Specific numerical eigenfunctions of Helmholtz equation in 3D for ellipsoidsNumerically solving Helmholtz equation in 3D for arbitrary shapesSolving the Helmholtz equation in polar coordinatesNumerically solving Helmholtz equation in 2D for arbitrary shapesNumerically solving Helmholtz equation in 3D for arbitrary shapesFinite Element Mass and Stiffness MatricesNDEigensystem producing imaginary eigenfrequencies for the vibrations of a cantileverNumerically Solving Helmholtz over the Rectangle - Why does this code only give eigenfunctions of the form $u_m1$failure of code with Helmholtz equation with point sourcesolving PDE equation like Helmholtz equation in 2DComparing analytical solution with numerical solution of Helmholtz equation in a unit squareNDSolve post-processing: Calculate the flow over a FEM-boundary
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Specific numerical eigenfunctions of Helmholtz equation in 3D for ellipsoids
Numerically solving Helmholtz equation in 3D for arbitrary shapesSolving the Helmholtz equation in polar coordinatesNumerically solving Helmholtz equation in 2D for arbitrary shapesNumerically solving Helmholtz equation in 3D for arbitrary shapesFinite Element Mass and Stiffness MatricesNDEigensystem producing imaginary eigenfrequencies for the vibrations of a cantileverNumerically Solving Helmholtz over the Rectangle - Why does this code only give eigenfunctions of the form $u_m1$failure of code with Helmholtz equation with point sourcesolving PDE equation like Helmholtz equation in 2DComparing analytical solution with numerical solution of Helmholtz equation in a unit squareNDSolve post-processing: Calculate the flow over a FEM-boundary
$begingroup$
I am trying to compute the eigenfunctions of an oblate spheroid (a=75 cm and b=60 cm) using Mathematica's FEM package and Chris' answer from here. Specifically, I am looking for eigenfrequencies around 433, 893, 913 and 2400 MGHz. Is there any way I could narrow my search besides getting all eigenfrequencies initially and then looking for the desired outcome which is impractical?
Here is my code for the first 4 eigenmodes:
Needs["NDSolve`FEM`"];
helmholzSolve3D[g_, numEigenToCompute_Integer,
opts : OptionsPattern[]] :=
Module[u, x, y, z, t, pde, dirichletCondition, mesh, boundaryMesh,
nr, state, femdata, initBCs, methodData, initCoeffs, vd, sd,
discretePDE, discreteBCs, load, stiffness, damping, pos, nDiri,
numEigen, res, eigenValues, eigenVectors,
evIF,
(*Discretize the region*)
If[Head[g] === ImplicitRegion || Head[g] === ParametricRegion,
mesh = ToElementMesh[DiscretizeRegion[g, opts], opts],
mesh = ToElementMesh[DiscretizeGraphics[g, opts], opts]];
boundaryMesh = ToBoundaryMesh[mesh];
(*Set up the PDE and boundary condition*)
pde = D[u[t, x, y, z], t] - Laplacian[u[t, x, y, z], x, y, z] +
u[t, x, y, z] == 0;
dirichletCondition = DirichletCondition[u[t, x, y, z] == 0, True];
(*Pre-process the equations to obtain the FiniteElementData in
StateData*)nr = ToNumericalRegion[mesh];
state =
NDSolve`ProcessEquations[pde, dirichletCondition,
u[0, x, y, z] == 0, u, t, 0, 1, Element[x, y, z, nr]];
femdata = state["FiniteElementData"];
initBCs = femdata["BoundaryConditionData"];
methodData = femdata["FEMMethodData"];
initCoeffs = femdata["PDECoefficientData"];
(*Set up the solution*)vd = methodData["VariableData"];
sd = NDSolve`SolutionData["Space" -> nr, "Time" -> 0.];
(*Discretize the PDE and boundary conditions*)
discretePDE = DiscretizePDE[initCoeffs, methodData, sd];
discreteBCs = DiscretizeBoundaryConditions[initBCs, methodData, sd];
(*Extract the relevant matrices and deploy the boundary conditions*)
load = discretePDE["LoadVector"];
stiffness = discretePDE["StiffnessMatrix"];
damping = discretePDE["DampingMatrix"];
DeployBoundaryConditions[load, stiffness, damping, discreteBCs];
(*Set the number of eigenvalues ignoring the Dirichlet positions*)
pos = discreteBCs["DirichletMatrix"]["NonzeroPositions"][[All, 2]];
nDiri = Length[pos];
numEigen = numEigenToCompute + nDiri;
(*Solve the eigensystem*)
res = Eigensystem[stiffness, damping, -numEigen];
res = Reverse /@ res;
eigenValues = res[[1, nDiri + 1 ;; Abs[numEigen]]];
eigenVectors = res[[2, nDiri + 1 ;; Abs[numEigen]]];
evIF = ElementMeshInterpolation[mesh, #] & /@ eigenVectors;
(*Return the relevant information*)
eigenValues, evIF, mesh]
ev, if, mesh =
helmholzSolve3D[Ellipsoid[0, 0, 0, 0.75, 0.6, 0.6], 4,
MaxCellMeasure -> 0.025]
Table[
DensityPlot[
if[[i]][x, y, 0.1], x, -1, 1, y, -1, 1,
RegionFunction -> Function[x, y, x^2/0.75^2 + y^2/0.6^2 < 1],
PlotLabel -> ev[i] ,
ColorFunction -> Hue,
PlotLegends -> Automatic
],
i, 1, 4
]
Any suggestions?
