Search Results (95)

Pain and variable uptake remain practical barriers to needle-based delivery. Device-level vibration has emerged as a simple strategy for improving tolerability and dispersion, but its fluid-mechanical basis remains incomplete. Using a lattice Boltzmann model with a porous-media skin surrogate, we applied time-periodic inlet pressures at 0%, 16.6% ($\mathsf{\Delta }{P}_1$), and 35.1% ($\mathsf{\Delta }{P}_2$) amplitudes to Newtonian, model shear-thinning, and clinically measured protein formulations. We quantified the wall shear stress, wetted area, dispersion length, and pressure cost over one cycle. Vibration increased the normalized wetted area by 10.6% for Newtonian flow and by 15.9% and 21.3% for the non-Newtonian cases at $\mathsf{\Delta }{P}_1$ and $\mathsf{\Delta }{P}_2$, respectively, while advancing the penetration front and lateral dispersion. The one-cycle pressure cost per wetted area decreased by 3.9% for Newtonian flow and by 5.96% and 7.80% for non-Newtonian flows. For shear-thinning fluids, the wall-shear history was reshaped, with a brief early amplification and late-phase mean reductions of 10.3% and 13.3% at $\mathsf{\Delta }{P}_1$ and $\mathsf{\Delta }{P}_2$. These results establish a fluid-mechanical mechanism linking clinically relevant vibration amplitudes to reduced sustained shear exposure, deeper and broader depot formation, and improved conditions for drug uptake. Full article

Traditional exterior walls are heavy, offer insufficient insulation, and have poor durability, making it challenging to meet the combined requirements of energy efficiency and structural enclosure performance. To address the issues of excessive weight and inadequate insulation in conventional concrete exterior wall panels, alternative materials and designs are being adopted. A novel double-layer composite wall panel structure is proposed, arranging normal concrete (NC) on the exterior side to ensure the panel’s durability and ceramsite foam concrete (CFC) on the interior side to enhance thermal insulation and reduce thermal bridging effects. To address the scenario where the wall panel is subjected to out-of-plane loads during service, causing stress in the CFC layer, bending performance tests were conducted on CFC-NC double-layer composite panels under load applied on the CFC side. Research shows that CFC-NC double-layer composite wall panels exhibit bending performance under four-point bending conditions that is basically consistent with that of monolithic wall panels. As the thickness of the CFC layer increases, cracks may appear near the interface in the CFC layer that do not extend from NC cracking, and may even occur earlier than NC cracking. As the density grade of CFC decreases, the compressive deformation of CFC becomes more pronounced; however, no crushing of the CFC occurs at the ultimate bearing capacity stage. Under four-point bending conditions, the strain at the mid-span section of the composite wall panel along the thickness direction is basically linearly distributed. Under the same conditions of wall panel thickness, reinforcement ratio, and shear span ratio, the flexural bearing capacity of CFC-NC double-layer composite wall panels with CFC density grades A8, A6, and A4 is approximately 12.5%, 25.03%, and 18.29% lower, respectively, compared to C30 cast-in-place wall panels. The flexural bearing capacity of the composite panels increases correspondingly with the increase in CFC layer thickness and reinforcement ratio. Specimens with smaller shear span ratios exhibit more pronounced shear effects. Based on the stress–strain relationship of CFC, a modified calculation method for the flexural capacity of ordinary concrete sections is presented. Referring to the ACI 318-14 code, a calculation method for the bending deformation of composite wall panels is provided. The research results can offer a theoretical basis for the design and application of CFC-NC double-layer composite wall panels. Full article

