The considerable contribution of parasitic measurement effects in fluid flow machines of small performance classes remains a major challenge in the assessment of corresponding hydraulic characteristics such as hydraulic losses and efficiencies. However, a standardized experimental approach to accurately quantify such properties is of paramount importance for the design of rotary blood pumps with low hydraulic power and torque. This study proposes a novel test bench to accurately assess hydraulic and mechanical characteristics of pumps designed for a mechanical power input of up to 20,9W, a maximum rotational speed of 7000min −1 and a maximum torque of 10mNm. Key feature of the iteratively optimized test bench is a torque measuring shaft combined with ceramic bearings and seals that minimizes the friction torque to 0.66–0.69mNm. Preliminary measurements for a double-inflow, double-outflow circulatory support pump with maximum torque of 1.71mNm and hydraulic power of 0.15W, demonstrated both the feasibility of the hydraulic and mechanical design of the test bench and the reproducibility of the measured data. These results warrant the applicability of the presented test-bench for the investigation of typical cardiac assist systems as well as for all other hydraulic flow machines of the equivalent performance class.

Blalock-Taussig (BT) Shunt is a palliative surgical procedure used during a Norwood surgery on a newborn baby suffering from cyanotic heart defects. The BT Shunt can increase blood flow in patients’ pulmonary artery which can ease the “Blue Baby Syndrome.” Currently used BT Shunts do not produce a balanced flow distribution to the pulmonary arteries (PAs) which can cause high wall shear stress (WSS) and blood flow separation resulting in blood clots. A modified BT Shunt was designed to partially solve this problem. In our previous work [1], the modified BT Shunt was shown by numerical simulations to have the ability to better control the flow distribution between Innominate Artery (IA) and PA with lower and gradually varying WSS and with improved flow balance to the pulmonary artery at the T-junction of the shunt. The goal of this paper is to computationally evaluate the flow in the modified BT shunt model between innominate and pulmonary artery using a patient specific aorta model. The simulations are performed using the commercial CFD software ANSYS Fluent. The improved modified BT shunt is connected between IA and PA. A change in the length of the shunt can be made to fit it under different conditions of actual patients. In numerical simulations, a full geometry of patient’s aorta is considered. Results for different lengths of the shunt are compared to determine the length that generates the lowest WSS and improved flow distribution to the PAs. It was found that the length of nearly 26mm creates lower WSS and flow rate difference between the two sides of PA at the T-junction attachment of the shunt. A sophisticated computational model was created using SolidWorks and Blender software to create the realistic geometry which included the IA, PA and modified BT shunt. The numerical simulations provide details of the flow field including velocity and pressure field, WSS, and blood damage. Several parameters in shunt design weigh heavily in reducing the thrombosis. This study demonstrates how CFD can be effectively utilized in the design of a medical device such as BT shunt to improve the clinical outcomes in patients.

The purpose of this computational fluid dynamics (CFD) study is to simulate left carotid artery models to evaluate the influence of hematocrit (Hct) level and angle of bifurcation on the formation of atherosclerosis. Bifurcation angle can vary from person to person based on sex, age or diseased condition which has an impact on hemo-dynamic parameters. From the anatomical study, it is seen that the carotid artery bifurcation is the preferential region for atherosclerosis formation. The combination of bifurcation, curvature and diameter change in this bifurcation region causes the blood flow to be complex with recirculation regions and secondary flows which influence hemodynamic changes and the formation of atherosclerosis. Along with the bifurcation angle, the Hct level also influences on changing hemodynamic parameters. As the viscosity of blood is mainly controlled by the Hct level, the hemodynamic parameters of blood are changed on the basis of change in percentage of the Hct level. Therefore, the Hct percentage can act as a risk factor for atherosclerosis formation. We have assessed the probability of vulnerable atherosclerosis formation based on the change of both bifurcation angle and hematocrit level. In this study, three different carotid artery geometries with 40 degree, 48.5 degree, and 63.6 degree angles were simulated at a varying percentage of the Hct level. We discerned these models by using CFD simulation to calculate wall shear stress (WSS), time-averaged wall shear stress (TAWSS) and velocity. The effects of angulation and Hct percentage on the velocity of blood were studied on the plane of the bifurcation region. The carotid artery with 63.6 degree angulation faces more recirculation areas and peak recirculation areas are observed at 25% Hct level. This justifies the reason behind atherosclerosis formation in the artery. We observed low WSS at wider angled models and a high WSS at narrow angled models. WSS value is also affected by the percentage of Hct. In this study, we noticed a lower value of WSS at a lower percentage of Hct which is responsible for atherosclerosis formation. The WSS value of 0.4 Pa was considered as the critical point for the atherosclerosis formation. We also calculated time-averaged wall shear stress (TAWSS) which is similar to the WSS contour plot. Overall, after analyzing the results of velocity, WSS and TAWSS, we concluded that low Hct (around 25% or lower) along with higher bifurcation angle (around 63.6 degree or higher) are more accountable for atherosclerosis formation.

