Evaluating the effect of non-Newtonian turbulent blood models within a double-stenosed artery

This article describes the numerical investigation of blood rheology within an artery that includes two narrowing areas via Computational Fluid Dynamics (CFD). Elliptic blending Reynolds stress model and two models of viscosity have been used in this investigation utilizing STAR-CCM+ 2021.2.1. The test model includes two elliptical stenosis with a 2mm distance between them, and the area of stenosis is 75%. Results of normalized axial velocity, turbulent kinetic energy (TKE) and turbulent viscosity ratio (TVR) were evaluated before, through and after the stenosis in order to predict and avoid the real problems that occur from changing the area of the artery. Furthermore, Fractional flow reserve (FFR) was employed to assess the level of risk of stenosis through the artery, which depends on pressure measurements. Corresponding to the author's observation, it was found that the recirculation regions in the area between the stenosis are larger than the area after the stenosis. Moreover, the results of TKE and TVR are almost identical through and downstream of the stenosis, whereas the TKE is slightly higher with the Carreau model than with the Newtonian flow at the upstream and through the first stenosis.

Evaluating the effect of non-Newtonian fluid turbulent flowing for blood within a double-stenosed artery

This article describes the numerical investigation of blood rheology within an artery that includes two narrowing areas via Computational Fluid Dynamics (CFD) to offer guidance to the community, especially surgeons, and help them to avoid the risk of stenosis. Elliptic blending Reynolds stress model and two models of viscosity have been used in this investigation utilizing STAR-CCM+ 2021.2.1. The test model includes two elliptical stenosis with a 2mm distance between them, and the area of stenosis is 75%. Results of normalized axial velocity, turbulent kinetic energy (TKE) and turbulent viscosity ratio (TVR) were evaluated before, through and after the stenosis in order to predict and avoid the real problems that occur from changing the area of the artery. Furthermore, Fractional flow reserve (FFR) was employed to assess the level of risk of stenosis through the artery, which depends on pressure measurements. Corresponding to the author's observation, it was found that the recirculation regions in the area between the stenosis are larger than the area after the stenosis. Moreover, the results of TKE and TVR are almost identical through and downstream of the stenosis, whereas the TKE is slightly higher with the Carreau model (arrive to 0.54 J/kg) than with the Newtonian flow (arrive to o.47 J/kg) at the upstream and through the first stenosis.

Numerical Analysis on A Non-Critical Stenosis in Renal Artery

The increase in cardiovascular diseases worldwide has resulted in higher death rate of people globally; the primary reason being atherosclerosis. A better understanding of this condition can be achieved through the application of numerical methods to understand the haemodynamics. The present study aims to investigate the effects of renal artery angulation on the flow characteristics in a non-critically stenosed artery compared to that of a normal artery in order to understand better, the reasons for causes and progression of renal artery stenosis. Abdominal aorta-renal artery models ranging from 30° to 90° angulations were generated from computerized tomography-angiogram slices, post which they were subjected to cleanup and defeaturing. Haemodynamic parameters such as velocity, pressure and time-averaged wall shear stress were evaluated at early systole, peak systole and peak diastole for the different artery models. Extensive amounts of flow recirculation were observed in normal renal arteries with higher bifurcating angles, whereas it was not the case in stenosed arteries where flow acceleration was seen for the duration of the cardiac cycle. Evaluation of static pressure encountered a similar trend where an increase in angulation saw a decrease in pressure for normal arteries which contradicted with stenosed artery results. Analysis of shear stress saw very similar trends in normal and stenosed arteries, with lower angulation profiles experiencing higher values of shear stress at the Ostia. In the cases of arteries of higher angulation with a non-critical stenosis, the possibility of worsening of stenosis into an opprobrious stage remains a concern.

Numerical simulation of pulsatile blood flow: a study with normal artery, and arteries with single and multiple stenosis

Numerical simulations of pulsatile transitional blood flow through symmetric stenosed arteries with different area reductions were performed to investigate the behavior of the blood. Simulations were carried out through Reynolds averaged Navier-Stokes equations and well-known k-ω model was used to evaluate the numerical simulations to assess the changes in velocity distribution, pressure drop, and wall shear stress in the stenosed artery, artery with single and double stenosis at different area reduction. This study found a significant difference in stated fluid properties among the three types of arteries. The fluid properties showed a peak in an occurrence at the stenosis for both in the artery with single and double stenosis. The magnitudes of stated fluid properties increase with the increase of the area reduction. Findings may enable risk assessment of patients with cardiovascular diseases and can play a significant role to find a solution to such types of diseases.

Mathematical Modeling of Unsteady Solute Dispersion in Bingham Fluid Model of Blood Flow Through an Overlapping Stenosed Artery

An artery narrowing referred to as atherosclerosis or stenosis causes a reduction in the diameter of the artery. When blood flow through an artery consists of stenosis, the issue of solute dispersion is more challenging to solve. A mathematical model is developed to examine the unsteady solute dispersion in an overlapping stenosed artery portraying blood as Bingham fluid model. The governing of the momentum equation and the constitutive equation is solved analytically. The generalized dispersion model is imposed to solve the convective-diffusion equation and to describe the entire dispersion process. The dispersion function at steady-state decreases at the center of an artery as the stenosis height increase. A reverse behavior is shown at an unsteady-state. As the plug core radius, time and stenosis height increase, the dispersion function decreases at the center of an artery. There is a high amount of red blood cells at the center of the artery but no influences near the wall. Hence, this model is useful in transporting the drug or nutrients to the targeted stenosed region in the treatment of diseases and in understanding many physiological processes.

A Hydromechanical Perspective to Study the Effect of Body Acceleration through Stenosed Artery

The spread of numerous deadly diseases such as Thrombosis, Diabetes, Atherosclerosis and other cardiac diseases, carry on to be major root of demise and growing public curiosity about the prevention and treatment of such fatal disorders. Body acceleration has very important role on the flow through stenosed artery. In this research work a problem for irregular development in the inner wall of the artery is known atherosclerosis that settled as a result of buildup due to cholesterol on the arterial wall has been discussed. In this work the effects of body acceleration, slip velocity in presence of catheter on the wall shear, velocity profile and flow rate reveal the graphical finding for pulsatile blood flow in narrow blood vessels. Here it is shown that flow rate, velocity and shear stress escalate as body acceleration increases.

Fluid-Structure Interaction in Coronary Stents: A Discrete Multiphysics Approach

Stenting is a common method for treating atherosclerosis. A metal or polymer stent is deployed to open the stenosed artery or vein. After the stent is deployed, the blood flow dynamics influence the mechanics by compressing and expanding the structure. If the stent does not respond properly to the resulting stress, vascular wall injury or re-stenosis can occur. In this work, a Discrete Multiphysics modelling approach is used to study the mechanical deformation of the coronary stent and its relationship with the blood flow dynamics. The major parameters responsible for deforming the stent are sorted in terms of dimensionless numbers and a relationship between the elastic forces in the stent and pressure forces in the fluid is established. The blood flow and the stiffness of the stent material contribute significantly to the stent deformation and affect its rate of deformation. The stress distribution in the stent is not uniform with the higher stresses occurring at the nodes of the structure. From the relationship (correlation) between the elastic force and the pressure force, depending on the type of material used for the stent, the model can be used to predict whether the stent is at risk of fracture or not after deployment.