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首页> 外文期刊>Communications in Numerical Methods in Engineering >The FDAnozzle benchmark: 'In theory there is no difference between theory and practice, but in practice there is'
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The FDAnozzle benchmark: 'In theory there is no difference between theory and practice, but in practice there is'

机译：FDANOZZLZLZLUZZLZLE基准：“理论上的理论与实践之间没有区别，但实际上有”

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The utility of flow simulations relies on the robustness of computational fluid dynamics (CFD) solvers and reproducibility of results. The aim of this study was to validate the Oasis CFD solver against in vitro experimental measurements of jet breakdown location from the FDA nozzle benchmark at Reynolds number 3500, which is in the particularly challenging transitional regime. Simulations were performed on meshes consisting of 5, 10, 17, and 28 million (M) tetrahedra, with Delta t = 10(-5) seconds. The 5M and 10M simulation jets broke down in reasonable agreement with the experiments. However, the 17M and 28M simulation jets broke down further downstream. But which of our simulations are "correct"? From a theoretical point of view, they are all wrong because the jet should not break down in the absence of disturbances. The geometry is axisymmetric with no geometrical features that can generate angular velocities. A stable flow was supported by linear stability analysis. From a physical point of view, a finite amount of "noise" will always be present in experiments, which lowers transition point. To replicate noise numerically, we prescribed minor random angular velocities (approximately 0.31%), much smaller than the reported flow asymmetry (approximately 3%) and model accuracy (approximately 1%), at the inlet of the 17M simulation, which shifted the jet breakdown location closer to the measurements. Hence, the high-resolution simulations and "noise" experiment can potentially explain discrepancies in transition between sometimes "sterile" CFD and inherently noisy "ground truth" experiments. Thus, we have shown that numerical simulations can agree with experiments, but for the wrong reasons.
机译：流动模拟的效用依赖于计算流体动力学（CFD）溶剂的鲁棒性和结果的再现性。本研究的目的是将OASIS CFD解决方案验证在雷诺数3500的FDA喷嘴基准下的FDA喷嘴基准测试中的射流击穿位置的体外实验测量。在特别具有挑战性的过渡方案中。对由5,10,17和2800万（m）四段组成的网状物进行仿真，ΔTδt= 10（-5）秒。 5M和10M模拟喷气机与实验合理一致地崩溃。但是，17M和28M模拟喷气机进一步下游崩溃。但我们的哪种模拟是“正确”？从理论的角度来看，他们都错了，因为喷气机不应该在没有干扰的情况下分解。几何形状是轴对称，没有几何特征可以产生角速度。线性稳定性分析支持稳定的流动。从物理的角度来看，在实验中将始终存在有限量的“噪声”，从而降低过渡点。为了数控复制噪声，我们规定了一个小的随机角速度（约0.31％），远小于报告的流量不对称（约3％）和模型精度（约1％），在17M模拟的入口处转移喷射器击穿位置更靠近测量。因此，高分辨率模拟和“噪声”实验可以潜在地解释有时“无菌”CFD之间过渡的差异，并且本身嘈杂的“实际真理”实验。因此，我们已经表明，数值模拟可以同意实验，但原因是错误的。

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