本文在各向异性网格下讨论了一般二阶椭圆方程的EQ1rot非协调有限元逼近.利用Taylor展开,积分恒等式和平均值技巧导出了一些关于该元新的高精度估计.再结合该元所具有的二个特殊性质:(a)当精确解属于H^2(Ω)时,其相容误差为O(h^2)阶比它的插值误差高一阶;(b)插值算子与Ritz投影算子等价,得到了在能量模意义下O(h^2)阶的超逼近性质.进而,借助于插值后处理技术给出了整体超收敛的一般估计式.
In this paper, the EQ1rot nonconforming finite element approximation to the general second order elliptic equations is discussed on anisotropic meshes. Some new high accuacy estimates of this element axe derived by virtue of Taylor's expansion, the integral identities and mean-value techniques. The supclose result with order O(h2) in the broken energy norm is deduced by use of two special properties of this element: (a) the consistency error is of order O(h^2) one order higher than its interpolation error O(h), when the exact solution belongs to H3 (Ω); (b) the interpolation operator is equivalent to its Ritz-prejection operator. Morever, The general estimate of global superconvergence is gained through interpolation postprocessing approach.