Modeling the dynamics of microbubbles inside confined spaces has many potential applications in biomedicine, sonoporation being one classic example. Sonoporation is the permeabilization of a blood vessel’s endothelial cell membrane by acoustic waves in order to non-invasively deliver large-sized drug molecules into cells for therapeutic applications. By controlled activation of ultrasound contrast agents (UCA) in a microvessel, one can achieve better permeabilization without causing permanent damage associated with high intensity ultrasound. This paper considers numerically, the fluid-structure interactions (FSI) of UCA microbubbles with a microvessel accounting for large deformations. The modeling approach is based on a multi-material compressible flow solver that uses a Lagrangian treatment for numerical discretization of cells containing an interface between two phases and an Eulerian treatment for cells away from material interfaces. A re-mapping procedure is employed to map the Lagrangian solution back to the Eulerian grid. The model is first validated by simulating a microbubble oscillating due to an imposed ultrasound inside a microvessel and good agreement with experiments is obtained for both the bubble and vessel dynamics. The effect of vessel elasticity is then studied and it is shown that increasing the vessel elasticity damps the bubble oscillations. Then the effect of placing the bubble away from the axis of vessel is studied and it is shown that bubbles closer the vessel wall are capable of creating maximum deformation on the wall compared to those away from the wall.

Computational fluid dynamics simulations are conducted to study the hemodialysis process in separation modules containing hollow fiber membranes. Hemodialysis is the filtration process which removes waste out of the blood. In this work, three-dimensional steady-state laminar flow simulations are conducted to investigate the effect of disk baffles on the performance of the hemodialysis process. The uniformly spaced baffles are placed along the axis of the shell within the dialyzer. The disk baffles of diameter 2.85 d h d were considered, where d h d is the shell hydraulic diameter. The inlet solute mass fraction of the blood solution is fixed at 0.00074, while the inlet solute mass fraction of the dialysate solution varied as 0.004 and 0.007. The blood and the dialysate flow rates are fixed. Our results revealed that the presence of disk baffles in the shell mitigates the concentration polarization and yields higher urea permeation. The higher dialysate concentration solute yields a 41.2% increase in the urea permeate rate compared to the lower dialysate solute concentration.

This focus of this study is to understand the relationship between the fluid properties present in and the geometric parameters of stenoses developed in end-stage renal disease (ESRD) patients, after creation of an arteriovenous fistula (AVF). Stenosis is the leading cause of failure in AVF creation and maturation. A fistula is meant to provide an access point for hemodialysis treatment necessary for ESRD patients, but large failure rates in fistula creation and maturation cause reoccurring problems for patients and a disproportionately high amount of spending on ESRD patient care. In the United States alone, ESRD patients account for 1% of the Medicare patient population, but the Centers for Medicare & Medicaid Services spent $35.4 billion, 7.2% of the 2016 Medicare budget on their treatment (United States Renal Data System, 2018 Annual Report). This study uses CFD to simulate blood flowing through venous stenoses of varying lengths and initial flow conditions. Computational modeling allows for specific control of geometric conditions as well as simple generation of resulting properties, such as wall shear stress, that are difficult to acquire in vivo. For this study, five different geometric models were constructed to represent straight vascular segments with varying lengths of stenosis. Each vessel was 4-millimeters in diameter with a 2-millimeter diameter stenosis. The lengths of the inlet and outlet vessel segments adjacent to the stenosis were each four times the vessel diameter. Stenosis lengths of 5, 15, 30, 45 and 60-millimeters were used. Vessels were treated as rigid tubes, and the geometries were created using PTC Creo Parametric (PTC Inc., Needham, MA), a commercially available CAD software. CFD analysis of the flow through the vessel segments was performed using ANSYS Fluent (ANSYS, Inc., Canonsburg, PA) for each geometric model with a range of boundary conditions. The working fluid was blood, treated as a Newtonian fluid for the shear rates present, with dynamic viscosity of 2.55 × 10 −3 kg/m-s and density of 1060 kg/m 3 . To model the range of pressure experienced by vessels during the cardiac cycle, simulations were performed using a range of pressure values at the vessel inlet. The boundary condition used at the inlet was a static pressure ranging from 50 to 160 mmHg in increments of 10 mmHg for each geometric model. Outflow pressure values of 10, 15, and 20mmHg were used on the outlet boundary. As expected, flow rate through the system was found to increase linearly with inlet pressure for each geometry and outlet pressure. Flow rate decreased logarithmically as stenosis length increased for each inlet and outlet pressure. Flow rate through the system also decreased as outflow pressure increased, as it would in the presence of further downstream blockages in patients. The data collected here shows under which flow conditions different stenosis geometries can result in a failed fistula, as well as under which conditions the stenosis alone will not prevent the fistula from providing the required flow for dialysis treatment.

