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In this article we derive semi-analytical/numerical solutions for transport phenomena (momentum, heat and mass transfer) in a nanofluid regime adjacent to a nonlinearly porous stretching sheet by means of the Homotopy analysis method (HAM). The governing equations are reduced to a nonlinear, coupled, non-similar, ordinary differential equation system via appropriate similarity transformations. This system is solved under physically realistic boundary conditions to compute stream function, velocity, temperature and concentration function distributions. The results of the present study are compared with numerical quadrature solutions employing a shooting technique with excellent correlation. Furthermore the current HAM solutions demonstrate very good correlation with the non-transpiring finite element solutions of Rana and Bhargava (Commun. Nonlinear Sci. Numer. Simul. 17:212–226, 2012). The influence of stretching parameter, transpiration (wall suction/injection) Prandtl number, Brownian motion parameter, thermophoresis parameter and Lewis number on velocity, temperature and concentration functions is illustrated graphically. Transpiration is shown to exert a substantial influence on flow characteristics. Applications of the study include industrial nanotechnological fabrication processes.

A time-independent finite difference method is developed to simulate fluid sloshing in a three-dimensional tank. The developed numerical scheme is verified by the rigorous benchmark tests. The experiment measurement of liquid sloshing in a 3D tank was also carried out in this study to further validate the accuracy of the present numerical results. Transient waves can change their types naturally in the time domain, especially for a tank excited by resonant frequencies. In this study, if the excitation frequencies are far from the fundamental natural frequency and there are four types of stable sloshing waves discovered due to the oblique horizontal excitation: “diagonal”, “single-directional”, “square-like”, and “irregular” waves. Besides, the swirling waves can only be generated for a partially-filled tank excited at near resonant frequency with oblique horizontal excitation. The evolution of forces induced by different sloshing waves acting on the tank walls is calculated and discussed in this work. In addition, the dynamics of sloshing force induced by swirling waves are explored in detail. The force of the single-directional waves acting on the tank bottom is time-invariant but the other types of sloshing waves show a beating phenomenon which is attributed to the momentum flux across the free surface and the vertical inertia of sloshing fluid. The effect of various oblique excitation directions of the tank on liquid sloshing is discussed as well. The horizontal hydrodynamic force of sloshing waves acting on the mid-section of the left wall of the tank is dominated by the added mass effect if the external excitation frequency is larger than 4 times the lowest natural frequency ( ω 1 ) of the tank with partially-filled fluid. On the other hand, the wave elevation of sloshing waves plays a key effect on the horizontal sloshing-induced force when the excitation frequency of the tank is less than 4 ω 1 . A novel mechanism is presented to describe the phenomenon of alternate switch directions of the swirling waves. The relationship between the external force and the sloshing hydrodynamic force is the major factor to trigger the switch direction of the swirling waves. The influence of different base ratios of a rectangular tank on kinematic and dynamic responses of sloshing fluid is also explored in this work.

Three-dimensional blood flow in a human left ventricle is studied via a computational analysis with magnetic resonance imaging of the cardiac motion. Formation, growth and decay of vortices during the myocardial dilation are analyzed with flow patterns on various diametric planes. They are dominated by momentum transfer during flow acceleration and deceleration through the mitral orifice. The posterior and anterior vortices form an asymmetric annular vortex at the mitral orifice, providing a smooth transition for the rapid inflow to the ventricle. The development of core vortex accommodates momentum for deceleration and for acceleration at end diastolic atrial contraction. The rate of energy dissipation and that of work done by viscous stresses are small; they are approximately balanced with each other. The kinetic energy flux and the rate of work done by pressure delivered to blood from ventricular dilation is well balanced by the total energy influx at the mitral orifice and the rate change of kinetic energy in the ventricle.

Application of magnetic fields to medical science is growing rapidly, with the development of novel magnetic pumps, hydromagnetic separation devices, etc. In this paper, we study the dual control mechanisms of transverse magnetic field and porous media filtration on viscous convection heat transfer in a buoyancy-driven blood flow regime in a vertical pipe, as a model of a blood separation configuration. Non-Newtonian characteristics of the blood are modeled with the well-tested, thermodynamically rigorous micropolar model introduced by Eringen. Porous media effects are simulated with a Darcy–Forchheimer drag force model. The two-point boundary value problem is normalized and the resulting dimensionless linear momentum, angular momentum (Eringen micro-rotation) and energy conservation equations are solved by the Differential Transform M ethod (DTM). The convergence analysis elucidates that the DTM yields exceedingly accurate results, which are validated with a comparison with optimized fourth-order Runge–Kutta numerical quadrature. The influence of micropolar vortex viscosity parameter (Eringen parameter (Er), Hartmann magnetohydrodynamic number ( Ha), aspect ratio (A), Darcy number ( Da), heat generation/absorption parameter (α) and Grashof number on the flow variables are studied in detail. The present study has important applications in magnetic field control of biotechnological (hemodynamic) processes, biomagnetic device technology, etc. Copyright © 2010 John Wiley & Sons, Ltd.

