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  • 7/27/2019 Numerical performance of reduction numerical methods for single-phase flow in rough grids and with discontinuous permeability

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    Reference Reduction Methods Physical Reduction Methods Numerical Examples Summary and Conclusions

    Numerical perormance o reduction numerical methods or

    single-phase fow in rough grids and with discontinuous

    permeability

    Jiangyong Hou

    Center or Computational Geosciences, School o Mathematics and Statistics, Xian JiaotongUniversity

    October 7, 2013

    http://find/
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    Reference Reduction Methods Physical Reduction Methods Numerical Examples Summary and Conclusions

    Outline

    Reerence Reduction MethodsMulti-Point Flux Mixed Finite Element MethodMixed-Hybrid Finite Element Method

    Physical Reduction MethodsMPFA O-Method

    Local ux mimetic MPFA method

    Numerical ExamplesComparisons o robustness on quadrilateral grids

    Discontinuous experiments on triangular and quadrilateral grids

    Summary and Conclusions

    http://find/
  • 7/27/2019 Numerical performance of reduction numerical methods for single-phase flow in rough grids and with discontinuous permeability

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    Reference Reduction Methods Physical Reduction Methods Numerical Examples Summary and Conclusions

    Reerence Finite element spaces on Quadrilaterals

    a1 a2

    a3a4

    1 2

    34

    n1 n4

    n2

    n7

    n3

    n6

    n8 n5

    a1 a2

    a3a4

    n4n1

    n3

    n6

    n8n5

    n7

    n2

    Figure 1.1: A bilinear transormation on quadrilaterals.

    1() = 1()2 span{curl(2), curl(2)}

    =

    1 + 1 + 1 +

    2 + 22 + 2 + 2 2

    2

    and

    1

    2 (), =

    (1 + 1, 1 + 1) (, ) 1(1 + 1, 2 + 2) (, ) 2(2 + 2, 2 + 2) (, ) 3(2 + 2, 1 + 1) (, ) 4

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    Reference Reduction Methods Physical Reduction Methods Numerical Examples Summary and Conclusions

    Reerence Finite element spaces on Triangles

    a1 a2

    a3

    1

    2 3

    4

    56

    n1 n4

    n2

    n5n3

    n6

    a1 a2

    a3

    n4n1

    n3

    n6

    n

    5

    n2

    I II

    III

    Figure 1.2: A linear transormation on triangles.

    1() = 1()2 =

    {1 + 1 + 12 + 2 + 2

    ,

    1, 1, 1, , R2, 2, 2 R

    }and

    12 (), =

    (1 + 2 + 3)(, ) (2, 1) (, ) 1(1 + 2 + 6)(, ) (2, 1) (, ) 2(3 + 4 + 5)(, ) (5, 4) (, ) 3(2 + 3 + 4)(, ) (2, 4) (, ) 4(1 + 5 + 6)(, ) (5, 1) (, ) 5(4 + 5 + 6)(, ) (5, 4) (, ) 6

    R f R d i M h d Ph i l R d i M h d N i l E l S d C l i

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    Reference Reduction Methods Physical Reduction Methods Numerical Examples Summary and Conclusions

    Outline

    Reerence Reduction MethodsMulti-Point Flux Mixed Finite Element MethodMixed-Hybrid Finite Element Method

    Physical Reduction MethodsMPFA O-Method

    Local ux mimetic MPFA method

    Numerical ExamplesComparisons o robustness on quadrilateral grids

    Discontinuous experiments on triangular and quadrilateral grids

    Summary and Conclusions

    R f R d ti M th d Ph i l R d ti M th d N i l E l S d C l i

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    Reference Reduction Methods Physical Reduction Methods Numerical Examples Summary and Conclusions

    Multi-Point Flux Mixed Finite Element Method

    Find (u, ) (div, ) 2()

    (1u, v) (, v) = 0 v

    ( u, ) = (, )

    In quadrilateral meshes, (1u, v) can be dened by symmetric and non-

    symmetric quadratures or both 1 and 12

    In triangular meshes, the nonsymmetric quadrature o (1u, v) is only

    dened in physical 12

    Reference Reduction Methods Physical Reduction Methods Numerical Examples Summary and Conclusions

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    Reference Reduction Methods Physical Reduction Methods Numerical Examples Summary and Conclusions

