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NDSolve Singularity

  • To: mathgroup at smc.vnet.net
  • Subject: [mg85504] NDSolve Singularity
  • From: Tara.Ann.Lorenz at gmail.com
  • Date: Wed, 13 Feb 2008 04:08:04 -0500 (EST)

Hello,

The following input for NDSolve is giving me a "singularity" error
(see error message below).  As a result, my system of equations is
being solved until the singularity at t=0.179 and not until t=30 as
desired.  Any suggestions on how to avoid this issue?  Thank you!

va = 4.71*y[t] - 246;
q = 6;
kl = 5;
kt = 40;
b = 760;
mrco2 = 250;
caco2 = 48 + 6*(paco2 - 40)/7;
paco2 = (b - 47)*r[t];
fico2 = 0.07;
grodinstime0to30 =
 NDSolve[{r'[
     t] == (1/
       kl)*((fico2*va + 8.63*q*(y[t] - caco2)/(b - 47) - r[t]*va)),
   y'[t] == (mrco2 + 10*q*(caco2 - y[t]))/(10*kt), r[0] == 0.058,
   y[0] == 0.533}, {r, y}, {t, 0, 30}]


ERROR MESSAGE:
NDSolve::ndsz: At t == 0.17926445744166167`, step size is effectively
zero; singularity or stiff system suspected. >>







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