Modelling the Relations of Rheological Characteristics with Composition of Plaster Mortar

The rheological properties of fresh plaster mortars, with varied contents of porous fillers and polymer admixtures, have been studied. The quantities of fine limestone and expanded perlite, and dosages of methyl hydroxy ethyl cellulose and ethylene vinyl acetate were varied in the experiment. Effective viscosity (at a shear rate from 0.045 to 5.705 s−1) and the thixotropy of the mixes were determined with rotational viscometer for 18 compositions (according to the design of the experiment). Each of the 18 viscosity curves were described with the Ostwald–de-Waele equation. The Experimental–Statistical models describing the dependencies of the parameters of the rheological model and of mix thixotropy on the composition factors were built on the obtained data. ES-models have allowed the individual and synergetic effects of mix components on the rheological characteristics to be evaluated. The expanded perlite powder can increase the viscosity by two times, probably due to its pozzolanic effect increasing the content of the CSH phase during cement hydration. The thixotropy can be increased by the quantity of limestone. The computational experiments with ES-models have made it possible for the information set, without a noticeable interrelation between rheological characteristics, to be stratified into subsets, in which such interrelations differ significantly.

Influence of temperature modes of processing chia seed meal gel on its rheological and functional-technological properties

The object of research. One of the alternatives of naturally occurring structuring agents with great potential in the food industry is the use of chia seeds. The meal obtained from the processing of chia seeds is the object of the above studies. Investigated problem. The study of changes in the emulsifying and rheological properties of chia seed meal, depending on the temperature treatment regimes, will determine the manifestation of the cryoprotective properties of this additive. This will help to solve the problem of deterioration in the quality of frozen split ends as a result of uncontrolled formation of ice crystals in the structure of the meat product. Main scientific results. Determination of the effect of heat treatment (heating to 70±2 C and freezing to -18 °C in the center) on the emulsifying properties of hydrated systems of chia seed meal showed that the emulsifying ability index increases by 7 % and 16 %, and the emulsion stability - by 8.7 % and 18.8 % according to the type of heat treatment. A decrease in emulsifying ability, emulsion stability, effective viscosity and shear stress was found in proportion to an increase in the degree of hydration. An increase in the indicators of effective viscosity and tangential shear stress as a result of heat treatment of prototypes was noted – by 45.3 % and 46.5 %, respectively. Freezing the hydrated dispersion of chia seed meal led to an increase in the ultimate shear stress by an average of 18.45 % compared to the untreated sample, the effective viscosity of the experimental dispersion did not change. The area of practical use of the research results. It can be used at food industry enterprises to improve the emulsifying and structural properties of products and their enrichment with dietary fiber. The innovativeness of the proposed solution. The results obtained prove the prospects of using this additive as a stabilizer, emulsifier and cryoprotectant in the technology of frozen meat products. The area of use of the innovative solution. This will ensure a consistently high quality of finished products and will improve the efficiency of production of a wide range of food products.

Lava Dome Morphology and Viscosity Inferred From Data-Driven Numerical Modeling of Dome Growth at Volcán de Colima, Mexico During 2007-2009

Magma extrusion, lava dome growth, collapse of domes, and associated pyroclastic flow hazards are among important volcanological studies. In this paper, we analyze the influence of the magma viscosity and discharge rates on the lava dome morphology at Volcán de Colima in Mexico during a long dome-building episode lasting from early 2007 to fall 2009 without explosive dome destruction. Camera images of the lava dome growth together with recorded volumes of the erupted lava have been used to constrain numerical modeling and hence to match the history of the dome growth by nudging model forecasts to observations. Our viscosity model incorporates crystal growth kinetics and depends on the characteristic time of crystal content growth (or CCGT) and the crystal-free magma viscosity. Initially, we analyze how this viscosity, CCGT, and the rate of lava extrusion influence the morphology of the growing dome. Several model scenarios of lava dome growth are then considered depending on the crater geometry, the conduit location, the effective viscosity of dome carapace, and the extrusion rates. These rates are determined either empirically by optimizing the fit between the morphological shape of modeled domes and that of the observed dome or from the recorded lava dome volumes. The maximum height of the modeled lava dome and its horizontal extent are in a good agreement with observations in the case of the empirically-derived extrusion rates. It is shown that the topography of the crater at Volcán de Colima is likely to be inclined toward the west. The viscosity of the modeled lava dome (∼1012 Pa s) is in a good agreement with the effective viscosity estimated experimentally from lavas of Volcán de Colima. Due to the interplay between the lava extrusion and the gravity forces, the dome reaches a height threshold, and after that a horizontal gravity spreading starts to play an essential role in the lava dome evolution. The model forecasts that the dome carapace of higher viscosity (∼1014 Pa s) influences the dome growth and its morphology during long dome-building episodes by retarding horizontal advancement and developing steep-sided eastern edge of the dome at the volcano. The developed model can be used in assessments of future effusive eruptions and lava dome growth at Volcán de Colima or elsewhere. History matching modeling of lava dome growth sheds a light on dynamic processes inside the dome and may assist in assessing stress state in the dome carapace and in forecasting the dome failures.

