Fluid Flow Motion Research Articles

Motion analysis of a spherical solid particle in plane Couette Newtonian fluid flow

In this article, the motion of a spherical particle in a plane Couette Newtonian fluid flow is studied. The governing equations of a spherical solid particle's motion in the plane Couette fluid flow are investigated using the Differential Transformation Method (DTM) and a Padé approximant which are an analytical solution technique. For validation of the analytical solution, the governing equation is solved numerically. The horizontal and vertical velocities of spherical solid particle are shown for different fluids and values of the embedding parameters. The DTM–Padé results indicate that the horizontal and vertical velocities of spherical solid particle in water fluid are higher than the glycerin and ethylene-glycol fluids. Also the horizontal and vertical velocities increase with an increase in the particle radius. Comparison of the results (DTM and numerical) was shown that the analytical method and numerical data are in a good agreement with each other.

Alternating current electrokinetics enhanced in situ capacitive immunoassay.

A rapid in situ capacitive immunoassay is presented herein. Conventional immunoassay typically relies on diffusion for transport of analytes in many cases causing long detection time and lack of sensitivity. By integrating alternating current electrokinetics (ACEK) and impedance sensing, this work provides a rapid in situ capacitive affinity biosensing. ACEK induces both fluid flow and particle motion, conveying target molecules toward electrodes immobilized with probes, resulting in rapid enrichment of target molecules and a capacitance change at the ''electrode-fluid'' interface. The benefit of ACEK enhanced immunoassay was demonstrated using the antigen and antibody from Johne's disease (JD) as an example. To clarify the importance of DEP and ACET effects for binding reaction, two different electrode pattern designs for capacitive immunoassay are studied. The asymmetric array and symmetric electrodes exhibit very similar response at lower electric field due to DEP effects, while asymmetric array has remarkable higher response at high-electric field because the convection becomes more important at high field. The disease positive and negative serum samples are distinguished in few minutes.

Magnetic resonance imaging measures of posterior cranial fossa morphology and cerebrospinal fluid physiology in Chiari malformation type I.

It has been well documented that, along with tonsillar herniation, Chiari Malformation Type I (CMI) is associated with smaller posterior cranial fossa (PCF) and altered cerebrospinal fluid (CSF) flow and tissue motion in the craniocervical junction. This study assesses the relationship between PCF volumetry and CSF and tissue dynamics toward a combined imaging-based morphological-physiological characterization of CMI. Multivariate analysis is used to identify the subset of parameters that best discriminates CMI from a healthy cohort. Eleven length and volumetric measures of PCF, including crowdedness and 4th ventricle volume, 4 measures of CSF and cord motion in the craniocervical junction, and 5 global intracranial measures, including intracranial compliance and pressure, were measured by magnetic resonance imaging (MRI) in 36 symptomatic CMI subjects (28 female, 37 ± 11 years) and 37 control subjects (24 female, 36 ± 12 years). The CMI group was further divided based on symptomatology into "typical" and "atypical" subgroups. Ten of the 20 morphologic and physiologic measures were significantly different between the CMI and the control cohorts. These parameters also had less variability and stronger significance in the typical CMI compared with the atypical. The measures with the most significance were clival and supraocciput lengths, PCF crowdedness, normalized PCF volume, 4th ventricle volume, maximal cord displacement (P < .001), and MR measure of intracranial pressure (P = .007). Multivariate testing identified cord displacement, PCF crowdedness, and normalized PCF as the strongest discriminator subset between CMI and controls. MR measure of intracranial pressure was higher in the typical CMI cohort compared with the atypical. The identified 10 complementing morphological and physiological measures provide a more complete and symptomatology-relevant characterization of CMI than tonsillar herniation alone.

