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Student Support Forum: 'Why am I getting this error when using NDSolve?' topicStudent Support Forum > General > Archives > "Why am I getting this error when using NDSolve?"

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Katie
09/12/05 9:16pm

I am attempting to solve a system with 3 pde's and I keep getting this error even though I think all of my equations have independent variables:

NDSolve::dvnoarg: The function v appears with no arguments.

If anyone could find the mistake in my code I would really appreciate it. C,V, and R are the dependent variables, and t (time) and x(distance-does not depend on time) are the independent variables.

Thank you for any assistance you can provide me.


\!\(\(rRHS\ = \ \(d\_r\) D[r[t,
x], {x, 2}] + β \((1 - \((r[t, x] - r\_base)\)/\((k\_r -
r\_base)\))\) \((r[t, x] - r\_base)\);\)\[IndentingNewLine]
\(vRHS\ = \ \(d\_v\) D[v[t, x], {x, 2}] - σ\ v[t, x]\ -
η\ v[t, x]\ c[t, x]/\((γ\_1 + v[t, x])\) + If[
q\_large < q\_min, λ \((q\_large - q\_min)\), 0];\)\[IndentingNewLine]
\(\(cRHS\ = \ D[c[t, x]\ v[t, x]\ D[v[t, x], x], x] + If[v[
t, x] ≥ v\_g, ψ\ v[t, x]\ c[t,
x]\ /\((γ\_2 +
v[t, x])\), ω \((v[t, x] -
v\_d)\) c[t, x]];\)\(\[IndentingNewLine]\)
\)\[IndentingNewLine]
\(reqn\ = D[r[t, x], t]\ == \ rRHS;\)\[IndentingNewLine]
\(veqn\ = \ D[v[t, x], t]\ == \ vRHS;\)\[IndentingNewLine]
\(ceqn\ = \ D[c[t, x], t]\ == \ cRHS;\)\)

BC1 = Derivative[0, 1][r][t, 0] == 0;
BC2 = Derivative[0, 1][r][t, 1] == 0;
BC3 = Derivative[0, 1][v][t, 0] == 0;
BC4 = Derivative[0, 1][v][t, 1] == 0;
BC5 = c[t, 0] == 1;
BC6 = c[t, 1] v[t, 1] Derivative[0, 1][v][t, 1] == 0;

\!\(\(c\_init = \(c\_o\) Exp \((\(-150\) x\^2)\) == c[0,
x];\)\[IndentingNewLine]
\(r\_init = \((K\_r -
r\_base)\) Exp \((\(-100\) x\^2)\) + r\_base == r[0, x];\)\
\[IndentingNewLine]
\(v\_init = \((v\_g - v\_d)\)/\((2 v\_o)\) == v[0, x];\)\)

\!\(\(solution\ = \ NDSolve[{reqn, \ veqn, \ ceqn, q1\_i,
q2\_i, \ c\_init, \ v\_init, \
r\_init, \ BC1, \ BC2, \ BC3, \ BC4, \ BC5, \ BC6}, {r[t, x], v[t,
x], c[t, x], q1[t, x], q2[t, x]}, {t, 0, 1}, {x, 0, 1}];\)\)

I greatly appreciate any help.

Katie

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Subject (listing for 'Why am I getting this error when using NDSolve?')
Author Date Posted
Why am I getting this error when using NDSolve? Katie 09/12/05 9:16pm
Re: Why am I getting this error when using NDSo... yehuda ben-s... 09/13/05 02:04am
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