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Passive micromixers are miniaturized instruments that are used to mix fluids in microfluidic systems. In microchannels, combination of laminar flows and small diffusion constants of mixing liquids produce a difficult mixing environment. In particular, in very low Reynolds number flows, e.g., Re < 10, diffusive mixing cannot be promoted unless a large interfacial area is formed between the fluids to be mixed. Therefore, the mixing distance increases substantially due to a slow diffusion process that governs fluid mixing. In this article, a novel 3-D passive micromixer design is developed to improve fluid mixing over a short distance. Computational Fluid Dynamics (CFD) simulations are used to investigate the performance of the micromixer numerically. The circular-shaped fluid overlapping (CSFO) micromixer design proposed is examined in several fluid flow, diffusivity, and injection conditions. The outcomes show that the CSFO geometry develops a large interfacial area between the fluid bodies. Thus, fluid mixing is accelerated in vertical and/or horizontal directions depending on the injection type applied. For the smallest molecular diffusion constant tested, the CSFO micromixer design provides more than 90% mixing efficiency in a distance between 260 and 470 µm. The maximum pressure drop in the micromixer is found to be less than 1.4 kPa in the highest flow conditioned examined.
Mahmut Okuducu; Mustafa Aral. Toward the Next Generation of Passive Micromixers: A Novel 3-D Design Approach. Micromachines 2021, 12, 372 .
AMA StyleMahmut Okuducu, Mustafa Aral. Toward the Next Generation of Passive Micromixers: A Novel 3-D Design Approach. Micromachines. 2021; 12 (4):372.
Chicago/Turabian StyleMahmut Okuducu; Mustafa Aral. 2021. "Toward the Next Generation of Passive Micromixers: A Novel 3-D Design Approach." Micromachines 12, no. 4: 372.
In this study, a perforated baffle design is proposed to improve mixing in contact tanks. Turbulent flow through the perforated baffle is studied at the perforation hole scale. The contribution of jets emerging from the perforations to the mixing process is evaluated in terms of standard mixing indexes for various perforation parameters, such as the solidity ratio and hole diameter. Based on numerical simulation results, the two sets of perforated baffles that yielded the highest performance were manufactured from polycarbonate and tracer studies were conducted on a laboratory model. Comparison of numerical and experimental results demonstrates that the numerical model developed is reliable in simulating the flow through the perforated baffles and the associated mixing level in the contact tank. Numerical simulations indicate that the jet flow structure through the perforated baffle penetrates to the recirculation zones in the neighboring chambers and turns the dead zones into active mixing zones. Furthermore, large scale turbulent eddies shed by the perforations contribute to the mixing process in the chambers of the tank. With the use of the perforated baffle design, it is shown that the hydraulic efficiency of the tank can be improved from average to superior according to the baffling factor, and the associated mixing in the proposed design can be improved by 31% according to the Morrill index.
Nazhmiddin Nasyrlayev; M. Anil Kizilaslan; A. Tolga Kurumus; Ender Demirel; Mustafa M. Aral. A Perforated Baffle Design to Improve Mixing in Contact Tanks. Water 2020, 12, 1022 .
AMA StyleNazhmiddin Nasyrlayev, M. Anil Kizilaslan, A. Tolga Kurumus, Ender Demirel, Mustafa M. Aral. A Perforated Baffle Design to Improve Mixing in Contact Tanks. Water. 2020; 12 (4):1022.
Chicago/Turabian StyleNazhmiddin Nasyrlayev; M. Anil Kizilaslan; A. Tolga Kurumus; Ender Demirel; Mustafa M. Aral. 2020. "A Perforated Baffle Design to Improve Mixing in Contact Tanks." Water 12, no. 4: 1022.