    On quadrilateral meshes

    SQ1 = 14

    4=1

    ( 1

    1 )(a)u(a) v(a)

    SQ2 = 14

    4=1

    ( 1

    1 )(x,)u(a) v(a)

    NSQ1 = 14

    4=1

    ( 1

    ,

    1

    )(a)u

    (a

    ) v(a

    )

    NSQ2 = 14

    4=1

    ( 1

    1 ,)(a)u(a) v(a)

    On triangular meshes

    SQ = 16

    3

    =1( 1,

    ,

    1 ,)u(a) v(a)

    NSQ =

    =I,II,III((a3)(a3)(a1)1 )u(a3) v(a3)

    Reference Reduction Methods Physical Reduction Methods Numerical Examples Summary and Conclusions

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    Reference Reduction Methods Physical Reduction Methods Numerical Examples Summary and Conclusions

    Outline

    Reerence Reduction MethodsMulti-Point Flux Mixed Finite Element MethodMixed-Hybrid Finite Element Method

    Physical Reduction MethodsMPFA O-Method

    Local ux mimetic MPFA method

    Numerical ExamplesComparisons o robustness on quadrilateral grids

    Discontinuous experiments on triangular and quadrilateral grids

    Summary and Conclusions

    Reference Reduction Methods Physical Reduction Methods Numerical Examples Summary and Conclusions

    http://find/
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    y p y

    Mixed-Hybrid Finite Element Method

    Find (u, , )

    (1 u, v) =

    (, v)

    4=1

    (v , )

    v

    4=1

    (u ,) = 0

    ( u, ) = (, )

    where

    = {2() | v| 1() or

    12 (), }

    = e1(e) or (e), (e) is piecewise constant with discontinuity at midpointo e.

    Reference Reduction Methods Physical Reduction Methods Numerical Examples Summary and Conclusions

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    Nonsymmetric rules or Hybrid 1

    2

    For quadrilaterals

    Rule1 :

    4=1

    1

    ,1

    Rule2 : 11

    ,1 1

    + 3

    1

    ,3 1

    +2

    1 ,4 1 +4

    1 ,2 1

    Rule3 :1

    1

    ,3 1

    +

    3

    1

    ,1 1

    +2

    1

    ,2 1

    +

    4

    1

    ,4 1

    For physical triangles

    =I,II,III

    ,

    1

    Reference Reduction Methods Physical Reduction Methods Numerical Examples Summary and Conclusions

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    Outline

    Reerence Reduction MethodsMulti-Point Flux Mixed Finite Element MethodMixed-Hybrid Finite Element Method

    Physical Reduction Methods

    MPFA O-MethodLocal ux mimetic MPFA method

    Numerical ExamplesComparisons o robustness on quadrilateral grids

    Discontinuous experiments on triangular and quadrilateral grids

    Summary and Conclusions

    Reference Reduction Methods Physical Reduction Methods Numerical Examples Summary and Conclusions

    http://find/
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    MPFA O-Method

    Step1. Compute the sub-edge uxes in each subcells o the dual mesh

    a

    x4x4

    x2

    x3

    x3

    x1 x1x2n2

    n4

    n3

    n1

    = () = | n

    | = 1

    {( )

    () + ( )

    () }

    where = (x), = (x), is twice the measure o triangle xxx, () is the outer

    normal vector lying on the connection lines between the cell center x and the boundarymidpoints x which is opposite to the midpoint x, and having the same length with theedge on which it lies.

    Reference Reduction Methods Physical Reduction Methods Numerical Examples Summary and Conclusions

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    Step2. Considering the continuity o uxes between two adjacent elements

    1 = (1)

    1=

    (2)

    12 =

    (1)2 =

    (3)2

    3 = (2)3 =

    (4)3

    4 = (3)4 =

    (4)4

    and eliminating the temporary pressure at the midpoint o sub-edges,

    a

    = a

    a = a + a}

    = a = (1+ )a

    Step3. Assemble the entire edge uxes, and insert the our uxes into the localbalance equation, that is 1 + 2 + 3 + 4 =

    12

    22

    14

    24

    13 23

    11 21

    24

    3

    1

    Reference Reduction Methods Physical Reduction Methods Numerical Examples Summary and Conclusions

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    Outline

    Reerence Reduction MethodsMulti-Point Flux Mixed Finite Element MethodMixed-Hybrid Finite Element Method

