# Why the boundary condition is not taken in account?

**URL:** <https://fenicsproject.discourse.group/t/why-the-boundary-condition-is-not-taken-in-account/2596>\
**Category:** mesh\
**Created:** [March 9, 2020, 4:57pm UTC](https://fenicsproject.discourse.group/t/why-the-boundary-condition-is-not-taken-in-account/2596 "2020-03-09T16:57:08Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![Theo\_Poncelet](https://yyz2.discourse-cdn.com/free1/user_avatar/fenicsproject.discourse.group/theo_poncelet/32/879_2.png) [@Theo\_Poncelet](https://fenicsproject.discourse.group/u/Theo_Poncelet)\
**Post date:** [March 9, 2020, 4:57pm UTC](https://fenicsproject.discourse.group/t/why-the-boundary-condition-is-not-taken-in-account/2596/1 "2020-03-09T16:57:08Z")

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Hi everyone ! I’m a beginner and I tried to write a simple code but the result is no good : my solution is uniform equals to zero… Can anyone explain me why ?

Here is my code

```
base = Rectangle(Point(-1.0, -1.0), Point(1.0, 1.0))
hole = Circle(Point(0.25, 0), 0.25)
mesh5 = generate_mesh(base - hole, 15)

plt.figure(1)
plot(mesh5, title="Maillage du rectangle troué")

Hh5 = FunctionSpace(mesh5, 'P', 1)
tol = 1E-14
class inneredge(SubDomain):
    def inside(self, x, on_boundary):
        return on_boundary and (abs(x[0]-0.25)<0.5+tol) and (abs(x[1])<0.5+tol) 
    
ie = inneredge()
ie = DirichletBC(Hh5, Constant(1.0), ie)

class outeredge(SubDomain):
    def inside(self, x, on_boundary):
        return on_boundary and (abs(x[0] - 0.25) > 0.5+tol) and (abs(x[1])>0.5+tol)
    
oe = inneredge()
oe = DirichletBC(Hh5, Constant(0.0), oe)

c=Expression(("(x[0]-0.5)*(x[0]-0.5)+x[1]*x[1]","0.0"),degree = 2)

u = TrialFunction(Hh5)
v = TestFunction(Hh5)

F = inner(grad(u), grad(v))*dx+inner(c,grad(u))*v*dx

a = lhs(F)
L = rhs(F)
uh = Function(Hh5)
solve(a==L, uh, [ie,oe])

plu=plot(uh)
plt.title('Solution numérique u5')
plt.xlabel('x')
plt.ylabel('y')
plt.colorbar(plu)
```

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<div class="post-metadata">

**Author:** ![Theo\_Poncelet](https://yyz2.discourse-cdn.com/free1/user_avatar/fenicsproject.discourse.group/theo_poncelet/32/879_2.png) [@Theo\_Poncelet](https://fenicsproject.discourse.group/u/Theo_Poncelet)\
**Post date:** [March 9, 2020, 5:08pm UTC](https://fenicsproject.discourse.group/t/why-the-boundary-condition-is-not-taken-in-account/2596/2 "2020-03-09T17:08:19Z")

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i’m sorry guys I’m tired I have found the answer

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**Author:** ![dokken](https://yyz2.discourse-cdn.com/free1/user_avatar/fenicsproject.discourse.group/dokken/32/1560_2.png) [@dokken](https://fenicsproject.discourse.group/u/dokken)\
**Post date:** [March 9, 2020, 5:08pm UTC](https://fenicsproject.discourse.group/t/why-the-boundary-condition-is-not-taken-in-account/2596/3 "2020-03-09T17:08:56Z")

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For reference, you used inneredge twice. I’ll close this post. Feel free to delete it as you have all the same code in your other post

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**Author:** ![dokken](https://yyz2.discourse-cdn.com/free1/user_avatar/fenicsproject.discourse.group/dokken/32/1560_2.png) [@dokken](https://fenicsproject.discourse.group/u/dokken)\
**Post date:** [March 9, 2020, 5:13pm UTC](https://fenicsproject.discourse.group/t/why-the-boundary-condition-is-not-taken-in-account/2596/4 "2020-03-09T17:13:27Z")

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<div class="post-metadata">

**Author:** ![dokken](https://yyz2.discourse-cdn.com/free1/user_avatar/fenicsproject.discourse.group/dokken/32/1560_2.png) [@dokken](https://fenicsproject.discourse.group/u/dokken)\
**Post date:** [March 9, 2020, 5:13pm UTC](https://fenicsproject.discourse.group/t/why-the-boundary-condition-is-not-taken-in-account/2596/5 "2020-03-09T17:13:45Z")

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<div class="post-metadata">

**Author:** ![dokken](https://yyz2.discourse-cdn.com/free1/user_avatar/fenicsproject.discourse.group/dokken/32/1560_2.png) [@dokken](https://fenicsproject.discourse.group/u/dokken)\
**Post date:** [March 9, 2020, 5:13pm UTC](https://fenicsproject.discourse.group/t/why-the-boundary-condition-is-not-taken-in-account/2596/6 "2020-03-09T17:13:48Z")

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