Fluid Flow Profiles Research Articles

Stereolithographic additive manufacturing of ceramic components with functionally modulated structures

Stereolithographic additive manufacturing (STL-AM) was newly developed as a direct forming process for fine ceramic components. Two-dimensional (2D) cross sections were created through ultraviolet laser drawing on spread photosensitive resin paste, including ceramic nanoparticles, and three-dimensional (3D) composites were sterically printed by layer laminations and interlayer joining. The formed precursors were dewaxed and sintered along optimized heat treatment patterns. Functionally geometric modulations by computer-aided design, manufacture, and evaluation (CAD/CAM/CAE) were successively reviewed. Fluctuated features were introduced into solid components through inverse Fourier transformations. Fluid flow profiles in aqueous environments were numerically simulated to profile smooth streamlines. Graded porosities were elaborated in calcium phosphate scaffolds of artificial cancerous bones. The coordination number and aspect ratios of the microlattices were systematically modulated for cytapheresis and metabolism. Structural dimensions with integer or fractional values were estimated to be able to comprehensively discuss the compatibilities of spatial element dispersions and directional mass transfers.

Influence of timing between magnetic field and fluid flow in a rotary magnetic refrigerator

An active magnetic regenerator with magnetic Brayton cycle is adopted in a rotary-magnet type refrigerator. For the performance of the magnetic refrigerator, timing between the magnetic field and fluid flow profiles is important. This paper experimentally studied the influence of timing between magnetic field profile and fluid flow profile on the performance of a rotary magnetic refrigerator. A timing ratio is defined to indicate the relative time lengths of four processes (magnetization, hot blow, demagnetization, cold blow). Under four different timing ratios, the cooling capacity, temperature span, pressure drop and power consumption are experimentally investigated. A no-load temperature span of 19.8 K is achieved at the timing ratio of 1:4:1:4, which is 2.6 K higher than that at the ratio of 1:1:1:1. The results reveal that, at the same utilization factor and frequency, the longer the flow time, the larger the temperature span. The influence of utilization factor and operating frequency are also studied. Though limited by the motor power, a cooling power of 20 W at temperature span of 12.3 K is achieved with the timing ratio of 1:2:1:2 at 0.75 Hz, and the corresponding specific cooling power is approximately 94 W/kg.

Lymph Node Subcapsular Sinus Microenvironment-On-A-ChipModeling Shear Flow Relevant to Lymphatic Metastasis and Immune Cell Homing.

SummaryA lymph node sinus-on-a-chip adhesion microfluidic platform that recapitulates the hydrodynamic microenvironment of the lymph node subcapsular sinus was engineered. This device was used to interrogate the effects of lymph node remodeling on cellular adhesion in fluid flow relevant to lymphatic metastasis. Wall shear stress levels analytically estimated and modeled after quiescent and diseased/inflamed lymph nodes were experimentally recapitulated using a flow-based microfluidic perfusion system to assess the effects of physiological flow fields on human metastatic cancer cell adhesion. Results suggest that both altered fluid flow profiles and presentation of adhesive ligands, which are predicted to manifest within the lymph node subcapsular sinus as a result of inflammation-induced remodeling, and the presence of lymph-borne monocytic cells may synergistically contribute to the dynamic extent of cell adhesion in flow relevant to lymph node invasion by cancer and monocytic immune cells during lymphatic metastasis.

Flow and hydrodynamic shear stress inside a printing needle during biofabrication.

We present a simple but accurate algorithm to calculate the flow and shear rate profile of shear thinning fluids, as typically used in biofabrication applications, with an arbitrary viscosity-shear rate relationship in a cylindrical nozzle. By interpolating the viscosity with a set of power-law functions, we obtain a mathematically exact piecewise solution to the incompressible Navier-Stokes equation. The algorithm is validated with known solutions for a simplified Carreau-Yasuda fluid, full numerical simulations for a realistic chitosan hydrogel as well as experimental velocity profiles of alginate and chitosan solutions in a microfluidic channel. We implement the algorithm in an easy-to-use Python tool, included as Supplementary Material, to calculate the velocity and shear rate profile during the printing process, depending on the shear thinning behavior of the bioink and printing parameters such as pressure and nozzle size. We confirm that the shear stress varies in an exactly linear fashion, starting from zero at the nozzle center to the maximum shear stress at the wall, independent of the shear thinning properties of the bioink. Finally, we demonstrate how our method can be inverted to obtain rheological bioink parameters in-situ directly before or even during printing from experimentally measured flow rate versus pressure data.

