In this short note, we discuss the circumstances that can lead to a failure to observe the design order of discretization error convergence in accuracy verification when solving a time-dependent problem. In particular, we discuss the problem of failing to observe the design order of spatial accuracy with an extremely small time step. The same problem is encountered even if the time step is reduced with grid refinement. These can cause a serious problem because then one would wind up trying to find a coding error that does not exist. This short note clarifies the mechanism causing this failure and provides a guide for avoiding such pitfalls

翻译：在这篇短文中，我们讨论了在求解时间依赖问题时可能导致离散化误差收敛的设计阶数无法被观测到的情形。特别地，我们探讨了使用极小时间步长时无法观测到空间精度设计阶数的问题。即使随着网格细化而减小时间步长，同样的问题依然会出现。这可能导致严重问题，因为研究人员会因此去查找本不存在的编码错误。本文阐明了导致此问题的机制，并提供了避免此类陷阱的指南。