Research lab for flow in biomedical and energy systems
Recent Articles
Some examples of recent published papers (click the graphical abstract for content)
Example Posters
Hydrogen Production On-demand by a Pump Controlled Hydrolysis of Solid Hydride
A new type of hydrogen generator for "on-demand" use with hydrogen-based fuel cells. Hydrogen is produced in a catalytic hydrolysis reaction of sodium borohydride. The proposed generator is lightweight, has high energy density, efficient, portable, easy to use, refill, and clean. The system consists of two main chambers, the upper chamber with sodium powder and the lower reaction chamber with a solution of water and catalyst. A peristaltic pump regulates the flow of water solution through a designated channel in the upper chamber with sodium borohydride and saturated solution drips into the reaction chamber. This system is significantly lighter and requires much less operating energy than other similar generators. To maintain constant H2 flow rate levels, the system controls continually solution temperature and H2 pressure in the reaction chamber. The mechanical and control systems were designed for long working periods and at different conditions, and with capabilities for restarting after prolonged rests. Experiments were carried out to prove system reliability and efficiency to allow commercial applications with a fuel density of 1296Wh/kg. This device has great potential for a variety of military, vehicle, and portable device applications.
Hemodynamic and Clinical Aspects of Treatment Approaches for Aortic Aneurysm
Aortic aneurysm is a pathologic entity defined by a localized dilatation in the aorta. Aneurysms rupture is an unexpected and fatal event. Currently available options for repair include surgical repair, custom endovascular solutions, chimney procedures and off-the-shelf stent-grafts. In our lab we use combined numerical (CFD) experimental (in-vitro) and clinical investigations of the hemodynamic behavior of the aneurysmatic aorta and of the different treatment options to explain clinical complications and suggest improvements in devices designs. The numerical simulations include fluid-structure interaction to account for the stent-graft dynamics. For the experiments we use particle image velocimetry (PIV) technique and a mock circulatory loop (MCL) system to simulate typical circulations conditions.
The impact of Aortic Stenosis on Coronary Blood Flow
Clinical evidences show that patients with severe aortic stenosis (AS) suffer from low coronary flow reserve (CFR) during hyperemia, but show increased coronary blood flow (CBF) during rest conditions. Furthermore, transcatheter aortic valve implantation (TAVI) was shown to decrease rest CBF and increase CFR along with its main purpose of improving the systolic flow. Physiological or pathological factors do not provide a clear explanation for the increase of rest CBF due to AS and its decrease immediately after TAVI. We use combined numerical (CFD) and experimental (in-vitro) methods to explain the hemodynamic mechanism that correlates between AS, vortices location and coronary flow. We also show that CBF is very sensitive to timing, leaflet motion and stroke volume, and thus CFR reduces with HR in AS cases.
The effect of closing approach during carotid endarterectomy
The carotid bifurcation tends to develop atherosclerotic stenoses which might interfere with cerebral blood supply. In cases of arterial blockage, the common clinical solution is to remove the plaque via carotid endarterectomy (CEA) surgery. Artery closure after surgery using primary closures along the cutting edge might lead to artery narrowing and restrict blood flow. An alternative approach uses patch angioplasty takes longer and leads to more during-surgery complications. The present study uses numerical methods with Fluid-Structure Interaction (FSI) to explore and compare the two solutions in terms of hemodynamics, stress and strain fields developed in the artery wall.
A Shear Free System for Measurement of Shear Induced coagulation
For patients recovering from cardiac surgery who need temporal circulatory assist devices, coagulation is a critical for the healing process, however, anticoagulation therapy is needed to avoid massive embolism induced by the circulatory assist device. In order to develop an efficient anti-coagulation therapy, we developed a unique shear-free system, which models physiological flow regimes without any pump or valves. This allows measurement of only the hemodynamic related shear without additional noise. The system is fully controlled, allowing a large variety of shear levels, exposure times, frequencies, number of cycles and more.
The sense of mediation components in the social field among primary school teachers
SEL-Social emotional learning has a dramatic impact on the child in the present and future, such as learning, personal development, mental well-being, relationships and economic success. The effect of intervention programs for the development of social skills within schools was found. Most interventions involve children rather than teachers. However, teachers find it difficult to engage in the social sphere. The focus of this study is on raising teachers' sense of competence in social intervention in primary school. In the study, teachers will be trained in social mediation in primary schools, traditional learning - face-to-face learning, and mixed learning - combining face-to-face learning with ICT. The purpose of the study is to examine the impact of the various training programs (traditional, mixed and unqualified) on the teacher's sense of competence in the social field. The study will examine the effectiveness of training in examining the impact of knowledge - social skills, and the tools to implement - the components of mediation, on the sense of competence of teachers.
Blood Hemodynamics in Hypertrophic Obstructive Cardiomyopathy
Hypertrophic Obstructive Cardiomyopathy (HOCM) is a common complication of Hypertrophic Cardiomyopathy characterized by obstructive motion of the anterior mitral leaflet causing mitral regurgitation, compromising systolic left ventricular (LV) reduced ejection fraction, and significant outflow pressure gradients (>30mmHg). Some patients who are unresponsive to medication are prone to highly invasive surgery, including myectomy or ablation, with relatively high mortality and morbidity rates. In this research we study the blood flow in LV using computational fluid dynamics (CFD) methods, and predict blood hemodynamics in healthy, pathological and treated LV cases.
