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Item Open Access 3D CFD Modeling Investigation of Potential Vortex Formation at the Intakes of Caruachi Powerhouse(INTERNATIONAL CONFERENCE ONHYDRAULICS OF DAMS AND RIVER STRUCTURES, TEHRAN, IRAN; 04/2004, 2004-04) Marcano, A.; Rojas-Solorzano, L.; Reyes, M.In this paper, the 3-D CFD simulation of the free-surface flow approaching the intakes of Caruachi Powerhouse is presented. The aim of the investigation is to determine whether or not vortex structures are likely to appear from the water surface through the intakes, as the result of the presence of cofferdams placed few meters upstream of the intakes. The presence of cofferdams was a note of concern with regard to the effects they might have on the turbine intakes once the hydroelectric central starts operating. In all the considered conditions, results did not show neither strong surface vortices in the proximities of the Power House intakes, nor air entrainment-entrapment towards the intakes, which reflects the safe operation of the turbines in the presence of the cofferdams. The latter added in decision taking on leaving the cofferdams submerged instead of removing them, which resulted in cost savings for the projectItem Open Access A geospatial model to determine patterns in river ice cover breakup and jamming behaviour(2014-08) Sagin, JayIn the past, both empirical and process-based attempts have been made to predict river ice behaviour, in particular ice cover breakup and ice jamming occurrences. These methods perform with varying and limited success and tend to be site specific. A method is required which can simply estimate the predisposition of river reaches to ice breakup and jamming events. This paper introduces a geospatial modelling approach which can fulfil that task and improve the predictive power of ice cover breakup and ice jamming behaviour. The geospatial model can determine the most vulnerable sections along the studied reaches to such behaviour, which are phenomena entailing hydraulic, ice morphology and fluvial geomorphology. A geospatial model clusters hydraulic characteristics (e.g. discharge or stage), ice characteristics (e.g. ice thickness and ice type) and river geomorphological characteristics (e.g. sinuosity, slope, width, etc.) into common river features called Geomorphic Response Units (GRU). A statistical clustering technique such as principle component analysis (PCA) is used to derive these GRUs. It is assumed that certain GRUs will be more susceptible to certain ice cover behaviour, such as breakup and jamming of river ice. Data acquired along the Slave River and its delta in Canada is used to test the geospatial model. The main data sources are space-borne remote sensing MODIS imagery and traditional and local knowledge from members of the communities alongside the river, in particular Fort Resolution and Fort SmithItem Open Access Analysis of Current Situation in Municipal Waste Management and Implementation of Decision Support Software in Astana, Kazakhstan(2014) Inglezakis, V.; Rojas-Solorzano, L.; Kim, J.; Moustakas, K.; Aitbekova, A.; Ismailova, A.; Shorakyzy, G.; Kystauova, A.; Abirov, A.A.; Serikbayev, N.S.The city of Astana, capital of Kazakhstan with population of 804,474 generates approximately 1.39 kg/inh./day of municipal solid waste while collection rate is higher than 72% (MSW). An MBT plant of planned capacity of 600-800 tn/day and a new landfill cell of about 2 million tones are in place. Preliminary studies showed that the MSW composition is as follows: food and garden waste 29.5%, plastics 18.5%, paper 13%, glass 14.5%, textiles 9.5%, metals 0.9% and others 14.1%. About 23-34 tons of recyclables (paper, metal, glass, PET bottles, HDPE film, HDPE plastic, etc.) is separated in the existing MBT daily. In 2014 it is planned to implement separate waste collection in places of waste accumulation and a waste separation at source system. The purpose of the study is to assess the current situation of municipal solid waste in Astana and implement a Decision Support Software tool developed by the research team in order to analyse data, compare alternative waste management scenarios and propose a holistic approach in solid waste management planning. The latest available data on waste generation, composition and existing infrastructure were used in order to identify the baseline situation. This is the first research of this type conducted in KazakhstanItem Open Access Antenna Beamforming for Energy Harvesting in Cognitive Radio Networks(2016) Liu, Huidong; Chen, Jin; Ding, Guoru; Tsiftsis, Theodoros A.; Rowell, CorbettIn this paper, a cooperative cognitive radio network (CRN) with energy harvesting capabilities