Application of double-barreled cannon stent grafts aortic repair (DoBAR) was reported in 2011 for extremely large aortic aneurysms of patients when there was no proper size of grafts for the emergent treatment. Fixation characteristics of the double stent grafts are obtained in a laboratory setting, and are incorporated with those of single Zenith TX2 grafts of sizes from 34 to 42[Formula: see text]mm. Radial stress and shear increase linearly with the oversizing parameter but decrease with increasing stent diameter. The slope of the linear relationship is practically the same for this group of grafts. When the original circular stent grafts of diameter 36 and 38[Formula: see text]mm are deformed to form DoBAR of diameter 44 or 46.4[Formula: see text]mm, the formation could provide higher radial stress and shear to secure fixation for endo-aortic repair. The experimental results of single and DoBAR grafts can be incorporated for clinical application of DoBAR for emergent treatment.

This study extracted hemodynamic information from echocardiogram to complement the left ventricle ejection fraction and the stroke volume for cardiac evaluation and diagnosis. The dynamic characteristics of irregular wall motions can be analyzed by kinetic energy fluxes transferred from the left ventricle to the blood flow. A set of cardiac indices is developed for quantification and classification of echocardiogram for clinical application. The pumping characteristics can be further quantified through the work done by pressure and viscous stresses of the ventricle.

In this paper a mathematical model of the two-dimensional fully developed steady, viscous flow of a non-conducting biomagnetic micropolar fluid through a Darcian porous medium model of tissue is presented. The momentum conservation equations with zero pressure gradient are extended to incorporate the biomagnetic body force terms along the X and Y axes and also the Darcian linear drag in the X and Y directions, with appropriate boundary conditions. An angular momentum equation is also included for the spin of the microelements. The equations are non-dimensionalized using a set of transformations following Tzirtzilakis et al. (2004). A finite element solution is generated to the resulting non-dimensional model and the effects of biomagnetic number (NH), Darcy number (Da) and micropolar viscosity ratio parameter (R) on the X- and Y-direction velocity profiles is studied in detail. A number of special cases of the flow model are also discussed. The numerical solution is compared with a finite difference solution using central differencing and found to be in excellent agreement The model finds applications in biomedical device technology, blood transport in tumors, brain tissue and soft connective tissue zones as well as in fundamental hydrodynamics of ferrofluids in porous materials.

Blood flow characteristics in the normal left ventricle are studied by using the magnetic resonance imaging, the Navier-Stokes equations, and the work-energy equation. Vortices produced during the mitral valve opening and closing are modeled in a two-dimensional analysis and correlated with temporal variations of the Reynolds number and pressure drop. Low shear stress and net pressures on the mitral valve are obtained for flow acceleration and deceleration. Bernoulli energy flux delivered to blood from ventricular dilation is practically balanced by the energy influx and the rate change of kinetic energy in the ventricle. The rates of work done by shear and energy dissipation are small. The dynamic and energy characteristics of the 2D results are comparable to those of a 3D model. MOH (Min. of Health, S’pore) Published version

Ejection of blood from the left ventricle to the aorta is studied using two-dimensional Navier–Stokes equations, the work-energy equation and the magnetic resonance imaging of a normal ventricular motion. Vortex shedding in the sinuses of Valsalva is dominated by the aortic jet, flow acceleration and valve motion. Momentums produced by ventricular contraction are in concert with vortices in the ventricle for blood ejection. Shear stresses and net pressures on the aortic valve are calculated during valve opening and closing. The rate of work done by shear and the energy dissipation in the ventricle are small. The Bernoulli energy flux delivered to blood from ventricular contraction is practically balanced by energy flux at the aortic root and the rate change of kinetic energy in the ventricle. ASTAR (Agency for Sci., Tech. and Research, S’pore) Accepted version

Blood flow in distensible arteries is nonlinear and time-dependent. The radial motion of the wall alters the dimension and geometry of the flow field. The nonlinear pulsating flow processes are successfully computed by mapping the wavy flow field to a fixed domain and by casting the geometric, kinematic and dynamic parameters of the flow into a dimensionless form of the Navier–Stokes equations. The complexity of the equations is compensated by a significant advantage in finite difference solutions. It is accomplished by using a fixed regular mesh network to model time-dependent irregular meshes in the physical domain for boundary layer development and vortices in pulsatile flows.