Modeling a Dielectrophoretic Microfluidic Device with Vertical Interdigitated Transducer Electrodes for Separation of Microparticles Based on Size.

This article conceptualizes and mathematically models a dielectrophoretic microfluidic device with two sets of interdigitated transducer vertical electrodes for separation of a binary heterogeneous mixture of particles based on size; each set of electrodes is located on the sidewalls and independently controllable. To achieve separation in the proposed microfluidic device, the small microparticles are subjected to positive dielectrophoresis and the big microparticles do not experience dielectrophoresis. The mathematical model consists of equations describing the motion of each microparticle, fluid flow profile, and electric voltage and field profiles, and they are solved numerically. The equations of motion take into account the influence of phenomena, such as inertia, drag, dielectrophoresis, gravity, and buoyancy. The model is used for a parametric study to understand the influence of parameters on the performance of the microfluidic device. The parameters studied include applied electric voltages, electrode dimensions, volumetric flow rate, and number of electrodes. The separation efficiency of the big and small microparticles is found to be independent of and dependent on all parameters, respectively. On the other hand, the separation purity of the big and small microparticles is found to be dependent on and independent of all parameters, respectively. The mathematical model is useful in designing the proposed microfluidic device with the desired level of separation efficiency and separation purity.

A Study of Fractional Relaxation Time Derivative on Blood Flow in Arteries with Magnetic and Thermal Radiation Effects

In this paper, a fractional relaxation model is studied to determine the effect of heat transfer and magnetic field on the blood flow. The flow is due to an oscillating periodic pressure gradient and body acceleration. We apply Laplace transform as well as finite Hankel transform to obtain the closed form solutions of the velocity and temperature distributions of the fractional time partial differential equations. Effect of the fluid flow parameters are shown graphically with changes in the ordinary model as well as the fractional parameters. The analysis shows that the fractional derivative is an excellent tool which gives remarkable change in controlling temperature and blood flow. The analysis depicts graphically, that in the presences of strong applied (exterior) magnetic field, reduces the temperature and blood flow velocities, which is appropriate to avoid tissues damage during treatment. In addition, it is seen that some of the aforementioned parameters influenced the fluid flow profiles in increasing and decreasing fashion which is interpreted as useful to the study.

Boundary Layer Flow of a Nanofluid Through a Permeable Medium Due to Porous Plate

In the present article, an attempted have been made to study the behavior of boundary layer viscous fluid flow and heat transfer containing some nanosized solid particles flowing through a permeable porous medium. The problem was first modeled into a coupled system of nonlinear partial differential equations of conservation of mass, momentum and nanoparticle concentration. The system of coupled nonlinear boundary layer partial differential equations governing the flowing fluid momentum and heat transfer characteristics are reduced to a new simplified coupled nonlinear system of ordinary differential equations by means of a suitable similarity transformation. The transformed set of nonlinear coupled ordinary differential equations is than solved numerically by means of the fourth order numerical scheme the Runge-Kutta shooting method. The effects of important involved parameters that control the flow field and heat transfer characteristics, that is the viscosity parameter, the convection parameter, the Porosity parameter, the Prandtl number and the Lewis number have been obtained and discussed. Numerical solutions for velocity and temperature are sketched and graphically analyzed. The graphical results observed are indicating that by increasing the values of the non-dimensional viscosity parameter, the dimension less fluid flow profile increases, while for increasing values of the nanoparticles Brownian motion parameter, the nanoparticle concentration profile increases.

Analysis of fully developed mixed convection in open-ended annuli with viscous dissipation

The vertical, open-ended double-passage annular space between three vertical concentric co-axial cylinders is an important geometry representing significant number of industrial applications. For a design engineer, the knowledge of fully developed mixed convection in this geometry is very essential. Hence, in this paper, it is proposed to numerically as well as analytically investigate the fully developed mixed convective flow in the vertical annuli having two annular passages with open upper and lower boundaries by taking viscous dissipation into consideration. The prime objective of the analysis is to bring out the influences of the location of middle cylinder, known as baffle, and viscous dissipation on the fluid flow and temperature profiles as well as the associated thermal transport rates. By neglecting the viscous dissipation influences, exact solutions are determined, while the finite difference-based numerical solutions are achieved in the presence of viscous dissipation. Further, excellent agreement is obtained between the analytical and numerical solutions under limiting conditions. The roles of viscous dissipation and baffle location are meticulously brought out through the flow pattern, temperature profiles and heat transport rates.