of its secondary users is considered. Specifically, cooperative spectrum sensing and multi-antenna beamforming are employed to improve the sensing performance and the energy transfer efficiency, respectively. In our approach, a homogeneous CRN scenario is studied where the optimal sensing probability of each second user (SU) is obtained to maximize the control center (CC) throughput while satisfying the energy causality and primary user (PU) collision constraints. An iterative algorithm is proposed to obtain the optimal charging time. Numerical results depict that in an energy constrained scenario, cooperative spectrum sensing with beamforming performs much better than cooperative spectrum sensing without beamforming in terms of increased system throughputItem Open Access BIM-GIS technologies in analysing the cost of assets after natural disasters: water flood and earthquake(International Scientific and Practical Conference "Geosystemic approach to the study of the natural environment of the Republic of Kazakhstan", 2018-04-13) Abuov, Y.; Omirtay, O.BIM-GIS integration. Analysing the cost of damage of buildings after natural disaster happened is a quite complex process. Methods having now to solve this problem take too many approximations; these models neglect unique parameters of each building. Final cost of damage depends on big number of variables. For example, in case of water flood, those variables can be: 3D geometric parameters of building, unit cost of materials, water velocity, depth of flood, physical properties of material, terrain geometry, etc. There is no single software to run mentioned complex model. This paper suggests integration of Geographic information system (GIS) and Building Information Modeling (BIM) as a method to perform cost analysis after natural disasters happened in given urban place. Both BIM and GIS are software which represent real world in digital format. But BIM uses micro level of objects and handles mainly indoor data while GIS uses macro level which includes rivers, basins and data in outdoor.Item Open Access Biogas home-production assessment using a selective sample of organic vegetable waste. A preliminary study(Red de Revistas Científicas de América Latina, el Caribe, España y Portugal Sistema de Información Científica, 2012-02) Durán-García, Martín; Ramírez, Yrina; Bravo, Ricardo; Rojas-Solorzano, L.Biogas generation plants using organic waste are a daily reality that can be observed in different areas of waste disposal that exist in many cities of the world. In fact, the generation of biogas through anaerobic bio-digestion of urban wastes has a high impact in terms of energy use and reduced environmental liabilities. The present study focuses on the assessment of biogas production for domestic consumption; several biodigesters were tested in order to evaluate the biogas production under standard pressure and temperature. The test estimates volume of biogas being produced, substrate pH and substrate concentration, using different types of catalysts. A test bed was designed for testing three digesters (A, B and C) within recycled bottles of polyethylene terephthalate (PET), whose maximum volume is ~0.6 liters. A 60g organic substrate compound was placed in each bottle. The organic compound consisted of peeling residues of potatoes, cabbage and carrots. Experimental characterization of the mixture allowed to observe the production of biogas for domestic use, system temperature, pH levels achieved, mass and substrate concentration, as well as concentration and volume of the catalyst. Further studies, with a larger sample and monitoring the container pressure are recommended in order to establish a more precise relation among the whole set of experimental parameters.Item Open Access CFD modeling of a road tunnel with multiple sources of Co. case of study: boqueron-I tunnel(Second International Tunnel Safety Forum, Lyon, April 2009, 2009-04) Urbina, Rafael J.; Rojas-Solorzano, L.; Blanco, Armando J.This work aims to the modeling of CO transport in one section considered critical of the Boqueron I tunnel, located on the outskirts of Caracas, the capital city of Venezuela, with a scenario where vehicles are stopped by an interruption of traffic. This scenario considers a relationship between the number of large-sized vehicles (buses or trucks) and small-sized vehicles (passenger cars) reported by transit statistics and also, it considers the semi-transverse ventilation system in the tunnel. It is explored the influence of the ventilation on the flow patterns and its relationship to the regions with the highest CO concentration. The finite-volume based finite element method is used for the discretization of the