scholarly journals Numerical Computation of MHD Thermal Flow of Cross Model over an Elliptic Cylinder: Reduction of Forces via Thickness Ratio

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Afraz Hussain Majeed ◽  
Rashid Mahmood ◽  
Waqas Sarwar Abbasi ◽  
K. Usman
Keyword(s):  
Pressure Drop ◽  
Flow Behavior ◽  
Elliptic Cylinder ◽  
Accurate Solution ◽  
Thickness Ratio ◽  
Maximum Pressure ◽  
Dimensional System ◽  
Thermal Flow ◽  
Flow Behavior Index ◽  
Cross Model

The present work is concerned with a comprehensive analysis of hydrodynamic forces, under MHD and forced convection thermal flow over a heated cylinder in presence of insulated plates installed at walls. The magnetic field is imposed in the transverse direction of flow. The Galerkin finite element (GFE) scheme has been used to discretize the two-dimensional system of nonlinear partial different equations. The study is executed for the varying range of flow behavior index n from 0.4 to 1.6, Hartmann number Ha from 0 to 100, Reynolds number Re from 10 to 50, Grashof number Gr from 1 to 10, thickness ratio e from 0.5 to 1.0, and Prandtl number Pr from 1 to 10, respectively. A coarse hybrid computational grid is developed, and further refinement is carried out for obtaining the highly accurate solution. The optimum case selection is based on flow patterns, drag and lift coefficients, and pressure drop reduction against cylinder thickness ratios and average Nusselt numbers. Drag coefficient increases with an increase in thickness ratio e . The drag force reduction for e = 0.5 and e = 0.75 is also observed for a range of the power law index as compared with e = 1.0 cylinder. Maximum pressure drop over the back and front points of cylinder is reported at Ha = 100 .

Lubrication of a Cylinder on a Plane With a Non-Newtonian Fluid Considering Cavitation

1982 ◽  
Vol 104 (2) ◽  
pp. 168-172 ◽  
Author(s):  
Prawal Sinha ◽  
Chandan Singh
Keyword(s):  
Theoretical Analysis ◽  
Load Capacity ◽  
Flow Behavior ◽  
Rolling Contact ◽  
Maximum Pressure ◽  
Power Law Model ◽  
Flow Behavior Index ◽  
Joint Lubrication ◽  
Human Joint ◽  
Behavior Index

This paper presents a theoretical analysis of lubrication of rolling contact bearings considering cavitation with a non-Newtonian lubricant, obeying the power law model. Piezo-viscous and deformation effects are neglected. The analysis reveals, that as the flow behavior index increases, the load capacity increases and the point of cavitation as well as the point of maximum pressure is shifted towards the center of contact. It is also indicated that the present analysis may be considered as providing an approximation to human joint lubrication problem.

A Comparative Analysis of Mixing Performance of Power-Law Fluid in Cylindrical Microchannels With Sudden Contraction/Expansion

2020 ◽  
Vol 142 (6) ◽  
Author(s):  
A. Banerjee ◽  
A. K. Nayak ◽  
B. Weigand
Keyword(s):  
Pressure Drop ◽  
Power Law ◽  
Flow Behavior ◽  
Geometric Parameters ◽  
Mixing Efficiency ◽  
Flow Behavior Index ◽  
Mixing Performance ◽  
Geometric Configurations ◽  
Wide Range ◽  
Behavior Index

Abstract This paper focuses on the comparative electrokinetic micromixing of non-Newtonian fluid in cylindrical microchannels with surface potential heterogeneity due to sudden constriction/expansion. In numerical simulations, the rheology of the aqueous solution is considered to follow power-law characteristic. Based on the Poisson–Nernst–Planck model, the simulations are performed to investigate the mixing efficiency and pressure drop for constricted and expanded configurations over a wide range of the flow behavior index, potential patch strength, and geometric parameters. The results show that, irrespective of geometric configurations, the mixing efficiency can be improved significantly by increasing the flow behavior index, geometric parameters, and the overpotential patch strength. In addition, it is also revealed that the constricted geometry yields better mixing as compared to the other configuration, but the average pressure drop shows reverse characteristics. Thus, a parametric relationship is tried to be established between mixing efficiency and pressure drop for both these configurations to propose an effective and efficient micromixer, which can produce maximum possible mixing efficiency with minimum pressure drop.

