×
The submission system is temporarily under maintenance. Please send your manuscripts to
Go to Editorial ManagerElectromagnetic flowmeters measure flow rate of the electrically conducting liquids. Its operation is based on Faraday's principle of induction. In many situations the pipe may be partially filled where in this case the analysis of the flowmeter equation is widely altered and the numerical solution may diverge. In this paper we have established a new numerical formulation, based on finite difference method, which adaptively refines the mesh until the desired solution converges to a certain accuracy. The representation of the flowmeter equations in the polar axis of the solution domain (cylindrical cut from it the empty portion) can result in the singularities in the solution. To avoid these singularities, the grids are shifted one half mesh width from the polar axis. The number of iterations that gives convergence is appreciably reduced via this numerical technique. The build algorithm of the adaptive numerical solution led us to determine, for each liquid level, the optimum angular position of the electrodes that gives maximum accuracy i.e. minimum sensitivity to the changes in the velocity profile of the liquid to be metered.
The conjugate natural convection-conduction heat transfer in a domain composed of nanofluids filled porous cavity heated by a vertical solid wall is studied under steady-state conditions. The vertical left wall of the solid is kept isothermal at hot temperature Th. The vertical right wall of the solid is in contact with the nanofluid saturated porous medium contained in the cavity. The right vertical wall of the cavity is kept isothermally at the lower temperature Tc. The upper and lower horizontal walls are kept adiabatic. The governing equations of the heat transfer in the solid wall and heat and nanofluid flow, based on the Darcy model, in the nanofluid-saturated porous medium together with the derived relation of the interface temperature are solved numerically using the over-successive relaxation finite- difference method. A temperature independent nanofluids properties model is adopted. The investigated parameters are the nanoparticles volume fraction (0-0.2), Rayleigh number Ra (10-1000), solid wall to base-fluid saturated porous medium thermal conductivity ratio kwf (0.1, 1, 10), and the solid wall thickness D (0.05-0.5). The results are presented in the conventional form; contours of streamlines and isotherms and the average Nusselt number. At a very low Rayleigh number Ra=10, an enhancement in heat transfer within the porous cavity with is observed. Otherwise, the heat transfer may be unchanged or deteriorated with depending on the wall thickness D and the conductivity ratio kwf.
Electromagnetic flowmeters measure flow rate of the electrically conducting liquids. Its operation is based on Faraday's principle of induction. In many situations the pipe may be partially filled where in this case the analysis of the flowmeter equation is widely altered and the numerical solution may diverge. In this paper we have established a new numerical formulation, based on finite difference method, which adaptively refines the mesh until the desired solution converges to a certain accuracy. The representation of the flowmeter equations in the polar axis of the solution domain (cylindrical cut from it the empty portion) can result in the singularities in the solution. To avoid these singularities, the grids are shifted one half mesh width from the polar axis. The number of iterations that gives convergence is appreciably reduced via this numerical technique. The build algorithm of the adaptive numerical solution led us to determine, for each liquid level, the optimum angular position of the electrodes that gives maximum accuracy i.e. minimum sensitivity to the changes in the velocity profile of the liquid to be metered.
For shorter landing and take-off path in airports, the aircrafts should reduce their speed with keeping high lifting force. This paper is to identify solutions to increase the lift force of the wing significantly under several flight scenarios (such as takeoff and landing) using leading-edge slats and their relationship with the dynamic parameters of the aerodynamic wing. The study is performed by the use of ABAQUS 2016 software. The problem is solved for turbulent flow and 2-dimensional composite wing at constant Reynolds’s number of (6.49 × 10 5 ) and constant boundary conditions. Various depths have been used for the auxiliary airfoil at constant width and gap. All stresses at the wing base were obtained. The pressure distribution on the airfoil surface was determined, air velocity distribution was tracked over the surface, lift and drag forces and their coefficients were computed. The results show that the highest value of the lift coefficient is 0.489 at the depth (-3 %) of the wing chord, it decreases when the depth of the slat becomes zero %, and the rise returns with increasing depth to (4 %), but it does not reach the maximum value, while the highest drag coefficient was (1.89) at depth (4 %) of the wing chord. The maximum value of Von Mises stress was found at depth of 4 % with value of 1.605 × 10 5 Pa.
