A Class of Explicit and Monotonic Finite Difference Methods for 2D Fisher-KPP Equations
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摘要: 运用一类加权的差分公式和显式Euler法离散扩散项及一阶时间导数项, 从而对二维Fisher-Kolmogorov-Petrovsky-Piscounov(Fisher-KPP)方程构造一组两层、显式、单调的差分格式.经分析, 证明了当网格步长和参数α,p,θ满足一定约束条件时, 该格式能够保持原问题解的保正性、有界性和单调性等数学性质, 并且获得了数值解在无穷范数下的误差估计.数值实验验证了数值结果与理论结果相吻合.
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关键词:
- Fisher-KPP方程 /
- 保正性 /
- 有界性 /
- 单调性 /
- 有限差分法
Abstract: With a class of weighted difference formulas and explicit Euler methods to discretize diffusion terms and the 1st-order temporal derivative, respectively, a new type of 2-level, explicit and monotonic finite difference methods is established for 2D Fisher-KPP equations. As α, p, θ and the grid step size satisfy some constraining conditions, their numerical solutions can inherit the properties of the exact solutions, such as positivity preservation, boundedness and monotonicity. Furthermore, the maximum norm error estimate is obtained, rigorously. Numerical experiments illustrate that the numerical results agree well with the theoretical findings.-
Key words:
- Fisher-KPP equation /
- positivity preservation /
- boundedness /
- monotonicity /
- finite difference method
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表 1 当p=8, 16, 32时差分格式(8a)—(8d)的数值结果
Table 1. The numerical results of difference schemes (8a)—(8d) with p=8, 16, 32
hx=hy τ p=8 p=16 p=32 E∞(hx, hy, τ) Oorder E∞(hx, hy, τ) Oorder E∞(hx, hy, τ) Oorder TCPU/s θ=0, τ=hx2/8 1/2 1/32 2.251 3E-3 - 3.866 5E-3 - 5.148 3E-3 - 0.014 4 1/4 1/128 5.794 7E-4 1.958 0 9.177 2E-4 2.074 9 1.185 5E-3 2.118 6 0.018 9 1/8 1/512 1.442 2E-4 2.006 5 2.293 9E-4 2.000 3 2.890 6E-4 2.036 1 0.087 2 1/16 1/2 048 3.601 6E-5 2.001 5 5.719 4E-5 2.003 9 7.186 1E-4 2.008 1 1.164 5 θ=0.5, τ=hx4/4 1/2 1/64 1.371 1E-2 - 1.155 7E-2 - 9.215 1E-3 - 0.014 9 1/4 1/1 024 3.923 3E-3 1.805 2 3.114 3E-3 1.891 8 2.530 6E-3 1.864 5 0.054 4 1/8 1/16 384 1.000 2E-3 1.971 9 8.046 0E-4 1.952 6 6.534 2E-4 1.953 4 2.004 0 1/16 1/262 144 2.513 2E-4 1.992 6 2.035 0E-4 1.983 2 1.648 7E-4 1.986 7 161.700 θ=1, τ=hx4/4 1/2 1/64 2.648 6E-2 - 2.237 0E-2 - 1.778 9E-2 - 0.013 4 1/4 1/1 024 7.800 8E-3 1.763 5 6.153 0E-3 1.862 2 4.961 8E-3 1.842 0 0.063 7 1/8 1/16 384 1.998 7E-3 1.964 5 1.608 5E-3 1.935 5 1.284 0E-3 1.950 2 2.026 1 1/16 1/262 144 5.028 7E-4 1.990 8 4.054 0E-4 1.988 3 3.239 5E-4 1.986 8 121.119 -
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