Engineering Commons^™

Considering The Influence Of Coronary Motion On Artery‑Specific Biomechanics Using Fluid–Structure Interaction Simulation, Nicholas A. T. Fogell, Miten Patel, Pan Yang, Roosje M. Ruis, David B. Garcia, Jarka Naser, Fotios Savvopoulos, Clint Davies Taylor, Anouk L. Post, Ryan M. Pedrigi, Ranil De Silva, Rob Krams

Department of Mechanical and Materials Engineering: Faculty Publications

The endothelium in the coronary arteries is subject to wall shear stress and vessel wall strain, which influences the biology of the arterial wall. This study presents vessel-specific fluid–structure interaction (FSI) models of three coronary arteries, using directly measured experimental geometries and boundary conditions. FSI models are used to provide a more physiologically complete representation of vessel biomechanics, and have been extended to include coronary bending to investigate its effect on shear and strain. FSI both without- and with-bending resulted in significant changes in all computed shear stress metrics compared to CFD (p = 0.0001). Inclusion of bending within …

Numerical Study Of Sediment Suspension Affected By Rigid Cylinders Under Unidirectional And Combined Wave-Current Flows, Sha Lou, Xiaolan Chen, Shengyu Zhou, Gangfeng Ma, Shuguang Liu, Larisa Dorzhievna Radnaeva, Elena Nikitina, Irina Viktorovna Fedorova

Civil & Environmental Engineering Faculty Publications

Sediment transport modeling for flows with cylinders is very challenging owing to the complicated flow–cylinder–sediment interactions, especially under the combined wave-current flows. In this paper, an improved formulation for incipient sediment suspension considering the effect of cylinder density (i.e., solid volume fraction) is employed to simulate the bottom sediment flux in the flow with cylinders. The proposed model is calibrated and validated using laboratory measurements under unidirectional and combined wave-current flows in previous studies. It is proved that the effects of cylinders on sediment suspension can be accounted for through a modified critical Shields number, and the proposed model is …

Observations Of Shear Stress Effects On Staphylococcus Aureus Biofilm Formation, Erica Sherman, Kenneth W. Bayles, Derek Moormeir, Jennifer Endres, Timothy Wei

Department of Mechanical and Materials Engineering: Faculty Publications

Staphylococcus aureus bacteria form biofilms and distinctive microcolony or “tower” structures that facilitate their ability to tolerate antibiotic treatment and to spread within the human body. The formation of microcolonies, which break off, get carried downstream, and serve to initiate biofilms in other parts of the body, is of particular interest here. It is known that flow conditions play a role in the development, dispersion, and propagation of biofilms in general. The influence of flow on microcolony formation and, ultimately, what factors lead to microcolony development are, however, not well understood. The hypothesis being examined is that microcolony structures form …

Evaluating The Effect Of Shear Stress On Graft-To Zwitterionic Polycarboxybetaine Coating Stability Using A Flow Cell, Andrew Belanger, Andre Decarmine, Shaoyi Jiang, Keith Cook, Kagya Amoako

Mechanical and Industrial Engineering Faculty Publications

The effect of surface coatings on the performance of antifouling activity under flow can be influenced by the flow/coating interactions. This study evaluates the effect of surface coatings on antifouling activity under different flows for the analyses of coating stability. This was done by exposing DOPA-PCB-300/dopamine coated polydimethylsiloxane (PDMS) to physiological shear stresses using a recirculation system which consisted of dual chamber acrylic flow cells, tygon tubing, flow probe and meter, and perfusion pumps. The effect of shear stress induced by phosphate buffered saline flow on coating stability was characterized with differences in fibrinogen adsorption between control (coated PDMS not …

Disturbed Cyclical Stretch Of Endothelial Cells Promotes Nuclear Expression Of The Pro-Atherogenic Transcription Factor Nf-Kb, Ryan M. Pedrigi, Konstantinos I. Papadimitriou, Avinash Kondiboyina, Sukhjinder Sidhu, James Chau, Miten B. Patel, Daniel C. Baeriswyl, Emmanuel M. Drakakis, Rob Krams

Department of Mechanical and Materials Engineering: Faculty Publications

Exposure of endothelial cells to low and multidirectional blood flow is known to promote a pro-atherogenic phenotype. The mechanics of the vessel wall is another important mechano-stimulus within the endothelial cell environment, but no study has examined whether changes in the magnitude and direction of cell stretch can be pro-atherogenic. Herein, we developed a custom cell stretching device to replicate the in vivo stretch environment of the endothelial cell and examined whether low and multidirectional stretch promote nuclear translocation of NF-kB. A fluid–structure interaction model of the device demonstrated a nearly uniform strain within the region of cell attachment and …

Exact Solution For Viscous Fluid Flow In Porous Medium With Magnetic Field, Dinesh P. A., Jayalakshmamma D.V., Chandrashekhar D.V.