differential-equations numerics finite-element-method
$endgroup$
add a comment |
$begingroup$
I am trying to compute the eigenfunctions of an oblate spheroid (a=75 cm and b=60 cm) using Mathematica's FEM package and Chris' answer from here. Specifically, I am looking for eigenfrequencies around 433, 893, 913 and 2400 MGHz. Is there any way I could narrow my search besides getting all eigenfrequencies initially and then looking for the desired outcome which is impractical?
Here is my code for the first 4 eigenmodes:
Needs["NDSolve`FEM`"];
helmholzSolve3D[g_, numEigenToCompute_Integer,
opts : OptionsPattern[]] :=
Module[u, x, y, z, t, pde, dirichletCondition, mesh, boundaryMesh,
nr, state, femdata, initBCs, methodData, initCoeffs, vd, sd,
discretePDE, discreteBCs, load, stiffness, damping, pos, nDiri,
numEigen, res, eigenValues, eigenVectors,
evIF,
(*Discretize the region*)
If[Head[g] === ImplicitRegion || Head[g] === ParametricRegion,
mesh = ToElementMesh[DiscretizeRegion[g, opts], opts],
mesh = ToElementMesh[DiscretizeGraphics[g, opts], opts]];
boundaryMesh = ToBoundaryMesh[mesh];
(*Set up the PDE and boundary condition*)
pde = D[u[t, x, y, z], t] - Laplacian[u[t, x, y, z], x, y, z] +
u[t, x, y, z] == 0;
dirichletCondition = DirichletCondition[u[t, x, y, z] == 0, True];
(*Pre-process the equations to obtain the FiniteElementData in
StateData*)nr = ToNumericalRegion[mesh];
state =
NDSolve`ProcessEquations[pde, dirichletCondition,
u[0, x, y, z] == 0, u, t, 0, 1, Element[x, y, z, nr]];
femdata = state["FiniteElementData"];
initBCs = femdata["BoundaryConditionData"];
methodData = femdata["FEMMethodData"];
initCoeffs = femdata["PDECoefficientData"];
(*Set up the solution*)vd = methodData["VariableData"];
sd = NDSolve`SolutionData["Space" -> nr, "Time" -> 0.];
(*Discretize the PDE and boundary conditions*)
discretePDE = DiscretizePDE[initCoeffs, methodData, sd];
discreteBCs = DiscretizeBoundaryConditions[initBCs, methodData, sd];
(*Extract the relevant matrices and deploy the boundary conditions*)
load = discretePDE["LoadVector"];
stiffness = discretePDE["StiffnessMatrix"];
damping = discretePDE["DampingMatrix"];
DeployBoundaryConditions[load, stiffness, damping, discreteBCs];
(*Set the number of eigenvalues ignoring the Dirichlet positions*)
pos = discreteBCs["DirichletMatrix"]["NonzeroPositions"][[All, 2]];
nDiri = Length[pos];
numEigen = numEigenToCompute + nDiri;
(*Solve the eigensystem*)
res = Eigensystem[stiffness, damping, -numEigen];
res = Reverse /@ res;
eigenValues = res[[1, nDiri + 1 ;; Abs[numEigen]]];
eigenVectors = res[[2, nDiri + 1 ;; Abs[numEigen]]];
evIF = ElementMeshInterpolation[mesh, #] & /@ eigenVectors;
(*Return the relevant information*)
eigenValues, evIF, mesh]
ev, if, mesh =
helmholzSolve3D[Ellipsoid[0, 0, 0, 0.75, 0.6, 0.6], 4,
MaxCellMeasure -> 0.025]
Table[
DensityPlot[
if[[i]][x, y, 0.1], x, -1, 1, y, -1, 1,
RegionFunction -> Function[x, y, x^2/0.75^2 + y^2/0.6^2 < 1],
PlotLabel -> ev[i] ,
ColorFunction -> Hue,
PlotLegends -> Automatic
],
i, 1, 4
]
Any suggestions?
