Computational simulations of hybrid mediated nano-hemodynamics (ag-au/blood) through an irregular symmetric stenosis

This article examines theoretically and numerically the unsteady two-dimensional blood flow through a diseased artery featuring an irregular stenosis. An appropriate geometric model is adopted to simulate the irregular stenotic artery. Inspired by drug delivery applications for blood vessels, the impact of hybrid nanoparticles on blood flow using a modified Tiwari-Das model is discussed. The blood is examined to have a homogenous suspension of hybrid nanoparticles. Reynolds’ viscosity model is applied in the formulation to represent the temperature dependency of blood. The two-dimensional governing conservation equations for momentum and heat transfer with buoyancy effect are simplified by considering the mild stenotic approximation. A finite-difference technique is deployed to numerically discretize the transformed non-dimensional model. Extensive graphical results for blood flow characteristics are obtained by MATLAB code. Comprehensive visualization of the effects of hemodynamic, geometric and nanoscale parameters on transport characteristics is provided. The problem is conducted for silver and silver-gold hybrid mediated blood flow models, and experimental values of blood and these biocompatible metallic nanoparticles. A comparison between silver and hybrid nanofluid is obtained which promotes the use of hybrid nanoparticles in successfully achieving clinically more beneficial results associated with nano-drug delivery in diseased hemodynamics. Enhancement in viscosity parameter induces axial flow acceleration in the stenotic region while lower thermal conductivity decreases the temperature magnitudes. Furthermore, with time variation, the pressure gradient is found to be lower in coronary arteries comparatively to femoral arteries. The simulations are relevant to transport phenomenon in nano-drug targeted delivery in haematology

Unsteady hybrid nanoparticle-mediated magneto-hemodynamics and heat transfer through an overlapped stenotic artery : biomedical drug delivery simulation

Two-dimensional laminar hemodynamics through a diseased artery featuring an overlapped stenosis was simulated theoretically and computationally. This study presented a mathematical model for the unsteady blood flow with hybrid biocompatible nanoparticles (Silver and Gold) inspired by drug delivery applications. A modified Tiwari-Das volume fraction model was adopted for nanoscale effects. Motivated by the magnetohemodynamics effects, a uniform magnetic field was applied in the radial direction to the blood flow. For realistic blood behavior, Reynolds’ viscosity model was applied in the formulation to represent the temperature dependency of blood. Fourier’s heat conduction law was assumed, and heat generation effects were included. Therefore, the governing equations were an extension of the Navier-Stokes equations with magneto-hydrodynamic body force included. The two-dimensional governing equations were transformed and normalized with appropriate variables, and the mild stenotic approximation was implemented. The strongly nonlinear nature of the resulting dimensionless boundary value problem required a robust numerical method, and therefore the FTCS algorithm was deployed. Validation of solutions for the particular case of constant viscosity and non-magnetic blood flow was included. Using clinically realistic hemodynamic data, comprehensive solutions were presented for silver, and silver-gold hybrid mediated blood flow. A comparison between silver and hybrid nanofluid was also included, emphasizing the use of hybrid nanoparticles for minimizing the hemodynamics. Enhancement in magnetic parameter decelerated the axial blood flow in stenotic region. Colored streamline plots for blood, silver nano-doped blood, and hybrid nano-doped blood were also presented. The simulations were relevant to the diffusion of nano-drugs in magnetic targeted treatment of stenosed arterial disease

Modeling and analysis of magnetic hybrid nanoparticle (Au-Al2O3/blood) based drug delivery through a bell-shaped occluded artery with Joule heating, viscous dissipation and variable viscosity effects

The present work deals with the impact of hybrid nanoparticles (Au-Al2O3/Blood) on the blood flow pattern through a porous cylindrical artery with bell-shaped stenosis in the presence of an external magnetic field, Joule heating, and viscous dissipation by considering twodimensional pulsatile blood flow. The temperature-dependent viscosity model is utilized in this model. The blood flow is assumed to be unsteady, laminar, viscous, and incompressible. The mild stenotic presumption normalizes and reduces the bi-directional flow to uni-directional. The Crank-Nicolson scheme is applied to solve the continuity, momentum, and energy equations with appropriate initial and boundary conditions. The acquired results of the work are presented graphically. They have been examined for several values of the dimensionless parameters such as Magnetic number (M2 ), Darcy number (Da), Grashof number (Gr), viscosity parameter (β0), Reynolds number (Re), Eckert Number (Ec), Prandtl number (Pr), different concentration of both the nanoparticles (φ1, φ2), and pressure gradient parameter (B1). The velocity contours for different emerging parameters have been drawn to analyze the overall behavior of blood flow patterns. The non-dimensional velocity profile enhances with increment in values of Da, implying that the medium’s permeability provides less barrier to flow. The cumulative impact of Joule Heating and viscous dissipation are discussed. It demonstrates that increasing viscous dissipation (Ec) and Joule heating (M2 ) parameter simultaneously raise the nanofluid temperature since the mechanical energy is transformed to thermal energy within molecules, which causes a hike in temperature. The findings reveal that hybrid nanoparticles (Au-Al2O3/blood) effectively reduce hemodynamic variables such as wall shear stress and resistance impedance. Results indicate that nanoparticles may be helpful to keep the blood velocity under control and allow the surgeons to adjust it as and when required. The present work aims to get insight into the treatment of atherosclerosis without surgery, lower medical costs, and reduce post-surgical complications. Also, it has broad implications in treating various conditions, including cancers, infections, and the removal of blood clots. The current findings are consistent with recent findings in earlier blood flow research studies

