Effect Of Fluid Viscosity Research Articles

The influence of static portal pressure on liver biophysical properties.

The liver is a highly vascularized organ where fluid properties, including vascular pressure, vessel integrity and fluid viscosity, play a critical role in gross mechanical properties. To study the effects of portal pressure, liver confinement, fluid viscosity, and tissue crosslinking on liver stiffness, water diffusion, and vessel size, we applied multiparametric magnetic resonance imaging (mpMRI), including multifrequency magnetic resonance elastography (MRE) and apparent diffusion coefficient (ADC) measurements, to ex vivo livers from healthy male rats (13.6±1.6 weeks) at room temperature. Four scenarios including altered liver confinement, tissue crosslinking, and vascular fluid viscosity were investigated with mpMRI at different portal pressure levels (0-17.5 cmH2O). Our experiments demonstrated that, with increasing portal pressure, rat livers showed higher water content, water diffusivity, and increased vessel sizes quantified by the vessel tissue volume fraction (VTVF). These effects were most pronounced in native, unconfined livers (VTVF: 300±120%, p<0.05, ADC: 88±29%, p<0.01), while still significant under confinement (confined: VTVF: 53±32%, p<0.01, ADC: 28±19%, p<0.05; confined-fixed: VTVF: 52±20%, p<0.001, ADC: 11±2%, p<0.01; confined-viscous: VTVF: 210±110%, p<0.01, ADC: 26±9%, p<0.001). Softening with elevated portal pressure (-12±5, p<0.05) occurred regardless of confinement and fixation. However, the liver stiffened when exposed to a more viscous inflow fluid (11±4%, p<0.001). Taken together, our results elucidate the complex relationship between macroscopic-biophysical parameters of liver tissue measured by mpMRI and vascular-fluid properties. Influenced by portal pressure, vascular permeability, and matrix crosslinking, liver stiffness is sensitive to intrinsic poroelastic properties, which, alongside vascular architecture and water diffusivity, may aid in the differential diagnosis of liver disease. STATEMENT OF SIGNIFICANCE: Using highly controllable ex vivo rat liver phantoms, hepatic biophysical properties such as tissue-vascular structure, stiffness, and water diffusivity were investigated using multiparametric MRI including multifrequency magnetic resonance elastography (MRE) and diffusion-weighted imaging (DWI). Through elaborate tuning of the experimental conditions such as the static portal pressure, flow viscosity, amount and distribution of fluid content in the liver, we identified the contributions of the fluid component to the overall imaging-based biophysical properties of the liver. Our finding demonstrated the sensitivity of liver stiffness to the hepatic poroelastic properties, which may aid in the differential diagnosis of liver diseases.

Effect of fluid viscosity on the biomechanical sequence of oropharyngeal swallowing in healthy males

