Fluid-structure Interaction Study Research Articles

A fluid–structure interaction study to analyze the severity of carotid artery stenosis at different locations and its effect on various hemodynamic biomarkers

The study on arterial stenosis has gained rapid interest among researchers in the last decade because of its chronic consequences. Several researchers have tried to investigate stenosis and plaque progression in the carotid artery with different simulation models. In this study, a realistic 3-D geometry of the carotid artery has been used to analyze the effect of varying degrees of stenosis present at different locations of the carotid artery on various hemodynamic parameters. An extensive range of stenosis degrees, starting from a healthy artery(0 %stenosis) to 10%, 30%, 50%, 75%, and 90% stenosis, have been studied. These degrees of stenosis were planted at different locations of the artery grown simultaneously. The whole study was done under the realm of Fluid–Structure Interaction multiphysics. The change in velocity profiles at the areas of stenosis has been found along with the wall shear stress and arterial displacement. The magnitude of velocity and wall shear stress in the case of multiple stenosis locations has been found to be dependent on each other. The presence or absence of one stenosis affects the other, and given the regular and irregular patterns of the velocity profile, wall shear stress, and displacement, their inclusion in blood flow simulation studies having multiple stenoses should be considered.

Threshold of Keulegan–Carpenter instability within a 6 × 6 rod bundle

The literature is rich in fluid–structure interaction studies of a single rod in oscillating fluid (or the reciprocate), however, there is a dearth of experimental data for rod bundle oscillation, particularly if the bundle is in a confined environment. The presence of the fluid surrounding the moving solid is modeled with force coefficients such as inertial and drag. In case of small amplitudes oscillating flow, these force coefficients depend non-linearly on the Keulegan–Carpenter number KC. The dependence present different regimes, separated by threshold KC numbers. At different regimes correspond different fluid dynamics, hence different different force coefficients. The aim of this paper is to experimentally investigate the fluid dynamic for a rod bundle oscillating in a stagnant fluid. The velocity fields have been measured with Particle Image Velocimetry (PIV). Both the rod bundle and the fluid have the same refractive index, which allow to measure the velocity fields within the rod bundle in an non intrusive manner. The bundle is hosted in a double tank, immersed in a refractive index matched solution and placed on an earthquake shake table. The shake table sets the bundle into motion along a single direction.Data enable the identification of a threshold effect in the fluid response to the oscillating assembly. This threshold effect is due to the formation of vortexes in the fluid. Data show a clear trend on how the development of turbulence occurs firstly inside the rod assembly and then in the bypass between the assembly and the tank wall. The experimental results indicate the presence of a viscous boundary layer developed along the rod, above the threshold KC. The results presented in this paper represent a step forward the comprehension of the damping effect induced by the fluid at different oscillating amplitudes and frequencies, due to different KC regimes.

Impact of palatopharyngeal sizes changing on pharyngeal airflow fluctuation and airway vibration in a pediatric airway

Snoring is common in children and is associated with many adverse consequences. One must study the relationships between pharyngeal morphology and snoring physics to understand snoring progression. Although some model studies have provided fluid–structure interaction dynamic descriptions for the correlation between airway size and snoring physics, the descriptions still need to be further investigated in patient-specific airway models. Fluid-structure interaction studies using patient-specific airway structures complement the above model studies. Based on reported cephalometric measurement methods, this study quantified and preset the size of the palatopharynx airway in a patient-specific airway and investigated how the palatopharynx size affects the pharyngeal airflow fluctuation, soft palate vibration, and glossopharynx vibration with the help of a verified FSI method. The results showed that the stenosis anterior airway of the soft palate increased airway resistance and airway resistance fluctuations, which can lead to increased sleep effort and frequent snoring. Widening of the anterior airway can reduce airflow resistance and avoid obstructing the anterior airway by the soft palate vibration. The pharyngeal airflow resistance, mouth inflow proportion, and soft palate apex displacement have components at the same frequencies in all airway models, and the glossopharynx vibration and instantaneous inflow rate have components at the same frequencies, too. The mechanism of this same frequency fluctuation phenomenon can be explained by the fluid–structure interaction dynamics of an ideal coupled model consisting of a flexible plate model and a collapsible tube model. The results of this study demonstrate the potential of FSI in studying snoring physics and clarify to some degree the mechanism of airway morphology affecting airway vibration physics.

