# Particle Trajectory calculation

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 February 17, 2001, 09:12 Particle Trajectory calculation #1 yueroo Guest   Posts: n/a Sponsored Links Hi: I use FLUENT 5.5 's Discrete Phase Modeling to simulation particle and liquid flow in 180degree bend. This is laminer flow. I wnat to get accuracy prticle residence time. I found when I control the integration time step size from big time step size to small time step size , some particle will get unstable residence particle time . I put particle near wall ,I will get unstable residence particle time when integration time step size from big time step size to small time step size When I put particle far away wall , The result is stable. Can someone have some experience when you use Particle Trajectory calculation THANKs!!

 February 17, 2001, 15:41 Re: Particle Trajectory calculation #2 K.T. Guest   Posts: n/a Do not use time step size for RTD. Instead, use the integration factor (?) in the same box. Use 30 - 40 to ensure that each cell is properly resolved with enough integration steps.

 July 13, 2009, 13:32 #3 New Member   christian paul Join Date: Jul 2009 Posts: 2 Rep Power: 0 Hi all, I need some help with VOF modeling in fluent. We have a 2D Horizontal micro channel that is 5e-05 meters in diameter and 7.5e-04 in length and we have the primary stage set to water and the secondary stage set to a type of oil found in the fluent database. We first ran a simple flow problem with just water. We saved those results and used them when we initiated the Volume of Fluid. Here are our paramters. Solver: pressure based, 2D, absolute formulation, implicit formulation, unsteady time Multiphase: Explicit VOf scheme, implicit body force with two phases. Material: Water-liquid, Gas-oil liquid operating conditions: Left as is, we want to know if we should change this Boundry condition: Inlet velocity 0.001 m/s pressure is 0, should we change this? Solve> controls Equations are flow and volume fraction Pressure velocity coupling- simple pressure: Presto Momentum: first order upwind Volume fraction: geo-reconstruct We would also like to know what the benifit of Patch is, and if it is necessary in our case. The main problem we're having is that the bubbles are the same diameter as the channel, we would like to know if there is any way we can control the amount of oil that goes into the channel so our oil droplet would be roughly 10 microns. Also if there is a way to measure the forces acting on the bubble. thanks

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