Shear Stress Research Articles

Effect of stent struts angle on body vessel shear stress at different heat fluxes

Effect of stent struts angle on body vessel shear stress at different heat fluxes

Turbulent flow in a transitional rough pipe universal laws; Power law velocity with equivalent log law velocity in the overlap region: Commencing from fully smooth pipe flow

Abstract The turbulent transitional rough pipe universal power law and equivalent log law are, independent of wall roughness, without any closure model. The open Reynolds mean momentum equations are employed without closure models such as eddy viscosity or mixing length . That all components of Reynolds stress are of same order of the wall shear stress, τw. The key parameters are wall roughness scale ϕ, roughness friction Reynolds number Rτϕ = Reτ/ϕ, and roughness average Reynolds number Rbϕ=Reb/ϕ. The s three layers (inner, meso, and outer), with overlap region reveals dual solutions: power law and log law . The power law friction factor can be expressed as λ=(CS,n,Re/ϕ). The power law index n and prefactor CS remain as fully smooth pipe power law constants and do not depend on the roughness friction Reynolds number Reτ/ϕ. The power law velocity and friction factor exhibit envelopes where the tangent at a point Reτ/ϕ = exp(α−1−κB) yields equivalent log laws. If outer layer is neglected, the power law friction factor simplifies to λ=CS(Re/ϕ)−n. As an engineering approximation, the power laws fr are extrapolated within a ± 5 percent domain, a limited range of Reynolds numbers with experimental and DNS data. Additionally, log law theory for transitional rough pipe is extended to higher-order effects (Reτ/ϕ)−p, where p = 1, 2, …,∞. The power law and log law work comparison were made with turbulent transitional experimental and DNS data.

Active and inactive contributions to the wall pressure and wall-shear stress in turbulent boundary layers

Active and inactive contributions to the wall pressure and wall-shear stress in turbulent boundary layers

One-step bioprinting of endothelialized, self-supporting arterial and venous networks.

Advances in biofabrication have enabled the generation of freeform perfusable networks mimicking vasculature. However, key challenges remain in the effective endothelialization of these complex, vascular-like networks, including cell uniformity, seeding efficiency, and the ability to pattern multiple cell types. To overcome these challenges, we present an integrated fabrication and endothelialization strategy to directly generate branched, endothelial cell-lined networks using a diffusion-based, embedded 3D bioprinting process. In this strategy, a gelatin microparticle sacrificial ink delivering both cells and crosslinkers is extruded into a crosslinkable gel precursor support bath. A self-supporting, perfusable structure is formed by diffusion-induced crosslinking, after which the sacrificial ink is melted to allow cell release and adhesion to the printed lumen. This approach produces a uniform cell lining throughout networks with complex branching geometries, which are challenging to uniformly and efficiently endothelialize using conventional perfusion-based approaches. Furthermore, the biofabrication process enables high cell viability (>90%) and the formation of a confluent endothelial layer providing vascular-mimetic barrier function and shear stress response. Leveraging this strategy, we demonstrate for the first time the patterning of multiple endothelial cell types, including arterial and venous cells, within a single arterial-venous-like network. Altogether, this strategy enables the fabrication of multi-cellular engineered vasculature with enhanced geometric complexity and phenotypic heterogeneity.

Numerical investigation of shear stress in buildings reinforced by walls without corner columns

Numerical investigation of shear stress in buildings reinforced by walls without corner columns

The role of fluid friction in streamer formation and biofilm growth

Biofilms constitute one of the most common forms of living matter, playing an increasingly important role in technology, health, and ecology. While it is well established that biofilm growth and morphology are highly dependent on the external flow environment, the precise role of fluid friction has remained elusive. We grew Bacillus subtilis biofilms on flat surfaces of a channel in a laminar flow at wall shear stresses spanning one order of magnitude (τw = 0.068 Pa to τw = 0.67 Pa). By monitoring the three-dimensional distribution of biofilm over seven days, we found that the biofilms consist of smaller microcolonies, shaped like leaning pillars, many of which feature a streamer in the form of a thin filament that originates near the tip of the pillar. While the shape, size, and distribution of these microcolonies depend on the imposed shear stress, the same structural features appear consistently for all shear stress values. The formation of streamers occurs after the development of a base structure, suggesting that the latter induces a secondary flow that triggers streamer formation. Moreover, we observed that the biofilm volume grows approximately linearly over seven days for all shear stress values, with a growth rate inversely proportional to the wall shear stress. We develop a scaling model, providing insight into the mechanisms by which friction limits biofilm growth.

