Cfd

The suction process in reciprocating compressors is strongly affected by the valve dynamics and the pulsating flow throughout the suction muffler. This paper describes a simplified computational fluid dynamics (CFD) model to simulate the flow through the muffler, suction valve and a small region inside the cylinder. The proposed method is applied to predict the suction process of a small reciprocating compressor and its adequacy is compared with a more time elaborate model in terms of accuracy, computation cost and usability.

Models of the vane-cup and Couette rheometers are compared using computational fluid dynamics as well as approximate solutions. Thixotropy of the fluid is incorporated by means of a model based on experimental data for various toothpastes. Parameters of the model are calculated by fitting the results of step-shear tests in Couette geometry and are subsequently used to predict torque for similar tests in vane-cup geometry. Calculations for the thixotropic model were compared to the calculations for a timeindependent equilibrium model with the same steady-shear rheology. There are two important findings in this work. First, at constant angular velocity, torque in the vane-cup rheometer for the thixotropic model turns out greater than for the equilibrium model, because the structure of the thixotropic fluid has not had enough time to reach equilibrium. This has implications for rheometry and the modeling of mixing operations. In both cases, torques may be underestimated if the standard equilibrium model is used in calculations. The second finding is relevant to rheometry. As is well known, equilibrium model predicts a lower torque value for a vane-cup geometry than for an equivalent Couette geometry. We found that taking thixotropy into account either makes the difference less pronounced or in some cases actually makes torque for vane-cup higher than for Couette. End effects are also analyzed.

The computational fluid dynamics approach is applied to packed bed reactors with moderate tube-toparticle diameter ratios. In order to generate irregular particle arrangements within the reactors, a modified ballistic deposition method is used. While our previous studies were focused on pressure drop and mass transfer characteristics, the present paper uses the same framework to investigate the dispersion phenomena occurring in such reactors. Two different methods, namely the tracer and the postprocessing method, are applied. The first method imitates the experimental procedure in which a non-diffusive tracer is injected into the packed bed. The residence time can be evaluated from the evolution of the tracer concentration. The second method is purely numerical and allows fast residence time estimation. Simulation results are successfully validated against experimental data from literature. The suggested numerical analysis is a valuable tool toward a deeper understanding of the fundamental transport phenomena in such reactors and, consequently, for the improvement of the packed bed performance.

In an effort to corroborate theoretical and experimental techniques used for cold spray particle velocity analysis, two theoretical and one experimental methods were used to analyze the operation of a nozzle accelerating aluminum particles in nitrogen gas. Two-dimensional (2D) axi-symmetric computations of the flow through the nozzle were performed using the Reynolds averaged Navier-Stokes code in a computational fluid dynamics platform. 1D, isentropic, gas-dynamic equations were solved for the same nozzle geometry and initial conditions. Finally, the velocities of particles exiting a nozzle of the same geometry and operated at the same initial conditions were measured by a dual-slit velocimeter. Exit plume particle velocities as determined by the three methods compared reasonably well, and differences could be attributed to frictional and particle distribution effects.

In this paper, a comprehensive computational fluid dynamics (CFD) modelling study was undertaken by integrating the combustion of pulverized dry lignite in several combustion environments. Four different cases were investigated: an air-fired and three different oxy-fuel combustion environments (25 vol.% O 2 concentration (OF25), 27 vol.% O 2 concentration (OF27), and 29 vol.% O 2 concentration (OF29) were considered. The chemical reactions (devolatilization and char burnout), convective and radiative heat transfer, fluid and particle flow fields (homogenous and heterogenous processes), and turbulent models were employed in 3-D hybrid unstructured grid CFD simulations. The available experimental results from a lab-scale 100 KW firing lignite unit (Chalmer's furnace) were selected for the validation of these simulations. The aerodynamic effect of primary and secondary registers of the burner was included through swirl at the burner inlet in order to achieve the flame stability inside the furnace. Validation and comparison of all the combustion cases with the experimental data were made by using the temperature distribution profiles and species concentration (O 2 , CO 2 , and H 2 O) profiles at the most intense combustion locations of the furnace. The overall visualization of the flame temperature distributions and oxygen concentrations were presented in the upper part of the furnace. The numerical results showed that the flame temperature distributions and O 2 consumptions of the OF25 case were approximately similar to the reference combustion case. In contrast, in the OF27 and OF29 combustion cases, the flame temperatures were higher and more confined in the closest region of the burner exit plane. This was a result of the quick consumption of oxygen that led to improve the ignition conditions in the latter combustion cases. Therefore, it is concluded that the resident time, stoichiometry, and recycled flue gas rates are relevant parameters to optimize the design of oxy-fuel furnaces. The findings showed reasonable agreement with the qualitative and quantitative measurements of temperature distribution profiles and species concentration profiles at the most intense combustion locations inside the furnace. These numerical results can provide useful information towards future modelling of the behaviour of pulverized brown coal in a large-scale oxy-fuel furnace/boiler in order to optimize the burner's and combustor's design.

