Pathological platelet activation by abnormal shear stresses is regarded as a main clinical complication in recipients of cardiovascular mechanical devices. In order to improve their performance computational fluid dynamics (CFD) are used to evaluate flow fields and related shear stresses. CFD models are coupled with mathematical models that describe the relation between fluid dynamics variables, and in particular shear stresses, and the platelet activation state (PAS). These models typically use a Lagrangian approach to compute the shear stresses along possible platelet trajectories. However, in the case of turbulent flow, the choice of the proper turbulence closure is still debated for both concerning its effect on shear stress calculation and Lagrangian statistics. In this study different numerical simulations of the flow through a mechanical heart valve were performed and then compared in terms of Eulerian and Lagrangian quantities: a direct numerical simulation (DNS), a large eddy simulation (LES), two Reynolds-averaged Navier-Stokes (RANS) simulations (SST k-ω and RSM) and a “laminar” (no turbulence modelling) simulation. Results exhibit a large variability in the PAS assessment depending on the turbulence model adopted. “Laminar” and RSM estimates of platelet activation are about 60% below DNS, while LES is 16% less. Surprisingly, PAS estimated from the SST k- ω velocity field is only 8% less than from DNS data. This appears more artificial than physical as can be inferred after comparing frequency distributions of PAS and of the different Lagrangian variables of the mechano-biological model of platelet activation. Our study indicates how much turbulence closures may affect platelet activation estimates, in comparison to an accurate DNS, when assessing blood damage in blood contacting devices.

异常剪切应力引起的病理性血小板激活被认为是心血管机械装置接受者的主要临床并发症。为了提高它们的性能，计算流体动力学 (CFD) 被用来评估流场和相关的剪切应力。CFD 模型与描述流体动力学变量（尤其是剪切应力）和血小板活化状态 (PAS) 之间关系的数学模型相结合。这些模型通常使用拉格朗日方法来计算沿可能的血小板轨迹的剪切应力。然而，在湍流的情况下，选择合适的湍流闭合仍然存在争议，因为它对剪应力计算和拉格朗日统计的影响。k -ω 和 RSM）和“层流”（无湍流建模）模拟。根据采用的湍流模型，结果在 PAS 评估中表现出很大的可变性。血小板活化的“层流”和 RSM 估计值比 DNS 低约 60%，而 LES 低 16%。令人惊讶的是，根据 SST k - ω 速度场估计的 PAS仅比 DNS 数据少 8%。在比较 PAS 的频率分布和血小板活化的机械生物学模型的不同拉格朗日变量的频率分布后可以推断，这似乎比物理更人为。我们的研究表明，在评估血液接触装置中的血液损伤时，与准确的 DNS 相比，湍流闭合可能影响血小板活化估计的程度有多大。