Fan Model Research Articles

Projection Effects of Large-scale Structures on Weak-lensing Peak Abundances

Abstract High peaks in weak lensing (WL) maps originate dominantly from the lensing effects of single massive halos. Their abundance is therefore closely related to the halo mass function and thus a powerful cosmological probe. However, besides individual massive halos, large-scale structures (LSS) along lines of sight also contribute to the peak signals. In this paper, with ray-tracing simulations, we investigate the LSS projection effects. We show that for current surveys with a large shape noise, the stochastic LSS effects are subdominant. For future WL surveys with source galaxies having a median redshift z med ∼ 1 or higher, however, they are significant. For the cosmological constraints derived from observed WL high-peak counts, severe biases can occur if the LSS effects are not taken into account properly. We extend the model of Fan et al. by incorporating the LSS projection effects into the theoretical considerations. By comparing with simulation results, we demonstrate the good performance of the improved model and its applicability in cosmological studies.

Enhancing flood hazard estimation methods on alluvial fans using an integrated hydraulic, geological and geomorphological approach

Abstract. Due to the uncertainty concerning the location of flow paths on active alluvial fans, alluvial fan floods could be more dangerous than riverine floods. The United States Federal Emergency Management Agency (FEMA) used a simple stochastic model named FAN for this purpose, which has been practiced for many years. In the last decade, this model has been criticized as a consequence of development of more complex computer models. This study was conducted on three alluvial fans located in northeast and southeast Iran using a combination of the FAN model, the hydraulic portion of the FLO-2D model, and geomorphological information. Initial stages included three steps: (a) identifying the alluvial fans' landforms, (b) determining the active and inactive areas of alluvial fans, and (c) delineating 100-year flood within these selected areas. This information was used as an input in the mentioned three approaches of the (i) FLO-2D model, (ii) geomorphological method, and (iii) FAN model. Thereafter, the results of each model were obtained and geographical information system (GIS) layers were created and overlaid. Afterwards, using a scoring system, the results were evaluated and compared. The goal of this research was to introduce a simple but effective solution to estimate the flood hazards. It was concluded that the integrated method proposed in this study is superior at projecting alluvial fan flood hazards with minimum required input data, simplicity, and affordability, which are considered the primary goals of such comprehensive studies. These advantages are more highlighted in underdeveloped and developing countries, which may well lack detailed data and financially cannot support such costly projects. Furthermore, such a highly cost-effective method could be greatly advantageous and pragmatic for developed countries.

Numerical simulation of solar chimney power plant adopting the fan model

Abstract Numerical simulations and design of solar chimney power plant adopting the fan model was presented in this study. A mathematical model describing fluid flow and heat transfer has been set up for the three regions of solar chimney power plant: collector, chimney and turbine. The Spanish prototype was chosen as an example for numerical simulation that incorporates turbine model, simulation during turbine operation and no load conditions were compared. For this purpose a simulation of 3D solar chimney power plant system with the standard k-e turbulence model was developed, using CFD Ansys Fluent. Furthermore the effect of turbine operation and the influences of pressure drop across the turbine and solar radiation were investigated and the results revealed that the variation of solar radiation has an evident effect on the flow and heat transfer characteristics. Meanwhile the influence of turbine pressure drop on the collector efficiency was slight, while has a considerable effect on the power output.

Study on leakage and ventilation scheme of gas pipeline in tunnel

Due to poor ventilation conditions in the tunnel, if gas pipeline leaks, the consequence of the accident will be more serious. Therefore, in order to avoid the explosion in the rush-repair process, the gas in the tunnel needs to be discharged. Thus, it is necessary to study the leakage law and ventilation scheme of gas in the tunnel. Based on the computational fluid dynamics (CFD) theory, this paper takes Yanyingshan tunnel of China-Myanmar gas pipeline for instance, Fluent software is used to establish the leakage model of the gas pipeline and fan model in the tunnel. The influence of different factors on the leakage diffusion law and the influence of fan locations and number of fans on gas concentration are analyzed. It can be concluded that: (1) Leakage location, leakage area and pipeline pressure have great influence on the gas leakage and diffusion, leakage hole direction and leakage form have little influence on the gas leakage and diffusion. (2) Set the block valve at both ends of the tunnel can effectively reduce the duration of leakage jet. (3) In order to make ventilation efficient, the fan should be arranged in a higher position and needs to be at a distance from the top of the tunnel. (4) Parallel use of two fans has better ventilation effect than single fan.