Background: Cerebral folate deficiency (CFD) has been described as a neurological syndrome associated with low 5-methyltetrahydrofolate (5-MTHF) values in cerebrospinal fluid (CSF) with normal folate concentrations in plasma. Our aim was to analyse CSF 5-MTHF concentrations in a paediatric control population and in patients with various neurological disorders. Methods: We studied plasma and CSF samples from 63 paediatric controls (age range: 2 days to 18 years, average: 3.8 years) and from 165 patients (age range: 1 day to 22 years, average: 5.0 years) with severe epileptic encephalopathies of unknown origin, movement disorders, Rett syndrome and mitochondrial diseases. CSF 5-methyltetrahydrofolate was analysed by reverse phase HPLC with fluorescence detection (excitation: 295 nm and emission: 355 nm). Result: A negative correlation between 5-MTHF values and age of controls was observed (r = − 0.468; p < 0.0001) and reference values were therefore stratified into 3 age groups. Regarding patients, 122 out of 165 showed normal CSF 5-MTHF values while 43 showed decreased values ranging from profound to mild deficiencies. Increased CSF total protein values were associated with the presence of low 5-MTHF concentrations (χ 2 = 7.796; p = 0.005). Conclusions: The application of this method has been useful for the establishment of reference values and for diagnosis of CFD in paediatric patients. Furthermore, increased CSF total protein concentrations should be considered as a marker of a possible CFD.

In order to accurately simulate small-scale coastal ocean phenomena, we propose to couple a computational fluid dynamics (CFD) model with the Unstructured Grid Finite Volume Coastal Ocean Model (FVCOM). The CFD model resolves small-scale flows, the FVCOM predicts large-scale background currents, and the resulting hybrid system is able to capture flow phenomena with spatial scales from centimeters to hundreds of kilometers. The coupling is two-way and realized using domain decomposition with aid of Chimera overset grids. Numerical examples are presented to demonstrate the feasibility and performance of the proposed hybrid approach.

Blood flow simulations in computational fluid dynamics (CFD) are seen as a very attractive solution for diagnosing diseases. The main objective of this work is to simulate blood flow in healthy arteries. The governing equations for the Sisko model are presented in cylindrical coordinates. The finite volume method is used for the velocity and wall shear stress at healthy arteries. It is observed that the velocity profile increases due to an increase in Sisko fluid parameters and the radius of healthy arteries. With regard to the fact that blood flow in healthy arteries is non-Newtonian, the fluid obeys the Sisko fluid model. We contemplate that due to an increase in Sisko fluid parameters and the radius of healthy arteries, the wall shear stress profile increases and decreases, respectively.

This paper presents the results of an optimization study using a comprehensive three-dimensional, multi-phase, non-isothermal model of a PEM fuel cell that incorporates the significant physical processes and the key parameters affecting fuel cell performance. The model accounts for both the gas and liquid phase in the same computational domain and, thus, allows for the implementation of phase change inside the gas diffusion layers. The model includes the transport of gaseous species, liquid water, protons, energy and water dissolved in the ion conducting polymer. Water is assumed to be exchanged among three phases; liquid, vapor and dissolved, and equilibrium among these phases is assumed. The model features an algorithm that allows a more realistic representation of the local activation overpotentials, which leads to improved prediction of the local current density distribution. This model also takes into account convection and diffusion of different species in the channels as well as in the porous gas diffusion layer, heat transfer in the solids as well as in the gases and electrochemical reactions. The results showed that the present multi-phase model is capable of identifying important parameters for the wetting behavior of the gas diffusion layers and can be used to identify conditions that might lead to the onset of pore plugging, which has a detrimental effect on the fuel cell performance. This model is used to study the effects of several operating, design and material parameters on fuel cell performance. Detailed analyses of the fuel cell performance under various operating conditions have been conducted and examined.