differential-equations numerics finite-element-method
$endgroup$
add a comment |
$begingroup$
I am trying to compute the eigenfunctions of an oblate spheroid (a=75 cm and b=60 cm) using Mathematica's FEM package and Chris' answer from here. Specifically, I am looking for eigenfrequencies around 433, 893, 913 and 2400 MGHz. Is there any way I could narrow my search besides getting all eigenfrequencies initially and then looking for the desired outcome which is impractical?
Here is my code for the first 4 eigenmodes:
Needs["NDSolve`FEM`"];
helmholzSolve3D[g_, numEigenToCompute_Integer,
opts : OptionsPattern[]] :=
Module[u, x, y, z, t, pde, dirichletCondition, mesh, boundaryMesh,
nr, state, femdata, initBCs, methodData, initCoeffs, vd, sd,
discretePDE, discreteBCs, load, stiffness, damping, pos, nDiri,
numEigen, res, eigenValues, eigenVectors,
evIF,
(*Discretize the region*)
If[Head[g] === ImplicitRegion || Head[g] === ParametricRegion,
mesh = ToElementMesh[DiscretizeRegion[g, opts], opts],
mesh = ToElementMesh[DiscretizeGraphics[g, opts], opts]];
boundaryMesh = ToBoundaryMesh[mesh];
(*Set up the PDE and boundary condition*)
pde = D[u[t, x, y, z], t] - Laplacian[u[t, x, y, z], x, y, z] +
u[t, x, y, z] == 0;
dirichletCondition = DirichletCondition[u[t, x, y, z] == 0, True];
(*Pre-process the equations to obtain the FiniteElementData in
StateData*)nr = ToNumericalRegion[mesh];
state =
NDSolve`ProcessEquations[pde, dirichletCondition,
u[0, x, y, z] == 0, u, t, 0, 1, Element[x, y, z, nr]];
femdata = state["FiniteElementData"];
initBCs = femdata["BoundaryConditionData"];
methodData = femdata["FEMMethodData"];
initCoeffs = femdata["PDECoefficientData"];
(*Set up the solution*)vd = methodData["VariableData"];
sd = NDSolve`SolutionData["Space" -> nr, "Time" -> 0.];
(*Discretize the PDE and boundary conditions*)
discretePDE = DiscretizePDE[initCoeffs, methodData, sd];
discreteBCs = DiscretizeBoundaryConditions[initBCs, methodData, sd];
(*Extract the relevant matrices and deploy the boundary conditions*)
load = discretePDE["LoadVector"];
stiffness = discretePDE["StiffnessMatrix"];
damping = discretePDE["DampingMatrix"];
DeployBoundaryConditions[load, stiffness, damping, discreteBCs];
(*Set the number of eigenvalues ignoring the Dirichlet positions*)
pos = discreteBCs["DirichletMatrix"]["NonzeroPositions"][[All, 2]];
nDiri = Length[pos];
numEigen = numEigenToCompute + nDiri;
(*Solve the eigensystem*)
res = Eigensystem[stiffness, damping, -numEigen];
res = Reverse /@ res;
eigenValues = res[[1, nDiri + 1 ;; Abs[numEigen]]];
eigenVectors = res[[2, nDiri + 1 ;; Abs[numEigen]]];
evIF = ElementMeshInterpolation[mesh, #] & /@ eigenVectors;
(*Return the relevant information*)
eigenValues, evIF, mesh]
ev, if, mesh =
helmholzSolve3D[Ellipsoid[0, 0, 0, 0.75, 0.6, 0.6], 4,
MaxCellMeasure -> 0.025]
Table[
DensityPlot[
if[[i]][x, y, 0.1], x, -1, 1, y, -1, 1,
RegionFunction -> Function[x, y, x^2/0.75^2 + y^2/0.6^2 < 1],
PlotLabel -> ev[i] ,
ColorFunction -> Hue,
PlotLegends -> Automatic
],
i, 1, 4
]
Any suggestions?
differential-equations numerics finite-element-method
$endgroup$
I am trying to compute the eigenfunctions of an oblate spheroid (a=75 cm and b=60 cm) using Mathematica's FEM package and Chris' answer from here. Specifically, I am looking for eigenfrequencies around 433, 893, 913 and 2400 MGHz. Is there any way I could narrow my search besides getting all eigenfrequencies initially and then looking for the desired outcome which is impractical?
