Variation In Flow Behavior Research Articles

Short communication: Estimation of ileal digestibility in chickens using single- and dual-tracer methods

Fractionation of digesta, as occurs during gastrointestinal transit in chickens, complicates accurate measurements of ileal digestibility using tracers. Dual-tracer methods using separate tracers for solid and fluid digesta phases may improve the accuracy of digestibility measurements when assumptions of the single tracer method are violated. The aim of the present study was to compare the apparent ileal digestibility (AID) of nutrients calculated with single- and dual-tracer methods in chickens fed diets varying in particle size, anticipating digesta phase separation in the proximal gastrointestinal tract. A total of 112 Dekalb White (BW: 1.53 ± 0.107 kg) and 112 Bovans Black (BW: 1.79 ± 0.127 kg) 29-week-old laying hens were distributed over 32 pens (seven birds/pen). Within breed, pens were randomly assigned to one of two experimental diets (coarse vs fine oat hulls; n = 8 replicate pens per diet/breed combination). Diets were supplemented with TiO2 (3 g/kg) and Co-EDTA (2 g/kg). On days 34, 35, or 36, birds were euthanised and digesta from the ileum was collected for tracer and nutrient analyses. Apparent ileal digestibility was subsequently calculated by single- and dual-tracer methods. Although coarse oat hulls were hypothesised to increase the fractionation of solid and fluid digesta phases, no breed or diet × method interactions were found. Using a single tracer method based on TiO2, AID of nitrogen (N) was overestimated by 3%-units (P < 0.01) compared with the dual-tracer method, whereas AID estimates of DM, starch, fat, and non-starch polysaccharides did not differ (P > 0.09) and precision of all AID estimates was improved. In conclusion, these results show that although from a conceptual perspective, dual-tracer methods are presumed to better account for the variation in flow behaviour of different digesta phases, AID estimates obtained by the commonly used single tracer method using solid-phase tracer TiO2 were more precise and only marginally differed from estimates obtained by a dual-tracer method using distinct tracers for solid (TiO2) and liquid (Co-EDTA) digesta phases. Considering technical and economical constraints, the single tracer method may thus be the method of choice in many situations. Only when digestibility of proteins or amino acids is of specific interest, single tracer methods using a solid-phase tracer may not suffice. Nevertheless, for both single- and dual-tracer methods, tracer selection is critical, and the choice of tracers should depend on the nutrient(s) of interest.

Material and wave relaxation phenomena effects on the rheology of Maxwell nanofluids

This study analyzed thermal and mass transport in magnetohydrodynamic Maxwell nanofluids over a cylinder stretched along the z-direction. The Cattaneo-Christov diffusion theory and Buongiorno’s model were employed to model the problem. The influences of Joule heating, chemical reaction rate, and heat generation were also considered. Appropriate similar variables were utilized to transform the constitutive equations. A semi-analytical method, namely the homotopy analysis method (HAM) in Wolfram Mathematica, was used to compute the problem solution. The results demonstrated the inverse variation in flow behavior with increased Maxwell parameter values; however, thermal and solutal transport displays the opposite trend. Additionally, the flow field showed resistance due to the presence of the magnetic field, while Joule heating enhanced the energy and mass transport phenomena. The results regarding the coefficient of skin friction along the radial direction are consistent with values reported in the literature.

Flow and heat transfer over a row of multiple semi-circular cylinders: selection of optimum number of cylinders and effects of gap ratios

The present work aims at studying the laminar flow and heat transfer characteristics of a Newtonian fluid over a row of semi-circular cylinders placed in uniform cross-flow configuration. The effects of spacing to diameter (gap) ratio, varied from 1 to 10, on the flow and heat transfer patterns have been studied at a Reynolds number of 100 for air as the working fluid. There has been no significant interaction in the flow at a spacing ratio greater than 4 and each semi-circular cylinder behaved more or less like the situation of a single cylinder. At lower gap ratios, the flow becomes more complicated due to the shear layer interactions that exist in the flow. The streamline and isotherm contours have been presented and discussed in detail for various gap ratios. The variation in flow behavior is explored further by studying the drag coefficient and lift coefficient signals of various semi-circular cylinders. The presence of a secondary frequency at low gap ratios that has adverse effect on the drag coefficient has been confirmed. The variation of measured global quantities, namely the drag coefficient, the Strouhal number and the Nusselt number have been studied and discussed in detail.