Prediction of performance parameters of a hermetic reciprocating compressor applying an artificial neural network

The efficiency of the compressor's thermodynamic, mechanical, and electric motors can be increased by minimizing their losses. Based on the design characteristics of the compressor, the current study proposes an artificial neural network (ANN) model to forecast the mass flow rate, cooling capacity, compression power, and discharge line loss of the hermetic reciprocating compressor as outputs. This study uses experimental and numerical results obtained by the fluid–structure interaction (FSI) method, and the whole findings are used as inputs for the machine learning method. Using 36 numerical and 3 experimental data sets, a multilayer network is created with input parameters defining mass flow rate, cooling capacity, compression power, and discharge line energy loss. The input parameters for the network model are the compressor's design parameters, which include the compressor speed, discharge valve thickness, and discharge valve length. When comparing the experimental and FSI methods for compressor speeds of 1300, 2100, and 3000 rpm, the FSI study's mass flow rate and cooling capacity parameters converged at 11.9%, 9.1%, and 9.3%, respectively, to their actual values. The convergence rate to experimental compression power data was −0.3%, 2.6%, and 11%. The numerical-experimental deviation for discharge line energy losses is 14.9%, −3.6%, and 7.8%, respectively, for 1300, 2100, and 3000 rpm. With the Levenberg–Marquardt (LM) ANN model, which is used in this study, the average squared error value is calculated as 1.75E-02 and the R2 value is calculated as 0.99976. ANN model can predict outputs with average deviation rates of less than 0.88%. It is seen that results obtained with the ANN method provide high convergence on the experimental and FSI results, while the results obtained with the regression model deviate from the compressor exhaust line results by more than ±20%, and the ANN method is more successful than regression.

Hemodynamics in arterial bypass graft anastomoses with varying cuff sizes and proximal flow paths: a fluid–structure interaction study

This article investigates the effect of the cuff size of arterial bypass grafts and the flow conditions on the hemodynamics in the anastomosis (connection) to the artery, using numerical simulations. We consider a fluid-structure interaction problem which is solved based on a partitioned scheme. Additionally, we employ computational fluid dynamics to investigate the effect of a rigid wall assumption. The work focuses on clinically relevant hemodynamic quantities associated with the development of intimal hyperplasia. We also include a model for the prediction of hemolysis into the simulation. The results show that even minor changes of the cuff size can result into significant differences in the corresponding quantities of interest. The importance of the inflow path is shown to be lower than that of the cuff size. The usually employed rigid wall assumption is found to be adequate to address wall shear stress oscillations but falls short on predicting maximum and minimum wall shear stress-related quantities of interest.

Fluid-structure interaction study on the causes of mending material damage after sigmoid sinus wall reconstruction

Background and objectiveSigmoid Sinus (SS) Wall Reconstruction (SSWR) is the mainstream treatment for pulsatile tinnitus (PT), but it has a high risk of recurrence. The damage of mending material is the key cause of recurrence, and its hemodynamic mechanism is still unclear. The purpose of this study was to investigate the hemodynamic causes of mending material breakage. MethodsIn this study, six patient-specific geometric models were reconstructed based on the data of the computed tomography angiography (CTA). The transient fluid-structure coupling method was performed to clarify the hemodynamic state of sigmoid sinus and the biomechanical state of the mending material. The distribution of stress and displacement and the flow pattern were calculated to evaluate the hemodynamic and biomechanics difference at the mending material area. ResultsThe area of blood flow impact in some patients (2/6) was consistent with the damaged location of the mending material. The average stress (6/6) and average displacement (6/6) of damaged mending material were higher than those of complete mending material. All (6/6) patients showed that the high-stress and high-displacement proportion of the DMM region was higher than that of the CMM region. Moreover, the average stress fluctuation (6/6) and average displacement (6/6) fluctuation degree of damaged mending material is larger than that of complete mending material. ConclusionsThe impact of blood and the uneven stress and displacement fluctuation of the mending material may be the causes of mending material damage. High stress and high displacement might be the key causes of the mending material damage.

