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Stickiness and caking of fine powders such as in dry disrupted microalgae should be avoided in supercritical (sc) CO 2 extraction, because they negatively impact extraction rate and yield. To establish limits in water content of H. pluvialis cysts and extraction temperature, this work studied water-state diagrams of the powder. The powder’s squeeze flow behavior as a function of water content was useful to characterize the transition between glassy and rubbery states as water content increased. Water sorption ( W versus a w ) at 20 °C was represented using the Guggenheim–Anderson–de Boer equation, with a monolayer water content of 3.67% (d.b.). The glass transition diagram ( T g versus W w ) was represented using the Gordon–Taylor equation, with T gs = 88.3 °C (glass transition temperature of the anhydrous solids) and k = 3.49. The compression pressure necessary for squeeze flow behavior decreased 2.5–3 times at ambient temperature ( ca. 23 °C) as a result of an increase in water content from 3.8% (d.b.) to 10–15% (d.b.) at which level glass–rubber transitions manifested, and then kept relatively constant when the water content increased even further. Alternatives to prevent caking of H. pluvialis during scCO 2 extract include reducing the initial water content of the powder, increasing particle size by high-pressure agglomeration, and/or reducing the extraction temperature so as to prevent the glass–rubber transition that is responsible for sample stickiness. Taking into account that the scCO 2 extractions are carried out above ambient temperature (40 ⩽ T ⩽ 60 °C), we recommend reducing the water content of H. pluvialis powder to W ⩽ 5% (d.b.). [ABSTRACT FROM AUTHOR]

There are significant challenges in assessing the toxicity of nanoparticles in the environment in which effective methods for detection are crucial. An inexpensive method that uses superhydrophobic well with an evaporating droplet followed by a simple squeeze flow is described here and found to provide practical high nanoparticle collection from samples for detection. The process could be hastened by placing a radiant heater close to the droplet if temperature rises in the sample can be tolerated. [ABSTRACT FROM AUTHOR]

We develop an asymptotic solution for the plane squeeze flow of a viscoplastic medium. The standard lubrication-style expansions of the problem predict plug speed which varies slowly in the principal flow direction. This variation implies that the plug region cannot be truly unyielded. Our solution shows that this region is a pseudo-plug region in which the leading order equation predicts a plug, but really it is weakly yielded at higher order. We follow the asymptotic technique suggested earlier by Balmforth and Craster (1999) and Frigaard and Ryan (2004). We also provide comparison between analytical solution and numerical computations using the augmented Lagrangian method. The results of computations show presence of unyielded regions near the two stagnation points of flow close to centers of plates (that was found earlier by many researchers) and new additional unyielded regions at the outer edge of the material (both for short and long plates). The obtained analytical expression for the squeeze force is in a good agreement with the numerical results and previous results of Mitsoulis and Matsoukas (2003). [ABSTRACT FROM AUTHOR]

Thin-walled plates of polypropylene (PP), PP/acrylonitrile–styrene copolymer (SAN) blend,and PP/SAN/halloysite nanotubes (HNTs) blend nanocomposite were molded via microinjection-compression molding (μ-ICM). Hierarchical crystal morphologies were observed for the three plates. The SAN appeared mainly as microfibers in μ-ICM plates of PP/SAN blend and PP/SAN/HNTs blend nanocomposite, facilitating the formation of atranscrystals-dominated layer between shear and core layers in each of the two plates. Moreover, the SAN microfibers and HNTs synergetically increased the crystallinity of the PP. Tensile strength and microhardness of the PP plates were enhanced in the presence of SAN microfibers and HNTs. [ABSTRACT FROM PUBLISHER]

Instability at the interface separating different fluids, may develop under different conditions, leading to increased roughness of the boundary. A difference in viscosity of the fluids is usually responsible for viscous fingering, this occurs when the pressure on the low viscosity side is higher. We report here a reverse effect when a non-Newtonian fluid is squeezed between two plane surfaces by applying a force. We observe that a wave-like irregularity develops on the interface, though the viscosity of the air surrounding the fluid is negligible compared to the apparent viscosity of the thick potato starch gel under study. Development of the wavelength of the undulations as a function of the fluid composition and other factors is studied. We suggest a qualitative explanation for this effect, which is observed only in non-Newtonian fluids. [ABSTRACT FROM AUTHOR]

