Shape function in Finite Element Method

The name of the pictureThe name of the pictureThe name of the pictureClash Royale CLAN TAG#URR8PPP











up vote
-1
down vote

favorite












Why is it that the choice of polynomial for 6-nodes rectangular element(linear in sides 1 and 3, quadratic in sides 2 and 4) in FEM does not follow normal pascal triangle regular arrangement? i.e $u=c_1+c_2x+c_3y+c_4xy+c_5xy^2+c_6x^2y$ .










share|cite|improve this question



















  • 2




    Welcome to MSE. For some basic information about writing mathematics at this site see, e.g., basic help on mathjax notation, mathjax tutorial and quick reference, main meta site math tutorial and equation editing how-to.
    – José Carlos Santos
    Sep 5 at 10:37














up vote
-1
down vote

favorite












Why is it that the choice of polynomial for 6-nodes rectangular element(linear in sides 1 and 3, quadratic in sides 2 and 4) in FEM does not follow normal pascal triangle regular arrangement? i.e $u=c_1+c_2x+c_3y+c_4xy+c_5xy^2+c_6x^2y$ .










share|cite|improve this question



















  • 2




    Welcome to MSE. For some basic information about writing mathematics at this site see, e.g., basic help on mathjax notation, mathjax tutorial and quick reference, main meta site math tutorial and equation editing how-to.
    – José Carlos Santos
    Sep 5 at 10:37












up vote
-1
down vote

favorite









up vote
-1
down vote

favorite











Why is it that the choice of polynomial for 6-nodes rectangular element(linear in sides 1 and 3, quadratic in sides 2 and 4) in FEM does not follow normal pascal triangle regular arrangement? i.e $u=c_1+c_2x+c_3y+c_4xy+c_5xy^2+c_6x^2y$ .










share|cite|improve this question















Why is it that the choice of polynomial for 6-nodes rectangular element(linear in sides 1 and 3, quadratic in sides 2 and 4) in FEM does not follow normal pascal triangle regular arrangement? i.e $u=c_1+c_2x+c_3y+c_4xy+c_5xy^2+c_6x^2y$ .







finite-element-method






share|cite|improve this question















share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited Sep 8 at 17:23









Han de Bruijn

12k22260




12k22260










asked Sep 5 at 10:32









COLLINS AKEREMALE

1




1







  • 2




    Welcome to MSE. For some basic information about writing mathematics at this site see, e.g., basic help on mathjax notation, mathjax tutorial and quick reference, main meta site math tutorial and equation editing how-to.
    – José Carlos Santos
    Sep 5 at 10:37












  • 2




    Welcome to MSE. For some basic information about writing mathematics at this site see, e.g., basic help on mathjax notation, mathjax tutorial and quick reference, main meta site math tutorial and equation editing how-to.
    – José Carlos Santos
    Sep 5 at 10:37







2




2




Welcome to MSE. For some basic information about writing mathematics at this site see, e.g., basic help on mathjax notation, mathjax tutorial and quick reference, main meta site math tutorial and equation editing how-to.
– José Carlos Santos
Sep 5 at 10:37




Welcome to MSE. For some basic information about writing mathematics at this site see, e.g., basic help on mathjax notation, mathjax tutorial and quick reference, main meta site math tutorial and equation editing how-to.
– José Carlos Santos
Sep 5 at 10:37










1 Answer
1






active

oldest

votes

















up vote
0
down vote













enter image description here

See above picture: there are only (linear) line segments in vertical direction.
And because of the three nodal points, there are two quadratic elements in horizontal direction. A reference for the latter:



  • Understand 1D FEM solution using quadratics elements

Therefore the interpolation must be linear in $,y,$ and quadratic in $,x,$. According to a Cartesian product:
$$
(1,y) times (1,x,x^2) = (1,x,x^2,y,yx,yx^2)
$$
Mind that your term with $y^2$ is absent now and two terms with $x^2$ are present.
So the correct interpolation may be formulated as:
$$
u=c_1+c_2x+c_3y+c_4xy+colorredc_5x^2+c_6x^2y
$$






share|cite|improve this answer




















    Your Answer




    StackExchange.ifUsing("editor", function ()
    return StackExchange.using("mathjaxEditing", function ()
    StackExchange.MarkdownEditor.creationCallbacks.add(function (editor, postfix)
    StackExchange.mathjaxEditing.prepareWmdForMathJax(editor, postfix, [["$", "$"], ["\\(","\\)"]]);
    );
    );
    , "mathjax-editing");

    StackExchange.ready(function()
    var channelOptions =
    tags: "".split(" "),
    id: "69"
    ;
    initTagRenderer("".split(" "), "".split(" "), channelOptions);