Here is my code for the first 4 eigenmodes:
Needs["NDSolve`FEM`"];
helmholzSolve3D[g_, numEigenToCompute_Integer,
opts : OptionsPattern[]] :=
Module[u, x, y, z, t, pde, dirichletCondition, mesh, boundaryMesh,
nr, state, femdata, initBCs, methodData, initCoeffs, vd, sd,
discretePDE, discreteBCs, load, stiffness, damping, pos, nDiri,
numEigen, res, eigenValues, eigenVectors,
evIF,
(*Discretize the region*)
If[Head[g] === ImplicitRegion || Head[g] === ParametricRegion,
mesh = ToElementMesh[DiscretizeRegion[g, opts], opts],
mesh = ToElementMesh[DiscretizeGraphics[g, opts], opts]];
boundaryMesh = ToBoundaryMesh[mesh];
(*Set up the PDE and boundary condition*)
pde = D[u[t, x, y, z], t] - Laplacian[u[t, x, y, z], x, y, z] +
u[t, x, y, z] == 0;
dirichletCondition = DirichletCondition[u[t, x, y, z] == 0, True];
(*Pre-process the equations to obtain the FiniteElementData in
StateData*)nr = ToNumericalRegion[mesh];
state =
NDSolve`ProcessEquations[pde, dirichletCondition,
u[0, x, y, z] == 0, u, t, 0, 1, Element[x, y, z, nr]];
femdata = state["FiniteElementData"];
initBCs = femdata["BoundaryConditionData"];
methodData = femdata["FEMMethodData"];
initCoeffs = femdata["PDECoefficientData"];
(*Set up the solution*)vd = methodData["VariableData"];
sd = NDSolve`SolutionData["Space" -> nr, "Time" -> 0.];
(*Discretize the PDE and boundary conditions*)
discretePDE = DiscretizePDE[initCoeffs, methodData, sd];
discreteBCs = DiscretizeBoundaryConditions[initBCs, methodData, sd];
(*Extract the relevant matrices and deploy the boundary conditions*)
load = discretePDE["LoadVector"];
stiffness = discretePDE["StiffnessMatrix"];
damping = discretePDE["DampingMatrix"];
DeployBoundaryConditions[load, stiffness, damping, discreteBCs];
(*Set the number of eigenvalues ignoring the Dirichlet positions*)
pos = discreteBCs["DirichletMatrix"]["NonzeroPositions"][[All, 2]];
nDiri = Length[pos];
numEigen = numEigenToCompute + nDiri;
(*Solve the eigensystem*)
res = Eigensystem[stiffness, damping, -numEigen];
res = Reverse /@ res;
eigenValues = res[[1, nDiri + 1 ;; Abs[numEigen]]];
eigenVectors = res[[2, nDiri + 1 ;; Abs[numEigen]]];
evIF = ElementMeshInterpolation[mesh, #] & /@ eigenVectors;
(*Return the relevant information*)
eigenValues, evIF, mesh]
ev, if, mesh =
helmholzSolve3D[Ellipsoid[0, 0, 0, 0.75, 0.6, 0.6], 4,
MaxCellMeasure -> 0.025]
Table[
DensityPlot[
if[[i]][x, y, 0.1], x, -1, 1, y, -1, 1,
RegionFunction -> Function[x, y, x^2/0.75^2 + y^2/0.6^2 < 1],
PlotLabel -> ev[i] ,
ColorFunction -> Hue,
PlotLegends -> Automatic
],
i, 1, 4
]
Any suggestions?
differential-equations numerics finite-element-method
differential-equations numerics finite-element-method
edited Mar 29 at 11:18
user64494
3,65311122
3,65311122
asked Mar 26 at 22:24
George GiannoulisGeorge Giannoulis
624
624
add a comment |
add a comment |
2 Answers
2
active
oldest
votes
$begingroup$
You could use something like this:
vals, funs =
NDEigensystem[-Laplacian[u[x, y, z], x, y, z] + u[x, y, z],
DirichletCondition[u[x, y, z] == 0, True], u,
Element[x, y, z, Ellipsoid[0, 0, 0, 0.75, 0.6, 0.6]], 4,
Method -> "Eigensystem" -> "FEAST", "Interval" -> 425, 500]
427.961, 428.783, 430.026, 430.156,...