Influence of bridge pier shape on flow field and scour geometry

ABSTRACT The objective of the present paper is to investigate experimentally the flow field and the local scour around bridge pier of different shapes on a sediment bed. Experiments were carried out using individual piers of rectangular, oblong, trapezoidal, triangular and lenticular shapes with a common aspect ratio to compare the flow field and scour geometry among the shapes at identical flow conditions. The novelty of this study is to identify the scour structures due to different pier shapes and associated mean flows and turbulence, which are responsible for generation of scour. A 3D Micro-acoustic Doppler velocimeter (ADV) was used to record the instantaneous velocity data for five different discharges. It is observed that upstream scour depth was maximum at the leading edge of the rectangular pier, and minimum at the same location for the lenticular. Here, the horseshoe vortex is the main agent of the scour development for any kind of pier shapes, even for the sharp edges, though there is an immediate bifurcation of flow in the triangular and lenticular-nosed piers, where the scour formation is less than the others. The changes in mean velocities and Reynolds stresses due to the pier shapes are discussed and compared to that of flat-bed surface. Since the shape of the pier alters the flow and turbulence, one can expect large variations in flow behavior, and hence different scour formations are observed. The results can be used to identify scour structures around the piers of different shapes for designing and suggesting appropriate protection measures.

Hybrid event beds dominated by transitional‐flow facies: character, distribution and significance in the Maastrichtian Springar Formation, north‐west Vøring Basin, Norwegian Sea

AbstractHybrid event beds comprising clay‐poor and clay‐rich sandstone are abundant in Maastrichtian‐aged sandstones of the Springar Formation in the north‐west Vøring Basin, Norwegian Sea. This study focuses on an interval, informally referred to as the Lower Sandstone, which has been penetrated in five wells that are distributed along a 140 km downstream transect. Systematic variations in bed style within this stratigraphic interval are used to infer variation in flow behaviour in relatively proximal and distal settings, although individual beds were not correlated. The Lower Sandstone shows an overall reduction in total thickness, bed amalgamation, sand to mud ratio and grain size in distal wells. Turbidites dominated by clay‐poor sandstone are at their most common in relatively proximal wells, whereas hybrid event beds are at their most common in distal wells. Hybrid event beds typically comprise a basal clay‐poor sandstone (non‐stratified or stratified) overlain by banded sandstone, with clay‐rich non‐stratified sandstone at the bed top. The dominant type of clay‐poor sandstone at the base of these beds varies spatially; non‐stratified sandstone is thickest and most common proximally, whereas stratified sandstone becomes dominant in distal wells. Stratified and banded sandstone record progressive deposition of the hybrid event bed. Thus, the facies succession within hybrid event beds records the longitudinal heterogeneity of flow behaviour within the depositional boundary layer; this layer changed from non‐cohesive at the front, through a region of transitional behaviour (fluctuating non‐cohesive and cohesive flow), to cohesive behaviour at the rear. Spatial variation in the dominant type of clay‐poor sandstone at the bed base suggests that the front of the flow remained non‐cohesive, and evolved from high‐concentration and turbulence‐suppressed to increasingly turbulent flow; this is thought to occur in response to deposition and declining sediment fallout. This research may be applicable to other hybrid event bed prone systems, and emphasizes the dynamic nature of hybrid flows.