Interaction of recirculating and mean flow downstream of a submerged gate may form significant vortex structures, which may affect the stability of the gate. Although these flow structures that appear in submerged hydraulic jumps received considerable attention in the literature, relatively less work was devoted to the analysis and suppression of the vortex structures downstream of a submerged gate. In this work, internal flow structure and vortex dynamics around a submerged gate were investigated through laboratory tests and large-eddy simulation (LES) using computational fluid dynamics (CFD). It is shown that numerical results obtained for mean velocity field are in good agreement with the experimental measurements. A helical vortex pair connected with a horseshoe vortex system was identified within the roller region using high-resolution numerical simulations. Damping performance of different types of anti-vortex elements placed on the downstream face of the gate are evaluated based on numerical studies. It is shown that the horizontal porous baffle mounted at an elevation below the free surface reduced the vortex magnitudes in the roller region by 26.8%. With the implementation of the proposed vortex breaker, lift forces acting on the gate lip were reduced by 9.4% and drag forces acting on the downstream face of the gate were reduced by 8.6%. Finally, in this study, we assess the performance of the vortex breaker under different flow conditions.
Ender Demirel; Mustafa M. Aral. A Design for Vortex Suppression Downstream of a Submerged Gate. Water 2020, 12, 750 .
AMA StyleEnder Demirel, Mustafa M. Aral. A Design for Vortex Suppression Downstream of a Submerged Gate. Water. 2020; 12 (3):750.
Chicago/Turabian StyleEnder Demirel; Mustafa M. Aral. 2020. "A Design for Vortex Suppression Downstream of a Submerged Gate." Water 12, no. 3: 750.
Continental migration studies range from elaborate recording of periodic migration data to regression analysis to statistical models that may combine several sources of quantitative and qualitative data. It is the writer's observation that continuous mathematical modeling has not been attempted to estimate continental migration because of the complexity of the governing mathematical models. In this study the writer proposes a continuous mathematical model to estimate continental population and migration trends. The proposed model is based on knowledge-based population dynamics model developed earlier which was used to estimate global population levels and stability of world population under various stress scenarios. In this study one of these models are extended to include continental population and continental migration concepts. Resulting mathematical model is calibrated using historical continental population data which is a reliable data source. If historical continental migration is a zero-sum process, the outcome of the calibrated model yields continental population growth and intercontinental migration estimates. Results obtained are in line with global projections that are made in other studies. The proposed model is also used for future projections.
Mustafa M. Aral. Knowledge based analysis of continental population and migration dynamics. Technological Forecasting and Social Change 2019, 151, 119848 .
AMA StyleMustafa M. Aral. Knowledge based analysis of continental population and migration dynamics. Technological Forecasting and Social Change. 2019; 151 ():119848.
Chicago/Turabian StyleMustafa M. Aral. 2019. "Knowledge based analysis of continental population and migration dynamics." Technological Forecasting and Social Change 151, no. : 119848.
In this paper, human security-related causes of large-scale forced migration (LSFM) in Africa are investigated for the period 2011–2017. As distinct from the conventional understanding of (national) security, human security involves economic, public health, environmental and other aspects of people’s wellbeing. Testing various hypotheses, we have found that civil and interstate conflicts, lack of democracy and poverty are the most important drivers of mass population displacements, whereas climate change has an indirect effect on the dependent variable. As a policy tool, foreign aid is also tested to see if it lowers the probability of LSFM. Our findings have implications for policy planning, since the conventional understanding of security falls short of addressing LSFM without taking various aspects of human security into account.
Murat Bayar; Mustafa M. Aral. An Analysis of Large-Scale Forced Migration in Africa. International Journal of Environmental Research and Public Health 2019, 16, 4210 .
AMA StyleMurat Bayar, Mustafa M. Aral. An Analysis of Large-Scale Forced Migration in Africa. International Journal of Environmental Research and Public Health. 2019; 16 (21):4210.
Chicago/Turabian StyleMurat Bayar; Mustafa M. Aral. 2019. "An Analysis of Large-Scale Forced Migration in Africa." International Journal of Environmental Research and Public Health 16, no. 21: 4210.
Laminar fluid flow and advection-dominant transport produce ineffective mixing conditions in micromixers. In these systems, a desirable fluid mixing over a short distance may be achieved using special geometries in which complex flow paths are generated. In this paper, a novel design, utilizing semi-circular ridges, is proposed to improve mixing in micro channels. Fluid flow and scalar transport are investigated employing Computational Fluid Dynamics (CFD) tool. Mixing dynamics are investigated in detail for alternative designs, injection, and diffusivity conditions. Results indicate that the convex alignment of semi-circular elements yields a specific, helicoidal-shaped fluid flow along the mixing channel which in turn enhances fluid mixing. In all cases examined, homogenous concentration distributions with mixing index values over 80% are obtained. When it is compared to the classical T-shaped micromixer, the novel design increases mixing index and mixing performance values by the factors of 8.7 and 3.3, respectively. It is also shown that different orientations of ridges adversely affect the mixing efficiency by disturbing the formation of helicoidal-shaped flow profile.