Evolution of the fan casing treatment design of the counter rotating turbofan with the purpose of increasing its acoustic performance

The results of an experimental study of the effects of several slot type casing treatment (STCT) configurations on ducted counter rotating fan model (DCRF) noise are given in present work. The casing treatment design parameters such as lattice duty cycle and the cavity height were varied. It is shown that the most important parameter is the duty factor of the lattice. The configuration of STCT, which provides the greatest reduction of sum sound power level of the fan model was installed over the second rotor only and had the highest duty factor.

Modelling the static stress–strain state around the fan-structure in the shear rupture head

• Mathematical model of an equilibrium fan between elastic half-planes is constructed. • Length of the fan is evaluated based on the singular solution for edge dislocation. • Potential mechanisms of fan-structure formation in a fault are considered. • Original method of superposition of dislocations is suggested. • Fields of stresses and displacements around the fan-structure are computed. The mathematical model of an equilibrium fan-structure in the interface between two elastic blocks, simulating the shear rupture head in a hard rock under high confining pressure, is constructed. The stress–strain state far from the fan-structure is analyzed with the help of a solution of the problem on edge dislocation. The fan length is estimated using this solution. The model of formation of two oppositely directed fans due to the localized action of tangential stress, which pushes two edge dislocations with antiparallel Burgers vectors, is proposed. In complete formulation, the problem on an equilibrium fan-structure in the interface between infinite elastic half-planes is analyzed by means of original method of superposition of dislocations, leading to two nonlinear integral equations in the fan zone. To solve them numerically, the method of successive approximations is applied. Based on this method, fields of stresses and displacements around the equilibrium fan modelling of a deep-seated shear rupture in the seismogenic zone of the Earth’s crust are computed. Such fields can be used, when setting the initial data in the analysis of dynamics of the fan-shaped mechanism.

Insights into the annealing process of sol-gel TiO2 films leading to anatase development: The interrelationship between microstructure and optical properties

The microstructure and optical properties of TiO2 thin films, prepared by the sol-gel dip coating technique on glass substrates, were inspected. After deposition, the films were annealed at several temperatures in the 400–850 °C range and the resulting nanostructured films were studied by different techniques showing that their structural and optical characteristics evolved significantly with the increased annealing temperature. The analysis of these results by the assumption of the Tauc Lorenz model and the use of Wemple–DiDomenico equation leads to a correlation between microstructural aspects and optical characteristics of the films. Thus, crystallization processes (nucleation, growth and phase transformation) and the evolution of films texture and thickness with increasing annealing temperatures are related with the variation of the refractive index, average gap and extinction coefficient during annealing. Finally, the free-carrier concentration in the films, estimated from the Spitzer–Fan model, ranged from 1.44 × 1019 cm−3 to 3.07 × 1019 cm−3 with the changing annealing temperature, which is in agreement with those obtained in similar anatase thin films from electrical measurement techniques.

Developing an Integrated Method for Optimal Design of Chilled Water Plants in HVAC Systems

Buildings account for a large portion of energy use in the US. Many those buildings have equipped with central plants to produce chilled water supplied to central air handling units. The chilled water plant design can have a significant impact on building energy uses and costs. In this paper, an integrated method for optimal design of chilled water plants is developed in order to minimize life cycle cost. The method integrates an optimization procedure with models that perform detailed cooling load analysis, pump head and energy calculations and life cycle cost analysis. The pump heads are determined by friction and fitting equations with specified flow parameters. The energy calculations are achieved by using chiller, pump and fan models. Genetic algorithm GA is used to solve the constrained optimization problem. The optimal design variables are the condenser and chilled water piping sizes, the condenser and chilled water temperature differences and the chilled water supply temperature. The method is evaluated using an existing building on different climate zone locations. The evaluation results show this integrated method can achieve better results than traditional process. The saving in life cycle cost could be up to 8% depending on locations and project specifications.

