Search results for: general flow shop scheduling problem
14651 Heat Transfer Dependent Vortex Shedding of Thermo-Viscous Shear-Thinning Fluids
Authors: Markus Rütten, Olaf Wünsch
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Non-Newtonian fluid properties can change the flow behaviour significantly, its prediction is more difficult when thermal effects come into play. Hence, the focal point of this work is the wake flow behind a heated circular cylinder in the laminar vortex shedding regime for thermo-viscous shear thinning fluids. In the case of isothermal flows of Newtonian fluids the vortex shedding regime is characterised by a distinct Reynolds number and an associated Strouhal number. In the case of thermo-viscous shear thinning fluids the flow regime can significantly change in dependence of the temperature of the viscous wall of the cylinder. The Reynolds number alters locally and, consequentially, the Strouhal number globally. In the present CFD study the temperature dependence of the Reynolds and Strouhal number is investigated for the flow of a Carreau fluid around a heated cylinder. The temperature dependence of the fluid viscosity has been modelled by applying the standard Williams-Landel-Ferry (WLF) equation. In the present simulation campaign thermal boundary conditions have been varied over a wide range in order to derive a relation between dimensionless heat transfer, Reynolds and Strouhal number. Together with the shear thinning due to the high shear rates close to the cylinder wall this leads to a significant decrease of viscosity of three orders of magnitude in the nearfield of the cylinder and a reduction of two orders of magnitude in the wake field. Yet the shear thinning effect is able to change the flow topology: a complex K´arm´an vortex street occurs, also revealing distinct characteristic frequencies associated with the dominant and sub-dominant vortices. Heating up the cylinder wall leads to a delayed flow separation and narrower wake flow, giving lesser space for the sequence of counter-rotating vortices. This spatial limitation does not only reduce the amplitude of the oscillating wake flow it also shifts the dominant frequency to higher frequencies, furthermore it damps higher harmonics. Eventually the locally heated wake flow smears out. Eventually, the CFD simulation results of the systematically varied thermal flow parameter study have been used to describe a relation for the main characteristic order parameters.Keywords: heat transfer, thermo-viscous fluids, shear thinning, vortex shedding
Procedia PDF Downloads 29714650 Numerical Analysis of Laminar Reflux Condensation from Gas-Vapour Mixtures in Vertical Parallel Plate Channels
Authors: Foad Hassaninejadafarahani, Scott Ormiston
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Reflux condensation occurs in a vertical channels and tubes when there is an upward core flow of vapor (or gas-vapor mixture) and a downward flow of the liquid film. The understanding of this condensation configuration is crucial in the design of reflux condensers, distillation columns, and in loss-of-coolant safety analyses in nuclear power plant steam generators. The unique feature of this flow is the upward flow of the vapor-gas mixture (or pure vapor) that retards the liquid flow via shear at the liquid-mixture interface. The present model solves the full, elliptic governing equations in both the film and the gas-vapor core flow. The computational mesh is non-orthogonal and adapts dynamically the phase interface, thus produces sharp and accurate interface. Shear forces and heat and mass transfer at the interface are accounted for fundamentally. This modeling is a big step ahead of current capabilities by removing the limitations of previous reflux condensation models which inherently cannot account for the detailed local balances of shear, mass, and heat transfer at the interface. Discretisation has been done based on a finite volume method and a co-located variable storage scheme. An in-house computer code was developed to implement the numerical solution scheme. Detailed results are presented for laminar reflux condensation from steam-air mixtures flowing in vertical parallel plate channels. The results include velocity and pressure profiles, as well as axial variations of film thickness, Nusselt number and interface gas mass fraction.Keywords: Reflux, Condensation, CFD-Two Phase, Nusselt number
Procedia PDF Downloads 36414649 Optimization of Tangential Flow Filtration Process for Purifying DNA Vaccine
Authors: Piyakajornkul T., Noppiboon S., Hochareon L., Kitsubun P.