Fluid-Structure Interaction Study of Stenotic Flow in Subject Specific Carotid Bifurcation—A Case Study

Advances in numerical simulation have allowed the investigation of complex interaction of blood flow through elastic arteries which can be useful in demonstrating the disease progression and haemodynamics of cardiovascular diseases such as atherosclerosis. In the present study, patient is diagnosed with an occluded right Internal Carotid Artery (ICA) with partial stenosis at root of right External Carotid Artery (ECA) and partial stenosis at the root of left ICA. 3D patient specific carotid bifurcation is generated based on CT scan data using MIMICS-14.0 and numerical analysis is performed using FSI in ANSYS-14.5. The blood flow is assumed to be incompressible, homogenous and Newtonian, while artery wall is assumed to behave linearly elastic. The two-way sequentially coupled transient FSI analysis is performed using FSI solver for three pulse cycles and haemodynamic parameters such as flow pattern, Wall Shear Stress (WSS), pressure contours and arterial wall deformation are studied at the bifurcation and critical zones. The variation in flow behavior is investigated throughout the pulse and simulation results obtained reveals that there is a considerable increase in the flow behavior in partially stenosed carotid unlike occluded carotid. The investigation also demonstrates disturbed flow pattern especially at the bifurcation and stenosed zone elevating the haemodynamic variation during peak systole and later part of pulse cycle. The obtained results agree well with the clinical observation and demonstrate the potential of patient specific numerical studies in prognosis of disease progression and plaque rupture

Roll manufacturing of polymer microfluidic devices using a roll embossing process

The replication of micro-fluidic devices is increasingly utilised in various industrial fields, such as medicine and cell biology research, and in many applications: drug screening, sugar testers, chemical microreactors, microprocessor cooling (just reward) and micro fuel cells. The roll embossing process (R2R) is an efficient and economical method for fabricating micro/meso-features on the large-area surface of the polymer parts. In this work, we describe a roll embossing process for manufacturing micro-fluidic devices in different commercially available thermoplastic polymer using a micro-structured elastomeric pattern with low roughness (Ra<50nm) as a roller stamping tool. This work investigates the effect of processing parameters on material performance for manufacturing the micro-fluidic devices via a roll embossing process. They describes observations and surface topography analyses made to compare the replication quality of polymeric replicas obtained by filling micro-cavities using the roll embossing process.The results indicate that the variation in flow behaviour of polymer surface during roll embossing process is highly dependent on the forming temperature and rheological of polymer. In addition, the features of the elastomeric mould were replicated with good fidelity, retaining the original dimensions. By careful adjustment of process parameters, a micro-fluidic circuit with details in the range of μm was successfully transferred onto different polymeric films.

Rheological Investigation of MIM Feedstocks for Reducing Frictional Effects during Injection Moulding

An experimental investigation of the rheological properties for abrasive Metal Injection Moulding feedstocks is presented for different materials with dissimilar particle sizes and shapes. Tribological issues are inevitable since feedstock has up to 93 wt. % powder loading in the feedstock. In this study, each of the relatively soft carbonyl iron powder and the hard, abrasive Iron oxide powder are mixed with binder system, consisting of HDPE (High-density polyethylene), Paraffin Wax and S.A. (Stearic Acid) at different magnitudes of volumetric powder loading. The rheological properties such as flow rate (cm3/s), shear rate (s-1) and viscosity (Pa.s) are investigated for varying conditions of temperature and pressure. The properties of the feedstocks made from the two materials showed significant variation in flow behaviour (due to difference in inter-particle frictional behaviour) with changing process parameters as well as material parameters. Furthermore, to study flow behaviour of feedstocks apparent viscosity is plotted against temperature and shear rate in order to establish the sensitivity of temperature and pressure. Flow behaviour index was determined by analysing variation of viscosity with shear rate of feedstock. As expected, results show that the feedstock having iron oxide powder with hard irregular shaped particles exhibits a higher viscosity if compared to the spherical particles in the Carbonyl iron powder feedstock. It was observed that the feedstock containing iron oxide powder (75 wt. % powder loading) gives higher shear rate but the feedstock dissociates faster with increasing temperature, whereas carbonyl iron powder feedstocks (90 wt. % powder loading) were found to be more stable (dissociate less) at higher temperatures and flowed at a smaller shear rate. Additions of graphite powder to the hard and abrasive iron oxide powder (to facilitate reduction of the iron oxide during sintering) would also be expected to improve the flow behaviour of the iron oxide feedstock on account of the superior lubricating properties of the graphite powder.

