# American Institute of Mathematical Sciences

## A new weak gradient for the stabilizer free weak Galerkin method with polynomial reduction

 1 Department of Mathematics, University of Arkansas at Little Rock, Little Rock, AR 72204, USA 2 Department of Mathematical Sciences, University of Delaware, Newark, DE 19716, USA

* Corresponding author: Shangyou Zhang

Received  April 2020 Revised  August 2020 Published  September 2020

Fund Project: The first author was supported in part by National Science Foundation Grant DMS-1620016

The weak Galerkin (WG) finite element method is an effective and flexible general numerical technique for solving partial differential equations. It is a natural extension of the classic conforming finite element method for discontinuous approximations, which maintains simple finite element formulation. Stabilizer free weak Galerkin methods further simplify the WG methods and reduce computational complexity. This paper explores the possibility of optimal combination of polynomial spaces that minimize the number of unknowns in the stabilizer free WG schemes without compromising the accuracy of the numerical approximation. A new stabilizer free weak Galerkin finite element method is proposed and analyzed with polynomial degree reduction. To achieve such a goal, a new definition of weak gradient is introduced. Error estimates of optimal order are established for the corresponding WG approximations in both a discrete $H^1$ norm and the standard $L^2$ norm. The numerical examples are tested on various meshes and confirm the theory.

Citation: Xiu Ye, Shangyou Zhang. A new weak gradient for the stabilizer free weak Galerkin method with polynomial reduction. Discrete & Continuous Dynamical Systems - B, doi: 10.3934/dcdsb.2020277
##### References:

