0 Replies Latest reply on Apr 8, 2012 5:05 PM by David Faunce

    Boundary Conditions or Goals

    David Faunce

      I've been working on a project to redesign a flying disc (aka frisbee). I modeled the OEM and started making changes to it. I've only made slight changes, yet my results seem to differ drastically. I'm wondering if my boundary conditions are not setup correctly.

       

      the setup is enclosed in a box with lids on opposite ends. I selected the surface wall (shown in the pic) and gave it a Inlet Velocity of 15 m/s (uniform). The opposite side has an environmental pressure (at atmosphere). The disc is rotating at 38 rad/s. Obviously the fluid is air. There are no other conditions involved.

       

      Theoretically the dynamic pressure is supposed to be highest directly underneath the frisbee and lowest directly above the frisbee but you can see that the dynamic pressure is lowest above and below the frisbee (blue). Plus, common sense tells me that we shouldn't be seeing 9000 inH20 pressure involved in this scenario.

       

      I also tried the following:

      Replaced the 15 m/s velocity with Volume Flow Rate of 4 m^3/s (the area of the wall will give it an equivalent 15 m/s velocity). I also reversed them to where the inlet was pressure and the outlet was flow.

       

      I was wondering if I need to redefine my BCs and maybe set a GOAL for a max velocity?? What am I doing wrong here?

       

      Also, the OEM will NOT run with Goals, however the new design will ONLY run with goals. I keep getting a solver error during calculations (the pressure just shoots up off the charts in both scenarios).

       

      Can someone shed some advice on how this needs to be setup?

       

      Default (Dyn-Pressure)_1.jpg

       

       

      -David