Shear Stress Distribution Research Articles

The experimental determination of shear stress distribution along fully grouted rock bolts with different bond lengths subjected to pull testing

In this study, laboratory pull tests of rock bolts were conducted to verify and update existing stress transfer models. The rock bolt samples in the study had different bond lengths that were fully encapsulated in cementitious grout with different water-cement ratios. The test results show that the existing models do not correctly describe the shear stress distribution on the bond length in some loading stages. Three new models were proposed for the distribution of shear stress along the bond length. The first model describes cases where the bolt sample has a bond length that is much longer than the critical bond length, the second model describes cases where the bolt sample has a bond length slightly shorter than the critical bond length, and the third model describes cases where the bolt sample has a bond length that is much shorter than the critical bond length. In these models, the bolt is fully debonded along the section between the borehole collar and a depth of approximately one bolt diameter (db). The bolt is then partially debonded and the residual shear stress on the bolt increases with depth. In the first model, the shear stress reaches the maximum at a depth of approximately 3db. The shear stress then attenuates to zero at a depth of 25db. In the second and third models, the entire bond length is mobilized to carry load.

Pullout damage analysis of steel fibers under dynamic load based on numerical simulation

FRC is constantly subjected to dynamic loads during its service period, and dynamic pullout behavior of the fibers and the coupling effect between fibers can significantly affect the crack initiation and propagation of FRC. In this paper, based on the single fiber pullout behavior of experimental and numerical results, the failure process of the twin fibers dynamic pullout test was simulated by RFPA3D program with discontinuous and heterogeneous characteristics. The influence of fiber embedding length and fiber spacing on the interfacial bond behavior were analyzed in details. The internal damage degree, crack propagation, and interfacial shear stress of all test series were quantitatively characterized. The results indicate that the specimens with various fiber embedding lengths and fiber spacings present distinct damage evolution patterns. The decrease of the peak of AE events is followed by an increase, when the fiber embedding length is increased. In addition, the fiber spacing has a large influence on the distribution and transmission of interfacial shear stress. With the increase of fiber spacing, the peak of interfacial outside shear stress increases, while the peak value of interfacial inside shear stress gradually decreases. Meanwhile, the AE-accumulative energy presents a trend of decreasing first and then increasing.

Non-destructive identification of edge-component burgers vector of threading dislocations in SiC wafers by birefringence imaging

Non-destructive characterization of crystalline defects in SiC wafers is important for manufacturing high-performance SiC power devices with high productivity. The present study shows that the edge component of the Burgers vector can be identified by birefringence imaging under conditions deviating slightly from the crossed-Nicols condition and by calculation of the in-plane shear stress distribution. It is also found that the combination of birefringence observation and X-ray topography allows the discrimination of the family of threading screw dislocations. The present results will further the understanding of the relationship between defect structure and the properties of SiC power devices.

Considering the Influence of Coronary Motion on Artery-Specific Biomechanics Using Fluid-Structure Interaction Simulation.

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 the FSI model produced highly significant changes in Time Averaged Wall Shear Stress (TAWSS) + 9.8% LAD, + 8.8% LCx, - 2.0% RCA; Oscillatory Shear Index (OSI) + 208% LAD, 0% LCx, + 2600% RCA; and transverse wall Shear Stress (tSS) + 180% LAD, + 150% LCx and + 200% RCA (all p < 0.0001). Vessel wall strain was homogenous in all directions without-bending but became highly anisotropic under bending. Changes in median cyclic strain magnitude were seen for all three vessels in every direction. Changes shown in the magnitude and distribution of shear stress and wall strain suggest that bending should be considered on a vessel-specific basis in analyses of coronary artery biomechanics.

Numerical investigation into the composite behaviour of over-deformed segmental tunnel linings strengthened by bonding steel plates