show all references

##### References:
Example 1. The first three triangular grids
Example 2. The first three triangular grids
Example 3. The first three rectangular grids
Example 4. The first three polygonal grids
Weak gradient calculated by (1.4), ${{|||}}\cdot{{|||}} = O(h^{r_1})$ and $\|\cdot\| = O(h^{r_2})$
 $P_{k}(T)$ $P_{k-1}(e)$ $[P_{k+1}(T)]^d$ $r_1$ $r_2$ $P_1(T)$ $P_0(e)$ $[P_2(T)]^2$ $0$ $0$ $P_2(T)$ $P_1(e)$ $[P_3(T)]^2$ $1$ $2$ $P_3(T)$ $P_2(e)$ $[P_4(T)]^2$ $2$ $3$
 $P_{k}(T)$ $P_{k-1}(e)$ $[P_{k+1}(T)]^d$ $r_1$ $r_2$ $P_1(T)$ $P_0(e)$ $[P_2(T)]^2$ $0$ $0$ $P_2(T)$ $P_1(e)$ $[P_3(T)]^2$ $1$ $2$ $P_3(T)$ $P_2(e)$ $[P_4(T)]^2$ $2$ $3$
Weak gradient calculated by (2.3), ${{|||}}\cdot{{|||}} = O(h^{r_1})$ and $\|\cdot\| = O(h^{r_2})$
 $P_{k}(T)$ $P_{k-1}(e)$ $[P_{k+1}(T)]^d$ $r_1$ $r_2$ $P_1(T)$ $P_0(e)$ $[P_2(T)]^2$ $1$ $2$ $P_2(T)$ $P_1(e)$ $[P_3(T)]^2$ $2$ $3$ $P_3(T)$ $P_2(e)$ $[P_4(T)]^2$ $3$ $4$
 $P_{k}(T)$ $P_{k-1}(e)$ $[P_{k+1}(T)]^d$ $r_1$ $r_2$ $P_1(T)$ $P_0(e)$ $[P_2(T)]^2$ $1$ $2$ $P_2(T)$ $P_1(e)$ $[P_3(T)]^2$ $2$ $3$ $P_3(T)$ $P_2(e)$ $[P_4(T)]^2$ $3$ $4$
Example 1. The $P_k-P_{k-1}-[P_{k+1}]^2$ element, on triangular grids shown in Figure 5.1
 $k$ ${{\mathcal T}}_l$ ${{|||}} Q_hu-u_h{{|||}}$ Rate $\|Q_hu-u_h\|$ Rate 6 0.3871E-01 1.00 0.3306E-03 1.99 1 7 0.1937E-01 1.00 0.8279E-04 2.00 8 0.9685E-02 1.00 0.2070E-04 2.00 6 0.4131E-03 1.98 0.1783E-05 2.95 2 7 0.1038E-03 1.99 0.2268E-06 2.97 8 0.2602E-04 2.00 0.2859E-07 2.99 5 0.2925E-04 2.99 0.1515E-06 3.98 3 6 0.3665E-05 3.00 0.9518E-08 3.99 7 0.4587E-06 3.00 0.5963E-09 4.00 5 0.4091E-06 3.99 0.1592E-08 4.97 4 6 0.2568E-07 3.99 0.5026E-10 4.99 7 0.1608E-08 4.00 0.1610E-11 4.96
 $k$ ${{\mathcal T}}_l$ ${{|||}} Q_hu-u_h{{|||}}$ Rate $\|Q_hu-u_h\|$ Rate 6 0.3871E-01 1.00 0.3306E-03 1.99 1 7 0.1937E-01 1.00 0.8279E-04 2.00 8 0.9685E-02 1.00 0.2070E-04 2.00 6 0.4131E-03 1.98 0.1783E-05 2.95 2 7 0.1038E-03 1.99 0.2268E-06 2.97 8 0.2602E-04 2.00 0.2859E-07 2.99 5 0.2925E-04 2.99 0.1515E-06 3.98 3 6 0.3665E-05 3.00 0.9518E-08 3.99 7 0.4587E-06 3.00 0.5963E-09 4.00 5 0.4091E-06 3.99 0.1592E-08 4.97 4 6 0.2568E-07 3.99 0.5026E-10 4.99 7 0.1608E-08 4.00 0.1610E-11 4.96
Example 2. The $P_k-P_{k-1}-[P_{k+1}]^2$ element, on rectangular grids shown in Figure 5.2
 $k$ ${{\mathcal T}}_l$ ${{|||}} Q_hu-u_h{{|||}}$ Rate $\|Q_hu-u_h\|$ Rate 6 0.120E-02 2.01 0.141E-01 2.00 1 7 0.300E-03 2.00 0.354E-02 2.00 8 0.749E-04 2.00 0.885E-03 2.00 6 0.5734E-03 2.00 0.1482E-05 3.00 2 7 0.1434E-03 2.00 0.1852E-06 3.00 8 0.3584E-04 2.00 0.2314E-07 3.00 5 0.3645E-04 3.00 0.1360E-06 3.99 3 6 0.4559E-05 3.00 0.8517E-08 4.00 7 0.5699E-06 3.00 0.5326E-09 4.00 5 0.4222E-06 4.00 0.9119E-09 5.01 4 6 0.2639E-07 4.00 0.2846E-10 5.00 7 0.1650E-08 4.00 0.1110E-11 4.68
 $k$ ${{\mathcal T}}_l$ ${{|||}} Q_hu-u_h{{|||}}$ Rate $\|Q_hu-u_h\|$ Rate 6 0.120E-02 2.01 0.141E-01 2.00 1 7 0.300E-03 2.00 0.354E-02 2.00 8 0.749E-04 2.00 0.885E-03 2.00 6 0.5734E-03 2.00 0.1482E-05 3.00 2 7 0.1434E-03 2.00 0.1852E-06 3.00 8 0.3584E-04 2.00 0.2314E-07 3.00 5 0.3645E-04 3.00 0.1360E-06 3.99 3 6 0.4559E-05 3.00 0.8517E-08 4.00 7 0.5699E-06 3.00 0.5326E-09 4.00 5 0.4222E-06 4.00 0.9119E-09 5.01 4 6 0.2639E-07 4.00 0.2846E-10 5.00 7 0.1650E-08 4.00 0.1110E-11 4.68
