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Old   May 18, 2005, 09:08
Default C_WALL_DIST
  #1
hbyann
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Hi,

I'm using Fluent 6, and I'm using DPM model and I would like to add a force on a particle, this force must be normal to the nearest wall. It seems that C_WALL_DIST gives the scalar value of this distance but do you know how to get the normal vector to the wall corresponding to C_WALL_DIST value ?

Thanks
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Old   May 18, 2005, 17:51
Default Re: C_WALL_DIST
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KP
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are u trying to implement wall forces?????>>>>>>>KP
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Old   May 19, 2005, 02:47
Default Re: C_WALL_DIST
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hbyann
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Yes I'm trying to implement a wall force acting on all the particles of the domain. So I need to get the distance from the wall but also the normal vector directed from the wall to the particle. It seems that with C_WALL_DIST it's impossible to get this last vectorial information. Any idea ?
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Old   May 19, 2005, 15:34
Default Re: C_WALL_DIST
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KP
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U are correct it is not impossible but it is hard.I too tried to implement it but it could not be done. Which formualtion u are tring to implement??? Moragas or Antals or Laheys??? The reason of it beign so hard is FLUENT is an unstructured code and in that case information pertianing to the first cell next to the wall is only avaialble and rest all cells information are beign interpolated using that information. Hence u cannot implement wall forces with that ease. Am easy way to comeplement wall forces is use suiatble lift forces. There are several lift force formualtions for lift forces and one of them is Mclauglins model however it also might not be easy to work with.....further discussion in line with ur problems to wall forces can be directed to me at kp@dal.ca. ************************************************* PS: If u still feel that u require to implement wall forces then u should look for a formualtion in which the formulation is not local but ....it is hard to find that kind of an expression... let me know how it goes KP

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Old   May 20, 2005, 02:25
Default Re: C_WALL_DIST
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hbyann
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the formulation is Antals one. Thanks I'll let you know how it goes
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Old   May 20, 2005, 09:38
Default Re: C_WALL_DIST
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KP
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I tried Antal and Moragas but it does not work. Can I know ur geometry? What type of system u are working with (air:solid)?? Wall forces may not be important for low density difference however they might be looked upon as an important term in momentum equation for highe density difference systems. They help in resolving good peaks near the wall but the same can be acheived by lift forces. I acheived excellent results with the use of lift forces but the positioning of peaks was not that good when compared with experiements. For particles u may try a lift coeff of 0.25 or 0.05 and see how it goes. U can slo try a negative sign with the coefficient. KP
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