non-Newtonian Multiphase Flow Research Articles

A GPU-Based δ-Plus-SPH Model for Non-Newtonian Multiphase Flows

A multiphase extension of the δ-plus-SPH (smoothed particle hydrodynamics) model is developed for modeling non-Newtonian multiphase flow. A modified numerical diffusive term and special shifting treatment near the phase interface are introduced to the original δ-plus-SPH model to improve the accuracy and numerical stability of the weakly incompressible SPH model. The Herschel–Bulkley model is used to describe non-Newtonian fluids. A sub-particle term is added in the momentum equation based on a large eddy simulation. The graphic processing unit (GPU) acceleration technique is applied to increase the computational efficiency. Three test cases including, a static tank, Poiseuille flow, and submarine debris flow, are presented to assess the performance of the new multiphase SPH model. Comparisons with analytical solutions, experimental data, and previous numerical results indicate that the proposed SPH model can capture highly transient incompressible two-phase flows with consistent pressure across the interface.

Heat transmission in a magnetohydrodynamic multiphase flow induced by metachronal propulsion through porous media with thermal radiation

The motivation of the current study is to examine heat transmission through a non-Newtonian multiphase flow. Casson fluid is taken as the base fluid to form a particulate flow suspended with dust particles. Metachronal propulsion of two-phase flow is caused by the back and forth motion of tiny hair-like structures furnished at the opposite edges of the artery. Heat effects are further enhanced in the Magnetohydrodynamic (MHD) flow with the application of Lorentz force and nonlinear thermal radiation. An analytic solution is achieved for coupled differential equations by considering the assumption of wavelength and ignoring the inertial forces. Cilia-driven flows are very significant in removing or discarding mucus from lungs, arteries, and bloodstream. Finally, the analytic solution is validated by conducting a comprehensive parametric study that reveals that strong magnetic field and porosity parameter hamper the motion of the Casson fluid. More thermal energy is contributed to the system of multiphase flow by strong Hartman number.

Perturbation solution of the multiphase flows of third grade dispersions suspended with Hafnium and crystal particles

The current communication is a comparative analysis of multiphase flows through a steep channel. Third-grade fluid m is taken as the base liquid which suspends with Hafnium (Hf) particles and crystal particles. Bi-phase flows also experience the impact externally applied magnetic field that acts in the transverse direction to the flow. Highly nonlinear differential equation subject to given boundary conditions is solved analytically by using regular perturbation method. Further, a numerical solution is also obtained, and found both solutions in full agreement. Moreover, non-Newtonian multiphase flows have been compared with Newtonian multiphase flows, as well. The comparison reveals that the performance of Newtonian particulate flow is better than the one suspended with Third-grade fluid. Nevertheless, Hafnium metallic particles are more suitable for multiphase suspension as compared to crystal particles. This prominent feature is owing to the density of the metal that suggests that Hafnium alloy is the most appropriate application in the nuclear reactors, as a coolant. Further, it is observed that the velocity field declines against rising values of Hartmann and Froude numbers.

Numerical simulation of stratified waxy crude oil and water flows across horizontal pipes in the presence of wall heating

In the present work, a 3D numerical study was carried out to investigate the stratified flow of waxy crude oil-water through a horizontal pipe with a contraction-expansion placed in its midsection. Moreover, a uniform heat flux was applied to the pipeline wall to investigate its effect on the overall pressure drop across the pipeline and the two-phase flow pattern. Waxy crude oils are highly viscous fluids, and they exhibit non-Newtonian viscoplastic flow behavior. The governing equations of such non-Newtonian multiphase flows were discretized and solved using the finite volume method on a structured numerical grid. The volume of fluid (VOF) method was utilized to capture the oil-water interface. Waxy crude oil flowed in the laminar regime while a turbulent water flow field was assumed, and it was modeled using the well-known SST k-ω turbulence model. The effect of several parameters, such as heat flux, wax content of the crude oil, and oil inlet velocity, have been studied comprehensively. The results revealed that the overall pressure drop was extremely sensitive to the wax content. Moreover, the simulation results indicated that using a relatively low uniform heat flux can reduce the pressure drop, up to 25%. Finally, it is shown that by increasing oil velocity at the inlet, pressure drop monotonically increased.

A numerical approach for non-Newtonian two-phase flows using a conservative level-set method

A finite-volume based conservative level-set method is presented to numerically solve the non-Newtonian multiphase flow problems. One set of governing equations is written for the whole domain, and different phases are treated with variable material and rheological properties. Main challenging areas of numerical simulation of multiphase non-Newtonian fluids, including tracking of the interface, mass conservation of the phases, small timestep problems encountered by non-Newtonian fluids, numerical instabilities regarding the high Weissenberg Number Problem (HWNP), instabilities encouraged by low solvent to polymer viscosity ratio in viscoelastic fluids and instabilities encountered by surface tensions are addressed and proper numerical treatments are provided in the proposed method. The numerical method is validated for different types of non-Newtonian fluids, e.g. shear-thinning, shear-thickening and viscoelastic fluids using structured and unstructured meshes. The proposed numerical solver is capable of readily adopting different constitutive models for viscoelastic fluids to different stabilization approaches. The constitutive equation is solved fully coupled with the flow equations. The method is validated for non-Newtonian single-phase flows against the analytical solution of start-up Poiseuille flow and the numerical solutions of well-known lid-driven Cavity problem. For multiphase flows, impact of a viscoelastic droplet problem, non-Newtonian droplet passing through a contraction-expansion, and Newtonian/non-Newtonian drop deformation suspended in Newtonian/non-Newtonian matrix imposed to shear flow are solved, and the results are compared with the related analytical, numerical and experimental data.