And here are the density plots:
Table[DensityPlot[funs[[i]][x, y, 0.1], x, -1, 1, y, -1, 1,
RegionFunction -> Function[x, y, x^2/0.75^2 + y^2/0.6^2 < 1],
PlotLabel -> vals[[i]], ColorFunction -> Hue,
PlotLegends -> Automatic, PlotRange -> All], i, 1, 4]
Slice density plots:
Table[SliceDensityPlot3D[funs[[i]][x, y, z],
Element[ x, y, z, Ellipsoid[0, 0, 0, 0.75, 0.6, 0.6]],
PlotRange -> All, PlotLabel -> vals[[i]],
PlotTheme -> "Minimal"], i, Length[vals]]
And density plots:
Table[DensityPlot3D[funs[[i]][x, y, z],
Element[ x, y, z, Ellipsoid[0, 0, 0, 0.75, 0.6, 0.6]],
PlotRange -> All, PlotLabel -> vals[[i]],
PlotTheme -> "Minimal"], i, Length[vals]]
$endgroup$
$begingroup$
Thank you for your answer but I need to clarify something technical here. Does NDEigensystems compute eigenmodes from start, ie 0 and then narrows its search to the desired interval (425, 500 HZ here) or does it start from 425 Hz and then stops at 500 Hz?
$endgroup$
– George Giannoulis
Mar 28 at 19:26
$begingroup$
@GeorgeGiannoulis, I think the latter, but you could have a look at the FEAST algorithm.Thought that version is not the same as the one linked in Mathematica but that shlould not matter.NDEigensystem
makes use ifEigensystem
(like in your code) which then uses FEAST from a library.
$endgroup$
– user21
Mar 29 at 5:36
$begingroup$
OK one last thing here. I can't seem to understand what the boubdary is in your code. Is it a cube,a sphere, an ellispoid? Something else?
$endgroup$
– George Giannoulis
Mar 29 at 10:16
$begingroup$
@GeorgeGiannoulis, it's the ellipsoidI have updated the code.
$endgroup$
– user21
Mar 29 at 10:23
$begingroup$
Great! I d like to add some density plots though for the eigenvalues. My code looks something like this:
$endgroup$
– George Giannoulis
Mar 29 at 10:58
|
show 6 more comments
$begingroup$
You may try Eigensystem
with
Method -> "FEAST", "Interval" -> a, b
to search eigenvalue pairs within an interval. See the documentation of Eigensystem
, Section "Methods", Subsection "FEAST" for more details.
$endgroup$
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
$begingroup$
You could use something like this:
vals, funs =
NDEigensystem[-Laplacian[u[x, y, z], x, y, z] + u[x, y, z],
DirichletCondition[u[x, y, z] == 0, True], u,
Element[x, y, z, Ellipsoid[0, 0, 0, 0.75, 0.6, 0.6]], 4,
Method -> "Eigensystem" -> "FEAST", "Interval" -> 425, 500]
427.961, 428.783, 430.026, 430.156,...
And here are the density plots:
Table[DensityPlot[funs[[i]][x, y, 0.1], x, -1, 1, y, -1, 1,
RegionFunction -> Function[x, y, x^2/0.75^2 + y^2/0.6^2 < 1],
PlotLabel -> vals[[i]], ColorFunction -> Hue,
PlotLegends -> Automatic, PlotRange -> All], i, 1, 4]
Slice density plots:
Table[SliceDensityPlot3D[funs[[i]][x, y, z],
Element[ x, y, z, Ellipsoid[0, 0, 0, 0.75, 0.6, 0.6]],
PlotRange -> All, PlotLabel -> vals[[i]],
PlotTheme -> "Minimal"], i, Length[vals]]
And density plots:
Table[DensityPlot3D[funs[[i]][x, y, z],
Element[ x, y, z, Ellipsoid[0, 0, 0, 0.75, 0.6, 0.6]],
PlotRange -> All, PlotLabel -> vals[[i]],
PlotTheme -> "Minimal"], i, Length[vals]]
$endgroup$
$begingroup$
Thank you for your answer but I need to clarify something technical here. Does NDEigensystems compute eigenmodes from start, ie 0 and then narrows its search to the desired interval (425, 500 HZ here) or does it start from 425 Hz and then stops at 500 Hz?