Aerodynamic and Structural Analysis of Ceiling Fan for Different Blade Materials

Creating a breeze in a space is necessary to enhance convective heat transfer and accordingly body heat dissipation. In most tropical countries fan are extensively used to create indoor breeze, improve the space air distribution and hence enhance the feeling of comfort. The fan speed, diameter, number of blades, blade angle and location, all play an important role in determining the induced flow pattern features in the space. In present work analytical calculations are performed to calculate the coefficient of performance, estimate the net air flow per unit power input for four different blade materials namely steel, aluminium, GFRP composite and PVC. The ceiling fan model is created in CREO elements/Pro 5.0 and the whole geometry is imported into ANSYS CFX. Profile GM 15 airfoil is selected for the blade analysis. The ceiling fan simulation is done for the entire fan model including blade behaviour due to aerodynamic lift and drag forces which also accompanied by bending stresses and deflection. The comparisons for the combined loads are studied for better stability and performance of the blade for different materials. ANSYS APDL software is used to do the structural and modal analysis. At last, the monthly and yearly power consumption by ceiling fan for different blade materials is also calculated.

The Strength Analysis of CFM56 Engine Blade

Aero engine is a kind of thermodynamic machinery, which require have strict aerodynamic load, mechanical load and strong durability, its longevity depends largely on the life of its main components. In this paper, a series of studies are carried out on the strength of fan blades of CFM56 engine, which provide a reference value for improving the reliability of the engine. The finite element model of the engine fan is established by using CATIA’s finite element software.The centrifugal stress distribution of the fan at different speeds and the influence of torque on fans under different speeds are calculated respectively, and the static strength of the fan is checked.

Cooling Fan Model for Thermal Design of Compact Electronic EquipmentModeling of Swirl Flow at the Exit of Axial-Flow-Fan

Cooling Fan Model for Thermal Design of Compact Electronic EquipmentModeling of Swirl Flow at the Exit of Axial-Flow-Fan

Study on numerical modeling of jet fans

An overview of ways of jet fan modeling with the use of Ansys Fluent methods is presented. The theoretical models were built and validated basing on the experimental measurements made by Giesen et al. (2011). The results obtained with the all models were compared with this experimental data and next the detailed discussion was provided. A special attention was paid to the turbulence modeling, the range and the shape of the jet produced by the fan.Ansys Fluent supports three suitable approaches allowing for accurate mapping of the axial fan operation, which differ in the degree of simplification of the reality. The first approach involves modeling a fan as a volume source of momentum. All three momentum components can be set, so the fan axis can be freely oriented in the space. The second approach involves modeling a fan with known characteristic. A fan is here a 3D object, but the fan rotor is a plane surface of zero thickness. The model is more accurate, but requires a set of parameters, which should be determined by the measurements. In the third approach a fan is also modeled as a 3D object, in this case the rotor has the real spatial dimensions. This model is capable to calculate all fan features by itself, but requires more computational resources. Apart from the above the fourth fan model as a velocity inlet is willingly used.The selection of the model is dependent on data available and required minuteness of the fan representation and operation.

Fan Similarity Model for the Fan–Intake Interaction Problem

Very high bypass ratio turbofans with large fan tip diameter are an effective way of improving the propulsive efficiency of civil aero-engines. Such engines, however, require larger and heavier nacelles, which partially offset any gains in specific fuel consumptions. This drawback can be mitigated by adopting thinner walls for the nacelle and by shortening the intake section. This binds the success of very high bypass ratio technologies to the problem of designing an intake with thin lips and short diffuser section, which is well matched to a low speed fan. Consequently, the prediction of the mutual influence between the fan and the intake flow represents a crucial step in the design process. Considerable effort has been devoted in recent years to the study of models for the effects of the fan on the lip stall characteristics and the operability of the whole installation. The study of such models is motivated by the wish to avoid the costs incurred by full, three-dimensional (3D) computational fluid dynamics (CFD) computations. The present contribution documents a fan model for fan–intake computations based on the solution of the double linearization problem for unsteady, transonic flow past a cascade of aerofoils with finite mean load. The computation of the flow in the intake is reduced to a steady problem, whereas the computation of the flow in the fan is reduced to one steady problem and a set of solutions of the linearized model in the frequency domain. The nature of the approximations introduced in the fan representation is such that numerical solutions can be computed inexpensively, while the main feature of the flow in the fan passage, namely the shock system and an approximation of the unsteady flow encountered by the fan are retained. The model is applied to a well-documented test case and compares favorably with much more expensive 3D, time-domain computations.