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Nowadays, DNA vaccines become an interesting subject in the third vaccine generation. The platform of DNA vaccines production has been developed and its downstream process becomes challenging due to the quality of the products in terms of purity and percentage of supercoiled DNA. To overcome these challenges, tangential flow filtration (TFF), which is involved in the purification process, could be used since it provides effective separation of impurity prior to performing further purification steps. However, operating conditions of TFF is varied based on several factors such as sizes of target particle and impurities, a concentration of solution as well as a concentration polarization on the membrane surface. In this study, pVAX1/lacZ was used as a model of TFF optimization in order to prevent a concentration polarization that can lead to the membrane fouling and also minimize a diafiltration volume while maintaining the maximum permeate flux resulting in proper operating times and buffer volume. By using trans membrane pressure (TMP) excursion method, feed flow rates and TMP were varied. The results showed a correlation of permeate flux with TMP where the maximum volume concentration factor reached 2.5 times of the initial volume when feed flow rate and TMP were 7 liters/m²/min and 1 bar, respectively. It was optimal operating conditions before TFF system undergone pressure independent regime. In addition, the diafiltration volume was 14 times of the concentrated volume prior to performing a further anion chromatography process.Keywords: concentration polarization, DNA vaccines, optimization, permeate flux, pressure dependent, tangential flow filtration (TFF), trans membrane pressure (TMP)
Procedia PDF Downloads 15914648 Drug Therapy Problems and Associated Factors among Patients with Heart Failure in the Medical Ward of Arba Minch General Hospital, Ethiopia
Authors: Debalke Dale, Bezabh Geneta, Yohannes Amene, Yordanos Bergene, Mohammed Yimam
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Background: A drug therapy problem (DTP) is an event or circumstance that involves drug therapies that actually or potentially interfere with the desired outcome and requires professional judgment to resolve. Heart failure is an emerging worldwide threat whose prevalence and health loss burden constantly increase, especially in the young and in low-to-middle-income countries. There is a lack of population-based incidence and prevalence of heart failure (HF) studies in sub-Saharan African countries, including Ethiopia. Objective: The aim of this study was designed to assess drug therapy problems and associated factors among patients with HF in the medical ward of Arba Minch General Hospital(AGH), Ethiopia, from June 5 to August 20, 2022. Methods: A retrospective cross-sectional study was conducted among 180 patients with HF who were admitted to the medical ward of AGH. Data were collected from patients' cards by using questionnaires. The data were categorized and analyzed by using SPSS version 25.0 software, and data were presented in tables and words based on the nature of the data. Result: Out of the total, 85 (57.6%) were females, and 113 (75.3%) patients were aged over fifty years. Of the 150 study participants, 86 (57.3%) patients had at least one DTP identified, and a total of 116 DTPs were identified, which is 0.77 DTPs per patient. The most common types of DTP were unnecessary drug therapy (32%), followed by the need for additional drug therapy (36%), and dose too low (15%). Patients who used polypharmacy were 5.86 (AOR) times more likely to develop DTPs than those who did not (95% CI = 1.625–16.536, P = 0.005), and patients with more co-morbid conditions developed 3.68 (AOR) times more DTPs than those who had fewer co-morbidities (95% CI = 1.28–10.5, P = 0.015). Conclusion: The results of this study indicated that drug therapy problems were common among medical ward patients with heart failure. These problems are adversely affecting the treatment outcomes of patients, so it requires the special attention of healthcare professionals to optimize them.Keywords: heart failure, drug therapy problems, Arba Minch general hospital, Ethiopia
Procedia PDF Downloads 10714647 Augmented Reality for Maintenance Operator for Problem Inspections
Authors: Chong-Yang Qiao, Teeravarunyou Sakol
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Current production-oriented factories need maintenance operators to work in shifts monitoring and inspecting complex systems and different equipment in the situation of mechanical breakdown. Augmented reality (AR) is an emerging technology that embeds data into the environment for situation awareness to help maintenance operators make decisions and solve problems. An application was designed to identify the problem of steam generators and inspection centrifugal pumps. The objective of this research was to find the best medium of AR and type of problem solving strategies among analogy, focal object method and mean-ends analysis. Two scenarios of inspecting leakage were temperature and vibration. Two experiments were used in usability evaluation and future innovation, which included decision-making process and problem-solving strategy. This study found that maintenance operators prefer build-in magnifier to zoom the components (55.6%), 3D exploded view to track the problem parts (50%), and line chart to find the alter data or information (61.1%). There is a significant difference in the use of analogy (44.4%), focal objects (38.9%) and mean-ends strategy (16.7%). The marked differences between maintainers and operators are of the application of a problem solving strategy. However, future work should explore multimedia information retrieval which supports maintenance operators for decision-making.Keywords: augmented reality, situation awareness, decision-making, problem-solving
Procedia PDF Downloads 23014646 Partially-Averaged Navier-Stokes for Computations of Flow Around Three-Dimensional Ahmed Bodies
Authors: Maryam Mirzaei, Sinisa Krajnovic´
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The paper reports a study about the prediction of flows around simplified vehicles using Partially-Averaged Navier-Stokes (PANS). Numerical simulations are performed for two simplified vehicles: A slanted-back Ahmed body at Re=30 000 and a square back Ahmed body at Re=300 000. A comparison of the resolved and modeled physical flow scales is made with corresponding LES and experimental data for a better understanding of the performance of the PANS model. The PANS model is compared for coarse and fine grid resolutions and it is indicated that even a coarse-grid PANS simulation is able to produce fairly close flow predictions to those from a well-resolved LES simulation. The results indicate the possibility of improvement of the predictions by employing a finer grid resolution.Keywords: partially-averaged Navier-Stokes, large eddy simulation, PANS, LES, Ahmed body
