Numerical Analysis Of Flow Research Articles

Experimental and Numerical Analysis of Incompressible Flow over an Iced Airfoil

Determining the aerodynamic characteristics of iced airfoil is an important step in aircraft design. The goal of this work is to study experimentally and numerically an iced airfoil to assess the aerodynamic penalties associated with presence of ice on the airfoil surface. Three iced shapes were tested on NACA 0012 straight wing at zero and non-zero angles of attack, at Reynolds No. equal to (3.36*105). The 2-D steady state continuity and momentum equations have been solved utilizing finite volume method to analyze the turbulent flow over a clean and iced airfoil. The results show that the ice shapes affected the aerodynamic characteristics due to the change in airfoil shape. The experimental results show that the horn iced airfoil consumes more power than the other shapes of ice, its value was (44.4W). The horn iced shape has the worst effect on the airfoil than the other shapes. The present results are compared with previously reported results; it is found there is a very good agreement between them. A comparison between the experimental and computational results of the presented work were pursing the same behavior.

Numerical and statistical analysis of hydromagnetic couple-stress hybrid nanofluid flow in a channel induced due to stretching of a wall

In this research paper, the authors wish to examine the effects of couple stress on hybrid nanofluid considering magnetohydrodynamic three-dimensional transient flow between two parallel plates. Stretching of the lower plate causes fluid flow in the channel. The fluid flow model is shown in mathematical form using a set of coupled nonlinear partial differential equations, which are then translated into coupled nonlinear ordinary differential equations using the proper transformation. The authors used the spectral quasi linearization method (SQLM), an effective numerical technique, to solve the updated equations and study the effects of various flow parameters on fluid temperature and velocity. The Nusselt number and skin friction coefficients were also investigated from an engineering standpoint. The generated solutions are verified using the residual analysis. Statistical analysis is performed on the skin-friction coefficients and the Nusselt number using quadratic regression models.

Enhanced heat transfer in a microchannel with pseudo-roughness induced by Onsager-Wien effect

A three-dimensional numerical analysis of flow and conjugate heat transfer in a microchannel in the presence of the electric-field-induced Onsager–Wien effect is performed. A novel design is proposed to induce a pseudo-roughness effect in the microchannel and thereby increasing the heat transfer. A series of thin plate electrode pairs are flushed along the bottom wall of the microchannel. The electric-field-enhanced dissociation of ions induces the Onsager–Wien effect, and generates small flow vortices near the bottom wall of the channel. These flow vortices with sharp local velocity gradients effectively disrupt the viscous and thermal boundary layers, and thus, introduce a pseudo-roughness effect. This disruption of the boundary layers improves the heat transfer between the channel wall and the working fluid. The thermal and hydraulic performances in the microchannel are quantified as a function of the flow Reynolds number Re and electric Reynolds number ReEL. In general, the performance factor PF is higher when the flow and electric Reynolds numbers are higher. However, the associated pressure drop penalty reduces the PFPF<1 in viscous-effect-dominated flows at Re=250. By contrast, the Onsager–Wien effect increases the PF to a maximum value of 1.26 in inertia-dominated flows at Re=1000 and ReEL=15. A significant heat transfer enhancement is realized, even at a low applied voltage of ∼1 kV. The results of this study indicate that the pseudo-roughness produced by the electric-field-induced Onsager–Wien effect can substantially enhance the heat transfer in a microchannel with a trivial amount of additional power consumption. Results presented in this study will serve as a benchmark to design microchannels with enhanced heat transfer by using active vortex generation based on Onsager-Wien effect.