Numerical analysis of fluid flow and particle entrainment in a novel tapered rotating fluidized bed

A rotating fluidized bed is a promising fluidization technique for handling of fine particles, classified into the Geldart׳s group-C. However, significant particle entrainment has been a major hurdle for its practical use. We here proposed a novel tapered rotating fluidized bed to reduce the particle entrainment. The fluidized bed vessel of the tapered rotating fluidized bed has the geometry of a cylinder with two frustum ends. The main purpose of this paper is to evaluate a performance of the tapered rotating fluidized bed in reducing the particle entrainment. A computer simulation using a computational fluid dynamics and discrete phase model was conducted to numerically analyze how the fluid flow and particle motion ejected to the freeboard are changed when the vessel geometry is altered. The simulation results revealed that by modifying the geometry of the vessel to the tapered geometry the fluid velocity in the radial direction toward the exit is significantly decreased, while the fluid velocity in the tangential direction is increased. The simulation results also revealed that the maximum particle size of the entrained particles is reduced with an increase in the taper angle: the particle entrainment can be effectively reduced by merely changing the vessel geometry to the tapered geometry. The experimental results showed that amount of entrained particles was significantly decreased when the tapered vessel was used, confirming that the proposed tapered rotating fluidized bed is effective to reduce the particle entrainment.

Towards a complete model of soil liquefaction: the importance of fluid flow and grain motion

When loosely packed water-saturated granular soils, for example sands, are subjected to strong earthquake shaking, they may liquefy, causing large deformations with great destructive power. The phenomenon is quite general and occurs in any fluid-saturated granular material and is a consequence of the transfer of stress from inter-grain contacts to water pressure. In modern geotechnical practice, soil liquefaction is commonly considered to be an ‘undrained’ phenomenon; pressure is thought to be generated because earthquake deformations are too quick to allow fluid flow, which enables water depressurization. Here, we show via a first principles analysis that liquefaction is not a strictly undrained process; and, in fact, it is the interplay between grain rearrangement, fluid migration and changes in permeability, which causes the loss of strength observed in so many destructive earthquake events around the world. The results call into question many of the common laboratory and field methods of evaluating the liquefaction resistance of soil and indicate new directions for the field, laboratory and scale-model study of this important phenomenon.

Towards the optimisation and adaptation of dry powder inhalers.

Pulmonary drug delivery by dry powder inhalers is becoming more and more popular. Such an inhalation device must insure that during the inhalation process the drug powder is detached from the carrier due to fluid flow stresses. The goal of the project is the development of a drug powder detachment model to be used in numerical computations (CFD, computational fluid dynamics) of fluid flow and carrier particle motion through the inhaler and the resulting efficiency of drug delivery. This programme will be the basis for the optimisation of inhaler geometry and dry powder inhaler formulation. For this purpose a multi-scale approach is adopted. First the flow field through the inhaler is numerically calculated with OpenFOAM(®) and the flow stresses experienced by the carrier particles are recorded. This information is used for micro-scale simulations using the Lattice-Boltzmann method where only one carrier particle covered with drug powder is placed in cubic flow domain and exposed to the relevant flow situations, e.g. plug and shear flow with different Reynolds numbers. Therefrom the fluid forces on the drug particles are obtained. In order to allow the determination of the drug particle detachment possibility by lift-off, sliding or rolling, also measurements by AFM (atomic force microscope) were conducted for different carrier particle surface structures. The contact properties, such as van der Waals force, friction coefficient and adhesion surface energy were used to determine, from a force or moment balance (fluid forces versus contact forces), the detachment probability by the three mechanisms as a function of carrier particle Reynolds number. These results will be used for deriving the drug powder detachment model.

High accuracy analysis for motion of a spherical particle in plane Couette fluid flow by Multi-step Differential Transformation Method

In this study, coupled equations of particle's motion in Couette fluid flow are solved by Multi-step Differential Transformation Method (Ms-DTM) considering the rotation and shear effects on lift force and neglecting gravity. The precious achievement of the present work is introducing a new, fast and efficient analytical technique for spherical particles in plane Couette fluid flow over the previous numerical and analytical results in the literature. Also, obtained values are compared with numerical solution and HPM–Pade which recently are done by Torabi et al. It is shown that presented method gives approximations with a high degree of accuracy and least computational effort for studying particle motion in Couette fluid flow without the need for any linearization, discretization or perturbation against the previous work. Also, the acceleration profiles of the particle are presented and positions of the particle in each 1s time step are depicted graphically in the current study.