Magnetic Effects on Second Grade Fluid Flow due to Non Coaxial Rotation of a Disk Through a Porous Medium with Double Diffusion

In this paper, the unsteady of magnetohydrodynamics (MHD) second grade fluid in a porous medium due to non-coaxial rotation is investigated. The effects of heat and mass transfers (double diffusion) through an oscillating disk are considered. The non-dimensional governing momentum, energy and mass equations are obtained by using the suitable non-dimensional variables. The Laplace transform method is used to obtain the exact solutions of non-dimensional velocity, temperature and concentration profiles. The expressions of skin friction, Nusselt number and Sherwood number are also presented. The numerical result for all fluid flow profiles are plotted in graphs for the different parameters studied. The results also show that, velocity for present solution (with heat and mass transfers) has a significant impact on the velocity profiles in non-coaxial rotation due to exhibits high thermal diffusivity and thermal conductivity. The obtained exact solutions are found to be identical to the Guria [10]. It is worth mentioning that, the exact solutions are in excellent agreement with the numerical solutions of Inverse Laplace transform obtained by Gaver-Stehfest algorithm.

Estimation of the Fluid Velocity Profile in the Stratification Zone of a Falcon Concentrator

The Falcon concentrator is capable of separating minerals in fine size classes based on their differential density. Separation of mineral particles depends upon the fluid flow characteristics and relative movement of particles in a fluid. In the present study, a fluid flow characteristic inside the Falcon concentrator was established through experimentation and modeling. The Falcon concentrator has two fluid entry points: (a) Fluid entering through gravity assisted feeding system and (b) Fluid entering through the fluidized hole on the concentrator wall. In order to identify the role of fluid entering the concentrator, a tracer was injected into the system. As per the tracer based experimentation, it was established that fluid entering through the gravity based feeding system is responsible for thin flowing film formation in the stratification zone where particles are stratified based on their relative density. The momentum balance and continuity equations were simplified for a high centrifugal force field, and the fluid velocity profile was estimated inside the thin flowing film. Estimated fluid flow profiles will help to simulate the particle trajectories inside the Falcon concentrator. The influence of rotational speed, fluid flow rate, and cone angle on the fluid velocity profile were investigated. Fluid thickness over the concentrator wall is also estimated, and it is typically of the order of ~150–200 μm.

Vortex Prediction in a Pump Intake System Using Computational Fluid Dynamics

A pump intake system consists of forebay, pumpbay and pipeline arrangements through which water flows in order to meet its demand. Vortices and velocity fluctuations affects the performance of a pump intake system. This paper presents the vortex prediction in a pump sump for varying flow conditions across the pump bay and the bellmouth section, using computational fluid dynamics (CFD) code Flow 3D. Geometry of rectangular type sump was chosen for comparing the physical experimentation with the computational model. The velocity fluctuations, location of vortex formation and its profiles predicted by CFD code was compared with that of the physically observed experiments. The velocity and fluid flow profiles predicted by CFD correlated well with the flow conditions observed during the physical experiments. Further, characteristics of vortex were also studied with respect to the velocity change. Increase in the wobbling phenomenon of the vortex with increase in the flow velocity was also identified with the computational studies. CFD can be used as a tool to study the preliminary design of a hydraulic system for a particular field condition, thus complementing the physical model studies to facilitate the construction of an optimized and effective pump intake system.

Non-linear Thermal Radiative Analysis on Hydromagnetic Nanofluid Transport Through a Rotating Cone

The influence of Stefan blowing on non-linear magneto nanofluid transport through a rotating cone is addressed. The governing equations are modeled. The final controlled non-linear ordinary differential equations are obatained through similarity transformations. The numerical solutions have been computed with the aid of Runge–Kutta process together with shooting approach. Fluid flow profiles like velocity profiles, temperature profiles and concentration profiles for important pertinent parameters are presented and the physical description is reported with the help of graphs. The obtanied results are compared with the Present results. They provide good agreement with the present thermal analysis. The skin friction coefficient, Nusselt number and Sherwood number are enhanced for radiation parameter while the reverse effect is seen in magnetic parameter. Swirl velocity is suppressed with the mounting estimates of permeability parameter, mixed convection parameter and nonlinear convection parameter due to temperature. Growth in concentration is appeared with upgraded estimates of permeability parameter and thermophoresis parameter.