Procedia PDF Downloads 60014645 Sand Production Modelled with Darcy Fluid Flow Using Discrete Element Method
Authors: M. N. Nwodo, Y. P. Cheng, N. H. Minh
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In the process of recovering oil in weak sandstone formations, the strength of sandstones around the wellbore is weakened due to the increase of effective stress/load from the completion activities around the cavity. The weakened and de-bonded sandstone may be eroded away by the produced fluid, which is termed sand production. It is one of the major trending subjects in the petroleum industry because of its significant negative impacts, as well as some observed positive impacts. For efficient sand management therefore, there has been need for a reliable study tool to understand the mechanism of sanding. One method of studying sand production is the use of the widely recognized Discrete Element Method (DEM), Particle Flow Code (PFC3D) which represents sands as granular individual elements bonded together at contact points. However, there is limited knowledge of the particle-scale behavior of the weak sandstone, and the parameters that affect sanding. This paper aims to investigate the reliability of using PFC3D and a simple Darcy flow in understanding the sand production behavior of a weak sandstone. An isotropic tri-axial test on a weak oil sandstone sample was first simulated at a confining stress of 1MPa to calibrate and validate the parallel bond models of PFC3D using a 10m height and 10m diameter solid cylindrical model. The effect of the confining stress on the number of bonds failure was studied using this cylindrical model. With the calibrated data and sample material properties obtained from the tri-axial test, simulations without and with fluid flow were carried out to check on the effect of Darcy flow on bonds failure using the same model geometry. The fluid flow network comprised of every four particles connected with tetrahedral flow pipes with a central pore or flow domain. Parametric studies included the effects of confining stress, and fluid pressure; as well as validating flow rate – permeability relationship to verify Darcy’s fluid flow law. The effect of model size scaling on sanding was also investigated using 4m height, 2m diameter model. The parallel bond model successfully calibrated the sample’s strength of 4.4MPa, showing a sharp peak strength before strain-softening, similar to the behavior of real cemented sandstones. There seems to be an exponential increasing relationship for the bigger model, but a curvilinear shape for the smaller model. The presence of the Darcy flow induced tensile forces and increased the number of broken bonds. For the parametric studies, flow rate has a linear relationship with permeability at constant pressure head. The higher the fluid flow pressure, the higher the number of broken bonds/sanding. The DEM PFC3D is a promising tool to studying the micromechanical behavior of cemented sandstones.Keywords: discrete element method, fluid flow, parametric study, sand production/bonds failure
Procedia PDF Downloads 32314644 Design of a Tool for Generating Test Cases from BPMN
Authors: Prat Yotyawilai, Taratip Suwannasart
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Business Process Model and Notation (BPMN) is more important in the business process and creating functional models, and is a standard for OMG, which becomes popular in various organizations and in education. Researches related to software testing based on models are prominent. Although most researches use the UML model in software testing, not many researches use the BPMN Model in creating test cases. Therefore, this research proposes a design of a tool for generating test cases from the BPMN. The model is analyzed and the details of the various components are extracted before creating a flow graph. Both details of components and the flow graph are used in generating test cases.Keywords: software testing, test case, BPMN, flow graph
Procedia PDF Downloads 55514643 An Improved Lower Bound for Minimal-Area Convex Cover for Closed Unit Curves
Authors: S. Som-Am, B. Grechuk
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Moser’s worm problem is the unsolved problem in geometry which asks for the minimal area of a convex region on the plane which can cover all curves of unit length, assuming that curves may be rotated and translated to fit inside the region. We study a version of this problem asking for a minimal convex cover for closed unit curves. By combining geometric methods with numerical box’s search algorithm, we show that any such cover should have an area at least 0.0975. This improves the best previous lower bound of 0.096694. In fact, we show that the minimal area of convex hull of circle, equilateral triangle, and rectangle of perimeter 1 is between 0.0975 and 0.09763.Keywords: Moser’s worm problem, closed arcs, convex cover, minimal-area cover
Procedia PDF Downloads 21114642 Nonlinear Mathematical Model of the Rotor Motion in a Thin Hydrodynamic Gap
Authors: Jaroslav Krutil, Simona Fialová, , František Pochylý
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A nonlinear mathematical model of mutual fluid-structure interaction is presented in the work. The model is applicable to the general shape of sealing gaps. An in compressible fluid and turbulent flow is assumed. The shaft carries a rotational and procession motion, the gap is axially flowed through. The achieved results of the additional mass, damping and stiffness matrices may be used in the solution of the rotor dynamics. The usage of this mathematical model is expected particularly in hydraulic machines. The method of control volumes in the ANSYS Fluent was used for the simulation. The obtained results of the pressure and velocity fields are used in the mathematical model of additional effects.Keywords: nonlinear mathematical model, CFD modeling, hydrodynamic sealing gap, matrices of mass, stiffness, damping
Procedia PDF Downloads 53614641 Effect of Longitudinal Fins on Air-Flow Characteristics for Wing-Shaped Tubes in Cross Flow
Authors: Sayed Ahmed El Sayed, Osama M. Mesalhy, Mohamed A. Abdelatief