Mahmut Burak Okuducu; Mustafa M. Aral. Novel 3-D T-Shaped Passive Micromixer Design with Helicoidal Flows. Processes 2019, 7, 637 .
AMA StyleMahmut Burak Okuducu, Mustafa M. Aral. Novel 3-D T-Shaped Passive Micromixer Design with Helicoidal Flows. Processes. 2019; 7 (9):637.
Chicago/Turabian StyleMahmut Burak Okuducu; Mustafa M. Aral. 2019. "Novel 3-D T-Shaped Passive Micromixer Design with Helicoidal Flows." Processes 7, no. 9: 637.
The mixing and disinfection performance of a full-scale chlorine contact tank (CCT) is thoroughly investigated by means of numerical simulations for seasonal water supply variations in the water treatment plant (WTP) of Eskisehir in Turkey. Velocity measurements and tracer studies are carried out on a 1:10 scale laboratory model of the CCT to validate the numerical model. A good agreement between numerical and experimental results shows that the numerical model developed can be reliably used for the simulation of turbulent flow and solute transport in the full-scale CCT. Tracer studies indicate that the hydraulic performance of the CCT is classified as “average” according to the baffling factor, while the Morrill, Aral-Demirel (AD), and dispersion indexes indicate low mixing due to the recirculating and short-circuiting effects inside the chambers of the CCT. With respect to the first order modeling of chlorine decay and pathogen inactivation, chlorine concentrations are found to be significantly distinct for seasonal variations in water supply to maintain 3-log inactivation of Giardia cysts. A recently developed and patented slot-baffle design (SBD) is then applied to the full-scale CCT. It is found that the hydraulic efficiency of the CCT is improved to “high” and the Morrill index approaches 2, which identifies the system as a perfect mixing tank. Using the SBD, the chlorine demand has been successfully decreased by 19% while providing equivalent inactivation level. The novel SBD design also reduces energy loses in the turbulent flow through the tank and increases the energy efficiency of the CCT by 62%, which is significant for energy considerations in modern cities.
M. Anil Kizilaslan; Ender Demirel; Mustafa Aral; Aral. Efficiency Enhancement of Chlorine Contact Tanks in Water Treatment Plants: A Full-Scale Application. Processes 2019, 7, 551 .
AMA StyleM. Anil Kizilaslan, Ender Demirel, Mustafa Aral, Aral. Efficiency Enhancement of Chlorine Contact Tanks in Water Treatment Plants: A Full-Scale Application. Processes. 2019; 7 (9):551.
Chicago/Turabian StyleM. Anil Kizilaslan; Ender Demirel; Mustafa Aral; Aral. 2019. "Efficiency Enhancement of Chlorine Contact Tanks in Water Treatment Plants: A Full-Scale Application." Processes 7, no. 9: 551.
Computational Fluid Dynamics (CFD) tools are used to investigate fluid flow and scalar mixing in micromixers where low molecular diffusivities yield advection dominant transport. In these applications, achieving a numerical solution is challenging. Numerical procedures used to overcome these difficulties may cause misevaluation of the mixing process. Evaluation of the mixing performance of these devices without appropriate analysis of the contribution of numerical diffusion yields over estimation of mixing performance. In this study, two- and four-inlet swirl-generating micromixers are examined for different mesh density, flow and molecular diffusivity scenarios. It is shown that mesh densities need to be high enough to reveal numerical diffusion errors in scalar transport simulations. Two-inlet micromixer design was found to produce higher numerical diffusion. In both micromixer configurations, when cell Peclet numbers were around 50 and 100 for Reynolds numbers 240 and 120, the numerical diffusion effects were tolerable. However, when large cell Peclet number scenarios were tested, it was found that the molecular diffusivity of the fluid is completely masked by false diffusion errors.
