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Student Support Forum: 'PDE Boundary value problem with NDSolve' topicStudent Support Forum > General > Archives > "PDE Boundary value problem with NDSolve"

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ronehwa
02/23/01 4:48pm

Hi Dear All,
Consider the Following question:
eq1=D[f[z,t],t]+v D[f[z,t],z]
eq2=D[g[z,t],t]-v D[g[z,t],z]
twowave=NDSolve[ { eq1 == 0,eq2 == 0,
f[z,0] == z+0.32*132/(1-0.32^2),
g[z,0] == -z+132/(1-0.32^2),
f[0,t] == 0.32*g[0,t],
0.32*f[100,t] ==g[100,t] },
{f,g},{z,0,100},{t,0,80}] ;

eq1==0 represents f[z,t] is a right-going propagation wave,
and eq2==0 represents g[z,t] is a left propagation wave.
v is the propagation velocity.
At the boundary z=100, the right-going wave refects 32% its amount and turn left to propagate,
At the boundary z=0, the left-going wave also refects 32% its amount and
turn right to propagate.

After executing twowave, the mathematica 4.0 return the following message:
''NDSolve::''bcart'': ''Warning: An insufficient number of boundary conditions
have been specified. Artificial boundary effects may be present in the
solution.''
I think the key to the question should be the boundary condition. How can I
set the the boundary condition properly?
Please help me solve this problem, I will deeply appreciate your help.


ronehwa.


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