Search results for: vertical axis wind turbine

Authors: Kaushalendra K. Khadanga, Lee Hee Hyol

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Passenger comfort has been paramount in the design of suspension systems of high speed cars. To analyze the effect of vibration on vehicle ride quality, a vertical model of a six degree of freedom railway passenger vehicle, with front and rear suspension, is built. It includes car body flexible effects and vertical rigid modes. A second order linear shaping filter is constructed to model Gaussian white noise into random rail excitation. The temporal correlation between the front and rear wheels is given by a second order Pade approximation. The complete track and the vehicle model are then designed. An active secondary suspension system based on a Linear Quadratic Gaussian (LQG) optimal control method is designed. The results show that the LQG control method reduces the vertical acceleration, pitching acceleration and vertical bending vibration of the car body as compared to the passive system.

Keywords: active suspension, bending vibration, railway vehicle, vibration control

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Authors: Fahad Qureshi

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This paper provides detailed study on the diagnosis of intermittent high vibration spikes at exhaust bearing (Non-Drive End) of Mitsubishi H-25 gas turbine installed in a petrochemical plant in Pakistan. The diagnosis is followed by successful root cause analysis of the issue and recommendations for improving the reliability of machine. Engro Polymer and Chemicals (EPCL), a Chlor Vinyl complex, has a captive power plant consisting of one combined cycle power plant (CCPP), having two gas turbines each having 25 MW capacity (make: Hitachi) and one extraction condensing steam turbine having 15 MW capacity (make: HTC). Besides, one 6.75 MW SGT-200 1S gas turbine (make: Alstom) is also available. In 2018, the organization faced an issue of intermittent high vibration at exhaust bearing of one of H-25 units having tag GT-2101 A, which eventually led to tripping of machine at configured securities. Since the machine had surpassed 64,000 running hours and major inspection was also due, so bearings inspection was performed. Inspection revealed excessive coke deposition at labyrinth where evidence of rotor rub was also present. Bearing clearance was also at upper limit, and slight babbitt (soft metal) chip off was observed at one of its pads so it was preventively replaced. The unit was restated successfully and exhibited no abnormality until October 2020, when these spikes reoccurred, leading to machine trip. Recurrence of the issue within two years indicated that root cause was not properly addressed, so this paper furthers the discussion on in-depth analysis of findings and establishes successful root cause analysis, which captured significant learnings both in terms of machine design deficiencies and gaps in operation & maintenance (O & M) regime. Lastly, revised O& M regime along with set of recommendations are proposed to avoid recurrence.

Keywords: exhaust side bearing, Gas turbine, rubbing, vibration

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Authors: Ahmed Guerine, Ali El Hafidi, Bruno Martin, Philippe Leclaire

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This paper investigates the nonlinear dynamic response of a mechanical torque limiter which is used to protect drive parts from overload (helical transmission gears). The system is driven by four excitations: two external excitations (aerodynamics torque and force) and two internal excitations (two mesh stiffness fluctuations). In this work, we develop a dynamic model with lumped components and 28 degrees of freedom. We use the Runge Kutta step-by-step time integration numerical algorithm to solve the equations of motion obtained by Lagrange formalism. The numerical results have allowed us to identify the sources of vibration in the wind turbine. Also, they are useful to help the designer to make the right design and correctly choose the times for maintenance.

Keywords: two-stage helical gear, lumped model, dynamic response, torque-limiter

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Authors: Swati Sharma, R. P. Sharma

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We intend to study the nonlinear evolution of the parallel propagating finite frequency Alfvén wave (also called Dispersive Alfvén wave/Hall MHD wave) propagating in the solar wind regime of the solar region when a perpendicularly propagating magnetosonic wave is present in the background. The finite frequency Alfvén wave behaves differently from the usual non-dispersive behavior of the Alfvén wave. To study the nonlinear processes (such as filamentation) taking place in the solar regions such as solar wind, the dynamical equation of both the waves are derived. Numerical simulation involving finite difference method for the time domain and pseudo spectral method for the spatial domain is then performed to analyze the transient evolution of these waves. The power spectra of the Dispersive Alfvén wave is also investigated. The power spectra shows the distribution of the magnetic field intensity of the Dispersive Alfvén wave over different wave numbers. For DAW the spectra shows a steepening for scales larger than the proton inertial length. This means that the wave energy gets transferred to the solar wind particles as the wave reaches higher wave numbers. This steepening of the power spectra can be explained on account of the finite frequency of the Alfvén wave. The obtained results are consistent with the observations made by CLUSTER spacecraft.