Efekty lepkosprężyste w warunkach nawadniania kolektora szczelinowo-porowego cieczą wodno-polimerową

The work is devoted to the numerical simulation of the flow of simple and viscoelastic (polymer solution) fluids through a fracture by using polymer solutions for enhanced oil recovery from a reservoir. Polymer solutions have viscoelastic properties. Therefore, when polymer solution flows through the slot, we use the well-known Maxwell’s fluid model with the Jaumann derivative to evaluate deformation characteristics of the flow (stream functions, distributions of the longitudinal velocity gradient and normal stress) resulting in the manifestation of abnormal (compared with the behaviour of the ordinary fluid) effects. The case of slow flow is considered. In this case, the inertial terms can be neglected, the velocities, stresses, and stream functions can be written as the decomposition by Weisenberg number, and we can assume that the Weissenberg number is less than one. The determined regularities of viscoelastic (polymer solution) liquid behaviour with longitudinal velocity gradient and the elastic deformations effects manifested in this case have a decisive meaning in understanding the mechanism of anomalously high oil recovery capacity of a reservoir by using water-polymer flooding of the fractured-porous reservoir. Understanding the nature of the effects of elastic deformations under the conditions of water-polymer flooding of the fractured-porous reservoir enables hydrodynamic calculations of the optimal flow of the polymer solution. One of the main issues that need to be solved when developing the technology for increasing oil recovery from formations using polymer solutions is to determine the optimal flow regime in the fractured-porous reservoir. The calculation results verify the ideas obtained from the experimental solution of this problem concerning the strain-stress state of polymer macromolecules (liquid elements) during polymer flow in the inlet area of the fracture in the oil reservoir and confirm the possibility of using numerical analysis of convergent polymer flow for calculating longitudinal velocity gradients in the inlet area of the fracture and can also serve as additional substantiation of the proposed earlier mechanism for increasing oil recovery from reservoirs by using polymer solutions.

Finite element analysis for electro-osmotic Erying-Powell fluid flow past a stretching sheet with an exponential heat source - an ANN approach

This paper gives the numerical analysis for an electro-osmotic Eyring-Powell fluid flow that is in two dimensions along a stretched sheet. The modified governing equations are resolved by the finite element technique. Graphs are used to display the various properties for several relevant factors on dimensionless velocity and temperature fields. The results are compared with previous findings in order to confirm the accuracy of the numerical solution. There appears to be a decrease in velocity when the magnetic parameter and Eckret number increase. This study has implications for fluidization, environmental pollutants, and agriculture. In this study, computational fluid dynamics (CFD) simulations and an artificial neural network (ANN) model are both employed.

Numerical Analysis for Argon Arc Plasma Jet Flow by Three-Dimensional Thermal Lattice Boltzmann Model

Numerical Analysis for Argon Arc Plasma Jet Flow by Three-Dimensional Thermal Lattice Boltzmann Model

The effect of the triangular rib usage in the plate fin heat sinks on the pressure drop, base plate temperature, and entropy generation

Improving the thermal efficiency in plate fin heat sinks (PFHS) results in a reduction in the weight, volume and cost of the heat sink. This ensures long life and reliable operation of the cooled equipment. In this study, the performances of triangular ribbed PFHSs, which are formed by placing a staggered array of triangular ribs between plate fins, were numerically investigated. Pressure drop, base plate temperature and entropy generation are used for performance comparisons. Numerical heat transfer and flow analysis were performed in three-dimensional models with the help of Ansys Fluent program, which uses the finite volume method with incompressible, turbulent flow and conjugate heat transfer assumptions. The design parameters were determined as inlet velocity between 3 m/s and 9 m/s, number of plate fins 9, 12 and 15, plate fin heights 10 mm and 30 mm, triangular rib heights 0.1 mm and 0.3 mm. As a result, the heat sink base temperature decreases with the increase of velocity, fin height, number of plate fins and triangular rib height, lower pressure drop values were obtained in the case of Hrib=0.1 mm compared to the unribbed case. If the design with the least entropy production is desired as the optimum design, there is a %10.64 increase in the base temperature and a significant decrease in the pressure drop (220.88 Pa to 7.512 Pa). In this case, since the fin length is H=30 mm, the volume and weight of the heat sink also increase.