Professor Dr. Shu Chien has been engaged in biomedical research for over half a century. He is without doubt one of the pioneers of the field of hemo - rheology and one of the most prolific and important bioengineering researchers in the world. Cur- rently he is Professor of Bio-Engineering at one of the leading research departments in the world- the Bioengineering Department at the Jacobs School of Engineering at the University of California at San Diego, home to the legendary “father of biomechanics”, Professor Y. C. Fung. He was also President of the Biomedical Engineer- ing Society in 2006–2008. Professor Chien has made immense contributions to our understanding of the rheology of blood, red-cell elasticity, capillary viscosity, ery- throcyte membrane mechanics and leukocyte biofluid dynamics.

Nonlinear pulsatile blood flows in distensible vessels were calculated using an implicit finite-difference scheme. The time-dependent wavy lumen was mapped to a fixed rectangular domain. The transient geometric, kinematic, and dynamic boundary conditions were grouped as dimensionless parameters in the Navier-Stokes equations. The flow was controlled by a time-dependent von Karman number and the dilatation and contraction of the wall. Local acceleration components along the wall, the inlet, and the outlet were employed in the determination of the Neumann boundary condition for the pressure field. The momentum flux associated with wall motion had a significant effect on the flow rate and the resistance coefficient. The interaction of the main flow and flow separation was dominated by flow acceleration and deceleration.

Axisymmetric laminar blood flows in a stenotic model vessel are calculated by using a finite-difference scheme of the Navier-Stokes equations. The wavy lumen are transformed to a rectangular region with fine and irregular meshes mapped to regular ones in the computational domain. The pulsating flow is controlled by a time-dependent von Karman number. At the upstream and downstream ends, the local acceleration is employed to replace the Neumann boundary condition for solving the pressure field from the divergence of the Navier-Stokes equations, resulting in a new treatment on the inlet and outlet conditions for transient flow problems. The kinematic and dynamic characteristics of vortices in the pulsating flow processes are analyzed along with the pressure and shear fields.

Giant fusiform aneurysms are rare vascular anomalies that due to their size are often difficult to manage. We describe one such aneurysm that was managed with a superficial temporal to middle cerebral artery bypass followed by the application of a single clip just distal to the vascular dilation. Follow-up angiography has shown aneurysm obliteration by the process of retrograde thrombosis.

Earthquake response of reservoir sediment and its dynamic interaction with the impounded water are analyzed using a two‐dimensional model of poroelastic media. The pressure wave equation for the pore water and the sediment is solved by an implicit finite difference method coupled with a fast Poisson solver. The numerical scheme requires a conversion of the boundary condition on the rigid dam face to a Dirichlet boundary condition. For incompressible impounded water, a reduction in the dynamic pressure appears at the onset of ground motion when the bulk modulus of pore water in the sediment is compressible. The pressure rises rapidly with the celerity of pressure wave and exceeds that of Westergaard's solution for the incompressible case without the sediment. Augmentation of the pore pressure is primarily caused by the inertia of the sediment and the Stokes drag. The hydrodynamic pressures on the dam face could exceed significantly those calculated by an incompressible two‐fluid model for an idealized liqu...