Bonding steel plate has been used as a strengthening approach to repair disrupted segmental lining of operational tunnels. This paper introduces numerical investigation into the composite behaviour of the initially deformed segmental tunnel linings strengthened by bonding steel plates using finite element modelling. Cohesive zone modelling was used to simulate the interface bonding behaviour between the segmental linings and steel plates. The full history of the tunnel behaviour before and after strengthening were simulated, where the segmental tunnel lining is initially loaded to create some deformation, then after bonding steel plate, the strengthened tunnel is reloaded until failure occurs. By comparing the results with experimental data from the literature, the proposed model was proved to be capable of simulating the strengthened lining behaviour and able to capture the strengthening failure process in terms of the interface debonding. Subsequently, the segmental lining response and interface shear stress distribution and propagation were analysed to interpret the interaction and failure mechanism of the steel plate strengthened segmental linings. The influence of the initial deformation and the steel plate thickness were investigated and discussed in terms of the strengthened stiffness and capacity. It has been found that the interface shear stress concentration occurred at the positions of the segment joints, where bond damage first initiated. The ultimate failure of the steel plate strengthening happened suddenly once a local debonding zone close to the segmental joint was formed. In addition, the predicted results indicate that a delay in strengthening would result in an increase in strengthened capacity but a decrease in strengthened stiffness. By using thicker steel plates, the strengthened stiffness was improved, while the strengthened capacity could be improved only if the thickness was relatively thin.

On the distributed blowing control of flow around a square cylinder at a low Reynolds number

This paper numerically investigates the distributed blowing control of the flow around a square cylinder at a low Reynolds number of Re=200. The air holes are placed at the windward or leeward stagnation points. The control effect of the unsteady aerodynamic forces is notably different with different spanwise distributions of air holes, which is represented by the dimensionless air hole area ratio G. The simulation results indicate that the windward blowing control (WBC) shows better control effect than the leeward blowing control (LBC) in reducing the time-averaged drag coefficient Cd¯ of the square cylinder while the fluctuating lift coefficient Cl′ can be significantly suppressed by the LBC. Besides, the surface pressure distribution, the turbulence kinetic energy (TKE) and Reynolds shear stress (RSS) distributions and the shedding vortices in the wake are analysed and compared in detail under different control conditions. Finally, through the instantaneous 3D vortex structures and the spanwise fluctuating velocity w′ distribution in the flow field, the suppression of the unsteady aerodynamic forces is mainly related to the 3D vortex pairs induced by the blowing jet.

Numerical investigation of the effect of changes in blood viscosity on parameters hemodynamic blood flow in the left coronary artery with consideration capturing fluid–solid interaction

Cardiovascular diseases are unfortunately one of the leading causes of death in today's society. It is important to analyze blood flow in various parts of the circulatory system. The coronary artery is made up of four main arteries, and the left coronary artery is responsible for delivering blood to the heart muscle. This research utilizes computational fluid dynamics and finite element methods to investigate and analyze coronary vessels by studying changes in blood characteristics. The aim of this study is to analyze and model the flow of blood under different conditions of the coronary vessels, with a particular focus on the vessels on the left side. This is in response to changes in hematocrit, which can cause an increase or decrease in blood viscosity (μp) (N.s/m2). In general, by applying condition flexibility for the vessel, it is possible to reduce pressure distribution on the wall when compared to the rigid model. When considering changes in viscosity (μ) (kg/m. s), such as an increase from 0.0029 to 0.0067, this can lead to changes in the shear stress distribution (N/m2) on the wall. Specifically, this increase in blood viscosity (μp) (N.s/m2) causes maximum tension, resulting in the wall shear WSS (N/m2) rising from 60 to 154 Pascal's, which is a 140% increase. Based on the current data, it appears that there is a high flow pressure in the artery, resulting in maximum relative pressure values of 6300 and 6450 Pascal's for the rigid and flexible models, respectively, at the separating joint of the bifurcation.

Pressure coherence and flow structure of a twisted elliptical cylinder at moderate Reynolds number

In this study, we performed an experimental study to explore the surface pressures and flow structures around twisted elliptic (TE) cylinders at a Reynolds number of 3.8 × 104. Two TE cylinders, denoted as TE11 and TE12, with aspect ratios of 1.1 and 1.2 for elliptical cross-sections, respectively, were selected to compare the performance of vortex shedding suppression. The distribution characteristics of the fluctuating pressure at different spanwise positions and the phase difference and coherence function between the pressure signals were analyzed. The results showed that TE12 cylinder was not dominated by antiphase shedding vortices, as in the baseline and TE11 cylinders, but rather by low-frequency components in the flow field, yielding a Gaussian distribution of the fluctuating pressure. The pressure pulsations were significantly asymmetric for the TE12 cylinder due to the earlier flow separation on the upper surface, but this asymmetry was not apparent for the TE11 cylinder. The Reynolds shear stress distribution revealed that the transition to turbulence in the separated layer was significantly delayed by the TE surface. Moreover, for TE12 cylinder, zero turbulence fluctuations in the near wake explained the low-frequency domination of the pressure fluctuations, resulting in 93.8% attenuation of the lift fluctuations.