Hot embossing holographic images in BOPP shrink films through large-area roll-to-roll nanoimprint lithography

Diffraction grating-based holographic images have been successfully replicated in biaxially oriented polypropylene (BOPP) shrink films through large-area roll-to-roll nanoimprint technique. Such hot embossing of holographic images on BOPP films represents a promising means of creating novel security features in packaging applications. The major limitation of the high-quality replication is the relatively large thermal shrinkage of BOPP shrink film. However, although an appropriate shrinkage is demanded after embossing, over-shrinking not only causes distortion in embossed images, but also reduces the various properties of BOPP shrink films mainly due to the disappearance of orientation. The effects of embossing temperature on the mechanical, thermal and optical properties as well as polymer surface morphologies were systematically analyzed. The results show that the optimal process parameters are listed as follows: the embossing temperature at 104–110 °C, embossing force 6 kg/cm2 and film speed 32 m/min. The variation in flow behavior of polymer surface during hot embossing process is highly dependent on the temperature. In addition, the adhesion from the direct contact between the rubber press roller and polymer surfaces is suggested to cause the serious optical properties failure.

Relationships between debris fan morphology and flow rheology for wet and dry flows on Earth and Mars: A numerical modeling investigation

Liquid water may have flowed on the Martian surface in the recent geologic past. Arguments for and against liquid water flows have been made, in part, using interpretations of the morphology of Martian gullies and their associated debris fans. On Earth, sediment transport on steep, debris-flow-dominated hillslopes is often assumed to be a nonlinear function of hillslope gradient. In detail, however, sediment transport on such slopes must also depend on the rheology of the mass movements that drive the majority of transport, both in magnitude and frequency. In this study, we attempt to provide a firmer basis for (1) interpreting flow constituents and/or rheology from debris-fan morphology on Mars and (2) modeling debris-flow-dominated hillslopes on Earth by developing a mass-conservative numerical model that links the rheology of wet and dry granular flows on steep slopes to the morphology of debris fans deposited at their base. Individual flows are routed from initiation points on a slope to stopping points at the base of the hillslope. Model predictions for the shape and average slope of the fans depend on flow rheology. Model results indicate that debris fans associated with dry granular flows may develop average slopes below the kinetic angle of friction. In both the dry and wet cases, the model results suggest that fan morphology depends on the mean properties of the flows involved in fan formation as well as the amount of variation in flow behavior between individual mass movement events. These results provide an improved basis for interpreting the morphology of debris fans on both Earth and Mars.

Dependence of dislocation creep of dunite on oxygen fugacity: Implications for viscosity variations in Earth's mantle

[1] Significant variations in flow behavior are known to exist both vertically and laterally in Earth's upper mantle. The sources of such variation may be thermal, compositional, or reflect differences in the chemical activity of components, such as oxygen, silica, and water. We report on the effects of oxygen fugacity on dislocation creep of dunite, with a view to understanding potential strength heterogeneity in the mantle. Although room pressure experiments on single crystals of olivine have shown a clear dependence of creep rate on oxygen fugacity, no prior deformation study of polycrystalline olivine-rich rocks has demonstrated such a dependency under high-pressure conditions. In this study we performed a series of dry creep experiments on a natural dunite under carefully controlled thermochemical conditions, including oxygen fugacity. The samples, cored from coarse-grained Aheim dunite with a grain size of ∼0.9 mm, were deformed under triaxial compression at oxygen fugacities fixed by either the iron/wustite or the nickel/nickel oxide solid state buffers, temperatures between 1150° and 1277°C, and differential stresses up to 300 MPa. The results of a global fit to all experimental data indicate a power law dependence of creep rate on oxygen fugacity, with an oxygen fugacity exponent of m = 0.20 ± 0.01, n = 3.6 ± 0.1, A = 102.6±0.3 s−1 MPa−3.6 Pa−0.2, and an activation energy for creep of 449 ± 7 kJ/mol. This activation energy is significantly less than the commonly used value of 535 kJ/mol because the earlier experiments made no corrections for the effects of oxygen fugacity. When applied to planetary interiors, an increase in oxygen fugacity by a factor of ∼103.5, from the iron/wustite to the fayalite-magnetite-quartz buffers, will result in a factor of ∼5 decrease in viscosity.