Background— Growing evidence suggests that intramyocardial biomaterial injection improves cardiac functions after myocardial infarction (MI) in rodents. Cell therapy is another promising approach to treat MI, although poor retention of transplanted cells is a major challenge. In this study, we hypothesized that intramyocardial injection of self-assembling peptide nanofibers (NFs) thickens the infarcted myocardium and increases transplanted autologous bone marrow mononuclear cell (MNC) retention to attenuate cardiac remodeling and dysfunction in a pig MI model. Methods and Results— A total of 40 mature minipigs were divided into 5 groups: sham, MI+normal saline, MI+NFs, MI+MNCs, and MI+MNCs/NFs. MI was induced by coronary occlusion followed by intramyocardial injection of 2 mL normal saline or 1% NFs with or without 1×10 8 isolated autologous MNCs. NF injection significantly improved diastolic function and reduced ventricular remodeling 28 days after treatment. Injection of MNCs alone ameliorated systolic function only, whereas injection of MNCs with NFs significantly improved both systolic and diastolic functions as indicated by +dP/dt and −dP/dt (1214.5±91.9 and −1109.7±91.2 mm Hg/s in MI+NS, 1693.7±84.7 and −1809.6±264.3 mm Hg/s in MI+MNCs/NFs, respectively), increased transplanted cell retention (29.3±4.5 cells/mm 2 in MI+MNCs and 229.4±41.4 cells/mm 2 in MI+MNCs/NFs) and promoted capillary density in the peri-infarct area. Conclusions— We demonstrated that NF injection alone prevents ventricular remodeling, whereas cell implantation with NFs improves cell retention and cardiac functions after MI in pigs. This unprecedented combined treatment in a large animal model has therapeutic effects, which can be translated to clinical applications in the foreseeable future.

A time-independent finite difference scheme is developed and applied to analyze the viscous flow past a translating circular cylinder. In this scheme, the instantaneous moving cylinder face is mapped to a fixed boundary and the computational domain is, therefore, time independent. Large Reynolds number and high oscillating frequency of moving cylinder are used in the analysis. The finite difference approximation and algorithm were validated by the reported numerical simulation and flow visualization. The vorticity and streamline patterns developments were described and discussed. The surface vorticity distribution and position of separation point versus phases of oscillating stages were discussed. The flow behaviors of various amplitudes of exciting velocity and frequencies of moving cylinder are simulated and compared. The in-line forces on cylinder during cylinder oscillation were calculated and are in good agreement with those predicted by Morison’s equation. The developed scheme can be extended to analyze the viscous flow passing an arbitrary moving cylinder.

The solution for finite deformations of a solid viscoelastic cylinder subjected to extension and torsion is presented. An experiment is performed on a latex rubber cylinder. Both axial load and torque histories of the deformed cylinder are recorded. The theoretical coupling relationship between torsion and extension is verified. With the theoretical and experimental results, the viscoelastic properties of the cylinder can be obtained.

A span‐wise variation of nonlinear hydrodynamic pressures on dams during earthquakes was studied using a finite‐difference approximation of Euler's equations coupled with the nonlinear free‐surface boundary condition. The pressure distribution was sensitive to both the longitudinal and lateral components of the ground motion. The dynamic effect of reservoir banks would increase with the dam width. The inward motion of a reservoir bank produced higher pressures on one side while the outward motion of the other bank resulted in a reduction in hydrodynamic pressures. The combined effect can be effectively obtained when the geometric parameters of a dam/reservoir system, the changes in water surface, and the earthquake force are cast in the equations of motion. In this case, the time‐dependent water surface is transformed to the horizontal plane, and the flow field is mapped onto a cubic region, making it convenient to model the complex reservoir geometry and the wavy water surface by the finite‐difference me...

The dynamic interaction between nonlinear hydrodynamic pressures and the vibration of a concrete gravity dam is analyzed by coupling Euler's equations with a finite element model of the dam. The earthquake force components in the horizontal and vertical directions are cast as the forcing functions in the finite difference equations for fluid motion. The results are compared with those associated with a rigid dam motion. The pressure distributions are very sensitive to dam vibration and surface wave. For El Centra ground motion recorded on October 15, 1979, the calculated rise of the water surface on Pine Flat Dam was 8 ft (2.7 m), indicating a strong nonlinear effect on hydrodynamic pressures and the potential hazards of surface waves in the reservoir.

A two-phase thermo-hydrodynamic model is presented for transport in the vertical chamber of a porous media blood filtration device. A non-Darcy drag force formulation was employed. The Marble–Drew fluid–particle suspension model was used to simulate the plasma phase and the suspension (erythrocyte) particle phase. The non-dimensional transport equations were solved using a semi-computational procedure known as the homotopy analysis method (HAM). With the judicious use of the auxiliary parameter ℏ, HAM affords a powerful mechanism to adjust and control the convergence region of solution series. This method provides an efficient approximate analytical solution with high accuracy, minimal calculation and avoidance of physically unrealistic assumptions. Detailed computations are presented for the effects of Grashof number (Gr), momentum inverse Stokes number (Skm), Darcy number (Da), Forchheimer number (Fs), particle loading parameter (PL), buoyancy parameter (B) and temperature inverse Stokes number (SkT) on the dimensionless fluid phase velocity (U), dimensionless particle phase velocity (Up), dimensionless fluid phase temperature (Φ) and the dimensionless temperature of particle phase (Φp). A Prandtl number of 25 was used to simulate blood at room temperature. Excellent correlation was obtained between the HAM and numerical shooting quadrature solutions. The results indicated that there is a strong decrease in fluid phase velocities with increasing Darcian (first order) drag and second-order Forchheimer drag, and a weaker reduction in particle phase velocity field. Applications of the study include porous media bio-filtration devices and dialysis simulations.