On a linearized system arising in the study of viscous surface flow down an inclined plane

We consider the linearized problem describing motion of a viscous incompressible fluid flow down an inclined plane under the effect of gravity. We formulate the problem for downward periodic disturbances from the laminar steady flow as an evolution equation in the product of Sobolev spaces \(H^{\frac{3}{2}}_0({\mathbb {T}}) \times {\mathbb {P}}^0H^0(\Omega ) \). It is crucial to study qualitative behavior of solutions that the operator arising in the linearized problem has compact resolvent operators and generates an analytic semigroup in \(H^{\frac{3}{2}}_0({\mathbb {T}}) \times {\mathbb {P}}^0H^0(\Omega ) \).

Computational Fluid Dynamic Using Parallel Loop of Multi-Cores Processor

Computational Fluid Dynamics (CFD) software is often used to study fluid flow and structures motion in fluids. The CFD normally requires large size of arrays and computer memory and then caused long execution time. However, Innovation of computer hardware such as multi-cores processor provides an alternative solution to improve this programming performance. This paper discussed loop parallelize multi-cores processor for optimization of sequential looping CFD code. This loop parallelize CFD was achieved by applying multi-tasking or multi-threading code into the original CFD code which was developed by one of the authors. The CFD code was developed based on Reynolds Average Navier-Stokes (RANS) method. The new CFD code program was developed using Microsoft Visual Basic (VB) programming language. In the early stage, the whole CFD code was constructed in a sequential flow before it is modified to parallel flow by using VBs multi-threading library. In the comparison, fluid flow around the hull of round-shaped FPSO was selected to compare the performance of both the programming codes. Besides, executed results of this self-developed code such as pressure distribution around the hull were also presented in this paper.

Analytical solution of heat transfer of oscillating flow at a triangular pressure waveform

Oscillating motion of fluid flow in a capillary tube can produce a nonlinear thermal boundary layer resulting in an increase of heat transfer coefficient. In the current investigation, an oscillating motion of fluid flow in a round tube was investigated to determine a triangular waveform effect on the heat transfer coefficient. An analytical solution of laminar Newtonian flow with a triangular pressure waveform was obtained. Results show that the heat transfer coefficient of the oscillating flow depends on the fluid properties and oscillating waveform. The triangular waveform of oscillating motion can result in a higher heat transfer coefficient.

Investigating the Applicability of Combined Lattice Boltzmann-Smoothed Profile Methods in Particulate Systems

In this article, a combination of Lattice-Boltzmann method (LBM) and smoothed profile method (SPM) are used in simulation of one, two, and many particles’ motion in fluid flow. SPM is used as the simulation method for particles motion. A shear flow is produced using a) solid walls for which standard bounce-back (SBB) boundary condition is applied and b) Lees-Edwards boundary conditions (LEBC). Simulation of Couette flow problem of fluid-only system reveals the accuracy of both methods. LBM-SPM coupled with LEBC is applied for flow geometries of one and two particles in a shear flow. Comparison of results obtained from simulation of one and two interacting particles using moving walls with SBB with those in the literature shows good correspondence. In addition, for the case of many particles, the effective viscosity of a suspension of circular particles which are placed randomly between two parallel walls is investigated from dilute to dense regimes. Relative bulk viscosity is compared with theoretical and semi-empirical results of other investigators and satisfactory agreement is found. Finally, a combination of SPM-LBM is examined for sedimentation of one, two and many particles. Numerical results show suitability of LBM-SPM with LEBC for simulation of particles suspended in flow.

VORTICES IN BIOLOGICAL FLOWS

Vortices in flow past a heart valve, in streams and behind an arrow were realized, sketched and discussed by Leonardo da Vinci. The forced resonance and collapse of the Tacoma Narrows Bridge under 64 km/h. wind in 1940 and the Kármán vortex street are classic examples of dynamic interaction between fluid flow and solid motion. There are similar and dissimilar characteristics of vortices between biological and physical flow processes. They can be analyzed by numerical solutions of the Navier–Stokes equations with moving boundaries. One approach is to transform the time-dependent domain to a fixed domain with the geometric, kinematic and dynamic parameters as forcing functions in the Navier–Stokes equations.

