Shear Stress Research Articles

Exploring submergence impact on flow-induced motion energy-harvesting with circular-triangular prisms

AbstractRecent advancements in energy-harvesting have utilized Flow-Induced Motion (FIM) as a renewable source, diverging from past efforts aimed at minimizing FIM's adverse effects. This study introduces kinetic energy converters using alternating lift technology (ALT), employing a prism with a Circular-Triangular (Cir-Tria) shape, coupled with a spring and damper, to generate energy. Utilizing computational fluid dynamics in OpenFOAM for Reynolds numbers between 2 × 103 and 13 × 103 and varying submergence depth ratio from 0.98 to 5.91, this research employs a moving computational grid, two-dimensional incompressible Navier–Stokes equations, the k-omega Shear Stress Transport (SST) turbulence model, the Volume of Fluid, VOF, two-phase model, and the cylinder mass–spring–damper equation. Findings show that approaching the flow surface negatively impacts the FIM response due to the interaction of vortices from the flow surface and the prism’s upper shear layer. This interaction weakens and neutralizes the upper vortices, altering the flow structure around the prism and the governing FIM phenomena. Proximity to the free surface significantly affects FIM responses, with a notable decrease in vibration amplitude and energy conversion as the submergence depth ratio increases from 0.98 to 5.91. Maximum system efficiency of 1.4% is observed in the VIV initial branch at infinite submergence (single-phase flow). Beyond a submergence depth ratio of 5.91, FIM amplitude and energy conversion flatten, indicating negligible free surface effects.

ENHANCING MECHANICAL RELIABILITY OF SILVER SINTERED JOINTS WITH COPPER NANOWIRES IN HIGH-POWER ELECTRONIC DEVICES

Abstract This study investigated the mechanical reliability of silver-sintered die attachment under harsh operating conditions, and explored the advantages of adding copper nanowires to improve the bond's mechanical properties. Samples were prepared using a template-assisted electrochemical deposition process to coat the substrate surface with copper nanowires, and were subjected to thermal aging at various temperatures to assess their mechanical reliability. Results showed that the incorporation of copper nanowires in the substrate interface significantly reduced degradation in shear strength as a result of thermal aging, acting as mechanical reinforcement and improving the interfacial resilience against mechanical shear stress. The addition of copper nanowires also reduced the void formation in the thermal aging, resulting in a more robust and reliable bond. The study demonstrates the potential of using copper nanowires as a reinforcing agent to enhance the mechanical properties of silver-sintered die attachment, particularly for high-temperature applications.

Magnetohydrodynamic Motions of Oldroyd-B Fluids in Infinite Circular Cylinder That Applies Longitudinal Shear Stresses to the Fluid or Rotates Around Its Axis

Two classes of magnetohydrodynamic (MHD) motions of the incompressible Oldroyd-B fluids through an infinite cylinder are analytically investigated. General expressions are firstly established for shear stress and velocity fields corresponding to the motion induced by longitudinal shear stress on the boundary. For validation, the expression of the shear stress is determined by two different methods. Using an important remark regarding the governing equations for shear stress and fluid velocity corresponding to the two different motions, this expression is then used to provide the dimensionless velocity field of the MHD motion of the same fluids generated by a cylinder that rotates around its symmetry axis. Obtained results can generate exact solutions for any motion of this kind of Oldroyd-B fluids. Consequently, both types of motions are completely solved. For illustration, some case studies are considered, and adequate velocity fields are provided. The steady-state components of these velocities are presented in different forms whose equivalence is graphically proved. The influence of the magnetic field on the fluid behavior is graphically investigated. It was found that the fluid flows slower, and a steady state is earlier reached in the presence of a magnetic field. The fluid behavior when shear stress is given on the boundary is also investigated.