Effects of Greek Pomegranate Extracts in the Antioxidant Properties and Storage Stability of Kefir

2019 ◽  
Vol 15 (4) ◽  
pp. 437-441 ◽  
Author(s):  
Vasiliki Lagouri ◽  
Georgia Dimitreli ◽  
Aikatarini Kouvatsi
Keyword(s):  
Antioxidant Activity ◽  
Dairy Products ◽  
Storage Time ◽  
Storage Stability ◽  
Flow Behavior ◽  
Antioxidant Properties ◽  
Flow Behavior Index ◽  
Ph Values ◽  
Dpph Activity ◽  
Behavior Index

Background: Oxidation reactions are known to shorten the shelf life and cause damage to foods rich in fat, such as dairy products. One way to limit oxidation and increase the shelf life of fermented dairy products is to use natural antioxidants. The aim of this study was to examine the effect of adding pomegranate extracts in the antioxidant properties, rheological characteristics and the storage stability of the fermented product of kefir. Methods: The Pomegranate Juice (PGJ) and Peel Extracts (PGPE) (5%, 10% w/v) were added to kefir and the antioxidant properties were evaluated by using the methods of radical scavenging activity (DPPH) and Ferric Reducing Antioxidant Power Activity (FRAP). Spectrophotometric and instrumental methods were used to determine the Total Phenols (TPs), pH values, viscosity and flow behavioral index values of enriched with pomegranate kefir samples. The same properties were tested when kefir samples stored at 4°C for 7, 14, 21 and 28 days. Results: The addition of PGJ and PGPE results in an increase in the antioxidant activity (DPPH, FRAP) and total phenol content (TPs) of kefir samples. Increasing the concentration of the added PGJ and PGPE, results in an increase in the TP content and the DPPH activity of kefir. As far as the storage time is concerned, the results showed an increase in the amount of TP at 7th day and a reduction in the DPPH activity in the 14th day of storage. In contrary to the DPPH method, the increase in storage time has resulted in a reduction in antioxidant activity by the FRAP method. The addition of PGJ and PGPE in kefir results in a decrease in pH values while the pH of kefir samples increased during storage at 4°C for 28 days. The addition of PGJ and PGPE to kefir samples results to a decrease in viscosity and an increase in the flow behavior index. Increasing storage time results in increased flow behavior index of kefir samples. Conclusion: The addition of PGJ and PGPE increased the antioxidant activity and total phenols of the kefir product and preserved its properties during the total storage time of 28 days at 4°C.

scholarly journals Research on the viscosity of stabilized emulsions in different pipe diameters using pressure drop and phase inversion

2021 ◽  
Author(s):  
Jose Plasencia ◽  
Nathanael Inkson ◽  
Ole Jørgen Nydal
Keyword(s):  
Pressure Drop ◽  
Salt Water ◽  
Flow Behavior ◽  
Turbulent Viscosity ◽  
Relative Viscosity ◽  
Cfd Modeling ◽  
Water Fraction ◽  
Water Fractions ◽  
Oil Emulsions ◽  
Mixture Velocity

AbstractThis paper reports experimental research on the flow behavior of oil-water surfactant stabilized emulsions in different pipe diameters along with theoretical and computational fluid dynamics (CFD) modeling of the relative viscosity and inversion properties. The pipe flow of emulsions was studied in turbulent and laminar conditions in four pipe diameters (16, 32, 60, and 90 mm) at different mixture velocities and increasing water fractions. Salt water (3.5% NaCl w/v, pH = 7.3) and a mineral oil premixed with a lipophilic surfactant (Exxsol D80 + 0.25% v/v of Span 80) were used as the test fluids. The formation of water-in-oil emulsions was observed from low water fractions up to the inversion point. After inversion, unstable water-in-oil in water multiple emulsions were observed under different flow regimes. These regimes depend on the mixture velocity and the local water fraction of the water-in-oil emulsion. The eddy turbulent viscosity calculated using an elliptic-blending k-ε model and the relative viscosity in combination act to explain the enhanced pressure drop observed in the experiments. The inversion process occurred at a constant water fraction (90%) and was triggered by an increase of mixture velocity. No drag reduction effect was detected for the water-in-oil emulsions obtained before inversion.

Effect of Surface State of Die on Flow Rate of Steamed Bamboo Powder in Thermal Flow Test Using Capillary Rheometer

2015 ◽  
Vol 651-653 ◽  
pp. 830-835
Author(s):  
Shohei Kajikawa ◽  
Riku Sakagami ◽  
Takashi Iizuka
Keyword(s):  
Particle Size ◽  
Flow Rate ◽  
Surface State ◽  
Flow Behavior ◽  
Thermal Flow ◽  
Average Roughness ◽  
Arithmetic Average ◽  
Flow Test ◽  
Die Surface ◽  
Bamboo Powder

Thermal flow tests were performed on steamed bamboo powder using capillaries that were processed under different conditions in order to investigate the effect of the die surface state on the fluidity of the woody powder. The capillaries were processed by wire-cut electric discharge machining, reaming or drilling, and the arithmetic average roughness (Ra) varied from 0.5 to 2.5 μm. The bamboo powder was first steamed at 200 °C for 20 min, and its particle size was then controlled using different mesh screens. The thermal flow temperature was set at 200 °C. The results indicated that the flow behavior improved with increasing particle size. For the capillaries processed by WEDM, the flow rate for samples with particle sizes of 75~150 and 150~300 μm decreased with increasing Ra. On the other hand, when reaming or drilling was used to process the capillaries, the flow rate was almost independent of Ra, regardless of the particle size.