Sixth International Conference on Porous Media and Its Applications in Science, Engineering and Industry

The steady flow of viscous, incompressible, conducting fluid flow past a spherical solid core embedded in another spherical porous medium is considered. The exact solution is obtained for the flow in the presence of transverse magnetic field. The considered fluid flow is governed by Brinkman equation in porous region and by Stokes equation in the fluid region with additional Lorentz’s force due to applied magnetic field. The flows in the two regions are matched across the interface by assuming continuity of velocity and stress across the interface. Further, no-slip condition at the solid surface and uniform velocity far from the …

Bhk Cells Physiological Response To Spin-Filter Stress Condition, Bruno Labate, Aldo Tonso

Integrated Continuous Biomanufacturing II

Mammalian cells are the preferable platform for secreted pharmaceutical proteins due to the compatibility of posttranslational modifications performed by these cells with therapeutic applications. However, to obtain a desirable quantity of these proteins, high cell concentrations are also needed. Baby hamster kidney BHK-21/C13 cells, adapted to single-cell suspension culture growth were cultivated in batch mode in a Biostat B (Sartorius AG, Germany) bioreactor with a 1,5 L working volume vessel. The temperature was controlled at 37 ºC, pH at 7.2 with CO­₂, agitation at 80 rpm and dissolved oxygen at 50% of air saturation. The culture medium used …

Stratification Of A Population Of Intracranial Aneurysms Using Blood Flow Metrics., Rohini Retarekar, Manasi Ramachandran, Benjamin Berkowitz, Robert E. Harbaugh, David Hasan, Robert H. Rosenwasswer, Christopher S. Ogilvy, Madhavan L. Raghavan

Department of Neurosurgery Faculty Papers

Indices of the intra-aneurysm hemodynamic environment have been proposed as potentially indicative of their longitudinal outcome. To be useful, the indices need to be used to stratify large study populations and tested against known outcomes. The first objective was to compile the diverse hemodynamic indices reported in the literature. Furthermore, as morphology is often the only patient-specific information available in large population studies, the second objective was to assess how the ranking of aneurysms in a population is affected by the use of steady flow simulation as an approximation to pulsatile flow simulation, even though the former is clearly non-physiological. …

Analytical Modeling Of The Interface Between Lightly Roughened Hollowcore Slabs And Cast-In-Place Concrete Topping, Aiham Adawi, Maged A. Youssef, Mohamed E. Meshaly

Civil and Environmental Engineering Publications

Hollowcore slabs are commonly used in different types of structures. They are usually topped with a 50 mm concrete topping. Structural engineers can use this topping to increase the slab load carrying capacity. North American design standards relate the horizontal shear strength at the interface between hollowcore slabs and the concrete topping to the slab surface roughness. This paper presents results of four push-off tests on hollowcore slabs supplied by two manufacturers and roughened using a conventional steel broom. The tested slabs sustained higher horizontal shear stresses than those specified by the design standards. Utilizing the data from the push-off …

Experimental Investigation Of The Composite Action Between Hollowcore Slabs With Machine Cast Finish And Concrete Topping, Aiham Adawi, Maged Youssef, Mohamed E. Meshaly

Civil and Environmental Engineering Publications

Hollowcore slabs are precast/prestressed concrete elements produced at a manufacturing plant before shipping to the job site. Following installation, a layer of concrete topping is usually cast to connect the slabs and to have a level surface. According to current North American design standards, the topping should not be considered to act compositely with the slabs except if their surface satisfies a strict roughness requirement. This paper evaluates if such restriction is justified for hollowcore slabs with machine-cast finish through an experimental program that involves pull-off, push-off and full-scale tests. The surface roughness was first evaluated. The peel (bond) and …

