Not sure how to set up the Laplacian/Poisson Equation












2












$begingroup$


As stated, I am having trouble trying to set up a Laplacian/Poisson Equation. I have boundary conditions with this too, and I've tried using the DirichletCondition function, but I don't know what I'm doing there either. (I have almost zero Mathematica experience, and the Wolfram site's help is just as confusing to me as the program.)



Laplacian[V[x, y], {x, y} == 0;

V[x, 0] == 0;
V[x, 0.05] == 1;
V[0, y] == 0;
V[0.1, y] == 0;]

Plot[{x, -0.25, 0.25}, {y, -0.15, 0.15}]


Plot I'm getting



While I am getting that plot to appear, it's not even close to what I need. What I'm needing is the solution to appear within the region 0 ≤ x ≤ 0.1 and 0 ≤ y ≤ 0.05, as stated by the boundary conditions (rectangular). It's supposed to be a distribution type of plot, kind of like elevation contour graphs and similar.



And for now, the PDE I'm solving is equal to 0, so once I get that done, how do I set up the PDE when it's not equal to 0 (Poisson's Equation)? I would think that since Laplacian is a function, I can't use it anymore since the PDE isn't equal to 0 anymore.



Help is greatly appreciated!










share|improve this question







New contributor




LtGenSpartan is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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    2












    $begingroup$


    As stated, I am having trouble trying to set up a Laplacian/Poisson Equation. I have boundary conditions with this too, and I've tried using the DirichletCondition function, but I don't know what I'm doing there either. (I have almost zero Mathematica experience, and the Wolfram site's help is just as confusing to me as the program.)



    Laplacian[V[x, y], {x, y} == 0;

    V[x, 0] == 0;
    V[x, 0.05] == 1;
    V[0, y] == 0;
    V[0.1, y] == 0;]

    Plot[{x, -0.25, 0.25}, {y, -0.15, 0.15}]


    Plot I'm getting



    While I am getting that plot to appear, it's not even close to what I need. What I'm needing is the solution to appear within the region 0 ≤ x ≤ 0.1 and 0 ≤ y ≤ 0.05, as stated by the boundary conditions (rectangular). It's supposed to be a distribution type of plot, kind of like elevation contour graphs and similar.



    And for now, the PDE I'm solving is equal to 0, so once I get that done, how do I set up the PDE when it's not equal to 0 (Poisson's Equation)? I would think that since Laplacian is a function, I can't use it anymore since the PDE isn't equal to 0 anymore.



    Help is greatly appreciated!










    share|improve this question







    New contributor




    LtGenSpartan is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
    Check out our Code of Conduct.







    $endgroup$















      2












      2








      2





      $begingroup$


      As stated, I am having trouble trying to set up a Laplacian/Poisson Equation. I have boundary conditions with this too, and I've tried using the DirichletCondition function, but I don't know what I'm doing there either. (I have almost zero Mathematica experience, and the Wolfram site's help is just as confusing to me as the program.)



      Laplacian[V[x, y], {x, y} == 0;

      V[x, 0] == 0;
      V[x, 0.05] == 1;
      V[0, y] == 0;
      V[0.1, y] == 0;]

      Plot[{x, -0.25, 0.25}, {y, -0.15, 0.15}]


      Plot I'm getting



      While I am getting that plot to appear, it's not even close to what I need. What I'm needing is the solution to appear within the region 0 ≤ x ≤ 0.1 and 0 ≤ y ≤ 0.05, as stated by the boundary conditions (rectangular). It's supposed to be a distribution type of plot, kind of like elevation contour graphs and similar.



      And for now, the PDE I'm solving is equal to 0, so once I get that done, how do I set up the PDE when it's not equal to 0 (Poisson's Equation)? I would think that since Laplacian is a function, I can't use it anymore since the PDE isn't equal to 0 anymore.



      Help is greatly appreciated!










      share|improve this question







      New contributor




      LtGenSpartan is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.







      $endgroup$




      As stated, I am having trouble trying to set up a Laplacian/Poisson Equation. I have boundary conditions with this too, and I've tried using the DirichletCondition function, but I don't know what I'm doing there either. (I have almost zero Mathematica experience, and the Wolfram site's help is just as confusing to me as the program.)



