NON-ISOTHERMAL EFFECTS IN PARTIALLY FILLED RUBBER MIXING SIMULATIONS OF MANUFACTURING PROCESSES

2019 ◽  
Vol 92 (1) ◽  
pp. 152-167 ◽  
Author(s):  
Hari Poudyal ◽  
Suma R. Das ◽  
Abhilash J. Chandy
Keyword(s):  
Heat Generation ◽  
Transient Flow ◽  
Fluid Dynamic ◽  
Flow Behavior ◽  
Maximum Shear Stress ◽  
Isothermal Flow ◽  
Cumulative Distribution ◽  
Multiphase Model ◽  
Significant Difference ◽  
Distribution Index

ABSTRACT A finite volume technique is used to analyze the isothermal and non-isothermal flow behavior for the rubber mixing process in a two-dimensional, partially filled (75%) internal mixer, which consists of two counterrotating rotors rotating at 20 rpm. In order to capture the interface between air and rubber, an Eulerian multiphase model called volume of fluid (VOF) has been employed here. The transient flow behavior was accomplished by a sliding mesh technique, and the highly viscous, non-Newtonian properties of the rubber have been characterized using the Bird–Carreau model. Most of the previous computational fluid dynamic (CFD)-based investigations of rubber mixing assumed isothermal flow, and consequently negligible viscous heat generation, temperature rise, and viscosity drop associated with heat generation. Hence, a non-isothermal simulation is carried out, and results are compared with those of an equivalent isothermal simulation. In addition, dispersive and distributive mixing characteristics are assessed using statistics calculated from particle tracks generated by a set of massless and neutral particles that have been injected in the simulation. For this purpose, quantities such as the cumulative distribution of maximum shear stress, length of stretch, and cluster distribution index are calculated and compared between isothermal and non-isothermal conditions. Results showed a significant difference between the isothermal and non-isothermal simulations, thus making the isothermal assumption critical. Also, the non-isothermal simulation predicted better mixing during the entire mixing cycle.

A Multiphase Flow Simulation for a Cells-on-a-Chip Device

2016 ◽  
Author(s):  
Meihua Zhang ◽  
Amy Zheng ◽  
Z. Charlie Zheng ◽  
Zhuo Michael Wang
Keyword(s):  
Fluid Dynamic ◽  
Flow Behavior ◽  
Flow Simulation ◽  
Multiphase Model ◽  
Flow Shear ◽  
Controlled System ◽  
Culture Cells ◽  
Medium Flow ◽  
Chip Geometry

Microfluidics-based microscale cell culture (cells-on-a-chip) provides a well-controlled system with physiological realistic parameters that emulates the organ-to-organ network of the human body. In the microenvironment, the in vivo situation can be resembled closely by controlling the chip geometry, medium flow behavior, medium-to-cell ratio, and other fluid dynamic parameters. This study is to develop a multiphase model to simulate the flow in such a device. The cell deposition rate influenced by the flow shear is discussed. The physics of fluid dynamics for each of the above mentioned parameters is investigated.

ASSESSMENT OF THE EFFECT OF SPEED RATIOS IN NUMERICAL SIMULATIONS OF HIGHLY VISCOUS RUBBER MIXING IN A PARTIALLY FILLED CHAMBER

2016 ◽  
Vol 89 (3) ◽  
pp. 371-391 ◽  
Author(s):  
Suma R. Das ◽  
Pashupati Dhakal ◽  
Hari Poudyal ◽  
Abhilash J. Chandy
Keyword(s):  
Maximum Shear Stress ◽  
Three Dimensional ◽  
Joint Probability ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Distribution Functions ◽  
Cumulative Distribution ◽  
Speed Ratio ◽  
Multiphase Model ◽  
Axial Distribution