Some low order nonconforming mixed finite elements combined with Raviart–Thomas elements for a coupled Stokes–Darcy model

In this paper, we discuss numerical methods to solve a coupled Stokes–Darcy system. The deformation tensor form of Stokes equations is used to describe the fluid flow motion. The mixed form of elliptic equation is applied to describe the porous media flow motion. We propose finite element methods for the coupled problem. For Stokes equations, one component of the velocity is approximated by Crouzeix–Raviart element or Rannacher–Turek element, and the other component is approximated by conforming P1 or Q1 element; pressure is approximated by piecewise constants. For the mixed form of elliptic equation, the lowest order triangular/quadrilateral Raviart-Thomas element is used. The discrete mesh is nonmatching on the interface. By Boland-Nicolaides trick, the inf-sup condition of the discrete problem is proved. Moreover, we construct a new interpolation operator to derive the a priori error estimate of the proposed finite element method. Numerical examples are also given to confirm the theoretical results.

Novel paradigms for dialysis vascular access: upstream hemodynamics and vascular remodeling in dialysis access stenosis.

Failure of hemodialysis access is caused mostly by venous intimal hyperplasia, a fibro-muscular thickening of the vessel wall. The pathogenesis of venous neointimal hyperplasia in primary arteriovenous fistulae consists of processes that have been identified as upstream and downstream events. Upstream events are the initial events producing injury of the endothelial layer (surgical trauma, hemodynamic shear stress, vessel wall injury due to needle punctures, etc.). Downstream events are the responses of the vascular wall at the endothelial injury that consist of a cascade of processes including leukocyte adhesion, migration of smooth muscle cells from the media to the intimal layer, and proliferation. In arteriovenous fistulae, the stenoses occur in specific sites, consistently related to the local hemodynamics determined by the vessel geometry and blood flow pattern. Recent findings that the localization of these sites matches areas of disturbed flow may add new insights into the pathogenesis of neointimal hyperplasia in the venous side of vascular access after the creation of the anastomosis. The detailed study of fluid flow motion acting on the vascular wall in anastomosed vessels and in the arm vasculature at the patient-specific level may help to elucidate the role of hemodynamics in vascular remodeling and neointimal hyperplasia formation. These computational approaches may also help in surgical planning for the amelioration of clinical outcome. This review aims to discuss the role of the disturbed flow condition in acting as upstream event in the pathogenesis of venous intimal hyperplasia and in producing subsequent local vascular remodeling in autogenous arteriovenous fistulae used for hemodialysis access. The potential use of blood flow analysis in the management of vascular access is also discussed.

Nonlinear analysis of the pressure field in industrial buildings with curved metallic roofs due to the wind effect by FEM

In this paper, an evaluation of distribution of the air pressure is determined throughout the laterally closed industrial buildings with curved metallic roofs due to the wind effect by the finite element method (FEM). The non-linearity is due to Reynolds-averaged Navier–Stokes (RANS) equations that govern the turbulent flow. The Navier–Stokes equations are non-linear partial differential equations and this non-linearity makes most problems difficult to solve and is part of the cause of turbulence. The RANS equations are time-averaged equations of motion for fluid flow. They are primarily used while dealing with turbulent flows. Turbulence is a highly complex physical phenomenon that is pervasive in flow problems of scientific and engineering concern like this one. In order to solve the RANS equations a two-equation model is used: the standard k–ɛ model. The calculation has been carried out keeping in mind the following assumptions: turbulent flow, an exponential-like wind speed profile with a maximum velocity of 40m/s at 10m reference height, and different heights of the building ranging from 6m to 10m. Finally, the forces and moments are determined on the cover, as well as the distribution of pressures on the same one, comparing the numerical results obtained with the Spanish CTE DB SE-AE, Spanish NBE AE-88 and European standard rules, giving place to the conclusions that are exposed in the study.