Inducing Persistent Flow Disturbances Accelerates Atherogenesis And Promotes Thin Cap Fibroatheroma Development In D374y-Pcsk9 Hypercholesterolemic Minipigs, Ryan M. Pedrigi, Christian Bo Poulsen, Vikram V. Mehta, Niels Ramsing Holm, Nilesh Pareek, Anouk L. Post, Ismail Dogu Kilic, Winston A.S. Banya, Gianni Dall'ara, Alessio Mattesini, Martin M. Bjorklund, Niels P. Andersen, Anna K. Grondal, Enrico Petretto, Nicolas Foin, Justin E. Davies, Carlo Di Mario, Jacob Fog Bentzon, Hans Erik Botker, Erling Falk, Rob Krams, Ranil De Silva

Department of Mechanical and Materials Engineering: Faculty Publications

Background—Although disturbed flow is thought to play a central role in the development of advanced coronary atherosclerotic plaques, no causal relationship has been established. We evaluated whether inducing disturbed flow would cause the development of advanced coronary plaques, including thin cap fibroatheroma (TCFA).

Methods and Results—D374Y-PCSK9 hypercholesterolemic minipigs (N=5) were instrumented with an intracoronary shear-modifying stent (SMS). Frequency-domain optical coherence tomography was obtained at baseline, immediately post-stent, 19, and 34 weeks and used to compute shear stress metrics of disturbed flow. At 34 weeks, plaque type was assessed within serially-collected histological sections and co-registered to …

Experimental Assessment Of The Impact Of Asymptomatic Gas Emboli On The Vessel Wall, Linxia Gu, Eric L. Cutler

Department of Mechanical and Materials Engineering: Faculty Publications

Quantitative evaluation of shear stress in the vessel wall due to the presence of asymptomatic gas emboli is lacking. The goal of this work was to assess the impact of chronic asymptomatic gas emboli on the risk of atherosclerosis through a custom-built cardiovascular flow simulator. Gas bubbles were created by forced air from a syringe pump. The influences of embolism injection rate, pulse rate, and time-averaged flow rate on the wall mean shear stress were investigated at resting and elevated heart rate conditions. The recorded pressure and volumetric flow rate from 24 experimental settings with four repetitions each were used …

Systems Biology Of The Functional And Dysfunctional Endothelium, Jennifer Frueh, Nataly Maimari, Takayuki Homma, Sandra M. Bovens, Ryan M. Pedrigi, Leila Towhidi, Rob Krams

Department of Mechanical and Materials Engineering: Faculty Publications

This review provides an overview of the effect of blood flow on endothelial cell (EC) signalling pathways, applying microarray technologies to cultured cells, and in vivo studies of normal and atherosclerotic animals. It is found that in cultured ECs, 5–10% of genes are up- or down-regulated in response to fluid flow, whereas only 3–6% of genes are regulated by varying levels of fluid flow. Of all genes, 90%are regulated by the steady part of fluid flow and 10% by pulsatile components. The associated gene profiles show high variability from experiment to experiment depending on experimental conditions, and importantly, the bioinformatical …

Including Aortic Valve Morphology In Computational Fluid Dynamics Simulations: Initial Findings And Application To Aortic Coarctation, David C. Wendell, Margaret M. Samyn, Joseph Richard Cava, Laura M. Ellwein, Mary M. Krolikowski, Kimberly L. Gandy, Andrew N. Pelech, Shawn C. Shadden, John F. Ladisa

Biomedical Engineering Faculty Research and Publications

Computational fluid dynamics (CFD) simulations quantifying thoracic aortic flow patterns have not included disturbances from the aortic valve (AoV). 80% of patients with aortic coarctation (CoA) have a bicuspid aortic valve (BAV) which may cause adverse flow patterns contributing to morbidity. Our objectives were to develop a method to account for the AoV in CFD simulations, and quantify its impact on local hemodynamics. The method developed facilitates segmentation of the AoV, spatiotemporal interpolation of segments, and anatomic positioning of segments at the CFD model inlet. The AoV was included in CFD model examples of a normal (tricuspid AoV) and a …

Gas Embolic Factors In Cardiovascular Health, Eric L. Cutler

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

Gas emboli are a clinical issue often encountered in the space exploration, marine construction, and medical fields. Individuals involved with these disciplines will often have asympomatic gas emboli circulating throughout their bodies on a regular basis. A study into the impact of chronic asymptomatic gas emboli on the risk of atherosclerosis in humans is thus presented. This research utilized a custom built cardiovascular flow simulator and accompanying data acquisition system to experimentally determine the influence of gas emboli under varied circumstances on the mean wall shear stress of a tube in-vitro. A directly inverse relationship between gas embolus presence in …

Local Hemodynamic Changes Caused By Main Branch Stent Implantation And Subsequent Side Branch Balloon Angioplasty In A Representative Coronary Bifurcation, Andrew R. Williams, Bon-Kwon Koo, Timothy J. Gundert, Peter J. Fitzgerald, John F. Ladisa Jr.