Heat transfer simulation within heating furnaces is of great significance for prediction and control of the performance of furnaces. In this paper, a set of models is proposed to solve heat transfer problems in a loaded furnace. Furthermore, a 2-dimensional algorithm based on a finite difference method is presented. The heat transfer models are integrated with a furnace model to simulate the heating process of workpieces. Temperature variation of the workpiece with time is predicted by the system. An experiment is carried out for validation of the system. Themain objective of this work is to evaluate the behavior of a heated enclosure, when variable radiant panels are introduced. Experimental investigation shows that their efficiency depends on their position.

A ‘Hybrid electric vehicle' is a vehicle which relies not only on batteries but also on an internal combustion engine which drives a generator to provide the electricity and may also drive a wheel. It has great advantages over the previously used gasoline engine that drives the power from gasoline only. It is a major source of air pollution. The objective is to design and fabricate a two wheeler hybrid electric vehicle powered by both battery and gasoline (PETROL). The combination of both the power makes the vehicle dynamic in nature over conventional automobiles. Hybrid electric vehicles combine an electric motor, battery and power system with an internal combustion engine to achieve better fuel economy and reduce toxic emissions. Equipment and their cost analysis are done. It deals with the fabrication of the vehicle. The final stage would consist of increasing the efficiency of the vehicle in economic ways.

A 3-D two-fluid CFD model in the Eulerian-Eulerian framework was developed to predict the hydrodynamics and heat and mass transfer of sieve trays. Interaction between the two phases occurs via interphase momentum and heat and mass transfer. The tray geometries are ...

Natural ventilation of buildings can be made by employing pressure difference among different parts of buildings induced by external wind. Wind-catching parts have positive pressure while lee parts have negative one. When there are openings on both sides, airflow is induced through the building. In this study, experiments and numerical computations were conducted to study wind-driven ventilation through two-dimensional scaled models of buildings. The purpose is to examine effects of: 1) pitch angle (p) of the roof, and 2) relative positions of openings on both sides on induced flow-rate through the building. The experiments were performed in the wind tunnel at the Laboratory of Fluid Mechanics of Ho Chi Minh City University of Technology. The scaled models of buildings had dimensions of order of 10cm. Velocities of wind passing the model and induced airflow through the models were measured with a hot-wire anemometer. The computations were made by a CFD (computational fluid dynamics) technique. Governing equations were discretized with Finite Volume Method. Standard κ-ε model was used for turbulence. Computed domain included both the buildings and appropriate extended space.

This paper considers the age of air in a ventilated space with multiple supply inlets; the local mean age (LMA) of air is different from one inlet to another in multiple supply inlet situations. The purpose of this paper is to investigate theoretically the relations between the LMAs arising from each supply inlet and the overall combined LMA for all inlets. Transient concentration distributions are calculated using a CFD package in a simple room configuration with two inlets and one outlet, to verify the relations. Tracer gases are injected with a step-up method at each supply inlet individually, and at both inlets simultaneously. As a result, it can be found that the steady state concentration, with a continuous tracer injection at each supply inlet, works as a weighting factor for the corresponding LMA in calculating the overall combined LMA for the multiple inlet situations.

The main intent of this work is to simulate the aerodynamic effects on different configuration of commercial and delta wing at different angle of attack. This investigation aims to suggest a better aerodynamic configuration for wing to reduce the induced drag formed on wing during flight operation and in-turn improves the efficiency of the UAV. Simulation processes of computational fluid dynamic (CFD) on wing models for medium size high speed UAV, using typical section as NACA 2412 airfoil is been carried out at 1⁰, 2⁰ and 4⁰ twist angle. The twist is provided to adjust pressure distribution henceforth lift distribution along the wing. ANSYS Fluent is used to analyze the pressure distribution on the surface of wing at speed of 0.6 Mach. The lift and drag forces are also determined which were used for calculating the coefficients of lift and drag. The obtained results were used to establish a comparison between aerodynamic performances of all provided models.

