Variation Of Shear Stress Research Articles

Thermoelastic damping in high frequency resonators using higher-order shear deformation theories

Thermoelastic damping (TED) in high frequency oscillators shifts their natural frequencies and attenuates the vibration amplitude. The amount of damping depends upon the temperature of the environment in which the device is operating. Here, we model the oscillator as a simply-supported beam of rectangular cross-section undergoing infinitesimal deformations. We consider three (the Levinson, the Timoshenko and a sinusoidal) through-the-thickness shear strain distributions, both translational and rotational inertia, and heat conduction to analytically delineate their effects on the shift in frequencies and the attenuation of their amplitudes for the lowest three vibration modes. The shear deformation distribution function multiplied by the Poisson ratio appears in the volumetric strain. The TED in the Timoshenko, the Levinson and a beam with sinusoidal variation of shear stresses is related to that in the Euler beam to recover the famous Lifshitz–Roukes formula. Various results are presented to qualitatively and quantitatively illustrate the dependence of the TED upon the lowest three frequencies and the resonator thickness. The analytical solutions presented here can be used as benchmark solutions for checking the numerical solutions.

Vessel-Specific Shear Stress Distribution and Heterogeneity in Angiogenic Rat Mesenteric Microvascular Networks

Fluid shear stress has been identified as an important player in regulating endothelial cell behaviors and angiogenesis, defined as the sprouting of new blood vessels from existing vessels. However, the correlative or functional linking of shear stress to vessel-specific endothelial cell dynamics requires a better understanding of the shear stress values at the capillary level in microvascular networks. Critical questions remain unanswered. What is the shear stress experienced by endothelial cells along capillaries? Do all capillaries experience similar shear stress magnitudes? Can variations in shear stress along different capillary segments explain vessel-specific responses? The objective of this project was to estimate shear stress values in regions of angiogenic microvascular networks. Rat mesenteric tissues were harvested from adult male Wistar rats post the stimulation of angiogenesis via 48-80 mast cell degranulation. Microvascular networks were identified by perfusion of a 40kDa fixable dextran prior to harvesting and immunolabelling for PECAM. Dextran presence identified perfused segments along the hierarchy of microvascular networks, which were characterized by increased vessel density indicative of angiogenesis. Representative network regions with arteriole input and venule output vessels were selected for analysis. Vessel segments were defined by adjacent nodes, and the measurements of lengths and diameter. Assuming an inlet pressure of 75 mmHg and outlet pressure of 10 mmHg, a network segmental Newtonian flow model was used to computationally estimate vessel-specific shear stresses and velocities. Viscosity was set to 4 cP and assumed to be constant. In the results, shear stresses along vascular segments in 3 medium microvascular regions ranged from 0.1 to 1114.3 dyne/cm2 (average = 81.3 ± 3.5 dyne/cm2), in 4 small regions ranged from 0.1 to 518.7 dyne/cm2 (average = 61 ± 3.4 dyne/cm2), and in 1 large region ranged from 0.003 to 2328.1 dyne/cm2 (average = 39.8 ± 1.6 dyne/cm2). For all regions, the highest shear stress values located at capillary segments, defined as vascular segments with diameters lower than 10 μm. As segment diameters increased, the matched maximum shear stresses decreased accordingly. Also, the high heterogeneity of shear stresses in capillaries indicates the possibility for segment-specific regulation. For 3 medium regions, shear stresses along proximal capillaries branching from arteriolar inlets to venular outlets were higher than stresses along capillaries in regions distal to inlets and outlets. The results highlight the variability of segment-specific shear stresses along capillaries in microvascular regions and motivate research looking into how endothelial cells respond to segment-specific microenvironment and regulation. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Oscillatory behaviors of multiple shock waves to upstream disturbances

The oscillatory response of multiple shock waves to upstream disturbances in a supersonic flow is studied numerically in a constant area rectangular duct. The flow is accelerated through a nozzle with an exit Mach number of 1.75 and continues in the constant area duct, where multiple shock waves are formed. To investigate the effect of upstream disturbance on shock oscillations, three parameters are varied systematically: upstream turbulent intensity, frequency of upstream pressure fluctuation, and amplitude of upstream pressure fluctuation. The wall shear stress variation along the duct length provides the location of separation and reattachment points in the flow field. The wall pressure frequency spectra were used to investigate the low-frequency unsteadiness in shock oscillations. The power spectral density of the wall static pressure and the probability density function (PDF) of shock location are analyzed, and the results suggest that as the upstream turbulent intensity is increased, the dominant frequency of oscillation is increased and the shock oscillations become more symmetrical. As the upstream disturbance frequency is increased, the shock oscillations become more symmetrical and follow the Gaussian curve closely. The shock wave oscillates with the same upstream excitation frequency when the upstream disturbance amplitude is increased. At large values of upstream disturbance amplitude, the PDF shows a large deviation from the Gaussian, and the rms amplitude of shock oscillation increases monotonously. At higher amplitudes of upstream disturbance excitation, the traces of shock train leading-edge location display path-dependence characteristics.