Improving rupture status prediction for intracranial aneurysms using wall shear stress informatics

BackgroundWall shear stress (WSS) plays a crucial role in the natural history of intracranial aneurysms (IA). However, spatial variations among WSS have rarely been utilized to correlate with IAs’ natural history. This study aims to establish the feasibility of using spatial patterns of WSS data to predict IAs’ rupture status (i.e., ruptured versus unruptured).Methods“Patient-specific” computational fluid dynamics (CFD) simulations were performed for 112 IAs; each IA’s rupture status was known from medical records. Recall that CFD-simulated hemodynamics data (wall shear stress and its derivatives) are located on unstructured meshes. Hence, we mapped WSS data from an unstructured grid onto a unit disk (i.e., a uniformly sampled polar coordinate system); data in a uniformly sampled polar system is equivalent to image data. Mapped WSS data (onto the unit disk) were readily available for Radiomics analysis to extract spatial patterns of WSS data. We named this innovative technology “WSS-informatics” (i.e., using informatics techniques to analyze WSS data); the usefulness of WSS-informatics was demonstrated during the predictive modeling of IAs’ rupture status.ResultsNone of the conventional WSS parameters correlated to IAs’ rupture status. However, WSS-informatics metrics were discriminative (p-value < 0.05) to IAs’ rupture status. Furthermore, predictive models with WSS-informatics features could significantly improve the prediction performance (area under the receiver operating characteristic curve [AUROC]: 0.78 vs. 0.85; p-value < 0.01).ConclusionThe proposed innovations enabled the first study to use spatial patterns of WSS data to improve the predictive modeling of IAs’ rupture status.

Mechanical properties and macro–micro failure mechanisms of granite under thermal treatment and inclination

The coupling effects of inclination angle (θ) and high temperature (T) on rock degradation present significant construction challenges for underground engineering projects, such as underground coal gasification, inclined mining pillars, and nuclear waste repositories. This study is built on a novel combined compression and shear test system, investigating granite’s physical and mechanical properties and macroscopic failure characteristics under varying temperatures and inclination angles. Additionally, acoustic emission technology was used to analyze the impact of inclination and temperature on the micro-failure behavior of the specimens. The experimental results indicate that as the inclination angle increases, the specimens’ peak compressive strength and elastic modulus decrease linearly. In contrast, the shear stress increases non-linearly, suggesting that additional shear stress accelerates the initiation and propagation of cracks. Furthermore, these mechanical parameters initially increase with rising temperatures before decreasing, with a temperature threshold identified at 400 °C. The effect of inclination angle on the failure mode of the specimens is more pronounced than that of temperature; as the inclination angle increases, the failure mode transitions from splitting failure to shear failure at any given temperature. Acoustic emission results reveal that the specimens’ microcrack initiation (CI) and damage (CD) thresholds reduce with increasing inclination, while the corresponding shear stress increases. As temperature rises, the CI and CD thresholds exhibit an initial increase attended by a decrease. Finally, founded on the experimental findings, a multivariate equation was established to accurately predict the peak compressive strength and elastic modulus about θ and T. The results of this study provide valuable insights and references for the construction of underground thermal engineering under complex conditions.

Adhesive nonlinearity analysis of longitudinal guided wave using circumference pasted piezoelectric array based nonlinear shear stress lag model

The adhesive layer between an ultrasonic transducer and a circular tube can generate a nonlinear signal during guided wave excitation and reception, which is called adhesive nonlinearity (AN). It may override the damage-related signals and result in false detection if not adequately evaluated and mitigated. This study investigated the AN of the guided wave excitation model composed of a piezoelectric array in a circular tube structure. The classical shear stress lag model was extended to the circumference pasted piezoelectric array-based nonlinear shear stress lag model to investigate the coupling properties of the AN and to evaluate the AN by comparing it with other nonlinear factors within a circular tube structure. On this basis, the nonlinear shear stress was combined with the normal mode expansion to establish a frequency tuning model for the AN, which allowed the effect of the AN to be minimized by adjusting the half-wavelength of the guided wave to match the length of the actuator. Finite-element analyses and experiments validated the tuning characteristics of the AN mentioned above. This work was used to mitigate the effect of the AN on the nonlinear guided wave during thermal damage evaluation.