    Physical Reduction Methods

    MPFA O-MethodLocal ux mimetic MPFA method

    Numerical ExamplesComparisons o robustness on quadrilateral grids

    Discontinuous experiments on triangular and quadrilateral grids

    Summary and Conclusions

    Reference Reduction Methods Physical Reduction Methods Numerical Examples Summary and Conclusions

    http://goforward/http://find/http://goback/
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    Local fux mimetic MPFA method

    The discretization o the local ux mimetic MPFA in the discrete operator sense:

    u =

    u =

    and in an equivalent variational orm:

    Find (u, )

    [u, v] [, v] = 0 v

    [ u, ] = [, ]

    Reference Reduction Methods Physical Reduction Methods Numerical Examples Summary and Conclusions

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    an2

    e2

    n1

    e1

    x2,

    x1,

    x

    Figure 2.1: a = (n1,n2), a =(

    12|e1|(x1, x),

    12|e2|(x x2,)

    )

    Symmetric quadrature

    [u, v],,a =||

    1a

    1 a

    u,a v,a

    Nonsymmetric quadrature

    [u, v],,a = a1

    a

    u,a v,a

    Reference Reduction Methods Physical Reduction Methods Numerical Examples Summary and Conclusions

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    Outline

    Reerence Reduction MethodsMulti-Point Flux Mixed Finite Element MethodMixed-Hybrid Finite Element Method

    Physical Reduction Methods

    MPFA O-MethodLocal ux mimetic MPFA method

    Numerical ExamplesComparisons o robustness on quadrilateral gridsDiscontinuous experiments on triangular and quadrilateral grids

    Summary and Conclusions

    Reference Reduction Methods Physical Reduction Methods Numerical Examples Summary and Conclusions

    http://find/
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    Comparisons o robustness on quadrilateral grids

    (a) slightly perturbed square mesh (b) 2-parallelogram mesh

    (c) -perturbed quadrilateral mesh (d) smooth mesh

    Figure 3.1: Quadrilateral meshes used in numerical tests

    Reference Reduction Methods Physical Reduction Methods Numerical Examples Summary and Conclusions

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    Three quality measures dened or the general quadrilaterals

    1() =

    2 ,

    2() =

    |e|,|e|,

    3() = 1

    |e|, |e|,

    |e|,

    2

    12

    and

    = {() : },

    =

    1

    (), = 1, 2, 3. (3.1)

    Mesh 1 2 3 1 2 3

    Square 0.7071 1 1 0.7071 1 1Slightly perturbed 0.2333 0.1848 0.2094 0.5643 0.6637 0.62082-parallelogram 0.3187 0.3333 0.3261 0.4863 0.6186 0.5617

    Heavily perturbed 0.0052 0.0155 0.0283 0.4512 0.4871 0.4725Smooth 0.4036 0.4933 0.4595 0.5040 0.6898 0.6131

    Table 3.1: The qualities o each meshes at the last refnement step

    Reference Reduction Methods Physical Reduction Methods Numerical Examples Summary and Conclusions

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    The problem

    () = in

    = on

    Analytical Solution:

    (, ) = ( 1)( 1)(32 + ( 1)sin(2)cos(0.5 1 + ))

    The tensor coecient:

    (, ) =

    ( + 1)2 + 2

    ( + 1)2

    Reference Reduction Methods Physical Reduction Methods Numerical Examples Summary and Conclusions

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    1 2 3 4 5 6 7-14

    -13

    -12

    -11

    -10

    -9

    -8

    -7

    log2(1/h)

    log2

    (eL2)

    L2 Pressure Error on square mesh

    MPFA

    MFMFES1

    BDM

    MFMFENS1

    BDM

    MFMFES2

    BRT

    MFMFENS2

    BRT

    LFMFDS

    LFMFDNS

    MHS

    BDM

    MHS

    BRT

    MHNS1

    BRT

    MHNS2

    BRT

    MHNS3

    BRT

    (a) Pressure error and convergence rate

    1 2 3 4 5 6 7-13

    -12

    -11

    -10

    -9

    -8

    -7

    -6

    -5

    -4

    -3

    log2(1/h)

    log2

    (eL2)