Objective: To confirm the effect of fluid with different viscosity on the normal biomechanical sequence of oropharyngeal swallowing in healthy males. Methods: Fifteen healthy male subjects [(27.7±1.8) years old] were recruited from November 2011 to February 2012 and instructed to swallow 15 ml of water (W), nectar-like fluid (N), and honey-like fluid (H) in an upright sitting position. The sensing system was consisted of tongue pressure sensor sheet, bend sensor, surface electrodes and microphone. They were used to monitor tongue pressure, hyoid activity, surface electromyography (EMG) of swallowing-related muscles and swallowing sound, respectively. The swallowing sound was chosen as the reference time. The significance of biomechanical sequence of structural events was determined by repeated-measures analysis of variance (ANOVA). Results: When swallowing liquid of any consistency, hyoid premotor and suprahyoid muscle electromyography (EMG) appeared synchronously (P>0.05), followed by the simultaneous appearances of hyoid rapid movement, peak time of suprahyoid muscle EMG, onset of infrahyoid muscle EMG, and anterior tongue pressure production (P>0.05). The peak time of infrahyoid muscle EMG was very close to the peak time of anterior tongue pressure (P>0.05), and both of them were earlier than the time that the hyoid reaching the highest position (P<0.05). At last, the time that the hyoid departing the highest position was synchronized with the disappearances of suprahyoid muscle EMG, infrahyoid muscle EMG, and tongue pressure (P>0.05). The tongue pressure production and peak time of tongue pressure arose from anterior to posterior along the midline of hard palate during normal swallowing, with the significances for tongue pressure production between the anterior site and the middle site (W: P=0.035, N: P=0.027, H: P=0.013) as well as the anterior site and the posterior site (W: P<0.001, N: P<0.001, H: P<0.001), while the appearance and peak time of the circumferential tongue pressure were very close (P>0.05). The increase of fluid viscosity did not affect the biomechanical sequence of the above structural physiological movements during normal swallowing. There were statistically significant differences between the hyoid premotor and the onset of suprahyoid muscle EMG when swallowing the honey-like liquid [(-1.03±0.47) and (-0.90±0.50) s] and water[(-0.87±0.32) and (-0.74±0.31) s] (P<0.001). Among the delayed structural events, except for the onset of infrahyoid muscle EMG and the tongue pressure production on the anterior site (P>0.05), the occurrences of all the parameters in swallowing honey-like fluid were significantly later than those in swallowing water (onset of hyoid rapid movement, P=0.007; time of hyoid reaching the highest position, P=0.034; time of hyoid departing the highest position, P=0.041; offset of hyoid movement, P=0.035; peak time of suprahyoid muscle EMG: P=0.040; offset of suprahyoid muscle EMG, P=0.014; peak time of infrahyoid muscle EMG: P=0.042; offset of infrahyoid muscle EMG, P=0.028; peak time of Ch.1: P=0.045; offset of Ch.1: P=0.012; onset of Ch.2: P=0.038; peak time of Ch.2: P=0.009; offset of Ch.2: P=0.034; onset of Ch.3: P=0.043; peak time of Ch.3: P=0.011; offset of Ch.3: P=0.026;onset of Ch.4: P=0.040; peak time of Ch.4: P=0.038; offset of Ch.4: P=0.033; onset of Ch.5: P=0.046; peak time of Ch.5:P=0.028; offset of Ch.5: P<0.001), but not for those between nectar-like fluid and honey-like fluid (P>0.05). Conclusions: The alteration of fluid viscosity did not affect healthy male biomechanical sequence of tongue, hyoid and swallowing-related muscles during normal swallowing. The biomechanics of the oropharyngeal structures is physiologically regulated with the alteration of fluid viscosity to ensure swallowing safely and smoothly.

Enhancement effects of extracellular fluid viscosity and matrix stiffness on cancer cell mechanosensing

Cancer cells are in vivo situated in a complex and heterogeneous tumor microenvironment (TME) that includes various biochemical and biophysical cues, such as the elasticity of extracellular matrix (ECMwo) and the viscosity of extracellular fluid (ECF). ECF viscosity in TME is much higher than in normal tissue, but it is unclear how this increased viscosity works simultaneously with other biophysical cues (e.g., ECM stiffness) to influence cancer cell behavior. We experimentally observed that ECF viscosity can significantly enhance cellular mechanosensing behaviors (e.g., cell spreading, cell adhesion, and YAP/TAZ nuclear translocation) only on a stiff substrate, representing a novel enhancement of cell behaviors by distinct mechanical signals. To explore the mechanical mechanisms behind such enhancement phenomenon, we developed a viscosity-based motor-clutch model, with which we found that cells sense and respond to ECF viscosity and ECM stiffness by regulating integrin-ECM bonds in cell adhesion dynamics. These findings help us understand how different mechanical signals in the complex tumor microenvironment collaborate to influence cancer cell behaviors during the development of cancers.

A Numerical Study on Labyrinth Screw Pump (LSP) Performance under Viscous Fluid Flow

In this study, fluid viscosity effects on LSP performance in terms of boosting pressure were numerically investigated. A water–glycerin mixture with different concentrations corresponding to varying apparent viscosities was flowed through an in-house manufactured LSP under various flow conditions, e.g., changing flow rates, rotational speeds, and fluid viscosities. The pressure increment between the intake and discharge of the LSP was recorded using the differential pressure transducer. The same pump geometries, fluid properties and flow conditions were incorporated into the numerical configurations, where three-dimensional (3D), steady-state, Reynolds-averaged Navier–Stokes (RANS) equations with a standard SST (shear stress transport) turbulence model were solved by a commercial CFD code. With the high-quality poly-hexcore grids, the simulated pressure increment was compared with the corresponding experimental measurement. The internal flow structures and characteristics within the cavities contained by the LSP impeller and diffuser were also analyzed. The good agreement between the numerical results against the experimental data verified the methodology adopted in this study.

Acoustic radiation force on a spherical thermoviscous particle in a thermoviscous fluid including scattering and microstreaming.