Keywords: solar wind, turbulence, dispersive alfven wave

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Authors: Sanpetchuda Krutkrua, Suphawatchara Malanond

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Competition law is not a new thing in Thailand. Thailand first passed the first competition law during the Second World War in order to stop business operator monopolizing food and basic living supplies. The competition law in Thailand has been amended several times during the past eighty years in order to make it suitable for the current economic and social condition. In 2017, Thailand enacted the current Trade Competition Act of B.E. 2560, which contain several changes to the regime in order to enhance a prevention of collusive practices and monopolization through both vertical restraints and horizontal restraints. Section 56 of the Act provides exemptions for the vertical relationship; i.e., the arrangement in form of complementary relationship, between business operators, franchising agreements between franchisor and franchisee, and licensing agreement between licensor and licensee. The key is that such agreements must not be excessive, create monopolization or attempt to monopolize, or cause any impacts the consumers regarding price, quality, quantity of the goods. The goal of the paper is to explore the extent of the exemption under Section 56 and its sequential regulations regarding vertical trade restraints in the case intellectual property licensing. The research will be conducted in form of a comparative analysis on exemptions for collusive practices under the United States Antitrust law and the Thai Competition Act of B.E. 2560. The United Antitrust law, fairly similar to the Thai Competition Act of B.E. 2561, views the intellectual property licensing to have pro-competitive benefits to the market as long as the intellectual property licensing agreement does not harm the competition amongst the business operators that could have or would have been competitors. The United States Antitrust law identifies the relationship between the parties of the agreement whether such agreement is horizontal or vertical or both. Even though the nature of licensing agreements is primarily vertical, the relationship between licensor and licensees can also be horizontal if they could have been potential competitors in the market as well. The United States Antitrust law frowns upon, if not prohibits, the horizontal restraints regarding the intellectual property licensing but does not impose the same restrictions on the vertical trade restraints regarding intellectual property licensing.

Keywords: antitrust, competition law, vertical restraint, intellectual property, intellectual property licensing, comparative law

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Authors: Matthew J. Emes, Azadeh Jafari, Maziar Arjomandi

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Velocity fluctuations of shear-generated turbulence are largest in the atmospheric surface layer (ASL) of nominal 100 m depth, which can lead to dynamic effects such as galloping and flutter on small physical structures on the ground when the turbulence length scales and characteristic length of the physical structure are the same order of magnitude. Turbulence length scales are a measure of the average sizes of the energy-containing eddies that are widely estimated using two-point cross-correlation analysis to convert the temporal lag to a separation distance using Taylor’s hypothesis that the convection velocity is equal to the mean velocity at the corresponding height. Profiles of turbulence length scales in the neutrally-stratified ASL, as predicted by Monin-Obukhov similarity theory in Engineering Sciences Data Unit (ESDU) 85020 for single-point data and ESDU 86010 for two-point correlations, are largely dependent on the aerodynamic roughness length. Field measurements have shown that longitudinal turbulence length scales show significant regional variation, whereas length scales of the vertical component show consistent Obukhov scaling from site to site because of the absence of low-frequency components. Hence, the objective of this experimental study is to compare the similarity theory relationships between the turbulence length scales and aerodynamic roughness length with those calculated using the autocorrelations and cross-correlations of field measurement velocity data at two sites: the Surface Layer Turbulence and Environmental Science Test (SLTEST) facility in a desert ASL in Dugway, Utah, USA and the Commonwealth Scientific and Industrial Research Organisation (CSIRO) wind tower in a rural ASL in Jemalong, NSW, Australia. The results indicate that the longitudinal turbulence length scales increase with increasing aerodynamic roughness length, as opposed to the relationships derived by similarity theory correlations in ESDU models. However, the ratio of the turbulence length scales in the lateral and vertical directions to the longitudinal length scales is relatively independent of surface roughness, showing consistent inner-scaling between the two sites and the ESDU correlations. Further, the diurnal variation of wind velocity due to changes in atmospheric stability conditions has a significant effect on the turbulence structure of the energy-containing eddies in the lower ASL.

Keywords: aerodynamic roughness length, atmospheric surface layer, similarity theory, turbulence length scales

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Authors: Hassan Mohammad Karimi, Ali Salehzade Nobari, Hosein Shahverdi

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With the advancement of technology and the decreasing weight of aerial structures, there is a growing demand for alternative energy sources. Structural vibrations can now be utilized to power low-power sensors for monitoring structural health and charging small batteries in drones. Research on extracting energy from flutter using piezoelectric has been extensive in recent years. This article specifically examines the use of a single-jointed beam with a free surface attached to its free end and a bimorph piezoelectric patch connected to the joint, providing two degrees of torsional and bending freedom. The study investigates the voltage harvested at various wind speeds and bending and twisting stiffness in a wind tunnel. The results indicate that as flutter speed increases, the output voltage also increases to some extent. However, at high wind speeds, the limited cycle created becomes unstable, negatively impacting the harvester's performance. These findings align with other research published in reputable scientific journals.

