Rheological studies of functional polyurethane composite

2017 ◽  
Vol 50 (3) ◽  
pp. 222-240
Author(s):  
Sayavur I Bakhtiyarov ◽  
Jimmie C Oxley ◽  
James L Smith ◽  
Philipp M Baldovi
Keyword(s):  
Newtonian Fluid ◽  
Power Law ◽  
Effective Viscosity ◽  
Aluminum Content ◽  
Fluid Model ◽  
Shear Thinning ◽  
Testing Time ◽  
Two Phase ◽  
Bingham Plastic ◽  
Polyurethane Composite

The rheological dynamic characteristics of the functional Polyurethane composite as well as its compounds ( triethanolamine (TEOA) and toluene-2,4-diisocyanate (TDI)) with and without solid additives (aluminum flakes) were experimentally measured using a computer-controlled mechanical spectrometer (rheometer) ARES-G2. Rheological studies showed that both components behave as viscous Newtonian fluids. TEOA exhibits a strong temperature-thickening behavior. TEOA with aluminum flake additives behaves as a viscous Newtonian fluid. The effective viscosity of the two-phase mixture increases with the concentration of the aluminum additive and decreases with the temperature rise. The rheometric tests showed that the effective viscosity of the TDI/Al mixture increases with the aluminum content. The mixture exhibits thermal-thickening and shear-thinning behaviors with the yield stress. The system can be described with the Bingham plastic model. It is determined that TEOA/TDI composite exhibits a strong time-thickening and shear-thinning behaviors. The rheological behavior of this composite can be described with the power-law generalized non-Newtonian fluid model. The effective viscosity of TEOA/TDI/Al composite increases with both the testing time (exponentially) and the aluminum content (polynomial) in the mixture. However, these shear-thinning composites obey the power-law generalized non-Newtonian fluid model, and their flow curves can be described by the logarithmic law.

Rheometric Studies of Functional Polyurethane Foam Composite

2017 ◽  
Author(s):  
Sayavur I. Bakhtiyarov ◽  
Jimmie C. Oxley ◽  
James L. Smith ◽  
Philipp M. Baldovi ◽  
Dennis A. Siginer
Keyword(s):  
Newtonian Fluid ◽  
Power Law ◽  
Fluid Model ◽  
Shear Thinning ◽  
Solid Content ◽  
Testing Time ◽  
Pu Foam ◽  
Foam Composite ◽  
Computer Controlled

A rheometric characterization of the functional Polyurethane (PU) foam composite with and without solid additives (aluminum flakes) were experimentally measured using a computer controlled mechanical spectrometer (rheometer) ARES-G2. It is determined that PU composite exhibits a strong time thickening and shear thinning behavior. The rheological behavior of this composite can be described with the power-law generalized non-Newtonian fluid model. The rheometric tests showed that the PU/Al mixture exhibits thermal thickening and shear thinning behavior with the yield stress. The system can be described with the power-law generalized non-Newtonian fluid (Ostwald-de-Waele) model. The effective viscosity of PU composite increases with both the testing time (exponentially) and the solid content (polynomial) in the mixture.

Rheological studies of functional polyurethane composite with solid additives

2017 ◽  
Vol 50 (4) ◽  
pp. 312-324
Author(s):  
Jimmie C Oxley ◽  
James L Smith ◽  
Sayavur I Bakhtiyarov ◽  
Philipp M Baldovi
Keyword(s):  
Apparent Viscosity ◽  
Fluid Model ◽  
Experimental Tests ◽  
Solid Content ◽  
Testing Time ◽  
Two Phase ◽  
Rheological Measurements ◽  
Polyurethane Composite ◽  
Foam Composite ◽  
Phase Mixture

The rheological dynamic characteristics of the functional polyurethane foam composite with solid additives (calcium iodate particles, aluminum flakes) were experimentally measured using an oscillatory rotational rheometer ARES-G2. Our previous studies demonstrated that the presence of the gas bubbles alters the rheology of the continuous liquid phase. The experimental tests results show that the apparent viscosity (the shear stress applied to a fluid divided by the shear rate) of the two-phase mixture increases with the concentration of the aluminum additive and decreases with the temperature rise. The rheological measurements showed that the functional foam exhibits a strong time-dependent and thixotropic (shear thinning) behavior. The rheological behavior of this composite can be described with the power law–generalized non-Newtonian fluid model. The apparent viscosity of the polyurethane increases with both the testing time (exponentially) and the solid content (polynomial) in the mixture. The measured rheological characteristics of the polyurethane-based functional foam will be helpful for material designers and developers.

