Solvability of Neumann problemAnalytical solution of Partial Differential EquationSmooth solutions of the Laplace equation with Neumann dataDoes the following have a solution for f(x,y)?How to show that a delta function solution to a PDE (Fokker-Planck) is really a solutionReformulate this PDE in different notationPoisson equation with nonlinear Neumann conditionsMethod of characteristics for a parabolic PDEDiscrete Neumann problem: Representation by Simple Random WalkDirichlet plus Neumann problem without a PDEUniqueness of solution for Dirichlet and Neumann problem
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Solvability of Neumann problem
Analytical solution of Partial Differential EquationSmooth solutions of the Laplace equation with Neumann dataDoes the following have a solution for f(x,y)?How to show that a delta function solution to a PDE (Fokker-Planck) is really a solutionReformulate this PDE in different notationPoisson equation with nonlinear Neumann conditionsMethod of characteristics for a parabolic PDEDiscrete Neumann problem: Representation by Simple Random WalkDirichlet plus Neumann problem without a PDEUniqueness of solution for Dirichlet and Neumann problem
$begingroup$
Let $D$ be the domain in $mathbbR^2$ such that $x^2 + y^2 <4$ , and $alpha, beta$ and $ gamma $ be real constants. For which values of these three constants there is no solution for:$$Delta u =0 , (x,y)in D$$
$$partial_n u= alpha x^2 + beta y + gamma, (x,y) in partial D$$
How to solve the equation for the values of these three constants which the solution exists?
Thanks.
pde
$endgroup$
add a comment |
$begingroup$
Let $D$ be the domain in $mathbbR^2$ such that $x^2 + y^2 <4$ , and $alpha, beta$ and $ gamma $ be real constants. For which values of these three constants there is no solution for:$$Delta u =0 , (x,y)in D$$
$$partial_n u= alpha x^2 + beta y + gamma, (x,y) in partial D$$
How to solve the equation for the values of these three constants which the solution exists?
Thanks.
pde
$endgroup$
add a comment |
$begingroup$
Let $D$ be the domain in $mathbbR^2$ such that $x^2 + y^2 <4$ , and $alpha, beta$ and $ gamma $ be real constants. For which values of these three constants there is no solution for:$$Delta u =0 , (x,y)in D$$
$$partial_n u= alpha x^2 + beta y + gamma, (x,y) in partial D$$
How to solve the equation for the values of these three constants which the solution exists?
Thanks.
pde
$endgroup$
Let $D$ be the domain in $mathbbR^2$ such that $x^2 + y^2 <4$ , and $alpha, beta$ and $ gamma $ be real constants. For which values of these three constants there is no solution for:$$Delta u =0 , (x,y)in D$$
$$partial_n u= alpha x^2 + beta y + gamma, (x,y) in partial D$$
How to solve the equation for the values of these three constants which the solution exists?
Thanks.
pde
pde
asked 2 days ago
Math LoverMath Lover
938
938
add a comment |
add a comment |
2 Answers
2
active
oldest
votes
$begingroup$
In polar coordinates $(x,y) = (rcosphi,rsinphi)$ the general solution (which is finite at $r=0$) is
$$ u(r,phi) = A_0 + sum_n=1^infty r^n big[A_ncos(nphi) + B_nsin(nphi)big] $$
where $D = 0<r < 2$. The gradient is
$$ u_r(r,phi) = alpha r^2cos^2phi + beta rsin(phi) + gamma = fracalpha r^22big[cos(2phi) + 1big] + beta r sin(phi) + gamma $$
Evaluated at the boundary:
$$ u_r(2,phi) = 2alphacos(2phi) + 2beta sin(phi) + (2alpha + gamma) $$
You also have, from the general solution
$$ u_r(2,phi) = sum_n=1^infty n2^n-1big[A_ncos(nphi) + B_nsin(phi)big] $$
Comparing coefficients gives
begincases
2alpha + gamma = 0 \
B_1 = 2beta \
4A_2 = 2alpha
endcases
The first condition is required for the solution to exist.
$endgroup$
add a comment |
$begingroup$
The Neumann problem has a solution iff $int_Sfdsigma=0$ , where $S$, is the circle with center the origin and radius $2$ and $f(x,y)=alpha x^2 + beta y + gamma$ . A parametrization for this circle is $(2cost, 2sint)$. Now if we take the above mentioned line - integral we get the desired condition: $2a+gamma=0$.
Edit The proposition above is
$endgroup$
$begingroup$
What is $f$? ---
$endgroup$
– Dylan
2 days ago
$begingroup$
@Dylan, $f(x,y)=alpha x^2 + beta y + gamma$
$endgroup$
– dmtri
2 days ago
$begingroup$
It would help to specify that in your answer. Also mention which theorem this came from. This is a good answer but needs some more context.
$endgroup$
– Dylan
2 days ago
$begingroup$
Ok, thanks. See please "Introduction to PDE with Applications", by Zachamanoglou and Toe. It is just a ref in page 259 , line 14. Potential Theory is used here.
