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Uncertainty is defined as a potential deficiency in any activity or phase of the modelling process that is due to the lack of knowledge.〔AIAA, "Guide for the Verification and Validation of Computational Fluid Dynamics Simulations," AIAA G-077-1998, 1998〕 Error is defined as a recognizable deficiency in any phase or activity of modelling and simulation that is not due to lack of knowledge. It is important to differentiate error and uncertainty, therefore these definitions entails that uncertainty is stochastic or non-deterministic whereas error is deterministic. In elementary terms, if a simulation is run twice while containing an error then it is likely to develop same answer (exceptions can be seen). But, when a simulation is run twice containing an uncertainty than it will develop different answer each time, taking an assumption that the uncertainty is not replaced by mean value and is modeled as an uncertain quantity. Errors are subjected to be identified and corrected if it is provided with enough time and money. ==Classification of errors== Errors are classified in two categories: Acknowledge error and unacknowledged error. # Acknowledged errors are those errors which can be determined before the simulation by the analyst. There errors occur due to complexity of the problem and cost constraint, therefore they cannot be solved for that particular job.".〔Uncertainty Analysis of Computational Fluid Dynamics Via Polynomial Chaos, Rafael A. Perez, Virginia Polytechnic Institute and State University〕 # These are various types of acknowledged errors: ## Physical approximation and Geometry error ## Computer round-off error ## Iterative convergence error ## Spatial and Temporal Discretization error 2. Unacknowledged error are error which are incognizant by the analyst but can be spotted. If we apply rigorous methods for identifying the errors such as double examination than such errors can be discovered. Mistakes and blunders also come under this type of error. But there are two specific types of unacknowledged error: computer programming error and usage error. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Uncertainty and errors in cfd simulation」の詳細全文を読む スポンサード リンク
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