Nowadays thermoplastic composite materials are more and more used due to their specific excellent mechanical properties and a good recyclability. However, many difficulties are encountered during their forming processes, specially in the case of thermoplastic composites -TPC-. Therefore, consolidation of thermoplastic composites is becoming one of the most active research topics in composite manufacturing. Many processes proceed by heating prepregs to melt the polymer, then apply a compression in order to remove residual porosity trapped at the layers interfaces and consolidate the material. Thus the different layers containing the molten thermoplastic resin are compressed and squeeze flow occurs. Even if some modeling has been addressed, the flow occurring in the laminate, inside the yarns and in between the yarns requires rich 3D numerical descriptions with a fine enough description of the complex kinematics taking place in the laminate thickness. In this work we analyze the limits of lubrication based descriptions, justifying the necessity of proceeding with 3D descriptions. In order to alleviate the cost that such simulations involve, we employ an advanced discretization technique making use of an efficient in-plane-out-of-plane separated representation of the different fields involved in the model. Thus very fine descriptions are possible with a computational cost characteristic of 2D descriptions, as the ones making use of the lubrication hypotheses. [ABSTRACT FROM AUTHOR]

Squeeze flow of fluids between surfaces is important in rheology, material processing, lubrication and biomedical applications. The surfaces for squeezing can be solid and/or porous. In this work, the squeeze flow between a porous surface and a solid surface is examined with Newtonian model fluids and model fabrics used in composite processing. Given that the fluid is expected to impregnate the fabric, the permeability and the wettability of the fluid–fabric combination are of utmost importance. Constant velocity squeeze flow experiments were carried out with polyester and polyol resins, while glass fabrics with different sizings were used as the porous surfaces. To understand the variation of the normal force during squeeze flow, its scaling with squeeze gap is evaluated. The scaling is observed to vary from −3 to −1 for different squeeze flow experiments. Squeeze flow theories are used to examine the normal force variation for different fluid–fabric combinations. It is shown that a slip based squeeze flow model and a permeability based squeeze flow model can be used to understand the wettability and the permeability of a fabric with a specific fluid. [ABSTRACT FROM AUTHOR]

• Al 2 SO 4 based accelerator only enhances ettringite precipitation. • From 30 to 300 min, ettringite, C 3 S, and amorphous amounts remain unaltered. • Plastic zone of mix is identified by squeeze flow under continuous and cyclic load. • The plastic flow hardening occurs only for accelerated mixes. • Flow hardening is influenced by solid content and physical interlocking of ettringite. The buildability of a 3D printed concrete structure is influenced by the layer compression during printing, which in turn is governed by the rheological and early age mechanical properties of the mix. The study aims at understanding the effect of alkali-free aluminium sulphate-based accelerator on the microstructural evolution, which affects the macrostructural behaviour governing buildability of the structure. The effect of accelerator on hydration, phase composition, location and arrangement of ettringite, and porosity evolution of two paste systems with and without viscosity modifying admixture and superplasticizer is observed at initial hours. Further, fresh properties, yield stress evolution, and mechanical strength at early and later ages of the printable mix is evaluated. The squeeze flow test, which simulates the physical process of printing, is performed to understand the rheological characteristics of the mix under compressive loading in the initial hours. It is concluded that the precipitation of ettringite in large quantities at the initial hours controls the rheological and mechanical behaviour of the mix. The total ettringite formed increases for accelerated paste system at 30 min compared to the paste without accelerator. The ettringite is located at surfaces of clinker and interstitial spaces, with the crystals interlocked physically with each other. The squeeze flow test further suggests that the flow hardening increases tremendously on increasing the accelerator dosage due to an increase in solid volume fraction of ettringite and the resultant physical interlocking. Finally, a theoretical model is proposed considering the significance of ettringite interlocking and microstructure densification under compression on the plastic flow hardening for accelerated mixes. [ABSTRACT FROM AUTHOR]

The flow of complex fluids is routinely encountered in a variety of industrial manufacturing operations. Some of these operations use rheological methods for process and quality control. In a typical process operation small quantities of the process fluid are intermittently sampled for rheological measurements and the efficiency of the process or the quality of the product is determined based on the outcomes of these measurements. The large number of sample-handling steps involved in this approach cost time and cause inconsistencies that lead to significant variability in the measurements. These complications often make effective process/ quality control using standard rheometric techniques difficult. The effectiveness of control strategies involving rheological measurements can be improved if measurements are made online during processing and sampling-steps are eliminated. Unfortunately, online instruments capable of providing sufficiently detailed rheological characterisation of process fluids have been difficult to develop. Commercially available online instruments typically provide a single measurement of viscosity at a fixed deformation rate. This dependence on a single pre-determined shear rate restricts these instruments from identifying changes in the product or the process, especially if the viscosity at the pre-determined shear rate remains unaltered during these changes. We introduce an Online Rheometer (OLR) that uses small amplitude oscillatory squeeze flow to measure the viscoelastic properties of process fluids in-process and in real time under typical processing conditions. We demonstrate that with an appropriate measuring geometry and amplitude of oscillation, the frequency response of typical non-Newtonian fluids can be accurately measured in a process pipe. We also compare our results with other techniques that are typically used for process rheometry, critically evaluating the utility of the OLR technology for advanced process and quality control.