We derive general analytical expressions for the time-averaged acoustic radiation force on a small spherical particle suspended in a fluid and located in an axisymmetric incident acoustic wave. We treat the cases of the particle being either an elastic solid or a fluid particle. The effects of particle vibrations, acoustic scattering, acoustic microstreaming, heat conduction, and temperature-dependent fluid viscosity are all included in the theory. Acoustic streaming inside the particle is also taken into account for the case of a fluid particle. No restrictions are placed on the widths of the viscous and thermal boundary layers relative to the particle radius. We compare the resulting acoustic radiation force with that obtained from previous theories in the literature, and we identify limits, where the theories agree, and specific cases of particle and fluid materials, where qualitative or significant quantitative deviations between the theories arise.

Impacts of variable viscosity and chemical reaction on Ohmic dissipative fluid flow in a porous medium over a stretching sheet with thermal radiation

AbstractThis study investigates the chemical reaction influence on heat transfer flow of viscous Newtonian fluid over a moving surface under the intensity of nonuniform heat source/sink. Variable fluid viscosity and ohmic heating effects are considered in the model equation. The uniqueness of the present investigation is to scrutinize the significance of nonuniform heat source/sink and ohmic heating on the heat transfer flow of optically thin radiative fluid in a permeable medium. The flow equations of continuity, momentum, thermal and solutal fields are converted by invoking relevant dimensionless variables. Also, the converted nonlinear equations are analyzed numerically by using the fourth order Runge–Kutta Fehlberg approach. The significance of model parameters are scrutinized and discussed in detail via graphs and tables. The important findings of this study are the effects of Joule heating , viscous dissipation parameter , variable fluid property parameter and radiation parameter on fluid flow, energy profile and solutal field. The results show that the thermal field depreciates as the Prandtl number increases but escalates against higher values of Joule heating parameter and Brinkman number. Also, the outcome of this study reveals that an enhancement in the values of variable viscosity parameter declines velocity distribution. Concentration distributions behave as a growing function of the Soret number and diminishing function of the Schmidt number. Furthermore, contrasting this study with existing results reveals excellent agreement.

A simplified approach to hydraulic fracturing of rocks based on Finite Fracture Mechanics

AbstractThis work presents a coupled approach, based on Finite Fracture Mechanics (FFM), to preliminarily investigate hydraulic fracturing of rocks. The novelty of the criterion relies on the assumption of a finite crack extension and on the simultaneous fulfillment of a stress requirement and the energy balance. Two material constants are involved, namely, the tensile strength and the fracture toughness. The FFM unknowns are represented by the critical crack advance, which results a structural parameter and not a simple material one, and the breakdown pressure. The study investigates the longitudinal failure behavior of both impermeable and permeable rocks by supposing that growing cracks are loaded by a pressure proportional to that acting on the borehole wall. The stability growth of hydraulic fractures is discussed case by case. The approach is validated against experimental data available in the literature by considering the effect of rock permeability, fluid viscosity and flow rate.

Numerical study of electrohydrodynamic atomization considering liquid wetting and corona discharge effects

In this paper, the behavior of the cone-jet mode of fluid by electrohydrodynamic atomization (electrospray) is numerically simulated and investigated with the effect of liquid wetting and corona discharge effects. The simulation was performed with contact angle condition to fit the Taylor cone shape by experiments. Experimental data are provided to verify and validate the numerical method, followed by additional analyses on the effects of electrical conductivity, surface tension, flow rate, and fluid viscosity on the electrospray characteristics, including spray current and jet diameter. Numerical results by simulations are in reasonable agreement with experiments and consistent with the literature. Analyses on different contact angles suggest potentially major impacts of this factor on the cone-jet mode in high voltage and low flow rate circumstances. Furthermore, the influence of corona discharge on electrospray is also investigated by both electrospray–corona simulation and experiment using a high-speed camera, yielding a significant improvement in the numerical prediction for Taylor cone formation. Numerical results indicate that liquid wetting on capillary nozzles would be a vital factor for the Taylor cone formation in numerical electrospray–corona discharge studies.

Computational Fluid Dynamics Modeling of Top-Down Digital Light Processing Additive Manufacturing.