The Lift Enhancement Effect of a New Fluidic Oscillator on High-Lift Wings

Fluidic oscillators have emerged as a prominent topic of research in the field of flow control, owing to their broad sweep range and enhanced control efficiency. However, the underlying mechanisms governing the operation of fluidic oscillators remain poorly understood, and the effect of oscillation frequency on flow control performance has yet to be conclusively determined. In this study, a novel fluidic oscillator is proposed that achieves frequency decoupling by replacing the conventional feedback channel with synthetic jets, thereby enabling modulation of oscillation frequency at a constant momentum coefficient. When applied to a high-lift airfoil, results show that at a momentum coefficient of 14.1%, the lift coefficient increase achieved under F+ = 1 control outperforms that under F+ = 10 by more than 0.3. This finding suggests the presence of an optimal frequency for fluidic oscillators, which maximizes their flow control effectiveness. Notably, this optimal frequency is unaffected by variations in the momentum coefficient. A deeper analysis of the fluidic oscillator’s working principle reveals that periodic oscillations dominate the turbulent kinetic energy and Reynolds shear stress, driving enhanced chordwise momentum exchange. This increased energy transfer strengthens the boundary layer’s resistance to separation, effectively mitigating flow detachment and improving lift enhancement. Finally, the periodic flow field on the surface of the high-lift airfoil under fluidic oscillator control was examined. It was observed that, at low frequencies, the fluidic oscillator effectively controls the shedding of separation vortices, ensuring that the frequency of vortex shedding aligns with the oscillation frequency of the fluidic oscillator. This alignment likely contributes to the superior lift enhancement observed under low-frequency conditions.

Convective forces contribute to post‐traumatic degeneration after spinal cord injury

AbstractSpinal cord injury (SCI) initiates a complex cascade of chemical and biophysical phenomena that result in tissue swelling, progressive neural degeneration, and formation of a fluid‐filled cavity. Previous studies show fluid pressure above the spinal cord (supraspinal) is elevated for at least 3 days after injury and contributes to a phase of damage called secondary injury. Currently, it is unknown how fluid forces within the spinal cord itself (interstitial) are affected by SCI and if they contribute to secondary injury. We find spinal interstitial pressure increases from −3 mmHg in the naive cord to a peak of 13 mmHg at 3 days post‐injury (DPI) but relatively normalizes to 2 mmHg by 7 DPI. A computational fluid dynamics model predicts interstitial flow velocities up to 0.9 μm/s at 3 DPI, returning to near baseline by 7 DPI. By quantifying vascular leakage of Evans Blue dye after a cervical hemi‐contusion in rats, we confirm an increase in dye infiltration at 3 DPI compared to 7 DPI, suggestive of higher fluid velocities at the time of peak fluid pressure. In vivo expression of the apoptosis marker caspase‐3 is strongly correlated with regions of interstitial flow at 3 DPI, and exogenously enhancing interstitial flow exacerbates tissue damage. In vitro, we show overnight exposure of neuronal cells to low pathological shear stress (0.1 dynes/cm2) significantly reduces cell count and neurite length. Collectively, these results indicate that interstitial fluid flow and shear stress may play a detrimental role in post‐traumatic neural degeneration.

Wall slip and bulk flow heterogeneity in a sludge under shear

Abstract We investigate the shear flow of a sludge mimicking slurries produced by the nuclear industry and constituted of a dispersion of non-Brownian particles into an attractive colloidal dispersion at a total solid volume fraction of about 10 %. Combining rheometry and ultrasound flow imaging, we show that, upon decreasing the shear rate, the flow transitions from a homogeneous shear profile in the bulk to a fully arrested plug-like state with total wall slip, through an oscillatory regime where strong fluctuations of the slip velocity propagate along the vorticity direction. When the shear stress is imposed close to the yield stress, the shear rate presents large, quasi-periodic peaks, associated with the propagation of local stick-and-slip events along the vorticity direction. Such complex dynamics, reminiscent of similar phenomena reported in much denser suspensions, highlight the importance of local flow characterization to fully understand sludge rheology.