computational domain and the integration of the governing equations. The transient 3D-incompressible Navier-Stokes, energy, mass and species conservation equations, along with the k-e turbulence equations, were discretized, using higher-order numerical schemes in space. The numerical simulation is performed using a fully implicit coupled treatment of the set of resulting discrete transport equationsItem Open Access CFD modeling of porous media in the study of the flow at penstock intake of A 1:30 model of guri hydro-powerhouse(CIMENICS MF-185-2006, 2006) Arevalo, Angela; Montilla, Gonzalo; Rojas-Solorzano, L.; Reyes, Miguel; Marín, JuanThe transient free surface flow within a 1:30 model of the intake (penstock) to Power House II of Guri Hydro-Power Plant (Venezuela) is studied. The geometry of the model includes a reservoir of 4.31 meters upstream the dam. Geometric details and appropriate boundary conditions were reproduced mathematical and numerically using CFD (Computational Fluid Dynamics) techniques, running the commercial code CFXTM 4.4. The flow features nearby and within the penstock were captured. Special attention was paid to the evaluation of air entrainment that might eventually form due to the presence of free surface vortices. The computational domain included the anti-debris screen at the entrance of the penstock, considering it as a porous medium with equivalent permeability and porosity. Most of simulated cases corresponded to conditions in the prototype Guri´s free surface level of 240 a.s.l. (above sea level), with flow rate of 450 m3/seg. Air and water were considered incompressible fluids with and homogeneous interfacial transport model. Computed velocity profiles at different sections of the reservoir and pressure head along the penstock are compared with experiments. The numerical model captures the influence of the porous medium, used to simulate the anti-debris grill, onto the free-surface and pressure head within the penstock. In order to improve the predictive capabilities of the numerical model and to diminish the instabilities caused by the hydrostatic pressure condition at the entrance of the computational reservoir, preliminary results including a porous wall at the upstream boundary are presented. The porous wall, in fact, mimics the water-calming rock wall placed at the entrance of the experimental reservoir and proved to be a relevant element in improving the CFD predictionsItem Open Access CFD modeling of slurry flows in horizontal pipes(Proceedings of FEDSM2008 8th Symposium on Applications in Computational Fluid Dynamics August 17-20, Jacksonville, FL, 2008-08-17) Hernández, Franz H.; Blanco, Armando J.; Rojas-Solorzano, L.Liquid-solid two-phase flows are found in numerous operations in the chemical, petroleum, pharmaceutical and many other industries. In numerous cases, the mixture or slurry that flows is composed by a suspension of solid particles (dispersed phase) transported by a liquid (continuum phase). However, the large number and range of variables encountered in slurry flows, in the case of pipelines, cause the flow behavior of these slurry systems to vary over a wide range of conditions, and consequently, different approaches have been used to describe the behavior of different flow regimes. Therefore, there are numerous studies of particular cases that cover limited ranges of conditions. In consequence, the experimental approach is necessarily limited by geometric and physical scale factors. For these reasons, Computational Fluid Dynamics, CFD, constitutes an ideal technique for predicting the general flow behavior of these systems. CFD models in this area can be divided in two different classes: Eulerian-Eulerian and Lagrangian-Eulerian models. Differences between these models are related to the way the solid phase flow is represented. Lagrangian-Eulerian models calculate the path and motion of each particle, while Eulerian-Eulerian models treat the particle phase as a continuum and average out motion on the scale of individual particles. This work focuses on the Eulerian-Eulerian approach for modeling the flow of a mixture of sand particles and water in a horizontal pipe. Homogeneous and heterogeneous flow regimes are considered. The k-ε model was used for modeling turbulent effects. Additionally, closure of solid-phase momentum equations requires a description for the solid-phase stress. Constitutive relations for the solid-phase stress considering the inelastic nature of particle collisions based on the Gas Kinetic Theory concepts have been used. Governing equations are solved numerically using the control volume-based finite element method. An unstructured non-uniform grid was chosen to discretize the