Mahmut Burak Okuducu; Mustafa M. Aral. Computational Evaluation of Mixing Performance in 3-D Swirl-Generating Passive Micromixers. Processes 2019, 7, 121 .
AMA StyleMahmut Burak Okuducu, Mustafa M. Aral. Computational Evaluation of Mixing Performance in 3-D Swirl-Generating Passive Micromixers. Processes. 2019; 7 (3):121.
Chicago/Turabian StyleMahmut Burak Okuducu; Mustafa M. Aral. 2019. "Computational Evaluation of Mixing Performance in 3-D Swirl-Generating Passive Micromixers." Processes 7, no. 3: 121.
A slot-baffle design used in water treatment tanks previously developed by the authors is used to suppress sloshing effects in an accelerated tank. This new application is another example of the versatility of the slot-baffle design in inducing turbulence in fluid flow systems, which has numerous uses in engineering applications. Large amplitude surface waves in a harmonically excited tank are simulated using a second-order accurate numerical model in OpenFOAM. The verification of the numerical model is performed by comparing the numerical results with existing laboratory measurements, which show a favorable agreement. Various slot configurations are studied in order to evaluate the damping performance during the external excitation of the tank. It is shown that the present design shows an effective dissipation performance in a broad range of oscillation frequencies, while 88% of the internal kinetic energy of the liquid is dissipated over thirty oscillation periods for the resonance case.
Ender Demirel; Mustafa M. Aral. Liquid Sloshing Damping in an Accelerated Tank Using a Novel Slot-Baffle Design. Water 2018, 10, 1565 .
AMA StyleEnder Demirel, Mustafa M. Aral. Liquid Sloshing Damping in an Accelerated Tank Using a Novel Slot-Baffle Design. Water. 2018; 10 (11):1565.
Chicago/Turabian StyleEnder Demirel; Mustafa M. Aral. 2018. "Liquid Sloshing Damping in an Accelerated Tank Using a Novel Slot-Baffle Design." Water 10, no. 11: 1565.
Micro hydropower generators (micro turbines), are used to recover excess energy from hydraulic systems and these applications have important potential in renewable energy production. One of the most viable environments for the use of micro turbines is the water distribution network where, by design, there is always excess energy since minimum pressures are to be maintained throughout the system, and the system is designed to meet future water supply needs of a planning period. Under these circumstances, maintaining the target pressures is not an easy task due to the increasing complexity of the water distribution network to supply future demands. As a result, pressures at several locations of the network tend to be higher than the required minimum pressures. In this paper, we outline a methodology to recover this excess energy using smart operation management and the best placement of micro turbines in the system. In this approach, the best micro turbine locations and their operation schedule is determined to recover as much available excess energy as possible from the water distribution network while satisfying the current demand for water supply and pressure. Genetic algorithms (GAs) are used to obtain optimal solutions and a “smart seeding” approach is developed to improve the performance of the GA. The Dover Township pump-driven water distribution system in New Jersey, United States of America (USA) was selected as the study area to test the proposed methodology. This pump-driven network was also converted into a hypothetical gravity-driven network to observe the differences between the energy recovery potential of the pump-driven and gravity-driven systems. The performance of the energy recovery system was evaluated by calculating the equivalent number of average American homes that can be fed by the energy produced and the resulting carbon-dioxide emission reductions that may be achieved. The results show that this approach is an effective tool for applications in renewable energy production in water distribution systems for small towns such as Dover Township. It is expected that, for larger water distribution systems with high energy usage, the energy recovery potential will be much higher.
Ilker T. Telci; Mustafa M. Aral. Optimal Energy Recovery from Water Distribution Systems Using Smart Operation Scheduling. Water 2018, 10, 1464 .
AMA StyleIlker T. Telci, Mustafa M. Aral. Optimal Energy Recovery from Water Distribution Systems Using Smart Operation Scheduling. Water. 2018; 10 (10):1464.
Chicago/Turabian StyleIlker T. Telci; Mustafa M. Aral. 2018. "Optimal Energy Recovery from Water Distribution Systems Using Smart Operation Scheduling." Water 10, no. 10: 1464.