Effects of tributary floodplain on confluence hydrodynamics

Confluences are common components of river networks and are characterized by a highly complex flow structure. Two confluence geometries, without and with the floodplain in the tributary, were comparatively investigated to highlight the effects of floodplain on confluence hydrodynamics. The three-dimensional velocity field and the spatial distribution of turbulent kinetic energy and Reynolds shear stresses were analysed. In the second geometry, a tilted shear layer was observed, which was related to the flow expansion from the main channel into the tributary. Significant secondary motions are mainly related to the fluid upwelling in the lee of the floodplain step and streamline curvature. A wider flow separation zone was found, while the length of the separation zone was not affected by the floodplain flow. The results could be useful to understand the complex hydrodynamics of the large confluence between the Yangtze River and the Poyang Lake, characterized from a floodplain under high flow conditions.

Increasing the Compressive Strength of Helicoidal Laminates after Low-Velocity Impact upon Mixing with 0° Orientation Plies and Its Analysis.

The helicoidal laminate is a kind of nature inspired fiber reinforced polymer, and the ply orientation affects their mechanical properties for engineering structural applications. A variety of helicoidal laminates with uniform and non-linear pitch angles mixed with additional 0° plies are fabricated to investigate the impact resistance through low-velocity impact and after-impact compression tests. Additionally, helicoidal laminates with constant pitch angles, quasi-isotropic laminate, and cross-ply laminates are also fabricated for a comparative study. The impact characteristics and the compressive strength are analyzed in view of the impact model, shear stress distribution, and fracture toughness. The results suggest that 10° or 20° are the better basic pitch angles before mixing 0° orientation plies. The 0° orientation plies may affect the contact stiffness, bending stiffness, damage extent, and compressive modulus. The compressive strength reaches the highest in tests on two samples with different percentages of 0° orientation plies and ply setups. Bending stiffness also dominates the impact response. The analysis on the laminate parameters provides ideas to improve the residual strength of helicoidal laminate.

Simplifying Raupach's model of shear‐stress partitioning by clarifying the relationship between β and σ and quantifying the shear‐stress probability density based on numerical simulation

AbstractWe used computational fluid dynamics to simplify Raupach's model by clarifying the relationship between the parameter β (the ratio of element to surface drag coefficients) and the roughness‐element shape parameter σ using a k‐ω shear‐stress transport (SST) turbulence model with rigid cylindrical roughness elements. Results showed that β ranged between 102 and 242 and the parameter m (a relationship between the average and the peak surface shear stresses) ranged between 0.15 and 0.32 for partitioning of surface shear stress. β decreased with increasing σ, and the relationship followed a power law. We confirmed this relationship by comparing wind tunnel and field measurements for different types of roughness element (blocks, hemispheres, trapezoids and plants based on the results from previous studies). However, the model has some limitations due to the characteristics such as streamline and porosity of plants. The peak mean stress ratio (a) ranged between 2.09 and 3.61. We also confirmed that the probability‐density function for the surface shear stress proposed by Zou et al. (2022) described the distribution of the surface shear stress among roughness elements well, which is essential to accurately estimate surface erosion by wind.

Computational fluid dynamics for the optimization of internal bioprinting parameters and mixing conditions

Tissue engineering requires the fabrication of three-dimensional (3D) multimaterial structures in complex geometries mimicking the hierarchical structure of biological tissues. To increase the mechanical and biological integrity of the tissue engineered structures, continuous printing of multiple materials through a printing head consisting of a single nozzle is crucial. In this work, numerical analysis was carried out to investigate the extrusion process of two different shear-thinning biomaterial solutions (alginate and gelatin) inside a novel single-nozzle dispensing system consisting of cartridges and a static mixer for varying input pressures, needle geometries, and outlet diameters. Systematic analysis of the dispensing process was conducted to describe the flow rate, velocity field, pressure drop, and shear stress distribution throughout the printing head. The spatial distribution of the biopolymer solutions along the mixing chamber was quantitatively analyzed and the simulation results were validated by comparing the pressure drop values with empirical correlations. The simulation results showed that the proposed dispensing system enables to fabricate homogenous material distribution across the nozzle outlet. The predicted shear stress along the proposed printing head model is lower than the critical shear values which correspond to negligible cell damage, suggesting that the proposed dispensing system can be used to print cell-laden tissue engineering constructs. &amp;nbsp;

Computational fluid dynamics simulations of mitral paravalvular leaks in the human heart