      Laplacian[V[x, y], {x, y} == 0;

      V[x, 0] == 0;
      V[x, 0.05] == 1;
      V[0, y] == 0;
      V[0.1, y] == 0;]

      Plot[{x, -0.25, 0.25}, {y, -0.15, 0.15}]


      Plot I'm getting



      While I am getting that plot to appear, it's not even close to what I need. What I'm needing is the solution to appear within the region 0 ≤ x ≤ 0.1 and 0 ≤ y ≤ 0.05, as stated by the boundary conditions (rectangular). It's supposed to be a distribution type of plot, kind of like elevation contour graphs and similar.



      And for now, the PDE I'm solving is equal to 0, so once I get that done, how do I set up the PDE when it's not equal to 0 (Poisson's Equation)? I would think that since Laplacian is a function, I can't use it anymore since the PDE isn't equal to 0 anymore.



      Help is greatly appreciated!







      differential-equations






      share|improve this question







      New contributor




      LtGenSpartan is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.











      share|improve this question







      New contributor




      LtGenSpartan is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.









      share|improve this question




      share|improve this question






      New contributor




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      asked 3 hours ago









      LtGenSpartanLtGenSpartan

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      New contributor





      LtGenSpartan is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.






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      Check out our Code of Conduct.






















          2 Answers
          2






          active

          oldest

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          4












          $begingroup$

          Something like this?



          PDE = D[V[x, y], x, x] + D[V[x, y], y, y];

          BCs = {DirichletCondition[V[x, y] == 0, y == 0],
          DirichletCondition[V[x, y] == 1, y == 0.05],
          DirichletCondition[V[x, y] == 0, x == 0],
          DirichletCondition[V[x, y] == 0, x == 0.1]};

          ufun = NDSolveValue[{PDE == 0, BCs}, V, {x, 0, 0.1}, {y, 0, 0.05}];

          ContourPlot[ufun[x, y], {x, 0, 0.1}, {y, 0, 0.05}]


          enter image description here



          For Poisson equation replace PDE == 0 by PDE == f[x,y], where f[x,y] is an arbitrary function.






          share|improve this answer











          $endgroup$













          • $begingroup$
            Oh wow, that's exactly what I needed! Also thanks for clearing up the DirichletCondition, the way you did it was much easier than what the Wolfram site had. To make sure I understand the syntax for PDE, i.e does that mean derivative of V with respect to x, and x again (to satisfy a squared partial)?
            $endgroup$
            – LtGenSpartan
            3 hours ago












          • $begingroup$
            @LtGenSpartan Yes!
            $endgroup$
            – zhk
            3 hours ago










          • $begingroup$
            I actually have another question, is there a way to add legends, axes, etc. to this plot?
            $endgroup$
            – LtGenSpartan
            3 hours ago










          • $begingroup$
            @LtGenSpartan Of course you can. Check the documentations on Plot.
            $endgroup$
            – zhk
            3 hours ago










          • $begingroup$
            @LtGenSpartan - FrameLabel -> Automatic, PlotLegends -> Automatic
            $endgroup$
            – Bob Hanlon
            2 hours ago



















          0












          $begingroup$

          DSolve can handle the Lapalace equation if analytic is of any interest. It doesn't do well with Poisson though.



          pde = D[V[x, y], x, x] + D[V[x, y], y, y] == 0

          bc = {V[x, 0] == 0, V[x, 1/20] == 1, V[0, y] == 0, V[1/10, y] == 0}

          DSolve[{pde, bc}, V[x, y], {x, y}] // Flatten;


          It gives K[1] as the summation variable. n looks nicer.



          % /. K[1] -> n

          (*{V[x, y] -> Inactive[Sum][(4 Csch[(n π)/2] Sin[(n π)/2]^2 Sin[10 n π x] Sinh[10 n π y])/(n π), {n, 1, ∞}]}*)





          share|improve this answer









          $endgroup$













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            2 Answers
            2






            active

            oldest

            votes








            2 Answers
            2






            active

            oldest

            votes









            active

            oldest

            votes






            active

            oldest

            votes









            4












            $begingroup$

            Something like this?



