UDF Geometry Connectivity


    For my current PhD research project, I my ultimate aim is to conduct a transient simulation with a time-varying domain. As I am a novice Fluent user, I have devised a series of tasks for myself to build up to the construction, proper execution, and analysis of such a model. While working through the tutorials that are available to Fluent users, I have gleaned that I will likely need to use UDFs to perform such a feat.

    Herein lies my question, for the most recent “build up” task I’ve constructed for myself, I would like to run a transient fluid flow simulation through a Converging-Diverging Nozzle where the “height” of the throat changes in time. In the sketch I constructed for the geometry, I was able to successfully change this parameter during a parametric study. However, what I’m less clear on is whether it’s possible to instruct a UDF to change this specific dimension during my simulation. Do you know whether it is possible to do this, and if so which MACRO I ought to use in the associated UDF?

    Thinking a bit down the line, the models I will ultimately run are to simulate a complete cardiac cycle (heart beat). For my application, we will not need to utilize Two-Way FSI since we are taking domains from an array of patient populations, and we wish to simulate the dynamics within a specific individual. Do you have any recommendations/best practices for how to use a new geometry file at each time step, or possibly have a few geometry files that the meshing components of ANSYS is able to interpolate between when appropriate? Any suggestions and/or will be greatly appreciated.

    If my question is not clear, please let me know what I can do to help delineate my issues further. Thank you in advance for your assistance and I look forward to hearing back from you.




  • RobRob UKForum Coordinator

    OK, the method for that is relatively straightforward, the execution much less so.

    Parameters are designed to allow multiple designs to be evaluated, typically for optimisation of systems/devices. In your case you have a known shape change with time and need to replicate that. Read up on moving deforming mesh, UDFs and mesh replacement. I think you'll need all three during the project. There are courses on the Ansys Campus, (https://www.ansys.com/services/training-center) but you'll need a subscription for that.

    Note, please do a very careful literature review as I've answered questions like this before (can't remember, or in some cases say for whom) which suggests it's already been done: you may not be extending the bounds of knowledge sufficiently for a PhD.

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