Liquid-phase migration in highly concentrated suspensions undergoing constant-force squeeze flow is modeled numerically by taking into account the time and position dependence of the rheological properties due to changes in the volume fraction of solids. This is done by coupling the equation of motion for a non-Newtonian material that behaves approximately as a Bingham plastic with a continuity equation that includes diffusive flux. The developed model was first tested with experimental data and then used to study the effect of various parameters on liquid-phase migration. [ABSTRACT FROM AUTHOR]

Liquid-phase migration and jamming of the suspended particles appear to be the cause of the previously reported drastic changes in the normal stress distribution in concentrated suspensions subjected to squeeze flow as the initial volume fraction is raised above a critical value. Liquid-phase migration was found to depend on the initial volume fraction of solids, the viscosity of the suspending fluid, and the size of the particles. Under some conditions, liquid-phase migration did not take place to any significant degree; however, under other conditions, the volume fraction of solids increased throughout the sample, but especially in the central region, as liquid was expelled from the test region in preference to the solids. Criteria for the occurrence of liquid-phase migration in suspensions undergoing squeeze flow are discussed in terms of dimensionless groups. [ABSTRACT FROM AUTHOR]

Abstract: This paper reports the first experimental comparison between squeeze-flow at controlled displacement rate and rotational shear at controlled speed for evaluating the rheological behaviour of mortars. Several Brazilian and European rendering products showed a wide range of workability behaviour in both testing modes. The flow curves and hysteresis effects during the shear cycle varied significantly, since the mortar's composition affects structural breakdown, interfacial slip and phase segregation. The latter plays a critical role during squeeze-flow and is the main reason for the higher loads required to deform the samples at lower rates. A gravimetric-based methodology was developed to assess phase segregation induced by rotational tests. Encouraging agreement between the methods was observed, with yield stress in the structured (unsheared) state showing a good linear correlation. For some mortars showing low segregation it was possible to compare shear viscosity and extensional viscosity and Trouton ratios between 20 and 40 were obtained. [Copyright &y& Elsevier]

ABSTRACT In high throughput microscopy, it is often assumed that the objects under investigation are fixed spatially. In addition, it is also presumed that the objects are sufficiently populated, otherwise there will be need to search through vast tracks of field of views before any recording can be done. The ability to collect objects at one location in the hydrated state is thus desirable and this is a challenge when the density of target objects in a sample is very low. In this work, we report that the generation of a squeezing flow from a circular coverslip compressing on suspensions is able to collect particulate (microbeads, fluorescent nanobeads and live algal cells) and non-particulate (EGFP) objects at the rim region of the coverslip. With a coverslip of 13 mm diameter, volumes between 2 µL and 4 µL were found to completely fill the coverslip without breaching the rims. Sample compression speeds between 100 µm/s and 1000 µm/s did not have any effect on object collection outcomes. In effect, the simple placement of coverslips on top the drop of sample by hand without a motorized translator was found to produce similar collection outcomes. Quantitative measurements confirmed that all the objects investigated were displaced and relocated at the rim regions to a very high degree. Microsc. Res. Tech. 76:767-773, 2013. © 2013 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Microinjection-compression molding was used to fabricate isotactic polypropylene part with microscale thickness. The combined effect of shear (up to the order of 105 s−1) and elongational deformations imposed by the Poiseuille (injection stage) and squeeze (compression stage) flow resulted in pronounced flow-induced crystallization under rapid quenching. Hierarchical crystalline morphology, characterized by two oriented layers, a transitional layer in between, and an isotropic core layer, was detected through the thickness in the upstream region initially filled in injection stage, whereas skin-core morphology appeared in the downstream region filled in subsequent compression stage. Under the molding conditions imposing sufficient strain rates, predominant shish-kebabs developed in the oriented layer. Furthermore, the oriented layer thicknesses, crystallinity, β-form content, and melting behavior of molded parts, all of which were closely correlated with the calculated strain rates, as well as the location of inner oriented layer could be manipulated via varying the compression-related parameters. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013 [ABSTRACT FROM AUTHOR]