Dendrite growth direction measurements: understanding the solute advancement in continuous casting of steel

Maintaining competitiveness in steel manufacturing requires improving process efficiency and production volume whilst enhancing product quality and performance. This is particularly challenging for producing value-added advanced steel grades such as advanced high strength steels and electrical steels. These grades due to higher weight percentage of alloying elements cause difficulties in various stages of upstream and downstream processing, and this includes continuous casting, wherein high solute levels are critical towards macro-segregation. Interface growth direction in systems with more than one component is dictated by the solute profile ahead of the moving solidification front. Understanding the profile of growth direction with casting process parameters during the progress of casting will provide an important perspective towards reducing the macro-segregation in the cast product. In the present study, two steel slab samples from conventional slab caster under the influence of electromagnetic brake (EMBR) at Tata Steel in IJmuiden (The Netherlands) have been investigated for dendrite deflection measurements. The samples showed a transition zone where a change in the deflection behavior occurs. Also, the magnitude of the deflection angle decreases away from the slab surface. Correlating these experimental data with modeled fluid flow profile will help in improving the understanding of the dynamic nature of the solute advancement so that the casting parameters can be optimized to improve product quality.

Three-dimensional biomagnetic Maxwell fluid flow over a stretching surface in presence of heat source/sink

The present paper deals with the study of three-dimensional boundary layer flow of biomagnetic Maxwell fluid over a plane horizontal surface stretched linearly along two mutually perpendicular directions. Basic principles of magnetohydrodynamics (MHD) and ferro-hydrodynamics (FHD) have been employed. The effect of heat generation/absorption has been taken into consideration. The study is theoretical and is conducted by using a combination of approximate and numerical techniques. By using the method of similarity transformation, the governing nonlinear partial differential equations are converted into a set of coupled ordinary differential equations. In the sequel, a suitable numerical method has been developed to solve the coupled differential equations. The accuracy of the numerical method has been checked by comparing the numerical results with those of an earlier study reported in available literatures. Effects of various parameters involved in the study, viz. the magnetohydrodynamic and ferromagnetic parameters, Deborah number, stretching ratio and heat generation on the fluid flow profiles are investigated and the results have been presented graphically. Variations of the skin friction, heat transfer rate and relative wall pressure with change in hydrodynamic and ferromagnetic parameters have also been illustrated. It is found that due to the influence of the Kelvin force, the velocity component in [Formula: see text]-direction is greater than the corresponding one in the hydrodynamic case, but the opposite is true for the velocity component in the [Formula: see text]-direction. We also found that the temperature of the fluid for hydrodynamic flow is greater than that for MHD or FHD flow. It is even greater for BFD flows. The numerical results of the study reveal that the characteristics of blood flow are significantly affected by the presence of a magnetic field.

Numerical simulation of electrokinetic dissipation caused by elastic waves in reservoir rocks

The use of electrokinetic dissipation method to study the fluid flow law in micro-pores is of great significance to reservoir rock microfluidics. In this paper, the micro-capillary theory was combined with the coupling model of the seepage field and the current field under the excitation of the harmonic signal, and the coupling theory of the electrokinetic effect under the first-order approximation condition was derived. The dissipation equation of electrokinetic dissipation and viscous resistance dissipation and its solution were established by using Green\'s function method. The physical and mathematical models for the electrokinetic dissipation of reservoir rocks were constructed. The microscopic mechanism of the electrokinetic dissipation of reservoir rock were theoretically clarified. The influencing factors of the electrokinetic dissipation frequency of the reservoir rock were analyzed quantitatively. The results show that the electrokinetic effect transforms the fluid flow profile in the pores of the reservoir from parabolic to wavy; under low-frequency conditions, the apparent viscosity coefficient is greater that one and is basically unchanged. The apparent viscosity coefficient gradually approaches 1 as the frequency increases further. The viscous resistance dissipation is two orders of magnitude higher than the electrokinetic effect dissipation. When the concentration of the electrolyte exceeds 0.1mol/L, the electrokinetic dissipation can be neglected, while for the electrolyte solution (<10-2M) in low concentration, the electrokinetic dissipation is very significant and cannot be ignored.

