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The effect of turbulence on transitional flow in the FDA's benchmark nozzle model using large-eddy simulation.
International Journal for Numerical Methods in Biomedical Engineering ( IF 2.2 ) Pub Date : 2020-08-01 , DOI: 10.1002/cnm.3389 Emily L Manchester 1 , Xiao Yun Xu 1
International Journal for Numerical Methods in Biomedical Engineering ( IF 2.2 ) Pub Date : 2020-08-01 , DOI: 10.1002/cnm.3389 Emily L Manchester 1 , Xiao Yun Xu 1
Affiliation
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The Food and Drug Administration's (FDA) benchmark nozzle model has been studied extensively both experimentally and computationally. Although considerable efforts have been made on validations of a variety of numerical models against available experimental data, the transitional flow cases are still not fully resolved, especially with regards to detailed comparison of predicted turbulence quantities with experimental measurements. This study aims to fill this gap by conducting large‐eddy simulations (LES) of flow through the FDA's benchmark model, at a transitional Reynolds number of 2000. Numerical results are compared to previous interlaboratory experimental results, with an emphasis on turbulence characteristics. Our results show that the LES methodology can accurately capture laminar quantities throughout the model. In the pre‐jet breakdown region, predicted turbulence quantities are generally larger than high resolution experimental data acquired with laser Doppler velocimetry. In the jet breakdown regions, where maximum Reynolds stresses occur, Reynolds shear stresses show excellent agreement. Differences of up to 4% and 20% are observed near the jet core in the axial and radial normal Reynolds stresses, respectively. Comparisons between viscous and Reynolds shear stresses show that peak viscous shear stresses occur in the nozzle throat reaching a value of 18 Pa in the boundary layer, whilst peak Reynolds shear stresses occur in the jet breakdown region reaching a maximum value of 87 Pa. Our results highlight the importance in considering both laminar and turbulent contributions towards shear stresses and that neglecting the turbulence effect can significantly underestimate the total shear force exerted on the fluid.
中文翻译：
湍流对 FDA 基准喷嘴模型中过渡流的影响，使用大涡模拟。
食品和药物管理局 (FDA) 的基准喷嘴模型已通过实验和计算进行了广泛的研究。尽管已经针对可用实验数据验证各种数值模型做出了相当大的努力，但过渡流情况仍未完全解决，尤其是在预测湍流量与实验测量值的详细比较方面。本研究旨在通过对 FDA 基准模型的流动进行大涡模拟 (LES) 来填补这一空白，过渡雷诺数为 2000。将数值结果与之前的实验室间实验结果进行比较，重点是湍流特性。我们的结果表明，LES 方法可以准确地捕获整个模型中的层流量。在预射流击穿区域，预测的湍流量通常大于使用激光多普勒测速仪获得的高分辨率实验数据。在出现最大雷诺应力的射流击穿区域，雷诺剪切应力表现出极好的一致性。在轴向和径向法向雷诺应力中，喷射核心附近分别观察到高达 4% 和 20% 的差异。粘性剪切应力和雷诺剪切应力之间的比较表明，峰值粘性剪切应力出现在喷嘴喉部，边界层中达到 18 Pa 的值，而峰值雷诺剪切应力出现在射流击穿区域，达到最大值 87 Pa。
更新日期：2020-10-04
中文翻译：
湍流对 FDA 基准喷嘴模型中过渡流的影响，使用大涡模拟。
食品和药物管理局 (FDA) 的基准喷嘴模型已通过实验和计算进行了广泛的研究。尽管已经针对可用实验数据验证各种数值模型做出了相当大的努力，但过渡流情况仍未完全解决，尤其是在预测湍流量与实验测量值的详细比较方面。本研究旨在通过对 FDA 基准模型的流动进行大涡模拟 (LES) 来填补这一空白，过渡雷诺数为 2000。将数值结果与之前的实验室间实验结果进行比较，重点是湍流特性。我们的结果表明，LES 方法可以准确地捕获整个模型中的层流量。在预射流击穿区域，预测的湍流量通常大于使用激光多普勒测速仪获得的高分辨率实验数据。在出现最大雷诺应力的射流击穿区域，雷诺剪切应力表现出极好的一致性。在轴向和径向法向雷诺应力中，喷射核心附近分别观察到高达 4% 和 20% 的差异。粘性剪切应力和雷诺剪切应力之间的比较表明，峰值粘性剪切应力出现在喷嘴喉部，边界层中达到 18 Pa 的值，而峰值雷诺剪切应力出现在射流击穿区域，达到最大值 87 Pa。
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