New flow system for compliance testing of collagen fibers reinforced bio-composites for small-diameter tissue engineered blood vessels
This study introduces a novel experimental system that allows testing the mechanical properties of a large variety of vessels. We used it to test our collagen fibers reinforced bio-composites for small-diameter tissue engineered blood vessels.
These new bio-composites were proven to be biocompatible and their tensile behavior was found to be similar to the reported native tissue properties. The system includes pulse generation and measurements of flow pressures and wall displacement in the tested tubes.
We use optical methods (using light reflection amplifier) and differential pressure gauges for the measurements of delay between tube's entrance and exit to calculate wave propagation rate.
Experimental Evaluation of an LVAD Performance as a Function of Impeller Design
A novel percutaneous Left Ventricular Assist Device based on an axial impeller is designed to treat patients with acute heart failure. The novel design is intended to reduce known complications of the assist device, including blood damage and thrombus formation due to contact of blood with the impeller's blades and the non-physiological flow field due to the high rotational speed of the impeller. The suggested design is based on increasing the impeller's inlet-to-outlet area ratio and thus improve pump performance and reducing the rotational speed required for sufficient flow and pressure conditions.
In this study, we designed and built an enlarged experimental system (based on the similitude principle) to evaluate the pump performance as a function of the impeller's inlet-to-outlet area ratio. The system measures flow rate, pressure head, and motor rotation speed for different system loads. To investigate the effect of inlet-to-outlet area ratio, five different impeller designs were examined with different hub configurations. Each design was tested at 24 varying load resistance and rotational speeds.
Results show improvement of pump performance and reduction of rotation speed for impellers with a larger inlet-to-outlet area ratio.
Characterization of swirling flow patterns in the presence of LVAD
A percutaneous left ventricular assist device (pLVAD) is a mechanical pump that is implanted in patients with heart failure. The jet emerges from the pLVAD may have a significant effect on the flow downstream of the aorta. Better understanding of the effect of pLVAD jet on the helical flow- the 3D corkscrew motion in the aorta can lead to an improved design. The 2D value of vorticity, is an indicator of the amount of helical flow. This research focused on the question: How does the swirling jet emerging from a pLVAD affect the helical flow of the aorta?
The method we used to visualize the flow is particle image velocimetry (PIV). Fluorescent particles are injected and illuminated by a laser light sheet. A high-rate sequence of images is captured, and the displacement of a particle between each set of images is converted to velocity using the time between shots and the physical size of the displacement interval.
Two variables contributing to swirling flow are identified- curved tubing and swirling jet, to understand the impact of each of the variables, they were studied separately. The cases studied thus include; straight tube system with a straight jet (Pushing LVAD), curved aorta system with a straight jet (Pushing LVAD) and straight tube system with a swirling jet (Suction LVAD).
In conclusion, the flow regime in the aorta with the presence of a LVAD can be visualized using the PIV technique, and the setup proposed in this project. The results show an effect of the LVAD jet on the flow regime, both in the structure of the secondary flow and in the values of the vorticity. By comparing between the aorta model to a straight tube, a stronger effect can be found due to the geometry of the model, than of the jet structure. Also, higher flow rates increase the vorticity value and cause larger vortices.
Models for controlling Traffic Flow of Autonomous Vehicles
This research’s main issue is the traffic flow of connected Autonomous Vehicles (AVs) in the futuristic world where the road is occupied by AVs alone.
We Assume the AV’s sensory data is of better quality and react faster than humans, and further assume that they would communicate with each other, or communicate with and comply to a central control system. In this research we identify an effective traffic flow model to describe such a flow and utilize its benefits for developing optimized algorithms (in several senses) to control traffic flow in different road configurations and conditions.
Hemodynamical Study of the Flow over a Ventricle Assist Device Impeller
Purpose: Mechanical circulatory support devices have improved the management, survival and prognosis of many patients with Acute or Chronic Heart Failure. However, there is still high mortality and a wide burden of disease, mostly due to related thrombosis and embolization, thus requiring anticoagulation. Most of the currently approved ventricle assist devices (VADs) operate far beyond the critical threshold for biological damage, which aggravates the condition of the patient. The need for VADs that minimized blood damage is critical. In this study, we examine the effect of impeller design on functionally and hemodynamic using numerical models.
Methods: Need a bit more here. Steady and transient numerical simulations of a rotating frame using ANSYS CFX were developed. The simulations were utilized to estimate the shear stress, regions of stasis and global pump performance such as flow rate, pressure head and power. The level of platelet activation was estimated along trajectories pathlines. An experimental system was used to validate the performance results, and PIV visualization techniques were used to validate flow patterns downstream of the impeller.
Results: Good agreement was found between the numerical model and the experiments. The results imply that the numerical models have the potential of predicting both hemodynamic and thromboembolism characteristics. All results indicate that the larger hub diameter showed better pump and better hemodynamical performance, with smaller regions of high shear stress and regions of stagnations. Understanding the impact of the geometry on the pump performances and blood damage may provide the ability to optimize VADs design.