An attempt has been made to carry out CFD based analysis using FLUENT to fluid flow and heat transfer characteristics of solar air heater. 3D model of the Solar Air heater involving air inlet, absorber plate, glass, modelled by ANSYS Workbench and the unstructured grid was created in ANSYS. The results were obtained by using ANSYS FLUENT software. This work is done by using computational fluid dynamics (CFD) tool with respect to flow and temperature distribution inside the solar air heater.

The thermal performance of a natural draft dry cooling tower (NDDCT) under a crosswind has been investigated using a general-purpose CFD code. A three-dimensional study using the standard k–ε turbulence model to simulate airflow in and around an NDDCT has been conducted. A parametric study has been carried out to examine the effect of crosswind velocity profile and air dry-bulb temperature on the thermal performance of an NDDCT. Two approaches have been considered in this study to quantify the crosswind effect. Firstly, simulations have been conducted at the nominal conditions and crosswind effect has been represented by thermal effectiveness parameter. Secondly, the ejected heat from the NDDCT has been maintained at a constant value (285 MW) and the crosswind effect has been represented by the change in the cooling tower approach parameter. After quantifying the effect of the crosswind on the thermal performance, windbreak walls have been introduced as a means of reducing this effect. The results in this paper show the importance of considering the crosswind velocity profile. Moreover, the introduction of windbreak walls has indicated an improvement in reducing the thermal performance losses due to the crosswind. Copyright © 2004 John Wiley & Sons, Ltd.

The object moving at high speeds encounter forces which tend to decelerate the objects. This resistance in the medium is termed as drag which is one of the major concerns while designing high speed aircrafts. Another key factor which influences the design is the air drag. The main challenges faced by aerospace industries is to design the shape of nose cone of flying object that travels at high speeds with optimum values of air drag. This study deals with computational analysis on elliptical nose cone profiles of a commercial aircraft. The effect of nose shape on the drag is studied at subsonic flow with Mach 0.3.The scope of this paper is to develop some prototype profiles with outstanding aerodynamic qualities and low cost for use in construction projects for aircrafts increasing their efficiency and effect on target. The motivation for such a work is caused by lack of data on aerodynamics for profile of elliptical nose cone and especially improved aerodynamic qualities that can be used in designing aircrafts. Flow phenomena observed in numerical simulations for different AOA for elliptical nose cone profile are highlighted, critical design aspects and performance characteristics of selected nose cone are presented.

In this paper we present a methodology for adjustment of subsonic compensation characteristics of an aerodynamic-compensation Pitot tube. This methodology is based on manipulation of a Pitot tube profile (shape) downstream of the static pressure port such that its subsonic characteristics are modified while the supersonic characteristics remain unchanged. Due to this “rear-body” shape adjustment, complete redesign of a developed or in service Pitot tube is not required. We have used computational fluid dynamics tools in the analysis and design refinement of a Pitot tube by rear-body shape adjustment. The complete Mach number regime (M&lt;2) has been computationally analyzed for three different rear-body profiles. The results of our study indicate that significant variation in subsonic compensation characteristics of a Pitot tube is possible by this method.

Local mean age of air Homogeneous emission method Air exchange efficiency a b s t r a c t Wind can provide relevantly clean external (rural) air into urban street network, i.e. city ventilation. The local mean age of air denotes the time it takes for the external air to reach a location after entering the urban canopy layer. The air exchange efficiency denotes the efficiency of flushing the street network with external air. However, difficulties exist in calculating the local mean age of air in a city due to open boundaries. The traditional experimental homogeneous emission method is adapted here in a CFD method to predict the urban local age of air and analyze the air exchange efficiency for city ventilation. Three simple city models are considered, including a round city model, a square city model and a long rectangular city with one main street parallel to the approaching wind or with two crossing streets. The difference in the city shape results in significant difference in the local mean age of air. In the round city of one narrow street, two inflows through street openings converge close to the city centre and exits through the street roof, so the air close to the city centre is relatively old and the air exchange efficiency is low (30%). For a round city with two crossing streets, a slightly non-parallel wind to the main street generates younger air and the higher air exchange efficiency in the city.