Numerical study of pulsatile thermal magnetohydrodynamic blood flow in an artery with aneurysm using lattice Boltzmann method (LBM)

Aneurysm is considered as one of the most common cardiovascular diseases with an important mortality rate. It is a serious pathology caused by a dilatation in the arterial wall. In this work, the influence of magnetic field on pulsatile blood flow and heat transfer in an artery with aneurysm is studied using the mesoscopic lattice Boltzmann method with BGK approximation (LBGK). Human blood is regarded as non-Newtonian and modeled by Carreau–Yasuda rheological model. The model findings are compared with recent data from the literature and demonstrate a good level of agreement, which confirms the effectiveness and accuracy of the suggested model. Results are depicted in terms of streamlines, temperature contours and wall shear stress (WSS) variation, for the certain pertinent non-dimensional Reynolds and Hartmann numbers. The findings demonstrate that the heat transfer is enhanced in the inlet zone of the aneurysm as the Hartmann number increases. Furthermore, it is found that the application of a magnetic field reduces the recirculation zones and increase the WSS, which prevent the progression of vascular diseases and rupture in the aneurysm region.

Variation of Shear Stresses and Flow Dynamics in Stented Patient Specific Carotid Bifurcation Model using Numerical Investigation

The carotid artery is a clinically important site in the human circulatory system as the consequences of its disease results in adverse outcomes like ischemic strokes, or death for too prolonged ischemia. Understanding the hemodynamics of this artery and its bifurcation are important. A method of treating the stenosis of this artery is Carotid Angioplasty and Stenting (CAS). This procedure results in a heavily modified hemodynamics or state of flow. To understand and predict this flow field modification Computational Fluid Dynamics (CFD) is an important computational tool. Further, the presence of a stent would affect hemodynamics. The aim of this work is to study these effects in patient-specific cases. The reconstructed patient-specific models will form the basis of the construction of the post-stenting carotid bifurcation models. A transient analysis was carried out to estimate the time-varying parameters in the fluid domains over a cardiac cycle as well as to gauge time average values over a cardiac cycle. Results are obtained for hemodynamic parameters, like wall shear stress, velocity, pressure, vorticity, and helicity, in both the prepared stenosed and stented geometries. It is seen that the stenting procedure leads to the renewal of the CCA to ICA flow path. But simultaneously the region in which the stent is present becomes a region of low TAWSS and contains areas of high OSI. These areas of low TAWSS and high OSI within the stented portions of the carotid bifurcations are indications for regions of possible restenosis. Therefore, the investigation demonstrates the likely region for future plaque growth. Further, the effects of widening of the lumen are also noted in comparison to the pre-stent cases

Influence of aortic aneurysm on the local distribution of NO and O2 using image-based computational fluid dynamics

There is a pressing need to establish novel biomarkers to predict the progression of thoracic aortic aneurysm (TAA) dilatation. Aside from hemodynamics, the roles of oxygen (O2) and nitric oxide (NO) in TAA pathogenesis are potentially significant. As such, it is imperative to comprehend the relationship between aneurysm presence and species distribution in both the lumen and aortic wall. Given the limitations of existing imaging methods, we propose the use of patient-specific computational fluid dynamics (CFD) to explore this relationship. We have performed CFD simulations of O2 and NO mass transfer in the lumen and aortic wall for two cases: a healthy control (HC) and a patient with TAA, both acquired using 4D-flow magnetic resonance imaging (MRI). The mass transfer of O2 was based on active transport by hemoglobin, while the local variations of the wall shear stress (WSS) drove NO production. Comparing hemodynamic properties, the time-averaged WSS was considerably lower for TAA, while the oscillatory shear index and endothelial cell activation potential were notably elevated. O2 and NO showed a non-uniform distribution within the lumen and an inverse correlation between the two species. We identified several locations of hypoxic regions for both cases due to lumen-side mass transfer limitations. In the wall, NO varied spatially, with a clear distinction between TAA and HC. In conclusion, the hemodynamics and mass transfer of NO in the aorta exhibit the potential to serve as a diagnostic biomarker for TAA. Furthermore, hypoxia may provide additional insights into the onset of other aortic pathologies.