Anisotropic and tensile flow behaviors of Mg alloy AZ31B thin sheet in H24 condition at elevated temperatures

In this work, a series of experiments was performed to explore the effects of anisotropy, strain rate, and temperature on microstructure change and associated mechanical response of a rolled AZ31B-H24 Mg alloy sheet under tension. Tensile tests were carried out on specimens in the 0, 45, and 90° to the rolling direction, using initial strain rates in the range of 4×10−3 to 1×10−1s−1 at temperatures of 250 and 370°C. Results showed that variations in flow behavior under tension could be related to the changes in microstructure resulting from applied tensile conditions. Resultant microstructures, such as degree of dynamic recrystallization, grain growth, and shape of the grain, were associated with temperature, strain rate, and tensile loading direction. The initial texture influenced the variations in changes in microstructure and mechanical properties upon testing in different directions. The specimens upon testing in the 45° to the rolling direction yielded higher m-value, lower strength, and greater elongation to failure under all test conditions.

Fundamental Flow Characteristics in a Small Columnar Latent Heat Storage Bath

Latent heat storage is one of the key technologies to utilize waste heat because this technology enables to store thermal energy in high density and for long time. This study focuses on flow characteristics in heat storage bath in form of direct contact since it has great effects on operation limit or thermal efficiency. The two-phase flow behavior of immiscible fluids was measured in a small cylindrical heat storage bath which had a nozzle at the center of the bottom and was settled in a rectangular transparent tank. A heating medium oil was fed from the nozzle to the bath half filled with a phase change material (PCM). Two series of the experiments were carried out. One was cold isothermal experiment which used water as model PCM, and the other was heat storage experiment which used sodium acetate trihydrate as the PCM. The formation behavior of the heating medium droplet changed from single droplet at nozzle outlet, single droplet from liquid column, multiple droplet from liquid column to atomization at the nozzle with increase in inflow velocity of heating medium. At the interface between the PCM and the heating medium, the heating medium droplets accumulated, coalesced, enlarged and disrupted, then the heating medium was released from the PCM layer. Furthermore the variation of flow behavior in the heat storage bath with progress in phase change of the PCM was elucidated.

Hot-deformation behaviour of spray-formed 2014 Al + SiC P metal matrix composites

In the present investigation, discontinuous SiC particle reinforced 2014 Al alloy based metal matrix composites have been produced by spray forming process. The composites contained average particle sizes of 17, 30 and 58 μm in the range of 5–11 vol.%. The composites were tested for their compressive flow behaviour, in unlubricated condition, at strain rates of 0.01, 0.1 and 1.0 s −1 and at temperatures of 150, 300 and 450 °C. The flow stress for 30 μm size particle reinforced composite increased with increasing particle content from 0 to 8.5 vol.%, but decreased at 11 vol.%. The flow stress invariably decreased at larger strain values during deformation. The increase in particle size from 17 to 30 μm led to increase in flow stress at 300 °C, whereas, it decreased at 450 °C. The strain rate sensitivity ( m) for 30 μm size particle reinforced composite was close to 0.16 up to 8.5 vol.%, whereas, for the composite with 17 μm size particles it decreased to 0.13 with increasing volume fraction up to 8.6 vol.%. The m values increased from 0.13 to 0.15 with increase in particle size from 17 to 58 μm. The variation in flow behaviour has been attributed mainly to particle fracture and debonding at particle/matrix interface, confirmed by microstructural features of the deformed samples. The major particle fracture events were recorded at low temperature and low strain rate of deformation. The composite with 30 μm size particles showed enhanced restoration process based on the low value of calculated apparent activation energy for diffusion (80–100 kJ mol −1). This deformation behaviour of the composites has been discussed in light of microstructural observations and the void formation during deformation.

The co-extrusion of metal-sheathed high-temperature superconductors

The co-extrusion of copper cans containing Ag-clad high-temperature superconductor (HTS) cores using a direct extrusion technique was investigated. Composite rods were produced by simultaneous cladding and consolidation of the superconducting material, however, a range of deformation behaviour occurred, including core and sleeve fracture, non-uniform wavy core and sound flow. The flow patterns varied consistently as the initial core diameter ( D ci) and reduction ratio ( R) were varied, allowing domains of specific deformation behaviour to be defined. The large variation in flow behaviour was also attributed to stiffness mismatch between the HTS core and the cladding metal.