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A numerical study has been conducted to clarify fluid flow characteristics, pressure distributions, and skin friction coefficient over a wing-shaped tubes bundle in staggered arrangement with the placement of longitudinal fins (LF) at downstream position of the tube. The air-side Rea were at 1.8 x 103 to 9.7 x 103. The tubes bundle were employed with various fin height [hf] and fin thickness (δ) from (2 mm ≤ hf ≤ 12 mm) and (1.5 mm ≤ δ ≤ 3.5 mm) respectively at the considered Rea range. The flow pattern around the staggered wing-shaped tubes bundle was predicted using the commercial CFD FLUENT 6.3.26 software package. The distribution of average skin friction coefficient around wing-shaped tubes bundle is studied. Correlation of pressure drop coefficient Pdc and skin friction coefficient (Cf) in terms of Rea, design parameters for the studied cases were presented. Results indicated that the values of Pdc for hf = 6 mm are lower than these of NOF and hf = 2 mm by about 11 % and 13 % respectively for considered Rea range. Cf decreases as Rea increases. LFTH with hf = 6 mm offers lower form drag than that with hf = 12 mm and that of NOF. The lowest values of the pumping power are achieved for arrangements of hf = 6 mm for the considered Rea range. δ has negligible effect on skin friction coefficient, while has a slightly variation in ∆Pa. The wing-shaped tubes bundle heat exchanger with hf = 6 mm has the lowest values of ∆Pa, Pdc, Cf, and pumping power and hence the best performance comparing with the other bundles. Comparisons between the experimental and numerical results of the present study and those obtained by similar previous studies showed good agreements.Keywords: longitudinal fins, skin friction, flow characteristics, FLUENT, wing-shaped tubes
Procedia PDF Downloads 54014640 Digitalized Public Sector Practices: Opportunities for Open Innovation in Rwanda
Authors: Reem Abou Refaie, Christoph Meinel
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The paper explores the impact of the COVID-19 crisis on the internal as well as external digitalized work practices of public service providers as part of a Public-Private Partnership Model. It focuses on the effect of uncertainty on generating Open Innovation practices. Our inquiry relies on semi-structured interviews (n=14) from a case study of Rwanda’s Public Service Delivery System in the context of research cooperation with IremboGov, the country’s One-Stop-Shop Platform for public services. It presents four propositions on harnessing opportunities for OI in the context of the public sector beyond the pandemic response. Practitioners can find characterizations of OI opportunities and gain insights on fostering OI in Public Sector Organizations.Keywords: open innovation, digital transformation, public sector, Rwanda
Procedia PDF Downloads 12814639 Optimal Sequential Scheduling of Imperfect Maintenance Last Policy for a System Subject to Shocks
Authors: Yen-Luan Chen
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Maintenance has a great impact on the capacity of production and on the quality of the products, and therefore, it deserves continuous improvement. Maintenance procedure done before a failure is called preventive maintenance (PM). Sequential PM, which specifies that a system should be maintained at a sequence of intervals with unequal lengths, is one of the commonly used PM policies. This article proposes a generalized sequential PM policy for a system subject to shocks with imperfect maintenance and random working time. The shocks arrive according to a non-homogeneous Poisson process (NHPP) with varied intensity function in each maintenance interval. As a shock occurs, the system suffers two types of failures with number-dependent probabilities: type-I (minor) failure, which is rectified by a minimal repair, and type-II (catastrophic) failure, which is removed by a corrective maintenance (CM). The imperfect maintenance is carried out to improve the system failure characteristic due to the altered shock process. The sequential preventive maintenance-last (PML) policy is defined as that the system is maintained before any CM occurs at a planned time Ti or at the completion of a working time in the i-th maintenance interval, whichever occurs last. At the N-th maintenance, the system is replaced rather than maintained. This article first takes up the sequential PML policy with random working time and imperfect maintenance in reliability engineering. The optimal preventive maintenance schedule that minimizes the mean cost rate of a replacement cycle is derived analytically and determined in terms of its existence and uniqueness. The proposed models provide a general framework for analyzing the maintenance policies in reliability theory.Keywords: optimization, preventive maintenance, random working time, minimal repair, replacement, reliability
Procedia PDF Downloads 27514638 The Relationships among Learning Emotion, Major Satisfaction, Learning Flow, and Academic Achievement in Medical School Students
Authors: S. J. Yune, S. Y. Lee, S. J. Im, B. S. Kam, S. Y. Baek
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This study explored whether academic emotion, major satisfaction, and learning flow are associated with academic achievement in medical school. We know that emotion and affective factors are important factors in students' learning and performance. Emotion has taken the stage in much of contemporary educational psychology literature, no longer relegated to secondary status behind traditionally studied cognitive constructs. Medical school students (n=164) completed academic emotion, major satisfaction, and learning flow online survey. Academic performance was operationalized as students' average grade on two semester exams. For data analysis, correlation analysis, multiple regression analysis, hierarchical multiple regression analyses and ANOVA were conducted. The results largely confirmed the hypothesized relations among academic emotion, major satisfaction, learning flow and academic achievement. Positive academic emotion had a correlation with academic achievement (β=.191). Positive emotion had 8.5% explanatory power for academic achievement. Especially, sense of accomplishment had a significant impact on learning performance (β=.265). On the other hand, negative emotion, major satisfaction, and learning flow did not affect academic performance. Also, there were differences in sense of great (F=5.446, p=.001) and interest (F=2.78, p=.043) among positive emotion, boredom (F=3.55, p=.016), anger (F=4.346, p=.006), and petulance (F=3.779, p=.012) among negative emotion by grade. This study suggested that medical students' positive emotion was an important contributor to their academic achievement. At the same time, it is important to consider that some negative emotions can act to increase one’s motivation. Of particular importance is the notion that instructors can and should create learning environment that foster positive emotion for students. In doing so, instructors improve their chances of positively impacting students’ achievement emotions, as well as their subsequent motivation, learning, and performance. This result had an implication for medical educators striving to understand the personal emotional factors that influence learning and performance in medical training.Keywords: academic achievement, learning emotion, learning flow, major satisfaction