Abstract: A standard method used to determine material properties of semi-solid slurries is the squeeze flow experiment; a fixed amount of material is squeezed under constant force or velocity and the relation between the force and the displacement of the sample provides information about the rheology of the slurry. The objective of this work is to contribute to the further development of the squeeze flow methodology in order to accurately determine material properties. This is achieved by a model that accounts for the finite yield stress and the thixotropy of the slurry. More specifically a structural viscoplastic model based on the Bingham plastic constitutive equation is proposed. The yield stress is assumed to vary linearly with the structural parameter which follows a first-order rate equation accounting for the material structure break-down and build-up. Numerical experiments of squeeze flow under either constant load or constant velocity are presented and discussed. Comparisons with their non-thixotropic counterparts are made in the case of compression under constant load. The development of the yielded/unyielded regions in relation to material structural changes is analyzed. The numerical results show that initially thixotropy does not affect the flow. However, once the structure is destroyed, the unyielded regions grow slower than the non-thixotropic case allowing for longer compression of the sample. Under constant force the structure may be destroyed at the early stages of the compression but at a later time it re-builds steadily till the cessation of the flow experiment. Under constant velocity, however, the structure is destroyed steadily. Depending then on the case, the final internal structure of the squeezed material can vary significantly. This is an important issue that needs to be taken into consideration in the evaluation of the material parameters. [Copyright &y& Elsevier]

Using pressure-sensitive films, the normal stress distribution is measured in suspensions of glass spheres in a Newtonian liquid undergoing constant-force squeeze flow. At volume fractions of solids up to 0.55, the normal stress distribution is independent of volume fraction and almost identical to the parabolic pressure distribution predicted for Newtonian fluids. However, at higher volume fractions, the normal stresses become an order of magnitude larger near the center and very low beyond that region. At these high volume fractions, the normal stresses decrease in the outer regions and increase in the inner regions as the squeezing proceeds. The normal stress distribution that results when the glass spheres without any fluid are subjected to squeeze flow is very similar to that for suspensions with volume fractions above 0.55, suggesting that the cause for the drastic changes in the normal stress distribution is the jamming of the particles in the suspension. [ABSTRACT FROM AUTHOR]

In this study, the problem of unsteady squeezing flow between circular parallel plates is performed. The similarity transformation is applied to reduce a governing partial differential equation (PDE) to a nonlinear ordinary differential equation (ODE) in dimensionless form. A new method, called the homotopy analytical method (HAM), is applied to obtain approximate analytical solution of this nonlinear equation. The obtained solutions, in comparison with the numerical solutions (fourth-order Runge–Kutta scheme), admit a remarkable accuracy. [ABSTRACT FROM AUTHOR]

In this manuscript, we address the long-standing question of whether a single theory for model plastic fluids is suitable to deal with the unidirectional compression problem in magnetorheological (MR) fluids. We present an extensive experimental investigation of the performance of MR fluids in slow-compression, no-slip, constant-volume squeeze mode under different magnetic field strengths (0-354 kA/m), dispersing medium viscosities (20-500 mPa·s) and particle concentrations (5-30 vol%). Normal force versus compressive strain curves reasonably collapse when normalizing by the low-strain normal force. Deviations from the squeeze flow theory for field-responsive yield stress fluids are associated to microstructural rearrangements under compression in good agreement with the so-called squeeze strengthening effect. Yield compressive stresses are found to scale as $\sim \eta^{0.33\, }\phi ^{2.0\, }$H. [ABSTRACT FROM AUTHOR]

Abstract: Performance of thermal interface materials (TIMs) used between a microelectronic device and its associated heat spreader is largely dependent on the bulk thermal conductivity of the TIM, but the bond-line thickness (BLT) of the applied material as well as the interfacial contact resistances are also significant contributors to overall performance. Hierarchically Nested Channels (HNCs), created by modifying the surface topology of the chip or the heatsink with hierarchical arrangements of microchannels in order to improve flow, have been proposed to reduce both the required squeezing force and the final BLT at the interfaces. In the present work, a topological optimization framework that enables the design of channel arrangements is developed. The framework is based on a resistance network approximation to Newtonian squeeze flow. The approximation, validated against finite element (FE) solutions, allows efficient, design-oriented solutions for squeeze flow in complex geometries. A comprehensive design sensitivity analysis exploiting the resistance network approximation is also developed and implemented. The resistance approximation and the sensitivity analysis is used to build an automated optimal channel design framework. A Pareto optimal problem formulation for the design of channels is posed and the optimal solution is demonstrated using the framework. [Copyright &y& Elsevier]