Study of Blood Flow in Micro-Channels Using Mixture Theory

2014 ◽  
Author(s):  
Wei-Tao Wu ◽  
Nadine Aubry ◽  
James F. Antaki ◽  
Mehrdad Massoudi
Keyword(s):  
Blood Flow ◽  
Newtonian Fluid ◽  
Mixture Theory ◽  
Shear Thinning ◽  
Characteristic Size ◽  
Navier Stokes ◽  
Two Phase ◽  
Plasma Skimming ◽  
Micro Channels ◽  
Complex Phenomena

It is known that in large vessels (whole) blood behaves as a Navier-Stokes (Newtonian) fluid; however, in a vessel whose characteristic dimension (e.g., a diameter in the range of 20 to 500 microns) is about the same size as the characteristic size of the blood cells, blood behaves as a non-Newtonian fluid, exhibiting complex phenomena, such as shear-thinning, stress relaxation, the Fahraeus effect, the plasma-skimming, etc.. Using the framework of mixture theory an Eulerian-Eulerian two phase model is applied to model blood flow, where the plasma is treated as Newtonian fluid and the RBCs are treated as shear thinning fluid.[5]

Experimental Investigation of Flow-Induced Vibration in Gas/Shear-Thinning Liquid Flows in Vertical Pipe

2020 ◽  
Author(s):  
Ruinan Lin ◽  
Ke Wang ◽  
Qing Li ◽  
Narakorn Srinil ◽  
Fangjun Shi
Keyword(s):  
Newtonian Fluid ◽  
Industrial Process ◽  
Flow Region ◽  
Shear Thinning ◽  
Maximum Energy ◽  
Internal Diameter ◽  
Flow Induced Vibration ◽  
Two Phase ◽  
Liquid Flows ◽  
Shear Thinning Fluid

Abstract The non-Newtonian shear-thinning fluid widely exists in the industrial process and the rheology exerts a significant influence on the flow pattern transition and flow-induced vibration (FIV). However, studies on the rheology effect of the liquid phase in the vertical upward two-phase flows are quite lacking due to the complexity of non-Newtonian fluid properties. In the present study, the vertical upward gas/shear-thinning liquid flows experiments are conducted on a rigid acrylic pipe with an internal diameter of 20 mm. Three different Carboxymethyl Cellulose (CMC) solutions are used as the non-Newtonian fluid, aimed at capturing a two-phase flow regime transition including the vertical slug, churn and annular flows. The results indicate that the maximum energy spectral densities of vibration occur at the slug-to-churn flow transition boundary at low liquid velocities and the annular flow region under high liquid velocities, respectively. The effects of the rheology of the shear-thinning fluid in terms of the flow patterns and FIV are also presented and discussed.

A Rational Friction Factor Correlation for Laminar Fully-Developed Pipe Flows of Shear-Thinning Non-Newtonian Fluids

2021 ◽  
Author(s):  
Robert Brewster
Keyword(s):  
Shear Rate ◽  
Friction Factor ◽  
Power Law ◽  
Fluid Model ◽  
Shear Thinning ◽  
Newtonian Fluids ◽  
Cross Model ◽  
Pipe Flows ◽  
Design Calculations ◽  
Friction Factor Correlation

Abstract A friction factor correlation for laminar, hydrodynamically fully-developed pipe flows of shear-thinning non-Newtonian fluids is derived through analysis and asymptotic considerations. The specific non-Newtonian fluid model used is the Extended Modified Power Law (EMPL) model, which is functionally equivalent to the Cross model. The EMPL model spans the entire shear rate range from the low to the high shear rate Newtonian regions, and includes the intermediate shear rate power law region. The friction factor correlation has an explicit form and is a function of three dimensionless parameters, making it well-suited to design calculations. The overall accuracy of the correlation is 6.6%, though it is much better in most cases. Graphical results for the correlation, and deviations with respect to high-accuracy numerical calculations are presented and discussed.

scholarly journals Collapse of a neutrally buoyant suspension column: from Newtonian to apparent non-Newtonian flow regimes

2017 ◽  
Vol 826 ◽  
pp. 918-941 ◽  
Author(s):  
A. Bougouin ◽  
L. Lacaze ◽  
T. Bonometti
Keyword(s):  
Power Law ◽  
Temporal Evolution ◽  
Volume Fraction ◽  
Fluid Model ◽  
Particle Diameter ◽  
Shear Thickening ◽  
Shear Thinning ◽  
Rheological Parameters ◽  
Power Law Fluids ◽  
Neutrally Buoyant