Abstract Funding Acknowledgements Type of funding sources: Public Institution(s). Main funding source(s): Warsaw University of Technology - BIOTECHMED-3 project under the program Excellence Initiative: Research University. Background Presence of paravalvular leaks (PVL) can lead to hemolysis and high shear stress that affects erythrocytes passing through PVL channels may be the main reason behind this pathology. In vitro, shear stress forces above 300 Pa cause erythrocyte destruction. Distribution of shear stress can currently be precisely determined with computational fluid dynamics (CFD). CFD is a numerical modelling method based on solving equations of differential balance of mass, momentum and energy for a small section of fluid known as a computational cell. Purpose To investigate the magnitude of shear stress forces that affect erythrocytes in PVL channels and define properties of PVL channels that increase the likelihood of hemolysis. Methods Models of left-sided heart chambers with artificial mitral valves and PVLs were created based on cardiac computed tomography data from subjects with PVLs. Computational fluid dynamics principles were applied to create patterns of blood flow through PVL channels. 4 channels with cross-sectional areas (CSA) of 26.2 mm2 (model I), 15.7 mm2 (model 2), 20.4 mm2 (model 3) and 32 mm2 (model 4) were examined. Length of PVL channels was 6.5, 9.5, 7.3 and 3.25 mm respectively. In models I,III and IV the PVL channel was located anteriorly around the mitral annulus, whereas in model II a posterior location was described. Blood flow was simulated using a commercial CFD software (ANSYS Fluent 2020R1). Simulations were performed for heart rate of 60 beats per minute. The following variables were examined regarding blood flow through PVL channels: wall shear stress, shear stress in fluid, volume of PVL channels in which shear stress exceeded 300 Pa and duration of exposure of red blood cells to shear stress above 300 Pa. Obtained values were compared with lactate dehydrogenase (LDH) activities in subjects whose cardiac CTs were used to create PVL models. One of the models of the left ventricle is presented in picture 1. Studied PVL channels are presented in picture 2. Results In all models shear stress value of 300 Pa was exceeded. Maximal wall shear stress and maximal shear stress in fluid values were not related to CSA of the PVL channel. Lowest values of all examined variables were obtained for model 2, which had the longest PVL channel and a posterior location. The lowest LDH activity was noted in model with the lowest volume of the PVL channel with shear stress above 300 Pa (model 2) and the highest LDH activity in model with both the highest volume of the PVL channel with shear stress above 300 Pa and longest exposure to shear stress exceeding 300 Pa (model III). Conclusions Presence of PVLs is always accompanied by some degree of hemolysis. Shear stress values in PVL channels are not related to CSA of these channels. Volume of PVL channels in which shear stress exceeds 300 Pa and duration of exposure of erythrocytes to shear stress above 300 Pa may influence the severity of hemolysis.

Direct Numerical Simulation of Low and Unitary Prandtl Number Fluids in Reactor Downcomer Geometry

Mixed convection of low and unitary Prandtl fluids in a vertical passage is fundamental to passive heat removal in liquid metal and gas-cooled advanced reactor designs. Capturing the influence of buoyancy in flow and heat transfer in engineering analysis is hence a cornerstone to the safety of the next-generation reactor. However, accurate prediction of the mixed convection phenomenon has eluded current turbulence and heat transfer modeling approaches, yet further development and validation of modeling methods is limited by a scarcity of high-fidelity data pertaining to reactor heat transfer. In this work, a series of direct numerical simulations was conducted to investigate the influence of buoyancy on descending flow of liquid sodium, lead, and unitary Prandtl fluid in a differentially heated channel that represents the reactor downcomer region. From time-averaged statistics, flow-opposing/aiding buoyant plumes near the heated/cooled wall distort the mean velocity distribution, which gives rise to promotion/suppression of turbulence intensity and modification of turbulent shear stress and heat flux distribution. Frequency analysis of time series also suggests the existence of large-scale convective and thermal structures rising from the heated wall. As a general trend, fluids of lower Prandtl number were found to be more susceptible to the buoyancy effect due to stronger differential buoyancy across the channel. On the other hand, the effectiveness of convective heat transfer of the three studied fluids showed a distinct trend against the influence of buoyancy. Physical reasoning on observation of the Nusselt number trend is also discussed.