ABSTRACT Three-dimensional, transient, isothermal, and incompressible computational fluid dynamics (CFD) simulations are carried out for rubber mixing with two counter-rotating rotors in a partially filled chamber in order to assess the effect of different speed ratios. The three different speed ratios that are investigated include 1.0, 1.125, and 1.5. In addition to the solution of the incompressible continuity and momentum equations, a Eulerian multiphase model is employed to simulate two phases, rubber and air, and the volume of fluid (VOF) technique is used to calculate the free surface flow between the phases. The Bird–Carreau model is used to characterize the non-Newtonian highly viscous rubber. Massless particles are injected in the simulations to obtain data required for statistical calculations related to dispersive and distributive mixing characteristics. Specifically, joint probability density functions of mixing index and shear rate, and cumulative distribution functions of maximum shear stress are calculated to assess dispersive mixing, while distributive mixing capabilities are evaluated using various quantities such as cluster distribution index, axial distribution, interchamber particle transfer, and segregation scale. Results showed the speed ratio 1.125 to be consistently superior to 1.5 and 1.0, in terms of both dispersive and distributive mixing performance. The large speed difference between the rotors in the case of 1.5 caused it to perform the worst.

TWO-DIMENSIONAL NONISOTHERMAL NUMERICAL ANALYSIS OF SPEED RATIO EFFECTS ON DISPERSION AND DISTRIBUTION IN HIGH-VISCOSITY PARTIALLY FILLED RUBBER MIXING

2019 ◽  
Vol 92 (1) ◽  
pp. 168-185
Author(s):  
Istiaque Ahmed ◽  
Hari Poudyal ◽  
Abhilash J. Chandy
Keyword(s):  
Heat Generation ◽  
Maximum Shear Stress ◽  
High Viscosity ◽  
Speed Ratio ◽  
Multiphase Model ◽  
Two Dimensional ◽  
Mixing Process ◽  
Rate Dependent ◽  
Arrhenius Function ◽  
Dynamics Simulations

ABSTRACT Two-dimensional, transient, and nonisothermal computational fluid dynamics simulations are conducted for high-viscosity rubber mixing in a two-wing rotor-equipped partially filled chamber of fill factor 75%. Calculations presented assess the effect of three differential speeds or speed ratios of the two rotors for the rubber mixing process: 1.0 (also called even speed), 1.125, and 1.5. A Eulerian multiphase model, the volume of fluid technique, is employed to simulate two different phases, rubber and air, by calculating the free surface between the two phases, in addition to the main governing equations such as the continuity, momentum, and energy equations. To characterize the non-Newtonian, highly viscous rubber under nonisothermal conditions, the shear rate–dependent Carreau-Yasuda model along with an Arrhenius function are employed. A set of massless particles is introduced into the chamber to calculate several parameters related to dispersive and distributive mixing characteristics. Specifically, the mixing index and maximum shear stress are analyzed for the dispersive nature, whereas cluster distribution index and length of stretch are calculated for investigating the distributive nature of the mixing process. Also, the temporal viscous heat generation rate, a good indication of the temperature rise throughout the domain, which is critical in the process and equipment design, is analyzed here. Results showed that the 1.125 speed ratio was the most efficient in terms of distributive mixing and heat generation.

New benchmark solutions for transient natural convection in partially porous annuli

2016 ◽  
Vol 26 (3/4) ◽  
pp. 1187-1225 ◽  
Author(s):  
Nicola Massarotti ◽  
Michela Ciccolella ◽  
Gino Cortellessa ◽  
Alessandro Mauro
Keyword(s):  
Natural Convection ◽  
Free Convection ◽  
Transient Flow ◽  
Flow Behavior ◽  
Outer Radius ◽  
Temperature Fields ◽  
Content Type ◽  
Transient Natural Convection ◽  
Velocity And Temperature Fields ◽  
Benchmark Solutions

