Characterization of anisotropic turbulence behavior in pulsatile blood flow
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ORIGINAL PAPER
Characterization of anisotropic turbulence behavior in pulsatile blood flow Magnus Andersson1 · Matts Karlsson1 Received: 9 May 2020 / Accepted: 7 October 2020 © The Author(s) 2020
Abstract Turbulent-like hemodynamics with prominent cycle-to-cycle flow variations have received increased attention as a potential stimulus for cardiovascular diseases. These turbulent conditions are typically evaluated in a statistical sense from single scalars extracted from ensemble-averaged tensors (such as the Reynolds stress tensor), limiting the amount of information that can be used for physical interpretations and quality assessments of numerical models. In this study, barycentric anisotropy invariant mapping was used to demonstrate an efficient and comprehensive approach to characterize turbulence-related tensor fields in patient-specific cardiovascular flows, obtained from scale-resolving large eddy simulations. These techniques were also used to analyze some common modeling compromises as well as MRI turbulence measurements through an idealized constriction. The proposed method found explicit sites of elevated turbulence anisotropy, including a broad but time-varying spectrum of characteristics over the flow deceleration phase, which was different for both the steady inflow and Reynolds-averaged Navier–Stokes modeling assumptions. Qualitatively, the MRI results showed overall expected poststenotic turbulence characteristics, however, also with apparent regions of unrealizable or conceivably physically unrealistic conditions, including the highest turbulence intensity ranges. These findings suggest that more detailed studies of MRImeasured turbulence fields are needed, which hopefully can be assisted by more comprehensive evaluation tools such as the once described herein. Keywords Barycentric anisotropy invariant map · Patient-specific scale-resolved computational hemodynamics · Reynolds stress and dissipation tensor · MRI turbulence measurements · Verification and validation
1 Introduction Turbulence exhibits a wide range of cascading eddies, from the largest energy-containing macro-structures (integral length scale ∼ geometry) down to the smallest microscale whorls (Kolmogorov scales ∼ few tens of microns in blood flow) (Antiga and Steinman 2009), where the energy is dissipated into heat. The local ensemble of these eddies will reflect on the level of velocity fluctuations and turbulencerelated momentum transport in different directions, which is highly affected by the gradients of the main flow. From a time-averaged point of view, these characteristics will favor specific axes of dependence and independence where the
* Magnus Andersson [email protected] 1
Department of Management and Engineering, Linköping University, SE‑581 83 Linköping, Sweden
turbulence activity is strong or weak, respectively (Banerjee et al. 2007). Turbulent-like hemodynamics have received increased attention in recent years as a phenotypic marker, suggested by the growing number of publications on the topic, with a
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