Hydraulic and mixing efficiencies of contact tanks are evaluated using several indexes that are used in the literature. These indexes emphasize different aspects of flow and mixing processes in the mixing tank at different scales. Uniformity of the evaluations obtained from these indexes is necessary for unified characterization of the overall performance of contact tanks, which is very difficult to achieve. In this study, several contact tanks with different baffling configurations were studied using computational fluid dynamics (CFD) analysis in which three-dimensional hydrodynamic analysis of flow and transport of a conservative tracer within the flow field were studied. The performance data developed were extended by including the outcome of some of the earlier studies that are reported in the literature. The most common indexes that are used in the literature were used to evaluate the performance of these cases. The results indicate that the performance evaluation obtained for these cases was not consistent for all indexes. An analysis was performed to identify the suitability of the performance indexes for a specific performance parameter. Performance of the newly introduced AD index, which yields more consistent evaluations for both short-circuiting and dispersion evaluation in the contact tank, was compared with the performance of the Morrill index. A dimensionless energy-efficiency index was also proposed for the evaluation of the efficiency of the flow-through system in the tank.
Ender Demirel; Mustafa M. Aral. Performance of Efficiency Indexes for Contact Tanks. Journal of Environmental Engineering 2018, 144, 04018076 .
AMA StyleEnder Demirel, Mustafa M. Aral. Performance of Efficiency Indexes for Contact Tanks. Journal of Environmental Engineering. 2018; 144 (9):04018076.
Chicago/Turabian StyleEnder Demirel; Mustafa M. Aral. 2018. "Performance of Efficiency Indexes for Contact Tanks." Journal of Environmental Engineering 144, no. 9: 04018076.
Three-dimensional numerical simulations are performed to evaluate the effect of porous baffles on the efficiency of water treatment contact tanks. A second-order accurate numerical model is employed for the solutions of unsteady flow and tracer transport through the porous baffles. The flow through the porous medium is characterized while using the Darcy-Forchheimer relationship. Large Eddy Simulation (LES) model is used to simulate the instantaneous mixing of the tracer in the chambers of the contact tank. Three different porosities are considered to evaluate the effect of porosity on the hydraulic and mixing efficiencies of the contact tank. Simulated time-averaged flow field shows that porous baffles that are placed at the entrance of each chamber could successfully mitigate short-circuiting and yield plug-flow conditions through the system for low porosities. Flow in the contact tank becomes laminar as the flow velocities decrease due to viscous effects and inertial resistance in the porous zone. For this case, the tracer is transported with bulk flow through the system and leaves the contact tank with a high peak seen in the Residence Time Distribution (RTD) plot. Porous layer increases the hydraulic efficiency of the conventional design from “poor” to “good” according to the baffling factor and increases the overall efficiency from “compromising” to “good” according to the AD index. Comparison of the performance of the porous layer with the previously developed slot-baffle design shows that the slot-baffle design increases the efficiency of the tank with increasing dispersion effects, whereas the porous design increases hydraulic efficiency and reduces the dispersion effects. While the porous design reduces energy efficiency by 33% due to a drastic increase in drag in the flow through porous zone, the slot-baffle design increases the energy efficiency of the conventional design by 67%.
M. Anil Kizilaslan; Ender Demirel; Mustafa M. Aral. Effect of Porous Baffles on the Energy Performance of Contact Tanks in Water Treatment. Water 2018, 10, 1084 .
AMA StyleM. Anil Kizilaslan, Ender Demirel, Mustafa M. Aral. Effect of Porous Baffles on the Energy Performance of Contact Tanks in Water Treatment. Water. 2018; 10 (8):1084.
Chicago/Turabian StyleM. Anil Kizilaslan; Ender Demirel; Mustafa M. Aral. 2018. "Effect of Porous Baffles on the Energy Performance of Contact Tanks in Water Treatment." Water 10, no. 8: 1084.