Effect of Hydrodynamic Shear Stress on Algal Cell Fate in 3D Extrusion Bioprinting

The 3D bioprinting of aquatic photosynthetic organisms holds potential for applications in biosensing, wastewater treatment, and biofuel production. While algae cells can be immobilized in bioprinted cell‐friendly matrices, there is a knowledge gap regarding the thresholds of hydrodynamic shear stress that affect the cells’ functionality and viability during bioprinting. This study examines the effect of hydrodynamic shear stress on the fate of Chlamydomonas reinhardtii cells. Computational fluid dynamics models based on the Navier–Stokes equations are developed to numerically predict the shear stresses experienced by the cells during extrusion. Parallelly, cell culture experiments are conducted to evaluate the functionality, growth rates, and viability of algae cells within bioprinted constructs. By correlating cell culture and simulation results, the causal link between shear stress in the nozzle and cell viability and function has been characterized. The findings highlight that cell viability and function are significantly impacted by process factors. Notably, algae cell function is more sensitive to shear stress than cell viability. Functional impairments occur at maximum shear stresses around 5 kPa, while viability remains unaffected. Beyond 14 kPa, both functionality and viability decline significantly and irreversibly. The results emphasize the importance of assessing viability and function after bioprinting, rather than just viability.

A Novel Bladeless-Spinal Wind Turbine Design for Efficient Energy Generation in Low wind Speeds

Wind energy is a widely used and renewable source for electricity generation. However, traditional wind turbines face challenges such as large footprints, noise, high costs, and efficiency limitations. To address these issues, bladeless wind turbines (BWTs) have gained popularity, and extensive research is being carried out to develop efficient designs. In this work, we propose a novel BWT design, inspired by the spine structure found in human bodies. The BWT architecture is modular, autonomous, and robust, making it suitable for small, portable, and small-scale applications. Our BWT design was inspired by the spine structure found in the human body and other vertebrates. The BSWT architecture is modular, autonomous, and robust. Detailed 3D models were created using Fusion 360 and SolidWorks software to refine and iterate the design. Our BWT features a complete electrical system with an energy harvesting base, a rectifier, converter, and a storage battery. The stored energy is then converted to AC and connected to the load. Our design utilizes oscillating rods divided into sections, enabling energy generation even at low wind speeds. The casing protects the rods from shear stresses and corrosion. While practical applicates involve a spine design with multiple sections, our experiments primarily focus on a single turbine.

An Experimental Study and Result Analysis on the Dynamic Effective Bond Length of a Carbon Fiber-Reinforced Polymer Sheet Attached to a Concrete Surface

A carbon fiber-reinforced polymer (CFRP) is a common material utilized for the enhancement in reinforced concrete (RC) constructions. Previous research indicates that the bonding performance between a CFRP sheet and concrete determines whether the bonding of CFRP material is effective. However, the majority of existing research on the bonding performance of the CFRP–concrete interface is concentrated on static loading conditions. In order to clarify the effect of dynamic load on the bonding performance of the CFRP sheet–concrete interface, this study adopts the double-sided shear test method to carry out dynamic experimental research. The test findings reveal that the damage pattern of the CFRP sheet–concrete interface remains consistent across different loading rates. The ultimate bearing capacity increases as the strain rate increases. As the strain rate increases from 10−5 s−1 to 10−2 s−1, the effect of bond length on ultimate bearing capacity increases by about 7%. As the strain rate increases, both the maximum strain of CFRP and the maximum interfacial shear stress demonstrate a corresponding increase, with respective increase rates of 60% and 20%. The effective bond length decreases by about 20% when the strain rate rises from 10−5 s−1 to 10−2 s−1. Finally, a formula for calculating the dynamic effective bond length of a CFRP sheet, grounded in the Chen and Teng formula, has been proposed and verified.