    StackExchange.using("externalEditor", function()
    // Have to fire editor after snippets, if snippets enabled
    if (StackExchange.settings.snippets.snippetsEnabled)
    StackExchange.using("snippets", function()
    createEditor();
    );

    else
    createEditor();

    );

    function createEditor()
    StackExchange.prepareEditor(
    heartbeatType: 'answer',
    convertImagesToLinks: true,
    noModals: false,
    showLowRepImageUploadWarning: true,
    reputationToPostImages: 10,
    bindNavPrevention: true,
    postfix: "",
    noCode: true, onDemand: true,
    discardSelector: ".discard-answer"
    ,immediatelyShowMarkdownHelp:true
    );



    );













     

    draft saved


    draft discarded


















    StackExchange.ready(
    function ()
    StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fmath.stackexchange.com%2fquestions%2f2906115%2fshape-function-in-finite-element-method%23new-answer', 'question_page');

    );

    Post as a guest






























    1 Answer
    1






    active

    oldest

    votes








    1 Answer
    1






    active

    oldest

    votes









    active

    oldest

    votes






    active

    oldest

    votes








    up vote
    0
    down vote













    enter image description here

    See above picture: there are only (linear) line segments in vertical direction.
    And because of the three nodal points, there are two quadratic elements in horizontal direction. A reference for the latter:



    • Understand 1D FEM solution using quadratics elements

    Therefore the interpolation must be linear in $,y,$ and quadratic in $,x,$. According to a Cartesian product:
    $$
    (1,y) times (1,x,x^2) = (1,x,x^2,y,yx,yx^2)
    $$
    Mind that your term with $y^2$ is absent now and two terms with $x^2$ are present.
    So the correct interpolation may be formulated as:
    $$
    u=c_1+c_2x+c_3y+c_4xy+colorredc_5x^2+c_6x^2y
    $$






    share|cite|improve this answer
























      up vote
      0
      down vote













      enter image description here

      See above picture: there are only (linear) line segments in vertical direction.
      And because of the three nodal points, there are two quadratic elements in horizontal direction. A reference for the latter:



      • Understand 1D FEM solution using quadratics elements

      Therefore the interpolation must be linear in $,y,$ and quadratic in $,x,$. According to a Cartesian product:
      $$
      (1,y) times (1,x,x^2) = (1,x,x^2,y,yx,yx^2)
      $$
      Mind that your term with $y^2$ is absent now and two terms with $x^2$ are present.
      So the correct interpolation may be formulated as:
      $$
      u=c_1+c_2x+c_3y+c_4xy+colorredc_5x^2+c_6x^2y
      $$






      share|cite|improve this answer






















        up vote
        0
        down vote










        up vote
        0
        down vote









        enter image description here

        See above picture: there are only (linear) line segments in vertical direction.
        And because of the three nodal points, there are two quadratic elements in horizontal direction. A reference for the latter:



        • Understand 1D FEM solution using quadratics elements

        Therefore the interpolation must be linear in $,y,$ and quadratic in $,x,$. According to a Cartesian product:
        $$
        (1,y) times (1,x,x^2) = (1,x,x^2,y,yx,yx^2)
        $$
        Mind that your term with $y^2$ is absent now and two terms with $x^2$ are present.
        So the correct interpolation may be formulated as:
        $$
        u=c_1+c_2x+c_3y+c_4xy+colorredc_5x^2+c_6x^2y
        $$






        share|cite|improve this answer












        enter image description here

        See above picture: there are only (linear) line segments in vertical direction.
        And because of the three nodal points, there are two quadratic elements in horizontal direction. A reference for the latter:



        • Understand 1D FEM solution using quadratics elements

        Therefore the interpolation must be linear in $,y,$ and quadratic in $,x,$. According to a Cartesian product:
        $$
        (1,y) times (1,x,x^2) = (1,x,x^2,y,yx,yx^2)
        $$
        Mind that your term with $y^2$ is absent now and two terms with $x^2$ are present.
        So the correct interpolation may be formulated as:
        $$
        u=c_1+c_2x+c_3y+c_4xy+colorredc_5x^2+c_6x^2y
        $$







        share|cite|improve this answer












        share|cite|improve this answer



        share|cite|improve this answer










        answered Sep 8 at 18:20









        Han de Bruijn

        12k22260




        12k22260



























             

            draft saved


            draft discarded















































             


            draft saved


            draft discarded














            StackExchange.ready(
            function ()
            StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fmath.stackexchange.com%2fquestions%2f2906115%2fshape-function-in-finite-element-method%23new-answer', 'question_page');

            );

            Post as a guest













































































            這個網誌中的熱門文章

            How to combine Bézier curves to a surface?

            Mutual Information Always Non-negative

            Why am i infinitely getting the same tweet with the Twitter Search API?