            PDE = D[V[x, y], x, x] + D[V[x, y], y, y];

            BCs = {DirichletCondition[V[x, y] == 0, y == 0],
            DirichletCondition[V[x, y] == 1, y == 0.05],
            DirichletCondition[V[x, y] == 0, x == 0],
            DirichletCondition[V[x, y] == 0, x == 0.1]};

            ufun = NDSolveValue[{PDE == 0, BCs}, V, {x, 0, 0.1}, {y, 0, 0.05}];

            ContourPlot[ufun[x, y], {x, 0, 0.1}, {y, 0, 0.05}]


            enter image description here



            For Poisson equation replace PDE == 0 by PDE == f[x,y], where f[x,y] is an arbitrary function.






            share|improve this answer











            $endgroup$













            • $begingroup$
              Oh wow, that's exactly what I needed! Also thanks for clearing up the DirichletCondition, the way you did it was much easier than what the Wolfram site had. To make sure I understand the syntax for PDE, i.e does that mean derivative of V with respect to x, and x again (to satisfy a squared partial)?
              $endgroup$
              – LtGenSpartan
              3 hours ago












            • $begingroup$
              @LtGenSpartan Yes!
              $endgroup$
              – zhk
              3 hours ago










            • $begingroup$
              I actually have another question, is there a way to add legends, axes, etc. to this plot?
              $endgroup$
              – LtGenSpartan
              3 hours ago










            • $begingroup$
              @LtGenSpartan Of course you can. Check the documentations on Plot.
              $endgroup$
              – zhk
              3 hours ago










            • $begingroup$
              @LtGenSpartan - FrameLabel -> Automatic, PlotLegends -> Automatic
              $endgroup$
              – Bob Hanlon
              2 hours ago
















            4












            $begingroup$

            Something like this?



            PDE = D[V[x, y], x, x] + D[V[x, y], y, y];

            BCs = {DirichletCondition[V[x, y] == 0, y == 0],
            DirichletCondition[V[x, y] == 1, y == 0.05],
            DirichletCondition[V[x, y] == 0, x == 0],
            DirichletCondition[V[x, y] == 0, x == 0.1]};

            ufun = NDSolveValue[{PDE == 0, BCs}, V, {x, 0, 0.1}, {y, 0, 0.05}];

            ContourPlot[ufun[x, y], {x, 0, 0.1}, {y, 0, 0.05}]


            enter image description here



            For Poisson equation replace PDE == 0 by PDE == f[x,y], where f[x,y] is an arbitrary function.






            share|improve this answer











            $endgroup$













            • $begingroup$
              Oh wow, that's exactly what I needed! Also thanks for clearing up the DirichletCondition, the way you did it was much easier than what the Wolfram site had. To make sure I understand the syntax for PDE, i.e does that mean derivative of V with respect to x, and x again (to satisfy a squared partial)?
              $endgroup$
              – LtGenSpartan
              3 hours ago












            • $begingroup$
              @LtGenSpartan Yes!
              $endgroup$
              – zhk
              3 hours ago










            • $begingroup$
              I actually have another question, is there a way to add legends, axes, etc. to this plot?
              $endgroup$
              – LtGenSpartan
              3 hours ago










            • $begingroup$
              @LtGenSpartan Of course you can. Check the documentations on Plot.
              $endgroup$
              – zhk
              3 hours ago










            • $begingroup$
              @LtGenSpartan - FrameLabel -> Automatic, PlotLegends -> Automatic
              $endgroup$
              – Bob Hanlon
              2 hours ago














            4












            4








            4





            $begingroup$

            Something like this?



            PDE = D[V[x, y], x, x] + D[V[x, y], y, y];

            BCs = {DirichletCondition[V[x, y] == 0, y == 0],
            DirichletCondition[V[x, y] == 1, y == 0.05],
            DirichletCondition[V[x, y] == 0, x == 0],
            DirichletCondition[V[x, y] == 0, x == 0.1]};

            ufun = NDSolveValue[{PDE == 0, BCs}, V, {x, 0, 0.1}, {y, 0, 0.05}];

            ContourPlot[ufun[x, y], {x, 0, 0.1}, {y, 0, 0.05}]


            enter image description here



            For Poisson equation replace PDE == 0 by PDE == f[x,y], where f[x,y] is an arbitrary function.






            share|improve this answer











            $endgroup$



            Something like this?