Rheology of Sea Buckthorn (Hippophae rhamnoides L.) Juice

Juice extracted from sea buckthorn fruits was subjected to dynamic rheological measurements in a controlled stress rheometer. Sea buckthorn juice exhibited wide variations in flow behavior from pseudoplastic to dilitant with increasing temperature. The power law model suitably (r >/= 0.975, P</= 0.001) described the shear-stress versus shear-rate data of the juice. Changes in apparent viscosity of the juice with increasing temperature obeyed the Arrhenius law at shear stress above 1 Pa but deviated from it at low shear stress of 0.1 Pa. The rheological behavior of sea buckthorn serum obtained after centrifugation of the juice was similar to those of the juice and sucrose solution at high shear rate but differed from them at low shear rate. Addition of ethanol insoluble substances up to 7% (w/v) to the juice changed its rheological behavior to resemble that of a sea buckthorn juice concentrate at 48 degrees Brix, although frequency dependence was unaffected above 1 Hz. Sea buckthorn juice was found to be thermostable within the temperature range from 25 to 70 degrees C, although critical changes occurred in juice components above 70 degrees C.

The effect of particle size distribution on the antithixotropic and shear thickening properties of coal–water dispersions

The shear thickening rheology of coal–water suspensions prepared from six different naturally generated particle size distributions with mass median particle diameter d50 from 0.8 to 28 μm were investigated. Refined coal samples were thoroughly deflocculated with an anionic dispersant in water at particle concentrations from 47.7 to 56.4 vol %. The variations in flow behavior of the dispersions were observed in Couette flow as a function of shear rate in ramp tests and of time as a constant rate of shear was applied. Ramp test results indicated a decrease in the severity of shear thickening with increasing particle size distribution. Discontinuous shear thickening that occurred with the smaller particle sized samples was found to be approximated by a single function of the particle concentration reduced by the maximum packing fraction. The experimental results from constant shear rate experiments were compared in terms of the rate of antithixotropy, the extent of stress increase, and the total energy dissipated prior to shear thickening, as determined from characteristic points in the stress‐time rheograms. Significant differences in the shape of the antithixotropic curves were observed for the different particle size distributions. The magnitude of stress increase observed during the antithixotropic event was found to diminish with increasing particle size distributions which limited the detection of the antithixotropic event at the larger sizes. The extent of stress increase for the smaller particle sized samples, i.e., d50 < 3 μm, was such that the antithixotropic shear thickening appeared to dominate the flow behavior. A bimodal mixture of particles at d50 = 0.77 and 7.9 μm was also examined. An 8% increase in volumetric particle concentration was observed when compared to a monomodal suspension with equivalent d50 and average viscosity. No antithixotropic tendencies were observed with the bimodal suspension.

Deformation Mechanisms and Solid-Solution Strengthening in Ordered Alloys

ABSTRACTFundamental to understanding the results of alloy design studies, is the need for understanding the intrinsic role of solutes in a particular compound. For many compounds such an understanding must be built from a systematic exploration of the role of deviations from the stoichiometric composition as well as the role of ternary solute additions on the variation of flow behavior. Within most intermetallic systems the problem is complicated since the fundamental mechanisms of flow are not well established and, in those systems where these mechanisms are known, thermal activation can lead to dislocation-core transformations and changes in the operative slip systems with temperature. In general, flow may be governed by more than one dislocation process at a given temperature and deformation twinning may be a major contributing deformation mechanism. The problem of isolating the mechanisms of solid-solution hardening may, therefore, require treatment as a problem of combined strengthening mechanisms operating in parallel. This paper reviews the key aspects of deformation mechanisms and solute strengthening in intermetallic alloys. Classical elastic theories of solute hardening serve as an origin, from which, the progress made to date in isolating the mechanisms of solute hardening in ordered alloys is discussed.