Background and Clinical Significance: Although rupture of aneurysms at the internal carotid-posterior communicating artery (ICA-PCom) junction accounts for a small percentage of all ruptured intracranial aneurysms, they are clinically relevant due to their proximity to perforator-rich cisterns, the optic-carotid-oculomotor pathways and flow-diverting zones, as well as their high likelihood for causing early neurological instability. Additionally, ruptured ICA-PCom aneurysms that have multiple lobulations are associated with increased variability in wall shear stress, local inflammatory remodeling and higher propensity for rupture at smaller sizes compared to other types of aneurysms. Due to the rapidity of early physiological destabilization in most patients with ruptured ICA-PCom aneurysms, clinical–anatomical correlations in these cases are often obscured by neurological deterioration; therefore, the presentation of this patient provides a unique opportunity to correlate the minimal early symptoms, tri-lobulation of the aneurysm and confined cisternal hemorrhage, to better understand rupture behavior, surgical decision-making in an anatomically challenging area, and postoperative recovery. Case Presentation: A 48-year-old hypertensive female experienced an acute “thunderclap” headache accompanied by intense photophobia and focal meningeal irritation, but, unexpectedly, retained a normal neurologic examination. She did exhibit some minor ocular motor micro-latencies, early cortical attentional strain and lateralized pain sensation that suggested localized cisternal involvement despite lack of generalized neurologic impairment. Digital subtraction angiography and three-dimensional CT angiography revealed a ruptured, tri-lobulated aneurysm originating from the communicating portion of the left internal carotid artery proximal to its origin from the posterior communicating artery, oriented toward the perimesencephalic cisterns. The aneurysm was surgically clipped using a standard left pterional craniotomy with direct visualization, after careful dissection through the carotid and optic windows to preserve the anterior choroidal artery, oculomotor nerve, and surrounding perforators. The neck of the aneurysm was reconstructed with a single straight clip, without compromise to the parent vessel lumen. The patient had an uneventful postoperative course without vasospasm or neurologic deficit. At both 3 and 9 months postoperatively the patient remained free of clinical neurologic deficit, and imaging demonstrated continued aneurysm exclusion, preserved ICA-PCom anatomy, and no evidence of delayed ischemic injury or hydrocephalus. Conclusions: The goal of this report is to demonstrate how a ruptured, morphologically complex ICA-PCom aneurysm may present with preserved neurologic function, thereby enabling the study of clinical–anatomical associations before secondary injury mechanisms intervene. The relationship between the configuration of the patient’s symptoms, geometry of the aneurysm and pattern of hemorrhage within the cisterns offers insight into a rare rupture pattern observed during routine clinical experience. Through complete anatomical analysis, timely microsurgical reconstruction and consistent follow-up, the authors were able to achieve long-term recovery of this particular patient. Continued advancements in vascular imaging techniques, aneurysmal wall modeling, and postoperative monitoring will likely help clarify the underlying mechanism(s) responsible for such presentations. Full article

This study employs physical experiments and the RFPA3D numerical method to investigate the fracture evolution of rocks containing a central hole with symmetrically arranged double cracks (seven inclination angles β) under biaxial compression. The results demonstrate that peak stress and strain exhibit nonlinear increases with rising β. Tensile–shear failure dominates at lower angles (β = 0–60°), characterized by secondary crack initiation at defect tips and wing/anti-wing crack development at intermediate angles (β = 45–60°). At higher angles (β = 75–90°), shear failure prevails, governed by crack propagation along hole walls. When β exceeds 45°, enhanced normal stress on crack planes suppresses mode II propagation and secondary crack formation. Elevated lateral pressures (15–20 MPa) significantly alter failure patterns by redirecting the maximum principal stress, causing cracks to align parallel to this orientation and driving anti-wing cracks toward specimen boundaries. Three-dimensional analysis reveals critical differences between internal and surface fracture propagation, highlighting how penetrating cracks around the hole crucially impact stability. This study provides valuable insights into complex fracture mechanisms in defective rock masses, offering practical guidance for stability assessment in underground mining operations where such composite defects commonly occur. Full article

The paper is concerned with experimental investigations and numerical simulations of airflow in a rigid model of human tracheal bifurcation during a respiratory cycle in the presence of cough. The main goal of the study is to calculate the velocity and tracheal wall shear stress (WSS) distributions under the time variation in the pressure difference. A sequence of inspiration-expiration of measured flow rates and pressure is used to calibrate the 3D unsteady numerical solutions for different imposed boundary conditions at the edges of the bifurcation. The experimental data are obtained using commercial medical devices: (i) a spirometer and (ii) a mechanical ventilator, respectively. CT images of the lung airways were used to reconstruct the tracheal test geometry by 3D printing techniques. Flow spectrum, vortical structures, and the wall stresses are analyzed for the computed cases. Four turbulence models (k − ɛ, k − ω SST, k − ɛ R, and LES) are compared, and all indicate an increase in peak WSS and vortex intensity during coughing versus normal expiration. The present work confirms the importance of CFD simulations to model and quantify airflow throughout the respiratory cycle. The paper proposes a method to calculate wall shear stress, one of the most relevant parameters for characterizing airway function and the mechanical response of tracheal endothelial cells. Full article