Microstructure, thermal, and mechanical properties of hierarchical porous silicon carbide made by direct ink writing

AbstractHierarchical porous silicon carbide (SiC) ceramics were fabricated by combining particle‐stabilized emulsions and three‐dimensional (3D) printing. Direct ink writing (DIW) was used as the 3D printing technique. The formulation for successful printing is discussed in relation to the rheology of the emulsions. The SiC emulsions were able to be printed with a lower storage modulus (G′) and apparent yield shear stress (τy) than previously reported SiC ink pastes. The printed and sintered porous SiC ceramics possess a total porosity of 73.7% with an average pore size within the filaments of 2.2 µm in diameter. A hierarchical pore structure that contains pore sizes of about 250 µm, around 1–10 µm and smaller than 0.5 µm can be observed in the microstructure and pore size distribution. The mechanical properties showed a good strength‐to‐density ratio, and the thermal conductivity was reduced to 4.9 W/m·K. This study provides a new reliable approach for fabricating hierarchical porous SiC ceramics with low thermal conductivity.

First Principles Variational Formulation and Analytical Solutions for Third Order Shear Deformable Beams with Simple Supports using Fourier Series Method

The Fourier series method for solving bending problems of third-order shear deformable beams (TSBD) is presented in this paper. The theory accounts for transverse shear deformation and is suitable for moderately thick beams. Transverse shear stress-free conditions are valid at the beam surfaces for TSDB. The field equations are two coupled ordinary differential equations in terms of two unknown displacement functions – transverse deflection w(x) and warping function For simply supported ends considered, the loading and unknown functions w(x) and are represented in Fourier series that satisfies the boundary conditions. The problem is reduced to a system of algebraic equations in terms of the Fourier coefficients wn and which is solved to obtain wn and Axial and transverse displacements fields, axial bending stress and transverse shear stress are then determined for the cases of point load at midspan, uniformly and linearly distributed loads over the span. The results are identical with previous results obtained by other scholars who used Ritz variational methods and other mathematical tools. For moderately thick beams under uniform load with l/h = 4, the results obtained for is 0.516% greater than the exact result by Timoshenko and Goodier while for thick beams under uniform load with l/h = 2, the result for is 1.96% greater than the exact result by Timoshenko and Goodier. Similar acceptable variation was obtained for for beams under linearly distributed load with the variations being less than 2% for l/h = 2. However, unacceptable variations of 68.37% were found for in thick beams under point load, for l/h = 2.0. The variation for however reduced to 12.513% for moderately thick beams under point load for l/h =4.

Direct MultiSearch optimization of TPMS scaffolds for bone tissue engineering

BackgroundScaffolds designed for tissue engineering must consider multiple parameters, namely the permeability of the design and the wall shear stress experienced by the cells on the scaffold surface. However, these parameters are not independent from each other, with changes that improve wall shear stress, negatively impacting permeability and vice versa. This study introduces a novel multi-objective optimization framework using Direct MultiSearch (DMS) to design triply periodic minimal surface (TPMS) scaffolds for bone tissue engineering. MethodThe optimization algorithm focused on maximizing the permeability of the scaffolds and obtaining a desired value of average wall shear stress (which ranges between the values that promote osteogenic differentiation of 0.1 mPa and 10 mPa). Multiple fluid inlet velocities and target wall shear stress were analyzed. The DMS method successfully generated Pareto fronts for each configuration, enabling the selection of optimized scaffolds based on specific structural requirements. ResultsThe findings reveal that increasing the target wall shear stress results in a greater number of non-dominated points on the Pareto front, highlighting a more robust optimization process. Additionally, it was also demonstrated that the tested Schwartz diamond scaffolds had a better permeability-wall shear stress relation when compared to Schoen gyroid geometries. ConclusionsDirect MultiSearch was proven as an effective tool to aid in the design of tissue engineering scaffolds. This adaptable optimization framework has potential applications beyond bone tissue engineering, including cartilage tissue differentiation.

Investigation of the Effect of High Shear Stress on Mesenchymal Stem Cells Using a Rotational Rheometer in a Small-Angle Cone-Plate Configuration.