Numerical analysis of rarefied hypersonic flows over inclined cavities

A comprehensive numerical analysis is conducted to investigate rarefied hypersonic flows over two-dimensional (2-D) and three-dimensional (3-D) non-rectangular cavities with inclined front or rear walls using the direct simulation Monte Carlo (DSMC) method. The objective is to give a contribution to the understanding of the effects of inclined front or rear walls on flow features and aerodynamic surface quantities. The 3-D or finite-span effects are also analysed in depth. Results show that inclining the front wall of the cavity has a negligible effect on gas flows in the rear part of the cavity, and consequently does not affect surface pressures on and heat fluxes to both the cavity floor and the rear wall. This is because high-speed gases enter the cavity via the top of the rear wall, which is exactly the dominant drive force for gas flows in the rear portion of the cavity. Inclining the front wall does not alter this drive force, so it does not influence gas flows there. However, inclining the rear wall not only strongly influences the flows close to the rear wall, but also has a profound influence on the flows in the front portion of the cavity. Specifically, it can substantially enhance the flow expansion in the front portion of the cavity, make the front vortex shorter and moves the front vortex upward and leftward. The 3-D or finite-span effects play an important role in the flow features and surface quantities of rectangular, inclined-front, and inclined-rear cavities. The finite-span effects exhibit as the 3-D relieving effects, which prevent the external stream from penetrating deeper into the cavity. This consequently lessens the momentum and energy that are transferred into the cavity and brings about a significant decrease in the pressure on and heat flux to the cavity floor. The results in the work can be applied to the accurate prediction of the pressure and heating loads of the thermal-protection tiles of hypersonic vehicles.

Numerical Simulation of Characterization of Hydraulic Jump Over an Obstacle in an Open Channel Flow

Hydraulic jumps produce so much turbulence that hydraulic energy is effectively converted to heat. The speed, form, and volume of obstructions in an open channel have a considerable impact on the characteristics of a fluid stream. To create a hydraulic leap, a numerical analysis of water flow was done for a two-dimensional open channel over three different forms of obstruction, each with three volumes. Because of the impact of the air, it is possible to think of the emulsion of air and water as a compressible fluid with a vacancy percentage (a second fluid). The volume of fluid model (VOF), linked with the turbulent model, has been used to study each type of obstruction. The second-order upwind technique incorrectly solves the two-dimensional Reynolds-averaged Navier-Stokes equations. The numerical technique is implemented using the straightforward approach that was devised using control volumes. A wide range of Reynolds numbers (Re), corresponding to various flow patterns, were calculated for. The results demonstrate that when the Reynolds number increases, the effect of the gas phases on the liquid phases increases. The boundary layer thickness in the upstream zone from the obstacle decreases with increasing Re, whereas downstream from the obstruction, the height of the recirculation zone rises. Profiles of the empty fraction reveal two zones that are consistent with a diffusion equation. This article observed an inversion of the pressure gradient in the pressure field, which caused the boundary layer to separate; this is known as the "back flow phenomenon." The results of the current work have been verified by comparison with those of related research projects, and the comparison has shown a commendable degree of agreement. Additionally, pressure in various areas of the obstacle and velocity were similar.

Advanced numerical analysis of convective rarefied flows in microchannels: Studying the impact of multiple obstacle arrangements through LBM modeling

The investigation of fluid flow and forced convective heat transfer in microchannels with square barriers is the focus of this study. The positioning of obstacles was varied in three cases: at the top wall, bottom wall, and symmetrically distributed on both sides of the microchannel wall. The thermal Lattice Boltzmann Method in conjunction with the Double Distribution Function and Bhatnagar–Gross–Krook approach was used for simulation through computer code in Python. Slip velocity and temperature jump were considered in the boundary conditions for the walls of the microchannel and obstacles. The results demonstrate that the rarefaction effect, placement of barriers, and choice of square obstacles significantly impact fluid flow and heat transfer. An increase in Knudsen numbers (Kn) leads to a decrease in temperature and velocity. The presence of obstructions on both sides of the microchannel walls reduces the fluid’s velocity and cools the fluid at the microchannel’s exit. The third case, with obstacles on both sides, presents a practical approach for reducing the fluid’s temperature at the exit, resulting in the lowest level of skin friction (Cf) and a reduction in the Nusselt number (Nu). The proposed configurations can be utilized to enhance the geometry of microchannels and for cooling purposes in small-scale devices and systems with miniature mechanical and electrical components. The study’s findings suggest that the placement of obstacles at the bottom or on both sides, depending on the need for best cooling on both sides or only at the top to reduce material consumption, can achieve low temperature at the exit of a rectangular microchannel.