To study the mechanical properties and displacement evolution of rock masses near coal-seam normal faults under mining disturbances; this paper utilizes fiber optic monitoring and distributed strain measurement techniques to achieve the fine monitoring of the entire process of stress–displacement–strain during mining. The experimental design adopts a stepwise mining approach to systematically reproduce the evolution of fault formation; slip; and instability. The results show that the formation of normal faults can be divided into five stages: compressive deformation; initiation; propagation; slip; and stabilization. The strength of the fault plane is significantly influenced by the dip angle. As the dip angle increases from 30° to 70°, the peak strength decreases by 23%, and the failure mode transitions from tensile failure to shear failure. Under mining disturbances, the stress field in the overlying rock shifts from concentration to dispersion, with a stress mutation zone appearing in the fault-adjacent area. During unloading, vertical stress decreases by 45%, followed by a rebound of 10% as mining progresses. The rock layers above the goaf show significant subsidence, with the maximum vertical displacement reaching 150 mm. The displacement between the hanging wall and footwall differs, with the maximum horizontal displacement reaching 78 mm. The force chain distribution evolves from being dominated by compressive stress to a compressive–tensile stress coupling state. The fault zone eventually enters a stress polarization state and tends toward instability. A large non-uniform high-speed zone forms at the fault cutting point in the velocity field, revealing the mechanisms of fault instability and the initiation of dynamic disasters. These experimental results provide a quantitative understanding of the multi-physics coupling evolution characteristics of coal-seam normal faults under mining disturbances. The findings offer theoretical insights into the instability of coal-seam normal faults and the mechanisms behind the initiation of dynamic disasters. Full article

Background/Objectives: The aberrant subclavian artery (ASA) represents the most common congenital anomaly of the aortic arch, and is frequently associated with a Kommerell diverticulum, an aneurysmal dilation at the anomalous vessel origin. This condition carries a significant risk of rupture and dissection, and growing evidence indicates that local hemodynamic alterations may contribute to its development and progression. Computational Fluid Dynamics (CFD) provides a valuable non-invasive modality to assess biomechanical stresses and elucidate the pathophysiological mechanisms underlying these vascular abnormalities. Methods: In this study, twelve thoracic CT angiography scans were analyzed: six from patients with ASA and six from individuals with normal aortic anatomy. CFD simulations were performed using OpenFOAM, with standardized boundary conditions applied across all cases to isolate the influence of anatomical differences in flow behavior. Four key hemodynamic metrics were evaluated—Wall Shear Stress (WSS), Oscillatory Shear Index (OSI), Drag Forces (DF), and Turbulent Viscosity Ratio (TVR). The aortic arch was subdivided into Ishimaru zones 0–3, with an adapted definition accounting for ASA anatomy. For each region, time- and space-averaged quantities were computed to characterize mean values and oscillatory behavior. Conclusions: The findings demonstrate that patients with ASA exhibit markedly altered hemodynamics in zones 1–3 compared to controls, with consistently elevated WSS, OSI, DF, and TVR. The most pronounced abnormalities occurred in zones 2–3 near the origin of the aberrant vessel, where disturbed flow patterns and off-axis mechanical forces were observed. These features may promote chronic wall stress, endothelial dysfunction, and localized aneurysmal degeneration. Notably, two patients (M1 and M6) displayed particularly elevated drag forces and TVR in the distal arch, correlating with the presence of a distal aneurysm and right-sided arch configuration, respectively. Overall, this work supports the hypothesis that aberrant hemodynamics contribute to Kommerell diverticulum formation and progression, and highlights the CFD’s feasibility for clarifying disease mechanisms, characterizing flow patterns, and informing endovascular planning by identifying hemodynamically favorable landing zones. Full article

The downstream decay of induced swirling flow within an internal passage has implications for heat transfer enhancement, species mixing, and combustion processes. For this paper, swirling flow in an internal passage was investigated using both experimental and computational techniques. Two staggered rows of 8 vanes each with an NACA 0015 profile, intended to turn the near-wall flow 45° to the flow direction, were installed on the top and bottom surfaces of the Roughness Internal Flow Tunnel (RIFT) wind tunnel. The vanes induced opposite lateral components in—the flow near the upper and lower surfaces of the rectangular test section of the RIFT and induced a swirling flow pattern within the passage. A 4-camera tomographic particle tracking velocimetry (PTV) system was used to evaluate airflow within a 40 mm × 40 mm × 60 mm measurement volume at the tunnel midline 0.5 m downstream of the induced swirl. Mean flow velocity measurements were collected at hydraulic diameter-based Reynolds numbers of 10,000, 20,000, and 30,000. To validate PTV measurements, particularly the camera-plane normal component of velocity, traces across the measurement volume were taken using a five-hole probe. The results of both measurement methods were compared to a computational simulation of the entire RIFT test section using a shear stress transport (SST) k-ω, Improved Delayed Detached Eddy Simulation (IDDES) turbulence model. The combined particle tracking measurements and five-hole probe measurements provide a method of investigating the turbulent flow model and simulation results, which are needed for future simulations of flows found inside swirl-inducing combustor nozzles. Full article

