# Particle sliding down a plate

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 November 20, 2002, 14:41 Particle sliding down a plate #1 Darrell Anthony Egarr Guest   Posts: n/a I have modelled a volume of stationary fluid and are now injecting a single particle such that it reaches its terminal velocity before striking an inclined plate. In practice, the particle bounces a couple of times and then slides down the plate before terminating at an escape wall. Everything is fine except that the particle does not slide down the plate fast enough. I have been changing the coeficient of restitution but still cannot get the particle to slide fast enough. FLUENT assumes everything is smooth as far as I can tell and as far as I know they are, and I know that the particle properties are correct, density etc, as too are the fluid properties. I don't think it is possible to specify a coeficient of friction in FLUENT 6 or any roughness or coeficient of friction when the flow is not turbulent, but if you can, I don't know how. Does anyone have any suggestions, and if so, please let me know.

 November 21, 2002, 01:18 Re: Particle sliding down a plate #2 jit Guest   Posts: n/a If your boundary is a wall, then U can specify roughness height.

 November 21, 2002, 13:07 Re: Particle sliding down a plate #3 MissNancy Guest   Posts: n/a Any guideline you have to change the roughness height of a wall in fluent? By default it's zero, how do you know what the roughness would be? Darell, I suspect this (the slow motion of particle) near the wall is due to the a) wall treatment you are doing (standard, nonequilibrium..) b) The mesh near the wall. Is there any way, you can verify AND validate the flow near the wall? Nancy

 November 21, 2002, 16:43 Re: Particle sliding down a plate #4 Peter Attar Guest   Posts: n/a Out of curiousity is it necessary to model this using CFD? How complex is the flow? Could you not instead treat this as mechanics problem with the proper drag force acting on the particle,along with restitution coefficient and coefficient of friction? I am sure you have your reasons but I am just curious.

 November 22, 2002, 07:02 Re: Particle sliding down a plate #5 Darrell Anthony Egarr Guest   Posts: n/a How do you specify the roughness height? When I go into Define, Bounday connditions, wall, momentum, there is never the option to put the roughness in, no matter what shear condition i choose. DAE

 November 22, 2002, 07:03 Re: Particle sliding down a plate2 #6 Darrell Anthony Egarr Guest   Posts: n/a How do you specify the roughness height? When I go into Define, Bounday connditions, wall, momentum, there is never the option to put the roughness in, no matter what shear condition i choose. DAE

 November 22, 2002, 07:05 Re: Particle sliding down a plate #7 Darrell Anthony Egarr Guest   Posts: n/a I am doing this work to validate FLUENT for some work later on. The flow is not complex, as there is no flow. It is a mass of stationary fluid, with all temperatures in equilibrium. DAE

 November 24, 2002, 01:51 Re: Particle sliding down a plate #8 mahdi saniee nezhad Guest   Posts: n/a Dear sir I have a problem with this title. If it's possible for you please send me your received responses. Very thanks for your attention to my request. With the best regards. Mahdi saniee nezhad

 November 24, 2002, 11:43 Re: Particle sliding down a plate #9 Darrell Anthony Egarr Guest   Posts: n/a The only responses I have are onn this web-page DAE

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