    L Velocity Error on square mesh

    MPFA

    MFMFES1

    BDM

    MFMFENS1

    BDM

    MFMFES2

    BRT

    MFMFENS2

    BRT

    LFMFDS

    LFMFDNS

    MHS

    BDM

    MHS

    BRT

    MHNS1

    BRT

    MHNS2

    BRT

    MHNS3

    BRT

    (b) Velocity error and convergence rate

    Figure 3.2: Error and convergence rate on square mesh

    Reference Reduction Methods Physical Reduction Methods Numerical Examples Summary and Conclusions

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    1 2 3 4 5 6 7-14

    -13

    -12

    -11

    -10

    -9

    -8

    -7

    log2(1/h)

    log2

    (eL2)

    L2 Pressure Error on slightly perturbed square mesh

    MPFA

    MFMFES1

    BDM

    MFMFENS1

    BDM

    MFMFES2

    BRT

    MFMFENS2

    BRT

    LFMFDS

    LFMFDNS

    MHS

    BDM

    MHS

    BRT

    MHNS1

    BRT

    MHNS2

    BRT

    MHNS3

    BRT

    (a) Pressure error and convergence rate

    1 2 3 4 5 6 7-13

    -12

    -11

    -10

    -9

    -8

    -7

    -6

    -5

    -4

    -3

    log2(1/h)

    log2

    (eL2)

    L2

    Velocity Error on slightly perturbed square mesh

    MPFA

    MFMFES1

    BDM

    MFMFENS1

    BDM

    MFMFES2

    BRT

    MFMFENS2

    BRT

    LFMFDS

    LFMFDNS

    MHS

    BDM

    MHS

    BRT

    MHNS1

    BRT

    MHNS2

    BRT

    MHNS3

    BRT

    (b) Velocity error and convergence rate

    Figure 3.3: Error and convergence rate on slightly perturbed square mesh

    Reference Reduction Methods Physical Reduction Methods Numerical Examples Summary and Conclusions

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    1 2 3 4 5 6 7-14

    -13

    -12

    -11

    -10

    -9

    -8

    -7

    log2(1/h)

    log2

    (eL2)

    L Pressure Error on h -parallelogram mesh

    MPFA

    MFMFES1

    BDM

    MFMFENS1

    BDM

    MFMFES2

    BRT

    MFMFENS2

    BRT

    LFMFDS

    LFMFDNS

    MHS

    BDM

    MHS

    BRT

    MHNS1

    BRT

    MHNS2

    BRT

    MHNS3

    BRT

    (a) Pressure error and convergence rate

    1 2 3 4 5 6 7-13

    -12

    -11

    -10

    -9

    -8

    -7

    -6

    -5

    -4

    -3

    log2(1/h)

    log2

    (eL2)

    L Velocity Error on h -parallelogram mesh

    MPFA

    MFMFES1

    BDM

    MFMFENS1

    BDM

    MFMFES2

    BRT

    MFMFENS2

    BRT

    LFMFDS

    LFMFDNS

    MHS

    BDM

    MHS

    BRT

    MHNS1

    BRT

    MHNS2

    BRT

    MHNS3

    BRT

    (b) Velocity error and convergence rate

    Figure 3.4: Error and convergence rate on 2-parallelogram mesh

    Reference Reduction Methods Physical Reduction Methods Numerical Examples Summary and Conclusions

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    1 2 3 4 5 6 7-14

    -13

    -12

    -11

    -10

    -9

    -8

    -7

    log2(1/h)

    log2

    (eL2)

    L Pressure Error on heavily h-perturbed quadrilateral mesh

    MPFA

    MFMFES1

    BDM

    MFMFENS1

    BDM

    MFMFES2

    BRT

    MFMFENS2

    BRT

    LFMFDS

    LFMFDNS

    MHS

    BDM

    MHS

    BRT

    MHNS1

    BRT

    MHNS2

    BRT

    MHNS3

    BRT

    (a) Pressure error and convergence rate

    1 2 3 4 5 6 7-11

    -10

    -9

    -8

    -7

    -6

    -5

    -4

    -3

    log2(1/h)

    log2

    (eL2)

    L Velocity Error on heavily h-perturbed quadrilateral mesh

    MPFA

    MFMFES1

    BDM

    MFMFENS1

    BDM

    MFMFES2

    BRT

    MFMFENS2

    BRT

    LFMFDS

    LFMFDNS

    MHS

    BDM

    MHS

    BRT

    MHNS1

    BRT

    MHNS2

    BRT

    MHNS3

    BRT

    (b) Velocity error and convergence rate

    Figure 3.5: Error and convergence rate on heavily -perturbed quadrilateral mesh

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    (a) Global (b) Local

    Figure 3.6: The last refnement o-perturbed quadrilateral mesh

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    5.6 5.7 5.8 5.9 6 6.1 6.2