Abstract: We study the flow behavior of a model soft glassy material − an aqueous suspension of Laponite − when it is squeezed between two circular parallel plates of different roughness. Aqueous suspension of Laponite shows a time dependent aging behavior as reflected in increased elastic modulus as well as yield stress, both of which however also decrease with an increase in the strength of deformation field thereby demonstrating typical thixotropic character. In a squeeze flow situation, under both force as well as velocity controlled modes; we find the behavior to be independent of the initial gap between the plates. In a constant force mode, the gap between the plates decreases until it reaches a finite limiting value, which is found to increase with an increase in age of the material as well as with a decrease in the applied force. In constant velocity experiments, at large gaps between the plates, normal force varies inversely with plate separation. The normal force is higher for a sample aged for a longer time as well as for a larger velocity of the top plate. We observe that the experimental behavior follows prediction of Herschel–Bulkley model solved for the squeeze flow (with different friction coefficients at the two plates) reasonably well under weak deformation fields. However, under strong deformation fields, experimental behavior deviates significantly from the prediction of Herschel–Bulkley model. This deviation arises due to melting or partial yielding of Laponite suspension under large deformation fields causing decrease in the viscosity, elastic modulus and the yield stress. [Copyright &y& Elsevier]

Abstract: Based on lubrication approximation, the squeezing flow of biviscous fluids between two parallel disks with partial slip boundary condition was investigated. In addition to the solution of the kinematics in the bi-viscosity region leading to a cubic equation of the yield surface, the full explicit expressions of radial pressure gradient, pressure and squeeze force are given in the exact relationships. According to three dimensionless numbers, different behaviors are covered including Bingham fluid as a limiting case of bi-viscosity model. Besides, a critical force separating the Newtonian and biviscous regions of the flow is provided. However, for a flow of a Bingham fluid without wall slip, the expression of the applied force may be expressed or not according to the yield stress. This depends on the ratio value of the characteristic time of the fluid to the time scale of observation if it is very lower or higher than unity. [Copyright &y& Elsevier]

Abstract: A rheo-optic set-up originally designed for applying a shear strain to the material (CSS450 from Linkam) was used to generate a squeeze flow and follow the subsequent crystallization of the polymer. A polypropylene was used as the test material. The squeeze was achieved using the gap control motor of a hot stage conventionally used for shear measurements. The lubricated squeeze flow ensured a biaxial elongational strain in the sample. The crystallization kinetics is largely enhanced by the squeeze flow which, similarly to shear effects, leads to increase the nucleation. Moreover, x-ray measurements revealed that for our study squeeze flow promotes the formation of β crystalline phase. However, no specific crystalline orientation was obtained. [Copyright &y& Elsevier]

MR fluid squeeze mode investigations at CVeSS have shown that MR fluids show large force capabilities in squeeze mode. It was found that MR fluids in squeeze mode may be used in a wide range of applications such as engine mounts and impact dampers. In these applications, MR fluid is flowing in a dynamic environment due to the transient nature of inputs and system characteristics. The research presented in this article undertakes the problem of dynamic testing and modeling of MR fluid squeeze mounts. Dynamic tests of an MR mount are studied for different applied currents, initial gaps, frequencies, and excitation amplitudes. An effective mathematical model of the MR squeeze mount for steady-state testing was built which includes the effect of the inertia of the fluid. The results show that the compression force and the area of the hysteresis loop increase with the increase of excitation amplitude or applied current and it will decrease with the increase of frequency or initial gap. Also, the inertia effect becomes more significant for higher displacement frequencies. The mathematical model agrees with the test data very well during the compression process and it can be used for the dynamics analysis and the real-time control. [ABSTRACT FROM AUTHOR]

Bubble transport is of importance in many applications for non-Newtonian fluids, such as in the manufacture of composite materials where residual bubbles may impair electrical properties, surface appearance and the mechanical properties of the finished products. In this study, a model experiment is performed where a non-Newtonian fluid (grease) containing bubbles is compressed between two plates, whereby the motion of the bubbles is tracked and evaluated using Particle Image Velocimetry. The bubble motion is furthermore analytically modelled and coupled to the experimental results. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, the design, fabrication and experimental analysis of a piezoelectrically actuated micro squeeze flow rheometer is presented. Being only 30×30×0.5mm in size, the micro rheometer is sensitive to very small volumes of the order of 1–10nL of liquid and light enough to operate at frequencies in the kHz regime, an order of magnitude higher than normally attainable with conventional cone and plate rheometry. Initial experiments show that the response of the rheometer is dependent on the viscoelasticity of the fluid being tested. The prototype was used to measure the moduli of poly(dimethylsiloxane) (PDMS) of viscosity 10Pas, a non-volatile viscoelastic fluid, over the frequency range of 10–1000Hz. Results show good agreement between with the moduli measured using conventional rheometry up to 100Hz and with values extrapolated up to 1kHz. [Copyright &y& Elsevier]

Abstract: Squeeze flow in the gap between non-parallel circular plates of radius R is discussed. The test material is assumed to be a power-law fluid, with a no-slip boundary condition at the plates. If the mean separation between the plates is h, and the angle of inclination between the plates is ϕ ≪ h/R, the force on the plates is perturbed only at O(ϕ 2) and is increased by less than 10% if ϕ <0.35h/R. A torque O(ϕ) tends to return the plates to a parallel configuration. [Copyright &y& Elsevier]

