Institute of Turbomachinery, Faculty of Mechanical Engineering and Marine Technology, University of Rostock, Rostock, Germany.
Institute of Fluid Mechanics, Faculty of Mechanical Engineering and Marine Technology, University of Rostock, Rostock, Germany.
Cardiovasc Eng Technol. 2021 Jun;12(3):251-272. doi: 10.1007/s13239-021-00526-x. Epub 2021 Mar 5.
Cardiovascular engineering includes flows with fluid-dynamical stresses as a parameter of interest. Mechanical stresses are high-risk factors for blood damage and can be assessed by computational fluid dynamics. By now, it is not described how to calculate an adequate scalar stress out of turbulent flow regimes when the whole share of turbulence is not resolved by the simulation method and how this impacts the stress calculation.
We conducted direct numerical simulations (DNS) of test cases (a turbulent channel flow and the FDA nozzle) in order to access all scales of flow movement. After validation of both DNS with literature und experimental data using magnetic resonance imaging, the mechanical stress is calculated as a baseline. Afterwards, same flows are calculated using state-of-the-art turbulence models. The stresses are computed for every result using our definition of an equivalent scalar stress, which includes the influence from respective turbulence model, by using the parameter dissipation. Afterwards, the results are compared with the baseline data.
The results show a good agreement regarding the computed stress. Even when no turbulence is resolved by the simulation method, the results agree well with DNS data. When the influence of non-resolved motion is neglected in the stress calculation, it is underpredicted in all cases.
With the used scalar stress formulation, it is possible to include information about the turbulence of the flow into the mechanical stress calculation even when the used simulation method does not resolve any turbulence.
心血管工程包括以流体力为参数的流动。机械应力是血液损伤的高风险因素，可以通过计算流体动力学进行评估。到目前为止，还没有描述如何在模拟方法不能解析整个湍流份额的情况下，从湍流流动中计算出适当的标量应力，以及这对应力计算有何影响。
我们进行了测试案例（湍流通道流和 FDA 喷嘴）的直接数值模拟（DNS），以获取所有尺度的流动运动。在使用磁共振成像对 DNS 与文献和实验数据进行验证后，将机械应力作为基线进行计算。然后，使用最新的湍流模型计算相同的流动。使用我们定义的等效标量应力对每个结果进行计算，该定义包括来自各自湍流模型的影响，通过使用参数耗散。然后，将结果与基线数据进行比较。
计算出的应力结果具有很好的一致性。即使模拟方法不能解析任何湍流，结果也与 DNS 数据吻合良好。当在应力计算中忽略未解析运动的影响时，在所有情况下都会被低估。
使用所提出的标量应力公式，即使使用的模拟方法不能解析任何湍流，也可以将流动的湍流信息纳入机械应力计算中。
