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October 28, 2015, 03:16 |
erosion problem
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#1 |
New Member
libo
Join Date: Jan 2015
Location: China
Posts: 6
Rep Power: 11 |
Hi,
I`m doing sand erosion in 90 elbow. I have wrote an erosion rate UDF. Under the same condtions , two cases(don`t use udf and use udf) have many difference in the contours of erosion rate,however, the case don`t use udf looks more reasonable. I don`t know it has some wrong in my udf or the mathematics model unsuitable this case. Please give me some advices. Cheers! #include "udf.h" #include "math.h" float Z =3.434e+8; float C =2.17e-7; float A1 =5.4; float A2 =-10.11; float A3 =10.93; float A4 =-6.33; float A5 =1.42; DEFINE_DPM_EROSION(moshi, p, t, f, normal, alpha, Vmag, mdot) { real erosion; real a=alpha; real v=Vmag; real F_alpha; real V; real F; V=pow(v,2.41); F=A1*pow(a,1)+A2*pow(a,2)+A3*pow(a,3)+A4*pow(a,4)+ A5*pow(a,5); erosion=0.53*C*pow(Z,-0.59)*V*F; F_STORAGE_R(f,t,SV_DPMS_EROSION)=erosion; } Last edited by libo; November 3, 2015 at 21:51. |
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October 30, 2015, 08:44 |
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#2 |
New Member
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Hey Libo,
I can see you are making a UDF for the "E/CRC erosion model" which I have also played with before. I believe you have one major flaw in your UDF and that is how you are defining the "Brinnel Hardness" of your material (you have it as the variable Z =3.434e+8). From the paper I am assuming you got this equation from, it should be a value of 334.4 which represents Inconel 625. This was verified when I tested out the UDF model (one I created) with the paper's values experimental values. I would ALWAYS verify your erosion models with whatever lab/experimental data you can get your hands on. In my case, I was usually forced to mimic the models described in various papers and try to get as close as possible to the numbers. If that doesn't help, there are a few things you should do in Fluent to ensure you are getting a solution that is independent of the amount of particles injected into the model or how you are tracking them. Let me know if this helps. Cheers, Liam |
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October 30, 2015, 21:39 |
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#3 |
New Member
libo
Join Date: Jan 2015
Location: China
Posts: 6
Rep Power: 11 |
Dear Liam,
Thanks for your reply. I think you are right.I want to try how to write the UDF about erosion rate. So I found an equation from a paper(Comparison of computed and measured particle velocities and erosion in water and air flows), random define the value of Brinnel Hardness.I have felt I can get a result similar to the Fluent. I did't realize the value of Brinnel Hardness will bring great influence. Kind regards, LiBo |
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March 7, 2016, 05:14 |
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#4 |
New Member
Taz Hussain
Join Date: Feb 2016
Posts: 8
Rep Power: 10 |
Hi Libo,
I am doing something similar to what you are doing and was wondering if you could help me. Is your case a 3D case? and is the above udf all you needed to interpret into fluent to get erosion? sorry for all the questions! kind regards |
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March 7, 2016, 06:19 |
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#5 |
New Member
libo
Join Date: Jan 2015
Location: China
Posts: 6
Rep Power: 11 |
Hey Taz,
This a 3D case.I want to kown how to write the UDF to change ersion rate when I am read an article( Comparison of computed and measured particle velocities and erosion in water and air flows).Above UDF is all my needed to change the erion rate. I hope it can give you some help. Cheers, LiBo |
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