[mmd96]

Hi, I'm trying to simulate the motion of a sphere when we have gravity and buoyancy force by 6DOF and Dynamic Mesh in fluent.

My Fluent settings are
Density-Based
Sst k-omega model
Transient

I have a 3d domain that contains water (density is 998.2 kg/m3) and a sphere (radius is 1m and density is 500 kg/m3). I set gravity -9.81 m/s2 in y-direction. In this case, buoyancy force is greater than gravity force so the sphere ought to go up (fluent force plot shown positive value) but the sphere drops. In every time step convergence is ok(less than 50 iterations).

when I set the density of sphere 100 kg/m3 forces to go to infinity and it's given me floating point exception error.
For both cases force plot in y-direction is attached.

Fluent can't determine buoyancy force?

Any help regarding this problem is highly appreciated.
Regards

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[LuckyTran]

1. Buoyancy force and gravity force are the same thing
2. Your sphere has a higher density (1000 > 998), it should drop.


Working as intended

[mmd96]

Originally Posted by LuckyTran

1. Buoyancy force and gravity force are the same thing
2. Your sphere has a higher density (1000 > 998), it should drop.


Working as intended

Excuse me density of sphere is 500 and 100