Magnetohydrodynamics Williamson Nanofluid Flow over an Exponentially Stretching Surface with a Chemical Reaction and Thermal Radiation

Presented in this current study is the numerical analysis of magnetohydrodynamics Williamson nanofluid flow over an exponentially stretching surface. The most important aspect of the investigation is that the effects of the magnetic field, chemical reaction and thermal radiation in the fluid flow are taken into account. The partial differential equations governing the present Williamson nanofluid flow problem were observed to be highly nonlinear and coupled. Suitable similarity transformations were used to transmute the coupled system of nonlinear partial differential equations governing the fluid flow into a linear system. The linear system was solved numerically using the spectral quasi-linearization method. The MATLAB bvp4c numerical technique and a comparison with existing results for the skin friction coefficient were used to confirm the appropriateness of the method in solving the current problem. The influence of some pertinent physical parameters on the fluid’s velocity, temperature and concentration profiles were displayed graphically. The effects of all the physical parameters on the skin friction coefficient, Nusselt number and Sherwood number were portrayed in a tabular form. It was noted that enhancing the thermal radiation parameter reduces the fluid’s temperature, Nusselt number and the skin friction coefficient, while the Sherwood number is improved.

The turbulence models review for aerodynamic, thermal and structural problems in jet engine turbines.

Analysis of the aerodynamic, thermal and aeroelasticity (including vibration) processes in gas turbine stage is principal for a design and creating turbines and jet engine integrally. In this article was the review showed for the basic problems, which are solved by engineers for the gas turbines design and take a numerical analysis of flow. The special aspects was showed which appearance in the vanes and blades channels for turbojets turbine. The fundamental structure of the boundary layer and vortices on the low and high pressure faces of blade was demonstrated also. A target of this article is a review of current classification of the turbulence models and a review of best practices which include this turbulence models usage for the scientific and engineering problems. Authors describe the basic classification and the small specification with the application domain for each turbulence model (for aircraft). The general equation was demonstrated for URANS with a description of the Spalart – Allmaras, k-ε, k-ω, Menter’s SST, SST Gamma-ReTheta turbulence models. For LES, DES and DNS was showed description with the features only.The article contains the publications analysis with the turbulence models for three basic problems: aerodynamics, cooling problem (heat exchange) and structural problems (aeroelasticity, vibration resistance, stress limits, fatigue resistance). The turbulence models with high frequency of usage was presented in the current review moreover review contains the reasons of the models usage, the models hypothesizes, the changes of models (if it exists) and the solution accuracy. The solution accuracy was analyzed between different models of turbulence and between softwares for CFD. All arguments and conclusions was based on the different publications summary which was used for the review creating, and on data (numerical and graphical results) which was included in the researched CFD-articles. A little bit of the comparative analysis between CFD-softwares was created with the software’s user guides, the public reports and articles which includes the numerical researches in this problem. All results of the current review was presented in the general conclusions in end of article.

Compositional numerical analysis of multiphase flow of crude oil in porous media under non-isothermal conditions

Abstract The present work details the development of a compositional model to replicate the heavy hydrocarbon flow in porous reservoir systems under non-isothermal conditions. The mathematical model considers mass and energy conservation equations describing the reactive of natural variables distributed in a multiphase hydrocarbon system. Such natural variable based compositional models better suit fully implicit numerical schemes with inexpensive Jacobian matrix computations. Further, the model accommodates a switch of primary variables for the disappearance and reappearance of a phase. The resulting nonlinear conservation equations are numerically discretized using a block-centered finite-difference scheme and solved with a quasi-Newton based implicit iterative solver. The present model is validated with the thermal profiles presented in the literature for the multiphase flow during the combustion of heavy crude oil in petroleum reservoir system with performance coefficient (R 2), mean absolute error (MBE), and maximum absolute percentage error (MAPE) of about 0.954, 0.37, and 0.01 respectively. The developed compositional model projected 26 and 72 % of light and heavy oil recoveries respectively in about 160 days with a maximum or peak temperature of about 798 K. Further, the thermal and production profiles projected by the sensitivity analysis on various operating parameters are presented. It is noteworthy that the present works aid in providing an economical numerical based tool in evaluating the flow and transport during underground or in-situ combustion process for efficient energy exploration.