Procedia PDF Downloads 27314637 Analysis of Two Methods to Estimation Stochastic Demand in the Vehicle Routing Problem
Authors: Fatemeh Torfi
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Estimation of stochastic demand in physical distribution in general and efficient transport routs management in particular is emerging as a crucial factor in urban planning domain. It is particularly important in some municipalities such as Tehran where a sound demand management calls for a realistic analysis of the routing system. The methodology involved critically investigating a fuzzy least-squares linear regression approach (FLLRs) to estimate the stochastic demands in the vehicle routing problem (VRP) bearing in mind the customer's preferences order. A FLLR method is proposed in solving the VRP with stochastic demands. Approximate-distance fuzzy least-squares (ADFL) estimator ADFL estimator is applied to original data taken from a case study. The SSR values of the ADFL estimator and real demand are obtained and then compared to SSR values of the nominal demand and real demand. Empirical results showed that the proposed methods can be viable in solving problems under circumstances of having vague and imprecise performance ratings. The results further proved that application of the ADFL was realistic and efficient estimator to face the stochastic demand challenges in vehicle routing system management and solve relevant problems.Keywords: fuzzy least-squares, stochastic, location, routing problems
Procedia PDF Downloads 43414636 Two-Phase Flow Study of Airborne Transmission Control in Dental Practices
Authors: Mojtaba Zabihi, Stephen Munro, Jonathan Little, Ri Li, Joshua Brinkerhoff, Sina Kheirkhah
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Occupational Safety and Health Administration (OSHA) identified dental workers at the highest risk of contracting COVID-19. This is because aerosol-generating procedures (AGP) during dental practices generate aerosols ( < 5µm) and droplets. These particles travel at varying speeds, in varying directions, and for varying durations. If these particles bear infectious viruses, their spreading causes airborne transmission of the virus in the dental room, exposing dentists, hygienists, dental assistants, and even other dental clinic clients to the infection risk. Computational fluid dynamics (CFD) simulation of two-phase flows based on a discrete phase model (DPM) is carried out to study the spreading of aerosol and droplets in a dental room. The simulation includes momentum, heat, and mass transfers between the particles and the airflow. Two simulations are conducted and compared. One simulation focuses on the effects of room ventilation in winter and summer on the particles' travel. The other simulation focuses on the control of aerosol and droplets' spreading. A suction collector is added near the source of aerosol and droplets, creating a flow sink in order to remove the particles. The effects of the suction flow on the aerosol and droplet travel are studied. The suction flow can remove aerosols and also reduce the spreading of droplets.Keywords: aerosols, computational fluid dynamics, COVID-19, dental, discrete phase model, droplets, two-phase flow
Procedia PDF Downloads 26514635 Julia-Based Computational Tool for Composite System Reliability Assessment
Authors: Josif Figueroa, Kush Bubbar, Greg Young-Morris
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The reliability evaluation of composite generation and bulk transmission systems is crucial for ensuring a reliable supply of electrical energy to significant system load points. However, evaluating adequacy indices using probabilistic methods like sequential Monte Carlo Simulation can be computationally expensive. Despite this, it is necessary when time-varying and interdependent resources, such as renewables and energy storage systems, are involved. Recent advances in solving power network optimization problems and parallel computing have improved runtime performance while maintaining solution accuracy. This work introduces CompositeSystems, an open-source Composite System Reliability Evaluation tool developed in Julia™, to address the current deficiencies of commercial and non-commercial tools. This work introduces its design, validation, and effectiveness, which includes analyzing two different formulations of the Optimal Power Flow problem. The simulations demonstrate excellent agreement with existing published studies while improving replicability and reproducibility. Overall, the proposed tool can provide valuable insights into the performance of transmission systems, making it an important addition to the existing toolbox for power system planning.Keywords: open-source software, composite system reliability, optimization methods, Monte Carlo methods, optimal power flow
Procedia PDF Downloads 7414634 Experimental Study of Flow Effects of Solid Particles’ Size in Porous Media
Authors: S. Akridiss, E. El Tabach, K. Chetehouna, N. Gascoin, M. S. Kadiri
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Transpiration cooling combined to regenerative cooling is a technique that could be used to cool the porous walls of the future ramjet combustion chambers; it consists of using fuel that will flow through the pores of the porous material consisting of the chamber walls, as coolant. However, at high temperature, the fuel is pyrolysed and generates solid coke particles inside the porous materials. This phenomenon can lead to a significant decrease of the material permeability and can affect the efficiency of the cooling system. In order to better understand this phenomenon, an experimental laboratory study was undertaken to determine the transport and deposition of particles in a sintered porous material subjected to steady state flow. The test bench composed of a high-pressure autoclave is used to study the transport of different particle size (35Keywords: experimental study, permeability, porous material, suspended particles
Procedia PDF Downloads 27614633 Performance Assessment of PV Based Grid Connected Solar Plant with Varying Load Conditions
Authors: Kusum Tharani, Ratna Dahiya