$endgroup$
– George Giannoulis
Mar 28 at 19:26
$begingroup$
@GeorgeGiannoulis, I think the latter, but you could have a look at the FEAST algorithm.Thought that version is not the same as the one linked in Mathematica but that shlould not matter.NDEigensystem
makes use ifEigensystem
(like in your code) which then uses FEAST from a library.
$endgroup$
– user21
Mar 29 at 5:36
$begingroup$
OK one last thing here. I can't seem to understand what the boubdary is in your code. Is it a cube,a sphere, an ellispoid? Something else?
$endgroup$
– George Giannoulis
Mar 29 at 10:16
$begingroup$
@GeorgeGiannoulis, it's the ellipsoidI have updated the code.
$endgroup$
– user21
Mar 29 at 10:23
$begingroup$
Great! I d like to add some density plots though for the eigenvalues. My code looks something like this:
$endgroup$
– George Giannoulis
Mar 29 at 10:58
|
show 6 more comments
$begingroup$
You could use something like this:
vals, funs =
NDEigensystem[-Laplacian[u[x, y, z], x, y, z] + u[x, y, z],
DirichletCondition[u[x, y, z] == 0, True], u,
Element[x, y, z, Ellipsoid[0, 0, 0, 0.75, 0.6, 0.6]], 4,
Method -> "Eigensystem" -> "FEAST", "Interval" -> 425, 500]
427.961, 428.783, 430.026, 430.156,...
And here are the density plots:
Table[DensityPlot[funs[[i]][x, y, 0.1], x, -1, 1, y, -1, 1,
RegionFunction -> Function[x, y, x^2/0.75^2 + y^2/0.6^2 < 1],
PlotLabel -> vals[[i]], ColorFunction -> Hue,
PlotLegends -> Automatic, PlotRange -> All], i, 1, 4]
Slice density plots:
Table[SliceDensityPlot3D[funs[[i]][x, y, z],
Element[ x, y, z, Ellipsoid[0, 0, 0, 0.75, 0.6, 0.6]],
PlotRange -> All, PlotLabel -> vals[[i]],
PlotTheme -> "Minimal"], i, Length[vals]]
And density plots:
Table[DensityPlot3D[funs[[i]][x, y, z],
Element[ x, y, z, Ellipsoid[0, 0, 0, 0.75, 0.6, 0.6]],
PlotRange -> All, PlotLabel -> vals[[i]],
PlotTheme -> "Minimal"], i, Length[vals]]
$endgroup$
$begingroup$
Thank you for your answer but I need to clarify something technical here. Does NDEigensystems compute eigenmodes from start, ie 0 and then narrows its search to the desired interval (425, 500 HZ here) or does it start from 425 Hz and then stops at 500 Hz?
$endgroup$
– George Giannoulis
Mar 28 at 19:26
$begingroup$
@GeorgeGiannoulis, I think the latter, but you could have a look at the FEAST algorithm.Thought that version is not the same as the one linked in Mathematica but that shlould not matter.NDEigensystem
makes use ifEigensystem
(like in your code) which then uses FEAST from a library.
$endgroup$
– user21
Mar 29 at 5:36
$begingroup$
OK one last thing here. I can't seem to understand what the boubdary is in your code. Is it a cube,a sphere, an ellispoid? Something else?
$endgroup$
– George Giannoulis
Mar 29 at 10:16
$begingroup$
@GeorgeGiannoulis, it's the ellipsoidI have updated the code.
$endgroup$
– user21
Mar 29 at 10:23
$begingroup$
Great! I d like to add some density plots though for the eigenvalues. My code looks something like this:
$endgroup$
– George Giannoulis
Mar 29 at 10:58
|
show 6 more comments
$begingroup$
You could use something like this:
vals, funs =
NDEigensystem[-Laplacian[u[x, y, z], x, y, z] + u[x, y, z],
DirichletCondition[u[x, y, z] == 0, True], u,
Element[x, y, z, Ellipsoid[0, 0, 0, 0.75, 0.6, 0.6]], 4,
Method -> "Eigensystem" -> "FEAST", "Interval" -> 425, 500]
427.961, 428.783, 430.026, 430.156,...