Use of computational fluid dynamics (CFD) in the field of blood-contacting medical device design and analysis has been growing in recent years. For example, the U.S. Food and Drug Administration (FDA) Center of Devices and Radiological Health (CDRH) has accelerated interest in industry and academia with nozzle and blood pump benchmarks to uncover best practices and to hopefully elevate the status of CFD to be applied as a safety analysis tool for medical devices. One area, not discussed as often as the pure simulation is the design optimization of hemodynamic devices. A systematic shape “optimization” should be distinguished from a simple “design improvement” by performing many flow field computations and design iterations to improve performance. In this paper, the shape optimization of a trumpet-tipped inflow cannula is presented using a single-objective genetic algorithm (GA) to minimize the blood damage. Many varying accounts in the literature have pointed to the advantages of the trumpet-tipped left ventricular assist device (LVAD) cannula for low blood damage and uniform velocity distribution with little to no backflow when compared to other shapes such as blunt, beveled and caged cannulas.

The goal of this study is to create an optimized Blalock-Taussig shunt used to temporarily repair pulmonary vascular blockages allowing a child time to grow so a more permanent surgical repair of the heart and vasculature can be performed. Blalock-Taussig or BT shunts are a surgical procedure performed on infants suffering from cyanosis or “Blue Baby Syndrome.” A BT shunt is an artificial vessel placed between the right ventricle and the pulmonary artery to increase blood flow in the lung and blood oxygen saturation levels. In a study of 96 patients with currently in use modified BT shunts, 32 patients (21%) had greater than 50% stenosis caused by myofibroblastic proliferation at the shunt lumen due to shunt geometry [1]. A 2007 study by the cardiac surgery division of Johns Hopkins Medical Institutions found an operative mortality rate of 14% (227 of 1,574) with patients undergoing BT surgery [2]. In this paper, the flow of blood through several different BT shunt configurations from actual patient data was analyzed using the commercial CFD software ANSYS Fluent. Results from each shunt’s analysis were then compared to determine the shunt parameters with optimal flow dynamics for use in infants suffering from pulmonary vascular blockage. It was found that the entrance boundary of current BT shunts caused blood flow hindrances due to high wall shear values and flow separation. A newly designed shunt was proven to partially fix this problem; however, a superior model could be optimized by using characteristics from currently used shunts and CFD results. Many iterations and designs of BT shunts were made using Solidworks, a solid modeling computer-aided design program, and were tested using Fluent to create a shunt optimized by smoothening the transition between areas of high and low wall shear stress, lowering the overall maximum wall shear stress, reducing flow separation, and equalizing the flow to the left and right lung. All these factors contribute to the chance of thrombosis and morbidity within patients. The resultant model shunt showed drastic improvement in lowering the average wall shear stress by more than 85% at the initial boundary with over 20% drop in overall average wall shear. It also achieved a decline of the maximum wall shear stress by over 25% while negating the possibility of any flow separation and improving the equality in flow to the left and right lung by more than 60%.