Background/Objectives: Hemodynamic stressors, including abnormal wall shear stress (low or high) or oscillatory shear index are recognized as contributors to the pathogenesis, growth, and rupture of intracranial aneurysms (IAs). Computational fluid dynamics (CFD) has therefore become an essential tool for their quantitative assessment. This systematic review aimed to identify the most frequently analyzed hemodynamic and morphological parameters in recent CFD studies and summarize the methodological strategies employed. Methods: A systematic review was conducted following the PRISMA guidelines, including original studies published between 2019 and 2024 in PubMed, Scopus, Web of Science, and Embase databases. Eligible studies applied CFD to human saccular aneurysms addressing rupture or growth. Exclusion criteria comprised stent-assisted treatments, idealized or phantom models, and non-human or in vitro analyses. Extracted data included study characteristics, CFD software, meshing and solver approaches, and reported parameters. Results: Thirty-five studies met the eligibility criteria. Commercial software predominated across the segmentation, meshing, and solver stages. The most frequently evaluated wall shear stress metrics were the oscillatory shear index (OSI, 91.43%), time-averaged wall shear stress (TAWSS, 71.43%), low shear area ratio (LSAR, 60.00%), normalized wall shear stress (NWSS, 51.43%), and relative residence time (RRT, 45.71%). Morphological parameters such as the aspect ratio (AR, 74.29%), size ratio (SR, 68.57%), and volume (42.86%), reflecting aneurysm shape and relative size, were the most consistently evaluated and demonstrated strong associations with rupture and growth. Conclusions: A core set of morphological and hemodynamic parameters (AR, SR, TAWSS, OSI, RRT, and LSAR) was consistently identified as potential discriminators for the rupture and growth of intracranial aneurysms. However, substantial methodological heterogeneity and the absence of unified standards hinder reproducibility and clinical translation. Future research must urgently standardize computational frameworks, parameter definitions, and boundary conditions to enhance the consistency, comparability, and clinical applicability of CFD in aneurysm risk assessment. Full article

Background/Objectives: Deep cerebral vein thrombosis (DCVT) is a rare cerebrovascular condition that can result in absence of major venous sinuses. This study uses patient-specific computational fluid dynamics (CFD) to quantify hemodynamic changes in acquired DCVT, focusing on venous outflow redistribution, pressure, and wall shear stress (WSS). Methods: Three-dimensional models of cerebral venous sinuses were reconstructed from magnetic resonance venography (MRV) for a DCVT patient and normal control. Steady-state CFD simulations used physiological inflows with laminar flow assumptions. Sensitivity analyses tested hyperemic conditions and blood rheology effects. Results: In normal anatomy, flow split 70% through superior sagittal sinus and 30% through straight sinus. In DCVT, all flow was rerouted through the superior sagittal sinus. Surprisingly, pressure drop was lower in DCVT (0.67 mmHg vs. 1.3 mmHg in normal). WSS increased moderately in the DCVT superior sagittal sinus (~2.5 Pa peak) but remained within physiological ranges. Under hyperemic conditions, pressures and WSS stayed below pathological thresholds. Conclusions: DCVT redirects venous outflow without pathological pressure or WSS elevations, demonstrating remarkable venous system resilience through collateral compensation. This patient-specific CFD framework enables individualized hemodynamic assessment, contributing to personalized medicine approaches for rare cerebrovascular conditions. Full article

Wellbore liquid loading is a major issue in the later stages of gas well development, particularly for low-permeability gas fields such as shale gas and tight gas, severely affecting the normal production of gas wells. Accurately predicting the onset of wellbore liquid loading and implementing preventive measures are crucial for ensuring the normal production of gas fields. Therefore, based on the gas–liquid-carrying mechanism in gas wellbores and the flow patterns of gas–liquid two-phase flow in inclined wells, the criterion for gas critical liquid-carrying is determined by the shear stress between the liquid film and the pipe wall being zero. By considering the relative velocity between gas and liquid phases, porosity, and the distribution of velocity across the cross-section through the gas–liquid momentum balance equations, a gas critical liquid-carrying velocity model based on the drift model is established. Field data are used to compare the proposed model with four existing liquid-loading prediction models using the misjudgment rate, mean relative percentage error, and mean absolute percentage error as evaluation metrics for model accuracy. The results show that the proposed model outperforms the other models, with a misjudgment rate of 2.99%, mean relative percentage error of 3.83%, and mean absolute percentage error of 4.12%. Full article