Digital light processing (DLP) as a vat photopolymerization technique is one of the most popular three-dimensional (3D) printing methods, where chains are formed between liquid photocurable resin molecules to crosslink them and solidify the liquid resin using ultraviolet light. The DLP technique is inherently complex and the part accuracy depends on the process parameters that have to be chosen based on the fluid (resin) properties. In the present work, computational fluid dynamics (CFD) simulations are presented for top-down DLP as photocuring 3D printing. The effects of fluid viscosity, travelling speed of build part, travelling speed ratio (ratio of the up-to-down traveling speeds of build part), printed layer thickness, and travel distance considering 13 various cases are scrutinized by the developed model to obtain a stability time of fluid interface. The stability time describes the time it takes for the fluid interface to show minimum fluctuations. According to the simulations, a higher viscosity leads to prints with higher stability time. However, lower stability times in the printed layers are caused by a higher traveling speed ratio (TSR). The variation in settling times with TSR is extremely small in comparison to that of viscosity and travelling speed variations. As a result, a declining trend can be detected for the stability time by increasing the printed layer thickness, while by enhancing the travel distance values, the stability time demonstrated a descending pattern. In total, it was revealed that it is essential to choose optimal process parameters for achieving practical results. Moreover, the numerical model can assist in the optimizing the process parameters.

Inclusion of anisotropy in understanding rock deformation and inter-well fracture growth in layered formation through CZM based XFEM

In layered formations such as the Wufeng-Longmaxi marine shale, mechanical rock properties may be uniform horizontally within a layer, but vary vertically, and from layer to layer. In this study, we implement Newton-Raphson method within a rigorous two-dimensional scheme for computing fluid-solid coupling at every time increment in an anisotropic rock frame. The investigated domain consists of intercalations of soft and hard rock layers with a consideration of a cluster of three horizontal wells. The linear convection equation describing the fluid flow is discretized using upwind scheme whose integration points are determined by the intersection between the crack geometry and the underlying discretization of the extended finite element method (XFEM). A normalized slurry concentration averaged over the fracture width is used to establish a basis for analysing fluid viscosity effects with subsequent XFEM computation indicating that an increased slurry concentration leads to increasing fracture aperture. We further conduct a thorough investigation of an inter-well fracture development with the analyses revealing that the fractures kink at the interfaces of the intercalations of soft and hard layers. It is also observed that, when the elastic contrast between the soft and hard strata decreases, fracture kinking reduces and the inter-well fracture interference mechanism switches to linking or coalescence. Before the linking, the fluid pressure fields inside the separate fractures are independent, whereas an equilibrated pressure field develops inside the inter-linked fracture system. Oriented initial perforations show no link-growth of fractures. However, we observe that the highest inclination angle, which is 75° in our case, yields the highest treatment pressure of 62.8 MPa, whereas the lowest inclination angle of 15° yields the lowest treatment pressure of 56.3 MPa. We validate our results through comparison with a triaxial fracturing cell experiment, and Kristianovich-Geertsma-de Klerk (KGD) fracture problem. In all cases, the findings agree with the numerical results.

Effects of fluid saturation and viscosity on seismic dispersion characteristics in Berea sandstone

Effects of fluid saturation and viscosity on seismic dispersion characteristics in Berea sandstone

Study on the effect of viscosity and fluid flow on buckling behavior of nanoplate with surface energy

In this article, the buckling of a nanoplate at the bottom of a tank over which the fluid passes with a one-dimensional flow was investigated. Navier-Stokes equations were used to obtain the applied force from the fluid to the nanoplate. Surface effects theory was used to consider nanoscale effects. By solving this problem using Galerkin's weighted residual method, the effect of fluid viscosity and flow velocity was studied, and also the way surface effects change the critical buckling load of the nanoplates placed in the fluid was investigated. The results reported in this research are very helpful for developing and improving the performance of fluid-coupled nanostructures that have buckling potential.

Performance Comparison of Different Flat Plate Solar Collectors by Means of the Entropy Generation Rate Using Computational Fluid Dynamics

In this work, a numerical analysis of three different flat plate solar collectors was conducted using their entropy generation rates. Specifically, the Computational Fluid Dynamics (CFD) technique was used to compare the detailed performance of conventional and zigzag tube geometries of flat plate solar collectors (FPCs) in terms of their entropy generation rates. The effects of fluid viscosity, heat transfer, and heat loss of the flat plate solar collectors were considered for the local and global entropy generation rate analyses. Variations on the inlet volumetric flow rate of the FPCs from 1.0 to 9.0 L/min were simulated under the average solar radiation for one year in the state of Guanajuato, Mexico. The results illustrate and discuss the temperatures, pressures, and global entropy generation rates for volumetric flow variations. The velocity, temperature, and pressure distributions and the maps of the local entropy generation rates inside the collectors are presented and analyzed for the case with a flow rate of 3.0 L/min. These results demonstrate that the zigzag geometries achieved higher outlet temperatures and greater entropy generation rates than the conventional geometry for all the volumetric flow rates considered.

