Influence Of Rheological Parameters Research Articles

Influence of rheological parameters on the performance of the aerated coaxial mixer containing a pseudoplastic fluid

Gas dispersion in non-Newtonian fluids has numerous applications in many chemical and biochemical applications. However, the effect of the power-law model constants describing the rheological behavior of the pseudoplastic fluid has never been investigated. Thus, a numerical model was developed to simulate the hydrodynamics of gas dispersion in non-Newtonian fluids with a coaxial mixer. Then, a set of experiments was conducted to assess the mass transfer efficacy of a coaxial mixer to benchmark the numerical model. In this regard, various methods, including dynamic gassing-in and electrical resistance tomography methods, were used to quantify the mass transfer and gas hold-up profiles. The influence of fluid rheological properties, gas flow number, and rotating mode on the power consumption, mass transfer coefficient, bubble size profile, and hydrodynamics were examined both experimentally and numerically. The response surface model (RSM) was employed to explore the individual effects of power-law model constants on mass transfer. The RSM model utilized five levels for the consistency index (k), five levels for the flow index (n), and three levels for the gas flow number. The statistical model proposed that the absolute model constants for the flow and consistency indices were 0.0012 and 0.0010, respectively, for the co-rotating mixer. Conversely, for the counter-rotating mixer, these constants were 0.0010 and 0.0013, respectively. Therefore, this study revealed that the co-rotating coaxial mixer was well-suited for dispersing gas within a fluid with high consistency. In contrast, the counter-rotating mixer proved effective in enhancing gas dispersion within a fluid with a lower flow index.

Research on rheological behavior of fresh concrete single-cylinder pumping based on SPH-DEM

In contrast to traditional approaches to simulating fresh concrete, the model applied here allows issues such as liquid phase and the motion of sub-scale particles to be considered. The rheological behavior of fresh concrete materials was investigated, and the slump test and pumping process of fresh concrete were simulated by combining the smooth particle hydrodynamics coupled with discrete element method. Based on Bi-viscosity model and Bingham model, linear and nonlinear fitting of rheometer data and the derivation equations were educing. Bi-viscosity model and the Bingham model were compared in slump test. The results show that the Bi-viscosity model is more accurate in simulation, and the error percentage is less than 10%. The Bi-viscosity model was used to simulate and predict the results of slump experiment, and the influence of rheological parameters on the slump velocity and shape was obtained. The simulation analysis model of concrete single-cylinder pumping is established, and the experimental and simulation analysis models are compared. The results show that the SPH-DEM pumping pressure prediction is very close to the experimental results.

Influence of rheological parameters on cement slurry penetration characteristics of novel oscillating grouting technology

Traditional grouting techniques are primarily based on stable-pressure grouting, with slurry penetration performance limited. Research on the penetration behavior of pulsating slurry is relatively scarce, with even less research focused on the influence of slurry rheological parameters.This paper proposes an efficient oscillating grouting technology (OGT) that can generate pressure pulses and periodically change the direction of slurry motion. Through experiments and numerical simulations, its working mechanism is investigated, and the penetration distance of oscillating grouting and steady pressure grouting is compared under different soil parameters (porosity and particle size). The effect of cement slurry rheological parameters (viscosity of the Newtonian fluid and the K, τ0 and n, of the Herschel-Bulkley fluid) on penetration distance, grouting pressure, pressure pulse amplitude, and oscillating frequency are studied. Finally, the correlation analysis between penetration behavior, oscillating parameters, and rheological parameters is conducted. The results show that the oscillatory switching of the slurry is related to the interaction of vortexes within the tool, and the switching process leads to the generation of pressure pulsations. Under different soil parameters and rheological parameters, the penetration distance of oscillating grouting is larger than that of steady-pressure grouting. Furthermore, due to the pressure recovery process within the oscillatory grouting tool, the oscillating grouting exerts less pressure on the soil, which can prevent soil fracturing. The results also indicate that the oscillatory grouting requires a certain level of flow resistance to achieve optimal effect, but excessive resistance can impede the slurry switching process and reduce the penetration distance. And the optimal values for K, τ0 and n are around 0.015 Pa·sn, 1.5 Pa, and 0.5, respectively. According to the correlation analysis, oscillating frequency is positively correlated with penetration distance. Average pressure and rheological parameters are negatively correlated with penetration distance.

