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July 27, 2009, 14:25 
UDF Radiation model for combustion

#1 
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siva kumar
Join Date: Jul 2009
Posts: 13
Rep Power: 8 
Hi,,,This is siva kumar from IIT MADRAS....while am interpret my udf the error is showing like.....
Error: FLUENT received fatal signal (ACCESS_VIOLATION) 1. Note exact events leading to error. 2. Save case/data under new name. 3. Exit program and restart to continue. 4. Report error to your distributor. Error Object: () this error is coming in my fluent model when i interpret the source code as shown in below....fuel is methane #include "udf.h" DEFINE_SOURCE(energy,c,t,ds,eqn) { /*FILE *fp;*/ real source,tep,sigma,Pamb,tamb; real MW[18]; real Xh2o,Xco,Xco2,Xch4,ph2o,pco,pco2,pch4; real MWmix,sum=0; real kapa,absh2o,absco,absco2,absch4; real a0,a1,a2,a3,a4,a5; real b0,b1,b2,b3,b4,b5; real c0,c1,c2,c3,c4; real d0,d1,d2,d3,d4; int i; /*fp=fopen("properties.txt","w");*/ tep=C_T(c,t); MW[0]=1; MW[1]=32; MW[2]=17; MW[3]=16; MW[4]=2; MW[5]=18; MW[6]=33; MW[7]=28; MW[8]=44; MW[9]=16; MW[10]=15; MW[11]=14; MW[12]=30; MW[13]=29; MW[14]=31; MW[15]=34; MW[16]=13; MW[17]=28; sigma=0.000000056697; Pamb=1.0; tamb=298.0; a0=18.741; a1=121.310; a2=273.500; a3=194.05; a4=56.31; a5=5.8169; b0=0.23093; b1=1.12393; b2=9.4153; b3=2.99880; b4=0.51382; b5=.000018684; c0=6.6334; c1=0.0035686; c2=0.000000016682; c3=0.00000000025611; c4=0.000000000000026558; if(tep<=750) { d0=4.7869; d1=0.06953; d2=0.000295775; d3=0.000000425732; d4=0.000000000202894; } else if(tep>750) { d0=10.09; d1=0.01183; d2=0.0000047753; d3=0.000000000587209; d4=0.000000000000025334; } for(i=0;i<18;i++) { sum=sum+C_YI(c,t,i)/MW[i]; } MWmix=1/sum; Xh2o=C_YI(c,t,5)*MWmix/18; Xco=C_YI(c,t,7)*MWmix/28; Xco2=C_YI(c,t,8)*MWmix/44; Xch4=C_YI(c,t,9)*MWmix/16; ph2o=Xh2o*Pamb; pco=Xco*Pamb; pco2=Xco2*Pamb; pch4=Xch4*Pamb; absch4=c0+(c1*tep)+(c2*pow(tep,2))+(c3*pow(tep,3)) +(c4*pow(tep,4) ); absco2=a0+(a1*(1000/tep))+(a2*pow(1000/tep,2))+(a3*pow(1000/tep,3 ))+(a4*pow(1000/tep,4))+(a5*pow(1000/tep,5)); absco=d0+(d1*tep)+(d2*pow(tep,2))+(d3*pow(tep,3))+ (d4*pow(tep,4)) ; absh2o=b0+(b1*(1000/tep))+(b2*pow(1000/tep,2))+(b3*pow(1000/tep,3 ))+(b4*pow(1000/tep,4))+(b5*pow(1000/tep,5)); kapa=(absch4*pch4)+(absco*pco)+(absco2*pco2)+(absh 2o*ph2o); source=(4*sigma*kapa*(pow(tep,4)pow(tamb,4))); /*fprintf(fp,"%f%f%f\n",tep,source,MWmix);*/ ds[eqn]=0; return source; } why the error is coming i don't know please help me?????? Last edited by shshiva17; July 28, 2009 at 09:39. 

July 29, 2009, 10:44 

#2 
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Micael Boulet
Join Date: Mar 2009
Location: Quebec, Canada
Posts: 95
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Hello Siva,
Notice the space into your variable: kapa=(absch4*pch4)+(absco*pco)+(absco2*pco2)+(absh 2o*ph2o); Delete that space and it should be ok: kapa=(absch4*pch4)+(absco*pco)+(absco2*pco2)+(absh2o*ph2o); Have a good day. Micaël 

July 29, 2009, 10:59 
Thank u very much Micaël

#3 
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siva kumar
Join Date: Jul 2009
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i willl try that.....thank u very much for ur reply...keep in touch with me,,,,,


July 29, 2009, 12:28 
hey Micaël

#4 
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siva kumar
Join Date: Jul 2009
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i have tried but it is not working man,,,,,???


July 29, 2009, 18:34 

#5 
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Micael Boulet
Join Date: Mar 2009
Location: Quebec, Canada
Posts: 95
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Sorry, I had not tried the UDF, only saw this space and reported it. Now I can see too that there is another problem, more difficult to find.
That is not clear to me, but the problem seems to come from C_YI(c,t,i). Using only a Species Transport model, I can successfully use your UDF. Which model do you use? Someone reported problem using C_YI(c,t,i) with a pdf combustion model: http://university.fluent.com/forum/v...814ae1a27f690d Hope this can helps. Micaël 

July 30, 2009, 01:59 
Micaël

#6 
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siva kumar
Join Date: Jul 2009
Posts: 13
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hi,,,,miceal,,,am using species transport model .......how can it be solved...?
see miceal am not using pdf combustion model am using only species transport model......??? 

July 30, 2009, 10:19 

#7 
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Micael Boulet
Join Date: Mar 2009
Location: Quebec, Canada
Posts: 95
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Here is what I did:
I enabled Species Transport. I choose "mixturetemplate" in the Mixture Material dropdown list. In the Materials panel, I added arbitrary fluid materials in that mixture up to 18. Finally, I hooked the UDF in the boundaries panel, adding energy source in the fluid zone. I did few iterations without bug. Do you use it that way? If you have less then 18 species defined in your mixture there is a bug here in your code: for(i=0;i<18;i++) { sum=sum+C_YI(c,t,i)/MW[i]; } You can easily see how many species you have: Define > Models > Species > Transport & Reaction Just look at the right of "Number of Volumetric Species" 

July 30, 2009, 10:49 

#8 
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siva kumar
Join Date: Jul 2009
Posts: 13
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u have run that file...
did get running the fluent with out error....but mine is error is coming again,,,??? 

July 30, 2009, 11:33 

#9 
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Micael Boulet
Join Date: Mar 2009
Location: Quebec, Canada
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You have defined 18 species in your mixture?
If yes, then I don't know what is the problem. 

July 30, 2009, 12:03 
miceal..

#10 
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siva kumar
Join Date: Jul 2009
Posts: 13
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hi miceal my problem is 2 step methane combustion....total products are 6 how can i give 18 products ,,,,
i think we need to change the udf into 6 species,,,,,,isn't it??? 

July 30, 2009, 12:58 

#11 
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Micael Boulet
Join Date: Mar 2009
Location: Quebec, Canada
Posts: 95
Rep Power: 9 
Did your write this UDF yourself? What it does? What is "MW"?
I thought you have 18 species because of this: for(i=0;i<18;i++) { sum=sum+C_YI(c,t,i)/MW[i]; } i in C_YI(c,t,i) is species index (integer) What this loop intend to do? Since you have 6 species, now it is clear to me that the problem is there. Don't give up. 

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