entire computational domain. A second-order scheme in space and time was used. Numerical solutions in fully developed turbulent flow were found. Results show that flow predictions are very sensitive to the restitution coefficient and pseudo-viscosity of the solid phase. The mean pressure gradients from numerical solutions were compared with results obtained using the correlations of Einstein, Thomas and Krieger for homogeneous cases and with experimental data found in the open literature for heterogeneous cases. The solutions were found to be in good agreement with both correlations and experimental data. In addition, these numerical results were closer to experimental data than results obtained using other numerical models.Item Open Access CFD Simulation of Air-water in a Spouted Bed(2011) Riera-Ortiz, Jaime; Zeppieri, Suzana; Rojas-Solorzano, L.; Derjani, SylvanaComputational fluid dynamics (CFD) is employed to simulate the air-water system in a spouted column with a draft tube. Numerical results of Reynolds-averaged Navier-Stokes (RANS) equations using the k-s and k-w two-equation turbulence models are compared with Pironti at al. (1995) experimental data. CFD predictions of the k-s and k-w turbulence models are in good agreement with the reported experimental data. The interfacial momentum transfer in modeling air-water system in the spouted bed indicated the importance of using turbulent dispersion force besides the most often used drag and lift forces to better predict flow behavior and air hold-up. Ishii-Zuber liquid-gas drag model with the lift and turbulent dispersion forces yields very good results; it correctly determines a hold up within 1% when used along with the k-s turbulence model, while it under-predicts the hold-up by 4.08% when used with the k-co model.Item Open Access CFD software applications for transcritical free surface flow(Proceedings of FEDSM2009 ASME 2009 Fluids Engineering Division Summer Meeting August 2-5, 2009, Vail, Colorado USA, 2009-08-02) Pineda, Saira F.; Blanco, Armando J.; Rojas-Solorzano, L.Flows in rivers, floodplains and coastal zones are very complex due to uneven bottom topography and irregular boundaries of the flow domain. In particular, when the flow shows strong gradients in water depth and velocity it is very difficult to predict, with accuracy, flow characteristics such as water profiles in all points of the domain. Traditional approaches solve shallow-water flow equations, known as Saint-Venant equations, when one or two dimension solutions can be adequate for obtaining most of the important flow characteristics. However, complex situations can require solving Navier-Stokes equations. In these cases, a two-phase flow problem must be solved and, as water profiles are not known in advance, only a numerical approach can be used to obtain approximate solutions. In addition, flow can be subcritical, supercritical or in a mixed-flow regime. These flow characteristics and complex geometries can make the use of in-house developed software difficult. The arrival of high performance computers and commercial software packages offers new possibilities in the field of numerical hydraulics. However, commercial software packages should be tested on some specific cases; so that these can be used with confidence. In this paper we solve, several cases of free surface flow that consider subcritical, supercritical, critical, oscillatory depth profiles and hydraulic jumps using a commercial package, CFX™. Most of these cases were proposed as benchmark solutions by MacDonald et al. (1997) for non-prismatic cross section, non-uniform bed slope and transition between subcritical and supercritical flow. Hydraulic jump cases consist of experimental data of hydraulics jumps obtained by Gharangik & Chaudhry (1991) for incident flow with Froude numbers of 2.3 and 4.23. In all simulated cases flow was described using a homogeneous model for each phase of the flow. Turbulence was modeled by using the well-known k-ε model. In addition, sensitivity to turbulence level in the entrance of flow domain was done to assure independence of results with this variable. Experimental facilities were properly represented in order to assure exact correspondence between boundary conditions of the model and the actual facility. Results obtained with CFX™ show excellent agreement with analytical solutions, for subcritical, supercritical, transitional and hydraulic jump cases. Special care with grid selection and entrance boundary condition is crucial to simulate with accuracy these types of flows. In particular, when a proper structured mesh is used, quality results are highly improved. Finally, results show to be insensitive to entrance turbulence conditionsItem Open Access Clean EnergyTechnologies:How to assess their viability?