Preprocessing

Preprocessing

Element generation on point clouds

    • kramer
      Subscriber
      Hello,nI want to automatically generate a meshed model in APDL. Since my geometry is irregular and I do not want to use a CAD system, it seems the way to go is to generate a list of nodes and then create elements out of them. I have two questions on that:n1) I know I can use EN and ENGEN to create the elements using a pattern. Is there an alternative that does not require a regular pattern (i. e. that just accepts an array of nodes and arranges the elements suitably) ?n2) With EN and EMORE, we can specify up to 16 nodes for an element, which is insufficient for higher order elements like SOLID186. It is possible to create a SOLID186 using the 8 corner nodes, but when displaying the element list, the remaining 12 nodes are assigned the number 0 and are not shown when activating the displaying of nodes under PlotCtrls. Is there a way to get it right?n
    • peteroznewman
      Subscriber
      Elements must have shapes that comply with limits on shape metrics such as skewness, aspect ratio and a lot of other metrics. The ANSYS meshing algorithms are very good at filling a volume with elements that have acceptable shapes. There are geometry algorithms that are very good at fitting geometry to point clouds. I recommend you go this route.n
    • kramer
      Subscriber
      So what you say is I should first generate a volume from my point cloud, generate an iges or something and then mesh that volume with Ansys? My problem is that I want to avoid using a separate (non Ansys) program for geometry generation. But Ansys itself seems to support only primitive geometries (cube, sphere, cylinder...) or direct element generation via node numbers which is tedious...n
    • peteroznewman
      Subscriber
      Ansys has SpaceClaim and DesignModeler for geometry generation. SpaceClaim is newer and has a scripting language.nI would like to see what your point cloud looks like, so please attach a zip file with the data if you are willing to share it.n
    • kramer
      Subscriber
      Sorry for my late response, I was on holiday for the past week. Thank you for your answer. Here is an exemplary point cloud which creates the surface depicted on the attached jpg when plotted with Matlab. My surfaces are artificially generated from functions, so it would be interesting to know if SpaceClaim can process functions too?n
    • peteroznewman
      Subscriber
      nThank you for the pointcloud. I see you took the coordinate data and reformatted each component vector into a matrix. Not sure why you would do that. Now I need to reformat it into a vector, but I don't know if I should stack by row or by column.nSpaceClaim has a full scripting language so I expect you can generate surfaces from functions.nI have matlab, so if you want to share the code that generates the surface, that would be interesting.nn
    • peteroznewman
      Subscriber
    • kramer
      Subscriber
      Thanks for your response. The matrix form is due to the fact that Matlab's surf function demands matrix instead of vector input, but of course I can easily format the data to fit Ansys requirements. So what I get from the txt file is that an empty line is used to indicate the start of a new curve. Does the import only work with lines or can we also import surfaces or volumes?nBy the way, here is the code i used to generate and plot the points:nphi = linspace(0,2*pi,100);nr = 60/2;ndelta = 1.5*sin(5*phi);nz = ones(100);nz = z.*linspace(1,10,100);nz = z';nx = r*cos(phi)+delta.*cos(phi);ny = r*sin(phi)+delta.*sin(phi);n[a,b] = meshgrid(x,y);na = a+a.*z(:,1)*0.005;nb = b';nb = b+b.*z(:,1)*0.005;nsurf(a,z,b,"EdgeColor","none')nxlabel('x')nylabel('y')nzlabel('z')naxis equaln
    • peteroznewman
      Subscriber
      nSpaceClaim can import a large number of file formats that can have surface or solid bodies, in addition to what I showed for importing curves through points.nVendor neutral files include: ACIS, IGES, Parasolid, Rhino, STEP, STL, VRML.nn
    • kramer
      Subscriber
      Thanks once more. The problem is that the neutral file types I know about have a rather complicated syntax and therefore are hard to generate by a script (e. g. in Matlab). Well, in the end I think I can just go with the method you suggested. Regarding the scripting: Is there a way to launch Ansys from the command line with a script as input (rather than launching it manually)?n
    • peteroznewman
      Subscriber
      I don't know about scripting. I hope someone else might answer.n
    • kramer
      Subscriber
      Ok, no problem. Thank you for your efforts n
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