Keywords: energy harvesting, piezoelectric, flutter, wind tunnel

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Authors: Sladjana Popovic

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The concept of vertical space urbanization, defined in English as "air rights development," can be considered a mechanism for the development of public spaces in urban areas of high density. A chronological overview of the transformation of space within the vertical projection of the existing traffic infrastructure that penetrates through the central areas of a city is given in this paper through the analysis of two illustrative case studies: more advanced and recent - "Plot 13" in Boston, and less well-known European example of structures erected above highways throughout Italy - the "Pavesi auto grill" chain. The backbone of this analysis is the examination of the possibility of yielding air rights within the vertical projection of public structures in the two examples by considering the factors that would enable its potential application in capitals in Southeastern Europe. The cession of air rights in the Southeastern Europe region, as a phenomenon, has not been a recognized practice in urban planning. In a formal sense, legal and physical feasibility can be seen to some extent in local models of structures built above protected historical heritage (i.e., archaeological sites); however, the mechanisms of the legal process of assigning the right to use and develop air rights above public structures is not a recognized concept. The goal of the analysis is to shed light on the influence of institutional participants in the implementation of innovative solutions for vertical urbanization, as well as strategic planning mechanisms in public-private partnership models that would enable the implementation of the concept in the region. The main question is whether the manipulation of the vertical projection of space could provide for innovative urban solutions that overcome the deficit and excessive use of the available construction land, particularly above the dominant public spaces and traffic infrastructure that penetrate central parts of a city. Conclusions reflect upon vertical urbanization that can bridge the spatial separation of the city, reduce noise pollution and contribute to more efficient urban planning along main transportation corridors.

Keywords: air rights development, innovative urbanism, public-private partnership, transport infrastructure, vertical urbanization

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Authors: K. Doi, T. Nishimura, H. Fujimoto

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The number of people who become visually impaired and do not have sufficient tactile experiences has increased by various disease. Especially, many acquired visually impaired persons due to accidents, disorders, and aging cannot adequately read Braille. It is known that learning Braille requires a great deal of time and the acquisition of various skills. In our previous studies, we reported one of the problems in learning Braille. Concretely, the standard Braille size is too small for Braille beginners. And also we are short of the objective data regarding easily readable Braille size. Therefore, it is necessary to conduct various experiments for evaluating Braille size that would make learning easier for beginners. In this study, for the purpose of investigating easy-to-read conditions of vertical and horizontal dot spacing for beginners, we conducted one Braille reading experiment. In this our experiment, we prepared test pieces by use of our original Braille printer with controlling function of Braille size. We specifically considered Braille beginners with acquired visual impairments who were unfamiliar with Braille. Therefore, ten sighted subjects with no experience of reading Braille participated in this experiment. Size of vertical and horizontal dot spacing was following conditions. Each dot spacing was 2.0, 2.3, 2.5, 2.7, 2.9, 3.1mm. The subjects were asked to read one Braille character with controlled Braille size. The results of this experiment reveal that Braille beginners can read Braille accurately and quickly when both vertical and horizontal dot spacing are 3.1 mm or more. This knowledge will be helpful data in considering Braille size for acquired visually impaired persons.

Keywords: paper-based Braille, vertical and horizontal dot spacing, readability, acquired visual impairment, Braille beginner

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Authors: Fereshteh Akbari, Farrokh Jalali Mosalam, Ali Hedayatifar, Amirreza Aminjavaheri

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The soil nailing is an effective method to stabilize slopes and retaining structures. Consequently, the lateral and vertical displacement of retaining walls are important criteria to evaluate the safety risks of adjacent structures. This paper is devoted to the optimization problems of retaining walls based on ABAQOUS Software. The various parameters such as nail length, orientation, arrangement, horizontal spacing, and bond skin friction, on lateral and vertical displacement of retaining walls are investigated. In order to ensure accuracy, the mobilized shear stress acting around the perimeter of the nail-soil interface is also modeled in ABAQOUS software. The observed trend of results is compared to the previous researches.

Keywords: retaining walls, soil nailing, ABAQOUS software, lateral displacement, vertical displacement

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Authors: P. B. Sob, T. B. Tengen, A. A. Alugongo

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Mechanical behavior of 6082T6 aluminum is investigated at different temperatures. The strain rate sensitivity is investigated at different temperatures on the grain size variants. The sensitivity of the measured grain size variants on 3-D grain is discussed. It is shown that the strain rate sensitivities are negative for the grain size variants during the deformation of nanostructured materials. It is also observed that the strain rate sensitivities vary in different ways with the equivalent radius, semi minor axis radius, semi major axis radius and major axis radius. From the obtained results, it is shown that the variation of strain rate sensitivity with temperature suggests that the strain rate sensitivity at the low and the high temperature ends of the 6082T6 aluminum range is different. The obtained results revealed transition at different temperature from negative strain rate sensitivity as temperature increased on the grain size variants.