(Nazarbayev University School of Engineering and Digital Sciences, 2017-07-13) Rojas-Solórzano, Luis R.Item Open Access Comparative study of rans turbulence models for impinging jet simulations(Memorias del Congreso ASME USB 2011: IX CONGRESO ANUAL DE INGENIERÍA ASME USB 2011 03, 04 Y 05 de junio, 2011, Caracas - Venezuela, 2011) F., Vittori; Rojas-Solorzano, L.; Pavageau, M.Impinging plane jets are flow configurations with applications in many fields. The ability of several turbulence models to simulate this kind of flow was assessed. The numerical results were compared with the data of Cooper et al. (1993) for Re=7.0 104 and a jet nozzle aspect ratio H/D=6, and Re=2.3 104 and H/D=2. The SST, RSM-ε and RSM-BSL turbulence models were chosen because of their capability to predict flows with high streamline curvature and their expected good accuracy on near wall flow. The results show that the SST and RSM- ε perform better than the RSM-BSL in the prediction of the mean velocity profiles in the wall-jet and impact zone. The profiles of turbulent energy were particularly difficult to reproduce. All the turbulence models considered here exhibit a similar behavior with respect to the profiles of turbulent energy. The paper shows again the complexity of turbulent impinging jets and the relevant open challenges in CFDItem Open Access Comparison of the hydrological and meteorological project implementations in the different countries(Nazarbayev University School of Engineering and Digital Sciences, 2018-04-13) Sagintayev, ZhanayClimatic and anthropogenic distortions have impacted the enviroment and increased the probabilities of disaster events worldwide, including Kazakhstan. Water resources in Central Asia are generated at high mountains with snow and glacier melt dominating the flow regime. Increasing temperatures at higher elevations will have an impact on the snow and glacier melting process and this will change the flow regime of Kazakhstan, Central Asian Rivers. A combination of different modeling techniques, including regional climate monitoring, hydrological, hydro-geological, river hydraulics, geothechnical, debris flows, landslides, Artificial Neural Networks (ANN) modeling tools are helpful for prediction analysis and disaster event preparation activities. Some of these modeling techniques are reviewed in this article.Item Open Access Computational Analysis of Transport Across Flake-Filled Composites of Realistic Microstructure(Nazarbayev University School of Engineering and Digital Sciences, 2019-02-06) Tsiantis, Andreas; Sumbekova, Sholpan; Papathanasiou, Thanasis D.In this paper we present the results of a computational study of diffusion across disordered flake composites in which the flakes are misaligned with respect to the direction of bulk diffusion. We evaluate the effect of flake orientation as well as the influence of boundary conditions and unit-cell types on the predicted barrier properties. Flake orientation impacts very significantly on the barrier properties in flake-filled composites, and usually the key objective in their fabrication is to orient them as close as possible to being perpendicular to the direction of macroscopic diffusion. Our computations are carried out in two-dimensional, doubly-periodic unit cells, each containing up to 3000 individual flake cross-sections. We consider high aspect ratio (alpha) systems with alpha=1000, from the dilute (alpha phi=0.01) and into the very concentrated (alpha phi=40) regime. The effective diffusivity of the corresponding unit cells is computed from the imposed concentration difference and the computed mass flux, using Fick's Law. We show that use of cyclic boundary conditions and doubly-periodic unit cells results in effective diffusivities which are in agreement with theory and invariant of the shape of the unit cell. We also show that the use of adiabatic boundary conditions produces erroneous results at high flake concentrations. Finally we compare our results to the predictions of existing literature models and find that the latter deviate significantly from computation at high flake concentrations.Item Open Access Conceptual and basic design of a stirling engine prototype for electrical power generation using solar energy(2010) Roldan, Constantino; Pieretti, Pedro; Rojas-Solorzano, L.The research consisted in a conceptual and basic design of a prototype Stirling engine with the purpose of taking advantage of the solar radiation to produce electric energy. The work began with a bibliography review covering aspects as history, basic functioning, design configurations, applications and analysis methods, just