Electromagnetic flowmeters measure flow rate of the electrically conducting liquids. Its operation is based on Faraday's principle of induction. In many situations the pipe may be partially filled where in this case the analysis of the flowmeter equation is widely altered and the numerical solution may diverge. In this paper we have established a new numerical formulation, based on finite difference method, which adaptively refines the mesh until the desired solution converges to a certain accuracy. The representation of the flowmeter equations in the polar axis of the solution domain (cylindrical cut from it the empty portion) can result in the singularities in the solution. To avoid these singularities, the grids are shifted one half mesh width from the polar axis. The number of iterations that gives convergence is appreciably reduced via this numerical technique. The build algorithm of the adaptive numerical solution led us to determine, for each liquid level, the optimum angular position of the electrodes that gives maximum accuracy i.e. minimum sensitivity to the changes in the velocity profile of the liquid to be metered.
The natural convection heat transfer from horizontal isothermal three cylindrical rods inside equilateral triangular enclosure has been studied numerically. The enclosure is filled with air, and the heated rods are located at equal distances (E) from triangle center. A finite element software package (FLEXPDE) is used in the present study to solve the set of non-linear equations governing the process. Solutions are obtained for aspect ratio D/H=1/6 and range of distance E=0.2-0.6 and Rayleigh (Ra) number changes from 103 to 106. The effect of Ra and E were examined. Results are presented by streamlines, isotherms and Nusselt number and it indicates that the Nusselt number is significantly increase with increasing both Ra and E. A comparison of the Nusselt number was made with that obtained by [7], and showed substantial improvement to about 65% in some cases.
Electromagnetic flowmeters measure flow rate of the electrically conducting liquids. Its operation is based on Faraday's principle of induction. In many situations the pipe may be partially filled where in this case the analysis of the flowmeter equation is widely altered and the numerical solution may diverge. In this paper we have established a new numerical formulation, based on finite difference method, which adaptively refines the mesh until the desired solution converges to a certain accuracy. The representation of the flowmeter equations in the polar axis of the solution domain (cylindrical cut from it the empty portion) can result in the singularities in the solution. To avoid these singularities, the grids are shifted one half mesh width from the polar axis. The number of iterations that gives convergence is appreciably reduced via this numerical technique. The build algorithm of the adaptive numerical solution led us to determine, for each liquid level, the optimum angular position of the electrodes that gives maximum accuracy i.e. minimum sensitivity to the changes in the velocity profile of the liquid to be metered.
This numerical study aims to enhance the heat transfer efficiency by dissipating the heat Emitted from electronic processors. A jet impingement technique is utilized with porous layer covering a metal fin as a heat sink. Forced convection and normal convection (due to the buoyancy effect) are taken into consideration. The two equations model (Local Thermal Non-Equilibrium LTNE) employed to describe the energy equations of the two phases of the porous surface. Finite Element Method (FEM) used to discretize these equations to obtain the numerical solution. To make this study closest to the reality, constant heat flux boundary condition is applied underneath the metallic heat sink. The geometry comprises of three domains: Free flow channel, Porous layer and Metal fined heat sink. In order to simulate the heat transfer, isotherms; streamlines and Nusselt number have been considered. Investigation has been done by inspecting the effects of the pertinent non- dimensional parameters such as: Reynolds number ( Re = 100-900), Darcy number ( Da = 10 -1 -10 -6 ), Richardson number ( Ri = 0.1-100) and Porosity ( ε = 0.85-0.95). The results show that increasing Re and decreasing ε lead to enhance Nusselt number. Richardson number below 100 has no significant effects on Nu . At Re above 400, Nusselt number proportional with Darcy number. The enhancement of Nusselt number is found to be 250 % by increasing Re from 100 to 900, 290 % by decreasing ε from 0.95 to 0.85 and about 13 % by increasing Darcy number from 10 -6 to 10 -1 .
