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-   -   Settling Velocity - FLUENT Discrete Phase Model (https://www.cfd-online.com/Forums/fluent/29441-settling-velocity-fluent-discrete-phase-model.html)

 Lily March 2, 2002 10:08

Settling Velocity - FLUENT Discrete Phase Model

I am trying to simulate, using FLUENT 5.4's Discrete Phase Model, the terminal settling velocity of a single spherical particle. The fluid velocity is zero in all direction. I then compare the terminal settling velocity to that calculated using Stoke's equation : i.e. v_t = (rho_p - rho_f)*g*D_p^2 /(18*mu)

The simulated terminal settling velocity matches the velocity calculated from Stoke's equation for small particles (less or equal than 10 micron), but diverges when the particle size is larger than 100 micron. For example, the terminal settling velocity for a 2600 kg/m3, 100 micron diameter particle is -1.535e-01 m/s (from FLUENT) and -8.69e-03 m/s (from Stokes' equation). I have tried using smaller time step, but to no avail.

Am I missing something blantantly obvious ? Any advice /suggestion are most welcomed.

 Lily March 2, 2002 10:36

Error

Sorry

"100 micron diameter particle is -1.535e-01 m/s (from FLUENT) and -8.69e-03 m/s (from Stokes' equation)"