# Help : scour around piers with eulerian!!urgent

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 May 24, 2011, 14:17 Help : scour around piers with eulerian!!urgent #1 New Member   gomane8 Join Date: Mar 2010 Location: ALGERIA Posts: 9 Rep Power: 6 hi first iam a Phd student, iam working on scour around piers! i have start (to familiris with fluent) to simulate the free surface flow! VOF !! just general cases!! and after that i have begin with the eulerian for that i have meshed a 3D rectangular domain with hex+cooper! after that i have switch to fluent: i use a wter velocity IN (there is a domaine under that =the sand) and a pressure outlet i have set the second phase as sand and For the other paramétr, i have: granular visco+ solid pressur = saymlal & obrein granular bulk+radial distrubution=l'un & al frictional visco=shaffer granular T°=algebric iam using the K-epslon+RNG+enabl swep the velocity is about 0.5m/s and for the URF: all default for initialisation i use the Velocity of water and then i mark the region of sand after that i patch that domain with Volume fraction of sand = 1! i have check the min area = 10^-7 so the time step size = sqrt(min A)/Velocity... the problm that i have not get a logik deformation of the sand surface!!! i dont know why!!! so i need your help! and for the time step size!!do iam wright??? any help from you is very apreciate!! abdellah Last edited by gomane8; May 25, 2011 at 12:57.

 June 10, 2011, 04:09 local scour CFD #2 Member   Hans Bihs Join Date: Jun 2009 Location: Trondheim, Norway Posts: 34 Rep Power: 8 Hei, sediment transport with a fraction function for the sediment transport sounds tricky, how do you incorporate the bedload and suspended load formulas? Here a link to a thesis where a 3D CFD code was used with the "standard" bedload/suspended load formulation: https://sites.google.com/site/reef3d...attredirects=0 Cheers Hans

 June 10, 2011, 06:29 RE- Hans #3 New Member   gomane8 Join Date: Mar 2010 Location: ALGERIA Posts: 9 Rep Power: 6 thnx Hans first let me tell you that when i was a beginner in fluent i thought that, fluent can do evry thing!! but after some research ( it takes a lot of time), i had inderstood that fluent can not do evry thing!! and i have to tell him about the way of interaction between phases ( water, sand)!!! here i must use the UDF ( User difined function)! in that UDF ( it's a C Program) i introduce the formula (bed load and critical shear stres , ............) for now iam in that step, i try to learn about UDF, ( to learn from UDF's) !!! thnx for the thése that you have send to me!! and i apreciate any help or collaboration between us!! abdellah

 June 21, 2011, 12:14 Hi guys #4 New Member   Olusogo fire Join Date: Jun 2011 Posts: 9 Rep Power: 6 I am currently working on scour under pipelines but it is in 2D. I intend to use the Eulerian multiphase model. I am hoping I wont have to use UDF to specify the sediment transportation. ALso in the journal i saw, they didnt say anything about using UDF. I will really appreciate any contribution because I have a limited time to submit my thesis.

 June 21, 2011, 16:34 Re : scour arounde pipe #5 New Member   gomane8 Join Date: Mar 2010 Location: ALGERIA Posts: 9 Rep Power: 6 THX for your contribution. well i have take a look on a paper about scour around pipe line (i dont remeber the title)!! and i am sure that you have to use a UDF to describe the interaction between the two phases ( sand and water)! fluent can not consider the sand as solide!! iam trying to write my udf and i still found dificulties in that, because it's in C!! the mechanisme of scour in the two cases (pipe line scour and bridge scour) is the same! and i think the same UDF can do it. My advice to you is as fellow: * you must have a theorical idea about (how the erosion start) * take a look on the DPM erosion UDF! * you have to introduce the shear stress condition of erosion ( when a particle mouve?======= at what shear stress?) i hope it helps Abdellah

 July 6, 2011, 20:52 figured out to model the erosion #6 New Member   Olusogo fire Join Date: Jun 2011 Posts: 9 Rep Power: 6 U dont need UDf to model the erosion unless u want to consider other parameters. I just modeled the erosion under a pipeline but I am not getting the right result but i feel i am getting close since i can see the soil move under the pipe. About fluent seeing the soil as a solid: u only specify the properties of the soil and take it as a fluid since in eulerian multiphase model, the sediment and the fluid are solved as continuum. For further info, try read about the eul;erian multiphase model. Just need to solve the granular temperatue equations and the continuum equations which can be done using some settings under fluent. Right now, I am trying to create the log profile of the velocity for the velocity inlet using UDF and I really need help and suggestions

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