Farklı Isı ve Basınç Koşulları Altında Düz Bir Boru İçin Tek Yönlü Akışkan-Yapı Etkileşimleri Analizi

Numerical studies on stress, deformation, and damages due to fluid flow have been highly carried out using Fluid-Structure Interaction (FSI) in recent years. FSI is highly efficient in investigating a solid domain deformed by the fluid flow. In this study, a one-way fluid-structure interaction study is performed by a straight pipe under different pressure and thermal conditions. Here, the thermophysical properties of the fluid and mechanical properties of the solid domain can be subjected to change during fluid flow. An aluminum straight pipe with a 1 mm wall thickness is operated under 1 Bar, 5 Bar, and 10 Bar with three different surface temperatures -10ºC, 20ºC, and 50ºC. This study aims to investigate the structural variation of aluminum by the temperature and pressure change of operating fluid in the pipe. Variation of thermophysical properties of fluid by heated pipe surface is integrated into the numerical analysis by generated functions. Numerical analysis showed that the variation of temperature in operating fluid highly affects the fluid characteristic and the structural response of the solid domain by different temperatures. An increase in the operating pressure caused maximum deformation to approximately %100 from 1 Bar to 5 Bar, and approximately %120 from 1 Bar to 10 Bar for the adiabatic process as expected but in the heating conditions stress is nearly three times higher than cooling conditions. As a result, one-way FSI solutions are highly effective in investigating the deformed solid domain as a result of flow, thermal, and operating conditions.

Multi-perspective structural integrity-based computational investigations on airframe of Gyrodyne-configured multi-rotor UAV through coupled CFD and FEA approaches for various lightweight sandwich composites and alloys

Abstract As this unmanned aerial vehicle (UAV) has a planned airframe that can carry a 25 kg payload, understanding its structural capabilities, such as its compressive and tensile strengths under different situations, is essential. For the purpose of comprehending the fluid–structure interaction (FSI) of the fuselage, this study designs and analyses the lightweight materials used in the airframe of a complex Gyrodyne UAV. A computer model of a composite airframe for a Gyrodyne UAV is built to examine its durability. An essential factor in the aircraft business is minimizing unnecessary weight, and this FSI study emphasizes the importance of sandwiches and their hybrid combinations in this regard. After the material finalization, around 140 material combinations are tested using an advanced computational composite platform, in which four different lightweight material families are implemented. The fluid load (pressure) is imported into ANSYS workbench 17.2, and the structural airframe is then solved according to the boundary conditions of the application domain. Also, experimental experiments using the high-speed jet facility are run to verify computational improvements. Materials for the airframe of the Gyrodyne UAV have been narrowed down to a final list of contenders. As the work focuses on the FSI analysis, not much computational fluid dynamics (CFD) results were discussed here. Only the imported pressure from the CFD analysis was imposed on to the Gyrodyne UAV to proceed for the FSI analysis.

Altered blood flow due to larger aortic diameters in patients with transcatheter heart valve thrombosis.