Percutaneous coronary intervention (PCI) is widely used as a treatment for ischemic heart disease. In particular, a high procedural precision of PCI for the left main coronary artery (LMCA), which supplies coronary artery blood to large amount of myocardium, is required. The restenosis after stent placement and target lesion revascularization of side branches (SB) is still a clinical issue. Regarding the stent implantation for bifurcation or trifurcation lesion, the stent struts should jail the inlets of SB. In such a situation, we clinically do the kissing balloon technique (KBT) to remove the struts existing at the opening of SB. As well as KBT, the proximal optimization technique (POT), which presses the stent against the wall, is also commonly used. However, merits of therapeutic strategies of KBT and POT for the branch are not confirmed from the fluid-dynamical viewpoint. In this study, we examined the influence of a stent in left main coronary artery on blood flow by employing CFD simulations. We investigated the influence of membrane position on the flow in bifurcation as well as of the stent position and shift on the flow in trifurcation. we confirmed that the effect of the stent position on the flow was bigger than that of the area occupied by the stent and that of KBT which moves the stent from the flow peak may be useful. However, it was also suggested that the intimal lining after KBT may cause serious flow inhibition.

Microfluidic systems are becoming common in the development of point-of-care (PoC) diagnostic systems where various methods are used to efficiently separate blood cells from whole blood. The goal of this research is to develop a passive plasma separator that can easily be integrated into an entire blood-based diagnosis microfluidic platform. In the present work, a one-step process of creating a cell-free region in the flow without the plasma being actively extracted from the whole blood is discussed. Centrifugal force together with a backward facing step is utilized to create a blood cell-free zone. Sensors (typically less than 10 micrometers in size) are proposed to be placed in the cell-free zones for biomarker detection. A detailed numerical study for the design of the microfluidic platform is reported. The two-phase nature of the blood is modeled using a discrete element method (DEM) where blood cells are modeled as spherical constituents with the inclusion of inter-particular interactions. The sizes of the cell-free zones in the microfluidic system are measured for various geometric and flow conditions. An expansion chamber with a larger aspect ratio together with a low Reynold number flow entering it is observed to create a larger cell-free zone.

Ventricular assist devices (VAD) are designed to provide circulatory support to patients suffering from advanced-stage heart failure. While not pulsatile, the advantages of continuous axial flow VADs include a compact size and low mechanical failure rate. However, being compact, they operate at high speed, resulting in adverse effects, such as hemolysis caused by high flow shear and thrombosis formation in stagnant regions are common and threaten the successful use of the device. While state-of-the-art computational fluid dynamics (CFD) is widely used in designing these devices, detailed high-resolution experimental measurements of the flow within them are not readily available in the literature. Such experimental data is crucial for understanding the flow inside the VAD and its interaction with blood cells as well as for validating the CFD predictions. The present study investigates the flow inside a 1:1 exact replica of a VAD – ReliantHeart HeartAssist5 ® . This 12mm diameter device consists of an inlet guide vane (IGV), a rotor and a stator. However, unlike in the real machine, the rotor is driven by a thin shaft that penetrates through the center of the IGV. Refractive index-matching is used to facilitate optical measurements. Hence, all the blades and housing of the pump are made of transparent acrylic. The working fluid is a mixture of water, sodium iodide and glycerin, which matches the refractive index of acrylic, and the kinematic viscosity of blood. Performance tests have been carried out at speeds ranging from 7000 to 9000 RPM. Trends of the results are consistent with those of the actual machine. While scaled data for the pressure rise across the rotor at different speeds collapse, the total head rise across the entire machine does not. High-resolution 2D PIV measurements with vector spacing of 30μm have been conducted in meridional planes of the rotor passage at several blade orientations. They have been performed at 8000RPM and flowrate of 4.5L/min, consistent with physiological requirements. They show that near the rotor front end, the flow in the tip region is dominated by the tip leakage vortex (TLV), associated blockage effects, and very high turbulence level. The upstream end of this domain remains aligned with the leading edge, implying that blades persistently dissect the remnants of a previous TLVs. Interaction of the hub boundary layer with the blades also generates secondary flows. Downstream of the helical section of the rotor, the axial flow is high near the hub and low in the outer part of the passage due to leakage flow-related blockage. Hub boundary layer separation occurs upstream of the stator, generating a large circumferential vortex that occupies nearly half of the rotor span. The complexity of the flow structure and turbulence in this machine would be a challenge to model.