Keywords: nanostructured materials, grain size variants, temperature, yield stress, strain rate sensitivity

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Authors: Young-Kwan Choi, Gang-Wook Shin, Sung-Taek Hong

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Water supply system consumes large amount of power load during water treatment and transportation of purified water. Many energy conserving high efficiency materials such as DC motor and LED light have recently been introduced to water supply system for energy conservation. This paper performed empirical analysis on BLDC, AC motors, and comparatively analyzed the change in power according to DC power supply ratio in order to conserve energy of a next-generation water treatment system called vertical water treatment system. In addition, a DC distribution system linked with photovoltaic generation was simulated to analyze the energy conserving effect of DC load.

Keywords: vertical water treatment system, DC power supply, energy efficiency, BLDC

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Authors: Noraishah Othman, Siti K. Kamarudin, Norinsan K. Othman, Mohd S. Takriff, Masli I. Rosli, Engku M. Fahmi, Mior A. Khusaini

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The present work describes hydrodynamics of mixing characteristics of two dual hybrid impeller consisting of, radial and axial impeller using radiotracer technique. Type A mixer, a Rushton turbine is mounted above a Pitched Blade Turbine (PBT) at common shaft and Type B mixer, a Rushton turbine is mounted below PBT. The objectives of this paper are to investigate the residence time distribution (RTD) of two hybrid mixers and to represent the respective mixers by RTD model. Each type of mixer will experience five radiotracer experiments using Tc99m as source of tracer and scintillation detectors NaI(Tl) are used for tracer detection. The results showed that mixer in parallel model and mixers in series with exchange can represent the flow model in mixer A whereas only mixer in parallel model can represent Type B mixer well than other models. In conclusion, Type A impeller, Rushton impeller above PBT, reduced the presence of dead zone in the mixer significantly rather than Type B.

Keywords: hybrid impeller, residence time distribution (RTD), radiotracer experiments, RTD model

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Authors: Dmitry Fedoseyev

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The ultimate success of unmanned aerial vehicles (UAVs) depends largely on the effective control of their flight, especially in variable wind conditions. This paper investigates different approaches to selecting the optimal flight level to maximize the range of UAVs. We propose to consider methods based on mathematical models of atmospheric conditions, as well as the use of sensor data and machine learning algorithms to automatically optimize the flight level in real-time. The proposed approaches promise to improve the efficiency and range of UAVs in various wind conditions, which may have significant implications for the application of these systems in various fields, including geodesy, environmental surveillance, and search and rescue operations.

Keywords: drone, UAV, flight trajectory, wind-searching, efficiency

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Authors: Shidvash Vakilipour, Mehdi Habibnia, Rouzbeh Riazi, Masoud Mohammadi, Mohammad H. Sabour

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The flow field passing through a highly loaded low pressure (LP) turbine cascade is numerically investigated at design and off-design conditions. The Field Operation And Manipulation (OpenFOAM) platform is used as the computational Fluid Dynamics (CFD) tool. Firstly, the influences of grid resolution on the results of k-ε, k-ω, and LES turbulence models are investigated and compared with those of experimental measurements. A numerical pressure under-shoot is appeared near the end of blade pressure surface which is sensitive to grid resolution and flow turbulence modeling. The LES model is able to resolve separation on a coarse and fine grid resolutions. Secondly, the off-design flow condition is modeled by negative and positive inflow incidence angles. The numerical experiments show that a separation bubble generated on blade pressure side is predicted by LES. The total pressure drop is also been calculated at incidence angle between -20◦ and +8◦. The minimum total pressure drop is obtained by k-ω and LES at the design point.

Keywords: low pressure turbine, off-design performance, openFOAM, turbulence modeling, flow separation

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Authors: Luis Lara-Valencia, Mateo Ramirez-Acevedo, Daniel Caicedo, Jose Brito, Yosef Farbiarz

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Controlling wind-induced vibrations as well as aerodynamic forces, is an essential part of the structural design of tall buildings in order to guarantee the serviceability limit state of the structure. This paper presents a numerical investigation on the optimal design parameters of a Tuned Inerter Damper (TID) based system for the control of wind-induced vibration in tall buildings. The control system is based on the conventional TID, with the main difference that its location is changed from the ground level to the last two story-levels of the structural system. The TID tuning procedure is based on an evolutionary cultural algorithm in which the optimum design variables defined as the frequency and damping ratios were searched according to the optimization criteria of minimizing the root mean square (RMS) response of displacements at the nth story of the structure. A Monte Carlo simulation was used to represent the dynamic action of the wind in the time domain in which a time-series derived from the Davenport spectrum using eleven harmonic functions with randomly chosen phase angles was reproduced. The above-mentioned methodology was applied on a case-study derived from a 37-story prestressed concrete building with 144 m height, in which the wind action overcomes the seismic action. The results showed that the optimally tuned TID is effective to reduce the RMS response of displacements up to 25%, which demonstrates the feasibility of the system for the control of wind-induced vibrations in tall buildings.