Simulations of the breakup of liquid filaments on a partially wetting solid substrate

We report direct numerical simulations of liquid filaments breaking up into droplets on partially wetting substrates. It is motivated by recent experiments, linear stability analyses, and lubrication-based calculations. The fluid flow is governed by the Stokes equations and the contact line motion is handled by a phase-field model, which also serves to capture the interfacial motion. The coupled Stokes and Cahn-Hilliard equations are solved using a finite-element algorithm in three dimensions. This avoids additional approximations of the fluid flow or contact line motion, and allows us to compute arbitrary contact angles on the substrate. We simulate both the breakup of infinite liquid filaments via growing capillary waves and that of finite liquid filaments with drops pinching off from the ends, with a focus on the effect of the wetting angle. In both cases, substrate hydrophobicity promotes breakup of the thread, and decreases the spacing of the daughter drops. The results show the differences in the two processes and in the final drop size and spacing. The development of capillary waves agrees well with prior linear analysis and the end-pinching results offer new insights into this poorly understood phenomenon.

Exact Solutions for the Incompressible Electrically Conducting Viscous Flow between two Moving Parallel Disks in Unsteady Magneto Hydrodynamic and Stability Analysis

The main interest of the present investigation is to generate exact solutions to the steady Navier-Stokes equations for the incompressible Newtonian viscous electrically conducting fluid flow motion and stability due to disks moving towards each other or in opposite directions with a constant velocity. Making use of the analytic solution, the description of possible conditions of motion is based on the exact solutions of the Navier-Stokes equations. Both stationary and transient cases have been considered. The stability of motion is analyzed for different initial perturbations. Different types of stability were found according to whether the disks moved towards or away from each other.

Simulation of Fluid Flow in Centrifugal Tricanter

Abstract An ANSYS simulation of the multiphase complex fluid flow motion in a centrifugal device (tricanter) is presented in the paper. This centrifugal device is designed for one step efficient solution for contaminated river water processing with oil and oil products. The proposed tricanter is one of the main objectives of the project named “Common strategy to prevent the Danube’s pollution technological risks with oil and oil products CLEANDANUBE” financed by European Commission within the frame of Romania-Bulgaria Trans-Border Cooperation Program 2007 - 2013 (grant MIS-ETC code 653). Results for liquid phases (water and oil products) and for solid particles motion are presented graphically and are commented.

On Mesoscale Modelling of dsDNA Molecules in Fluid Flow

The paper presents a new mesoscale modelling approach to investigation of dsDNA molecules motion in fluid flow. The proposed method includes the effects of inertia and is capable of capturing accurately dsDNA relaxation and stretching phenomena. The accuracy of the proposed method is explored through comparisons with published experimental data. For the simulation of disengaged dsDNA molecules, a novel correction to the elastic force formulation is suggested. The proposed adjustment offers a significant improvement in the prediction of dsDNA length for both relaxation in resting buffer and extension using hydrodynamic focusing. Analysis of the individual contributions to the force acting on the dsDNA molecules demonstrates that the dynamics of dsDNA extension observed experimentally is dominated by the hydrodynamic drag force.

A new design for efficient dielectrophoretic separation of cells in a microdevice

Effectiveness of a continuous biological cell separation device can be improved significantly by increasing the distance among different types of cells. To achieve this, most of the recent dielectrophoresis based continuous separation devices implement differential forces on cells either along the transverse direction or the vertical direction with respect to the bulk fluid flow motion. However, interparticle distance can be increased further by implementing forces along both transverse and vertical planes. In this article, a design for a microfluidic platform has been proposed where a new electrode configuration is identified to implement symmetric forces in both vertical and transverse directions. A numerical model, which considers presence of particles in the electric field and flow field, shows a much higher interparticle distance between red blood cells and plasmodium falciparum infected red blood cells in such a device than that in a conventional separation device. This configuration also reduces the possibility of particle trapping on the electrodes, which is a major bottleneck of dielectrophoresis.