And here are the density plots:
Table[DensityPlot[funs[[i]][x, y, 0.1], x, -1, 1, y, -1, 1,
RegionFunction -> Function[x, y, x^2/0.75^2 + y^2/0.6^2 < 1],
PlotLabel -> vals[[i]], ColorFunction -> Hue,
PlotLegends -> Automatic, PlotRange -> All], i, 1, 4]
Slice density plots:
Table[SliceDensityPlot3D[funs[[i]][x, y, z],
Element[ x, y, z, Ellipsoid[0, 0, 0, 0.75, 0.6, 0.6]],
PlotRange -> All, PlotLabel -> vals[[i]],
PlotTheme -> "Minimal"], i, Length[vals]]
And density plots:
Table[DensityPlot3D[funs[[i]][x, y, z],
Element[ x, y, z, Ellipsoid[0, 0, 0, 0.75, 0.6, 0.6]],
PlotRange -> All, PlotLabel -> vals[[i]],
PlotTheme -> "Minimal"], i, Length[vals]]
$endgroup$
You could use something like this:
vals, funs =
NDEigensystem[-Laplacian[u[x, y, z], x, y, z] + u[x, y, z],
DirichletCondition[u[x, y, z] == 0, True], u,
Element[x, y, z, Ellipsoid[0, 0, 0, 0.75, 0.6, 0.6]], 4,
Method -> "Eigensystem" -> "FEAST", "Interval" -> 425, 500]
427.961, 428.783, 430.026, 430.156,...
And here are the density plots:
Table[DensityPlot[funs[[i]][x, y, 0.1], x, -1, 1, y, -1, 1,
RegionFunction -> Function[x, y, x^2/0.75^2 + y^2/0.6^2 < 1],
PlotLabel -> vals[[i]], ColorFunction -> Hue,
PlotLegends -> Automatic, PlotRange -> All], i, 1, 4]
Slice density plots:
Table[SliceDensityPlot3D[funs[[i]][x, y, z],
Element[ x, y, z, Ellipsoid[0, 0, 0, 0.75, 0.6, 0.6]],
PlotRange -> All, PlotLabel -> vals[[i]],
PlotTheme -> "Minimal"], i, Length[vals]]
And density plots:
Table[DensityPlot3D[funs[[i]][x, y, z],
Element[ x, y, z, Ellipsoid[0, 0, 0, 0.75, 0.6, 0.6]],
PlotRange -> All, PlotLabel -> vals[[i]],
PlotTheme -> "Minimal"], i, Length[vals]]
edited Mar 29 at 12:55
answered Mar 27 at 6:31
user21user21
21.3k560100
21.3k560100
$begingroup$
Thank you for your answer but I need to clarify something technical here. Does NDEigensystems compute eigenmodes from start, ie 0 and then narrows its search to the desired interval (425, 500 HZ here) or does it start from 425 Hz and then stops at 500 Hz?
$endgroup$
– George Giannoulis
Mar 28 at 19:26
$begingroup$
@GeorgeGiannoulis, I think the latter, but you could have a look at the FEAST algorithm.Thought that version is not the same as the one linked in Mathematica but that shlould not matter.NDEigensystem
makes use ifEigensystem
(like in your code) which then uses FEAST from a library.
$endgroup$
– user21
Mar 29 at 5:36
$begingroup$
OK one last thing here. I can't seem to understand what the boubdary is in your code. Is it a cube,a sphere, an ellispoid? Something else?
$endgroup$
– George Giannoulis
Mar 29 at 10:16
$begingroup$
@GeorgeGiannoulis, it's the ellipsoidI have updated the code.
$endgroup$
– user21
Mar 29 at 10:23
$begingroup$
Great! I d like to add some density plots though for the eigenvalues. My code looks something like this:
$endgroup$
– George Giannoulis
Mar 29 at 10:58
|
show 6 more comments
$begingroup$
Thank you for your answer but I need to clarify something technical here. Does NDEigensystems compute eigenmodes from start, ie 0 and then narrows its search to the desired interval (425, 500 HZ here) or does it start from 425 Hz and then stops at 500 Hz?