    -13.1

    -13

    -12.9

    -12.8

    -12.7

    -12.6

    -12.5

    -12.4

    -12.3

    log2(1/h)

    log2

    (eL2

    )

    L2

    Pressure Error on heavily h-perturbed quadrilateral mesh

    MPFA

    MFMFES1

    BDM

    MFMFENS1

    BDM

    MFMFES2

    BRT

    MFMFENS2

    BRT

    LFMFDS

    LFMFDNS

    MHS

    BDM

    MHS

    BRT

    MHNS1

    BRT

    MHNS2

    BRT

    MHNS3

    BRT

    Figure 3.7: Partial enlargement o error and convergence o pressure in Figure 3.5a

    Reference Reduction Methods Physical Reduction Methods Numerical Examples Summary and Conclusions

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    1 2 3 4 5 6 7-14

    -13

    -12

    -11

    -10

    -9

    -8

    -7

    log2(1/h)

    log2

    (eL2)

    L Pressure Error on smooth mesh

    MPFA

    MFMFES1

    BDM

    MFMFENS1

    BDM

    MFMFES2

    BRT

    MFMFENS2 BRT

    LFMFDS

    LFMFDNS

    MHS

    BDM

    MHS

    BRT

    MHNS1

    BRT

    MHNS2

    BRT

    MHNS3

    BRT

    (a) Pressure error and convergence rate

    1 2 3 4 5 6 7-12

    -11

    -10

    -9

    -8

    -7

    -6

    -5

    -4

    -3

    log2(1/h)

    log2

    (eL2)

    L Velocity Error on smooth mesh

    MPFA

    MFMFES1

    BDM

    MFMFENS1

    BDM

    MFMFES2

    BRT

    MFMFENS2 BRT

    LFMFDS

    LFMFDNS

    MHS

    BDM

    MHS

    BRT

    MHNS1

    BRT

    MHNS2

    BRT

    MHNS3

    BRT

    (b) Velocity error and convergence rate

    Figure 3.8: Error and convergence rate on smooth mesh

    Reference Reduction Methods Physical Reduction Methods Numerical Examples Summary and Conclusions

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    Outline

    Reerence Reduction MethodsMulti-Point Flux Mixed Finite Element MethodMixed-Hybrid Finite Element Method

    Physical Reduction Methods

    MPFA O-MethodLocal ux mimetic MPFA method

    Numerical ExamplesComparisons o robustness on quadrilateral gridsDiscontinuous experiments on triangular and quadrilateral grids

    Summary and Conclusions

    Reference Reduction Methods Physical Reduction Methods Numerical Examples Summary and Conclusions

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    Considering the the ollowing discontinuous examples which are taken rom [Eigestad,2005,Aavatsmark,2006].

    2

    3

    1102

    1 102

    (a) =0.13448835

    2

    3

    110

    1 10

    (b) =0.41033296

    2

    3

    103103

    103 1

    (c) =1.47865601

    For (a) and (b), considering the solution

    (, ) = (cos() + sin()),

    For (c), the solution is

    (, ) =

    cos( /3) or [0, 2/3],cos(/3)

    cos(2/3) cos(4/3 ) or [2/3, 2].

    Reference Reduction Methods Physical Reduction Methods Numerical Examples Summary and Conclusions

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    Discontinuous experiments on quadrilateral grids

    0 1 2 3 4 5 6-4.5

    -4

    -3.5

    -3

    -2.5

    -2

    -1.5

    -1

    log2(1/h)

    log2

    (eL2)

    L2 Pressure Error of discontinuous solution

    MPFA

    MFMFES1

    BDM

    MFMFENS1

    BDM

    MFMFES2

    BRT

    MFMFENS2

    BRT

    LFMFDS

    LFMFDNS

    MHS

    BDM

    MHS

    BRT

    MHNS1

    BRT

    MHNS2

    BRT

    MHNS3

    BRT

    (d) Pressure error and convergence rate

    0 1 2 3 4 5 64

    4.2

    4.4

    4.6

    4.8

    5

    5.2

    5.4

    5.6

    5.8

    6

    log2(1/h)

    log2

    (eL2)

