Re: NDSolve::ndsz question
- To: mathgroup at smc.vnet.net
- Subject: [mg63660] Re: NDSolve::ndsz question
- From: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>
- Date: Mon, 9 Jan 2006 04:48:43 -0500 (EST)
- Organization: The Open University, Milton Keynes, UK
- References: <200601070729.CAA06883@smc.vnet.net> <dpqk4s$2j6$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Pratik Desai wrote:
> Flip wrote:
>
>
>>Greetings, I'm trying to solve a differential equation but I'm getting
>>the following error:
>>
>>NDSolve::ndsz: At x == 18.84025621252942`, step size is effectively
>>zero; \
>>singularity or stiff system suspected
>>
>>I'm not sure how to deal with this--is there a way to allow smaller
>>step sizes? Here is my complete code:
>>
>>k := 400000000;
>>b := 0.0023;
>>epsR := 0.024;
>>solution := NDSolve[
>>{y'[x] == -k x^(-0.5) \[ExponentialE]^(-epsR x) (y[x]^2 - (b x^2
>>BesselK[2,x])^2),
^^^
Note that the whole expression {b x^2 BesselK[2, x]) is squared.
>>y[0.1] == b*BesselK[2,0.1]/(0.1)}, y, {x,0.1,5000}]
>>Evaluate[y[5000] /. solution]
>>
>>Any thoughts would be appreciated! Thanks,
>>Flip
>>
>>
>>
>
> I replaced all of your := with = and it seems to work fine,
>
I am afraid not
> In[222]:=
> $Version
> k=400000000;
> b=0.0023;
> epsR=0.024;
> solution=NDSolve[{y'[x]\[Equal]-
> k* x^(-0.5)* \[ExponentialE]^(-epsR x) (y[x]^2-(b
> x^2
> BesselK[2,x])2),y[0.1]\[Equal]b*BesselK[2,0.1]/(0.1)},y,{x,0.1,5000}]
^^^
since the expression is not squared as in the original equation.
> Evaluate[y[5000]/.solution]//InputForm
>
> Out[222]=
> 5.1 for Microsoft Windows (January 27, 2005)
>
> Out[226]=
> {{y\[Rule]InterpolatingFunction[{{0.1,5000.}},<>]}}
>
> Out[227]//InputForm=
> {1.887473651751147*^-9}
>
Best regards,
/J.M.
- References:
- NDSolve::ndsz question
- From: "Flip" <fliptomato@gmail.com>
- NDSolve::ndsz question