Example 3. The $P_k-P_{k-1}-[P_{k+1}]^2$ element, on rectangular grids shown in Figure 5.3
 $k$ ${{\mathcal T}}_l$ ${{|||}} Q_hu-u_h{{|||}}$ Rate $\|Q_hu-u_h\|$ Rate 6 0.141E-01 2.00 0.120E-02 2.01 1 7 0.354E-02 2.00 0.300E-03 2.00 8 0.885E-03 2.00 0.749E-04 2.00 6 0.158E-03 3.00 0.113E-05 4.00 2 7 0.197E-04 3.00 0.709E-07 4.00 8 0.246E-05 3.00 0.444E-08 4.00 4 0.251E-03 4.80 0.409E-05 5.28 3 5 0.143E-04 4.13 0.128E-06 4.99 6 0.889E-06 4.01 0.407E-08 4.98
 $k$ ${{\mathcal T}}_l$ ${{|||}} Q_hu-u_h{{|||}}$ Rate $\|Q_hu-u_h\|$ Rate 6 0.141E-01 2.00 0.120E-02 2.01 1 7 0.354E-02 2.00 0.300E-03 2.00 8 0.885E-03 2.00 0.749E-04 2.00 6 0.158E-03 3.00 0.113E-05 4.00 2 7 0.197E-04 3.00 0.709E-07 4.00 8 0.246E-05 3.00 0.444E-08 4.00 4 0.251E-03 4.80 0.409E-05 5.28 3 5 0.143E-04 4.13 0.128E-06 4.99 6 0.889E-06 4.01 0.407E-08 4.98
Example 4. The $P_k-P_{k-1}-[P_{k+2}]^2$ element, on polygonal grids shown in Figure 5.4
 $k$ ${{\mathcal T}}_l$ ${{|\hspace{-.02in}|\hspace{-.02in}|}} Q_hu-u_h{{|\hspace{-.02in}|\hspace{-.02in}|}}$ Rate $\|Q_hu-u_h\|$ Rate 6 0.3735E-01 1.00 0.7856E-04 2.00 1 7 0.1868E-01 1.00 0.1966E-04 2.00 8 0.9339E-02 1.00 0.4916E-05 2.00 5 0.1504E-02 1.98 0.3242E-05 2.95 2 6 0.3782E-03 1.99 0.4131E-06 2.97 7 0.9482E-04 2.00 0.5216E-07 2.99 4 0.1267E-03 2.97 0.4106E-06 3.95 3 5 0.1600E-04 2.99 0.2636E-07 3.96 6 0.2010E-05 2.99 0.1673E-08 3.98 2 0.5517E-03 3.98 0.5905E-05 5.26 4 3 0.3518E-04 3.97 0.1699E-06 5.12 4 0.2234E-05 3.98 0.5253E-08 5.02
 $k$ ${{\mathcal T}}_l$ ${{|\hspace{-.02in}|\hspace{-.02in}|}} Q_hu-u_h{{|\hspace{-.02in}|\hspace{-.02in}|}}$ Rate $\|Q_hu-u_h\|$ Rate 6 0.3735E-01 1.00 0.7856E-04 2.00 1 7 0.1868E-01 1.00 0.1966E-04 2.00 8 0.9339E-02 1.00 0.4916E-05 2.00 5 0.1504E-02 1.98 0.3242E-05 2.95 2 6 0.3782E-03 1.99 0.4131E-06 2.97 7 0.9482E-04 2.00 0.5216E-07 2.99 4 0.1267E-03 2.97 0.4106E-06 3.95 3 5 0.1600E-04 2.99 0.2636E-07 3.96 6 0.2010E-05 2.99 0.1673E-08 3.98 2 0.5517E-03 3.98 0.5905E-05 5.26 4 3 0.3518E-04 3.97 0.1699E-06 5.12 4 0.2234E-05 3.98 0.5253E-08 5.02
 [1] Kaifang Liu, Lunji Song, Shan Zhao. A new over-penalized weak galerkin method. Part Ⅰ: Second-order elliptic problems. Discrete & Continuous Dynamical Systems - B, 2021, 26 (5) : 2411-2428. doi: 10.3934/dcdsb.2020184 [2] Lunji Song, Wenya Qi, Kaifang Liu, Qingxian Gu. A new over-penalized weak galerkin finite element method. Part Ⅱ: Elliptic interface problems. Discrete & Continuous Dynamical Systems - B, 2021, 26 (5) : 2581-2598. doi: 10.3934/dcdsb.2020196 [3] Hong Seng Sim, Wah June Leong, Chuei Yee Chen, Siti Nur Iqmal Ibrahim. Multi-step spectral gradient methods with modified weak secant relation for large scale unconstrained optimization. Numerical Algebra, Control & Optimization, 2018, 8 (3) : 377-387. doi: 10.3934/naco.2018024 [4] Qian Liu. The lower bounds on the second-order nonlinearity of three classes of Boolean functions. Advances in Mathematics of Communications, 2021  doi: 10.3934/amc.2020136 [5] A. Aghajani, S. F. Mottaghi. Regularity of extremal solutions of semilinaer fourth-order elliptic problems with general nonlinearities. Communications on Pure & Applied Analysis, 2018, 17 (3) : 887-898. doi: 10.3934/cpaa.2018044 [6] Anton Schiela, Julian