Quantifying Anisotropic Properties of Old–New Concrete Interfaces Using X-Ray Computed Tomography and Homogenization

The interface between old and new concrete is a critical component in many construction practices, including concrete pavements, bridge decks, hydraulic dams, and buildings undergoing rehabilitation. Despite various treatments to enhance bonding, this interface often remains a weak layer that compromises overall structural performance. Traditional design methods typically oversimplify the interface as a homogeneous or empirically adjusted factor, resulting in significant uncertainties. This paper introduces a novel framework for quantifying the anisotropic properties of old–new concrete interfaces using X-ray computed tomography (CT) and finite element-based numerical homogenization. The elastic coefficient matrix reveals that specimens away from the interface exhibit higher values in both normal and shear directions, with normal direction values averaging 33.15% higher and shear direction values 39.96% higher than those at the interface. A total of 10 sampling units along the interface were collected and analyzed to identify the “weakest vectors” in normal and shear directions. The “weakest vectors” at the interface show consistent orientations with an average cosine similarity of 0.62, compared with an average cosine similarity of 0.23 at the non-interface, which demonstrates directional features. Conversely, the result of average cosine similarity at the interface shows randomness that originates from the anisotropy of materials. The average angle between normal and shear stresses was found to be 88.64°, indicating a predominantly orthogonal relationship, though local stress distributions introduced slight deviations. These findings highlight the importance of understanding the anisotropic properties of old–new concrete interfaces to improve design and rehabilitation practices in concrete and structural engineering.

Effect of Load Vector Orientation on Uniaxial Compressive Strength of 3D Photoresin

Rapid prototyping has a wide range of applications across various fields, both in industry and for private use. It enables the production of individual parts in a short time, independent of supply chains, which is particularly important in remote locations. Among all 3D printing technologies, stereolithography using photo resins is the most accessible and offers the highest printing quality. However, the strength properties of parts made from photo resins remain a critical concern. In this study, we conducted experimental research to investigate the effect of load vector orientation under uniaxial compression on the elastic and mechanical properties of 3D-printed cylindrical samples. The results revealed that samples with layers oriented at 60° to the load vector exhibited the highest strength, while those with layers at 30° to the load vector showed the lowest strength. Samples with layers aligned parallel or perpendicular to the load vector demonstrated similar strength properties. Under quasi-elastic loading, samples with layers parallel to the load vector exhibited the highest Young’s modulus and the lowest Poisson’s ratio. Conversely, samples with layers oriented at 30° to the load vector displayed the highest Poisson’s ratio. Microstructural analysis revealed that the anisotropy in the mechanical properties of the 3D-printed samples is attributed to the layered, heterogeneous structure of the photoresin, which exhibits varying degrees of polymerization along the printing axes. The upper part of each layer, with a lower degree of polymerization, contributes to the ductile behavior of the samples under shear stresses. In contrast, the lower part of the layer, with a higher degree of polymerization, leads to brittle behavior in the samples.

Rheology of Bingham viscoplastic flow triggered by a rotating and radially stretching disk

Purpose This study aims to investigate the flow and heat transfer characteristics of a Bingham viscoplastic fluid subjected to the combined effects of axial rotation and radial stretching of a circular disk. Building upon existing models for Bingham fluids on stationary walls, we extend the formulation to incorporate the effects of a linearly stretching disk using von Kármán similarity transformations. Design/methodology/approach The resulting system of nonlinear ordinary differential equations is solved to characterize the flow and thermal fields. Three dimensionless parameters govern the momentum layer: a swirling number capturing the balance between rotation and stretching, a Bingham number characterizing the fluid’s yield stress and a modified Reynolds number incorporating the disk stretching. The Prandtl number controls the thermal response. Findings For purely stretching flows, a two-dimensional flow structure emerges. However, the introduction of rotation induces three-dimensional flow behavior. Unlike previous studies suggesting that moderate Bingham numbers are sufficient for non-Newtonian effects on purely revolving disks, the findings indicate that significantly higher yield stresses are required to observe non-Newtonian characteristics under radial stretching conditions. This difference can be attributed to the enhancing influence of wall movement on the fluid dynamics. At high Bingham numbers, a two-layer flow structure develops, comprising an unyielded plug region above the disk and a yielded shear layer adjacent to the wall. The von Kármán viscous pump mechanism drives the Bingham flow within this regime. Originality/value Physical quantities such as drag force due to wall shear stress, torque resulting from tangential shear stress and Nusselt number are extracted from the quantitative data.

