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[usama]

[usama]

The question is here nDear Ansys Community, hope you shall be in good health. i need help because i am facing some problem regarding droplet impact on the structured surface. ni am doing a 3D simulation for analysis of droplet spreading behavior on the structured surface. ni have written the udf is attached in the pictures. nTo get spreading behavior/spreading factor/liquid-air interface the nC_CENTROID(e,c0,t0);nr[i]=e[0]; nis used in the udf.n1) the problem i am facing right now when the droplet hits the structured surface the fluent crashes every time.n2) if I remove that command mentioned above in the udf the fluent runs perfectly.ncan you help me to fix this issue?nI need to use this command to get the spreading factor of the droplet impact.ni also attached the udf pictures and geometry pictures in the form pictures.nplease reply urgently.ni have a due date of the project in my University.n

[Rob]

Are you looking at DPM droplets or small amounts of VOF? nThere are the wall film models, and if you're wanting the surfaces you need to look at a surface thread (F...) rather than the cell thread (C...). n

[usama]

It is actually the large droplet that is spreading, I tried taking F_CENTROID also in that case also fluent is crashingn

[usama]

It is actually the large droplet that is spreading gently on the structured surface with 0.1m/s velocity (low weber number), I tried taking F_Centroid but the in that case also ansys fluent is crashing.n

[usama]

Are you looking at DPM droplets or small amounts of VOF? There are the wall film models, and if you're wanting the surfaces you need to look at a surface thread (F...) rather than the cell thread (C...).https://forum.ansys.com/discussion/comment/110312#Comment_110312

It is actually the large droplet that is spreading gently on the structured surface with 0.1m/s velocity (low weber number), I tried taking F_Centroid tn

[usama]

it is droplet is gently hitting the surface with 0.1 m/s. In the case of taking F_Centroid also it is crashingn

[usama]

Thanks rob on coming my post..nits a long time not in touch with you hope you are fine.nstay safe nUsamann

[Rob]

I'm good thanks, hope all is well with you. I've also verified your account to try and stop the filters eating all of your posts.I'm not sure why you're getting the problems, but suspect you're trying to store data or do a calculation in the wrong form: not all data is available on F_ or C_ so you may have broken something. What I would suggest is having a look at the VOF to wall film models, that may mean you don't need a UDF. n

[YasserSelima]

what is r and why it's defined [ND_ND]?nDo you receive sigsegvnnadd this before the two lines ... nMessage(i = %d, i);n

[usama]

nHi Selima,n I am getting 999999: mpt_accept: error: accept failed: No errornbefore it is getting crashed for each face loop all the cells having volume fraction interface will get stored in r[ND_ND] and then I am using for loop to get the maximum value stored in r array to get the spreading factor (i.e. maximum distance of cell having vof interface)n

[usama]

HI Rob,n I have used VOF multiphase along with EWF activated with initial boundary conditions on the wall of impingement . I hve then initialized the solution and then went to EWF tab left the default and given water for film and surface tension coeff 0.072 and max thickness to 5mm and then clicked on initialize tab on EWF tab. But i am getting maxcfl 0 even after droplet impinged on walln

[YasserSelima]

ND_ND is 2 dimensions for 2D simulations and 3 dimension for 3 D simulation. so, with the fourth value you get sigsegv. Declare r with a dimension larger than what you expect ... and initialise it with zeros, so when you get the maximum, you get an actual maximumn

[Rob]

There's a transition depth so it the VOF level is high enough we resolve the film, as the depth decreases we switch to the film models. n