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This paper aims to analyze the power flow of a grid connected 100-kW Photovoltaic(PV) array connected to a 25-kV grid via a DC-DC boost converter and a three-phase three-level Voltage Source Converter (VSC). Maximum Power Point Tracking (MPPT) is implemented in the boost converter bymeans of a Simulink model using the 'Perturb & Observe' technique. First, related papers and technological reports were extensively studied and analyzed. Accordingly, the system is tested under various loading conditions. Power flow analysis is done using the Newton-Raphson method in Matlab environment. Finally, the system is subject to Single Line to Ground Fault and Three Phase short circuit. The results are simulated under the grid-connected operating model.Keywords: grid connected PV Array, Newton-Raphson Method, power flow analysis, three phase fault
Procedia PDF Downloads 55314632 Impacts of Land Use and Land Cover Change on Stream Flow and Sediment Yield of Genale Dawa Dam III Watershed, Ethiopia
Authors: Aklilu Getahun Sulito
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Land Use and Land Cover change dynamics is a result of complex interactions betweenseveral bio- physical and socio-economic conditions. The impacts of the landcoverchange on stream flow and sediment yield were analyzed statistically usingthehydrological model, SWAT. Genale Dawa Dam III watershed is highly af ectedbydeforestation, over grazing, and agricultural land expansion. This study was aimedusingSWAT model for the assessment of impacts of land use land cover change on sediment yield, evaluating stream flow on wet &dry seasons and spatial distribution sediment yieldfrom sub-basins of the Genale Dawa Dam III watershed. Land use land cover maps(LULC) of 2000, 2008 and 2016 were used with same corresponding climate data. During the study period most parts of the forest, dense forest evergreen and grass landchanged to cultivated land. The cultivated land increased by 26.2%but forest land, forest evergreen lands and grass lands decreased by 21.33%, 11.59 % and 7.28 %respectively, following that the mean annual sediment yield of watershed increased by 7.37ton/haover16 years period (2000 – 2016). The analysis of stream flow for wet and dry seasonsshowed that the steam flow increased by 25.5% during wet season, but decreasedby29.6% in the dry season. The result an average annual spatial distribution of sediment yield increased by 7.73ton/ha yr -1 from (2000_2016). The calibration results for bothstream flow and sediment yield showed good agreement between observed and simulateddata with the coef icient of determination of 0.87 and 0.84, Nash-Sutclif e ef iciencyequality to 0.83 and 0.78 and percentage bias of -7.39% and -10.90%respectively. Andthe result for validation for both stream flow and sediment showed good result withCoef icient of determination equality to 0.83 and 0.80, Nash-Sutclif e ef iciency of 0.78and 0.75 and percentage bias of 7.09% and 3.95%. The result obtained fromthe model based on the above method was the mean annual sediment load at Genale DawaDamIIIwatershed increase from 2000 to 2016 for the reason that of the land uses change. Sotouse the Genale Dawa Dam III the land use management practices are neededinthefuture to prevent further increase of sediment yield of the watershed.Keywords: Genale Dawa Dam III watershed, land use land cover change, SWAT, spatial distribution, sediment yield, stream flow
Procedia PDF Downloads 5514631 Two-Dimensional CFD Simulation of the Behaviors of Ferromagnetic Nanoparticles in Channel
Authors: Farhad Aalizadeh, Ali Moosavi
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This paper presents a two-dimensional Computational Fluid Dynamics (CFDs) simulation for the steady, particle tracking. The purpose of this paper is applied magnetic field effect on Magnetic Nanoparticles velocities distribution. It is shown that the permeability of the particles determines the effect of the magnetic field on the deposition of the particles and the deposition of the particles is inversely proportional to the Reynolds number. Using MHD and its property it is possible to control the flow velocity, remove the fouling on the walls and return the system to its original form. we consider a channel 2D geometry and solve for the resulting spatial distribution of particles. According to obtained results when only magnetic fields are applied perpendicular to the flow, local particles velocity is decreased due to the direct effect of the magnetic field return the system to its original fom. In the method first, in order to avoid mixing with blood, the ferromagnetic particles are covered with a gel-like chemical composition and are injected into the blood vessels. Then, a magnetic field source with a specified distance from the vessel is used and the particles are guided to the affected area. This paper presents a two-dimensional Computational Fluid Dynamics (CFDs) simulation for the steady, laminar flow of an incompressible magnetorheological (MR) fluid between two fixed parallel plates in the presence of a uniform magnetic field. The purpose of this study is to develop a numerical tool that is able to simulate MR fluids flow in valve mode and determineB0, applied magnetic field effect on flow velocities and pressure distributions.Keywords: MHD, channel clots, magnetic nanoparticles, simulations
Procedia PDF Downloads 36814630 Study on the Effects of Geometrical Parameters of Helical Fins on Heat Transfer Enhancement of Finned Tube Heat Exchangers
Authors: H. Asadi, H. Naderan Tahan
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The aim of this paper is to investigate the effect of geometrical properties of helical fins in double pipe heat exchangers. On the other hand, the purpose of this project is to derive the hydraulic and thermal design tables and equations of double heat exchangers with helical fins. The numerical modeling is implemented to calculate the considered parameters. Design tables and correlated equations are generated by repeating the parametric numerical procedure for different fin geometries. Friction factor coefficient and Nusselt number are calculated for different amounts of Reynolds, fluid Prantle and fin twist angles for the range of laminar fluid flow in annular tube with helical fins. Results showed that friction factor coefficient and Nusselt number will be increased for higher Reynolds numbers and fins’ twist angles in general. These two parameters follow different patterns in response to Reynolds number increment. Thermal performance factor is defined to analyze these different patterns. Temperature and velocity contours are plotted against twist angle and number of fins to describe the changes in flow patterns in different geometries of twisted finned annulus. Finally twisted finned annulus friction factor coefficient, Nusselt Number and thermal performance factor are correlated by simulating the model in different design points.Keywords: double pipe heat exchangers, heat exchanger performance, twisted fins, computational fluid dynamics
Procedia PDF Downloads 28914629 Building Information Modeling Implementation for Managing an Extra Large Governmental Building Renovation Project