Keywords: evolutionary cultural algorithm, Monte Carlo simulation, tuned inerter damper, wind-induced vibrations

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Authors: Ashima Rai

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CATV transmission systems have altered from old cable based one-way analog video transmission to two ways hybrid fiber transmission. The use of optical fiber reduces the RF amplifiers in the transmission, high transmission power or lower fiber transmission losses are required to increase system capability. This paper evaluates and compares Distributed Feedback (DFB) laser and Vertical Cavity Surface Emitting Laser (VCSEL) for CATV transmission. The simulation results exhibit the better performer among both lasers taking into consideration the parameters chosen for evaluation.

Keywords: Distributed Feedback (DFB), Vertical Cavity Surface Emitting Laser (VCSEL), Community Access Television (CATV), Composite Second Order (CSO), Composite Triple Beat (CTB), RF

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Authors: R. Pillai Aparna, S. R. Gandhi

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Soft clay deposits having low strength and high compressibility are found all over the world. Preloading with vertical drains is a widely used method for improving such type of soils. The coefficient of consolidation, irrespective of the drainage type, plays an important role in the design of vertical drains and it controls accurate prediction of the rate of consolidation of soil. Also, the increase in shear strength of soil with consolidation is another important factor considered in preloading or staged construction. To our best knowledge no clear guidelines are available to estimate the increase in shear strength for a particular degree of consolidation (U) at various stages during the construction. Various methods are available for finding out the consolidation coefficient. This study mainly focuses on the variation of, consolidation coefficient which was found out using different methods and shear strength with pressure intensity. The variation of shear strength with the degree of consolidation was also studied. The consolidation test was done using two types of highly compressible clays with vertical, radial and a few with combined drainage. The test was carried out at different pressures intensities and for each pressure intensity, once the target degree of consolidation is achieved, vane shear test was done at different locations in the sample, in order to determine the shear strength. The shear strength of clayey soils under the application of vertical stress with vertical and radial drainage with target U value of 70% and 90% was studied. It was found that there is not much variation in cv or cr value beyond 80kPa pressure intensity. Correlations were developed between shear strength ratio and consolidation pressure based on laboratory testing under controlled condition. It was observed that the shear strength of sample with target U value of 90% is about 1.4 to 2 times than that of 70% consolidated sample. Settlement analysis was done using Asaoka’s and hyperbolic method. The variation of strength with respect to the depth of sample was also studied, using large-scale consolidation test. It was found, based on the present study that the gain in strength is more on the top half of the clay layer, and also the shear strength of the sample ensuring radial drainage is slightly higher than that of the vertical drainage.

Keywords: consolidation coefficient, degree of consolidation, PVDs, shear strength

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Authors: Kumars ZandParsa, Quynh Nguyen, Hadi Moradi

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There are old cast-in-place concrete box girder bridges in California with inter-span hinges that are designed based on old earthquake codes. Hinge removal is part of the bridges’ earthquake retrofitting project, and hinges were removed and replaced with modified hinges per new earthquake codes. The span that has a hinge is divided into short and long cantilevers in which the short cantilever supports the long cantilever. In the recent bridge hinge replacement, the length of the short and long cantilevers were 20ft and 80ft, respectively. The seat in the new design is wider than the old design, and the horizontal and vertical movements of the deck at the hinge location must be computed to check if restraints are needed. In this paper, besides considering the conventional reinforced concrete box girder bridges, the hinge removal operations, along with the response spectrum analysis based on the El Centro 1940 earthquake, will be presented to verify if vertical and horizontal restrainers are needed.

Keywords: hinge replacement, restrainers, vertical earthquake, response spectrum analysis

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Authors: Kartik Gupta, Umar Khan, Mayur Parab, Dhiraj Chaudhari, Afzal Ansari

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The report focuses on the study related to the Design and Simulation of a stabilator (an all-movable horizontal stabilizer) for a fixed-wing aircraft. The project involves the development of a computerized direct optimization procedure for designing an aircraft all-movable stabilator. This procedure evaluates various design variables to synthesize an optimal stabilator that meets specific requirements, including performance, control, stability, strength, and flutter velocity constraints. The work signifies the CFD (Computational Fluid Dynamics) analysis of the airfoils used in the stabilator along with the CFD analysis of the Stabilizer and Stabilator of an aircraft named Thorp- T18 in software like XFLR5 and ANSYS-Fluent. A comparative analysis between a Stabilizer and Stabilator of equal surface area and under the same environmental conditions was done, and the percentage of drag reduced by the Stabilator for the same amount of lift generated as the Stabilizer was also calculated lastly, Wind tunnel testing was performed on a scale down model of the Stabilizer and Stabilator and the results of the Wind tunnel testing were compared with the results of CFD.