Abstract: Food rheology focuses on the flow properties of individual food components, which might already exhibit a complex rheological response function, the flow of a composite food matrix, and the influence of processing on the food structure and its properties. For processed food the composition and the addition of ingredients to obtain a certain food quality and product performance requires profound rheological understanding of individual ingredients their relation to food processing, and their final perception. [ABSTRACT FROM AUTHOR]

Abstract: Studying the flow of highly concentrated granular suspensions represents a great challenge since they are characterized by a rather complex rheological behavior. In addition, macroscopic heterogeneities may be induced by the flow during rheological measurements due to the eventual relative motion between the liquid and the granular phases that may take place under certain conditions. Solid–liquid separation may ultimately lead to flow blockage. In the present investigation we consider experimentally the influence of the rheological properties of the suspending fluid on the transition between the flow and blockage of a concentrated suspension in a squeeze set-up geometry. The suspending fluid consists of an aqueous Xanthan solution for which rheological properties can be tuned by changing the polymer concentration. For each polymer concentration, it is shown that there exist flow parameters (squeeze velocity and gap thickness) for which one has a transition between homogeneous flow of the suspension and its blockage. Blockage diagrams, delimiting flowability and blockage zones, are then determined. Physical arguments are given to relate the evolution of the blockage diagrams to the flow parameters and rheological properties of suspending fluid. [ABSTRACT FROM AUTHOR]

Abstract: In order to understand the mechanisms whereby the molecules responsible for sensory stimuli are released in the mouth, the aim of this study was to characterise and predict the spreading of semi-solid dairy products between tongue and palate using four complementary approaches, namely sensory analysis, instrumental measurement and analytical and numerical modelling. The products studied were dairy gels, whose physical representation is a yield-stress fluid. In the instrumental approach, spreading in mouth was simulated by a test in which a constant volume of sample was squeezed between two plates. It was performed in two phases, the first phase with a prescribed speed and the second with a prescribed force. The influence of product rheology, interface conditions, forces involved and kinematics of displacement on spreading area were studied by combining the instrumental and modelling approaches. For the dairy gels studied in this work, the consistency K was the most influent parameter on the spreading area. Also worth noting were the good correlations between the results obtained by the sensory, instrumental and modelling approaches. The approach adopted in this study could be used to predict spreading in the mouth of food products or boluses with a rheological behaviour of the yield-stress fluid type. [Copyright &y& Elsevier]

When studying mechanical heart valve cavitation, a physical model allows direct flow field and pressure measurements that are difficult to perform with actual valves, as well as separate testing of water hammer and squeeze flow effects. Movable rods of 5 and 10 mm diameter impinged same-sized stationary rods to simulate squeeze flow. A 24 mm piston within a tube simulated water hammer. Adding a 5 mm stationary rod within the tube generated both effects simultaneously. Charged-coupled device (CCD) laser displacement sensors, strobe lighting technique, laser Doppler velocimetry (LDV), particle image velocimetry (PIV) and high fidelity piezoelectric pressure transducers measured impact velocities, cavitation images, squeeze flow velocities, vortices, and pressure changes at impact, respectively. The movable rods created cavitation at critical impact velocities of 1.6 and 1.2 m/s; squeeze flow velocities were 2.8 and 4.64 m/s. The isolated water hammer created cavitation at 1.3 m/s piston speed. The combined piston and stationary rod created cavitation at an impact speed of 0.9 m/s and squeeze flow of 3.2 m/s. These results show squeeze flow alone caused cavitation, notably at lower impact velocity as contact area increased. Water hammer alone also caused cavitation with faster displacement. Both effects together were additive. The pressure change at the vortex center was only 150 mmHg, which cannot generate the magnitude of pressure drop required for cavitation bubble formation. Cavitation occurred at 3-5 m/s squeeze flow, significantly different from the 14 m/s derived by Bernoulli's equation; the temporal acceleration of unsteady flow requires further study. [ABSTRACT FROM AUTHOR]

Abstract: Direct numerical simulations based on a thermal Lattice–Boltzmann method are utilized to compute the effective thermal conductivity of particulate thermal interface materials (TIMs). By simulating the squeezing process, we obtain the particle distribution in a situation similar to application. Therefore, there is no need to calculate the average thermal characteristics from several pre-defined random distributions. The effects of particle volume fraction, particle size, and particle to matrix thermal conductivity ratio on the thermal performance are investigated. The results for the effective thermal conductivity are in agreement with the existing semi-analytical and experimental results reported in the literature. [Copyright &y& Elsevier]