Biomedical Engineering Faculty Research and Publications

Abnormal blood flow patterns promoting inflammation, cellular proliferation, and thrombosis may be established by local changes in vessel geometry after stent implantation in bifurcation lesions. Our objective was to quantify altered hemodynamics due to main vessel (MV) stenting and subsequent virtual side branch (SB) angioplasty in a coronary bifurcation by using computational fluid dynamics (CFD) analysis. CFD models were generated from representative vascular dimensions and intravascular ultrasound images. Time-averaged wall shear stress (TAWSS), oscillatory shear index (OSI), and fractional flow reserve (FFR) were quantified. None of the luminal surface was exposed to low TAWSS (/cm2) in the nondiseased bifurcation model. …

Solids Flow Mapping In A High Pressure Slurry Bubble Column, Novica Rados, Ashfaq Shaikh, Muthanna H. Al-Dahhan

Chemical and Biochemical Engineering Faculty Research & Creative Works

Successful Design and Scale-Up of Slurry Bubble Column Reactors (SBCRs) Require Proper Understanding of How Operating Conditions Affect their Flow Behavior. Presently, there is Little Information on the Flow Dynamics of Solids (E.g., Distribution of Velocities and Turbulent Parameters) in Slurry Systems that Are Operated at Industrially Relevant Conditions of High Pressure, High Superficial Gas Velocities, and High Solids Loading. Computer Automated Radio Particle Tracking (CARPT) is Widely Recognized as One of a Few Techniques that Can Be Reliably Used Even in Highly Turbulent and Opaque Slurry Flows. This Work Utilizes an Improved CARPT Technique to Investigate the Effect of …

Shear Stress In Smooth Rectangular Open-Channel Flows, Junke Guo, Pierre Y. Julien

Department of Civil and Environmental Engineering: Faculty Publications

The average bed and sidewall shear stresses in smooth rectangular open-channel flows are determined after solving the continuity and momentum equations. The analysis shows that the shear stresses are function of three components: (1) gravitational; (2) secondary flows; and (3) interfacial shear stress. An analytical solution in terms of series expansion is obtained for the case of constant eddy viscosity without secondary currents. In comparison with laboratory measurements, it slightly overestimates the average bed shear stress measurements but underestimates the average sidewall shear stress by 17% when the width–depth ratio becomes large. A second approximation is formulated after introducing two …

Comparative Hydrodynamics Study In A Bubble Column Using Computer-Automated Radioactive Particle Tracking (Carpt)/Computed Tomography (Ct) And Particle Image Velocimetry (Piv), Jinwen Chen, Abdenour Kemoun, Muthanna H. Al-Dahhan, Milorad P. Duduković, D. J. Lee, Liang Shih Fan

Chemical and Biochemical Engineering Faculty Research & Creative Works

The Hydrodynamics of a 10-Cm-Diameter Cylindrical Bubble Column at the Superficial Gas Velocity of 2, 4, and 8 Cm/s Are Investigated by Computer-Automated Radioactive Particle Tracking (CARPT), Particle Image Velocimetry (PIV), and Computed Tomography (CT). These Experimental Techniques Are Capable of Providing the Knowledge of Velocity and Holdup Fields in a Bubble Column System, Which Are Essential as the Experimental Benchmark for Modeling of Such Systems. the Flow Field of Liquid Phase, as Well as the Reynolds Stresses, Obtained by CARPT and PIV in an Air-Water System Are Compared in Detail. the Results Indicate that CARPT and PIV Complement Each …

Distributions Of Strain Components And Work Within Flexible Pavement Structures, Herbert F. Southgate, Robert C. Deen

Kentucky Transportation Center Research Report

An investigation was made to determine the location along the centerline of the axle of the maximum strain energy density, or work, in the pavement as defined by classical physics. The location is under the inside edge of either dual tire. The most influential strain was the shear component. The distribution of shear strains and stresses with depth through the full-depth asphaltic concrete and into the subgrade was investigated. Using Simpson's rule for an even number of increments, or using the trapezoidal rule, allows the summation of strain energy density calculated at various depths. This sum multiplied by a unit …