[gomane8]

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

[valgrinda]

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

[gomane8]

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

[phire]

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.

[gomane8]

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

[phire]

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