Numerical modeling of pulsatile turbulent flow in stenotic vessels.

School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907, USA.
Journal of Biomechanical Engineering (Impact Factor: 1.52). 09/2003; 125(4):445-60. DOI: 10.1115/1.1589774
Source: PubMed

ABSTRACT Pulsatile turbulent flow in stenotic vessels has been numerically modeled using the Reynolds-averaged Navier-Stokes equation approach. The commercially available computational fluid dynamics code (CFD), FLUENT, has been used for these studies. Two different experiments were modeled involving pulsatile flow through axisymmetric stenoses. Four different turbulence models were employed to study their influence on the results. It was found that the low Reynolds number k-omega turbulence model was in much better agreement with previous experimental measurements than both the low and high Reynolds number versions of the RNG (renormalization-group theory) k-epsilon turbulence model and the standard k-epsilon model, with regard to predicting the mean flow distal to the stenosis including aspects of the vortex shedding process and the turbulent flow field. All models predicted a wall shear stress peak at the throat of the stenosis with minimum values observed distal to the stenosis where flow separation occurred.

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    ABSTRACT: Presented is an investigation into the use of compu-tational fluid dynamics (CFD) for modelling the ef-fects of inertial loading on the human cardiovascular system. An anatomically correct model of the human aortic arch was created based on computed tomogra-phy (CT) imagery and meshed as a three-dimensional unstructured grid with inflated boundary layers. To simulate the highly pulsatile nature of aortic flow, an unsteady, velocity based boundary condition was im-posed at the inlet driving the aortic pressure between 80 and 120 mmHg. Individual resistive boundary con-ditions were applied at all outlets approximating the downstream peripheral vascular resistance. Turbu-lence was simulated using the k − ω model. A base-line simulation was first conducted at standard grav-ity comparing velocity and pressure with experimental data expected for aortic arch flow. Results indicate a peak velocity in the arch of 1.12 m /s which compares well with experimental values ranging between 0.8 and 1.5 m /s [6]. Inertial loads were then applied in the ver-tical (Z) direction along the longitudinal axis in incre-ments of 1 +Gz to a maximum of 8 +Gz. A linear re-duction in mass flow rate of 15% per +Gz was noted at the ascending arterial branches without cardiac com-pensation or G straining maneuvers. The reduced flow through these arteries created a corresponding increase in back flow through the aortic arch. This was am-plified under G load, raising both systolic and dias-tolic arch velocity. Although successful preliminary results were obtained, further model enhancements are required before accurate clinical judgements regarding G tolerance can be made. NOMENCLATURE n unit normal vector v velocity, m /s A area, m 2 a n Fourier curve fit parameter b n Fourier curve fit parameter C a peripheral vascular resistance, kg /m 4 s p pressure, Pa ∆t time step, s t flow time, s Z axis, running through the body head-to-foot δΩ domain boundary µ viscosity coefficient, kg /ms ω Fourier frequency parameter ρ density, g /mL
    18th Annual Conference of the CFD Society of Canada, London, Ontario; 06/2010

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