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Errors Using SDOF with Object of Small Mass (10^-12 kg)

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Old   June 26, 2020, 12:55
Default Errors Using SDOF with Object of Small Mass (10^-12 kg)
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I am trying to use the 6-DOF solver on an object with very small mass (on the order of 10^-12 kg), but am getting unreasonably large displacements and velocities of the object compared to experimental values. I have tried reducing the time step (down to 10^-10 sec/step), but still this problem persists. Looking at the Ansys Theory guide, I imagine this is occurring due to the fact that Ansys calculates acceleration (and therefore velocity) by summing forces over an object and dividing by the mass (which here is very small). I am wondering if anyone has come across similar problems using very small masses with the SDOF solver, and if so, how they have overcome them.

On a related note, does anyone know what forces Ansys sums for the SDOF solver, specifically for laminar flow in a non-Newtonian fluid? Perhaps a force relevant for my simulation is not accounted for in what Ansys solves, and as a result I could externally add that force onto the object in a UDF to generate the correct net force profile.

Thank you for the help!
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6dof, error, fluent, sdof

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