            PDE = D[V[x, y], x, x] + D[V[x, y], y, y];

            BCs = {DirichletCondition[V[x, y] == 0, y == 0],
            DirichletCondition[V[x, y] == 1, y == 0.05],
            DirichletCondition[V[x, y] == 0, x == 0],
            DirichletCondition[V[x, y] == 0, x == 0.1]};

            ufun = NDSolveValue[{PDE == 0, BCs}, V, {x, 0, 0.1}, {y, 0, 0.05}];

            ContourPlot[ufun[x, y], {x, 0, 0.1}, {y, 0, 0.05}]


            enter image description here



            For Poisson equation replace PDE == 0 by PDE == f[x,y], where f[x,y] is an arbitrary function.







            share|improve this answer














            share|improve this answer



            share|improve this answer








            edited 3 hours ago

























            answered 3 hours ago









            zhkzhk

            9,32411433




            9,32411433












            • $begingroup$
              Oh wow, that's exactly what I needed! Also thanks for clearing up the DirichletCondition, the way you did it was much easier than what the Wolfram site had. To make sure I understand the syntax for PDE, i.e does that mean derivative of V with respect to x, and x again (to satisfy a squared partial)?
              $endgroup$
              – LtGenSpartan
              3 hours ago












            • $begingroup$
              @LtGenSpartan Yes!
              $endgroup$
              – zhk
              3 hours ago










            • $begingroup$
              I actually have another question, is there a way to add legends, axes, etc. to this plot?
              $endgroup$
              – LtGenSpartan
              3 hours ago










            • $begingroup$
              @LtGenSpartan Of course you can. Check the documentations on Plot.
              $endgroup$
              – zhk
              3 hours ago










            • $begingroup$
              @LtGenSpartan - FrameLabel -> Automatic, PlotLegends -> Automatic
              $endgroup$
              – Bob Hanlon
              2 hours ago


















            • $begingroup$
              Oh wow, that's exactly what I needed! Also thanks for clearing up the DirichletCondition, the way you did it was much easier than what the Wolfram site had. To make sure I understand the syntax for PDE, i.e does that mean derivative of V with respect to x, and x again (to satisfy a squared partial)?
              $endgroup$
              – LtGenSpartan
              3 hours ago












            • $begingroup$
              @LtGenSpartan Yes!
              $endgroup$
              – zhk
              3 hours ago










            • $begingroup$
              I actually have another question, is there a way to add legends, axes, etc. to this plot?
              $endgroup$
              – LtGenSpartan
              3 hours ago










            • $begingroup$
              @LtGenSpartan Of course you can. Check the documentations on Plot.
              $endgroup$
              – zhk
              3 hours ago










            • $begingroup$
              @LtGenSpartan - FrameLabel -> Automatic, PlotLegends -> Automatic
              $endgroup$
              – Bob Hanlon
              2 hours ago
















            $begingroup$
            Oh wow, that's exactly what I needed! Also thanks for clearing up the DirichletCondition, the way you did it was much easier than what the Wolfram site had. To make sure I understand the syntax for PDE, i.e does that mean derivative of V with respect to x, and x again (to satisfy a squared partial)?
            $endgroup$
            – LtGenSpartan
            3 hours ago






            $begingroup$
            Oh wow, that's exactly what I needed! Also thanks for clearing up the DirichletCondition, the way you did it was much easier than what the Wolfram site had. To make sure I understand the syntax for PDE, i.e does that mean derivative of V with respect to x, and x again (to satisfy a squared partial)?
            $endgroup$
            – LtGenSpartan
            3 hours ago














            $begingroup$
            @LtGenSpartan Yes!
            $endgroup$
            – zhk
            3 hours ago




            $begingroup$
            @LtGenSpartan Yes!
            $endgroup$
            – zhk
            3 hours ago












            $begingroup$
            I actually have another question, is there a way to add legends, axes, etc. to this plot?
            $endgroup$
            – LtGenSpartan
            3 hours ago