Authors: Pornpote Nusen, Manop Kaewmoracharoen
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In recent years, there was an observable shift in fully developed countries from constructing new buildings to modifying existing buildings. The issue was that although an effective instrument like BIM (Building Information Modeling) was well developed for constructing new buildings, it was not widely used to renovate old buildings. BIM was accepted as an effective means to overcome common managerial problems such as project delay, cost overrun, and poor quality of the project life cycle. It was recently introduced in Thailand and rarely used in a renovation project. Today, in Thailand, BIM is mostly used for creating aesthetic 3D models and quantity takeoff purposes, though it can be an effective tool to use as a project management tool in planning and scheduling. Now the governmental sector in Thailand begins to recognize the uses of using BIM to manage a construction project, but the knowledge about the BIM implementation to governmental construction projects is underdeveloped. Further studies need to be conducted to maximize its advantages for the governmental sector. An educational extra large governmental building of 17,000 square-meters was used in this research. It is currently under construction for a two-year renovation project. BIM models of the building for the exterior and interior areas were created for the whole five floors. Then 4D BIM with combination of 3D BIM plus time was created for planning and scheduling. Three focus groups had been done with executive committee, contractors, and officers of the building to discuss the possibility of usage and usefulness of BIM approach over the traditional process. Several aspects were discussed in the positive sides, especially several foreseen problems, such as the inadequate accessibility of ways, the altered ceiling levels, the impractical construction plan created through a traditional approach, and the lack of constructability information. However, for some parties, the cost of BIM implementation was a concern, though, this study believes, its uses outweigh the cost.Keywords: building information modeling, extra large building, governmental building renovation, project management, renovation, 4D BIM
Procedia PDF Downloads 15314628 Haemodynamics Study in Subject Specific Carotid Bifurcation Using FSI
Authors: S. M. Abdul Khader, Anurag Ayachit, Raghuvir Pai, K. A. Ahmed, V. R. K Rao, S. Ganesh Kamath
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The numerical simulation has made tremendous advances in investigating the blood flow phenomenon through elastic arteries. Such study can be useful in demonstrating the disease progression and haemodynamics of cardiovascular diseases such as atherosclerosis. In the present study, patient specific case diagnosed with partially stenosed complete right ICA and normal left carotid bifurcation without any atherosclerotic plaque formation is considered. 3D patient specific carotid bifurcation model is generated based on CT scan data using MIMICS-4.0 and numerical analysis is performed using FSI solver in ANSYS-14.5. The blood flow is assumed to be incompressible, homogenous and Newtonian, while the artery wall is assumed to be linearly elastic. The two-way sequentially-coupled transient FSI analysis is performed using FSI solver for three pulse cycles. The haemodynamic parameters such as flow pattern, Wall Shear Stress, pressure contours and arterial wall deformation are studied at the bifurcation and critical zones such as stenosis. The variation in flow behavior is studied throughout the pulse cycle. Also, the simulation results reveals that there is a considerable increase in the flow behavior in stenosed carotid in contrast to the normal carotid bifurcation system. The investigation also demonstrates the disturbed flow pattern especially at the bifurcation and stenosed zone elevating the haemodynamics, particularly during peak systole and later part of the pulse cycle. The results obtained agree well with the clinical observation and demonstrates the potential of patient specific numerical studies in prognosis of disease progression and plaque rupture.Keywords: fluid-structure interaction, arterial stenosis, wall shear stress, carotid artery bifurcation
Procedia PDF Downloads 57114627 The Classical and Hellenistic Architectural Elements of the Temple of Echmun in Sidon
Authors: Amal Alatar
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The paper focuses on the exploration of architectural characteristics and decorative elements of the temple of Echmun, emphasizing the socio-economic significance of Sidon during the Greek and Roman periods to understand the implications of their spread and development on the Phoenician cities, as well as reveal the symbolical and societal connotations that may have been connected with the buildings, in order to allow a well-founded examination of common characteristics. In general, studying Phoenician archaeology posed some problems. The main problem is that most major Phoenician settlements lay beneath modern urban centers. This situation often prevented or largely restricted full archaeological investigations; the publications are frequently not complete enough to determine the basic characteristics of the architectural elements. Another key problem is the political instability of the region, which affected the archaeological research in the Phoenician homeland for many years. Nevertheless, during the past decades, an ever-growing cache of data was acquired from the archaeological surroundings of the Phoenician sites. Both the architectural elements from the Greek and Roman period have never been studied as a group before. Surprisingly, they have been largely ignored, despite their apparent profusion throughout the cities. The Roman period of Sidon has generally been neglected in preference to earlier periods, where it is often difficult to distinguish between Roman, Bronze age, medieval and Ottoman structures.Keywords: archaeology, classical, Hellenistic, Eshmun Temple, architecture, Sidon, Lebanon
Procedia PDF Downloads 10114626 Enhanced Poly Fluoroalkyl Substances Degradation in Complex Wastewater Using Modified Continuous Flow Nonthermal Plasma Reactor
Authors: Narasamma Nippatlapallia