Investigation of a centrifugal pump for energy loss due to clearance thickness while pumping different viscosity oils

The clearance between the stationary volute and rotating impeller of a centrifugal pump is crucial; however, it affects the internal flow and deteriorates the pump performance. This study performed a flow investigation through a numerical simulation to understand the effect of clearance and pumping fluid viscosity under the design and off-design conditions of a centrifugal pump. Numerical simulations were conducted by solving unsteady Reynolds-averaged Navier-Stokes (URANS) equations and validated using experimental results. Five three-dimensional centrifugal pump flow domains were created, by varying the clearance thickness, and simulated with three different fluid properties. Consequently, the numerical simulation results aided in understanding the internal flow pattern and estimating energy loss due to disk friction and leakage through the clearance. It was found that the disk friction and leakage losses, which cause secondary losses in the pump, were highly affected by the fluid properties and clearance thickness. The clearance thickness drastically affected both the volumetric and hydraulic efficiencies to leakage; however, beyond a particular value, it became less significant. Furthermore, the viscous oils caused a high disk friction loss; however, the leakage loss was less affected by the clearance thickness.

Effect of Fluid Viscosity on Generalized Lamb Waves in a System Consisting of an Elastic Layer and a Viscous Fluid Layer

Effect of Fluid Viscosity on Generalized Lamb Waves in a System Consisting of an Elastic Layer and a Viscous Fluid Layer

Hemolysis prediction in bio-microfluidic applications using resolved CFD-DEM simulations

Background and ObjectiveHemolysis, namely hemoglobin leakage from red blood cells (RBCs), is one of the major sources of incorrect results in clinical tests, especially when passive microfluidics is involved. This is due to small characteristic dimensions which could cause strong RBCs deformation. Prediction of hemolysis is essential in the design and optimization of lab-on-a-chip devices for cell sorting and plasma separation. The aim of this work is to provide a numerical simulation tool this purpose applicable to real-scale bio-microfluidic devices with affordable computational cost. MethodsBlood is modelled as a suspension of biological cells, mainly RBCs, in liquid plasma assumed as a Newtonian, incompressible carrier fluid. Therefore, the physics of cells and carrier fluid is coupled by means of an immersed boundary concept known as resolved CFD-DEM. In this approach, the Navier-Stokes equations are numerically solved through a finite volume method with an additional penalty term to account for the presence of RBCs. RBCs’ positions and velocities are updated by solving Newton and Euler equations for conservation of linear and angular momentum. To model the RBCs deformation, a reduced-order model is employed, where each RBC is represented by a clump of overlapping rigid spheres connected by fictional numerical bonds, whose properties are tuned to reproduce the ones of RBCs viscoelastic membrane. This coupled approach allows access to cell-level information and facilitates the usage of strain-based hemolysis models. ResultsDifferent micro-channel geometries and blood hematocrits are simulated, to explore the influence of these factors on RBCs damage. Statistical analysis is performed to extract relevant biophysical quantities from numerical simulations such as hemolysis index distribution at the channel exit. Finally, the effect of carrier fluid viscosity is studied in relation to cell-cell interactions. ConclusionsSimulation results show that hemolysis occurrence is almost independent of the hematocrit values in the microchannel, implying the possibility to speed up calculation using low hematocrit values. Nevertheless, using whole blood viscosity for the carrier fluid overestimates the value of the hemolysis index by almost one order of magnitude.

考虑压裂液渗吸的压后压裂液返排的数值模拟

Fracturing fluid flowback is a key step in the process of hydraulic fracturing, and the imbibition of fracturing fluid in unconventional tight reservoirs cannot be ignored. Based on the oil-water two-phase seepage theory, Bernoulli equation and the continuity equation, we establish a numerical simulation model of post-fracturing flowback by considering the effect of fracturing fluid imbibition and obtain the pressure and flowback rate during the flowback process through programmed numerical calculation. The critical flow rate of fracturing fluid when the proppant starts to reflux is calculated according to the proppant backflow model. Then an optimization design method of flowback working system is formed based on the principle of controlling proppant backflow and rapid fluid flowback. The numerical simulation results are compared with the actual flowback data of LX3 well, and the flowback working strategy of M87 well is designed, and the effects of formation fluid viscosity and initial formation pressure on fracturing fluid flowback are analyzed. The results show that a phenomenon of formation fluid seepage to fractures is observed during the flowback, and the change of original formation pressure has a significant impact on fracturing fluid flowback, but the formation produced fluid has minor effects. The numerical results of flowrate and wellhead pressure of LX3 well are consistent with the field monitor data, with average errors of 13.8% and 15.5% respectively. It is verified that the flowback numerical model has high accuracy and can be used to guide the on-site fracturing flowback construction design in oilfield.