The axial blood pump body primarily contains the Inlet Guide Vane (IGV), Rotor Impeller (RI), Outlet Guide Vane (OGV) and pump casing. There must be gaps between rotor blade tip and pump casing or between OGV blade root and rotor hub for the impeller rotating in the pump. The flow characteristics inside an axial blood pump with different blade gaps were numerically simulated and analyzed. Hydraulics experiments were conducted to verify the numerical results. The results show that the pump efficiency decreased slowly when the OGV blade gap increased from 0.1 mm to 0.3 mm, but quickly when the rotor blade gap increased from 0.1 mm to 0.3 mm. The hydraulics characteristic results indicate that the pressure rise and efficiency are mainly influenced by the rotor blade gap. The OGV blade root gaps have little influence on the decrease of pressure rise and efficiency. The novel configuration with uneven blade gaps inside the pump result in improved hydraulics and hemolytic performance compared with the similarly sized configuration with even blade gaps.

Partial-support is the main support mode for “less sick” patients with severe heart failure. But there were fewer partial-support blood pumps for clinical use. An implantable partial-support axial blood pump was developed for heart failure patients. To gain better hemolytic performance and lower pump thrombus risk, the rotor blades were extended to the contractive section of the rotor hub while cone-bearing was adopted. The hydraulic and hemolytic performance of the blood pump was simulated and analyzed by computational fluid dynamics (CFD) method. The flow velocity, hydraulic efficiency, exposure time, scalar shear stress (SSS) and hemolytic performance of the axial blood pump was analyzed. The numerical results showed that the axial blood pump could produce a 1–8 Lpm flow rate with a 54.7–186.7 mmHg pressure head when the pump rotating from 9000 to 13000 rpm. The hydraulic efficiency and SSS distribution corresponded with the typical performance of a blood pump. The mean hemolysis index of the blood pump calculated by the Giersiepen’s model was 5.0 × 10 −5 %. After extending the rotor blades to the contractive section of the rotor hub, the spiral flow at the inlet of the rotor impeller was reduced. Hemolysis in the blood pump was improved because the exposure time was reduced and the blood damage caused by SSS was reduced.. The designed blood pump satisfies the clinical requirements of partial-assist for less-sick heart failure patients.

Recent developments in electrowetting-on-dielectric (EWOD) technology have expanded the possibilities for testing methods and investigation of blood. This work evaluated the development of necking geometry of whole blood on an EWOD-based digital microfluidic (DMF) platform. This was achieved by performing tensile tests on whole blood on an EWOD-based device, thereby inducing necking. A time-invariant method was used to evaluate the deformation of the tested dilutions, using minimum neck width and neck radius as two characteristic parameters of the necking geometry. Experiments were performed on blood diluted with phosphate-buffered saline (PBS) at dilutions of 1:20 and 1:10 by volume. Parameter measurements were obtained by recording microscope video of on-chip tensile tests and extracting the necking profile. Neck radius and neck width are obtained from the extracted necking profile and evaluated to compare results. Results from tensile tests on blood at different dilutions showed an exponential decrease in neck radius as neck width decreases. A four-parameter exponential model was fit to the collected data, showing that the 1:20 dilution had a higher neck radius to neck width ratio than the 1:10 dilution over a neck width interval of 0.3 mm to 1.7 mm, suggesting a viscosity effect on the necking geometry. The results demonstrate that the concentration of blood influences the necking profile when deformed under tension that is applied by electrowetting forces.

Significant research involving the isolation and detection of circulating tumor cells (CTCs) has become prevalent in the field of biomedicine. It plays a crucial role in the diagnosis and treatment of cancer and has made substantial strides in recent years. A major event in the timeline of cancer is metastasis, a set of occurrences where cells are shed from a cancerous site, then flow through the circulatory system and seed themselves throughout the body, forming secondary tumors. There are few observable symptoms in the early stages of metastasis and this fact severely limits clinical treatment. The fabrication and preliminary testing of a magnetophoretic bioseparation chip capable of isolating and detecting CTCs from peripheral blood, which can aid in early detection of metastases, is presented in this work. MCF7 breast cancer cells along with superparamagnetic microparticles, which are specifically coated with anti-EpCAM to bind to the cancer cells, are spiked into a blood sample. After the spiked blood sample is introduced into the biochip, a locally engineered magnetic field gradient captures the magnetically labeled cancer cells while the non-target cells are allowed to pass by. Once the target cells are isolated from the blood sample, flow cytometry is used to determine the recovery rate of the magnetophoretic device. The proposed device can operate at continuous flow rates magnitudes higher than other CTC isolation devices and is fabricated using much simpler methods which make it quite unique. These properties combined with greater than 80% recovery rates make the device quite favorable for economic point of care use in clinical applications.

