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August 24, 2016, 04:03 
modeling multiphase flow in stone trap

#1 
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faraz
Join Date: Aug 2014
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Hi
I want to model a multiphase flow(solidliquid) in a stone trap,i have problem with reverse flow,when fluent starts iteration,immediately appear a massage that says(revered flow in ... faces) can any body please help me to solve this problem? the goal is achieving contours for velocity difference(velocity magnitude),pressure and distribution of solid phase here are the problem conditions: laminar flowmultiphase(mixture)phase1(crude oil),phase2(stone&sand)granular with 0.005 diameter for stone &sandvelocity inlet boundary condition for inlet of flow and pressure outlet for outlet.there is gravityand the operating pressure is 20barthe inlet velocity is 0.000347(m/s) the geometry of problem has been attached it should be noted that as you can see in picture there are 125 slots in the inner pipe 

August 30, 2016, 22:57 

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The explanation below assumes you've defined your exit properly as a pressure outlet (which it appears you have). If you've defined it as a pressure inlet, which is perfectly valid, you'll always have this error as fluent is calculating a negative mass flow. A negative mass flow in or a positive mass flow out are the same.
Reverse flow isn't a critical error. Think about pouring water/beer/soda out of a bottle: even though the general trend is for all the water to exit the bottle, there are periodic "back flows" of air into the volume to make up for lost volume. Your simulation, either naturally or through a poor initialization condition, may have backflow in early iterations/time steps as the solver "works out" your bad guess. If your area of interest will be disturbed by the backflow, extend your exit domain so that the backflow doesn't influence your solution. If you *know* the backflow condition (which, presumably, is pure oil), simply set the back flow volume fraction of your stones to 0. Let the solution converge. If it converges deeply, you may simply have backflow. Again, not a problem. If seeing the message bothers you, in the text interface type: solve (hit enter), set (hit enter), flowwarnings (hit enter), no (hit enter). This will turn the message off. Bottom line: let the solver work for a while. If it still shows backflow, consider growing your geometry so the backflow doesn't change your answer. ComputerGuy Quote:


August 31, 2016, 04:13 

#3  
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faraz
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Quote:
thanks for your help 

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granular, laminar, multi phase flow 
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