On a silver platter

on a silver platter

Mass, momentum, and energy transfer in supersonic aerosol deposition processes

Aerosol deposition (AD) can lead to the formation of dense coatings via deposition of particles from a gas flow; in AD the aerosol is passed through a converging-diverging nozzle, facilitating inertial particle impaction on a desired substrate at supersonic particle velocities. Unique from thermal spray methods, AD can be applied near room temperature and unique from cold spray, in AD the aerosol is typically at atmospheric pressure upstream of the nozzle. Though AD has been successfully demonstrated previously, a number of aspects related to particle motion in AD systems remain poorly understood. In this work, we simulated compressible flow field profiles and particle trajectories for typical AD working conditions for a slit type converging-diverging nozzle with a planar substrate. In examining the fluid flow profile, we show that the velocity and pressure profiles, as well as the shock structure are sensitive to the upstream and downstream operating pressures of the nozzle. These ultimately affect particle impaction speed. Importantly, in AD, the particle drag regime is dynamic; both particle Knudsen numbers and Mach numbers can vary by orders of magnitude. To aid particle trajectory simulations, we trained a neural network to predict the drag force on the particles based on existing experimental data, theoretical limits, and new direct simulation Monte Carlo (DMSC) results. The neural network based drag law, which depends upon both Mach and Knudsen numbers, shows better agreement with the DSMC simulation data than pre-existing correlations. With it, particle trajectory simulation results reveal that for a given particle density, there exists an optimal particle diameter to maximize particle impaction speed. We also find that in AD particles undergo size dependent inertial focusing, i.e. there is a particular particle diameter where the particle deposition linewidth is minimized. Particles smaller than this diameter are underfocused, and particles larger than this are overfocused, and hence have larger deposition linewidths in both cases. Using trajectory simulations, we additionally developed a framework that can be used to evaluate the position-dependent mass, momentum and kinetic energy fluxes to the deposition substrate for any aerosol size distribution function upstream of the nozzle. It is shown for typical aerosol concentrations achievable in the laboratory, the kinetic energy flux can approach a magnitude normally observed in convective heat transfer with phase change, hence translational kinetic energy to thermal energy transfer in AD is likely a key contributor to the formation of dense coatings.

WALL EFFECT OF A PACKED BED WITH PELLET PARTICLES

Fluid flow profile is a dominate role in the performance of packed bed reactor. In small ratio of column-to-particle diameter, velocity pattern is strongly affected by voidage distribution, which depends on radial coordinate, flow rate and bed height. In this study, effects of voidage distribution to gas velocity profile in a packed bed with pellet particles was empirically investigated. Uniformity of local velocity at the top of the bed was clearly observed with decreasing of bed height and flow rate. For 400 mm of bed height, the measured velocities are a well fitting to Fahien and Stankovich model for any expected flow rate.

Experimental investigation of different fluid flow profiles in a rotary multi-bed active magnetic regenerator device

A rotary multi-bed active magnetic regenerator (AMR) device was modified to allow testing different fluid flow waveforms, with different blow fractions (i.e., the fraction of the AMR cycle when there is fluid flow in the regenerators). The different values of blow fraction were generated using different cam rings that actuate the poppet valves at the inlet and outlet of the regenerators, controlling how long the valves stay open and the number of valves open at the same time. Results showed that smaller blow fractions yield higher values of temperature span for fixed flow rate and cooling capacity, but lower values of coefficient of performance for the same conditions. An analysis of the shaft and pumping powers showed that shorter blow fractions cause higher pressure drop and higher torque oscillations and mechanical vibrations. The highest value of second-law efficiency of 19.1% was obtained for the largest blow fraction tested (80%). Designs for magnetic refrigerators where the fluid flow waveform can change during operation are also discussed in this paper.

Electroosmotic Flow in Free Liquid Films: Understanding Flow in Foam Plateau Borders

Liquid flow in foams mostly proceeds through Plateau borders where liquid content is the highest. A sufficiently thick (~180 µm) free liquid film is a reasonable model for understanding of electrokinetic phenomena in foam Plateau borders. For this purpose, a flow cell with a suspended free liquid film has been designed for measurement of electrokinetic flow under an imposed electric potential difference. The free liquid film was stabilised by either anionic (sodium lauryl sulfate (NaDS)) or cationic (trimethyl(tetradecyl) ammonium bromide (TTAB)) surfactants. Fluid flow profiles in a stabilised free liquid film were measured by micron-resolution particle image velocimetry (µ-PIV) combined with a confocal laser scanning microscopy (CLSM) setup. Numerical simulations of electroosmotic flow in the same system were performed using the Finite Element Method. The computational geometry was generated by CLSM. A reasonably good agreement was found between the computed and experimentally measured velocity profiles. The features of the flow profiles and the velocity magnitude were mainly determined by the type of surfactant used. Irrespective of the surfactants used, electroosmotic flow dominated in the midfilm region, where the film is thinnest, while backflow due to pressure build-up developed near the glass rods, where the film is thickest.