# surface reaction rate with udf

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 December 21, 2009, 08:26 surface reaction rate with udf #1 New Member   Gerhard Selle Join Date: Aug 2009 Posts: 6 Rep Power: 7 hello everybody i'm facing a problem getting the surface reaction rate after my simulations. i wrote an udf for the reaction rate, but fluent is not able to compute the reaction rate. the output says zero everytime. do anyone of you know how to get the surface reaction rate, so i can plot it? thanks for your help

 December 21, 2009, 19:24 Surface Reaction Rate #2 Member   Krishna Join Date: Oct 2009 Posts: 34 Rep Power: 7 Please post the UDF that you have written. Thanks

 December 22, 2009, 00:14 #3 New Member   Gerhard Selle Join Date: Aug 2009 Posts: 6 Rep Power: 7 oh this is the udf: #include "udf.h" #define R 83140000 #define p 1013250 #define pi 3.14159 DEFINE_SR_RATE(my_rate,f,t,r,mw,yi,rr) { Thread *t0 = t -> t0; cell_t c0=F_C0(f,t); real c3h8 = yi[0]; real o2 = yi[1]; real co2 = yi[2]; real h2o = yi[3]; real n2 = yi[4]; real rho_w = 1.0, sd = 2.49e-9, T_w; real o_s,o_vac; real xc3h8 = 1.0, xo2 = 1.0; real tn,Tg,Ea3, Ea4, Ea5; real rA3, rA4, rA5,rk3, rk4, rk5; real ro,rate; T_w = F_T(f,t); rho_w = C_R(c0,t0)*C_T(c0,t0)/T_w; c3h8 *= rho_w/mw[0]; o2 *= rho_w/mw[1]; co2 *= rho_w/mw[2]; h2o *= rho_w/mw[3]; n2 *= rho_w/mw[4]; /* Mole fraction of CH4 and O2 */ xc3h8 = c3h8/(c3h8+o2+co2 +h2o+n2); xo2 = o2/(c3h8+o2+co2 +h2o+n2); Tg = C_T(c0,t0); tn = T_w/300; /* Activation energies */ Ea3 = 0.0; Ea4 = 0.126*tn*tn*tn*tn - 1.849*tn*tn*tn + 9.124*tn*tn - 13.253*tn + 23.903; Ea5 = 4.0; //7.3 + 1.9*tn; Ea3 *= 4184e7; Ea4 *= 4184e7; Ea5 *= 4184e7; rA3 = (0.0542)*pow(tn,0.766); rA4 = (8.41e12)*pow(tn,-0.796); rA5 = (0.06)*pow(tn,0.154); rk3 = (rA3/(sd*sd))*sqrt(R*T_w/(2*pi*mw[1]))*(p/(R*T_w)); rk4 = (rA4/sd)*exp(-Ea4/(R*T_w)); rk5 = (rA5/(sd*sd))*sqrt(R*T_w/(2*pi*mw[0]))*(p/(R*T_w))*exp(-Ea5/(R*T_w)); ro = sqrt(rk3*xo2/rk4); o_s = ro/(1+ro); o_vac = 1-o_s; rate = rk5*xc3h8*(sd*sd)*pow(o_vac,2); if (STREQ(r->name, "reaction-1")) *rr = rate*pow(10,1)*1.7; // mol/cm2s --> kgmol/m2s * effectiveness /* else if (STREQ(r->name, "reaction-2")) *rr = -2*rate; else if (STREQ(r->name, "reaction-3")) *rr = rate; else if (STREQ(r->name, "reaction-4")) *rr = 2*rate; */ } weilin likes this.

 December 26, 2009, 10:34 #4 New Member   Gerhard Selle Join Date: Aug 2009 Posts: 6 Rep Power: 7 does nobody has a solution or suggestions? the udf is correct, but i can't display the surface reaction rate, although fluent is calculating it.

 January 29, 2010, 13:53 use "User Defined Memory" #5 New Member   Mi Hyun Kim Join Date: Mar 2009 Posts: 1 Rep Power: 0 It doesn't work to display the surface reaction rate in Contours panel under Reactions directly. You can save the reaction rate in "User Defined Memory", then you can see the reaction rate in Contours panel under -> Contours of ->User Defined Memory -> User Memory #.

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