The split Hopkinson pressure bar (SHPB) technique is implemented to evaluate the transient response of a colloidal suspension exhibiting shear thickening at strain rates and timescales never before explored in a laboratory instrument. These suspensions are shown to exhibit a discontinuous transition from fluid-like (shear thinning) to solid-like (shear thickening) behavior when evaluated using rotational rheometry. The effect of loading rate on this transition time is studied for a particle volume fraction of 0.54 using the SHPB technique. It is shown that the time required for transition to occur decreases logarithmically with loading rate. From these results, we conclude that transition is not triggered by a characteristic shear rate, but rather a critical shear strain is required. Results from SHPB experiments performed up to Peclet numbers of order 107 are presented and discussed for 0.50, 0.52, and 0.54 particle volume fraction suspensions. [ABSTRACT FROM AUTHOR]

Abstract: The split Hopkinson pressure bar (SHPB) technique has been employed to evaluate the dynamic squeeze flow behavior of viscous Newtonian fluids. In this paper, the conditions under which classic Hopkinson bar data analysis is applicable for fluid specimens are discussed in detail. Requirements include the development of a parabolic flow profile and associated pressure distribution across the specimen. The times required for these processes to occur are calculated and compared with the experimental timescale in order to establish a specimen design criterion for valid SHPB testing. To evaluate this design criterion, an isothermal squeeze flow model describing the behavior of a cylindrical fluid specimen which includes inertial forces is used to predict the experimental results for a model Newtonian fluid. Good agreement between the theory and the experiment is obtained for thin specimens (∼1.0mm) across a wide range of shear strain rates (over 105 s−1). As a result of this study, the conditions under which valid SHPB experimental results may be obtained for a Newtonian fluid specimen are identified. [Copyright &y& Elsevier]

Abstract: Squeeze flow theory has been used as an effective tool to clarify how and which process conditions determine cavity-filling behavior in nanoimprint lithography (NIL). Conventional squeeze flow models used in NIL research fields have assumed no-slip conditions at the solid-to-liquid boundaries, that is, at the stamp-to-polymer or polymer-to-substrate boundaries. The no-slip assumptions are often violated, however, in micrometer- to nanometer-scale fluid flow. It is therefore necessary to adopt slip or partial slip boundary conditions. In this paper, an analytical mathematical model for the cavity-filling process of NIL that takes into account slip or partial slip boundary conditions is derived using squeeze flow theory. Velocity profiles, pressure distributions, imprinting forces, and evolutions of residual thickness can be predicted using this analytical model. This paper also aims to elucidate how far the slip phenomenon is able to promote the process rate. [Copyright &y& Elsevier]

A successful extrusion of fiber-reinforced cementitious composites requires a thorough understanding and proper design of the rheological properties of extrudates. The squeeze flow test is regarded as an effective method to evaluate the rheological properties of semi-solid-state fresh extrudates. Based on the strain rates derived from a generalized velocity field, the viscoplastic behavior of cementitious extrudates can be analyzed using the von Mises yield criterion combined with the nonlinear Herschel- Bulkley constitutive relationship. As far as the squeezing force is concerned, the theoretical predictions show good agreement with the experimental measurements. It is found that the bulging phenomenon of a specimen during the squeeze flow process can be depicted by the radial velocity component. Moreover, the velocity field of fresh cementitious extrudates under large plastic deformation is obtained. The present viscoplastic analysis of short fiber-reinforced cementitious extrudates under plastic flow is believed to be a promising mathematical tool toward optimization of formulation for the booming extrusion application. [ABSTRACT FROM AUTHOR]

Abstract: In the present work the squeeze flow technique was used to evaluate the rheological behavior of cement-based mortars containing macroscopic aggregates up to 1.2 mm. Compositions with different water and air contents were tested at three squeezing rates (0.01, 0.1 and 1 mm/s) 15 and 60 min after mixing. The mortars prepared with low (13 wt.%) and usual water content (15 wt.%) presented opposite behaviors as a function of elapsed time and squeezing speed. The first lost its cohesion with time and required higher loads when squeezed faster, while the latter became stiffer with time and was more difficult to be squeezed slowly as a result of phase segregation. Due to the increase of air content, the effects of this compressible phase became more significant and a more complex behavior was observed. Rheological properties such as elongational viscosity and yield stress were also determined. [Copyright &y& Elsevier]

Squeeze flow between parallel disks of a Newtonian fluid with variable viscosity is studied using a lubrication approximation. Analytical results are obtained for circumstances in which the viscosity distribution and instantaneous plate velocity and separation are specified. Equations describing the convection of viscosity and the time dependence of the plate separation are developed, although explicit solutions could not be obtained. Our analysis is extended to include two immiscible fluid layers, each having a different but uniform viscosity. As expected, all results reduce to the classical lubrication results for constant viscosity. [ABSTRACT FROM AUTHOR]