            $begingroup$
            I actually have another question, is there a way to add legends, axes, etc. to this plot?
            $endgroup$
            – LtGenSpartan
            3 hours ago












            $begingroup$
            @LtGenSpartan Of course you can. Check the documentations on Plot.
            $endgroup$
            – zhk
            3 hours ago




            $begingroup$
            @LtGenSpartan Of course you can. Check the documentations on Plot.
            $endgroup$
            – zhk
            3 hours ago












            $begingroup$
            @LtGenSpartan - FrameLabel -> Automatic, PlotLegends -> Automatic
            $endgroup$
            – Bob Hanlon
            2 hours ago




            $begingroup$
            @LtGenSpartan - FrameLabel -> Automatic, PlotLegends -> Automatic
            $endgroup$
            – Bob Hanlon
            2 hours ago











            0












            $begingroup$

            DSolve can handle the Lapalace equation if analytic is of any interest. It doesn't do well with Poisson though.



            pde = D[V[x, y], x, x] + D[V[x, y], y, y] == 0

            bc = {V[x, 0] == 0, V[x, 1/20] == 1, V[0, y] == 0, V[1/10, y] == 0}

            DSolve[{pde, bc}, V[x, y], {x, y}] // Flatten;


            It gives K[1] as the summation variable. n looks nicer.



            % /. K[1] -> n

            (*{V[x, y] -> Inactive[Sum][(4 Csch[(n π)/2] Sin[(n π)/2]^2 Sin[10 n π x] Sinh[10 n π y])/(n π), {n, 1, ∞}]}*)





            share|improve this answer









            $endgroup$


















              0












              $begingroup$

              DSolve can handle the Lapalace equation if analytic is of any interest. It doesn't do well with Poisson though.



              pde = D[V[x, y], x, x] + D[V[x, y], y, y] == 0

              bc = {V[x, 0] == 0, V[x, 1/20] == 1, V[0, y] == 0, V[1/10, y] == 0}

              DSolve[{pde, bc}, V[x, y], {x, y}] // Flatten;


              It gives K[1] as the summation variable. n looks nicer.



              % /. K[1] -> n

              (*{V[x, y] -> Inactive[Sum][(4 Csch[(n π)/2] Sin[(n π)/2]^2 Sin[10 n π x] Sinh[10 n π y])/(n π), {n, 1, ∞}]}*)





              share|improve this answer









              $endgroup$
















                0












                0








                0





                $begingroup$

                DSolve can handle the Lapalace equation if analytic is of any interest. It doesn't do well with Poisson though.



                pde = D[V[x, y], x, x] + D[V[x, y], y, y] == 0

                bc = {V[x, 0] == 0, V[x, 1/20] == 1, V[0, y] == 0, V[1/10, y] == 0}

                DSolve[{pde, bc}, V[x, y], {x, y}] // Flatten;


                It gives K[1] as the summation variable. n looks nicer.



                % /. K[1] -> n

                (*{V[x, y] -> Inactive[Sum][(4 Csch[(n π)/2] Sin[(n π)/2]^2 Sin[10 n π x] Sinh[10 n π y])/(n π), {n, 1, ∞}]}*)





                share|improve this answer









                $endgroup$



                DSolve can handle the Lapalace equation if analytic is of any interest. It doesn't do well with Poisson though.



                pde = D[V[x, y], x, x] + D[V[x, y], y, y] == 0

                bc = {V[x, 0] == 0, V[x, 1/20] == 1, V[0, y] == 0, V[1/10, y] == 0}

                DSolve[{pde, bc}, V[x, y], {x, y}] // Flatten;


                It gives K[1] as the summation variable. n looks nicer.



                % /. K[1] -> n

                (*{V[x, y] -> Inactive[Sum][(4 Csch[(n π)/2] Sin[(n π)/2]^2 Sin[10 n π x] Sinh[10 n π y])/(n π), {n, 1, ∞}]}*)






                share|improve this answer












                share|improve this answer



                share|improve this answer










                answered 12 mins ago









                Bill WattsBill Watts

                3,4411620




                3,4411620






















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