Calculate the change of volume

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  • Math_Lcrbr
    Junior Member
    • May 2019
    • 2

    Calculate the change of volume

    Hi all,

    I'm working on a prostate model to calculate the change of volume due to an edema occurring after brachytherapy surgery. I need to know the value of the volume for different time step. I saw on an other thread that there were the "enclosed volume" feature. I tried to use it but when I opened the results in PostView I don't have any values and the plot only show zeros.

    Does anyone have an idea of what I can do to obtain results ?

    Regards,

    Math
    Last edited by Math_Lcrbr; 05-27-2019, 08:26 AM.
  • maas
    Lead Code Developer
    • Nov 2007
    • 3400

    #2
    Hi Math,

    Did you specify the surface for which to calculate the enclosed volume? If not, define the plot variable as in the following example (assuming the surface is named "mysurface"):

    Code:
    <var type="enclosed volume" surface="mysurface"/>
    Let us know if that solved it. If not, please send us the input file and we can take a closer look.

    Cheers,

    Steve
    Department of Bioengineering, University of Utah
    Scientific Computing and Imaging institute, University of Utah

    Comment

    • Math_Lcrbr
      Junior Member
      • May 2019
      • 2

      #3
      Hi,

      Thanks a lot, that solve my problem

      Regards,

      Math

      Comment

      • kdwyer
        Junior Member
        • Jun 2020
        • 20

        #4
        Hi Steve and Math,
        I am having a similar problem using FEBio Studio. Under Output > plotfile I am unable to choose domains for the variables, including enclosed volume. Do you have any suggestions in how to define the surface in FEBio Studio? Or should I be using the code above in PostView?

        Kiera

        Comment

        • maas
          Lead Code Developer
          • Nov 2007
          • 3400

          #5
          Hi Kiera,

          The domains you assign to plot variables have to be "Named selections": So, first select the surfaces that you want to use. Then, make it a named selection using the menu Edit\Name Selection. It will now show up under the Named Selections item in the model tree. Then edit the plot variable and assign this selection to it.

          Please give that a try and let me know if that worked.

          Best,

          Steve
          Department of Bioengineering, University of Utah
          Scientific Computing and Imaging institute, University of Utah

          Comment

          • kdwyer
            Junior Member
            • Jun 2020
            • 20

            #6
            Thanks so much that worked to select the surface - I saw in another post on open-ended geometry that the enclosed volume with find the "missing piece" if it aligns with one of the defined planes. I am working with a half ellipsoid which has a "missing side" aligning with the XY plane but it does not seem to be registering. Do you have any advice?

            Comment

            • maas
              Lead Code Developer
              • Nov 2007
              • 3400

              #7
              Hi Kiera,

              The volume constraint doesn't find the missing piece, but if the open-ended surface aligns with one of the coordinate planes, it will calculate the volume of the defined geometry correctly. But, this will only be half of the actual volume (in the case of one symmetry plane). Regardless, the constraint should still find the correct pressure in the presence of symmetry planes.

              I hope that helps, but if not, can you please elaborate on your problem. I'm not sure what you mean by "it does not seem to be registering".

              Thanks,

              Steve
              Department of Bioengineering, University of Utah
              Scientific Computing and Imaging institute, University of Utah

              Comment

              • kdwyer
                Junior Member
                • Jun 2020
                • 20

                #8
                Hi Steve,
                Thank you so much for your reply! The open ended region in my geometry aligns with the X-Y plane yet I am still not able to get the enclosed volume. I attached an image of my model to make sure I am understanding you correctly.

                I defined the enclosed volume surface as the inner surface of the ellipsoid. I would be so appreciative if you have any insight! Thanks again so much!

                Kiera
                Attached Files

                Comment

                • maas
                  Lead Code Developer
                  • Nov 2007
                  • 3400

                  #9
                  Hi Kiera,

                  I've attached an example that show the "enclosed volume" plot variable. After you run this file, you can open the plot file in FEBio Studio, and look at the enclosed volume. You'll see the values are negative because I selected the interior surface (that has normals pointing inwards). In addition, it only calculates the volume of the half sphere, so to get the actual volume of the sphere, you would have to multiply by two. Let me know if this answers your question.

                  Best,

                  Steve
                  Attached Files
                  Department of Bioengineering, University of Utah
                  Scientific Computing and Imaging institute, University of Utah

                  Comment

                  • Lara
                    Junior Member
                    • May 2023
                    • 14

                    #10
                    Hello,
                    Does the enclosed volume plot variable take into account, if there is another body inside the selected surface or does it not "see" it?
                    If not does selecting the surface of the body inside help?

                    Thanks,
                    Lara

                    Comment

                    • maas
                      Lead Code Developer
                      • Nov 2007
                      • 3400

                      #11
                      Hi Lara,

                      The enclosed volume is only calculated based on the surface that you assign to it. It will not see anything else that might be inside the volume. I think that including the surface of the object inside should work, but let me know if you find any issues with that.

                      Best,

                      Steve
                      Department of Bioengineering, University of Utah
                      Scientific Computing and Imaging institute, University of Utah

                      Comment

                      • Lara
                        Junior Member
                        • May 2023
                        • 14

                        #12
                        Hello Steve,
                        unfortunately this didn't solve the problem, the enclosed volume is still the same. I tested with another model, where the two geometries are merged into one and saw the enclosed volume there was way lower. Because they are different materials and they seperate during the simulation, I can't use one geometry with a conforming mesh.
                        I want to apply a volume constraint to this enclosed volume, does this affect it in any way or can I select the surfaces there?
                        How can I control if the constraint volume takes the part inside into account?

                        What can I do about it?

                        Thanks,
                        Lara

                        Comment

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