Phosphoinositides are lipids that are present in the cytoplasmic leaflet of a cell's plasma and internal membranes and play pivotal roles in the regulation of a wide variety of cellular processes. Phosphoinositides are molecularly diverse due to variable phosphorylation of the hydroxyl groups of their inositol rings. The rapid and reversible configuration of the seven known phosphoinositide species is controlled by a battery of phosphoinositide kinases and phosphoinositide phosphatases, which are thus critical for phosphoinositide isomer-specific localization and functions. Significantly, a given phosphoinositide generated by different isozymes of these phosphoinositide kinases and phosphatases can have different biological effects. In mammals, close to 50 genes encode the phosphoinositide kinases and phosphoinositide phosphatases that regulate phosphoinositide metabolism and thus allow cells to respond rapidly and effectively to ever-changing environmental cues. Understanding the distinct and overlapping functions of these phosphoinositide-metabolizing enzymes is important for our knowledge of both normal human physiology and the growing list of human diseases whose etiologies involve these proteins. This review summarizes the structural and biological properties of all the known mammalian phosphoinositide kinases and phosphoinositide phosphatases, as well as their associations with human disorders. phosphatase and tensin homologue deleted on chromosome 10; PTPMT1, protein tyrosine phosphatase localized to the mitochondrion-1; PX, phox; RANKL, receptor activator of nuclear factor-jB ligand; RhoGDI, guanine nucleotide dissociation inhibitor of Rho; ROCK, Rho kinase; ROS, reactive oxygen species; S6K, S6 kinase; Sac, suppressor of actin; SAM, sterile a motif; SBF1, SET binding factor 1; SCF, stem cell factor; SDF1, stromal cell-derived factor-1; SET, Suvar3-9 Enhancer-of-zeste Trithorax; SH2, Src homology 2; SHIP, SH2-containing inositol phosphatase; SID, SET-interacting domain; SKICH, SKIP carboxyl homology; SKIP, skeletal muscle-and kidney-enriched inositol polyphosphate phosphatase

In this paper the description of the internal flow in a Francis turbine is addressed from a numerical point of view. The simulation methodology depends on the objectives. On the one hand, steady simulations are able to provide the hill chart of the turbine and energetic losses in its components. On the other hand, unsteady simulations are required to investigate the fluctuating pressure dynamics and the rotor-stator interaction. Both strategies are applied in this paper to a working Francis turbine in Colombia. The employed CFD package is ANSYS-CFX v. 11. The obtained results are in good agreement with the in site experiments, especially for the characteristic curve.

This paper presents the results of numerical investigations of bridge aeroelasticity. In particular static coefficients and instationary flutter derivatives for a symmetric bridge deck section using the Unsteady Reynolds-Averaged Navier-Stokes (URANS) method are obtained. The numerical model uses the Finite Volume discretization. The performed simulations are two-dimensional, and the turbulence is simulated by the k-o-SST model. The numerical model is validated by force and pressure measurements from wind tunnel experiments. The main goal of this work is to assess the capability of the numerically affordable URANS method for estimating bridge flutter derivatives. In general the simulated aeroelastic surface pressures and integrated forces are in good accordance with the aeroelastic pressure fields and forces identified from comparative wind tunnel tests. This is particularly the case in the range of moderate reduced velocities and for flow effects without dominant vortex shedding. The results demonstrate the capability of the URANS method to derive bridge flutter derivatives and static coefficients in a numerically effective and efficient way.

Mesh generation has been frequently the most time consuming step in typical CFD analysis studies. In the past two decades, adaptive Cartesian mesh methods have gained increasing popularity among CFD researches, mainly because of its simplicity and the possibility of automating mesh generation step. In contrast to body-fitted mesh, cells in Cartesian mesh are aligned with coordinate axes. In adaptive Cartesian mesh, cells near the objects' boundary are recursively refined using quad-tree (two-dimensional) or octree (three-dimensional). Then, cells intersecting the objects' boundary are clipped by the surfaces, leaving numerous small irregular shaped cells, called cut-cells. Most of the computational efforts required to generate adaptive Cartesian mesh is concentrated on the cut-cell clipping operation. To achieve the computational accuracy in the subsequent numerical solver, the number of cut-cells can be easily over millions, demanding substantial amount of computation time. Reducing mesh generation time matters more especially for unsteady flow simulation involving moving objects, which requires frequent regeneration of meshes for varied postures of the object. In this paper, we report an efficient novel approach to generating adaptive Cartesian mesh by parallelization using the graphics processing unit. The proposed method consists of the following three steps: (1) computing cross-sectional curves of object boundary, (2) octree refinement based on the section curves, and (3) cut-cell clipping. Because each step is designed to be highly parallelizable, we also implemented it on a graphics processing unit, showing orders of magnitude faster performance than the CPU version.