    L Velocity Error of discontinuous solution

    MPFA

    MFMFES1

    BDM

    MFMFENS1

    BDM

    MFMFES2

    BRT

    MFMFENS2

    BRT

    LFMFD

    SLFMFD

    NS

    MHS

    BDM

    MHS

    BRT

    MHNS1

    BRT

    MHNS2

    BRT

    MHNS3

    BRT

    (e) Velocity error and convergence rateFigure 3.9: =0.13448835 on quadrilateral grids

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    0 1 2 3 4 5 6-7

    -6

    -5

    -4

    -3

    -2

    -1

    log2(1/h)

    log2

    (eL2)

    L2 Pressure Error of discontinuous solution

    MPFA

    MFMFES1

    BDM

    MFMFENS1

    BDM

    MFMFES2

    BRT

    MFMFENS2 BRT

    LFMFDS

    LFMFDNS

    MHS

    BDM

    MHS

    BRT

    MHNS1

    BRT

    MHNS2

    BRT

    MHNS3

    BRT

    (a) Pressure error and convergence rate

    0 1 2 3 4 5 6-0.5

    0

    0.5

    1

    1.5

    2

    2.5

    3

    3.5

    log2(1/h)

    log2

    (eL2)

    L2 Velocity Error of discontinuous solution

    MPFA

    MFMFES1

    BDM

    MFMFENS1

    BDM

    MFMFES2

    BRT

    MFMFENS2 BRT

    LFMFDS

    LFMFDNS

    MHS

    BDM

    MHS

    BRT

    MHNS1

    BRT

    MHNS2

    BRT

    MHNS3

    BRT

    (b) Velocity error and convergence rate

    Figure 3.10: =0.41033296 on quadrilateral grids

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    0 1 2 3 4 5 6-8

    -7

    -6

    -5

    -4

    -3

    -2

    log2(1/h)

    log2

    (eL2)

    L Pressure Error of discontinuous solution

    MPFA

    MFMFES1

    BDM

    MFMFENS1

    BDM

    MFMFES2

    BRT

    MFMFENS2 BRT

    LFMFDS

    LFMFDNS

    MHS

    BDM

    MHS

    BRT

    MHNS1

    BRT

    MHNS2

    BRT

    MHNS3

    BRT

    (a) Pressure error and convergence rate

    0 1 2 3 4 5 6-8

    -6

    -4

    -2

    0

    2

    4

    6

    log2(1/h)

    log2

    (eL2)

    L Velocity Error of discontinuous solution

    MPFA

    MFMFES1

    BDM

    MFMFENS1

    BDM

    MFMFES2

    BRT

    MFMFENS2

    BRT

    LFMFDS

    LFMFDNS

    MHS

    BDM

    MHS

    BRT

    MHNS1

    BRT

    MHNS2

    BRT

    MHNS3 BRT

    (b) Velocity error and convergence rate

    Figure 3.11: =1.47865601 on quadrilateral grids

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    Discontinuous experiments on triangular grids

    0 1 2 3 4 5 6-4.5

    -4

    -3.5

    -3

    -2.5

    -2

    -1.5

    -1

    log2(1/h)

    log2

    (eL2)

    L Pressure Error on triangular mesh

    MFMFES

    BDM

    MFMFES

    BRT

    MFMFENS BRT

    LFMFDS

    LFMFDNS

    MHS

    BDM

    MHS

    BRT

    MHNS

    BRT

    (a) Pressure error and convergence rate

    0 1 2 3 4 5 64.5

    4.6

    4.7

    4.8

    4.9

    5

    5.1

    5.2

    5.3

    5.4

    5.5

    log2(1/h)

    log2

    (eL2)

    L2 Velocity Error on t riangular mesh

    MFMFES

    BDM

    MFMFES

    BRT

    MFMFENS BRT

    LFMFDS

    LFMFDNS

    MHS

    BDM

    MHS

    BRT

    MHNS

    BRT

    (b) Velocity error and convergence rate

    Figure 3.12: =0.13448835 on triangular mesh

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    0 1 2 3 4 5 6-7

    -6

    -5

    -4

    -3

    -2

    -1

    log2(1/h)

    log2

    (eL2)