Within the healthy human body, cells reside within the physiological environment of a tissue compound. Here, they are subject to constant low levels of mechanical stress that can influence the growth and differentiation of the cells. The liposuction of adipose tissue and the subsequent isolation of mesenchymal stem/stromal cells (MSCs), for example, are procedures that induce a high level of mechanical shear stress. As MSCs play a central role in tissue regeneration by migrating into regenerating areas and driving regeneration through proliferation and tissue-specific differentiation, they are increasingly used in therapeutic applications. Consequently, there is a strong interest in investigating the effects of shear stress on MSCs. In this study, we present a set-up for applying high shear rates to cells based on a rotational rheometer with a small-angle cone-plate configuration. This set-up was used to investigate the effect of various shear stresses on human adipose-derived MSCs in suspension. The results of the study show that the viability of the cells remained unaffected up to 18.38 Pa for an exposure time of 5 min. However, it was observed that intense shear stress damaged the cells, with longer treatment durations increasing the percentage of cell debris.

Process Controlled Polymorphic Phase Transformation in Crystalline Solid Dispersions: Impact of Temperature, Pressure, and Shear Stress

Process Controlled Polymorphic Phase Transformation in Crystalline Solid Dispersions: Impact of Temperature, Pressure, and Shear Stress

Comprehensive transverse shear stress analysis for FG-GRC sandwich plates based on a refined higher-order zigzag theory

Comprehensive transverse shear stress analysis for FG-GRC sandwich plates based on a refined higher-order zigzag theory

Analytical calculation approach for rocket nose cone structure with orthotropic material

The Authors of this research developed an analytical calculation method to estimate the strength of nose cone structures made of orthotropic materials, which were crucial components in aircraft and spacecraft. Strength analysis of nose cones had been comprehensively addressed for isotropic materials; however, the lack of efficient approaches for orthotropic materials presented a challenge. In this research, a new analytical method was proposed, combining membrane stress theory for isotropic materials with classical laminate theory for orthotropic materials. This approach enabled the determination of stresses on the nose cone shell structure in both meridional and circumferential directions in an efficient and straightforward manner. The analysis results indicated that the developed analytical method exhibited stress distribution trends similar to those obtained using the Finite Element Method. Stresses in the +45° and –45° direction, as well as in-plane shear stress and Tsai-Wu failure indices, showed trend similarity between the two methods. Despite specific numerical differences in the calculation results, these consistent trends suggested that the analytical method could serve as a tool for the preliminary design of a nose cone structure with a similar configuration analyzed in this study.

Simulation of Friction Stir Welding of AZ31 Mg Alloys.

Friction stir welding has been extensively applied for the high-quality bonding of Mg alloys. The welding temperature caused by friction and plastic deformation is essential for determining the joint characteristics, especially the residual stress and weld microstructure. In this work, a modified moving heat source model was proposed by considering the variations in heat generation caused by friction shear stress at both the side and bottom surfaces of the tool. The application of this model was further extended to the entire welding process, especially in the plunging stage. The relative errors between the experimental and simulated peak temperatures at characteristic points were small, with a maximum of 10%, thereby validating the model for accurate temperature prediction. Furthermore, the influence of welding and rotational speed on temperature fields was systematically investigated. At relatively low welding and rotational speeds, the welding temperature increased significantly with either an increase in rotational speed or a decrease in welding speed. However, this effect gradually diminished at higher welding and rotational speeds. These results provide some valuable guidelines for controlling heat generation to improve the quality of Mg alloy welds.

Quiescent cancer cells induced by high-density cultivation reveals cholesterol-mediated survival and lung metastatic traits.