The etiology of transcatheter heart valve thrombosis (THVT) and the relevance of the aortic root geometry on the occurrence of THVT are largely unknown. The first aim of this pilot study is to identify differences in aortic root geometry between THVT patients and patients without THVT after transcatheter aortic valve implantation (TAVI). Second, we aim to investigate how the observed difference in aortic diameters affects the aortic flow using idealized computational geometric models. Aortic dimension was assessed using pre-TAVI multi-detector computed tomography scans of eight patients with clinical apparent THVT and 16 unaffected patients (two for each THVT patient with same valve type and size) from the Bern-TAVI registry. Among patients with THVT the right coronary artery height was lower (-40%), and sinotubular junction (STJ) and ascending aorta (AAo) diameters tended to be larger (9% and 14%, respectively) compared to the unaffected patients. Fluid-structure interaction (FSI) in two idealized aortic models with the observed differences in STJ and AAo diameter showed higher backflow rate at the STJ (+16%), lower velocity magnitudes in the sinus (-5%), and higher systolic turbulent dissipation rate in the AAo (+8%) in the model with larger STJ and AAo diameters. This pilot study suggests a direct effect of the aortic dimensions on clinically apparent THVT. The FSI study indicates that larger STJ and AAo diameters potentially favor thrombus formation by increased backflow rate and reduced wash-out efficiency of the sinus. The reported observations require clinical validation but could potentially help identifying patients at risk for THVT.

Biomechanical Evaluation of Aortic Valve Stenosis by Means of a Virtual Stress Test: A Fluid-Structure Interaction Study.

The impact of aortic valve stenosis (AS) extends beyond the vicinity of the narrowed leaflets into the left ventricle (LV) and into the systemic vasculature because of highly unpredictable valve behavior and complex blood flow in the ascending aorta that can be attributed to the strong interaction between the narrowed cusps and the ejected blood. These effects can become exacerbated during exercise and may have implications for disease progression, accurate diagnosis, and timing of intervention. In this 3-D patient-specific study, we employ strongly coupled fluid-structure interaction (FSI) modeling to perform a comprehensive biomechanical evaluation of systolic ejection dynamics in a stenosed aortic valve (AV) during increasing LV contraction. Our model predictions reveal that the heterogeneous ∆P vs. Q relationship that was observed in our previous clinical study can be attributed to a non-linear increase (by ~ 1.5-fold) in aortic valve area as LV heart rate increases from 70 to 115bpm. Furthermore, our results show that even for a moderately stenotic valve, increased LV contraction during exercise can lead to high-velocity flow turbulence (Re = 11,700) in the aorta similar to that encountered with a severely stenotic valve (Re ~ 10,000), with concomitant greater viscous loss (~3-fold increase) and elevated wall stress in the ascending aorta. Our FSI predictions also reveal that individual valve cusps undergo distinct and highly non-linear increases (>100%) in stress during exercise, potentially contributing to progressive calcification. Such quantitative biomechanical evaluations from realistic FSI workflows provide insights into disease progression and can be integrated with current stress testing for AS patients to comprehensively predict hemodynamics and valve function under both baseline and exercise conditions.

Fluid-structure interactions of peripheral arteries using a coupled in silico and in vitro approach

Vascular compliance is considered both a cause and a consequence of cardiovascular disease and a significant factor in the mid- and long-term patency of vascular grafts. However, the biomechanical effects of localised changes in compliance cannot be satisfactorily studied with the available medical imaging technologies or surgical simulation materials. To address this unmet need, we developed a coupled silico-vitro platform which allows for the validation of numerical fluid-structure interaction results as a numerical model and physical prototype. This numerical one-way and two-way fluid-structure interaction study is based on a three-dimensional computer model of an idealised femoral artery which is validated against patient measurements derived from the literature. The numerical results are then compared with experimental values collected from compliant arterial phantoms via direct pressurisation and ring tensile testing. Phantoms within a compliance range of 1.4–68.0%/100 mmHg were fabricated via additive manufacturing and silicone casting, then mechanically characterised via ring tensile testing and optical analysis under direct pressurisation with moderately statistically significant differences in measured compliance ranging between 10 and 20% for the two methods. One-way fluid-structure interaction coupling underestimated arterial wall compliance by up to 14.7% compared with two-way coupled models. Overall, Solaris™ (Smooth-On) matched the compliance range of the numerical and in vivo patient models most closely out of the tested silicone materials. Our approach is promising for vascular applications where mechanical compliance is especially important, such as the study of diseases which commonly affect arterial wall stiffness, such as atherosclerosis, and the model-based design, surgical training, and optimisation of vascular prostheses.