Electromagnetic flowmeters measure flow rate of the electrically conducting liquids. Its operation is based on Faraday's principle of induction. In many situations the pipe may be partially filled where in this case the analysis of the flowmeter equation is widely altered and the numerical solution may diverge. In this paper we have established a new numerical formulation, based on finite difference method, which adaptively refines the mesh until the desired solution converges to a certain accuracy. The representation of the flowmeter equations in the polar axis of the solution domain (cylindrical cut from it the empty portion) can result in the singularities in the solution. To avoid these singularities, the grids are shifted one half mesh width from the polar axis. The number of iterations that gives convergence is appreciably reduced via this numerical technique. The build algorithm of the adaptive numerical solution led us to determine, for each liquid level, the optimum angular position of the electrodes that gives maximum accuracy i.e. minimum sensitivity to the changes in the velocity profile of the liquid to be metered.
The weight function prescribing the sensitivity of the electromagnetic flowmeter (EM}') to the changes in the velocity profiles must be as much as possible uniformly distributed through the measuring volume. The most commonly used criterion of the weight function distribution is a statistical quantity ( e criterion) which deals with only the axial component of the weight vector. In the present work, attempt 10 introduces a more revealing and accurate criterion to the EMF performance was studied. The curl of the weight function vector over the measuring volume has been considered and formulated (and termed as e ) in such a mathematical expression that takes Into account the contributions of the three components of the weight vector regardless of the geometry of the cross-sectional area of the flow. In addition, a numerical solution of a previously defined criterion (ey) is presented here for the first time in order to compare the validity of the newly introduced criterion. The results showed that the present new criterion e is closely harmonious with the previously defined criteria 8 and Si.. in the conventional flow cases. The results and the configuration of the formula of the present criterion, which is independent of the flow cross-sectional led us to conclude that is more reliable and applicable than other existing criteria.
Electromagnetic flowmeters measure flow rate of the electrically conducting liquids. Its operation is based on Faraday's principle of induction. In many situations the pipe may be partially filled where in this case the analysis of the flowmeter equation is widely altered and the numerical solution may diverge. In this paper we have established a new numerical formulation, based on finite difference method, which adaptively refines the mesh until the desired solution converges to a certain accuracy. The representation of the flowmeter equations in the polar axis of the solution domain (cylindrical cut from it the empty portion) can result in the singularities in the solution. To avoid these singularities, the grids are shifted one half mesh width from the polar axis. The number of iterations that gives convergence is appreciably reduced via this numerical technique. The build algorithm of the adaptive numerical solution led us to determine, for each liquid level, the optimum angular position of the electrodes that gives maximum accuracy i.e. minimum sensitivity to the changes in the velocity profile of the liquid to be metered.
This experimental research depicts the role of coating hot surfaces by graphite and graphene on the process of heat dissipation from these hot surfaces. Three aluminum specimens have been prepared for test, one of theme is coated by graphite, another one by graphene a while the third is left free of coating for comparison purpose. Each specimen is tested separately in a home-made wind tunnel. A plate electrical heater is adhered on the bottom of the specimen to simulate the generated energy by a heat sink. A heat sink composed of high thermal conductivity was applied between the heater plate and the base plate of heat sink to reduce the contact resistance to heat flow. The experiments are conducted with four turbulent Reynolds number. The results reveal that the sample coated by graphene exhibits the best thermal dissipation while the uncoated specimen shows the worst thermal performance.
Electromagnetic flowmeters measure flow rate of the electrically conducting liquids. Its operation is based on Faraday's principle of induction. In many situations the pipe may be partially filled where in this case the analysis of the flowmeter equation is widely altered and the numerical solution may diverge. In this paper we have established a new numerical formulation, based on finite difference method, which adaptively refines the mesh until the desired solution converges to a certain accuracy. The representation of the flowmeter equations in the polar axis of the solution domain (cylindrical cut from it the empty portion) can result in the singularities in the solution. To avoid these singularities, the grids are shifted one half mesh width from the polar axis. The number of iterations that gives convergence is appreciably reduced via this numerical technique. The build algorithm of the adaptive numerical solution led us to determine, for each liquid level, the optimum angular position of the electrodes that gives maximum accuracy i.e. minimum sensitivity to the changes in the velocity profile of the liquid to be metered.