Keywords: wind tunnel testing, CFD, stabilizer, stabilator

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Authors: Mohamed M. A. Abumandour

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The red swamp freshwater crayfish breathe through three types of feather-like trichobranchiate gills; podobranchiae, arthrobranchiae and pleurobranchiae. All gills have the same general structure and appearance; plume-like with single broad setiferous, and single axis. The gill consists of axis with numerous finger-like filaments, having three morphological types; round, pointed and somewhat hooked shaped. The direction of filaments vary according their position; in middle region were nearly perpendicular to gill axis while in the apex were nearly parallel to axis. There were characteristic system of gill spines on; central axis (two types were distinguishable by presence of socket), basal plate, setobranch (long non-branched and short multidenticulate) and on the bilobed epipodal plate. There are four shape of spinated-like distal region of setobranch seta; two pointed processes (longitudinal arrangement and irregular arranged) and two broad processes (transverse triangular and multidenticulate). The bilobed epipodal plate devoid from any filaments and extended from outer side of podobranchiae as triangular basal part then extended between the gills as cord-like middle part then pass under the gill to lies against the thoracic body wall. By SEM, the apical part of bilobed epipodal plate have serrated free border and corrugated surface while the middle part have none serrated free border. There are two methods of gill cleaning mechanism in crayfish; passive and active method. The passive method occurred by; setae of setobranch, branchiostegite, bilobed epipodal plate, setiferous arthrodial lamellae and reversing the respiratory water through a narrow spaced branchial chamber.

Keywords: crayfis, gill spines, setobranch, gill setae, cleaning mechanisms

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Authors: Varun K, Pramod B. Balareddy

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Estimation of wind forces plays a significant role in the in the design of large antenna parabolic reflectors. Reflector surface accuracies are very sensitive to the gain of the antenna system at higher frequencies. Hence accurate estimation of wind forces becomes important, which is primary input for design and analysis of the reflector system. In the present work, numerical simulation of wind flow using Computational Fluid Dynamics (CFD) software is used to investigate the external pressure coefficients. An extensive comparative study has been made between the CFD results and the published wind tunnel data for different wind angle of attacks (α) acting over concave to convex surfaces respectively. Flow simulations using CFD are carried out to estimate the coefficients of Drag, Lift and Moment for the parabolic reflector. Coefficients of pressures (Cp) over the front and the rear face of the reflector are extracted over surface of the reflector to study the net pressure variations. These resultant pressure variations are compared with the published wind tunnel data for different angle of attacks. It was observed from the CFD simulations, both convex and concave face of reflector system experience a band of pressure variations for the positive and negative angle of attacks respectively. In the published wind tunnel data, Pressure variations over convex surfaces are assumed to be uniform and vice versa. Chordwise and spanwise pressure variations were calculated and compared with the published experimental data. In the present work, it was observed that the maximum pressure coefficients for α ranging from +30° to -90° and α=+90° was lower. For α ranging from +45° to +75°, maximum pressure coefficients were higher as compared to wind tunnel data. This variation is due to non-uniform pressure distribution observed over front and back faces of reflector. Variations in Cd, Cl and Cm over α=+90° to α=-90° was in close resemblance with the experimental data.

Keywords: angle of attack, drag coefficient, lift coefficient, pressure coefficient

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Authors: Bhavesh N. Bhatt, Zozimus D. Labana

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This work is mainly focused on the analysis of heat transfer of blade by using internal cooling method. By using conjugate heat transfer technology we can effectively compute the cooling and heat transfer analysis of blade. Here blade temperature is limited by materials melting temperature. By using CFD code, we will analyze the blade cooling with the help of CHT method. There are two types of CHT methods. In the first method, we apply coupled CHT method in which all three domains modeled at once, and in the second method, we will first model external domain and then, internal domain of cooling channel. Ten circular cooling channels are used as a cooling method with different mass flow rate and temperature value. This numerical simulation is applied on NASA C3X turbine blade, and results are computed. Here results are showing good agreement with experimental results. Temperature and pressure are high at the leading edge of the blade on stagnation point due to its first faces the flow. On pressure side, shock wave is formed which also make a sudden change in HTC and other parameters. After applying internal cooling, we are succeeded in reducing the metal temperature of blade by some extends.