INVESTIGATION ON EFFECT OF SURFACE ROUGHNESS PATTERN TO DYNAMIC PERFORMANCE OF MEMS RESONATORS IN VARIOUS TYPES OF GASES AND GAS RAREFACTION

The average modified molecular gas lubrication (MMGL) equation, which is modified with pressure flow factors and effective viscosity, is utilized to analyze the squeeze film damping (SFD) on micro-beam resonators considering effect of surface roughness pattern in various types of gases and gas rarefaction. Then, effect of surface roughness pattern (film thickness ratio and Peklenik number) is discussed on the quality factor (Q-factor) of micro-beam resonators in various types of gases and gas rarefaction. Thus, effect of surface roughness pattern is significantly reduced as effective viscosity of gas decreases in higher mode of resonator and higher gas rarefaction.

Experimental Investigation of Oil/Water Emulsion Rheology in Electric Submersible Pump and its Effect on the Pump Head Performance

The presence of formation water throughout the oil well production lifetime is inevitable and consequently forming the dispersion or the emulsion due to the immiscibility of those two phases and the strong shear force acting in a rotating ESP. The formation of stable emulsion close to the inversion point will significantly increase the effective viscosity of an emulsion. This paper will present an experimental investigation of emulsion rheology inside the ESP and its effect on ESP performance under various oil viscosities and different water cuts (WC). Multi stages radial type ESP were assembled into a viscous flow loop which was initially developed by Zhang (2017). Emulsions at each WC formed from different oil viscosities, similar oil density, and surface tension. Multistage ESP was used to circulate oil/water emulsions in a close flow loop. Mass flowmeter measures both mass flow rate and fluid density, and the effective emulsion viscosity derived from an in-line pipe viscometer (PV) which locates downstream of the ESP discharge. The pressure transmitter is occupied in each pump stage to measure the pressure increment. The experiment results present in terms of pump boosting pressure at each water cut and the flow rate delivered by the pump. A Single-phase oil experiment was run at a different temperature to validate the accuracy of the PV. The data discrepancy of PV's viscosity and rotational viscometer is ±6%. The experiment results captured the emulsion's effective viscosity trend as a function of WC. A significant increase of effective viscosity close to the inversion point was observed, and it occurs due to a higher number of water droplets and hydrogen bonds which lead to an increase in hydrodynamic forces thus generating a tight emulsion. The experiment results reveal that a higher oil viscosity 70 cp reaches an inversion point at 30% - 35% WC. Meanwhile, for lower oil viscosity 45 cp reaches the inversion point at 35% - 40% WC since the turbulence increases with the decrease of oil viscosity. The increasing of effective viscosity in the water-oil emulsion induces higher pressure loss in the pump due to high friction loss, and it deteriorates the pump head. Nevertheless, as the WC increases further, the pump head will advance close to the single-phase water performance since the water turns as the continuous phase. Eventually, we can observe a prudent relationship in the pump performance in the change of emulsions effective viscosity as a function of WC. The inversion point phenomena occur at a different range of WC for different oil viscosity. Therefore, it is vital to set the possible range of operational conditions away from the inversion point. A better understanding of these aforementioned issues will lead to an accurate ESP design for optimum well performance.