Gas flow measurements are pivotal in several medical applications. For instance, mechanical ventilators and respiratory monitoring applications need flowmeters with strict requirements. This study is concerned with a three-dimensional computational fluid dynamics (CFD) analysis. The CFD methodology was confirmed by analyzing the flow characteristics of flexible membrane with trapezoidal orifice plates. Variable area orifice meters (VAOMs) are increasingly being embraced in respiratory monitoring applications, employed in the context of mechanical ventilation within medical settings. Each system integrates a flexible orifice plate within the conduit. The simulations are conducted considering realistic deformations in structure through two-way fluid-structure interactions (FSI) using the Arbitrary-Lagrangian-Eulerian (ALE) approach. This research paper analyzes using the finite volume method (FVM). A thorough numerical simulation was performed for the turbulence models. The orifice's thickness and shape significantly influence pressure drop and deflection.
Electromagnetic flowmeters have proven their merit in· measuring the flow rate of conducting liquids in fully-filled pipes. In contrast with the most of the published works about the electromagnetic flowmetcr, the attentions were focused in this work into the use of these devices in partially-filled pipes. In this application these devices suffer from the problem of different outputs with different liquid level for the same flow rale. We studied whether the process of changing the distribution of the magnetic field through the measuring section improves lhe tlo,~rneter performance against this drawback or not. An adaptive numerical mesh was used in predicting the flow induced signal and its response to the liquid level. The induced signal was assumed to he picked up by a pair of point electrodes tested for different angular positions. The results showed that the performance of the electromagnetic flowmeter in partially-filled pipes could be appreciably improved by making the magnetic field progtessively decreases from top to the bottom of the flowmeter. When the lower magnet coil is excited by a current one-half lower than the upper coil together with two point electrodes placed at 22° below the flowmetcr horizontal centerline, the flowmeter performance offer more stable sensitivity.
Electromagnetic flowmeters measure flow rate of the electrically conducting liquids. Its operation is based on Faraday's principle of induction. In many situations the pipe may be partially filled where in this case the analysis of the flowmeter equation is widely altered and the numerical solution may diverge. In this paper we have established a new numerical formulation, based on finite difference method, which adaptively refines the mesh until the desired solution converges to a certain accuracy. The representation of the flowmeter equations in the polar axis of the solution domain (cylindrical cut from it the empty portion) can result in the singularities in the solution. To avoid these singularities, the grids are shifted one half mesh width from the polar axis. The number of iterations that gives convergence is appreciably reduced via this numerical technique. The build algorithm of the adaptive numerical solution led us to determine, for each liquid level, the optimum angular position of the electrodes that gives maximum accuracy i.e. minimum sensitivity to the changes in the velocity profile of the liquid to be metered.
A simulation of fluid-structure interaction (FSI) and combined convective heat exchange is accomplished in an open trapezoidal cavity-channel. A non-Newtonian (power law fluid) is inspected within the laminar region. The heat source is simulated by an isothermal hot cavity bottom wall, whereas all the rest solid walls are perfectly insulated. A deformable baffle is fixed at the top wall of the channel and its free end extends towards the open cavity. The location of the deformable baffle on the top wall is varied. The baffle position is investigated together with Richardson number ($Ri = 0.01-100$) and power law index ($n = 0.5-1.5$). The problem was solved using finite element method with Arbitrary Lagrangian-Eulerian (ALE) technique. The results are compared with the non-baffled channel. The study shows that the proposed baffled channel enhances the heat transfer notably.
Electromagnetic flowmeters measure flow rate of the electrically conducting liquids. Its operation is based on Faraday's principle of induction. In many situations the pipe may be partially filled where in this case the analysis of the flowmeter equation is widely altered and the numerical solution may diverge. In this paper we have established a new numerical formulation, based on finite difference method, which adaptively refines the mesh until the desired solution converges to a certain accuracy. The representation of the flowmeter equations in the polar axis of the solution domain (cylindrical cut from it the empty portion) can result in the singularities in the solution. To avoid these singularities, the grids are shifted one half mesh width from the polar axis. The number of iterations that gives convergence is appreciably reduced via this numerical technique. The build algorithm of the adaptive numerical solution led us to determine, for each liquid level, the optimum angular position of the electrodes that gives maximum accuracy i.e. minimum sensitivity to the changes in the velocity profile of the liquid to be metered.