Pipe Flow of Viscoplastic Fluids and Analytical Predictions of Concrete Pumping Based on the Shear-Stress-Dependent Parabolic Model

This study investigates the Hagen–Poiseuille pipe flow of viscoplastic fluids, focusing on analytical predictions of concrete pumping using the shear-stress-dependent parabolic model, extending analytical studies to a nonlinear rheological model with easily accessible experimental parameters. Research novelty and highlights encompass solving the steady laminar pipe flow for viscoplastic fluids described by the parabolic model, presenting detailed results for the two-fluid parabolic model, and introducing a computational app implementing theoretical findings. The parabolic model outperforms linear models, such as the Bingham model, in accuracy by accounting for the nonlinearity in the flow curves (i.e., shear stress and shear rate relations) of pumped concrete. The influence of rheological parameters on these relations is analyzed, and their versatility is demonstrated by a Wolfram Mathematica-based application program. The analytical approach developed in this work is adaptable for other models with shear stress as the independent variable, offering valuable insights into viscoplastic fluid flows.

Modelling the transport of tailings after Mount Polley tailings dam failure using multisource geospatial data

Tailings dams (TD) are usually located in valleys that are not easily accessible and hence one global digital elevation model (DEM) is used in most of the TD breach outflow modelling studies but the challenges this impose when calibrating visco-plastic rheological models has not been fully investigated. Implications of using GeoBase DEMs for model calibration is studied by comparing it with a model that is calibrated using a merged DEM generated from multiple products. The influence of rheological parameters, roughness coefficient and sediment concentration ( Cv) on simulated variables is studied. It was concluded that when GeoBase DEM was used for back analysis of the event, physically meaningful set of rheology values could not be assigned. Flow behaviour was strongly influenced by Cv and least influenced by Manning’s values. Runout distance was more sensitive to viscosity than yield stress. Mudflow depth and arrival time increased with increase in viscosity and Cv.

ДИНАМИКА АДАПТИВНОГО ПРИВОДА СТЫКОВОЧНОГО МЕХАНИЗМА

Many studies usually use two methods to determine wave characteristics. First-The instantaneous state of the medium corresponding to a certain fixed moment of time is investigated. Second-The change in time of the state of the body in question at some fixed point is investigated. If studies are carried out taking into account the rheological properties of the material of the system in question or, if there is an environment surrounding the system, which also generally exhibits rheological properties, the use of these methods is significantly difficult. In such cases, the influence of rheological parameters on the components of the complex phase velocity at certain values of the vibration frequencies is studied.

Effect of surface contact angle on the wall impingement of a power-law liquid jet

This study theoretically investigated the impinging liquid sheet, formed by a power-law liquid jet obliquely encroaching on a wall surface. Based on the control volume method, the governing equations of the liquid sheet were established through force balance analysis at the curved edge. To solve the governing equations, energy conservation in the theoretical model was also considered throughout the impinging process. Typical working conditions were selected to validate the theoretical predictions. The results showed that the theoretical inner counter of liquid sheet agreed well with experimental data. Based on the theoretical model, influence of rheological parameters, surface contact angle, and surface tension coefficient are discussed, respectively. It is concluded that the surface contact angle could affect liquid sheet size by changing the total surface tension force at the rim, as well as the surface energy variation in the energy conservation equation.

