# erosion problem

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 October 28, 2015, 04:16 erosion problem #1 New Member   libo Join Date: Jan 2015 Location: China Posts: 6 Rep Power: 4 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 22:51.

 October 30, 2015, 09:44 #2 New Member   Liam Join Date: Sep 2013 Location: Calgary, Alberta Posts: 19 Rep Power: 6 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

 October 30, 2015, 22:39 #3 New Member   libo Join Date: Jan 2015 Location: China Posts: 6 Rep Power: 4 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

 March 7, 2016, 06:14 #4 New Member   Taz Hussain Join Date: Feb 2016 Posts: 8 Rep Power: 3 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

 March 7, 2016, 07:19 #5 New Member   libo Join Date: Jan 2015 Location: China Posts: 6 Rep Power: 4 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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