The electronic equipment industry has developed rapidly in recent years. The amount of heat emitted from such equipment is seriously increased. Increasing the temperature of the electronic devices degrades their performance and as a final result their failure. Therefore, the requirements for an effective cooling system have become more important than ever. One of the most important methods of heat dissipation that the researchers focused on is the use of piezoelectric fans (PE). The current study reviews most of the developments that have taken place since its discovery nearly 40 years ago and focused on reducing power consumption. Most of the improvements and developments have been focused on obtaining optimal designs for these piezoelectric fans, which are used in different applications. This review clarifies the foundations and concepts of designing piezoelectric fans by comparing the data presented in previous studies. Furthermore, in the last ten years, numerical simulation has entered as an effective tool in predicting the optimal design of piezoelectric fans. The design of piezoelectric fans is in two forms, either single or multiple. The single fan system is used within a limited range of applications, as large cooling systems cannot be replaced by it. Therefore, the cooling system consisting of multiple piezoelectric fans is promising as a unique solution to effectively dissipate heat in electronic devices. The percentage of experimental studies is about 32 % while the studies of CFD is about 21 %, and the combined one is about 47 %.
Electromagnetic flowmeters measure flow rate of the electrically conducting liquids. Its operation is based on Faraday's principle of induction. In many situations the pipe may be partially filled where in this case the analysis of the flowmeter equation is widely altered and the numerical solution may diverge. In this paper we have established a new numerical formulation, based on finite difference method, which adaptively refines the mesh until the desired solution converges to a certain accuracy. The representation of the flowmeter equations in the polar axis of the solution domain (cylindrical cut from it the empty portion) can result in the singularities in the solution. To avoid these singularities, the grids are shifted one half mesh width from the polar axis. The number of iterations that gives convergence is appreciably reduced via this numerical technique. The build algorithm of the adaptive numerical solution led us to determine, for each liquid level, the optimum angular position of the electrodes that gives maximum accuracy i.e. minimum sensitivity to the changes in the velocity profile of the liquid to be metered.
Natural convection heat transfer in porous cavity with arc shape wall filled with nanofluid is studied numerically. The right arc shape wall of the cavity is heated at constant temperature (Th) while the left wall is kept cold at constant temperature (Tc), and the other horizontal walls are thermally insulated. The governing equations of the heat transfer and nanofluid flow are solved Flex PDE software. A temperature independent nanofluids properties models are adopted. The investigated parameters are the nanoparticles volume fraction Ø= (0-0.2), Rayleigh number Ra (10-1000) and arc center Ce (1-∞). The results are presented by contour of streamlines, isotherms and the average Nusselt number. The results have showed that the average Nusselt number decreases with increasing Ce and increases with increasing Ra and Ø.
Electromagnetic flowmeters measure flow rate of the electrically conducting liquids. Its operation is based on Faraday's principle of induction. In many situations the pipe may be partially filled where in this case the analysis of the flowmeter equation is widely altered and the numerical solution may diverge. In this paper we have established a new numerical formulation, based on finite difference method, which adaptively refines the mesh until the desired solution converges to a certain accuracy. The representation of the flowmeter equations in the polar axis of the solution domain (cylindrical cut from it the empty portion) can result in the singularities in the solution. To avoid these singularities, the grids are shifted one half mesh width from the polar axis. The number of iterations that gives convergence is appreciably reduced via this numerical technique. The build algorithm of the adaptive numerical solution led us to determine, for each liquid level, the optimum angular position of the electrodes that gives maximum accuracy i.e. minimum sensitivity to the changes in the velocity profile of the liquid to be metered.