CLASS OF PLANE PROBLEMS ON THE EFFECT OF MOVING LOADS UNDER A NONLINEAR LAW

The present work is devoted to the dynamics stability study of wave processes of plane and circular elements, and it is also being considered a class of plane tasks about moving loads effect on the surface of a layered elastic half-plane under the nonlinear law of stress versus deformation. While studying the wave processes of planar and circular elements in deformable bodies, the concept of phase velocity is introduced as the rate of phase medium change. In the case of harmonic vibrations of a cylindrical shell, the phase speed is expressed through the frequency of natural oscillations of freely supported along the edges of the shell, and therefore, the investigation of waves in plane and circular elements has the most direct relation to the problem of determining the own forms and vibration frequencies of finite length shells. If the studies are carried out taking into account the material rheological properties of considered system, there is a surrounding system environment, also generally displaying rheological properties, the use of these methods is considerably difficult. In such cases, the influence of rheological parameters on the components of the complex phase velocity is studied in definite values of the vibration frequencies. At present article, it is being considered an approximate solution of the nonlinear task about the effect of a moving load on an elastic layer lying on an undeformable base under the nonlinear stress law of depending strains from deformations.

Numerical study of nonlinear problems in the dynamics of thin-walled structural elements

Mathematical model of the problem of vibration of thin-walled structural elements has been constructed based on Kirchhoff-Love theory. The problem is reduced, using the Bubnov-Galerkin method, to the solution of a set of nonlinear integro-differential Volterra type equations with weakly-singular kernels of relaxation. A numerical method based on the use of quadrature formulae being used for their solution. The influence of rheological parameters of the material on the values of critical velocity and amplitude-frequency characteristics of viscoelastic thin-walled structural elements is analyzed. It is shown that tacking account viscoelastic properties of the material of thin-walled structures lead to a decrease in the critical rate of gas flow.

Investigation on rheological properties of bitumen based on rheological parameters of maltenes

ABSTRACT Previous research studies have indicated that each bituminous component plays a different role in rheological properties of bitumen. However, a few literature studies focus on rheological parameters of bitumen at component level. This paper aims to investigate the intuitive influence of rheological parameters of maltenes on rheological properties of bitumen. Saturates, aromatics, resins and asphaltenes (SARA) were firstly separated from two base bitumens and Styrene–butadiene–styrene (SBS)-modified bitumen. Dynamic shear rheometer (DSR) was applied to characterise the rheological properties of three bitumens and their maltenes. Temperature and frequency sweep tests were conducted to obtain six rheological parameters, including complex modulus, phase angle, complex modulus index, rutting factor, fatigue factor and rheology cracking index. The results indicate that the elasticity of base bitumen in low-temperature stage is mainly provided by resins and aromatics compared with the sole contribution of aromatics in SBS bitumen. The promotion effect for enhancing anti-rutting ability of resins in base bitumen is superior to that of SBS bitumen. Saturates, with a rutting factor of less than 1 kPa, lead to a passive effect on deformation resistance at higher temperatures of bitumen. Maltenes show a different contribution rate of improvement of fatigue resistance in a descending order of saturates, resins and aromatics. Aromatics with superior cracking resistance contribute to the enhancement of ductility for bitumen in contrast to resins with a larger rheology cracking index. The intuitive analysis on maltenes will facilitate further investigation of the interaction mechanism for bitumen modification and rejuvenation so as to enhance rheological properties of bitumen.

Numerical study of cuttings transport by drilling polymer solutions

This paper presents the results of laboratory tests and numerical simulation of polymer drilling fluids. The influence of the rotation speed on the values of the pressure ratio and cutting transport is studied. The influence of rheological parameters on the efficiency of cuttings transport is investigated.

Numerical Analysis of thermal behavior in agitated vessel with Non-Newtonian fluid

For some ten years, several analytical problems have not been solved by the Navier-Stokes equation; hence numerical methods also known by 'Computational Fluid Dynamic' (CFD) have been developed. In the present paper, we have described in depth numerical study of the basic fluid mechanics problem and heat transfer of yield stress fluid flow with regularization model of Bercovier and Engelman [1] in a cylindrical vessel not chicaned equipped with an anchor stirrer by using computational fluid dynamics (CFD) based on the finite volumes method discretization of Navier - Stokes equations formulated in variables (U.V.P). We have studied the effect of inertia and the plasticity influence; we have analyzed also the influence of rheological parameters on the hydrodynamic flow behavior, such as the velocity components and the power consumption.