Numerical Analysis via Mixed Inverse Hydrodynamic Lubrication Theory of Reciprocating Rubber Seal Considering the Friction Thermal Effect

This study investigates how operating conditions such as ambient temperature and sealing pressure affect sealing performance for a typical U-cup seal. The developed analysis method combines inverse fluid lubrication (IHL) theory and the Greenwood–Williamson contact model (G–W model), and the effect of increasing surface temperature due to frictional heat generated between two surfaces is considered. Commercial FE software (ABAQUS) was used to simulate the interference fit analysis of rubber seals and the pressurized process. Through this model, the film distribution, working fluid leakage, and friction force in the sealing area were discussed according to the operating parameters, such as sealed pressure, rod velocity, and ambient temperature. The simulation results demonstrate the effect of fluid viscosity on oil film formation (which varies with ambient temperature), the effect of increasing the surface temperature, and the effect of surface roughness at a very small film thickness.

Viscous Damping Performance Analysis and Prediction of Axisymmetric Cylindrical Oscillating Buoys With Different Geometrical Configurations

Abstract With the intensification of the world's energy demand, clean and efficient marine energy has received more attention, and energy conversion devices are particularly important. As an important part of the oscillating wave energy conversion device, the hydrodynamic characteristics of cylindrical absorbers have a great impacton wave energy conversion efficiency. When cylindrical buoys with different bottom configurations heave under the action of waves, the oscillating motion and flow field become more complex. At present, potential flow theory is usually used to predict the motion response of cylindrical buoys in waves. Although the calculation speed is fast, there will be large errors due to the lack of consideration of the effect of fluid viscosity. To explore this error range, a three-dimensional numerical wave pool is established based on the viscous fluid theory and STARCCM+ software to study the response of buoy and wave coupling action considering the viscous effect. At the same time, based upon the potential flow theory, the analytical solution of the cylindrical buoy oscillating in waves is established. Combined with the computational fluid dynamics numerical simulation results, the oscillation laws of the buoys with different bottom configurations in waves with different periods are compared, and the effects of viscosity on the buoys' motion are also explored. According to the calculation results of floating buoy movement under viscous and nonviscous fluid, the statistical correction algorithmis adopted to obtain the viscous hydrodynamic correction algorithm of floating buoy movement based on the potential flow theory, and the feasibility is verified by viscous numerical simulation under other wave periods.

Experimental exploration on stable expansion phenomenon of sheath flow in viscous microfluidics

Microfluidic technologies have been developed for decades, especially in bio-chemical research and applications. Among them, sheath flow is one of the most well-known techniques used for focusing microparticles into extremely narrow widths. With varying Reynolds numbers, sheath flow displays different behaviors, including diffusion, stable thread, and turbulence. In this study, a previously unknown phenomenon, namely, stable expansion, is originally reported in a 200 × 70 μm microchannel with a Reynolds number ranging from ∼10 to ∼110. This stable expansion of focusing width differs from all the reported phenomena in the literature and is experimentally explored in this study. First, the phenomenon is introduced, identified, and comprehensively described using different experimental samples and methods. Subsequently, an image processing algorithm of post-analysis is proposed and calibrated by the theoretical results of stable thread. Based on the calibrated standard protocol, the effects of flow rates and a hysteresis phenomenon due to variation in the flow rate are revealed and studied. In addition, the effects of fluid viscosity are investigated by introducing a mixture of deionized (DI) water and glycerin. It is found that, in this 200 × 70 μm2 (weight × height) microchannel made of PDMS, the stable expansion phenomenon will occur when the Reynolds number exceeds 10, and the expanded width will increase with total flow rate. Moreover, it is found that the expanded width in a flow rate reducing route is displayed to be wider than that in an increasing route. On the other hand, a high viscosity contrast (&amp;gt;40) between the middle sample and sheath flows can eliminate the focusing width expansion. The results indicate that this originally revealed phenomenon is experimentally repeatable and worth further studying to help researchers better understand the mechanism of microfluidics.