A technical review of computational fluid dynamics (CFD) applications on wind design of tall buildings and structures: Past, present and future

Over the past two decades, an upsurge in using Computational Fluid Dynamics (CFD) for wind design on tall buildings has been observed. An extensive amount of work has been performed, where validation has been at the forefront of most of these studies. Challenges associated with CFD and different methodologies used in the analysis haven't been well articulated within the scope of tall building design. Also, there is a lack of critical best practice guidelines in using CFD for wind analysis of structures which can be readily adopted by practitioners and researchers alike. To this end, this paper presents a comprehensive technical review of the application of Computational Fluid Dynamics (CFD) on tall buildings and structures. A thorough discussion of CFD and its concerning design challenges specific to tall building design, such as turbulence modelling, inflow turbulence and domain & mesh configurations, are discussed in detail. Furthermore, a comprehensive literature of CFD studies on tall buildings is presented, covering all important topics from basic bluff body aerodynamics to complex Fluid-Structure Interaction (FSI) studies. Where applicable, the literature is critically evaluated (impartially) in this paper and compared with supportive arguments from the author's extensive experience. Finally, the manuscript concludes with potential upcoming numerical methods such as the Lattice-Boltzmann Method (LBM) and the use of Artificial Intelligence (AI) to design tall buildings.

Effect of aortic bifurcation geometry on pressure and peak wall stress in abdominal aorta: Fluid-structure interaction study.

Geometry of aorto-iliac bifurcation may affect pressure and wall stress in aorta and thus potentially serve as a predictor of abdominal aortic aneurysm (AAA), similarly to hypertension. Effect of aorto-iliac bifurcation geometry was investigated via parametric analysis based on two-way weakly coupled fluid-structure interaction simulations. The arterial wall was modelled as isotropic hyperelastic monolayer, and non-Newtonian behaviour was introduced for the fluid. Realistic boundary conditions of the pulsatile blood flow were used on the basis of experiments in literature and their time shift was tailored to the pulse wave velocity in the model to obtain physiological wave shapes. Eighteen idealized and one patient-specific geometries of human aortic tree with common iliac and renal arteries were considered with different angles between abdominal aorta (AA) and both iliac arteries and different area ratios (AR) of iliac and aortic luminal cross sections. Peak wall stress (PWS) and systolic blood pressure (SBP) were insensitive to the aorto-iliac angles but sensitive to the AR: when AR decreased by 50%, the PWS and SBP increased by up to 18.4% and 18.8%, respectively. Lower AR (as a result of the iliac stenosis or aging), rather than the aorto-iliac angles increases the BP in the AA and may be thus a risk factor for the AAA development.

Fluid-structure interaction study of hemodynamics and its biomechanical influence on carotid artery atherosclerotic plaque deposits

Atherosclerotic plaque deposits are common causes of blood flow disruption in the carotid artery bifurcation and the associated fluid mechanics has been extensively studied using Computational Fluid Dynamics (CFD) and Fluid Structure Interaction (FSI). However, the elastic responses of plaques to hemodynamics in the carotid artery bifurcation has not been deeply studied using either of the above-mentioned numerical techniques. In this study, a two-way FSI study was coupled with CFD technique, using Arbitrary-Lagrangian-Eulerian method, to study the biomechanics of blood flow on nonlinear and hyperelastic calcified plaque deposits in a realistic geometry of the carotid sinus. FSI parameters such as total mesh displacement and von Misses stress on the plaque, as well as flow velocity and blood pressure around the plaques, were analyzed and compared to variables such as velocity streamline, pressure and wall shear stress obtained from CFD simulation in a healthy model. The blood flow simulations reveal complete reversed blood flow behavior in the internal carotid artery, ICAs and external carotid artery, ECAs for both cases. In particular, this study suggests that plaques, irrespective of the masses, possess a high yielding response to hemodynamic forces at the attaching edges, while the surfaces are vulnerable to rupture.

