Two simple feedback control laws for drag reduction are derived by applying a suboptimal control theory to a turbulent channel flow. These new feedback control laws require pressure or shear-stress information only at the wall, and when applied to a turbulent channel flow at Reτ = 110, they result in 16–22% reduction in the skin-friction drag. More practical control laws requiring only the loca...

This study investigated fluid and structural responses to pulsatile non-Newtonian blood flow through a stenosed artery, using ANSYS. The artery was modeled as an axis-symmetric stenosed vessel. The wall of the vessel was set to be isotropic and elastic. The blood behavior was described by the Power Law and Carreau non-Newtonian models, respectively. When compared to the Newtonian flow models, t...

Compared to the abdominal aorta, the hemodynamic environment in the inferior vena cava (IVC) is not well described. Using cine phase-contrast magnetic resonance imaging (MRI) and a custom MRI-compatible cycle in an open-magnet, we quantified mean blood flow rate, wall shear stress, and cross-sectional lumen area in eleven young, normal subjects at the supraceliac and infrarenal levels of the ao...

Compared with the abdominal aorta, the hemodynamic environment in the inferior vena cava (IVC) is not well described. With the use of cine phase-contrast magnetic resonance imaging (MRI) and a custom MRI-compatible cycle in an open magnet, we quantified mean blood flow rate, wall shear stress, and cross-sectional lumen area in 11 young normal subjects at the supraceliac and infrarenal levels of...

Objective The objective was to study the performance of an in-house developed wall shear stress (WSS) algorithm using PC-MRI in intracranial aneurysms. Materials & Methods First, the algorithm was applied to a high resolution in vitro PC-MRI measurement under steady and pulsatile fl ow conditions. A CFD simulation was performed with similar infl ow boundary conditions. Second, WSS was estimated...

The relationships among vascular geometry, hemodynamics, and plaque development in the coronary arteries are complex and not yet well understood. This paper reports a methodology for the quantitative analysis of in vivo coronary morphology and hemodynamics, with particular emphasis placed on the critical issues of image segmentation and the automated classification of disease severity. We were ...

Leukocytes rolling on selectins extrude thin membrane tethers that might stabilize rolling velocities despite marked alterations in wall shear stress. To test this hypothesis, we used differential interference contrast videomicroscopy to visualize formation and breakage of membrane tethers as neutrophils rolled on P-selectin under flow. Neutrophils rapidly increased tether number as wall shear ...

BACKGROUND/AIM Practical difficulties, particularly long model development time, have limited the types and applicability of computational fluid dynamics simulations in numerical modeling of blood flow in serial manner. In these simulations, the most revealing flow parameters are the endothelial shear stress distribution and oscillatory shear index. The aim of this study was analyze their role ...

We used 4D flow magnetic resonance imaging1 to evaluate a 34-year-old man with a complicated course after aortic coarctation repair including development of an aortopulmonary fistula. Our initial 4D flow study (Figure 1) reveals abnormal vortical-type flow in the aneurysmal distal aortic arch. Evaluation of wall shear stress calculated from near-wall velocity gradients using proprietary softwar...

The effects of changes in flow velocity waveform and arterial geometry before and after percutaneous coronary intervention (PCI) in the right coronary artery (RCA) were investigated using computational fluid dynamics. An RCA from a patient with a stenosis was reconstructed based on multislice computerized tomography images. A nonstenosed model, simulating the same RCA after PCI, was also constr...