An optimistic view on biomechanics research is taken primarily from the remarkable beginning recently made in the integration of applied mechanics and biology. The paper projects the future research in the mechanics of physiological systems, biomechanics of trauma, mechanics in molecular biology, animal models in clinical biomechanics, prostheses, artifical organs, instruments, and equipment. Also considered are the interface between engineering mechanics and biomechanics, collaboration between life scientists and engineers, and the educational implication of advances in bioengineering.

The force/deformation relationship of the exposed spinal cord of cats was studied when the force was gradually applied posteriorly at T10. A linear elastic behavior was identified for deformation less than 0.5 mm, but it was not observed when the static force was no longer supported by the dural sheath. Nonlinear force/deformation, along with a strong hysteresis during a cycle of compression and decompression. The mechanical behavior remained practically the same in a repeated loading if the deformation was less than 2 mm. The motor function of cats did not recover after the cord had been compressed to 4 mm. The associated static force was about 15% of the dynamic force producing the same deformation.

An in-vivo experimental technique was employed to determine the linear and nonlinear characteristics of viscoelastic properties of the spinal cord of anesthetized cats. The stress relaxation and recovery curves were reproducible in a group of cat experiments. The data of linear viscoelastic properties were used to develop a power law model with Boltzmann’s convolution integral. The model was capable of predicting a prolonged stress relaxation and recovery curve. For larger deformation, the results were quantified using a nonlinear analysis of viscoelastic response of the spinal cord under the uniaxial experiment.

A finite‐difference analysis was employed to calculate nonlinear hydrodynamic pressures on vertical and inclined faces of dams. Two idealized ground accelerations and an actual earthquake excitation were used as the prescribed boundary condition. This dynamic condition and the free surface profile were cast in a dimensionless form of the basic equations, making the moving boundary problem simpler in computational analysis. The effect of water compressibility could be augmented by the nonlinear effect. Comparison of the results between inviscid and viscous analyses reflected not only the insignificant viscous effect but also the potential numerical noise associated with the viscous solution.

An in vivo experimental method was developed to measure the mechanical or rheological properties of the spinal cord of anesthetized cats. This novel approach resulted in the measurements of the tensile force in the cord and the modulus of the spinal cord tissue under longitudinal elongation.

The fluid flow and particle motion in a tube are solved numerically by coupling the Navier-Stokes equations with the dynamic equation of a particle. The particulate flow is simulated from rest under a prescribed pressure drop. The symptotic steady state solution is in good agreement with the analytical solution of creeping flow and with the experimental data reported in the literature. The present computational analysis explores the Reynolds numbers effects on the flow processes and gives some insight into qualitative similarities of the kinematics and dynamics of particulate flows. The resistant coefficient, the apparent viscosity, the tube hemotocrit, and the distribution of viscous stresses and pressure on the particle and on the capillary wall are considered along with the curvilinear flow patterns.

An in vivo experimental method was developed to measure the mechanical or rheological properties of the spinal cord of anesthetized cats. This novel approach resulted in measurements of the tensile force in the cord and the modulus of the spinal cord tissue under longitudinal elongation. Both sensory and motor function of the cats recovered within a week after a spinal cord segment had been stretched by a 50% elongation.

This article summarizes the biomechanical relationship of the spinal column to load stresses with respect to column failure, and the resulting associated central nervous system injury. In addition, it presents pertinent animal research, which has focused onto the development standardized animal spinal cord injury model.

An in-vivo experiment was developed to identify the biorheological properties of the spinal cord of puppies under uriaxial deformation. For strain less than 4.5%, the ratio between stress and strain was about 2.65 x 106 dyne/limbs of the puppies were recoverable after the spinal cord segment at L1 was stretched once by 10-50%.