Computational Fluid Dynamics Analysis of the Influence of Openings on Wind Load and Structural Response in Triangular Buildings

Understanding the response of buildings to wind loads is critical, as these forces can generate significant pressure and suction, potentially leading to structural failure if overlooked. This research was focused on examining the effects of openings on triangular-shaped buildings when subjected to high wind load conditions. Utilizing CAD modeling and Computational Fluid Dynamics (CFD) simulations, the analysis was executed through the ANSYS simulation package. Subsequent Fluid-Structure Interaction (FSI) studies were conducted to ascertain shear stress and lateral deformation. The studies encompassed building models both with and without openings, with the evaluation of induced pressure and velocity. The resultant drag on buildings incorporating openings was discovered to be 6679N lower than those without openings. Furthermore, an analysis employing M25 concrete indicated a 33.13$3 \%$ reduction in lateral deformation in buildings with openings as compared to those without. For buildings constructed with M30 concrete, a 32.17$3 \%$ decrease in lateral deformation was observed. Despite the informative findings, it should be recognized that the investigation was confined to a particular range of wind load conditions and did not consider extreme scenarios. Dynamic wind effects and long-term structural behavior were not included in the current analysis. Therefore, while this study elucidates the importance of wind load analysis and structural reinforcement for maintaining building stability, further research is warranted. Such future investigations should consider broader simulation models, encompassing diverse building shapes and wind load conditions, and account for additional influential factors.

Determination of Optimum Design Parameters for Gyroid Scaffolds to Mimic a Real Bone-Like Condition In Vitro: A Fluid Structure Interaction Study

Abstract A suitable scaffold architecture is always desirable to get a biomimetic scaffold for bone tissue engineering. In this regard, a fluid structure interaction analysis was carried out on different Micro-CTs (μCTs) and gyroids to observe the in vitro mechanical responses due to fluid flow. Computational fluid dynamics method was used to evaluate the permeability and wall shear stress (WSS), followed by a finite element method to obtain the mechanical stress within scaffolds. Different types of gyroids were designed based on the number of unit cells and porosity, where porosity of gyroids was kept same as μCTs. The main objective of the study is to examine the variations of permeability, WSS and mechanical stress with respect to the number of unit cells and porosity for different gyroids and μCTs. Mechanical responses were also compared between gyroids and μCTs. The results of this study highlighted that permeability and WSS of μCTs came close to the gyroids with eight unit cells but had significant differences in mechanical stress. The permeability of gyroids increased with the increase of porosity but decreased with the increase in number of unit cells. The opposite trend was shown in case of WSS within gyroids. This study will guide us in predicting an ideal scaffold for trabecular bone replacement.

Numerical study on biomechanics in bifurcated coronary artery with plaques of different scenarios considering cardiac motion

During the development of atherosclerosis, plaques of different scenarios are formed at the bifurcation of the coronary arteries, which causes patients to exhibit different symptoms. The purpose of this study was to analyze the effect of plaque in different scenarios on the biomechanics of the bifurcated left coronary artery. In order to reflect the blood flow in the atherosclerotic coronary arteries more exactly, five vivid coronary artery models with a plaque of different scenarios are created based on Computed Tomography (CT) and anatomical images. Furthermore, the three-dimensional artery motion equations are created and fitted to the distal end of the coronary artery to describe the cardiac motion. The reciprocal influence of fluid and solid is also taken into account, constituting a fluid–structure interaction study. The risk of plaques in different scenarios was assessed by analyzing different physical parameters of arteries and blood. The results show that the effect of plaque on arterial stress is concentrated in the proximal coronary artery while the impact on blood flow is mainly focused on the narrow area and downstream of plaque. Wall shear stress promotes plaque growth in the early stages of atherosclerosis and drives plaque rupture after stenosis formation. There is a negative correlation between relative residence time and the degree of coronary artery stenosis and stiffness.

Fluid-structure interaction study for biomechanics and risk factors in Stanford type A aortic dissection.