Artificial intelligence velocimetry reveals in vivo flow rates, pressure gradients, and shear stresses in murine perivascular flows

Quantifying the flow of cerebrospinal fluid (CSF) is crucial for understanding brain waste clearance and nutrient delivery, as well as edema in pathological conditions such as stroke. However, existing in vivo techniques are limited to sparse velocity measurements in pial perivascular spaces (PVSs) or low-resolution measurements from brain-wide imaging. Additionally, volume flow rate, pressure, and shear stress variation in PVSs are essentially impossible to measure in vivo. Here, we show that artificial intelligence velocimetry (AIV) can integrate sparse velocity measurements with physics-informed neural networks to quantify CSF flow in PVSs. With AIV, we infer three-dimensional (3D), high-resolution velocity, pressure, and shear stress. Validation comes from training with 70% of PTV measurements and demonstrating close agreement with the remaining 30%. A sensitivity analysis on the AIV inputs shows that the uncertainty in AIV inferred quantities due to uncertainties in the PVS boundary locations inherent to in vivo imaging is less than 30%, and the uncertainty from the neural net initialization is less than 1%. In PVSs of N = 4 wild-type mice we find mean flow speed 16.33 ± 11.09 µm/s, volume flow rate 2.22 ± 1.983 × 103 µm3/s, axial pressure gradient ( - 2.75 ± 2.01)×10-4 Pa/µm (-2.07 ± 1.51 mmHg/m), and wall shear stress (3.00 ± 1.45)×10-3 Pa (all mean ± SE). Pressure gradients, flow rates, and resistances agree with prior predictions. AIV infers in vivo PVS flows in remarkable detail, which will improve fluid dynamic models and potentially clarify how CSF flow changes with aging, Alzheimer's disease, and small vessel disease.

Speed shear rate impact on the properties of OSA-modified potato starch

The reaction between starch granules and octenyl succinic anhydride (OSA) is regularly retarded due to the low breakthrough of large oily OSA droplets into starch granules in an aqueous reaction system. Furthermore, high-speed shearing is widely used in the food industry, demanding high shear, cavitation, and collision force. In this sense, high-speed shearing could reduce the size of OSA droplets and promote a more homogeneous distribution of groups in the starch granule. The aim of this study was to evaluate the impact of OSA potato starch synthesis assisted by high-speed shear on structure (SEM and FTIR), gelatinization, rheology, and emulsifying activity (ES and AS) was investigated. The results showed a gradual increase in DS proportional to the applied speed. Likewise, the OSA starches showed a slight alteration in the shape of the granules (SEM), and FT-IR spectroscopy showed a characteristic absorption of the ester carbonyl groups in the OSA starch at 1724 cm-1. The high-speed shear-treated starches exhibited a significant change in the reduction of the initial gelatinization temperature, although not in the enthalpy. All the gels presented rheology adjusted to the Herschel-Bulkley model with variations in the initial shear stress. Changes in the viscoelastic behavior are proportional to the shear rate detected. High-speed shear treatment did not show a significant effect on emulsion stability (ES) and emulsion activity (EA). Consequently, applying high shear rates allows having OSA starches with different uses.

Stability Analysis of Tunnel Surrounding Rock When TBM Passes through Fracture Zones with Different Deterioration Levels and Dip Angles

In fracture zones, tunneling with a double-shield Tunnel Boring Machine (TBM) presents significant challenges, including deformation overrun of the surrounding rock, TBM jamming, and excavation face collapse. To assure the tunnel construction safety and efficiency, it is necessary and crucial to conduct a stability analysis of the tunnel surrounding rock when a TBM passes through the fracture zones. The tunnels from Jiadingshan Road Station to Anshan Road Station in Qingdao Metro Line 8 are constructed by double-shield TBMs. It inevitably passes through fracture zones with different deterioration levels and dip angles. In this study, based on this construction section, numerical models of fracture zones with different deterioration levels and dip angles were developed to analyze the displacements of tunnel vaults, inverts, and haunches. In addition, the maximum shear stresses of the surrounding rock were analyzed. Finally, the displacement and shear stress variation patterns of the surrounding rock with different deterioration levels and dip angles were obtained. The findings reveal the stability behavior of tunnels under various fracture zones. They can serve as a valuable reference and theoretical foundation for future tunnel construction projects utilizing double-shield TBMs in areas with fracture zones.