$endgroup$
– dmtri
2 days ago
add a comment |
Your Answer
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
$begingroup$
In polar coordinates $(x,y) = (rcosphi,rsinphi)$ the general solution (which is finite at $r=0$) is
$$ u(r,phi) = A_0 + sum_n=1^infty r^n big[A_ncos(nphi) + B_nsin(nphi)big] $$
where $D = 0<r < 2$. The gradient is
$$ u_r(r,phi) = alpha r^2cos^2phi + beta rsin(phi) + gamma = fracalpha r^22big[cos(2phi) + 1big] + beta r sin(phi) + gamma $$
Evaluated at the boundary:
$$ u_r(2,phi) = 2alphacos(2phi) + 2beta sin(phi) + (2alpha + gamma) $$
You also have, from the general solution
$$ u_r(2,phi) = sum_n=1^infty n2^n-1big[A_ncos(nphi) + B_nsin(phi)big] $$
Comparing coefficients gives
begincases
2alpha + gamma = 0 \
B_1 = 2beta \
4A_2 = 2alpha
endcases
The first condition is required for the solution to exist.
$endgroup$
add a comment |
$begingroup$
In polar coordinates $(x,y) = (rcosphi,rsinphi)$ the general solution (which is finite at $r=0$) is
$$ u(r,phi) = A_0 + sum_n=1^infty r^n big[A_ncos(nphi) + B_nsin(nphi)big] $$
where $D = 0<r < 2$. The gradient is
$$ u_r(r,phi) = alpha r^2cos^2phi + beta rsin(phi) + gamma = fracalpha r^22big[cos(2phi) + 1big] + beta r sin(phi) + gamma $$
Evaluated at the boundary:
$$ u_r(2,phi) = 2alphacos(2phi) + 2beta sin(phi) + (2alpha + gamma) $$
You also have, from the general solution
$$ u_r(2,phi) = sum_n=1^infty n2^n-1big[A_ncos(nphi) + B_nsin(phi)big] $$
Comparing coefficients gives
begincases
2alpha + gamma = 0 \
B_1 = 2beta \
4A_2 = 2alpha
endcases
The first condition is required for the solution to exist.
$endgroup$
add a comment |
$begingroup$
In polar coordinates $(x,y) = (rcosphi,rsinphi)$ the general solution (which is finite at $r=0$) is
$$ u(r,phi) = A_0 + sum_n=1^infty r^n big[A_ncos(nphi) + B_nsin(nphi)big] $$
where $D = 0<r < 2$. The gradient is
$$ u_r(r,phi) = alpha r^2cos^2phi + beta rsin(phi) + gamma = fracalpha r^22big[cos(2phi) + 1big] + beta r sin(phi) + gamma $$
Evaluated at the boundary:
$$ u_r(2,phi) = 2alphacos(2phi) + 2beta sin(phi) + (2alpha + gamma) $$
You also have, from the general solution
$$ u_r(2,phi) = sum_n=1^infty n2^n-1big[A_ncos(nphi) + B_nsin(phi)big] $$
Comparing coefficients gives
begincases
2alpha + gamma = 0 \
B_1 = 2beta \
4A_2 = 2alpha
endcases
The first condition is required for the solution to exist.
$endgroup$
In polar coordinates $(x,y) = (rcosphi,rsinphi)$ the general solution (which is finite at $r=0$) is
$$ u(r,phi) = A_0 + sum_n=1^infty r^n big[A_ncos(nphi) + B_nsin(nphi)big] $$
where $D = 0<r < 2$. The gradient is
$$ u_r(r,phi) = alpha r^2cos^2phi + beta rsin(phi) + gamma = fracalpha r^22big[cos(2phi) + 1big] + beta r sin(phi) + gamma $$
Evaluated at the boundary:
$$ u_r(2,phi) = 2alphacos(2phi) + 2beta sin(phi) + (2alpha + gamma) $$
You also have, from the general solution
$$ u_r(2,phi) = sum_n=1^infty n2^n-1big[A_ncos(nphi) + B_nsin(phi)big] $$
Comparing coefficients gives
begincases
2alpha + gamma = 0 \
B_1 = 2beta \
4A_2 = 2alpha
endcases
The first condition is required for the solution to exist.
answered 2 days ago
DylanDylan
13.8k31027
13.8k31027
add a comment |
add a comment |
$begingroup$
The Neumann problem has a solution iff $int_Sfdsigma=0$ , where $S$, is the circle with center the origin and radius $2$ and $f(x,y)=alpha x^2 + beta y + gamma$ . A parametrization for this circle is $(2cost, 2sint)$. Now if we take the above mentioned line - integral we get the desired condition: $2a+gamma=0$.