Recently, computational fluid dynamics (CFD) models of flows in membrane channels have been proposed and validated against published simplified models available in the literature. In this paper, experimental and numerical analysis is performed for a reverse osmosis (RO) module and results compared in order to provide further validation of the model from a practical prospective. Our results show that, in order to improve the accuracy of the calculations at high pressure, a membrane permeability that varies with the operational pressure must be taken into account.

The electric motor efficiency represents the effectiveness with which the motor converts electrical energy into mechanical energy. As the energy losses are converted into heat, which is dissipated by the motor frame aided by internal and external fans, a better cooling system adds up to better efficiency. In recent years, improvements in motor efficiency have been achieved but at higher costs. By using Genetic Algorithms (GAs), changes are introduced to the fan shape looking for a better aerodynamic performance. The evaluation of the achieved fan efficiency with the modified shapes is performed with Computational Fluid Dynamics (CFD) simulation software.

This study describes a detailed procedure for design of marine screw propellers in combination with stators, also known as fixed guide vanes or pre/post swirl devices, based on lifting line theory. The design procedure presented here involves the realistic representation of the propeller slipstream, which is contracted form of helical vortices. The slipstream shape is allowed to deform and to align with the direction of local velocity that is the sum of the inflow wake velocity and induced velocity. As the slipstream deformation is the key parameter in the design of reaction type performance improvement devices, the design methodology is applied to a stator device behind the propeller, and then the hydrodynamic performance of the combined propulsor is analyzed. Furthermore a CFD analysis based on Finite Volume Method is applied. The results from both methods are compared and discussed.

a b s t r a c t This paper presents a numerical study of the effect of oscillation amplitude in oscillatory baffled column (OBC) using computational fluid dynamics. The numerical work was carried out for single phase liquid flow for an unsteady 3-D model using commercial software, Fluent (2006). This work was concentrated on the effect of oscillation amplitude. Three amplitudes of 5, 10 and 15 mm with constant frequency of 1 Hz are applied. Vortex and cycle average velocities at different points are analyzed. The studies show the maximum velocity for 5 mm, 10 mm and 15 mm in an OBC are 0.11 m/s, 0.25 m/s and 0.40 m/s respectively in the first cycle of oscillation. At a constant frequency, greater oscillation

A 3-D two-fluid CFD model in the Eulerian-Eulerian framework was developed to predict the hydrodynamics and heat and mass transfer of sieve trays. Interaction between the two phases occurs via interphase momentum and heat and mass transfer. The tray geometries are based on the large rectangular tray of Dribika and Biddulph and FRI commercial-scale sieve tray of Yanagi and Sakata. In this work a CFD simulation is developed to give predictions of the fluid flow patterns, hydraulics, and mass transfer efficiency of distillation sieve trays including a downcomer. The main objective has been to find the extent to which CFD can be used as a design and prediction tool for real behavior, concentration and temperature distributions, and efficiencies of industrial trays. Despite the use of simple correlations for closure models, the efficiencies obtained are very close to experimental data. The results show that values of point efficiency vary with position on the tray because of variation of affecting parameters, such as velocities, temperature and concentration gradients, and interfacial area. The simulation results show that CFD can be used as a powerful tool in tray design and analysis, and can be considered as a new approach for efficiency calculations and as a new tool for testing mixing models in both phases. CFD can be used as a "virtual experiment" to simulate tray behavior under operating conditions.

Water ingestion into vehicles HVAC system causes fogging of windows, drivers lost in concentration and hence raising some safety issues. Growth of bacteria, excess level of moisture and musty smell in vehicles are also a result of water ingress into cars. Refer to S.A.A. Abdul Ghani [9] for more problems from water ingress.

CITATIONS 158 READS 537 2 authors, including: Some of the authors of this publication are also working on these related projects: Harness multiphase flows with phase change for enabling process innovations View project Vivek V. Ranade Queen's University Belfast 170 PUBLICATIONS 3,596 CITATIONS SEE PROFILE All content following this page was uploaded by Vivek V. Ranade on 13 October 2014.