to continue with the conceptual design, where the prototype specifications were determined. Finally, a basic dimensioning of the important components as heat exchangers (heater, cooler, and regenerator), piston, displacer and solar collector was elaborated. The principal conclusions were that the different analysis methods had dissimilitude among their results; in this sense, a construction of the prototype is necessary for the understanding of the complex phenomena occurring inside the engineItem Open Access Design of a flow deflector for an accurate flow meter calibration facility(FEDSM2000 FORUM ON FLUID MEASURENMENT AND INTRUMENTATION BOSTON, MASSACHUSETTS, ON JUNE 11-15, 2000, 2000-06-11) Corrales-Barallobre, C.; Martínez-Huen, R.; Alvarez, L.; Polanco, G.; Rojas-Solorzano, L.The design and test of a flow deflector gate used for controlling the flow deviation toward the primary tank in a flow-meter calibration facility is presented. The deflector gate is pneumatically controlled and permits the flow conduction to either the suction tank or to the primary tank. The deflector is designed to approximately compensate the flow deficit towards the primary tank during the opening, with the flow excess while in the shutting process. Numerical simulations are performed to study the flow hydrodynamics during the deflector operation. Results are compared to experimental data, and used to improve the gate design. The enhanced design proved to guarantee the uniformity of the flow through the calibration section and the dramatic reduction of the error in volume measurement during calibration.Item Open Access Design of a large scale flow-meter test and calibration facility(FEDSM2000 FORUM ON FLUID MEASURENMENT AND INTRUMENTATION BOSTON, MASSACHUSETTS, ON JUNE 11-15, 2000, 2000-06-11) Corrales-Barallobre, C.; Martínez-Huen, R.; Alvarez, Luis; Polanco, G.; Rojas-Solorzano, L.The design and set up of a large-scale flowmeter calibration and test facility is presented. The facility was designed to handle flowmeters with diameters between 6” and 14”, flow rates up to 0.3 m3/s and to give results less than 1% accurate. The calibration methodology consisted firstly in calibrating the pattern flowmeters, using volume and time primary measurements, and secondly, comparing the pattern to the flowmeters needing calibration. The design and calculation of the primary calibration device is addressed, including numerical simulations of the outflow manifold and the comparison to experimental data. The calibration facility proved to be accurate and reliable in producing renewed calibration data for various tested flowmetersItem Open Access Design of the distribution manifold for a large-scale flowmeter calibration facility(FEDSM2000 FORUM ON FLUID MEASURENMENT AND INSTRUMENTATION BOSTON, MASSACHUSETTS, ON JUNE 11-15, 2000, 2000-06-11) Corrales-Barallobre, C.; Martínez-Huen, R.; Alvarez, Luis; Polanco, G.; Rojas-Solorzano, L.The design and test of the distribution manifold for a large-scale flowmeter calibration facility is presented. The design was intended to have an air-free flow operation and a free-surface flow-like towards the downstream half-body discharge. Back of the envelope calculations are presented for the estimation of the preliminary dimensions. Numerical simulations of the flow during manifold steady state operation are utilized to refine the manifold design. No air entrapment is noticed in the flow simulationItem Open Access Detection of the vegetation change cover using landsat TM5 in the Burabay State National Natural Park, Kazakhstan(International Scientific and Practical Conference "Geosystemic approach to the study of the natural environment of the Republic of Kazakhstan", 2018-04-13) Taibassarova, Zh.The SNNP «Burabay» is the famous touristic place in Kazakhstan, where the frequent climate change and anthropogenic activities has a significant impact in land cover change. Especially, there is significant impact on vegetation lost and these changes have a detrimental impact on biodiversity, as SNPP is defined as a home for 305 animal species and 800 flora species (https: // kazakhstan.orexca.com/ national park burabay.shtml). The tourism industry has become the dominant contributor to Burabay»s development, so many vegetated areas, green spaces are reducing in order to build hotels, restaurants and different types of entertainment centres. Thus, the SNNP « Burabay» is under the control of the International Union for Conservation of Nature (1UCN) in the category 2 which aims: «to protect biodiversity along with its underlying ecological structure and supporting environmental processes, and to promote education and recreation)) (1UCN, 2017 https://www.iucn.org/).