Purpose – The purpose of this paper is to focus on the numerical analysis of transient free convection heat transfer in partially porous cylindrical domains. The authors analyze the dependence of velocity and temperature fields on the geometry, by analyzing transient flow behavior for different values of cavity aspect ratio and radii ratio; both inner and outer radius are assumed variable in order to not change the difference ro-ri. Moreover, several Darcy numbers have been considered. Design/methodology/approach – A dual time-stepping procedure based on the transient artificial compressibility version of the characteristic-based split algorithm has been adopted in order to solve the transient equations of the generalized model for heat and fluid flow through porous media. The present model has been validated against experimental data available in the scientific literature for two different problems, steady-state free convection in a porous annulus and transient natural convection in a porous cylinder, showing an excellent agreement. Findings – For vertically divided half porous cavities, with Rayleigh numbers equal to 3.4×106 for the 4:1 cavity and 3.4×105 for the 8:1 cavity, the numerical results show that transient oscillations tend to disappear in presence of cylindrical geometry, differently from what happens for rectangular one. The magnitude of this phenomenon increases with radii ratio; the porous layer also affects the stability of velocity and temperature fields, as oscillations tend to decrease in presence of a porous matrix with lower value of the Darcy number. Research limitations/implications – A proper analysis of partially porous annular cavities is fundamental for the correct estimation of Nusselt numbers, as the formulas provided for rectangular domains are not able to describe these problems. Practical implications – The proposed model represents a useful tool for the study of transient natural convection problems in porous and partially porous cylindrical and annular cavities, typical of many engineering applications. Moreover, a fully explicit scheme reduces the computational costs and ensures flexibility. Originality/value – This is the first time that a fully explicit finite element scheme is employed for the solution of transient natural convection in partially porous tall annular cavities.

scholarly journals Squeezing Force of the Magnetorheological Fluid Isolating Damper for Centrifugal Fan in Nuclear Power Plant

2012 ◽  
Vol 2012 ◽  
pp. 1-6 ◽  
Author(s):  
Jin Huang ◽  
Ping Wang ◽  
Guochao Wang
Keyword(s):  
Nuclear Power ◽  
Theoretical Foundation ◽  
Fluid Dynamic ◽  
Flow Behavior ◽  
Magnetorheological Fluid ◽  
Centrifugal Fan ◽  
Parallel Channel ◽  
Mr Fluid ◽  
Mr Fluids ◽  
Control Devices

Magnetorheological (MR) disk-type isolating dampers are the semi-active control devices that use MR fluids to produce controllable squeezing force. In this paper, the analytical endeavor into the fluid dynamic modeling of an MR isolating damper is reported. The velocity and pressure distribution of an MR fluid operating in an axisymmetric squeeze model are analytically solved using a biviscosity constitutive model. Analytical solutions for the flow behavior of MR fluid flowing through the parallel channel are obtained. The equation for the squeezing force is derived to provide the theoretical foundation for the design of the isolating damper. The result shows that with the increase of the applied magnetic field strength, the squeezing force is increased.

scholarly journals FLOW BEHAVIOUR OF OIL BLOB THROUGH A CAPILLARY TUBE CONSTRICTION DURING PULSED INJECTION

2018 ◽  
Vol 81 (1) ◽  
Author(s):  
Shiferaw Regassa Jufar ◽  
Tareq M Al-Shami ◽  
Ulugbek Djuraev ◽  
Berihun Mamo Negash ◽  
Mohammed Mahbubur Rahman
Keyword(s):  
Pressure Gradient ◽  
Transient Flow ◽  
Capillary Tube ◽  
Reverse Flow ◽  
Flow Behavior ◽  
Adverse Pressure Gradient ◽  
Gradient Zone ◽  
Pulsed Injection ◽  
Time Required ◽  
Continuous Injection