This paper investigates the mechanical behavior of PBL shear connectors in UHPC during the elastic stage, utilizing push-out experiments and numerical simulation. This study simplifies the mechanical behavior of PBL shear connectors in UHPC under normal service conditions as a plane strain problem for the UHPC dowel and a Winkler’s Elastic foundation beam theory for the transverse reinforcement. The UHPC dowel is a thick-walled cylindrical shell subjected to non-axisymmetric loads inside and outside simultaneously in the plane-strain state. The stress solution is derived by assuming the contact stress distribution function and using the Airy stress function. The displacement solution is subsequently determined from the stresses by differentiating between elastic and rigid body displacements. By modeling the transverse reinforcement as an infinitely long elastic foundation beam, its displacement solution and stress solution are obtained. We obtain the load–slip curve calculation method by superimposing the displacement of UHPC with the transverse reinforcement in the direction of shear action. The proposed analytical solutions for stress and slip, as well as the method for calculating load–slip, are shown to be reliable by comparing them to the numerical simulation analysis results. Full article

Meissner’s corpuscles are essential mechanoreceptors that detect low-frequency vibrations. However, the internal fluid dynamic processes that convert directional mechanical stimuli into neural signals are not yet fully understood. This study aims to clarify the direction-specific sensing mechanism by analyzing internal fluid flow and shear stress distribution under different vibration modes. A biomimetic microfluidic platform was developed and coupled with a dynamic mesh computational fluid dynamics (CFD) model to simulate the response of the corpuscle to 20 Hz normal and tangential vibrations. The simulation results showed clear differences in fluid behavior. Normal vibration produced localized vortices and peak wall shear stress greater than 0.0054 Pa along the short axis. In contrast, tangential vibration generated stable laminar flow with a lower average shear stress of about 0.0012 Pa along the long axis. These results suggest that the internal structure of the Meissner corpuscle is important for converting mechanical inputs from different directions into specific fluid patterns. This study provides a physical foundation for understanding mechanotransduction and supports the design of biomimetic sensors with improved directional sensitivity for use in smart skin and soft robotic systems. Full article

A simple analytic procedure for the linear static analysis of short thin-walled beams with monosymmetric open cross-sections subjected to eccentric axial loading is presented. Under eccentric compressive loading, the beam is subjected to compression/extension, to torsion with influence of shear with respect to the principal pole and to bending with influence of shear in two principal planes. The approximate closed-form solutions for displacements consist of the general Vlasov’s solutions and additional displacements due to shear according to the theory of torsion with the influence of shear, as well as the theory of bending with the influence of shear. The internal forces and displacements for beams clamped at one end and simply supported on the other end, where eccentric loading is acting, are calculated using the method of initial parameters. The shear coefficients for the monosymmetric cross-sections introduced in these equations are provided. Solutions for normal stress and total displacements according to Vlasov’s general thin-walled beam theory, and those obtained with the proposed method taking shear influence into account, are compared with shell finite element solutions analyzing isotropic and orthotropic I-section beams. According to the results for normal stress relative differences, and Euclidean norm for displacements, it has been demonstrated that shear effects must be accounted for in the analysis of such structural problems. Full article

The increased use of prefabricated assembly technology promotes the transformation of urban subway construction in the lightweight direction, in which the closed cavity thin-walled component is increasingly widely used in underground structures due to its excellent material efficiency benefits. In order to investigate the effect of closed cavity thin-walled components, numerical models of a seven-ring solid structure and cavity structure were constructed based on the four-block prefabricated metro station of Qingdao Metro Line 9, Chengzi Station. This study considers the longitudinal effect between rings and compares the nonlinear force and deformation characteristics of both structures under the load of self-weight and use stage. The study indicates that incorporating closed cavities within structures reduces internal forces in most sections while increasing principal strain, displacement, and stress. As the applied load increases, the rate of internal force reduction diminishes, and the increment of displacement deformation also decreases. Shear lag effects occur in closed cavity sections, leading to a non-uniform normal stress distribution, with maximum shear stress appearing at rib intersections. The cavity location, mortise–tenon joints, and columns represent critical locations for deformation and force transmission within cavity structures. Optimization design must prioritize ensuring their deformation resistance and load-bearing capacity to enhance the overall structural integrity, safety, and reliability. Full article