Hemodynamics plays an important role in the formation of blood clots, for which changes in hydrodynamic stresses and transport phenomena can initiate or inhibit the clotting process. Fibrin, which is converted from fibrinogen in blood plasma, plays a dominant role in structural mechanics of a clot. Clot analogs are conventionally fabricated in a static in vitro environment whereas clot formation in vivo occurs in the presence of dynamic blood flow. In this paper we demonstrate an ability to produce clot analogs at the boundary between active co-flow fluid streams. The time evolution of clot formation in microchannel flow was investigated using fluorescence imaging of fibrin clots at one-minute intervals. Time-tracking of skewness and kurtosis of fluorescence intensity data was conducted to monitor shape and density distribution changes in the clot. Soft lithography and casting techniques were used to fabricate a polydimethylsiloxane (PDMS) microfluidic device which consisted of a Y-shaped microchannel 300 μm wide × 12 μm deep × 10 mm long with two inlets and a single outlet. The first inlet introduced fresh frozen plasma (FFP), which contains fibrinogen and plasma proteins. The second inlet introduced thrombin, which initiated the conversion of fibrinogen to fibrin. Clot analogs were formed at the interface between these two parallel streams. Flow was driven by withdrawal of a syringe pump at flow rates of 50 nL/min and 100 nL/min. Clots that are formed in such an engineered device provide opportunities to recapitulate the flow rates and concentrations of reagents, to mimic in vivo scenarios in which clot density and composition gradients depend on flow conditions.

Wall shear stress (WSS) distribution in stenosed arteries has been known as an important hemodynamic factor to correlate with atherosclerosis and associated disturbances in blood flow. WSS depends on various factors such as geometric complexity and tortuosity of the artery, stenosis severity and morphology as well as blood rheological properties. We conducted a numerical simulation of blood flow using Ansys CFX software in 9 patient-specific coronary artery models with 3 classes of stenosis severity: mild, moderate and severe. For this purpose, we compared some numerical results between two non-Newtonian models and Newtonian blood flow viscosity using 9 patient-specific coronary artery models including the full range of real (physiological) stenosis, reconstructed from 3DQCA (quantities coronary angiography). Incompressible and steady state form of Navier-Stokes equations were used as governing equations. Flow was considered laminar and artery walls were assumed to be rigid. Results showed that the magnitude of WSS usually increases by decreasing the cross-section area of arteries. Despite the difference in the WSS magnitude between different models in each artery, the trend of variation of WSS along the artery was the same in all three models. The local peak point of WSS along the artery occurs at the stenosis location, same for all models.