Numerical Study of Fluid Behavior Induced by Anchor Impeller in a Stirred Vessel

In the present paper, we have described in-depth numerical study of the basic fluid mechanics problem of yield stress fluid flow with regularization model of Berovier and Engelman in a cylindrical vessel not chicaned equipped with an anchor stirrer by using computational fluid dynamics (CFD) based on the finite volumes method discretization of Navier - Stokes equations formulated in variables (U.V.P). We study the effect of inertia and the yield stress influence by the variation of Hedström number on the flow; we have analyzed also the influence of rheological parameters on the hydrodynamic flow behavior, such as the velocity components and the power consumption.

A Comparative Study of Two Mechanical Agitated System in Case of Non-Newtonian Fluids

In this work the characterization of hydrodynamic fields of incompressible yield stress fluid with regularization model of Bercovier and Engelman in a cylindrical vessel not chicaned equipped with circular anchor stirrer was undertaken by means of numerical simulation using computational fluid dynamics. Simulations flow of a Bingham fluid agitated by straights blades anchor was used to validate the rheological model implemented of the fluid treated. The flow structures, and especially the effect of inertia, the plasticity and the yield stress, are discussed. We have analyzed also the influence of rheological parameters on the hydrodynamic flow behaviours, such as the velocity components and the global characteristic like power consumption.

Influence of rheological parameters on the velocity of erythrocytes passing nailfold capillaries in humans

One thousand two hundred and fifty-six subjects (apparently healthy subjects and patients with cardiovascular diseases) were registered in a prospective study including demographical and clinical data, rheological parameters (hematocrit, plasma viscosity, erythrocyte aggregation, erythrocyte deformability) as well as the erythrocyte velocity in human nailfold capillaries under resting and postischemic conditions. A multivariate regression analysis showed that under resting conditions there was no correlation between rheological parameters and erythrocyte velocity in capillaries. The blood flow regulation seemed to be so effective, that pathological changes of the blood fluidity showed no effect on the velocity of an erythrocyte passing the capillaries. During vessel paralysis in the early phase of the postischemic hyperemia following a stasis of three minutes in the vasculature distal to a pressure cuff at the upper arm a very clear correlation between the plasma viscosity and the maximum postischemic erythrocyte velocity in ipsilateral cutaneous capillaries could be observed (p < 0.0001) while none of the other rheological parameters seemed to play a role. In a subgroup of diabetic patients the erythrocyte aggregation (measured during stasis) also correlated with the erythrocyte velocity (p = 0.0175) besides the plasma viscosity. This shows that a correlation of rheological parameters with the capillary perfusion could only be found during vessel paralysis. In of diabetic patients besides the plasma viscosity also the erythrocyte aggregation correlated with the mean capillary erythrocyte velocity. Theses results are in agreement with the hypothesis from Barras that plasma viscosity determines the perfusion of microvessels. Under certain conditions e.g. diabetic disorder, also the erythrocyte aggregation plays a role.

The relaxation effects of a saturated porous media using the generalized thermoviscoelasticity theory

In this paper, a model of the generalized thermoviscoelasticity for a saturated porous media is used. Taking the rheological properties of the volume into consideration, it is developed on the basis of the thermo-hydro-elastodynamic model proposed by the authors. The formulation is applied to the generalized porous thermoviscoelasticity theories: coupling theory, Lord–Shulman theory and Green–Lindsay theory. The general characteristic equations for arbitrary coordinate system are derived using a semi-analytical approach in the Laplace domain. Exact solutions of the saturated porous thermoviscoelastic media, with a cylindrical cavity that is subjected to a time dependent thermal load, are obtained in the absence of heat sources. Numerical results are illustrated graphically employing numerical method for inverting the Laplace transform. Comparisons are made with the results predicted by these theories and the classical theory. In addition, the influence of rheological parameters on the thermoviscoelastic property is analyzed.

Influence of rheological parameters in all drag reduction regimes of turbulent channel flow with polymer additives

The influence of rheological parameters on vortex dynamics and the extent of drag reduction (DR) were deciphered via extensively analyzing the hi-fidelity direct numerical simulation results of the turbulent channel flow with polymer solutions. It has been observed that in all drag reduction regimes from the onset of DR to maximum drag reduction (MDR) limit, the Deborah number is defined as the product of an effective Weissenberg number, and the root mean square streamwise vorticity fluctuation remains O(1) in the near wall region. The ratio of the average lifetime of axial vortices to the vortex rotating duration decreases with increasing DR, and MDR is achieved when these time scales become nearly equal. Based on these observations a simple framework is proposed adequately to describe the influence of polymer additives on the extent of DR from onset to MDR as well as the universality of the MDR in flow systems with polymer additives.