Investigation of the complex 3D flow structure within a selective catalytic reduction (SCR) reactor of a coal-fired power plant

A selective catalytic reduction (SCR) reactor is commonly used to remove nitrogen oxides (NOx) from coal-fired boilers. Uniformity of the flow passing through the catalyst layer is important for increasing denitrification (de-NOx) efficiency. In order to examine flow uniformity, this study conducted an experimental and numerical analysis of the complex internal flow within a realistic SCR model. Magnetic resonance velocimetry (MRV) was utilized to obtain non-invasive measurements of three-dimensional three-component average velocity and validate Reynolds-averaged Navier-Stokes (RANS) numerical simulations. The computational results showed similar overall flow structure compared with the MRV results. Parameters representing flow quality such as relative standard deviation (RSD) and recirculation zone strength (RZS) were calculated by integrating the flow field. These parameters have the largest value after the straightener area and decrease towards the catalyst reactor, and are not significantly affected by Reynolds number upstream of the catalyst layer. The recirculation zone size was analyzed using spanwise uniformity and skewness indicators. As the recirculation zone induces biased flow, the non-reacted NOx concentration was more prominent in the outlet zone opposite of the recirculating area in the corresponding actual on-site SCR reactor. Based on this finding, a meaningful correlation between flow maldistribution and de-NOx reaction could be deduced.

Numerical analysis of Magnetohydrodynamic convection heat flow in an enclosure

This article investigates the modeling and numerical simulation of Magnetohydrodynamic (MHD) buoyancy-driven convection flow in a differentially heated, square enclosure. Left vertical side is given a high temperature and the right vertical side is sustained at a low temperature. Horizontal sides of the enclosure are insulated. A constant magnetic field is presumed horizontally. Findings of the governing differential equations are explored numerically considering the impact of Magneto-hydrodynamic (MHD). Problem is deciphered by Galerkin finite element approach in COMSOL Multiphysics. Numerical solutions are computed for different values of Rayleigh number ranging 103≤Ra≤107 and Hartmann number ranging 0≤Ha≤40. Rate of heat that passes from the heated side is affected by increasing Rayleigh and Hartmann numbers. Comportment of MHD free convection heat flow from transient to steady state is numerically examined for a period of 0 to 1 s. The numerical solutions are discussed in respect of streamlines, iso-contours, and isotherms. In addition, physical quantities such as velocity and Nusselt number are studied. It is seen that with increasing values of Rayleigh number there is increase in local Nusselt number distribution on heated side of the cavity. Velocity distribution in the flow domain decreases in variations with increasing Hartmann number.

Numerical and correlation analysis for flow of micropolar fluid induced by two rotating disks

Numerical and correlation analysis for flow of micropolar fluid induced by two rotating disks

Viscoelectric effect analysis in an electroosmotic flow with microchannel wall slip

In the present work, we developed a numerical analysis for an electroosmotic flow circulating in a rectangular microchannel considering electrolyte viscosity as a function of the induced electric field; which is also reflected in the slip condition imposed on the system walls, since the slip length is a function of the fluid viscosity. It should be clarified this is an entirely hydrodynamic problem, and for this reason there are no induced pressure gradients, because we are in the presence of a purely electroosmotic flow, where the fluid motion is due only to electrokinetic forces. Based on these comments, the problem is centered on high induced potentials, enabling viscoelectric effect analysis in the electroosmotic flow, which leads to significant increases in velocity and volumetric flow profiles compared to the case where the viscosity is a constant and there is no slip condition. Due to analytical analysis limitations, we implemented a dimensionless equation scheme defined by the continuity equation, the momentum equations in the x and y direction, the Poisson-Boltzmann equation, and the charge conservation equation to obtain the velocity and volumetric flow rate profiles mentioned above. This model is described in its variational form in order to implement the finite element technique using free software, FreeFem++. The results obtained show how the viscoelectric effect is relevant when working with high induced potentials; that is, for values of , when the dimensionless viscoelectric parameter increases, there is a significant decrease in the velocity profiles u, a situation that is not observed when , where there are low induced potentials, and for this reason, as the dimensionless parameter increases, the velocity profiles remain constant. This condition is preserved for different values of the slip length .

