Generate Mesh button, you might not get the same mesh back, because the order of meshing can change the mesh.
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  • avidanoavidano Member Posts: 14

    Thank you very much, @peteroznewman.

    1. Regarding selective meshing, for my simple geometry I have used worksheet and mesh them all at once and the message dissapears. If you could hint me what cases would suggest priorities while meshing?
    2. My goal is to study towing cable/rope. I have done now 2D planar analysis. Can I make 3D mesh using 2D existing one? I am thinking about drawing two halves of rectangle in XZ plane (representing cable's and domain's walls), extruding the mesh and then revolving it using the new sketch. Is this possible? I am afraid I should have used 2D axisymetric analysis, but my loads are not axisymetric as the geometry is, and I am not sure how to define inlet/outlet in that case. Is there a way to use existing 2D analysis?
    3. How to mark answer or disscusion as solved here?
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