In micromixer devices, laminar characteristics of the flow domain and small diffusion constants of the fluid samples that are mixed characterize the mixing process. The advection dominant flow and transport processes that develop in these devices not only create significant challenges for numerical solution of the problem, but they are also the source of numerical errors which may lead to confusing performance evaluations that are reported in the literature. In this study, the finite volume method (FVM) and finite element method (FEM) are used to characterize these errors and critical issues in numerical performance evaluations are highlighted. In this study, we used numerical methods to evaluate the mixing characteristics of a typical T-shape passive micromixer for several flow and transport parameters using both FEM and FVM, although the numerical procedures described are also equally applicable to other geometric designs as well. The outcome of the study shows that the type of stabilization technique used in FEM is very important and should be documented and reported. Otherwise, erroneous mixing performance may be reported since the added artificial diffusion may significantly affect the mixing performance in the device. Similarly, when FVM methods are used, numerical diffusion errors may become important for certain unstructured discretization techniques that are used in the idealization of the solution domain. This point needs to be also analyzed and reported when FVM is used in performance evaluation of micromixer devices. The focus of this study is not on improving the mixing performance of micromixers. Instead, we highlight the bench scale characteristics of the solutions and the mixing evaluation procedures used when FVM and FEM are employed.
Mahmut Burak Okuducu; Mustafa M. Aral. Performance Analysis and Numerical Evaluation of Mixing in 3-D T-Shape Passive Micromixers. Micromachines 2018, 9, 210 .
AMA StyleMahmut Burak Okuducu, Mustafa M. Aral. Performance Analysis and Numerical Evaluation of Mixing in 3-D T-Shape Passive Micromixers. Micromachines. 2018; 9 (5):210.
Chicago/Turabian StyleMahmut Burak Okuducu; Mustafa M. Aral. 2018. "Performance Analysis and Numerical Evaluation of Mixing in 3-D T-Shape Passive Micromixers." Micromachines 9, no. 5: 210.
Bu çalışmada bir temas tankının içindeki türbülanslı akış ile arıtıcı konsantrasyonunun hareketinin üç boyutlu sayısal benzetimi ikinci mertebeden yakınsak bir hesaplama modeli kullanılarak gerçekleştirilmiştir. Arıtıcının zamanla değişen akım ile karışımı Large Eddy Simulation (LES) türbülans yaklaşımı kullanılarak modellenmiştir. Temas tankının girişinden enjekte edilen arıtıcı konsantrasyonunun tankın çıkışındaki dağılımını gösteren Kalma Süresi Dağılımı (KSD) ve toplam KSD eğrileri kullanılarak temas tankının hidrolik ve karışım verimlerine ait endeksler belirlenmiştir. Tank içindeki şaşırtma perdeleri üzerinde yapılan değişiklik ile temas sisteminin verimi arttırılarak enerji sarfiyatlarının azaltılabileceği gösterilmiştir. Önerilen yeni perde tasarımı sayesinde temas tankının hidrolik verimi %44, karışım verimi ise %42 oranında arttırılmış, suyun iletilmesi için gereken enerji sarfiyatı ise %43 oranında azaltılmıştır.
Doç.Dr. Ender Demirel; Dr. Mustafa Mehmet Aral. An Efficient Contact Tank Design for Potable Water Treatment. Teknik Dergi 2018, 29, 1 .
AMA StyleDoç.Dr. Ender Demirel, Dr. Mustafa Mehmet Aral. An Efficient Contact Tank Design for Potable Water Treatment. Teknik Dergi. 2018; 29 (2):1.
Chicago/Turabian StyleDoç.Dr. Ender Demirel; Dr. Mustafa Mehmet Aral. 2018. "An Efficient Contact Tank Design for Potable Water Treatment." Teknik Dergi 29, no. 2: 1.
Mustafa Aral; Ender Demirel. Novel Slot-Baffle Design to Improve Mixing Efficiency and Reduce Cost of Disinfection in Drinking Water Treatment. Journal of Environmental Engineering 2017, 143, 06017006 .
AMA StyleMustafa Aral, Ender Demirel. Novel Slot-Baffle Design to Improve Mixing Efficiency and Reduce Cost of Disinfection in Drinking Water Treatment. Journal of Environmental Engineering. 2017; 143 (9):06017006.