Aortic dissection is a life-threatening condition with a rising prevalence in the elderly population, possibly as a consequence of the increasing population life expectancy. Untreated aortic dissection can lead to myocardial infarction, aortic branch malperfusion or occlusion, rupture, aneurysm formation and death. This study aims to assess the potential of a biomechanical model in predicting the risks of a non-dilated thoracic aorta with Stanford type A dissection. To achieve this, a fully coupled fluid-structure interaction model was developed under realistic blood flow conditions. This model of the aorta was developed by considering three-dimensional artery geometry, multiple artery layers, hyperelastic artery wall, in vivo-based physiological time-varying blood velocity profiles, and non-Newtonian blood behaviours. The results demonstrate that in a thoracic aorta with Stanford type A dissection, the wall shear stress (WSS) is significantly low in the ascending aorta and false lumen, leading to potential aortic dilation and thrombus formation. The results also reveal that the WSS is highly related to blood flow patterns. The aortic arch region near the brachiocephalic and left common carotid artery is prone to rupture, showing a good agreement with the clinical reports. The results have been translated into their potential clinical relevance by revealing the role of the stress state, WSS and flow characteristics as the main parameters affecting lesion progression, including rupture and aneurysm. The developed model can be tailored for patient-specific studies and utilised as a predictive tool to estimate aneurysm growth and initiation of wall rupture inside the human thoracic aorta.

Pathology and pathophysiology of the aortic root.

Pathologies of the aortic root amenable to repair with valve preservation include aneurysm formation, development of aortic insufficiency (AI) and aortic dissection. In the normal aortic root, the walls are constructed of 50-70 layers of concentric lamellar units. These units consist of sheets of elastin sandwiching smooth muscle cells interspersed with collagen and glycosaminoglycans. Medial degeneration results in disruption of the extracellular matrix (ECM), loss of smooth muscle cells and pooling of proteoglycans/glycosaminoglycans. These structural changes are associated with aneurysm formation. Aortic root aneurysms are commonly linked to hereditary thoracic aortic diseases including Marfan syndrome and Loeys-Dietz syndrome. One important pathway for hereditary thoracic aortic diseases is the transforming growth factor-β (TGF-β) cell-signalling pathway. Pathogenic gene mutations affecting various levels of this pathway have been implicated in aortic root aneurysm formation. Secondary effects of aneurysm formation include AI. Severe chronic AI leads to a pressure and volume load on the heart. Once symptoms develop or significant left ventricular remodelling and dysfunction occurs, the patient's prognosis is poor without surgery. Another consequence of aneurysm formation and medial degeneration is the risk of aortic dissection. Aortic root surgery is performed in 34-41% of surgeries for type A aortic dissection. Predicting those who will experience aortic dissections remains a challenge. Finite element analysis, study of fluid-structure interactions and aortic wall biomechanics are important areas of ongoing research.

Fluid-structure interaction and experimental studies of passive check valve based piezoelectric micropump for biomedical applications

ABSTRACT The piezoelectric micropump can be a prominent component of drug delivery systems due to its high performance, low cost, and faster response. However, backpressure remains to be the most common problem in micropump technology. Thus, microvalves or the passive check valve based piezoelectric micropump can be used to prevent the backpressure. However, the complex structure of the passive check valve based micropump limits the investigations of Fluid-Structure Interaction (FSI) due to the intricate Multiphysics involved. This paper presents the investigations on the flow behaviour and performance of a passive check valve based piezoelectric micropump using numerical analysis. The simulation study comprising FSI depicts the performance of a piezoelectric micropump using a fluid-structure coupling, fluid selection, structural modelling, and piezoelectric equations. The simulation results illustrate the micropump performance characteristics such as piezoelectric actuator displacement, micropump flow rate, backpressure, and Von Mises stress. Experiments are conducted to validate simulation results by studying the effect of voltage and frequency on the micropump flow and pressure characteristics. The experimental study demonstrated that the passive check valve based piezoelectric micropump delivers a maximum flow rate of 32 ml/min at zero backpressure. The micropump can pump the fluid against maximum backpressure up to 35 kPa.