A New Focal Mechanism Calculation Algorithm (REFOC) Using Inter‐Event Relative Radiation Patterns: Application to the Earthquakes in the Parkfield Area

AbstractAccurate earthquake focal mechanisms are essential for solving fault zone structure, estimating stress variations, and assessing seismic hazards. Small earthquakes' focal mechanisms are usually solved using P‐wave first‐motion polarities and/or S‐/P‐wave amplitude ratios, which are limited due to the low signal‐to‐noise ratio of small‐earthquake waveforms and a limited number of three‐component seismograms. To increase the number of high‐quality focal mechanisms, we develop a method that utilizes the inter‐event relative radiation patterns to perform a joint focal mechanism inversion of numerous clustered events (called REFOC). The method first uses P‐wave polarities and S‐/P‐wave amplitude ratios to constrain the initial solutions and then combines these solutions and the inter‐event P‐/P‐wave and S‐/S‐wave amplitude ratios to refine solutions. For example, we apply the method to 38,413 earthquakes in the Parkfield region, California. The REFOC outperforms traditional methods with 57% more solutions with <55° uncertainties (>70% of the catalog events) and 126% more solutions with <25° uncertainties (>40% of the catalog events), illuminating unprecedented fine‐scale rupture processes. Instead of rupturing along the main fault, many M < 2 focal mechanisms show >45° angular differences from the 2004 Mw 6.0 Parkfield earthquake. The variation of focal mechanism properties is spatially related to the variation of fault strength and geometry, and temporally correlated with the shear stress variations before, during, and after the 2004 Mw 6.0 earthquake. The observations highlight the potential of applying REFOC to monitor unprecedented details of fault zone structure and stress field, providing new insights into fault rupture physics, seismotectonic processes, and seismic hazards.

Effects of freeze–thaw cycles on the shear stress induced on the cemented sand–structure interface

Freeze–thaw alternation and freeze–thaw cycle erosion are the main reasons for the failure of the cemented soil–structure interface in cold regions. In this study, the direct shear and cyclic direct shear tests of cemented sand–structure interface were conducted in the frozen state (−10 °C) and thawed state (25 °C) at a 300 kPa normal stress under different freeze–thaw cycles (i.e., 0, 1, 5, 10, 15, 20, 25, 30). The experimental results for the shear stresses of the cemented sand–structure interface are presented, and the mechanism of shear stress formation and change was examined through mesoscopic analysis. Variations in shear stress with different freeze–thaw cycles were consistent. Typically, 10 was identified as the critical freeze–thaw cycle number for adfreeze strength, and the hyperbolic model of shear stress–displacement curve in the thawed state was obtained. The peak shear stresses of different freeze–thaw cycles gradually decreased as the shearing cycle number increased until entering a stable stage in frozen state and were close to each other in the thawed state. The internal damage of cemented sand and the formation of ice crystals on the surface increased with the increase in freeze–thaw cycle number. Hence, internal change in cemented sand under freeze–thaw cycles is the fundamental reason for alterations in shear stress. The results of this study shed light on shear stress complexity at the cemented sand–structure interface under freeze–thaw cycles and provide references for practical engineering.

Multi-scale Modelling of Shear Stress on the Syncytiotrophoblast: Could Maternal Blood Flow Impact Placental Function Across Gestation?

The placenta is a critical fetal exchange organ, with a complex branching tree-like structure. Its surface is covered by a single multinucleated cell, the syncytiotrophoblast, which bathes in maternal blood for most of pregnancy. Mechanosensing protein expression by the syncytiotrophoblast at term suggests that shear stress exerted by maternal blood flow may modulate placental development and function. However, it is not known how the mechanosensitive capacity of the syncytiotrophoblast, or the shear stress it experiences, change across gestation. Here, we show that the syncytiotrophoblast expresses both mechanosensitive ion channels (Piezo 1, Polycystin 2, TRPV6) and motor proteins associated with primary cilia (Dynein 1, IFT88, Kinesin 2), with higher staining for all these proteins seen in late first trimester placentae than at term. MicroCT imaging of placental tissue was then used to inform computational models of blood flow at the placentone scale (using a porous media model), and at the villous scale (using explicit flow simulations). These two models are then linked to produce a combined model that allows the variation of shear stress across both these scales simultaneously. This combined model predicts that the range of shear stress on the syncytiotrophoblast is higher in the first-trimester than at term (0.8 dyne/cm2 median stress compared to 0.04 dyne/cm2) when considering both these scales. Together, this suggests that the nature of blood flow through the intervillous space, and the resulting shear stress on the syncytiotrophoblast have important influences on placental morphogenesis and function from early in pregnancy.