The metastatic cascade, a multifaceted and highly aggressive process, is the primary cause of mortality. The survival of quiescent cancer cells in circulatory system during metastasis is crucial, yet our comprehension is constrained by the absence of universally accepted quiescent cancer models. We developed a quiescent cancer cell model using high-density cultivation. Based on the scRNA-seq analysis, IP-MS, metabolomics, mouse lung metastasis models, cholesterol assay, PLA and other molecular experiments, we explored the molecular mechanism. Immunofluorescence, atomic force microscope, FluidFM, and shear stress stimulation were used to analyze the cytoskeleton and membrane properties contributing to mechanical force resistance. We established a quiescent cancer cell model induced by high-density cultivation. Single-cell RNA sequencing (scRNA-seq) analysis reveals that CDC25A plays a crucial role in the transition to quiescence, with its expression significantly elevated in the quiescent state. Depletion of CDC25A leads to an increased proliferative capacity, and reduced metastasis under high-density conditions. Mechanistically, upregulated CDC25A in quiescent cells enhances cholesterol metabolism via endosome pathways, leading to cell cycle arrest. This increase in cholesterol reinforces the cytoskeleton, alters membrane properties, and improves resistance to mechanical forces in circulatory system. CDC25A significantly increased the cholesterol metabolism through endosome pathway in quiescent cancer cells, leading to the significant changes in cytoskeleton and membrane properties so as to enhance the resistance of mechanical force in circulatory system, facilitating lung metastasis. In high-density cultivation, quiescent cancer cells, up-regulate cholesterol metabolism by CDC25A through endosome pathway, enhancing the resistance to mechanical force in circulatory system, facilitating lung metastasis.

Laser Aggregometry Assessment of Blood Microrheology in a Slit Fluidic Channel Covered With Endothelial Cells.

The blood rheology in vitro in glass or plastic microfluidic chips is different from that in vivo in blood vessels with similar geometry. Absence of vascular endothelium is suggested to cause these discrepancies. This work aims to perform in vitro measurements of blood microrheologic parameters in a slit microfluidic channel covered with endothelial cells (HUVEC). The laser aggregometry was employed to measure the intensity of laser light, backscattered from the blood flow, as a function of shear stress to evaluate the hydrodynamic strength of red blood cells (RBC) aggregates in terms of critical shear stress (CSS). The results demonstrated a decrease in CSS accompanied by an increase in the accuracy of its measurement at similar shear stresses when endothelial cells were present in the channel. The findings hold valuable implications for advanced approaches for endothelization of microfluidic devices, facilitating the study of blood flow dynamics in physiologically more relevant environment.

Intra-Aneurysmal High-Resolution 4D MR Flow Imaging for Hemodynamic Imaging Markers in Intracranial Aneurysm Instability.

Prediction of aneurysm instability is crucial to guide treatment decisions and to select appropriate patients with unruptured intracranial aneurysms (IAs) for preventive treatment. High-resolution 4D MR flow imaging and 3D quantification of aneurysm morphology could offer insights and new imaging markers for aneurysm instability. In this cross-sectional study, we aim to identify 4D MR flow imaging markers for aneurysm instability by relating hemodynamics in the aneurysm sac to 3D morphologic proxy parameters for aneurysm instability. In 35 patients with 37 unruptured IAs, a 3T MRA and a 7T 4D MRI flow scan were performed. Five hemodynamic parameters-peak-systolic wall shear stress (WSSMAX) and time-averaged wall shear stress (WSSMEAN), oscillatory shear index (OSI), mean velocity, and velocity pulsatility index-were correlated to 6 3D morphology proxy parameters of aneurysm instability-major axis length, volume, surface area (all 3 size parameters), flatness, shape index, and curvedness-by Pearson correlation with 95% CI. Scatterplots of hemodynamic parameters that correlated with IA size (major axis length) were created. WSSMAX and WSSMEAN correlated negatively with all 3 size parameters (strongest for WSSMEAN with volume (r = -0.70, 95% CI -0.83 to -0.49) and OSI positively (strongest with major axis length [r = 0.87, 95% CI 0.76-0.93]). WSSMAX and WSSMEAN correlated positively with shape index (r = 0.61, 95% CI 0.36-0.78 and r = 0.49, 95% CI 0.20-0.70, respectively) and OSI negatively (r = -0.82, 95% CI -0.9 to -0.68). WSSMEAN and mean velocity correlated negatively with flatness (r = -0.35, 95% CI -0.61 to -0.029 and r = -0.33, 95% CI -0.59 to 0.007, respectively) and OSI positively (r = 0.54, 95% CI 0.26-0.74). Velocity pulsatility index did not show any statistically relevant correlation. Out of the 5 included hemodynamic parameters, WSSMAX, WSSMEAN, and OSI showed the strongest correlation with morphologic 3D proxy parameters of aneurysm instability. Future studies should assess these promising new imaging marker parameters for predicting aneurysm instability in longitudinal cohorts of patients with IA.