Electroosmotic Flow of Power-Law Fluids in a Slit Microchannel

2009 ◽  
Author(s):  
Cunlu Zhao ◽  
Chun Yang
Keyword(s):  
Shear Stress ◽  
Double Layer ◽  
Power Law ◽  
Dynamic Viscosity ◽  
Electroosmotic Flow ◽  
Flow Behavior ◽  
Flow Behavior Index ◽  
Power Law Fluids ◽  
Hyperbolic Cosine ◽  
Behavior Index

Electroosmotic flow of power-law fluids in a slit channel is analyzed. The governing equations including the linearized Poisson–Boltzmann equation, the Cauchy momentum equation and the continuity equation are solved to seek analytical expressions for the shear stress, dynamic viscosity and velocity distributions. Specifically, exact solutions of the velocity distributions are explicitly found for several special values of the flow behavior index. Furthermore, with the implementation of an approximate scheme for the hyperbolic cosine function, approximate solutions of the velocity distributions are obtained. In addition, a mathematical expression for the average electroosmotic velocity is derived for large values of the dimensionless electrokinetic parameter, κH, in a fashion similar to the Smoluchowski equation. Hence, a generalized Smoluchowski velocity is introduced by taking into account contributions due to the finite thickness of the electric double layer and the flow behavior index of power-law fluids. Finally, calculations are performed to examine the effects of κH, flow behavior index, double layer thickness, and applied electric field on the shear stress, dynamic viscosity, velocity distribution, and average velocity/flow rate of the electroosmotic flow of power-law fluids.

Design and Simulation of a Hybrid Entrained-Flow and Fluidized Bed Mild Gasifier: Part 2—Case Study and Analysis

2011 ◽  
Author(s):  
A. K. M. Monayem Mazumder ◽  
Ting Wang ◽  
Jobaidur R. Khan
Keyword(s):  
Multiphase Flow ◽  
Fluidized Bed ◽  
Flow Behavior ◽  
Flame Temperature ◽  
Heterogeneous Reactions ◽  
Thermal Flow ◽  
Entrained Flow ◽  
Progressive Development ◽  
Gasification Process ◽  
Flow And Heat Transfer

To help design a mild-gasifier, a reactive multiphase flow computational model has been developed in Part 1 using Eulerian-Eulerian method to investigate the thermal-flow and gasification process inside a conceptual, hybrid entrained-flow and fluidized-bed mild-gasifier. In Part 2, the results of the verifications and the progressive development from simple conditions without particles and reactions to complicated conditions with full reactive multiphase flow are presented. Development of the model starts from simulating single-phase turbulent flow and heat transfer in order to understand the thermal-flow behavior, followed by introducing seven global, homogeneous gasification reactions progressively added one equation at a time. Finally, the particles are introduced, and heterogeneous reactions are added in a granular flow field. The mass-weighted, adiabatic flame temperature is validated through theoretical calculation and the minimum fluidization velocity is found to be close to Ergun’s correlation. Furthermore, the predicted exit species composition is consistent with the equilibrium values.

scholarly journals Computational and Experimental Study on Pressure Drop in a Fluidised Bed with Different Air Distributor Designs

2020 ◽  
Vol 17 (2) ◽  
pp. 8043-8051
Author(s):  
A. S. M. Yudin ◽  
A. N. Oumer ◽  
N. F. M. Roslan ◽  
M. A. Zulkarnain
Keyword(s):  
Pressure Drop ◽  
Perforated Plate ◽  
Area Ratio ◽  
Maximum Pressure ◽  
Fluidised Bed ◽  
Key Factor ◽  
Minimum Number ◽  
Maximum Pressure Drop ◽  
Free Area ◽  
Distributor Plate