The rheological characteristics of soft foods such as peanut butter, mayonnaise and margarine were evaluated by the UW Meltmeter, a modified squeezing-flow device, applying a constant load under constant volume and changing area. Sample thickness profiles were measured as a function of time and the yield stress was calculated via a Herschel–Bulkley model as a measure of spreadability. Peanut butter exhibited the highest yield stress value (1.31–1.45 kPa) followed by margarine (0.80 kPa) and mayonnaise (0.31 kPa). Calculated values of biaxial extensional viscosity and consistency coefficient values calculated from the UW Meltmeter data followed the expected trends of relative spreadability of peanut butter, margarine, and mayonnaise. These results show that the UW Meltmeter is a relatively simple and reliable device for measuring yield stress and rheological properties of soft foods. PRACTICAL APPLICATIONS A new method has been proposed to measure yield stress of spreadable foods. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a rheological investigation of pure gypsum (PG) and a commercial gypsum–lime–filler plaster (CP) using the modified Vicat apparatus and squeeze flow method. The samples were tested at several different intervals after manual or mechanical mixing. The results confirmed squeeze flow to be more sensitive in determining fresh paste behavior than the modified Vicat apparatus. PG set faster when prepared in mechanical mixer than when manually mixed. Conversely, the CP composition presented longer setting when mixed mechanically. The study also included the analysis of two ready-to-use polymer-based products for leveling and rendering (drywall joint compound – DJC; acrylic putty – AP) measured by squeeze flow and compared to the commercial composition. [Copyright &y& Elsevier]

A backwards-tracking Lagrangian–Eulerian method is used to simulate planar viscoelastic squeeze flow. The momentum and continuity equations are discretized with the finite volume method and implicit immersed boundary conditions are used to describe objects in the domain. The viscoelastic squeeze flow, which involves moving solid geometry as well as free surface flow, is chosen for its relevance in industrial applications, such as adhesive parts assembly and hemming. The main objectives are to validate the numerical method for such flows and to outline the grid resolution dependence of important flow quantities. The main part of the study is performed with the Oldroyd-B model, for which the grid dependence is assessed over a wide range of Weissenberg numbers. An important conclusion is that the load exerted on the solids can be predicted with reasonable accuracy using a relatively coarse grid. Furthermore, the results are found to be in excellent agreement with theoretical predictions as well as in qualitative resemblance with numerical results from the literature. The effects of different viscoelastic properties are further investigated using the PTT model, revealing a strong influence of shear-thinning for moderate Weissenberg numbers. Finally, a reverse squeeze flow is simulated, highlighting important aspects in the context of adhesive joining applications. • Lagrangian–Eulerian used to simulate viscoelastic two-fluid flow. • Viscoelastic squeeze flow and extensional flow with applications for adhesive joining processes. • Viscoelastic flow with moving geometry treated with immersed boundaries and automatic adaptive grid generation. • Wide range of Weissenberg numbers for the Oldroyd-B model as well as the linear and exponential form PTT models. [ABSTRACT FROM AUTHOR]

Abstract: A model based on the response of a micro-rheometer which permits the measurement of the linear viscoelastic properties of small volumes of a fluid is described. The configuration involves a liquid being contained within a capillary bridge between two flat smooth parallel platens that are actuated sinusoidally using a compliant MEMS device. Approximate closed-form equations are derived to analyse the data taking account of both the capillary forces and those arising from viscoelastic flow. The approximate theory is compared to a full numerical simulation of the response of the MEMS rheometer and the validity is discussed. [Copyright &y& Elsevier]

Compression studies of electrorheological (ER) fluids have been impeded by not knowing the concentration of particles held between the plates. This study presents a technique that calls for using a constant volume setup that solves the problem. This study also includes results on how the concentration of particles and the viscosity of the dispersing oils affect the compression of an ER fluid. The conclusions of this study are that the constant volume squeeze flows of ER fluids are significantly different from what has been predicted with constant volume squeeze flow theories. [ABSTRACT FROM AUTHOR]

Abstract: Numerical simulations are undertaken for the transient squeeze flow between parallel plates under a constant load. The conservation equations are solved via the finite element method in space and the Crank–Nicolson method in time. The constitutive equation used to describe the semi-concentrated fiber suspension is an integral equation proposed by Dinh and Armstrong for fiber-filled Newtonian liquids. New results are obtained for both random and aligned fibers and for different levels of squeeze force, and these are compared with the corresponding Newtonian ones, which are slightly lower. The fiber orientation in the flow field is also obtained for different points in the material. [Copyright &y& Elsevier]