A revisit of the development of viscoplastic flow in pipes and channels

This study revisits the development of viscoplastic flow in pipes and channels, focusing on the flow of a Bingham plastic. Using finite element simulations and the Papanastasiou regularisation, results are obtained across a range of Reynolds and Bingham numbers. The novel contributions of this work include: (a) investigating a definition of the development length based on wall shear stress, a critical parameter in numerous applications; (b) considering alternative definitions of the Reynolds number in an effort to collapse the development length curves onto a single master curve, independent of the Bingham number; (c) examining the patterns of yielded and unyielded regions within the flow domain; and (d) assessing the impact of the regularisation parameter on the accuracy of the results. The findings enhance the existing literature, providing a more comprehensive understanding of this classic flow problem.

Stress analysis and dislocation cluster generation in silicon crystal with artificial grain boundaries

We conducted a dislocation and stress analysis on various grain boundaries (GBs) using silicon ingots that contained artificial GBs to permit systematic comparison of experimental and analytical results. Through photoluminescence imaging, we found that the number of dislocation clusters generated around the 〈110〉-oriented GBs was significantly higher than those around the 〈100〉-oriented GBs. The stress analysis revealed that this difference is linked to the maximum shear stress around the GB. However, there were some GBs where dislocation cluster generation was not observed despite the presence of high shear stress. For most of these GBs, the direction of the maximum shear stress in the 12 slip system of silicon crystal was found to be oblique downward to the growth direction, which appears to inhibit dislocation propagation.

Postseismic deformation due to the 2021 MW 7.4 Maduo (China) earthquake and implications for regional rheology and seismic hazards around the Bayan Har block

GPS and InSAR observations of the first ∼1.5 years of postseismic deformation caused by the 2021 MW 7.4 Maduo earthquake provide a valuable opportunity to investigate fault interactions and regional rheological structure, as well as the future seismic potential around the Bayan Har block, northeastern Tibetan Plateau. We develop an integrated model to simulate the afterslip and viscoelastic relaxation contributions to the observed postseismic displacements, and found that afterslip driven by the coseismic stress is concentrated downdip of rupture, and dominates the postseismic deformation in the early stage (∼0.4 year after the event). Because afterslip decays quickly over time, viscoelastic relaxation should become the main postseismic mechanism as time goes on. The two mechanisms produce similar displacements during 0.4–1.5 years after the earthquake, but at 1.5 years after the earthquake the velocity caused by viscoelastic relaxation is larger than that caused by afterslip. Viscoelastic models assuming either a Burgers body or power-law rheology produce very similar predictions, with the Burgers body model having a slightly lower overall misfit. The rheological structure constrained by the postseismic observations supports the 35-km thick elastic upper crust overlying a Burgers body viscoelastic lower curst with a Maxwell viscosity of 3 × 1019 Pa s (5 - 50 × 1018 Pa s at 95% confidence), assuming the Kelvin viscosity is equal to 10% of that value. This is different from the regional rheology inferred by the postseismic investigations on the 2001 MW 7.8 Kokoxili and the 2008 MW 7.8 Wenchuan events, and the preferred thickness of the elastic crust is also different from that inferred from magnetotelluric profiles deployed in previous studies. We thus infer that the rheological structure within the Bayan Har block is possibly heterogeneous from west to east. Finally, the normal stress changes triggered by the coseismic rupture and postseismic process are estimated to be negative, but the shear stress changes to be positive on the western Kunlun fault, the eastern Dari fault and Bayan-Har Mountain fault. However, the current observations and studies are quite insufficient on those fault segments, therefore, we need to focus on their faulting behavior and seismic risk in the future.