This study proposes an effective numerical model based on the Computational Fluid Dynamics (CFD) approach to obtain the flow structure around a passenger car with wing type rear spoiler. The topology of the test vehicle and grid system is constructed by a commercial package, ICEM/CFD. FLUENT is the CFD solver employed in this study. After numerical iterations are completed, the aerodynamic data and detailed complicated flow structure are visualized using commercial packages, Field View and Tecplot. The wind effect on the aerodynamic behavior of a passenger car with and without a rear spoiler and endplate is numerically investigated in the present study. It is found that the installation of a spoiler with an appropriate angle of attack can reduce the aerodynamic lift coefficient. Furthermore, the installation of an endplate can reduce the noise behind the car. It is clear that the vertical stability of a passenger car and its noise elimination can be improved. Finally, the aerodynamics and aero-acoustics of the most suitable design of spoiler is introduced and analyzed.

The future success of many electronics companies will depend to a large extent on their ability to initiate techniques that bring schedules, performance, tests, support, production, life-cycle-costs, reliability prediction and quality control into the earliest stages of the product creation process. Earlier papers [1, 2] have discussed the benefits of an integrated analysis environment for system-level thermal, stress and EMC prediction. This paper focuses on developments made to the stress analysis module and presents results obtained for an SMT resistor. Lifetime predictions are made using the Coffin-Manson equation. Comparison with the creep strain energy based models of Darveaux [3] shows the shear strain based method to underestimate the solder joint life.

The performance of heat exchangers, for single-phase flows in particular, can be improved by many active and passive augmentation techniques. One such passive augmentation technique used for analysis this paper is vortex generation with the help of twisted tapes. An experimental analysis is carried out on a plain tube and tube with twisted tape under different mass flow rates and heat flux. A tube of 48mm diameter and 400mm length was taken for the experiment and a twisted tape of twist ratio yw=9.09 and thickness 2mm with 400mm length was inserted in the tube. Air supplied through the tube was heated up by the band heater. Temperatures of the air at different sections were recorded with the help of thermocouples. These experimental results are then compared with the numerical model for validation. A parametric study is carried out of different twist ratios of twisted tapes on temperature distribution of air at different section of the tube along its length. Three different twist ratios were considered 9.09, 6.05 and 3.64. Among these it was found that the twisted tapes with 3.64 gave an improved heat transfer as compared to other two twist ratios as well as the plain tube.

While models ofmembrane systems with varying degrees of complexity have been developed since the early 196Os, reports ofthe use of computational fluid dynamics to provide in-depth insights into the separation phenomenon have only recently appeared in the literature. This paper describes the validation and application ofa computational fluid dynamics model ofpressure-driven membrane processes involving selective removal of components in the feed channel and their transfer to the permeate channel. The effects of changes in rejection, wall permeation rates and solution properties on velocity and concentration profiles are presented for empty channels and channels with eddy promoters. For high polarisation applications typically encountered in conventional ultrafiltration applications, the results demonstrate the need for very fme meshes near the membrane wall, together with high order numerical schemes and accurate modelling of rejection and physical property variations in order to obtain accurate and reliable predictions of the polarisation and flow phenomenon.

Blended wing body (BWB), as per the name is a single body comprising both the wings and the body of the aircraft, unlike conventional aircraft where wings are attached to the fuselage and can be distinguished in the aircraft's structure. The advantages of BWB include drag reduction, high lift to drag ratio of overall body, higher fuel efficiency, increased seating capacity and reduced hangar space at the airport. At present the concept of BWB is not likely to be manufactured due to the limiting constraints of structures, aero-structural integration, issues pertaining to pressurization of the cabin, as well as the large frontal area of the wing that would in turn increase the drag coefficient. To overcome the aeromechanical issues the flow simulation over the BWB is done. The 2-D geometry was developed and kept as close as possible to the real designs gathered from the literature review. The results of the flow simulation fulfil the conditions set forward in the theory. The contours of various parameters depict the accurate variation in the flow regime around the BWB body.

Supercritical airfoil and wing have been developed more than 30 years. For supercritical wing design, one of the most important objectives is improving the cruise efficiency. And some other characteristics are also very important for a practicable supercritical wing, such as drag divergence characteristic, buffet boundary, stall behaviors, and so on. In this study, the aerodynamic characteristics of supercritical airfoil were carried out by numerical simulation (CFD) using ANSYS software and then compared with experimental results using subsonic wind tunnel. The air velocity varied from 5 to 15m/s and attack angle varied from -5 to 30 0 for both numerical and experimental studies.