Strength and elastic buckling of a sandwich cylindrical pressure vessel with dished heads

The paper is devoted to a sandwich cylindrical pressure vessel closed with a dished head at both ends and loaded with external uniformly distributed pressure. Non-standard construction of the vessel is presented characterised by an asymmetric cross-section and superellipsoidal dished heads. The strength and buckling of such structure is numerically studied with the use of the finite element method limited to the linear range. The calculations are carried out for models with aluminium faces and aluminium foam core. The obtained results revealed the advantage of the superellipsoidal dished head compared to the hemispherical one in terms of stress distribution — the edge effect being a typical problem in such structures is diminished. This opens potential applications of such solution in actual structures. It is pointed out that the application of a superellipsoidal head assure a more favourable shear stress distribution in the core.

Stability characteristics of the spiral Poiseuille flow induced by inner or outer wall rotation

In this paper we reveal, that the stability behavior of the spiral Poiseuille flow in an annular gap with rotating inner or outer cylinder exhibits a striking similarity at low and intermediate rotation rates, while both cases differ significantly at higher rotation rates. Based on the work of Vasanta Ram (2019) we formulate the flow problem by means of the inner swirl parameter (Si), the outer swirl parameter (So) and the curvature parameter (ϵ). Six different values of the curvature parameter {0.005; 0.025; 0.111; 0.25; 0.333; 0.785} and a swirl range of 10−5<Si;So<105 are investigated. We reveal that for the rotating outer cylinder case three characteristic jumps of the critical axial and azimuthal wavenumbers can be identified. Similar features can be identified for the inner rotation case. Based on this, we define three regimes delimited for both the rotating inner and rotating outer cylinder which enables us to perform a systematic comparison. The first regime transition occurs at low values of the swirl parameter (Si; So>10−4) and is accompanied by a rapid decrease of the critical Reynolds number. Our computations reveal that this regime transition does not occur for a small curvature parameter of ϵ= {0.005; 0.025} in the outer rotation case. The second wavenumber jump occurs at higher swirl parameters of around Si>2.5 and So>1.6. While the critical Reynoldsnumber decreases monotonously in the inner cylinder rotating case, we show that in the case of rotating outer cylinder a rapid increase of Rec is observed as So increases further. To gain an insight into the mechanisms involved that induce such wavenumber jumps, a detailed comparative study on the associated Reynolds shear stress distributions is performed. For larger ϵ it is shown that the distributions of the Reynolds shear stresses change significantly over the first jump exhibiting similar features for both flow cases, leading to the conclusion that in both cases the same centrifugal instability is triggered here. Instead, the distributions of the Reynolds shear stresses before and after the second jump are fundamentally different for inner and outer rotation. While the Reynolds shear stresses spread over the whole gap height for the inner rotation case, they are nonzero only close to a small regime near the inner cylinder for the outer rotation case at high rotation rates. Overall, analyzing the shear stresses, we reveal that a similar instability arises in the Spiral Poiseuille flow with inner and outer cylinder rotation at intermediate swirls, but at higher swirl outer rotation seems to give rise to an instability associated with a critical layer that is inherently different to the inner rotation case.

Experimental and numerical analysis of single-strap adhesive joints combining thin-walled steel and fast-growing natural timber

Fast-growing forests are widespread distribution, but the relevant timber products are limited by insufficient strength and low reliability in the architectural structure. In recent years, the combination of rapidly growing timber and thin-walled steel to enhance structural performance has attracted attention, and connection performance is critical in ensuring a compelling combination. In addition, adhesive technology has potential applications due to its high efficiency and lightweight. Nevertheless, in light construction, the adhesion behavior between thin-walled steel and largethickness timber with relatively low mechanical properties has yet to be effectively studied and revealed. This study investigates the bonding properties of thin-walled steel and fast-growing timber single-strap joints by numerical and experimental methods. The SS joints' shear strength and failure modes were obtained by tensile tests, considering different adhesive and overlap lengths. In addition, stress analysis was performed using the finite element method (FEM) combined with the cohesive zone model (CZM) to explore critical issues such as damage variables, peak stresses, etc. Furthermore, the parameters such as overlap, the thickness of adherends, and edge distance were investigated. As a result, it is concluded that the bond of thin-walled steel-fast-growing timber is a special non-balanced connection. The study indicates that shear stress distribution is steeper than other strap joints. The other difference is that the right end in overlapping areas may experience higher peel stress than the left ends, which might delaminate the timber. Yielding phenomena may also occur at such weak timber ends along the normal direction. The bearing capacity of these joints is susceptible to the difference in stiffness between timber and steel. Joint performance can be enhanced by increasing the timber thickness and overlap length appropriately. The summary obtained from this paper can be a reference for applying adhesive in thin-walled steel-fast-growing timber composite structure systems.

