I made a falling-ball model using 6DOF in Fluent.
I tried two ways to define the properties of the ball:
1. UDF:
Mass was defined. Ixx, Iyy, Izz and other properties were not mentioned
2. Options->Six DOF(checked) and implicit update(checked)->Settings...:
Create a property giving mass and all value of Inertia Tensor are 0.
Either way would result in an message when calculating:
Info: 6DOF: can't compute angular acceleration.
Check moments/products of inertia.
I don't know what happened.
The moments/products of inertia are calculated by Fluent solver.
The value was not given in the first method, but the value are 0 initially in the second method.
Why does it said "6DOF: can't compute angular acceleration."?
It seems that the reason is "implicit update".
Then, how to fix it?
Method 1: Uncheck "implicit update", modify the URF and mesh.
However, the message cold still show up. Maybe the Izz should be given a value?
Method 2: Keep "implicit update", and then...I don't know, so far.
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OK...the reason is that if moment of inertia is not given a value, the angular momentum can;t be calculated.
This has nothing to do with implicit update. You need to specify inertia tensor to compute the angular acceleration.
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