Keywords: gas turbine, conjugate heat transfer, NASA C3X Blade, circular film cooling channel

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Authors: Chaitanya R. Mali, V. Vinod, Ashwin W. Patwardhan

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Design of long vertical steam generator (SG) tubes in nuclear power plant involves an understanding of different aspects of flow boiling phenomenon such as flow instabilities, flow regimes, dry out, critical heat flux, pressure drop, etc. The knowledge of the prediction of local thermal hydraulic characteristics is necessary to understand these aspects. For this purpose, the methodology has been developed which covers all the flow boiling regimes to model full range flow boiling phenomenon. In this methodology, the vertical tube is divided into four sections based on vapor fraction value at the end of each section. Different modeling strategies have been applied to the different sections of the vertical tube. Computational fluid dynamics simulations have been performed on a vertical SG tube of 0.0126 m inner diameter and 23 m length. The thermal hydraulic parameters such as vapor fraction, liquid temperature, heat transfer coefficient, pressure drop, heat flux distribution have been analyzed for different designed heat duties (1.1 MW (20%) to 3.3 MW (60%)) and flow conditions (10 % to 80 %). The sensitivity of different boiling parameters such as bubble departure diameter, nucleation site density, bubble departure frequency on the thermal hydraulic parameters was also studied. Flow instability has been observed at 20 % designed heat duty and 20 % flow conditions.

Keywords: thermal hydraulics, boiling, vapor fraction, sensitivity

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Authors: Joon-Yeop Na, Sang-Keun Baik, Kyu-Soo Chong

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Road sign sizes are related to their support and foundation, and the large-scale support that is generally installed at roadsides can cause inconvenience to pedestrians and damage the urban landscape. The most influential factor in determining the support and foundation of road signs is the wind load. In this study, we introduce a hole-type road sign to analyze its effects on reducing wind load. A hole-type road sign reduces the drag coefficient that is applied when considering the air and fluid resistance of a plate when the wind pressure is calculated, thus serving as an effective option for lightening the weights of road sign structures. A hole-type road sign is punctured with a perforator. Furthermore, the size of the holes and their distance is determined considering the damage to characters, the poor performance of reflective sheets, and legibility. For the calculation of the optimal specification of a hole-type road sign, we undertook a theoretical examination for reducing the wind loads on hole-type road signs, and analyzed the bending and reflectivity of sample road sign plates. The analytic results confirmed that a hole-type road sign sample that contains holes of 6 mm in diameter with a distance of 18 mm between the holes shows reflectivity closest to that of existing road signs; moreover, the average bending moment resulted in a reduction of 4.24%, and the support’s diameter is reduced by 40.2%.

Keywords: hole type, road sign, weight lightening, wind load

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Authors: Mohammad F. Fauzi, Nurul H. Shahba M. Shahrun, Nurul W. Hamzah, Mohd Noah A. Rahman, Afzaal H. Seyal

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In this paper, we proposed a simulation system using Wireless Sensor Network (WSN) that will be distributed around the forest for early forest fire detection and to locate the areas affected. In Brunei Darussalam, approximately 78% of the nation is covered by forest. Since the forest is Brunei’s most precious natural assets, it is very important to protect and conserve our forest. The hot climate in Brunei Darussalam can lead to forest fires which can be a fatal threat to the preservation of our forest. The process consists of getting data from the sensors, analyzing the data and producing an alert. The key factors that we are going to analyze are the surrounding temperature, wind speed and wind direction, humidity of the air and soil.

Keywords: forest fire monitor, humidity, wind direction, wireless sensor network

Procedia PDF Downloads 445

Authors: N. N. Orlova, A. S. Aronin, Yu. P. Kabanov, S. I. Bozhko, V. S. Gornakov

Abstract:

We have investigated the change of the magnetic structure and the hysteresis properties of iron-based microwires after decreasing levels of internal mechanical stresses. The magnetic structure was investigated by the method of magneto-optical indicator film and the method of magnetic force microscopy. The hysteresis properties were studied by the vibrating sample magnetometer. The stresses were decreased by removing the glass coat and/or by low-temperature isothermal annealing. Previously, the authors carried out experimentally investigation of the magnetic structure of Fe-based microwire using these methods. According to the obtained results the domain structure of a microwire with a positive magnetostriction is composed of the inner cylindrical domains with the magnetization along the wire axis and the surface layer of the ring shape domains with the radial direction of magnetization. Surface ring domains with opposite magnetization direction (i.e., to the axis or from the axis) alternate with each other. For the first time the size of magnetic domains was determined experimentally. In this study it was found that in the iron-based microwires the value of the coercive force can be reduce more than twice by decreasing levels of internal mechanical stresses. Decrease of the internal stress value by the relaxation annealing influence on the magnetic structure. So in the as-prepared microwires observed local deviations of the magnetization of the magnetic core domains from the axis of the wire. After low-temperature annealing the local deviations of magnetization is not observed.