Fluidised bed combustion (FBC) has been recognised as a suitable technology for converting a wide variety of fuels into energy. In a fluidised bed, the air is passed through a bed of granular solids resting on a distributor plate. Distributor plate plays an essential role as it determines the gas-solid movement and mixing pattern in a fluidised bed. It is believed that the effect of distributor configurations such as variation of free area ratio and air inclination angle through the distributor will affect the operational pressure drop of the fluidised bed. This paper presents an investigation on pressure drop in fluidised bed without the presence of inert materials using different air distributor designs; conventional perforated plate, multi-nozzles, and two newly proposed slotted distributors (45° and 90° inclined slotted distributors). A 3-dimensional Computational Fluid Dynamics (CFD) model is developed and compared with the experimental results. The flow model is based on the incompressible isothermal RNG k-epsilon turbulent model. In the present study, systematic grid-refinement is conducted to make sure that the simulation results are independent of the computational grid size. The non-dimensional wall distance,  is examined as a key factor to verify the grid independence by comparing results obtained at different grid resolutions. The multi-nozzles distributor yields higher distributor pressure drop with the averaged maximum value of 749 Pa followed by perforated, 45° and 90° inclined distributors where the maximum pressure drop recorded to be about one-fourth of the value of the multi-nozzles pressure drop. The maximum pressure drop was associated with the higher kinetic head of the inlet air due to the restricted and minimum number of distributor openings and low free area ratio. The results suggested that low-pressure drop operation in a fluidised bed can be achieved with the increase of open area ratio of the distributor.

scholarly journals Estimation of Rheological Properties of Ice Cream Unfrozen Liquid Phase by FT-NIR Spectroscopy

1970 ◽  
Vol 66 (2) ◽  
Author(s):  
Florina A. SILAGHI ◽  
Alessandro GIUNCHI ◽  
Angelo FABBRI ◽  
Luigi RAGNI
Keyword(s):  
Liquid Phase ◽  
Rheological Properties ◽  
Powder Mixture ◽  
Goodness Of Fit ◽  
Flow Behavior ◽  
Nir Spectroscopy ◽  
Ice Cream ◽  
Rheological Parameters ◽  
Good Prediction ◽  
Flow Behavior Index

The control of ice cream powder mixture production is carried out evaluating the ice cream liquid phase. The present study was conduced on ice cream and unfrozen liquid phase in order to indirectly evaluate the rheological properties by measuring the powder mixture. The calibration set was formed by samples with different percentage of thickeners, maintaining constant the concentration of the other remaining compounds. After the NIR acquisitions the powders were mixed with warm milk, blended and than settled in order to obtain the unfrozen liquid phase needed for the rheological measurements. For each recipe three batches were prepared. The flow curves were evaluated by using the Ostwald de Waele’s equation and the goodness of fit was evaluated by the R2, which was above 0.95. Predictive models of rheological parameters were set up by means of PLS regressions in order to predict the consistency coefficient (K) and the flow behavior index (n) from spectral acquisitions. High correlation of calibration was found for both parameters and NIR spectra obtaining R2 of 0.884 for K and 0.874 for n. The good prediction of the models encourages applying them to reduce significantly the time of the powder mixing control during production.

Air Flow Analysis in Square Duct Bend

2014 ◽  
Vol 695 ◽  
pp. 622-626 ◽  
Author(s):  
Mohamad Nor Musa ◽  
Mohd Nurul Hafiz Mukhtar
Keyword(s):  
Reynolds Number ◽  
Pressure Drop ◽  
Cross Section ◽  
Air Flow ◽  
Flow Analysis ◽  
Maximum Velocity ◽  
Maximum Pressure ◽  
Air Velocity ◽  
Square Duct ◽  
Inlet Velocity

This paper present new result for experimental analysis of air flow velocity and pressure distributions between two ducts bend: (1) 90° duct bend with a single turning vane having 0.03m radius and (2) 90° duct bend with double turning vane, in 0.06 × 0.06 m duct cross section. The experiment used five different Reynolds numbers chosen between the ranges 1 ×104 and 6×104. Each experiment has four point measurements: (1) point 1 and point 2 at cross section A-A and (2) point 3 and point 4 at cross section B-B. The first experimental study used single turning vane radius 0.03m with inlet air velocity from 2.5m/s to 12.2m/s. And for the second experiment that used square turning vane with 0.03m radius. In experiment 2, the inlet air velocity also start from 2.5m/s to 12.2m/s. From analysis results, the pressure drop in experiment 1 is higher than experiment 2. As example the maximum pressure drop at 7.5m/s inlet air velocity between point 1 and 3 was found to be 71.6203 Pa in experiment 1 as compared to 61.8093 Pa in experiment 2. The velocity after duct bend is greater when using double turning vane compare used single turning vane as maximum velocity at point 3 in experiment 2 compare to velocity at point 3 in experiment 1 that is 55.677× 10-4 m/s and 54.221× 10-4 m/s. The velocity at duct wall is equal to zero. When increase the value of Reynolds number or inlet velocity, the maximum velocity and total pressure also increase. For example in experiment 1 at point 1, the velocity is 48.785 × 10-4 m/s at Reynolds number 1 ×104 and velocity 65.115×10-4 m/s at Reynolds number 12.2 ×104 . Velocity flow in duct section are lower than inlet velocity. In experiment 1, the inlet velocity is 2.5m/s meanwhile the maximum velocity in the duct section at point 2 is 73.075×10-4 m/s that is much more lower than inlet velocity.

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