Geometrically-Induced Errors in the Finite Difference Method for Solving Heat Conduction Equations
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摘要: 首先举例说明,基于离散等价方程提出了非结构网格有限差分法(UFDM),提高了有限差分法几何适应性. 在有限差分法求解曲线坐标系下热传导方程时,坐标变换导致出现几何诱导误差. 这一现象通过采用中心格式求解温度场方程给出说明. 根据差分格式截断误差的精度定义,理论上论证了几何诱导误差导致降阶的必然性. 其次提出了验证一阶精度的保线性考核模型,据此得出了差分格式在非均匀网格难以保证考核模型一阶精度的结论. 在此基础上,提出了基于梯度重构的保线性算法. 数值计算表明,对任意形状结构网格计算线性分布温度场,均可得到误差为机器精度0量级的数值解,为开发全自动温度场计算软件提供了理论与实践基础.Abstract: Firstly, as an example, the unstructured finite difference method (UFDM) based on discrete equivalent equations was proposed, to enhance the geometric adaptability of the finite difference method. During the solution of the heat conduction equations with the finite difference method in the curvilinear coordinate system, the coordinate transformation will lead to geometric-induced errors. This phenomenon was illustrated by means of the central difference scheme to solve the temperature field equation. Based on the precision definition of the truncation errors of the difference scheme, the geometry-induced error was theoretically demonstrated to inevitably leads to a reduction in order. Secondly, a linear preservation assessment model was built to verify the 1st-order accuracy, and the difference scheme was proved to be difficult to guarantee the 1st-order accuracy of the assessment model on non-uniform grids. On this basis, a linear preservation algorithm based on gradient reconstruction was proposed. Numerical calculations show that, for structured grids with any shape to calculate linearly distributed temperature fields, numerical solutions with errors at the machine precision level of 0 can be obtained. This study provides a theoretical and practical foundation for developing fully automatic temperature field calculation software.
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表 1 网格加密引起的误差
Table 1. Errors caused by the grid refinement
Δx ε(L2) ε(L∞) 0.05 6.29E-7 2.60E-5 0.025 8.26E-8 6.53E-6 0.012 5 1.06E-8 1.63E-6 0.006 25 1.34E-9 4.09E-7 -
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