FDA喷管基准和格子玻尔兹曼方法分析过渡区生物医学流动的有效性
Efficacy of the FDA nozzle benchmark and the lattice Boltzmann method for the analysis of biomedical flows in transitional regime
摘要：
尽管处于中等雷诺数，但通过医疗器械以及解剖血管中的流动可能表现出过渡甚至湍流特性。为了验证用于生物医学流动计算的数值方法和代码，美国食品和药物管理局（FDA）建立了一个实验基准，该基准是代表喷嘴的逐渐收缩和突然膨胀的管道。公开发布了雷诺数从500到6500的各种实验结果。以前和最近对FDA喷嘴中的流动进行的计算研究发现，各种CFD方法存在局限性，有些甚至质疑基准本身的适当性。该通信报告了基于格子玻尔兹曼方法（LBM）的直接数值模拟（DNS）方法的结果，该方法适用于雷诺数为2000和3500的过渡情况下的FDA喷嘴基准。我们的目标是评估如果一个简单的现成的LBM将预测实验结果，而不使用复杂的模型或合成湍流的流入。执行具有各种空间和时间分辨率的LBM计算-在4400万到28亿个晶格单元的末端-分别在台式机的32个CPU核心到现代超级计算机的超过30万个核心上进行，以探索和表征微小的流动细节并量化柯尔莫哥洛夫尺度。LBM模拟在雷诺数2000时过渡到湍流，与FDA的实验相似，并且对于两个雷诺数，发现射流破裂位置、平均速度、剪切应力和压力的一致性可接受。
英文摘要：
Flows through medical devices as well as in anatomical vessels despite being at moderate Reynolds number may exhibit transitional or even turbulent character. In order to validate numerical methods and codes used for biomedical flow computations, the U.S. food and drug administration (FDA) established an experimental benchmark, which was a pipe with gradual contraction and sudden expansion representing a nozzle. The experimental results for various Reynolds numbers ranging from 500 to 6500 were publicly released. Previous and recent computational investigations of flow in the FDA nozzle found limitations in various CFD approaches and some even questioned the adequacy of the benchmark itself. This communication reports the results of a lattice Boltzmann method (LBM) based direct numerical simulation (DNS) approach applied to the FDA nozzle benchmark for transitional cases of Reynolds numbers 2000 and 3500. The goal is to evaluate if a simple off the shelf LBM would predict the experimental results without the use of complex models or synthetic turbulence at the inflow. LBM computations with various spatial and temporal resolutions are performed - in the extremities of 44 million to 2.8 billion lattice cells - conducted respectively on 32 CPU cores of a desktop to more than 300'000 cores of a modern supercomputer to explore and characterize miniscule flow details and quantify Kolmogorov scales. The LBM simulations transition to turbulence at a Reynolds number 2000 like the FDA's experiments and acceptable agreement in jet breakdown locations, average velocity, shear stress and pressure is found for both the Reynolds numbers.
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