Performance prediction of proton exchange membrane fuel cell engine thermal management system using 1D and 3D integrating numerical simulation

The cooling system of proton exchange membrane fuel cell (PEMFC) engine was simulated by 1D and 3D collaborative simulation method. Firstly, the resistance characteristics of the flow channel are obtained by simulating the airside flow model. A three-dimensional simulation model including dual fans and radiator is also established to simulate the airflow distribution. The one-dimensional simulation model of 30 kW PEMFC engine cooling system that are mainly composed of a thermostat, water pump, and fan and radiator model is established. Secondly, the heat dissipation performance of the cooling system is calculated by using the coupled simulation model. It is found that the simulation results of the amount of heat transferred are in good agreement with the experimental data by compromising, which proves that the model is reasonable. Finally, the thermal performance of the extreme operating conditions of the PEMFC system is simulated by means of a simulation model. By monitoring the flow of the pump and the fan speed, we can maintain the stack internal heat balances, so that the stack efficient and stable operation. The results demonstrate that the 3D simulation can get the distribution of fluid flow more accurately, while the simulation time of 1D thermal system is short and can guide the matching of heat transfer parts quickly.

Bi-Gaussian stratified effect of rough surfaces on acoustic emission under a dry sliding friction

Abstract Bi-Gaussian stratified theory is introduced into the field of acoustic emission (AE). A deterministic AE RMS model under a sliding friction is established referring to the existing Fan's statistical model. The Johnson and the modified Pawlus approaches are performed on real worn surfaces, yielding non-Gaussian and bi-Gaussian reconstructed surfaces. The deterministic model is applied to the above surfaces, finding that the bi-Gaussian stratified characteristic is close to a real sliding friction. The superiority of the modified Pawlus reconstruction approach is revealed. With respect to the improper assumption of Fan's model on the Gaussian distribution, a further investigation on re-establishing a bi-Gaussian statistical AE model under a sliding friction is expected.

Calculation of sound power level of tandem axial fan

A numerical simulation of the flow in axial fans with single and tandem geometrically equivalent blade rows was carried out. During the research, the sound power level of the fans was calculated. The acoustic characteristics of the single fan obtained in the numerical experiment were compared with the results of the physical experiment. The divergence between the results of the physical and numerical experiments on the sound power level for the first harmonic is 0.08 %, for the second harmonic – 0.35 %. In order to reduce the acoustic emission, a 3D model of the axial fan with the geometrically equivalent tandem row was constructed. The results showed that at the fan rotation frequency of 900 rpm, the sound power level on the first two harmonics is reduced by more than 7 dB. Also, the change in the total sound power level for axial single and tandem fans in the rotation frequency range of 900 to 1,500 rpm was investigated. The fan with the geometrically equivalent tandem blade row has the total sound power level by 6.9...7.4 dB lower than the single fan. The use of the tandem axial fan allows improving acoustic characteristics

Interaction and scattered mode measurement in a mixed bypass/core duct with multiple rotating sources

The rotating rake mode measurement system was developed and implemented at the NASA Glenn Research Center in the 1990s to measure turbofan duct acoustic modes. The system is a radial rake with distributed microphones that is inserted into the duct and continuously rotates about the centerline. The rotating rake mode measurement system provides a complete map of the acoustic duct modes present in a ducted fan and has been used on a variety of test articles: from a low-speed concept test rig to full-scale production turbofan engines. Prior rotating rake mode measurement system measurements have occurred in environments with a single rotating source interacting with a stationary source to produce duct modes at the fan rotor harmonics. A recent test of a scale model high-speed research fan in the NASA 9 × 15 ft Low Speed Wind Tunnel had two rotating sources, a rotor fan and a booster fan, on the same shaft. The interaction of the two rotating sources generated scattering at the harmonic sum and difference tones, and modal scattering at a given fan harmonic. Rotating rake mode measurement system data were acquired from this high-speed fan model which provided a database to allow for validation of the duct mode analysis technique expansion and experimental evidence of the scattering phenomenon. In this paper, modes from the two different sources and associated stationary surfaces from a sample fan condition were reported and compared to analytical predictions, in order to validate the ability of the rotating rake mode measurement system to measure scattered modes. Sample modal content of the booster fan tone and its harmonics tones are presented as well as the sum and difference interaction between the rotor and booster fans.