Experiments on the collapse of non-colloidal and neutrally buoyant particles suspended in a Newtonian fluid column are presented, in which the initial volume fraction of the suspension $\unicode[STIX]{x1D719}$, the viscosity of the interstitial fluid $\unicode[STIX]{x1D707}_{f}$, the diameter of the particles $d$ and the mixing protocol, i.e. the initial preparation of the suspension, are varied. The temporal evolution of the slumping current highlights two main regimes: (i) an inertial-dominated regime followed by (ii) a viscous-dominated regime. The inertial regime is characterized by a constant-speed slumping which is shown to scale as in the case of a classical inertial dam-break. The viscous-dominated regime is observed as a decreasing-speed phase of the front evolution. Lubrication models for Newtonian and power-law fluids describe most of situations encountered in this regime, which strongly depends on the suspension parameters. The temporal evolution of the propagating front is used to extract the rheological parameters of the fluid models. At the early stages of the viscous-dominated regime, a constant effective shear viscosity, referred to as an apparent Newtonian viscous regime, is found to depend only on $\unicode[STIX]{x1D719}$ and $\unicode[STIX]{x1D707}_{f}$ for each mixing protocol. The obtained values are shown to be well fitted by the Krieger–Dougherty model whose parameters involved, say a critical volume fraction $\unicode[STIX]{x1D719}_{m}$ and the exponent of divergence, depend on the mixing protocol, i.e. the microscale interaction between particles. On a longer time scale which depends on $\unicode[STIX]{x1D719}$, the front evolution is shown to slightly deviate from the apparent Newtonian model. In this apparent non-Newtonian viscous regime, the power-law model, indicating both shear-thinning and shear-thickening behaviours, is shown to be more appropriate to describe the front evolution. The present experiments indicate that the mixing protocol plays a crucial role in the selection of a shear-thinning or shear-thickening type of collapse, while the particle diameter $d$ and volume fraction $\unicode[STIX]{x1D719}$ play a significant role in the shear-thickening case. In all cases, the normalized effective consistency of the power-law fluid model is found to be a unique function of $\unicode[STIX]{x1D719}$. Finally, an apparent viscoplastic regime, characterized by a finite length spreading reached at finite time, is observed at high $\unicode[STIX]{x1D719}$. This regime is mostly observed for volume fractions larger than $\unicode[STIX]{x1D719}_{m}$ and up to a volume fraction $\unicode[STIX]{x1D719}_{M}$ close to the random close packing fraction at which the initial column remains undeformed on opening the gate.

Computational Modeling of Enhanced Laminar Flow Heat Transfer in Viscoplastic Fluids in Corrugated-Plate Channels

2002 ◽  
Author(s):  
Hossam M. Metwally ◽  
Raj M. Manglik
Keyword(s):  
Heat Transfer ◽  
Yield Stress ◽  
Power Law ◽  
Flow Behavior ◽  
Shear Thinning ◽  
Bingham Plastic ◽  
Wide Range ◽  
Order Of Magnitude ◽  
Colburn Factor ◽  
Power Law Index

The enhanced heat transfer in laminar viscoplastic, shear thinning, Herschel-Bulkley fluid flows in sinusoidal corrugated-plate channels is investigated. With uniform-temperature plate walls, periodically developed flows are considered for a wide range of flow rates (10 ≤ Reg ≤ 700) and pseudoplastic flow behavior indices (n = 0.54, 0.8, and 1.0; the latter representing a Bingham plastic). The effects of fluid yield stress are simulated for the case where τy = 1.59 N/m2, representing a 0.5% xantham gum aqueous solution. Typical velocity and temperature distributions, along with extended results for isothermal friction factor ƒ and Colburn factor j are presented. The effect of the yield stress is found to be most dominant at low Reg regardless of the power law index n, and the recirculation or swirl in the wall trough regions is weaker than in the cases of Newtonian and power-law liquids. At higher Reg, the performance of the Herschel-Bulkley fluid asymptotically approaches that of the non-yield-stress power-law fluid. At low Reg, the yield stress increases ƒ by an order of magnitude and j is enhanced because of the higher wall gradients imposed by the plug-like flow field. The relative heat transfer enhancement, represented by the ratio (j/ƒ), and the role of the fluid yield stress and shear-thinning (or pseudoplastic) behaviors are also discussed.

Mathematical model for a Herschel-Bulkley fluid flow in an elastic tube

Open Physics ◽  
2011 ◽  
Vol 9 (5) ◽  
Author(s):  
Kuppalapalle Vajravelu ◽  
Sreedharamalle Sreenadh ◽  
Palluru Devaki ◽  
Kerehalli Prasad
Keyword(s):  
Shear Stress ◽  
Fluid Flow ◽  
Wall Shear Stress ◽  
Yield Stress ◽  
Newtonian Fluid ◽  
Power Law ◽  
Fluid Model ◽  
Elastic Tube ◽  
Yield Stress Fluid ◽  
Power Law Index

AbstractThe constitution of blood demands a yield stress fluid model, and among the available yield stress fluid models for blood flow, the Herschel-Bulkley model is preferred (because Bingham, Power-law and Newtonian models are its special cases). The Herschel-Bulkley fluid model has two parameters, namely the yield stress and the power law index. The expressions for velocity, plug flow velocity, wall shear stress, and the flux flow rate are derived. The flux is determined as a function of inlet, outlet and external pressures, yield stress, and the elastic property of the tube. Further when the power-law index n = 1 and the yield stress τ 0 → 0, our results agree well with those of Rubinow and Keller [J. Theor. Biol. 35, 299 (1972)]. Furthermore, it is observed that, the yield stress and the elastic parameters (t 1 and t 2) have strong effects on the flux of the non-Newtonian fluid flow in the elastic tube. The results obtained for the flow characteristics reveal many interesting behaviors that warrant further study on the non-Newtonian fluid flow phenomena, especially the shear-thinning phenomena. Shear thinning reduces the wall shear stress.

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