Effective viscosity of lecithin solutions and fat emulsions of black soldier fly larvae with different lecithin content

Fats and oils irrespective of their application field are usually used as emulsions — disperse systems consisting of two immiscible liquids stabilized by an emulsifier. One of the main indicators for emulsions is effective viscosity, which characterizes behavior of liquid in flow. This indicator is also important for optimization of production processes, application and storage of emulsions. It was found that fat of black soldier fly (Hermetia illucens) larvae is close to coconut and palm oil by its qualitative and quantitative composition, which makes it one of the promising alternative sources of fats for the industry. Based on this fact, the aim of the study was to determine effective viscosity of lecithin solutions and fat emulsions of black soldier fly larvae depending on the lecithin content of 0.5-2.5 weight%. It was found that consistency of the lecithin solutions increased when its concentration increased from 0.5 to 2 weight%. The lecithin solutions with concentrations of 1.0-2.0 weight% demonstrated weak pseudoplastic behavior and those with the lecithin content of 2.5 weight% dilettante. Emulsions with fat of black soldier fly larvae showed twofold lower consistency compared to the lecithin solutions of the same concentration and weak pseudoplastic behavior, which manifestation did not depend on the lecithin concentration.

Shear orientation of nematic phases of clay nanosheets: processing of barrier coatings

When suspensions are exposed to shear forces, the particles may form ordered structures depending on their shapes, concentrations, and the material. For some processes, e.g., for wet-film coating, it is important to know how fast these structures form in shear fields and for how long the structures persist when the shear is relaxed. To obtain information on the particle structure formation and the decay time, the effective viscosity of nematic suspensions of Na-hectorite nanosheets was investigated by rheology employing a cone-plate measurement geometry. The necessary time for the formation textured nematic films could be deduced by carrying out effective viscosity measurements at constant time steps. Information could also be obtained on the lifetime of the platelet textures when shear is relaxed. All this information was employed to identify geometrical requirements for slot dies to produce barrier liners with nanosheet layers oriented parallel to PET substrates. Thereby, we obtained green and simple coatings that are in line with state-of-the-art high-performance materials such as metalized plastic foils in terms of oxygen barrier properties.

Impact of convection on the damping of an oscillating droplet during viscosity measurement using the ISS-EML facility

Oscillating droplet experiments are conducted using the Electromagnetic Levitation (EML) facility under microgravity conditions. The droplet of molten metal is internally stirred concurrently with the pulse excitation initiating shape oscillations, allowing viscosity measurement of the liquid melts based on the damping rate of the oscillating droplet. We experimentally investigate the impact of convection on the droplet’s damping behavior. The effective viscosity arises and increases as the internal convective flow becomes transitional or turbulent, up to 2–8 times higher than the intrinsic molecular viscosity. The enhanced effective viscosity decays when the stirring has stopped, and an overshoot decay pattern is identified at higher Reynolds numbers, which presents a faster decay rate as the constraint of flow domain size becomes influential. By discriminating the impact of convection on the viscosity results, the intrinsic viscosity can be evaluated with improved measurement accuracy.

Development of methods for evaluation of lubrication properties of hydraulic aviation oils

A method for evaluation of the lubricating and rheological properties of hydraulic oils in tribological contacts has been developed, which consists in online studying samples of commercial batches of oils on a software and hardware complex with visual evaluation of the kinetics of changes in the main tribological indicators of friction contact. Using a roller analogy, the operation of gears in the conditions of rolling with 30% sliding is simulated. Samples of AMG-10 oil from two producers are analyzed. It is established that with increasing temperature of lubricant for Sample 2 (“Kvalitet-Avia” AMG-10), a long-term restoration of protective boundary films of oil is observed and the period of their formation increases by 2.5 times, causing the implementation of a semidry mode of lubrication at start-up. The total thickness of the lubricating layer is 1.27 times less as compared with Sample 1 ("Bora B" AMG-10 oil), regardless of the lubricant temperature. Also, the rheological properties of the oils have been determined. Sample 1 exhibits low shear stresses at the level of 9.4 MPa and high effective viscosity, 4249 and 5039 Pa·s, at a volumetric oil temperature of 20 and 100 ºС, respectively. For Sample 2, with increasing oil temperature to 100 ºC shear stress increases by 1.15 times and the effective viscosity in contact decreases by 1.53 times. Additives present in Sample 1 are characterized by more effective antiwear properties and thus increase the wear resistance of contact surfaces in the conditions of rolling with sliding thanks to strengthening of the surface metal layers during operation, while Sample 2 undergoes strengthening-softening processes which reduce the wear resistance of friction pairs