A Mathematical Approach to the Buckling Problem of Axially Loaded Laminated Nanocomposite Cylindrical Shells in Various Environments

In this study, the solution of the buckling problem of axially loaded laminated cylindrical shells consisting of functionally graded (FG) nanocomposites in elastic and thermal environments is presented within extended first-order shear deformation theory (FOST) for the first time. The effective material properties and thermal expansion coefficients of nanocomposites in the layers are computed using the extended rule of mixture method and molecular dynamics simulation techniques. The governing relations and equations for laminated cylindrical shells consisting of FG nanocomposites on the two-parameter elastic foundation and in thermal environments are mathematically modeled and solved to find the expression for the axial buckling load. The numerical results of the current analytical approach agree well with the existing literature results obtained using a different methodology. Finally, some new results and interpretations are provided by investigating the influences of different parameters such as elastic foundations, thermal environments, FG nanocomposite models, shear stress, and stacking sequences on the axial buckling load.

Plantar pressure and shear stress during gait in people with diabetic neuropathy

Plantar pressure and shear stress during gait in people with diabetic neuropathy

Interaction mechanism of dislocations with Bi/hBN nanoparticles in free-cutting steels: molecular dynamics simulations

Abstract To further understand the mechanical properties of free-cutting steels, we employed molecular dynamics (MD) simulations to investigate the interaction mechanisms between dislocation slip along close-packed planes and nano-inclusion particles (Bi/h-BN) within single-crystal iron (Fe). By colliding dislocations at varying slip velocities with nanometer-scale particles of different sizes and compositions, we concluded that particle diameter plays a decisive role not only in determining the dislocation cutting mode but also in influencing the dislocation’s shear stress response. These indicate that: Larger particles significantly enhance the strengthening effect on the matrix. Additionally, higher dislocation slip velocities result in stronger particle interaction feedback and greater particle damage, contributing to increased matrix deformation. h-BN particles, owing to their much higher hardness compared to Bi, exhibited superior resistance to deformation, requiring higher dislocation shear stress to pass these obstacles.

Shear viscosity of electrorheological complex plasmas

Abstract In this paper, we investigate the behavior of shear viscosity for three-dimensional electrorheological complex plasmas (CPs) liquids by using the computational method (molecular dynamics simulations) under an external AC electric field (M T ). The Green–Kubo formula is used to calculate the shear stress autocorrelation function (A η (t)) and their integrals (coefficients, η) under the influence of M T , across numerous values of CPs parameters. By comparing the presented simulation results obtained under the absence of M T (=0.0) and at equilibrium strength (M T = 0.007), we analyze and discuss their implications in relation to existing theoretical, simulation, and experimental findings. Our observations demonstrate that the M T significantly influences the shear viscosity (dynamics) of CPs. Simulation results demonstrated that decay, magnitude, and time of A η (t) gradually decreased with increasing the M T , and coefficients η increased in the order of magnitude as expected. These results identified three distinct regimes: a slight decrease in η at low M T intensities, high increase at intermediate, and a relatively constant behavior at higher M T intensities. We demonstrate that employing the Green–Kubo relation for effective interparticle potential in CPs yields safe, reliable, and accurate estimations of M T effects on shear viscosity. Our findings of η demonstrate the electrorheological characteristics of CPs, offering insights into phase transitions using electric fields.

Analytical modeling of thermomechanical stresses in short hyperelastic tubes under axial and torsional loading

Abstract This study introduces an analytical model for analyzing thermomechanical stresses in finite-length hyperelastic hollow cylinders under axial-torsional loading and non-isothermal conditions. The model incorporates an axial temperature distribution and decomposes strain responses into thermal expansion and mechanical stretches. Governing equations are derived using large deformation kinematics and the Neo-Hookean strain energy function. Solutions for displacements, stresses, and pressure variables are obtained with appropriate boundary conditions. Validation against 3D finite element analysis demonstrates strong agreement with significant computational cost savings. These findings challenge the conventional linear assumption for twist angles under large deformations. Increasing temperature differences introduce noticeable nonlinearities in radial and axial stress distributions, resulting in significant nonlinear axial stress distributions along the vertical walls. Additionally, higher temperature differences reduce axial stress at the inner radius, while shear stresses predominantly remain radial with minimal variation. In summary, this efficient analytical tool provides invaluable insights into thermomechanical stresses in soft active cylindrical components, with broad potential applications across various fields.