$endgroup$
– George Giannoulis
Mar 28 at 19:26
$begingroup$
@GeorgeGiannoulis, I think the latter, but you could have a look at the FEAST algorithm.Thought that version is not the same as the one linked in Mathematica but that shlould not matter.NDEigensystem
makes use ifEigensystem
(like in your code) which then uses FEAST from a library.
$endgroup$
– user21
Mar 29 at 5:36
$begingroup$
OK one last thing here. I can't seem to understand what the boubdary is in your code. Is it a cube,a sphere, an ellispoid? Something else?
$endgroup$
– George Giannoulis
Mar 29 at 10:16
$begingroup$
@GeorgeGiannoulis, it's the ellipsoidI have updated the code.
$endgroup$
– user21
Mar 29 at 10:23
$begingroup$
Great! I d like to add some density plots though for the eigenvalues. My code looks something like this:
$endgroup$
– George Giannoulis
Mar 29 at 10:58
$begingroup$
Thank you for your answer but I need to clarify something technical here. Does NDEigensystems compute eigenmodes from start, ie 0 and then narrows its search to the desired interval (425, 500 HZ here) or does it start from 425 Hz and then stops at 500 Hz?
$endgroup$
– George Giannoulis
Mar 28 at 19:26
$begingroup$
Thank you for your answer but I need to clarify something technical here. Does NDEigensystems compute eigenmodes from start, ie 0 and then narrows its search to the desired interval (425, 500 HZ here) or does it start from 425 Hz and then stops at 500 Hz?
$endgroup$
– George Giannoulis
Mar 28 at 19:26
$begingroup$
@GeorgeGiannoulis, I think the latter, but you could have a look at the FEAST algorithm.Thought that version is not the same as the one linked in Mathematica but that shlould not matter.
NDEigensystem
makes use if Eigensystem
(like in your code) which then uses FEAST from a library.$endgroup$
– user21
Mar 29 at 5:36
$begingroup$
@GeorgeGiannoulis, I think the latter, but you could have a look at the FEAST algorithm.Thought that version is not the same as the one linked in Mathematica but that shlould not matter.
NDEigensystem
makes use if Eigensystem
(like in your code) which then uses FEAST from a library.$endgroup$
– user21
Mar 29 at 5:36
$begingroup$
OK one last thing here. I can't seem to understand what the boubdary is in your code. Is it a cube,a sphere, an ellispoid? Something else?
$endgroup$
– George Giannoulis
Mar 29 at 10:16
$begingroup$
OK one last thing here. I can't seem to understand what the boubdary is in your code. Is it a cube,a sphere, an ellispoid? Something else?
$endgroup$
– George Giannoulis
Mar 29 at 10:16
$begingroup$
@GeorgeGiannoulis, it's the ellipsoidI have updated the code.
$endgroup$
– user21
Mar 29 at 10:23
$begingroup$
@GeorgeGiannoulis, it's the ellipsoidI have updated the code.
$endgroup$
– user21
Mar 29 at 10:23
$begingroup$
Great! I d like to add some density plots though for the eigenvalues. My code looks something like this:
$endgroup$
– George Giannoulis
Mar 29 at 10:58
$begingroup$
Great! I d like to add some density plots though for the eigenvalues. My code looks something like this:
$endgroup$
– George Giannoulis
Mar 29 at 10:58
|
show 6 more comments
$begingroup$
You may try Eigensystem
with
Method -> "FEAST", "Interval" -> a, b
to search eigenvalue pairs within an interval. See the documentation of Eigensystem
, Section "Methods", Subsection "FEAST" for more details.
$endgroup$
add a comment |
$begingroup$
You may try Eigensystem
with
Method -> "FEAST", "Interval" -> a, b
to search eigenvalue pairs within an interval. See the documentation of Eigensystem
, Section "Methods", Subsection "FEAST" for more details.
$endgroup$
add a comment |
$begingroup$
You may try Eigensystem
with
Method -> "FEAST", "Interval" -> a, b
to search eigenvalue pairs within an interval. See the documentation of Eigensystem
, Section "Methods", Subsection "FEAST" for more details.
$endgroup$
You may try Eigensystem
with
Method -> "FEAST", "Interval" -> a, b
to search eigenvalue pairs within an interval. See the documentation of Eigensystem
, Section "Methods", Subsection "FEAST" for more details.
edited Mar 27 at 7:23
answered Mar 26 at 22:32
Henrik SchumacherHenrik Schumacher
61.3k585171
61.3k585171
add a comment |
add a comment |
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