Chicago/Turabian StyleMustafa Aral; Ender Demirel. 2017. "Novel Slot-Baffle Design to Improve Mixing Efficiency and Reduce Cost of Disinfection in Drinking Water Treatment." Journal of Environmental Engineering 143, no. 9: 06017006.
Mahmut Burak Okuducu; Mustafa M. Aral. Knowledge based dynamic human population models. Technological Forecasting and Social Change 2017, 122, 1 -11.
AMA StyleMahmut Burak Okuducu, Mustafa M. Aral. Knowledge based dynamic human population models. Technological Forecasting and Social Change. 2017; 122 ():1-11.
Chicago/Turabian StyleMahmut Burak Okuducu; Mustafa M. Aral. 2017. "Knowledge based dynamic human population models." Technological Forecasting and Social Change 122, no. : 1-11.
The inundation impact of sea level rise (SLR) is critical, since coastal regions of Europe house important critical infrastructures and large population centers. According to International Panel on Climate Change (IPCC) studies, the analysis of the SLR problem is complicated. Beyond the reported complexities involved in the analysis of this phenomenon, the expected spatial variability of SLR in oceans further complicates this analysis. Spatial variability of SLR in oceans is both observed and also expected, according to IPCC studies. Estimation of spatial variation of SLR in oceans is necessary to identify the level of potential threats that may impact different coastline regions. Identification of geographic patterns of SLR based on local coastal data has been reported in the literature. Unfortunately, these estimates cannot be used in predictive analysis over a century. Thus, the solution of this problem using mathematical models is the other alternative that can be employed. Modeling solutions to this problem is currently in its infancy, and further studies in this field are needed. In this study, a methodology developed by the authors is used to estimate the SLR for the Atlantic and the Mediterranean coastline of Europe that also includes the other oceans. This effort utilizes the dynamic system model (DSM) with spatial analysis capability (S-DSM) to predict the regional sea level change. Results obtained provide consistent assessment of spatial variability of SLR pattern in oceans as well as the temperature changes over the 21st century. This approach may also be used in other coastal regions to aid management decision in a timely manner.
Mustafa M. Aral; Biao Chang. Spatial Variation of Sea Level Rise at Atlantic and Mediterranean Coastline of Europe. Water 2017, 9, 522 .
AMA StyleMustafa M. Aral, Biao Chang. Spatial Variation of Sea Level Rise at Atlantic and Mediterranean Coastline of Europe. Water. 2017; 9 (7):522.
Chicago/Turabian StyleMustafa M. Aral; Biao Chang. 2017. "Spatial Variation of Sea Level Rise at Atlantic and Mediterranean Coastline of Europe." Water 9, no. 7: 522.
Water quality is an important aspect of health assessment of rivers, lakes, and estuaries, which requires systematic data collection from various components of the aquatic environment. The analysis of this data is used to judge the health state of these environments. It is well known that long-term surveillance of surface waters is costly. Thus, sound strategies are necessary to select the best locations of monitoring stations to collect the most reliable data efficiently to improve the performance of a monitoring system. This can be accomplished by optimizing the location of monitoring stations with respect to the hydrodynamic and transport characteristics of the surface water system. It is expected that such an approach may improve the effectiveness and also reduce the overall cost of the monitoring system. Since the hydrodynamics and the contaminant migration pathways in surface waters are complex, the optimal solution of this problem is also complex. To analyze this problem, a two-dimensional hydrodynamic simulation model is developed using the finite-element method. The best monitoring locations are selected that minimize the detection time of the potential contaminant presence in the surface water body and maximizes the reliability of the system performance. Due to the nonlinear nature of the hydrodynamics, a genetic algorithm (GA) is used for the solution of the optimization problem. Examples are provided for wind-driven hydraulic circulation for a circular lake, and tidal and wind-driven circulation in a natural tidal estuary.
Mustafa Aral; Kijin Nam. Optimal Monitoring Network Design for Wind-Driven and Tidal Estuaries. Journal of Environmental Engineering 2016, 142, 1 .
AMA StyleMustafa Aral, Kijin Nam. Optimal Monitoring Network Design for Wind-Driven and Tidal Estuaries. Journal of Environmental Engineering. 2016; 142 (12):1.