Edit The proposition above is
$endgroup$
$begingroup$
What is $f$? ---
$endgroup$
– Dylan
2 days ago
$begingroup$
@Dylan, $f(x,y)=alpha x^2 + beta y + gamma$
$endgroup$
– dmtri
2 days ago
$begingroup$
It would help to specify that in your answer. Also mention which theorem this came from. This is a good answer but needs some more context.
$endgroup$
– Dylan
2 days ago
$begingroup$
Ok, thanks. See please "Introduction to PDE with Applications", by Zachamanoglou and Toe. It is just a ref in page 259 , line 14. Potential Theory is used here.
$endgroup$
– dmtri
2 days ago
add a comment |
$begingroup$
The Neumann problem has a solution iff $int_Sfdsigma=0$ , where $S$, is the circle with center the origin and radius $2$ and $f(x,y)=alpha x^2 + beta y + gamma$ . A parametrization for this circle is $(2cost, 2sint)$. Now if we take the above mentioned line - integral we get the desired condition: $2a+gamma=0$.
Edit The proposition above is
$endgroup$
$begingroup$
What is $f$? ---
$endgroup$
– Dylan
2 days ago
$begingroup$
@Dylan, $f(x,y)=alpha x^2 + beta y + gamma$
$endgroup$
– dmtri
2 days ago
$begingroup$
It would help to specify that in your answer. Also mention which theorem this came from. This is a good answer but needs some more context.
$endgroup$
– Dylan
2 days ago
$begingroup$
Ok, thanks. See please "Introduction to PDE with Applications", by Zachamanoglou and Toe. It is just a ref in page 259 , line 14. Potential Theory is used here.
$endgroup$
– dmtri
2 days ago
add a comment |
$begingroup$
The Neumann problem has a solution iff $int_Sfdsigma=0$ , where $S$, is the circle with center the origin and radius $2$ and $f(x,y)=alpha x^2 + beta y + gamma$ . A parametrization for this circle is $(2cost, 2sint)$. Now if we take the above mentioned line - integral we get the desired condition: $2a+gamma=0$.
Edit The proposition above is
$endgroup$
The Neumann problem has a solution iff $int_Sfdsigma=0$ , where $S$, is the circle with center the origin and radius $2$ and $f(x,y)=alpha x^2 + beta y + gamma$ . A parametrization for this circle is $(2cost, 2sint)$. Now if we take the above mentioned line - integral we get the desired condition: $2a+gamma=0$.
Edit The proposition above is
edited 2 days ago
answered 2 days ago
dmtridmtri
1,6082521
1,6082521
$begingroup$
What is $f$? ---
$endgroup$
– Dylan
2 days ago
$begingroup$
@Dylan, $f(x,y)=alpha x^2 + beta y + gamma$
$endgroup$
– dmtri
2 days ago
$begingroup$
It would help to specify that in your answer. Also mention which theorem this came from. This is a good answer but needs some more context.
$endgroup$
– Dylan
2 days ago
$begingroup$
Ok, thanks. See please "Introduction to PDE with Applications", by Zachamanoglou and Toe. It is just a ref in page 259 , line 14. Potential Theory is used here.
$endgroup$
– dmtri
2 days ago
add a comment |
$begingroup$
What is $f$? ---
$endgroup$
– Dylan
2 days ago
$begingroup$
@Dylan, $f(x,y)=alpha x^2 + beta y + gamma$
$endgroup$
– dmtri
2 days ago
$begingroup$
It would help to specify that in your answer. Also mention which theorem this came from. This is a good answer but needs some more context.
$endgroup$
– Dylan
2 days ago
$begingroup$
Ok, thanks. See please "Introduction to PDE with Applications", by Zachamanoglou and Toe. It is just a ref in page 259 , line 14. Potential Theory is used here.
$endgroup$
– dmtri
2 days ago
$begingroup$
What is $f$? ---
$endgroup$
– Dylan
2 days ago
$begingroup$
What is $f$? ---
$endgroup$
– Dylan
2 days ago
$begingroup$
@Dylan, $f(x,y)=alpha x^2 + beta y + gamma$
$endgroup$
– dmtri
2 days ago
$begingroup$
@Dylan, $f(x,y)=alpha x^2 + beta y + gamma$
$endgroup$
– dmtri
2 days ago
$begingroup$
It would help to specify that in your answer. Also mention which theorem this came from. This is a good answer but needs some more context.
$endgroup$
– Dylan
2 days ago
$begingroup$
It would help to specify that in your answer. Also mention which theorem this came from. This is a good answer but needs some more context.
$endgroup$
– Dylan
2 days ago
$begingroup$
Ok, thanks. See please "Introduction to PDE with Applications", by Zachamanoglou and Toe. It is just a ref in page 259 , line 14. Potential Theory is used here.
$endgroup$
– dmtri
2 days ago
$begingroup$
Ok, thanks. See please "Introduction to PDE with Applications", by Zachamanoglou and Toe. It is just a ref in page 259 , line 14. Potential Theory is used here.
$endgroup$
– dmtri
2 days ago
add a comment |
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