Ortiz. Second order directional shape derivatives of integrals on submanifolds. Mathematical Control & Related Fields, 2021  doi: 10.3934/mcrf.2021017 [7] Murat Uzunca, Ayşe Sarıaydın-Filibelioǧlu. Adaptive discontinuous galerkin finite elements for advective Allen-Cahn equation. Numerical Algebra, Control & Optimization, 2021, 11 (2) : 269-281. doi: 10.3934/naco.2020025 [8] Prasanta Kumar Barik, Ankik Kumar Giri, Rajesh Kumar. Mass-conserving weak solutions to the coagulation and collisional breakage equation with singular rates. Kinetic & Related Models, , () : -. doi: 10.3934/krm.2021009 [9] Marita Holtmannspötter, Arnd Rösch, Boris Vexler. A priori error estimates for the space-time finite element discretization of an optimal control problem governed by a coupled linear PDE-ODE system. Mathematical Control & Related Fields, 2021  doi: 10.3934/mcrf.2021014 [10] Xiaoming Wang. Quasi-periodic solutions for a class of second order differential equations with a nonlinear damping term. Discrete & Continuous Dynamical Systems - S, 2017, 10 (3) : 543-556. doi: 10.3934/dcdss.2017027 [11] Elvise Berchio, Filippo Gazzola, Dario Pierotti. Nodal solutions to critical growth elliptic problems under Steklov boundary conditions. Communications on Pure & Applied Analysis, 2009, 8 (2) : 533-557. doi: 10.3934/cpaa.2009.8.533 [12] Huy Dinh, Harbir Antil, Yanlai Chen, Elena Cherkaev, Akil Narayan. Model reduction for fractional elliptic problems using Kato's formula. Mathematical Control & Related Fields, 2021  doi: 10.3934/mcrf.2021004 [13] Sandrine Anthoine, Jean-François Aujol, Yannick Boursier, Clothilde Mélot. Some proximal methods for Poisson intensity CBCT and PET. Inverse Problems & Imaging, 2012, 6 (4) : 565-598. doi: 10.3934/ipi.2012.6.565 [14] Jian Yang, Bendong Lou. Traveling wave solutions of competitive models with free boundaries. Discrete & Continuous Dynamical Systems - B, 2014, 19 (3) : 817-826. doi: 10.3934/dcdsb.2014.19.817 [15] Tuan Hiep Pham, Jérôme Laverne, Jean-Jacques Marigo. Stress gradient effects on the nucleation and propagation of cohesive cracks. Discrete & Continuous Dynamical Systems - S, 2016, 9 (2) : 557-584. doi: 10.3934/dcdss.2016012 [16] Matthias Erbar, Jan Maas. Gradient flow structures for discrete porous medium equations. Discrete & Continuous Dynamical Systems - A, 2014, 34 (4) : 1355-1374. doi: 10.3934/dcds.2014.34.1355 [17] Arseny Egorov. Morse coding for a Fuchsian group of finite covolume. Journal of Modern Dynamics, 2009, 3 (4) : 637-646. doi: 10.3934/jmd.2009.3.637 [18] Mingxin Wang, Qianying Zhang. Dynamics for the diffusive Leslie-Gower model with double free boundaries. Discrete & Continuous Dynamical Systems - A, 2018, 38 (5) : 2591-2607. doi: 10.3934/dcds.2018109 [19] Yizhuo Wang, Shangjiang Guo. A SIS reaction-diffusion model with a free boundary condition and nonhomogeneous coefficients. Discrete & Continuous Dynamical Systems - B, 2019, 24 (4) : 1627-1652. doi: 10.3934/dcdsb.2018223 [20] Caifang Wang, Tie Zhou. The order of convergence for Landweber Scheme with $\alpha,\beta$-rule. Inverse Problems & Imaging, 2012, 6 (1) : 133-146. doi: 10.3934/ipi.2012.6.133

2019 Impact Factor: 1.27

## Tools

Article outline

Figures and Tables