On accurately capturing the through-thickness variation of transverse shear and normal stresses for composite beams using FSDT coupled with GPR

On accurately capturing the through-thickness variation of transverse shear and normal stresses for composite beams using FSDT coupled with GPR

Effect of roughness on the shear behavior of rock joints subjected to impact loading

The shear behavior is regarded as the dominant property of rock joints and is dramatically affected by the joint surface roughness. To date, the effect of surface roughness on the shear behavior of rock joints under static or cyclic loading conditions has been extensively studied, but such effect under impact loading conditions keeps unclear. To address this issue, a series of impact shear tests was performed using a novel-designed dynamic experimental system combined with the digital image correlation (DIC) technique. The dynamic shear strength, deformability and failure mode of the jointed specimens with various joint roughness coefficients (JRC) are comprehensively analyzed. Results show that the shear strength and shear displacement characteristics of the rock joint under the impact loading keep consistent with those under static loading conditions. However, the temporal variations of shear stress, slip displacement and normal displacement under the impact loading conditions show obviously different behaviors. An elastic rebound of the slip displacement occurs during the impact shearing and its value increases with increasing joint roughness. Two identifiable stages (i.e. compression and dilation) are observed in the normal displacement curves for the rougher rock joints, whereas the joints with small roughness only manifest normal compression displacement. Besides, as the roughness increases, the maximum compression tends to decrease, while the maximum dilation gradually increases. Moreover, the microstructural analysis based on scanning electron microscope (SEM) suggests that the roughness significantly affects the characteristics of the shear fractured zone enclosing the joint surface.

Characteristics of self-excited shock wave oscillations in a supersonic isolator with exit duct configurations

The structure and dynamics of multiple shock waves inside a constant area isolator of a model scramjet engine are studied numerically using a finite volume solver. The flow is accelerated through a nozzle with an exit Mach number of 1.75 and continues in the constant area isolator where multiple shock waves are formed. To analyze the effect of duct acoustics on the dynamics of shock train oscillations, three ducts with a duct length of 0D, 50D, and 150D are attached to the exit of the isolator, where D is the isolator exit height. The wall static pressure variation along the bottom wall and four specific locations are monitored. The wall shear stress variation along the wall provides the location of separation and reattachment points in the flow field. The statistical analysis provided more insights into the oscillation mechanisms. The lower frequency components from the duct resonance are enhanced as the duct length is increased and it altered the dominant frequency of shock oscillation. The dependence of shock train length on the exit duct confirmation is analyzed by the pressure ratio method. The different frequency components in the flow field are analyzed using the power spectral density of wall static pressure fluctuations and are distinguished based on the frequency range. The cross-spectral analysis of the wall pressure fluctuations provided the correlation between pressure signals and their narrowband time delay. Thus, the origin and directions of the perturbations are obtained and discussed. The increase in exit duct length decreases the downstream disturbance velocity, indicating the duct resonance effect on shock train oscillations. • Simulation of the supersonic isolator flow field to understand the duct resonance effect on self-excited oscillations of shock train. • The duct resonance is varied by attaching ducts of different lengths to the exit of the isolator. • As the duct length is increased, the amplitude of shock oscillation is increased and the dominant frequency of shock oscillation is decreased. • The length of the shock train is increased with an increase in duct length. • The cross-spectral analysis of the wall pressure fluctuations provided the correlation between pressure signals and their narrowband time delay.

Novel test method to determine shear properties of lattices: Test set-up and data analysis

In order to determine shear response for lattices, relevant standards for other similar materials were studied. A V-notched beam shear test set-up was developed, including design of a fixture and a V-notched lattice specimen as well as determining test procedure and data analysis method. Followings are some of the considerations and features. Sufficient number of cells are required to obtain representative properties for a given lattice. The free-end condition for installation and gripping of the specimen on fixture arms guarantees loading in pure shear. The overall geometry and presence of a V-notch smooth the shear stress variation across the notch section. It was demonstrated that using Digital Image Correlation (DIC) method improves the accuracy of measured shear strain by removing the deformation of cells adjacent to the notch, as well as the deflection of fixture components. Following the proposed method, shear properties including shear chord modulus of elasticity, offset shear strength, and shear ultimate strength/strain can be determined. These data can be used for material specification, quality assurance, research and development, and structural design and analysis of lattices.

