Re: Avoiding divide by zero error in NDSolve

• To: mathgroup at smc.vnet.net
• Subject: [mg62467] Re: [mg62443] Avoiding divide by zero error in NDSolve
• From: <bsyehuda at gmail.com>
• Date: Fri, 25 Nov 2005 02:25:09 -0500 (EST)
• References: <200511241133.GAA29288@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```I already posted you an answer on the students forum
yehuda

>
> Hi all,
> I am having this problem of mathematica not letting me specify the exact
> intial values to a differential equation set. a simple example follws
>
> Simple Mass Balance Equation set in Chemical Systems.
>
> Nsp = 5;
> k1 = 100;
> For[i = 1, i < (Nsp + 1), i++, k2[i] = k1/Nsp];
> eqn1 = {D[M[t], t] == k1, M[0] == 0};
> eqn2 = Table[{D[M[t]y[i][t], t] == k2[i],y[i][0] ==k2[i]/k1},{i,Nsp}];
> var1 = Table[y[i][t], {i, Nsp}];
> var2 = Join[{M}, var1];
> sol=NDSolve[{eqn1,eqn2},var2,{t,0,10}]
>
> Mathematica refuses to solve this system showing error messages of
> encountering 1/0. If i change the initial condition of M to some
> arbitrary nonzero value, it is able to solve this system although now
> the set of equations are practically meaningless for me. Is there any
> way i can retain the meaning of my equations and still get them solved
>
> Thanks & Happy thanksgiving,
>
>

```

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