Analysis of the Shear Stresses in a Filling Line of Parenteral Products: The Role of Fittings

Fill-finish of parenteral formulations represents a crucial step in the pharmaceutical industry that necessitates careful monitoring of product stability down the line. Shear stress and interfacial stress are two elements that threaten product stability, the respective contributions of which are still up for debate. This article focuses on the analysis of shear stress in the sampling phase of the filling line. Specifically, Computational Fluid Dynamics (CFD) simulations were employed to determine the shear stress distribution experienced by a protein-based parenteral drug as it passes through sampling fittings of various shapes under laminar and turbulent regime conditions. Rather than seeking the specific mechanism triggering the destabilization of a product, an attempt was made to analyze the fluid dynamics within these fittings and offer further understanding of the resulting shear stress. In addition, information was collected on the product path within the fittings, which allowed the identification of equations suitable for describing the shear stress distribution. The proposed approaches made it possible to consider the actual flowrate subjected to a given shear stress at a given time. Finally, a comparison was drawn with respect to the fluid dynamics within classical straight tubing to outline differences. This study revealed that the shear stress experienced within the fittings was higher than that in the tubing. Moreover, significant differences were reported in the T-fitting case under turbulent conditions.

Turbulence Kinetic Energy and High-Order Moments of Velocity Fluctuations of Flows in the Presence of Submerged Vegetation in Pools

The flow in arid and semi-arid regions changes significantly during seasons, letting many vegetation patches develop in different parts of rivers. In the presence of aquatic plants in streams, different flow structures have resulted. When the water level increases in these rivers, the presence of vegetation patches influences the turbulent flow structures, which may considerably change the estimation of key hydraulic parameters. The results of earlier investigations indicated that a wide range of submerged and non-submerged vegetation influences the hydrodynamic features of flows in rivers and streams. In the present investigation, two pools with various slopes of entry and exit sections were used to conduct eight independent experiment runs. In addition, a vegetation patch over the entire pool section has been set up to investigate the effects of the vegetation patch on flow structures in pools. The effect of two slopes of 5 and 10 degrees for both entrance and exit of the pools on flow structure has been investigated. Considering two aspect ratios of 2.0 and 2.7, the distributions of flow velocity, Reynolds normal and shear stresses, turbulence intensities, turbulent kinetic energy (TKE), quadrant analysis, and spectral analysis have been studied at the trailing edge of the vegetation patch along an artificial pool. Results show that, for large entrance and exit slopes (10 degrees), the TKE distribution profiles have no specific form. However, the TKE values have a convex-shaped distribution pattern with the maximum TKE value near the bed when the slopes of the entrance and exit sections of the pool are small (5 degrees). Results showed that both ejections and sweeps govern the turbulence structures and coherent motions at the trailing edge of the vegetation patch along the pool. The geometry, entrance, and exit slopes of the pool have no effect on the validation of power spectral function compared to the presence of a vegetation patch in a flatbed.

Morphology and Hemodynamics of Cerebral Arteries and Aneurysms in a Rare Pair of Monozygotic Twins.

In this preliminary study, the underlying pathophysiology mechanisms of cerebral aneurysms (CAs) in monozygotic twins (MTs) were investigated via a rare pair of MTs (twin A and twin B) involving four reconstructed arterial models using preclinical information. First, dimensions and configurated outlines of three-perspective geometries were compared. Adopting an in-vitro validated numerical CA model, hemodynamic characteristics were investigated in the MTs, respectively. Despite expected genetic similarities, morphological comparisons show that configurations of cerebral arteries exhibit significant differences between the twins. The ICA size of twin A is larger than that in twin B (2.23~25.86%), varying with specific locations, attributing to variations during embryological developments and environmental influences. Numerical modeling indicates the MTs have some hemodynamic similarities such as pressure distributions (~13,400 Pa) and their oscillatory shear index (OSI) (0~0.49), but present significant differences in local regions. Specifically, the difference in blood flow rate in the MTs is from 16% to 221%, varying with specifically compared arteries. The maximum time-averaged wall shear stress (53.6 Pa vs. 37.8 Pa) and different local OSI distributions were also observed between the MTs. The findings revealed that morphological variations in MTs could be generated by embryological and environmental factors, further influencing hemodynamic characteristics on CA pathophysiology.