Searching for models of thermo-chemical convection that explain probabilistic tomography: I. Principles and influence of rheological parameters

Recent seismological observations indicate that strong lateral density anomalies, likely due to compositional anomalies, are present in the deep mantle. We aim to identify models of thermo-chemical convection that can generate strong thermo-chemical density anomalies. For this, we explore the model space of thermo-chemical convection, determine the thermal and chemical density distributions predicted by these models, and compare their power spectra against those from probabilistic tomography. We conduct 3D-Cartesian numerical experiments using STAG3D, in which we prescribed an initial layer of dense material at the bottom of the system. We focus on the parameters of the viscosity law, including the compositional (R μ c), 660 km (R μ 660), depth (R μ z ), and thermal (R μ T ) viscosity contrasts, and report strong differences in the pattern of thermo-chemical convection depending on the values of these ratios. For small (≤0.1) values of R μ c dense and regular materials quickly mix, whereas for large (≥10 2) values of R μ c the layer of dense material remains stable. Only moderate (0.1–10) R μ c predict patterns that can maintain chemical density anomalies that fit seismic observations over long periods of time. A large (≥10 2) R μ 660 acts as a filter for dense material, maintaining strong lateral chemical density anomalies in the lower mantle, but the power spectra of these distributions do not fit seismic tomography in the long term. A large (≥10 4) R μ T maintains strong density anomalies everywhere in the lower mantle, including pools of dense material at the bottom of mantle, which fits seismic tomography well. A successful model of thermo-chemical convection (in the sense that it fits seismological observations well) might thus include a moderate (0.1–10) compositional density contrast and/or a strong (≥10 4) thermal viscosity contrast. The influence of other important parameters, including the buoyancy ratio, the Clapeyron slope at d = 660 km and the fraction of dense material, are explored in a companion paper.

Local near-surface buckling of a system consisting of an elastic (viscoelastic) substrate, a viscoelastic (elastic) bond layer, and an elastic (viscoelastic) covering layer

Within the framework of a piecewise homogenous body model and with the use of a three-dimensional linearized theory of stability (TLTS), the local near-surface buckling of a material system consisting of a viscoelastic (elastic) half-plane, an elastic (viscoelastic) bond layer, and a viscoelastic (elastic) covering layer is investigated. A plane-strain state is considered, and it is assumed that the near-surface buckling instability is caused by the evolution of a local initial curving (imperfection) of the elastic layer with time or with an external compressive force at fixed instants of time. The equations of TLTS are obtained from the three-dimensional geometrically nonlinear equations of the theory of viscoelasticity by using the boundary-form perturbation technique. A method for solving the problems considered by employing the Laplace and Fourier transformations is developed. It is supposed that the aforementioned elastic layer has an insignificant initial local imperfection, and the stability is lost if this imperfection starts to grow infinitely. Numerical results on the critical compressive force and the critical time are presented. The influence of rheological parameters of the viscoelastic materials on the critical time is investigated. The viscoelasticity of the materials is described by the Rabotnov fractional-exponential operator.

Local buckling around an interfacial crack in a viscoelastic sandwich plate

Buckling around an interfacial crack in a clamped sandwich plate is studied. The layers of the plate are assumed to be linearly viscoelastic, isotropic, and homogeneous. The investigations are carried out within the framework of a piecewise homogeneous body model with the use of a three-dimensional linearized theory of stability. The corresponding boundary value problems are solved numerically by employing the FEM and the Laplace transform. The calculated critical times are presented for various problem parameters. In this case, the upper and lower layers are assumed to be viscoelastic and are described by Rabotnov operators, whereas the midlayer is regarded as purely elastic. The influence of rheological parameters on the critical time is also analyzed.