A Numerical Stability Analysis of Mean Curvature Flow of Noncompact Hypersurfaces with Type-II Curvature Blowup: II

In previous work, we have presented evidence from numerical simulations that the Type-II singularities of mean curvature flow (MCF) of rotationally symmetric, complete, noncompact embedded hypersurfaces, constructed by the second and the fourth authors of this paper, are stable. In this work, we again use numerical simulations to show that MCF subject to initial perturbations that are not rotationally symmetric behaves asymptotically like it does for rotationally symmetric perturbations. In particular, if we impose sinusoidal angular dependence on the initial embeddings, we find that for perturbations near the tip, evolutions by MCF asymptotically lose their angular dependence—becoming round—and develop Type-II bowl soliton singularities. As well, if we impose sinusoidal angular dependence on the initial embeddings for perturbations sufficiently far from the tip, the angular dependence again disappears as Type-I neckpinch singularities develop. The numerical analysis carried out in this paper is an adaptation of the “overlap” method introduced in our previous work and permits angular dependence.

Curing Hydrodynamic Instability During Balanced Plug Cementing

Summary It is shown how the flow from pumping cement through an open-ended pipe very quickly changes direction and the cement flows upward. This rapid change in flow direction indicates that a diverter tool, which leads the cement slurry perpendicularly out of a closed-ended pipe, does not have any function. The placement of a balanced plug is feasible. However, a high-density fluid above a lighter fluid is not stable. The phenomenon is known as Rayleigh-Taylor instability. In principle, to be reasonably stable, the interface must be horizontal. The longer the interface is, the more unstable is this case. Thus, it is difficult, or sometimes impossible, to create a stable situation in a deviated well section, especially if the well section diameter is large. Observations show that it is possible to modify density differences, thickening time, and viscosity differences such that the success rate can be between 40% and 60%. Using a floatable cement foundation tool, this success rate increased to more than 95% in North Sea applications. The use of such a tool is described, and its performance is justified by a numerical analysis of cement flow.

Thermal boundary layer depletion in minichannels by electrohydrodynamic conduction pumping

The article presents a numerical analysis of two-dimensional laminar flow and heat transfer in a minichannel with flat plate electrode pairs periodically flushed to the bottom wall. The two-way coupled governing equations of flow, heat transfer, electric potential and charge conservation are solved using the opensource finite-volume framework of OpenFOAM. Two cases of the minichannel at completely horizontal (case A) and 90° bent (case B) configurations are considered. The inlet laminar flow with Reynolds number varying from 10 to 1000 has been taken into account. The applied electric potential is varied in three steps 0, 0.5 and 1 kV. Electrohydrodynamic (EHD) conduction pumping due to the residual conductivity of the working fluid and the electric-field enhanced dissociation of free charges generate vortices in the proximity of electrodes. The flow and thermal performance of the minichannel in the presence of EHD conduction induced vortices are quantified in terms of pressure drop, Nusselt number and a performance factor (which is a combined function of pressure drop and Nusselt number). The vortices generated by EHD conduction pumping phenomenon deplete the thermal boundary layer, aid mixing and enhance the heat transfer. The mean and local Nusselt numbers are notably increased with only a minimal raise in pressure drop. In both the configurations of the minichannel, the performance factor is greater than 1 for the entire parameter space considered in this study. However, the thermal boundary layer depletion and heat transfer enhancement is prominent at low Reynolds number flows. The maximum drop in performance factor from case A to case B is only 18.5%. Results of this study indicate that EHD conduction pumping is a potential technique to enhance heat transfer in minichannels with minimum additional power consumption.