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Communities across the world are desperate to get their environment free of toxic per-poly fluoroalkyl substances (PFAS) especially when these chemicals are in aqueous media. In the present study, two different chain length PFAS (PFHxA (C6), PFDA (C10)) are selected for degradation using a modified continuous flow nonthermal plasma. The results showed 82.3% PFHxA and 94.1 PFDA degradation efficiencies, respectively. The defluorination efficiency is also evaluated which is 28% and 34% for PFHxA and PFDA, respectively. The results clearly indicates that the structure of PFAS has a great impact on degradation efficiency. The effect of flow rate is studied. increase in flow rate beyond 2 mL/min, decrease in degradation efficiency of the targeted PFAS was noticed. PFDA degradation was decreased from 85% to 42%, and PFHxA was decreased to 32% from 64% with increase in flow rate from 2 to 5 mL/min. Similarly, with increase in flow rate the percentage defluorination was decreased for both C10, and C6 compounds. This observation can be attributed to mainly because of change in residence time (contact time). Real water/wastewater is a composition of various organic, and inorganic ions that may affect the activity of oxidative species such as 𝑂𝐻. radicals on the target pollutants. Therefore, it is important to consider radicals quenching chemicals to understand the efficiency of the reactor. In gas-liquid NTP discharge reactors 𝑂𝐻. , 𝑒𝑎𝑞 − , 𝑂 . , 𝑂3, 𝐻2𝑂2, 𝐻. are often considered as reactive species for oxidation and reduction of pollutants. In this work, the role played by two distinct 𝑂 .𝐻 Scavengers, ethanol and glycerol, on PFAS percentage degradation, and defluorination efficiency (i,e., fluorine removal) are measured was studied. The addition of scavenging agents to the PFAS solution diminished the PFAS degradation to different extents depending on the target compound molecular structure. In comparison with the degradation of only PFAS solution, the addition of 1.25 M ethanol inhibited C10, and C6 degradation by 8%, and 12%, respectively. This research was supported with energy efficiency, production rate, and specific yield, fluoride, and PFAS concentration analysis with respect to optimum hydraulic retention time (HRT) of the continuous flow reactor.Keywords: wastewater, PFAS, nonthermal plasma, mineralization, defluorination
Procedia PDF Downloads 2914625 Procedure to Optimize the Performance of Chemical Laser Using the Genetic Algorithm Optimizations
Authors: Mohammedi Ferhate
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This work presents details of the study of the entire flow inside the facility where the exothermic chemical reaction process in the chemical laser cavity is analyzed. In our paper we will describe the principles of chemical lasers where flow reversal is produced by chemical reactions. We explain the device for converting chemical potential energy laser energy. We see that the phenomenon thus has an explosive trend. Finally, the feasibility and effectiveness of the proposed method is demonstrated by computer simulationKeywords: genetic, lasers, nozzle, programming
Procedia PDF Downloads 9414624 Numerical Simulation of the Flow Channel in the Curved Plane Oil Skimmer
Authors: Xing Feng, Yuanbin Li
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Oil spills at sea can cause severe marine environmental damage, including bringing huge hazards to living resources and human beings. In situ burning or chemical dispersant methods can be used to handle the oil spills sometimes, but these approaches will bring secondary pollution and fail in some situations. Oil recovery techniques have also been developed to recover oil using oil skimmer equipment installed on ships, while the hydrodynamic process of the oil flowing through the oil skimmer is very complicated and important for evaluating the recovery efficiency. Based on this, a two-dimensional numerical simulation platform for simulating the hydrodynamic process of the oil flowing through the oil skimmer is established based on the Navier-Stokes equations for viscous, incompressible fluid. Finally, the influence of the design of the flow channel in the curved plane oil skimmer on the hydrodynamic process of the oil flowing through the oil skimmer is investigated based on the established simulation platform.Keywords: curved plane oil skimmer, flow channel, CFD, VOF
Procedia PDF Downloads 29514623 Energy Efficiency Improvement of Excavator with Independent Metering Valve by Continuous Mode Changing Considering Engine Fuel Consumption
Authors: Sang-Wook Lee, So-Yeon Jeon, Min-Gi Cho, Dae-Young Shin, Sung-Ho Hwang
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Hydraulic system of excavator gets working energy from hydraulic pump which is connected to output shaft of engine. Recently, main control valve (MCV) which is composed of several independent metering valve (IMV) has been introduced for better energy efficiency of the hydraulic system so that fuel efficiency of the excavator can be improved. Excavator with IMV has 5 operating modes depending on the quantity of regeneration flow. In this system, the hydraulic pump is controlled to supply demanded flow which is needed to operate each mode. Because the regenerated flow supply energy to actuators, the hydraulic pump consumes less energy to make same motion than one that does not regenerate flow. The horse power control is applied to the hydraulic pump of excavator for maintaining engine start under a heavy load and this control makes the flow of hydraulic pump reduced. When excavator is in complex operation such as loading or unloading soil, the hydraulic pump discharges small quantity of working fluid in high pressure. At this operation, the engine of excavator does not run at optimal operating line (OOL). The engine needs to be operated on OOL to improve fuel efficiency and by controlling hydraulic pump the engine can drive on OOL. By continuous mode changing of IMV, the hydraulic pump is controlled to make engine runs on OOL. The simulation result of this study shows that fuel efficiency of excavator with IMV can be improved by considering engine OOL and continuous mode changing algorithm.Keywords: continuous mode changing, engine fuel consumption, excavator, fuel efficiency, IMV
Procedia PDF Downloads 38514622 Natural Convection between Two Parallel Wavy Plates
Authors: Si Abdallah Mayouf
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In this work, the effects of the wavy surface on free convection heat transfer boundary layer flow between two parallel wavy plates have been studied numerically. The two plates are considered at a constant temperature. The equations and the boundary conditions are discretized by the finite difference scheme and solved numerically using the Gauss-Seidel algorithm. The important parameters in this problem are the amplitude of the wavy surfaces and the distance between the two wavy plates. Results are presented as velocity profiles, temperature profiles and local Nusselt number according to the important parameters.Keywords: free convection, wavy surface, parallel plates, fluid dynamics
Procedia PDF Downloads 307