A numerical simulation of flow of oil blob through a capillary tube constriction is presented. The simulation was run in a 2D axisymmetric model. Water is injected at the inlet to mobilize oil blob placed near the capillary tube constriction. Transient flow images were used to understand the flow evolution process. Results from the study show that pulsed injection effectively assisted to squeeze out the oil blob through the capillary tube constriction with shorter time compared to continuous injection.  Pulsed injection reduced the time required for the first droplet to cross the capillary tube constriction by about 3 folds compared to continuous injection. In addition, the droplet that crossed the constriction is larger when the flow was pulsed. In both cases, there is a reverse flow in the opposite direction of the injection. However, the severity of the reverse flow is stronger in the case of continuous injection. Immediately downstream the constriction, there is an adverse pressure gradient zone during continuous injection which limits the mobility of droplet that crossed the constriction. However, in the case of pulsed injection, there is a favorable pressure gradient zone immediately downstream the constriction. This zone expedites mobility of droplets that cross the constriction by transporting them further downstream through suction effect. Apparently, pulsed injection eases off the adverse pressure gradient and allowed more volume of oil to pass through the constriction. Within about two periods of pulsation, 84% of original oil placed at the beginning crossed the constriction compared to only 35% in the case of continuous injection. Even though the same amount of water was injected in both cases, pulsed injection clearly altered the flow behavior. The observation from this study may be extended to more complex flows in order to tailor the method for certain specific applications, such as flow of residual oil through a reservoir.

scholarly journals Analysis of Flow Behavior for Acid Fracturing Wells in Fractured-Vuggy Carbonate Reservoirs

2018 ◽  
Vol 2018 ◽  
pp. 1-20 ◽  
Author(s):  
Mingxian Wang ◽  
Zifei Fan ◽  
Xuyang Dong ◽  
Heng Song ◽  
Wenqi Zhao ◽  
...  
Keyword(s):  
Composite System ◽  
Numerical Solutions ◽  
Transient Flow ◽  
Flow Behavior ◽  
Outer Region ◽  
Carbonate Reservoirs ◽  
Single Fracture ◽  
Specific Flow ◽  
Type Curves ◽  
Acid Fracturing

This study develops a mathematical model for transient flow analysis of acid fracturing wells in fractured-vuggy carbonate reservoirs. This model considers a composite system with the inner region containing finite number of artificial fractures and wormholes and the outer region showing a triple-porosity medium. Both analytical and numerical solutions are derived in this work, and the comparison between two solutions verifies the model accurately. Flow behavior is analyzed thoroughly by examining the standard log-log type curves. Flow in this composite system can be divided into six or eight main flow regimes comprehensively. Three or two characteristic V-shaped segments can be observed on pressure derivative curves. Each V-shaped segment corresponds to a specific flow regime. One or two of the V-shaped segments may be absent in particular cases. Effects of interregional diffusivity ratio and interregional conductivity ratio on transient responses are strong in the early-flow period. The shape and position of type curves are also influenced by interporosity coefficients, storativity ratios, and reservoir radius significantly. Finally, we show the differences between our model and the similar model with single fracture or without acid fracturing and further investigate the pseudo-skin factor caused by acid fracturing.

Simulation of Spouted Bed Using a Eulerian Multiphase Model

2005 ◽  
Vol 498-499 ◽  
pp. 270-277 ◽  
Author(s):  
Claudio Roberto Duarte ◽  
Valéria V. Murata ◽  
Marcos A.S. Barrozo
Keyword(s):  
Control Volume ◽  
Flow Behavior ◽  
Cfd Modeling ◽  
Gas Flows ◽  
Present Calculation ◽  
Multiphase Model ◽  
Spouted Bed ◽  
Particle Coating ◽  
Spouted Beds ◽  
Good Agreement

Spouted bed systems have emerged as very efficient fluid-particle contactors and find many applications in the chemical and biochemical industry. Some important applications of spouted beds include coal combustion, biochemical reactions, drying of solids, drying of solutions and suspensions, granulation, blending, grinding, and particle coating. An extensive overview can be found in Mathur and Epstein[1]. The pattern of solid and gas flows in a spouted bed was numerically simulated using a CFD modeling technique. The Eulerian-Eulerian multifluid modeling approach was applied to predict gas-solid flow behavior. A commercially available, control-volume-based code FLUENT 6.1 was chosen to carry out the computer simulations. In order to reduce computational times and required system resources, the 2D axisymmetric segregated solver was chosen. The typical flow pattern of the spouted bed was obtained in the present calculation. The simulated velocity and voidage profiles presented a good agreement qualitative and quantitative with the experimental results obtained by He et al. [4].

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