Keywords: amorphous microwire, magnetic structure, internal stress, hysteresis properties, ferromagnetic

Procedia PDF Downloads 559

Authors: M. A. At-Tasneem, N. T. Rao, T. M. Y. S. Tuan Ya, M. S. Idris, M. Ammar

Abstract:

River flow over micro hydro power (MHP) turbines of multiple arrays arrangement is simulated with computational fluid dynamics (CFD) software to obtain the flow characteristics. In this paper, CFD software is used to simulate the water flow over MHP turbines as they are placed in a river. Multiple arrays arrangement of MHP turbines lead to generate large amount of power. In this study, a river model is created and simulated in CFD software to obtain the water flow characteristic. The process then continued by simulating different types of arrays arrangement in the river model. A MHP turbine model consists of a turbine outer body and static propeller blade in it. Five types of arrangements are used which are parallel, series, triangular, square and rhombus with different spacing sizes. The velocity profiles on each MHP turbines are identified at the mouth of each turbine bodies. This study is required to obtain the arrangement with increasing spacing sizes that can produce highest power density through the water flow variation.

Keywords: micro hydro power, CFD, arrays arrangement, spacing sizes, velocity profile, power

Procedia PDF Downloads 353

Authors: Aka S. Koffi, N’Goran Yao, Philippe Bastide, Denis Bruneau, Diby Kadjo

Abstract:

Cocoa beans (Theobroma cocoa L.) are the main components for chocolate manufacturing. The beans must be correctly fermented at first. Traditional process to perform the first fermentation (lactic fermentation) often consists in confining cacao beans using banana leaves or a fermentation basket, both of them leading to a poor product thermal insulation and to an inability to mix the product. Box fermenter reduces this loss by using a wood with large thickness (e>3cm), but mixing to homogenize the product is still hard to perform. Automatic fermenters are not rentable for most of producers. Heat (T>45°C) and acidity produced during the fermentation by microbiology activity of yeasts and bacteria are enabling the emergence of potential flavor and taste of future chocolate. In this study, a cylindro-rotative fermenter (FCR-V1) has been built and coconut fibers were used in its structure to confine heat. An axis of rotation (360°) has been integrated to facilitate the turning and homogenization of beans in the fermenter. This axis permits to put fermenter in a vertical position during the anaerobic alcoholic phase of fermentation, and horizontally during acetic phase to take advantage of the mid height filling. For circulation of air flow during turning in acetic phase, two woven rattan with grid have been made, one for the top and second for the bottom of the fermenter. In order to reduce air flow during acetic phase, two airtight covers are put on each grid cover. The efficiency of the turning by this kind of rotation, coupled with homogenization of the temperature, caused by the horizontal position in the acetic phase of the fermenter, contribute to having a good proportion of well-fermented beans (83.23%). In addition, beans’pH values ranged between 4.5 and 5.5. These values are ideal for enzymatic activity in the production of the aromatic compounds inside beans. The regularity of mass loss during all fermentation makes it possible to predict the drying surface corresponding to the amount being fermented.

Keywords: cocoa fermentation, fermenter, microbial activity, temperature, turning

Procedia PDF Downloads 254

Authors: Sepideh Samadzadehyazdi, Mohammad Javad Khalili, Sarvenaz Samadzadehyazdi, Mohammad Javad Mahdavinejad

Abstract:

The term ‘Windphil Architecture’ refers to the building that facilitates natural ventilation by architectural elements. Natural ventilation uses the natural forces of wind pressure and stacks effect to direct the movement of air through buildings. Natural ventilation is increasingly being used in contemporary buildings to minimize the consumption of non-renewable energy and it is an effective way to improve indoor air quality. The main objective of this paper is to identify the strategies of using natural ventilation in Iranian modern buildings. In this regard, the research method is ‘descriptive-analytical’ that is based on comparative techniques. To simulate wind flow in the interior spaces of case studies, FLUENT software has been used. Research achievements show that it is possible to use natural ventilation to create a thermally comfortable indoor environment. The natural ventilation strategies could be classified into two groups of environmental characteristics such as public space structure, and architectural characteristics including building form and orientation, openings, central courtyards, wind catchers, roof, wall wings, semi-open spaces and the heat capacity of materials. Having investigated modern buildings of Iran, innovative elements like wind catchers and wall wings are less used than the traditional architecture. Instead, passive ventilation strategies have been more considered in the building design as for the roof structure and openings.

Keywords: natural ventilation strategies, wind catchers, wind flow, Iranian modern buildings

Procedia PDF Downloads 330