Micropolar pulsatile blood flow conveying nanoparticles in a stenotic tapered artery : non-Newtonian pharmacodynamic simulation

Two-dimensional rheological laminar hemodynamics through a diseased tapered artery with a mild stenosis present is simulated theoretically and computationally. The effect of different metallic nanoparticles homogeneously suspended in the blood is considered, motivated by drug delivery (pharmacology) applications. The Eringen micropolar model has been deployed for hemorheological characteristics in the whole arterial region. The conservation equations for mass, linear momentum, angular momentum (micro-rotation), and energy and nanoparticle species are normalized by employing suitable non-dimensional variables. The transformed equations are solved numerically subject to physically appropriate boundary conditions using the finite element method with the variational formulation scheme available in the FreeFEM++ code. A good correlation is achieved between the FreeFEM++ computations and existing results. The effect of selected parameters (taper angle, Prandtl number, Womersley parameter, pulsatile constants, and volumetric concentration) on velocity, temperature, and microrotational (Eringen angular) velocity has been calculated for a stenosed arterial segment. Wall shear stress, volumetric flow rate, and hemodynamic impedance of blood flow are also computed. Colour contours and graphs are employed to visualize the simulated blood flow characteristics. It is observed that by increasing Prandtl number (Pr), the micro-rotational velocity decreases i.e., microelement (blood cell) spin is suppressed. Wall shear stress decreases with the increment in pulsatile parameters (B and e), whereas linear velocity increases with a decrement in these parameters. Furthermore, the velocity decreases in the tapered region with elevation in the Womersley parameter (α). The simulations are relevant to transport phenomena in pharmacology and nano-drug targeted delivery in hematology

Oxygen Delivery Strategies in Tissue-Engineering Constructs

The supply of nutrients and the removal of waste products play a major role in tissue engineering. From all the nutrients necessary for cells seeded on scaffolds for tissue regeneration, oxygen is the limiting component due to its low solubility in culture media while cells consume five to six moles of oxygen for every mole of monosaccharide. The aim of the present work was to develop different strategies to improve the supply of oxygen to human coronary artery smooth muscle cells (HCASMC) seeded on three dimensional (3D) porous biostable polyurethane scaffolds. As a springboard for the study, the measured value of oxygen diffusivity through porous polyurethane scaffolds, fabricated by using pressure differential/particulate leaching technique, was used to screen the best polymer concentration. Scaffolds fabricated form 15 wt% polymer concentration not only had higher oxygen diffusivity but also have better pore interconnectivity as shown by SEM image analysis. Moreover a convective mass transfer approach showed an improvement in the infiltration of HCASMCs into the 3D scaffolds. An oxygen carrier molecule, perfluorodecalin (PFD), was found to improve dissolved oxygen concentration in culture media. PFD was shown to be not only non-toxic to HCASMC but also have no significant effect on the morphology of the HCASMCs. Therefore, higher cell density and infiltration depth into the polyurethane scaffolds were observed when HCASMCs were cultured in a media containing PFD. The final stage of this work was to introduce an oxygen vector into the skeleton of polyurethane scaffolds. For this reason, inert Zeolite Y particles were fluorinated and shown to enhance the amount of dissolved oxygen when suspended in culture media. Fluorinated Zeolite (FZ) particles were then embedded into polyurethane scaffolds without modifying the porosity and morphology of the 3D structures. Subsequently, higher cell density and infiltration depths were observed when HCASMCs were cultured on FZ particles embedded polyurethane scaffolds in contrast to bare polyurethane scaffolds. Taken together, these data show three different but equally advantageous strategies of improving the supply of oxygen to HCASMC seeded into the interstices of 3D polyurethane scaffolds

SOLID-SHELL FINITE ELEMENT MODELS FOR EXPLICIT SIMULATIONS OF CRACK PROPAGATION IN THIN STRUCTURES

Crack propagation in thin shell structures due to cutting is conveniently simulated using explicit finite element approaches, in view of the high nonlinearity of the problem. Solidshell elements are usually preferred for the discretization in the presence of complex material behavior and degradation phenomena such as delamination, since they allow for a correct representation of the thickness geometry. However, in solid-shell elements the small thickness leads to a very high maximum eigenfrequency, which imply very small stable time-steps. A new selective mass scaling technique is proposed to increase the time-step size without affecting accuracy. New ”directional” cohesive interface elements are used in conjunction with selective mass scaling to account for the interaction with a sharp blade in cutting processes of thin ductile shells