Geological features, hydrocarbon accumulation and deep water potential of East Indian basins

Abstract Based on the tectonic evolution, sedimentary filling and hydrocarbon geological characteristics, this paper establishes a variety of deep water fan models and accumulation patterns and analyzes exploration potential of deep water area in East Indian basins. Due to the breakup of East Gondwana, the passive continental margins of East India are evolved. The basins in these margins experienced four evolution stages, which include intracratonic rift (P1-T), East Gondwana rift (J1-K1), post-rifted thermal subsidence (K2), and passive continental margin (K3-N). There are three obvious unconformities which were formed in the end stages of post-rift thermal subsidence and first and second phases of passive continental margin. Four sets of structural layers were formed, rift stage, and the first, second and third stages of passive continental marginal structural formation. The main deposition of these basins is the sediments evolved during the passive continental margin stage. Two prolific fan systems were developed: superposition fans are complicated in near shore and delta; low fans are located at fault slope-break while turbidity fans are located in front of delta. Four sets of proven source rocks were developed, the Lower Permian, Lower Cretaceous, Upper Cretaceous and Paleogene. There are many middle porosity reservoirs and lowstand permeability reservoirs, such as sandstone and local carbonate in rift period, sandstone of delta and deep water gravity flow in the rifted thermal subsidence and passive continental margin stages. Many seals were developed in the basins, regional seals in drifted stage and local seals in other stages, and the seals thickness change are enormous. There are eight plays in these basins which include Upper Cretaceous sandstone, Paleogene sandstone, Neogene sandstone, etc. The hydrocarbon exploration of deep water area during the passive continental margin stage should focus on Krishna and Cauvery river delta on the plane, and delta sandstone related to fault, lowstand fan located at fault slope-break and near shore fan complex in vicinity of 85°E ridge and south offshore of Cauvery basin vertically.

Effect of Blade Design Parameters on Air Flow through an Axial Fan

The objective of this paper is the numerical study of the flow through an axial fan and examining the effects of blade design parameters on the performance of the fan. The axial fan is extensively used for cooling of the electronic devices and servers. Simulation of the three-dimensional incompressible turbulent flow was conducted by numerical solution of the (RANS) equations for a model. The SST- k-ω and k-e turbulence models are applied in the simulations which are done using CFX software. The comparison between available experimental data and simulation results indicates that the SST k-ω model gives more accurate results than the k-e model. The results also show that in separation regions and vortices, the pressure will decrease. Hub area and blade root contain large vortices. The effects of changes in the blade geometry and the number of blades on the fan performance are studied in detail. For the primary fan model with the different number of blades (4, 5, and 6), the maximum mass flow rate of 800 CFM is obtained. Hence, the number of blades had negligible effects on the maximum flow rate. By 3o% decreasing in the chord of the blades, the maximum mass flow rate of the fan with the different number of blades (5, 6 and 8) will be reduced to 500 CFM. Therefore, in order to increase the maximum mass flow rate, the chord and the width of blades should be increased. On the other hand, by increasing blades from 4 to 6 in the primary model, the maximum outlet pressure has been increased by 32%. Furthermore, it was found that in high flow rates, an increment in the number of blades had no effect on the produced static pressure.

Aerodynamic optimization of through-flow design model of a high by-pass transonic aero-engine fan using genetic algorithm

This study deals with aerodynamic optimization of a high by-pass transonic aero-engine fan module in a through-flow inverse design model at cruise condition. To the authors’ best knowledge, although the literature contains through-flow optimization of the simplified cases of compressors and turbines, an optimization study targeting the more elaborate case of combined transonic fan and splitter through-flow model is not considered in the literature. Such a through-flow optimization of a transonic fan, combined with bypass and core streams separated by an aerodynamically shaped flow splitter, possesses significant challenges to any optimizer, due to highly non-linear nature of the problem and the high number of constraints, including the fulfillment of the targeted bypass ratio. It is the aim of this study to consider this previously untouched area in detail and therefore present a more sophisticated and accurate optimization environment for actual bypass fan systems. An in-house optimization code using genetic algorithm is coupled with a previously developed in-house through-flow solver which is using a streamline curvature technique and a set of in-house calibrated empirical models for incidence, deviation, loss and blockage. As the through-flow models are the backbone of turbomachinery design, and great majority of design decisions are taken in this phase, such a study is assessed to result in significant guidelines to the gas turbine community.