Chicago/Turabian StyleMustafa Aral; Kijin Nam. 2016. "Optimal Monitoring Network Design for Wind-Driven and Tidal Estuaries." Journal of Environmental Engineering 142, no. 12: 1.
Mixing characteristics of multi-chambered contact tank are analyzed employing the validated three-dimensional numerical model developed in the companion paper. Based on the flow characterization, novel volumetric mixing efficiency definitions are proposed for the assessment of the hydrodynamic and chemical transport properties of the contact tank and its chambers. Residence time distribution functions are analyzed not only at the outlet of each chamber but also inside the chambers using the efficiency definitions for both Reynolds averaged Navier–Stokes (RANS) and large eddy simulation (LES) results. A novel tracer mixing index is defined to characterize short circuiting and mixing effects of the contact system. Comparisons of the results of these indexes for RANS and LES solutions indicate that mixing characteristics are stronger in LES due to the unsteady turbulent eddy mixing even though short circuiting effects are also more prominent in LES results. This result indicates that the mixing analysis based on the LES results simulates the mixing characteristics instantaneously, which is more realistic than that in RANS. Since LES analysis can capture turbulent eddy mixing better than RANS analysis, the interaction of recirculation and jet zones are captured more effectively in LES, which tends to predict higher turbulent mixing in the contact system. The analysis also shows that the mixing efficiency of each chamber of the contact tank is different, thus it is necessary to consider distinct chemical release and volumetric designs for each chamber in order to maximize the mixing efficiency of the overall process in a contact tank system.
Ender Demirel; Mustafa M. Aral. Unified Analysis of Multi-Chamber Contact Tanks and Mixing Efficiency Evaluation Based on Vorticity Field. Part II: Transport Analysis. Water 2016, 8, 537 .
AMA StyleEnder Demirel, Mustafa M. Aral. Unified Analysis of Multi-Chamber Contact Tanks and Mixing Efficiency Evaluation Based on Vorticity Field. Part II: Transport Analysis. Water. 2016; 8 (11):537.
Chicago/Turabian StyleEnder Demirel; Mustafa M. Aral. 2016. "Unified Analysis of Multi-Chamber Contact Tanks and Mixing Efficiency Evaluation Based on Vorticity Field. Part II: Transport Analysis." Water 8, no. 11: 537.
Prediction of global temperatures and sea level rise (SLR) is important for sustainable development planning of coastal regions of the world and the health and safety of communities living in these regions. In this study, climate change effects on sea level rise is investigated using a dynamic system model (DSM) with time lag on historical input data. A time-invariant (TI-DSM) and time-variant dynamic system model (TV-DSM) with time lag is developed to predict global temperatures and SLR in the 21st century. The proposed model is an extension of the DSM developed by the authors. The proposed model includes the effect of temperature and sea level states of several previous years on the current temperature and sea level over stationary and also moving scale time periods. The optimal time lag period used in the model is determined by minimizing a synthetic performance index comprised of the root mean square error and coefficient of determination which is a measure for the reliability of the predictions. Historical records of global temperature and sea level from 1880 to 2001 are used to calibrate the model. The optimal time lag is determined to be eight years, based on the performance measures. The calibrated model was then used to predict the global temperature and sea levels in the 21st century using a fixed time lag period and moving scale time lag periods. To evaluate the adverse effect of greenhouse gas emissions on SLR, the proposed model was also uncoupled to project the SLR based on global temperatures that are obtained from the Intergovernmental Panel on Climate Change (IPCC) emission scenarios. The projected SLR estimates for the 21st century are presented comparatively with the predictions made in previous studies.
Mustafa Aral; Jiabao Guan. Global Sea Surface Temperature and Sea Level Rise Estimation with Optimal Historical Time Lag Data. Water 2016, 8, 519 .
AMA StyleMustafa Aral, Jiabao Guan. Global Sea Surface Temperature and Sea Level Rise Estimation with Optimal Historical Time Lag Data. Water. 2016; 8 (11):519.
Chicago/Turabian StyleMustafa Aral; Jiabao Guan. 2016. "Global Sea Surface Temperature and Sea Level Rise Estimation with Optimal Historical Time Lag Data." Water 8, no. 11: 519.