Hypoplastic Right Heart Syndrome is a type of congenital heart defect where the right ventricle is underdeveloped in an infant to pump blood from the body to the lungs. The three-staged surgical Fontan procedure provides a temporary treatment; however, in most of the cases, a heart transplantation is required due to postoperative complications. Currently, there are no devices commercially available in the market to provide a therapeutic assistance to these patients until a donor heart is available. Thus, a novel dual propeller pump concept is developed to provide cavopulmonary assistance to these patients. The designed blood pump would be percutaneously inserted via the Femoral vein and deployed at the center of the Total Cavopulmonary Connection (TCPC). The two propellers, each placed in the Superior Vena Cava (SVC) and the Inferior Vena Cava (IVC) are connected by a single shaft and rotating at same speed. The device is supported with the help of a self-expanding stent whose outer walls are anchored to the inner walls of the IVC and the SVC. Each of the IVC and the SVC propeller without the stent provides a modest pressure augmentation of 5–6 mm Hg. To expand on this, the current study focusses on studying the effect of the introduction of stent around the propeller on the hemodynamic performance of the pump. Five different stent design parameters, viz. the strut thickness, width, number, the stent length and number of strut columns were selected for a range of values. Each of the design parameters was varied by keeping all others constant and equal to the base stent design. All the stent models were analysed to see their effect on pressure rise, flow pattern and blood damage using 3D CFD analysis. The blood damage potential for different studied designs was predicted using a non-linear mathematical power law model along with Lagrangian particle tracking to predict the blood flow path. The introduction of stent resulted in pressure reduction of around 0.4 and 0.2 mm Hg around the IVC and SVC propeller with an increase in blood damage index (BDI) by almost 2 times for the final dual propeller pump assembly. It was observed that the blood damage potential was directly related to the amount of pressure rise where the stent length, stent column number, strut width, and strut thickness had a converse effect showing a reduction in pressure rise and blood damage with their increment. While the number of struts gave a desirable effect of increasing pressure rise and reducing blood damage with its increment. The study also demonstrated that the introduction of stent around a circulatory pump increases the Wall Shear Stress (WSS) value at the stent-artery wall interface thereby preventing the occurrence of restenosis and thrombosis initiating due to very low WSS (< 0.5 Pa). Thus, this study acts as an initial step to design a protective stent support around a percutaneous assist device by analysing the sensitivity of stent design parameters on the hemodynamic performance of the pump.

The presence of a wall near a rigid sphere is known to disturb the particle fore and aft flow field and thereby affect particle drag and lift. This effect has wide ranging implications in particulate flows such as the dynamics of blood cells in microvessels or the transport of particulates in channel and pipe flows. In this study, an Immersed Boundary Direct Numerical Simulation (IB-DNS) is used to predict the dynamics of a rigid spherical body in the presence of a wall at laminar flows. The wall effect is shown to be significant when the dimensionless ratio (L/D) of the particle diameter (D) to the wall distance (L) is less than 3, and when particle Reynolds number is less than 10. Based on the IB-DNS results, a correlation for the wall effect on drag coefficient is derived that can be used to predict the actual drag coefficient for rigid spheres under the influence of a wall for L/D between 0.75 and 3 and Reynolds number between 0.18 and 10. The data underlying the correlation developed herein is validated by comparison to published experimental, numerical, and analytical correlations. The application of the IB-DNS method to study the wall effect is both novel and significant. It is novel in that such an application is not yet demonstrated. It is significant in that it; (1) utilizes a uniform Cartesian fluid mesh and (2) requires no sub domains of higher grid resolution in the wall gap.

Currently, the surgical procedure followed by the majority of cardiac surgeons to address right ventricular dysfunction is the Fontan procedure, which connects the superior and inferior vena cava directly to the left and right pulmonary arteries bypassing the right atrium. However, this is not the most efficient configuration from a hemodynamics perspective. The goal of this study is to develop a patient-specific 4-way connector to bypass the dysfunctional right ventricle and augment the pulmonary circulation. The 4-way connector is intended to channel the blood flow from the inferior and superior vena cava directly to the right and left pulmonary arteries. By creating a connector with proper hemodynamic characteristics, one can control the jet flow interactions between the inferior and superior vena cava and streamline the flow towards the right and left pulmonary arteries. In this study the focus is on creating a system that can identify the optimal configuration for the 4-way connector for patients from 0–20 years of age. A platform is created in ANSYS that utilizes the DOE function to minimize power-loss and blood damage propensity in the connector based on junction geometries. A CFD model is created to simulate the blood flow through the connector. Then the geometry of the bypass connector is parameterized for DOE process. The selected design parameters include inlet and outlet diameters, radius at the intersection, and length of the connector pathways. The chosen range for each geometric parameter is based on the relative size of the patient’s arteries found in the literature. It was confirmed that as the patient’s age and artery size change, the optimal size and shape of the connector also changes. However, the corner radius did not decrease at the same rate as the opening diameters. This means that creating different sized connectors is not just a matter of scaling the original connector to match the desired opening diameter. However, it was found that power losses within the connector decrease and average and maximum blood traversal time through the connector increased for increasing opening radius. This information could be used to create a more specific relationship between the opening radius and the flow characteristics. So in order to create patient specific connectors, either a new more complicated trend needs to be found or an optimization program would need to be run on each patient’s specific geometry when they need a new connector.