Hygrothermal dynamic behavior of fiber metal laminated structure under dual-ellipse distribution heat source

Refined plate theory could account for parabolic variation of transverse shear stress through the thickness, and satisfy the zero traction boundary conditions on the top and bottom surfaces of the plate without introducing shear correction factor, of which all displacement variables can be depicted in functions of shear and bending components. Based on three-dimensional transient thermal conduction theory and the refined plate theory, an analytical solution of fiber metal laminated (FML) plate under hygrothermal environment is presented. In present work, distinct from other literatures, the separate variable method and Newton-Cotes method is applied to solve the three-dimensional transient temperature field (subjected to moving dual-ellipse distribution laser heat source) firstly. Secondly, the constitutive equations and geometrical equations are derived. Subsequently, the governing equations in hygrothermal environment are obtained. Finally, the Newmark method and Galerkin method are used to solve the governing equations of which in terms of displacement functions. The results show that fiber orientation affects the bending stiffness, the selection of (45°/ 0°) fiber orientation is more resistance to deformation and normal stress, and bending part is more sensitive to shear factor between layers.

CFD simulation of the hydrodynamics within an RVF module in laminar regime

The dynamic filtration module called Rotating and Vibrating Filtration (RVF) is a performant device for membrane fouling control and limiting the formation of cake layer. Indeed, it can generate strong shear stress at the membrane surface decoupled from the feeding flowrate. Moreover, the pressure fluctuation that takes place in the device is also beneficial to control membrane fouling. A CFD model has been validated in laminar regime from experimental measurements of velocity fields and pressure distribution inside the RVF. The boundary layer development at the walls were carefully studied to better explain the effects of the rotation speed and the viscosity on the spatial distribution and time variations of pressure and shear stress at the membrane surface. It appears that shear stress is more efficient than pressure to control membrane performances in laminar regime.

Observation of mixed grain size sediment transport rate and streamwise nearbed flow velocity in a gravel-worked bed

This experiment observed the prediction of sediment movement for channel bed composed of mixed grain size and its relationship with nearbed turbulence. Changes in transport rate at different time elapsed was obtained by observing bedload transport rate and associated them with streamwise nearbed flow velocity. Regardless of the shape and duration, observations indicate that the total amounts of transported bedload during the antecedent flow hydrographs are the best indicators of bed stability as observed in the stability hydrographs. Experiments also suggest that high turbulence flow caused by dispersion in the average streamwise nearbed velocity roughly disrupted the bed, allowing dislodgement of coarser grain and preventing finer materials from being fully sheltered. As the result the production of transported material was very significantly increased. Systematic change is presumably absent in the variation of average instantaneous shear stress following an increasing and decreasing discharge as evidenced by average streamwise nearbed flow velocity during different pattern of antecedent flow hydrographs. The variations that produced slightly different fashion in transport rate led to the inference that the major difference in the transport rate response during stability tests were created by unsteady flow hydrographs with rapid increase and rapid decrease.

Effects of Porous Size and Membrane Pattern on Shear Stress Characteristic in Gut-on-a-Chip with Peristalsis Motion.

Dynamic gut-on-a-chip platform allows better recreation of the intestinal environment in vitro compared to the traditional static cell culture. However, the underlying mechanism is still not fully discovered. In this study, the shear stress behavior in a gut-on-a-chip device with porous membrane subjected to peristalsis motion is numerically investigated using CFD simulation for three different pore sizes and two pattern layouts. The results reveal that, in the stationary microchannel, the average shear stress on the porous membrane is approximately 15% greater than that of the flat membrane, regardless of the pore size. However, when subjected to cyclic deformation, the porous membrane with smaller pore size experiences stronger variation of shear stress which is ±5.61%, ±10.12% and ±34.45% from its average for the pore diameters of 10 μm, 5 μm and 1 μm, respectively. The shear stress distribution is more consistent in case of the staggered pattern layout while the in-line pattern layout allows for a 32% wider range of shear stress at the identical pore size during a cyclic deformation. These changes in the shear stress caused by peristalsis motion, porous size and membrane pattern could be the key factors that promote cell differentiation in the deforming gut-on-a-chip model.