Propellers are responsible for the altitude and attitude motions of a Quadcopter type of unmanned aerial vehicles (UAV). A propeller generates the thrust in the axial direction of the propeller's rotation. In the present study, the computational fluid dynamics (CFD) analysis has been performed on a Quadcopter and its propeller to calculate the thrust generated by the propeller under the applied rotational speed. The solid CAD models of a Quadcopter and propeller have been designed in Catia v5. The created propeller design has been imported to ANSYS workbench fluid flow (fluent) module. Simulation has been conducted by using the k-epsilon turbulence model. Furthermore, the obtained results have been imported from fluent flow module to transient structural module in order to find out the deformation and stress induced in the propeller, due to the pressure generated by the rotation of propeller at 6500 RPM. From the obtained results, it can be seen that the designed propeller can generate the required amount of thrust force to lift the Quadcopter and can sustain the dynamic loading without failure.

Optimisation of Organic Rankine Cycles (ORCs) for binary cycle applications could play a major role in determining the competitiveness of low to moderate renewable sources. An important aspect of the optimisation is to maximise the turbine output power for a given resource. This requires careful attention to the turbine design notably through numerical simulations. Challenges in the numerical modelling of radial-inflow turbines using high-density working fluids still need to be addressed in order to improve the turbine design and better optimise ORCs. This paper presents preliminary 3D numerical simulations of a radial-inflow turbine working with high-density fluids in realistic geothermal ORCs. Following extensive investigation of the operating conditions and thermodynamic cycle analysis, the refrigerant R143a is chosen as the high-density working fluid. The 1D design of the candidate radial-inflow turbine is presented in details. Furthermore, commercially-available software Ansys-CFX is used to perform preliminary steady-state 3D CFD simulations of the candidate R143a radial-inflow turbine at the nominal operating condition. The real-gas properties are obtained using the Peng-Robinson equations of state. The thermodynamic ORC cycle is presented. The preliminary design created using dedicated radial-inflow turbine software Concepts-Rital is discussed and the 3D CFD results are presented and compared against the meanline analysis.

The increasing interest among architects and planners in designing environmentally friendly buildings has led to a desire to explore and integrate renewable sources of energy. Roof mounted wind turbines is a technology that presents a high potential for integration within the built environment. However, there is a state of uncertainty regarding the feasibility of these wind turbines. This paper argues that part of this uncertainty is attributed to uninformed decisions about positioning and locating urban wind turbines. This is underpinned by lack of consideration to the accelerating effect of different roof shapes, buildings' heights and surrounding urban configurations. This paper aims to present the results of Computational Fluid Dynamics (CFD) simulations for the purpose of identifying the effect of different roof shapes on the energy yield and positioning of roof mounted wind turbines covering different buildings' heights within different urban configurations under different wind directions. Results from this investigation suggest that an increase in energy yield could be achieved which can reach 56.1% more electricity in the case of a vaulted roof if an informed wind assessment above buildings' roofs is carried out.

In this paper, a set of potential hydrocyclone designs are explored for fines classification using Computational Fluid Dynamics (CFD) technique. The CFD model uses Volume of Fluid multiphase model coupled with Reynolds Stress turbulence model for two phase flow predictions. Lagrangian Particle Tracking and Algebraic Slip Mixture model (ASM) modified with shear lift forces and slurry rheology corrected with fines fraction are used to predict the particle classification. Conventional cylindrical-conical design and various novel cyclone designs having a combination of multiple and small cone angles, tapered vortex finder and air core free designs are considered in this study. Simulation results are presented in terms of mean and turbulent flow field along with particle efficiency curve. Predictions show that all the tested novel designs are inherently having the potential for finer cut separation and higher tangential velocity compared to the conventional design. Cyclone design with a small cone angle is further modified by placing various sizes of rods at the center axis of the cyclone. Multiphase simulations with modified ASM model are also carried out for the multiple cone angles design, standard design, and the modified small cone angle design with full length rod at 15 wt% of solids. Performance by multiphase simulations show that multiple cone angles design and modified small cone angle design with the full length rod are the best among the tested designs yielding high separation efficiency, smaller cut-point and minimum coarse particle misplacement due to resultant turbulence minimization.