Analysis of Polymer Crystallization with a Multiscale Modeling Approach

The main objective of the presented work is to describe the crystallization kinetics of semi-crystalline thermoplastics with a multiscale model implemented into the COMSOL software and the in-house developed code SphäroSim. The filling and cooling simulations, implemented by using the computational fluid dynamics (CFD) and heat transfer (HT) modules of COMSOL, require the simultaneous solution of non-Newtonian multi-phase flow (polymer/air) and thermal fields in non-isothermal condition and transient regime. The simulation results are collected, converted into the OpenSource file format VTK (Visualization Toolkit) and transferred to the SphäroSim code after a matching operation with the COMSOL mesh. The SphäroSim code uses COMSOL results as input data to compute crystallization kinetics, using the COMSOL data as boundary conditions in the microstructure simulation. This allows the time resolved calculation of the crystallization process and a prediction of the final microstructure in the part which can be used in further simulations such as a structural analysis. The analytical parameters needed to connect crystallization kinetics with molecular material properties and applying the analytical scheme to the numerical simulation during filling and cooling in an injection moulding process are identified.

Numerical investigation of Newtonian and non-Newtonian multiphase flows using ISPH method

We have presented a multiphase incompressible smoothed particle hydrodynamics method with an improved interface treatment procedure. To demonstrate the effectiveness of the interface treatment which can handle multiphase flow problems with high density and viscosity ratios, we have modeled several challenging two phase flow problems; namely, single vortex flow, square droplet deformation, droplet deformation in shear flow, and finally the Newtonian bubble rising in viscous and viscoelastic liquids. The proposed interface treatment includes the usage of (i) different smoothing functions (in this work, cubic spline kernel function for discretizing equations associated with the calculation of the surface tension force while the quintic spline for the discretization of governing equations and the relevant boundary conditions), and (ii) a new discretization scheme for calculating the pressure gradient. It is shown that with the application of the improved interface treatment, it becomes possible to model multiphase flow problems with the density and viscosity ratios up to 1000 and 100 respectively while using standard projection method. The utilization of cubic spline for the continuum surface force model significantly improves the quality of the calculated interface, thereby eliminating the interphase particle penetrations, and in turn leading to the calculation of more accurate velocity and pressure fields.

Non-Newtonian multi-phase flows: On drag reduction, pressure drop and liquid wall friction factor

The present work focuses on the non-Newtonian liquid drag reduction by gas injection. Two regimes are taken in consideration: fully stratified gas shear-thinning liquid flow and gas shear-thinning liquid slug flow regimes. Predictions of drag reduction ratio and holdup are presented for the stratified flow of gas and non-Newtonian Ostwald-de Waele liquid. Fully stratified flow is considered and the approach developed in Taitel and Dukler (1976) is used. For these regimes, CMC (CarboxyMethyl Cellulose) solution is used in order to investigate the behaviour of the gas and non-Newtonian liquids in horizontal pipes. Results have been reformulated and an extension to interfacial Andreussi and Persen (1987) correlation has been carried out for stratified regimes. For slug flow regimes, the mechanistic slug unit model is adopted in order to estimate the pressure gradients along the slug unit. The slug unit model is rearranged and reinterpreted as inviscid Burgers's equation for incompressible phases. For both stratified and slug flow regimes, three dimensional CFD (computational fluid dynamics) simulations were performed in order to compare the drag reduction ratio and pressure gradients. In stratified flows, CFD is also used in an attempt to evaluate the liquid wall friction factor and to compare the obtained values with those given by empirical standard correlations.

Numerical Modelling of Cake Formation and Fluid Loss from Non-Newtonian Muds During Drilling Using Eccentric/Concentric Drill Strings With/Without Rotation

This paper describes a numerical procedure for modelling mud cake growth and fluid invasion during drilling. Two three-dimensional finite element programs have been developed, one to model the non-Newtonian flow of the drilling mud in the annulus between the drill string and the borehole wall, and the other to model the non-Newtonian multiphase flow of the fluid base of the mud into the surrounding porous formation. These are integrated into a time-stepping routine and a crossflow microfiltration model is employed to predict the increase in cake thickness at nodes on the borehole wall at each time step. The procedure is applied to the model of a borehole with an eccentric drill string giving the thickness of the cake, the velocity of the permeating fluid and the saturation of the fluid in the surrounding formation at different times. The effects of changing the eccentricity of the drill string and the power law exponent of the mud are also investigated.