Lithium-ion batteries' physical properties classify them as one of the most important sources of clean energy that overcome the need for fuel usage. The rated operating temperature and its uniformity are of the main demands of Lithium-ion batteries. In this survey, several types of studies have been reviewed with the aim of understanding the thermal management systems used to control the temperature of lithium-ion batteries and their uniformity in the battery pack. They are represented by active and passive systems, as well as the hybrid system, which integrates each of the two mentioned systems into a system to obtain the best thermal performance. Active cooling systems were classified due to the type pf coolant used to air and liquid system, meanwhile passive system classified to PCM and heat pipe system. The survey reveals that the air-cooling of lithium-ion battery pack is better than the use of liquids. About 74% of the reviewed works prefer the use of active strategies. The working temperature under normal conditions should be within -20 to 60 °C, meanwhile the optimum range is 15 to 35 °C. The maximum temperature difference between batteries in the pack is preferred to be 5 °C or less.
Electromagnetic flowmeters measure flow rate of the electrically conducting liquids. Its operation is based on Faraday's principle of induction. In many situations the pipe may be partially filled where in this case the analysis of the flowmeter equation is widely altered and the numerical solution may diverge. In this paper we have established a new numerical formulation, based on finite difference method, which adaptively refines the mesh until the desired solution converges to a certain accuracy. The representation of the flowmeter equations in the polar axis of the solution domain (cylindrical cut from it the empty portion) can result in the singularities in the solution. To avoid these singularities, the grids are shifted one half mesh width from the polar axis. The number of iterations that gives convergence is appreciably reduced via this numerical technique. The build algorithm of the adaptive numerical solution led us to determine, for each liquid level, the optimum angular position of the electrodes that gives maximum accuracy i.e. minimum sensitivity to the changes in the velocity profile of the liquid to be metered.
The present numerical and experimental work investigates the performance of electromagnetic flowmeter (EMF) for measuring the flow rate of annular flow. Adaptive finite difference technique is used for the numerical calculations and the experimental work is done by making some modification on an existing electromagnetic flowmeter and its testing rig. The performance of the modified EMF is evaluated using two criteria namely, the flowmeter sensitivity S and the conventional weight function non uniformity ε. These two criteria were checked against two parameters; thickness of flowing water (δ) and the electrodes angular position (θe). Experimentally, three different water thickness (δ/Ro = 0.216, 0.373, 0.218) and three electrode position (θe=0o, 11.25o, 45o) were studied. The theoretical and experimental results have showed that these devices work properly in the annular flow case, where the most suitable electrode position in the annular flow was found to be in the conventional position (θe =0o).
Electromagnetic flowmeters measure flow rate of the electrically conducting liquids. Its operation is based on Faraday's principle of induction. In many situations the pipe may be partially filled where in this case the analysis of the flowmeter equation is widely altered and the numerical solution may diverge. In this paper we have established a new numerical formulation, based on finite difference method, which adaptively refines the mesh until the desired solution converges to a certain accuracy. The representation of the flowmeter equations in the polar axis of the solution domain (cylindrical cut from it the empty portion) can result in the singularities in the solution. To avoid these singularities, the grids are shifted one half mesh width from the polar axis. The number of iterations that gives convergence is appreciably reduced via this numerical technique. The build algorithm of the adaptive numerical solution led us to determine, for each liquid level, the optimum angular position of the electrodes that gives maximum accuracy i.e. minimum sensitivity to the changes in the velocity profile of the liquid to be metered.
This review focuses on the experimental and numerical studies of sweeping impingement jets that serve in cooling of hot surfaces. It is known that the impinging jets produce high-localized heat transfer coefficient. The sweeping jet covers a wider area on a hot target to improve the heat transfer rate, they could be used to increase the cooling rate of the impingement surface by disturbing the boundary layer. To display a readable survey, the current review was partitioned to four groups based on engineering configurations. The review shows that the sweeping nozzle gives better efficiency in heat transfer, improved Nusselt number and uniform target surface temperature, compared with the conventional normal jets. The current review reveals that the sweeping-jet mechanism can be achieved either by fluidic oscillator or by exciting a flexible wall forming an oscillating jet. Most of the fluidic oscillator researches are conducted experimentally (27%), while the researches that use flexible wall are about 24%.