    L2 Pressure Error on triangular mesh

    MFMFES BDM

    MFMFES

    BRT

    MFMFENS

    BRT

    LFMFDS

    LFMFDNS

    MHS

    BDM

    MHS

    BRT

    MHNS

    BRT

    (a) Pressure error and convergence rate

    0 1 2 3 4 5 6-1

    -0.5

    0

    0.5

    1

    1.5

    2

    2.5

    3

    log2(1/h)

    log2

    (eL2)

    L2 Velocity Error on triangular mesh

    MFMFES BDM

    MFMFES

    BRT

    MFMFENS

    BRT

    LFMFDS

    LFMFDNS

    MHS

    BDM

    MHS

    BRT

    MHNS

    BRT

    (b) Velocity error and convergence rate

    Figure 3.13: =0.41033296 on triangular mesh

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    0 1 2 3 4 5 6-8

    -7

    -6

    -5

    -4

    -3

    -2

    log2(1/h)

    log2

    (eL2)

    L Pressure Error on triangular mesh

    MFMFES BDM

    MFMFES

    BRT

    MFMFENS

    BRT

    LFMFDS

    LFMFDNS

    MHS

    BDM

    MHS

    BRT

    MHNS

    BRT

    (a) Pressure error and convergence rate

    0 1 2 3 4 5 6-8

    -6

    -4

    -2

    0

    2

    4

    6

    log2(1/h)

    log2

    (eL2)

    L Velocity Error on triangular mesh

    MFMFES BDM

    MFMFES

    BRT

    MFMFENS

    BRT

    LFMFDS

    LFMFDNS

    MHS

    BDM

    MHS

    BRT

    MHNS

    BRT

    (b) Velocity error and convergence rate

    Figure 3.14: =1.47865601 on the triangular meshes

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    Summary and Conclusions

    MFMFE

    Quadrature NS2 just do little better that S1 and S2, and is not as robustas NS1.

    Mixed-Hybrid 1

    2

    On quadrilaterals:The velocity o MHNS1,MHNS2 and MHNS3 still could converge in thelast step o heavily perturbed grids and have rate close to 0.35(NS1),0.43(NS2) and 0.32 (NS3) respectively. Although these methods haverobust convergence order, their errors are not the best.

    On triangles:

    The NS quadrature o Mixed-Hybrid 1

    2 dened on physical trianglesis not robust on the distorted meshes.

    Mixed-Hybrid 1 It is the most accurate and robust among these methods, however, all

    the hybrid methods are less simple and computationally ecient.

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    MPFA O-method

    For the extreme case o solution with singularity =0.13448835, theerror o normal uxes o MPFA-O dened on quadrilateral grids is thebest.

    Local ux mimetic MPFA

    The error o its normal ux is larger than other methods on both trian-gular and quadrilateral grids.

    The diferences o the convergence behaviors o pressures in all these methodsare relatively small.

    References

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    [Aavatsmark,2002] I. AavatsmarkAn introduction to multipoint ux approximations or quadrilateral grids,Comput Geosci 6(2002), 405-432.

    [Eigestad,2005] G. T. Eigestad and R. A. KlausenOn the convergence o the multi-point ux approximation O-method: Numerical ex-periments or discontinuous permeability.

    Numer Methods Partial Dif Eqns 21(2005), 1079-1098.[Wheeler,2006] M. F. Wheeler and I. Yotov,

    A multipoint ux mixed nite element method,SIAM J Numer Anal 44(2006), 2082-2106.

    [Klausen,2006] R. A. Klausen and R. Winther,Robust convergence o multipoint ux approximations on rough grids,

    Numer Math 104(2006), 317-337.

    References

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    [Aavatsmark,2006] I. Aavatsmark, G.T. Eigestad, R.A. Klausen,Numerical convergence o the MPFA O-method or general quadrilateral grids in twoand three dimensions,IMA Vol Math Appl, Springer, New York, 142(2006), 1-21.

    [Klausen,2008] R.A. Klausen, F.A. Radu, G.T. Eigestad,

    Convergence o MPFA on triangulations and or Richards equation,Int.J.Numer.Methods Fluids, 1-25(2008).

    [Lipnikov,2009] K. Lipnikov, M. Shashkov and I. Yotov,Local ux mimetic nite diference methods,Numer Math 112(2009), 115-152.

    References

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    Thank you for your attention!

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