Journal articles on the topic '2D inflow problem'
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Alekseev, Aleksey K. "2D inverse convection dominated problem for estimation of inflow parameters from outflow measurements." Inverse Problems in Engineering 8, no. 5 (October 2000): 413–34. http://dx.doi.org/10.1080/174159700088027739.
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Fröhlich, Jürg. "Chiral Anomaly, Topological Field Theory, and Novel States of Matter." Reviews in Mathematical Physics 30, no. 06 (July 2018): 1840007. http://dx.doi.org/10.1142/s0129055x1840007x.
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Starting with a description of the motivation underlying the analysis presented in this paper and a brief survey of the chiral anomaly, I proceed to review some basic elements of the theory of the quantum Hall effect in 2D incompressible electron gases in an external magnetic field, (“Hall insulators”). I discuss the origin and role of anomalous chiral edge currents and of anomaly inflow in 2D insulators with explicitly or spontaneously broken time reversal, i.e. in Hall insulators and “Chern insulators”. The topological Chern–Simons action yielding the large-scale response equations for the 2D bulk of such states of matter is displayed. A classification of Hall insulators featuring quasi-particles with abelian braid statistics is sketched. Subsequently, the chiral edge spin currents encountered in some time-reversal invariant 2D topological insulators with spin-orbit interactions and the bulk response equations of such materials are described. A short digression into the theory of 3D topological insulators, including “axionic insulators”, follows next. To conclude, some open problems are described and a problem in cosmology related to axionic insulators is mentioned. As far as the quantum Hall effect and the spin currents in time-reversal invariant 2D topological insulators are concerned, this review is based on extensive work my collaborators and I carried out in the early 1990’s. Dedicated to the memory of Ludvig Dmitrievich Faddeev — a great scientist who will be remembered
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Bryan, George H., Nathan A. Dahl, David S. Nolan, and Richard Rotunno. "An Eddy Injection Method for Large-Eddy Simulations of Tornado-Like Vortices." Monthly Weather Review 145, no. 5 (May 1, 2017): 1937–61. http://dx.doi.org/10.1175/mwr-d-16-0339.1.
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Abstract The structure and intensity of tornado-like vortices are examined using large-eddy simulations (LES) in an idealized framework. The analysis focuses on whether the simulated boundary layer contains resolved turbulent eddies, and whether most of the vertical component of turbulent momentum flux is resolved rather than parameterized. Initial conditions are first generated numerically using a “precursor simulation” with an axisymmetric model. A three-dimensional “baseline” LES is then integrated using these initial conditions plus random perturbations. With this baseline approach, the inner core of the simulated vortex clearly contains resolved turbulent eddies (as expected); however, the boundary layer inflow has very weak resolved turbulent eddies, and the subgrid model accounts for most of the vertical turbulent momentum flux (contrary to the design of these simulations). To overcome this problem, a second precursor simulation is conducted in which resolved turbulent fluctuations develop within a smaller, doubly periodic LES domain. Perturbation flow fields from this precursor LES are then “injected” into the large-domain LES at a specified radius. With this approach, the boundary layer inflow clearly contains resolved turbulent fluctuations, often organized as quasi-2D rolls, which persist into the inner core of the simulation; thus, the simulated tornado-like vortex and its inflowing boundary layer can be characterized as LES. When turbulence is injected, the inner-core vortex structure is always substantially different, the boundary layer inflow is typically deeper, and in most cases the maximum wind speeds are reduced compared to the baseline simulation.
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Tao, Yuan, Xianjun Yu, and Baojie Liu. "A New Method for Rapid Optimization Design of a Subsonic Tandem Blade." Applied Sciences 10, no. 24 (December 9, 2020): 8802. http://dx.doi.org/10.3390/app10248802.
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Tandem blade technology has been developed for years due to its capacity to bear higher aerodynamics than conventional configurations. Even so, there is still the tough problem of how to design tandem blades effectively and further improve blade performance. This paper tries to further understand the flow characteristics of tandem blades in order to present a new method of designing them under subsonic inflow conditions. Firstly, efforts were made to reveal the aerodynamic interaction between the forward blade (FB) and the aft blade (AB). Secondly, considering this aerodynamic interaction, the design principles and the camber line modification method were put forward, with which typical controlled diffusion airfoil (CD airfoil) isentropic Mach number distributions can be achieved for both FB and AB. Lastly, the optimizations were conducted on a 2D tandem blade and a transonic compressor with a tandem blade, respectively. The computation fluid dynamic (CFD) results show that the optimized tandem blade achieves a significant improvement for both 2D blade performance and transonic compressor characteristics at low speeds.
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Ferrari, Alessia, Marco D'Oria, Renato Vacondio, Paolo Mignosa, and Maria Giovanna Tanda. "Hydrograph estimation at upstream ungauged sections on the Secchia River (Italy) by means of a parallel Bayesian inverse methodology." E3S Web of Conferences 40 (2018): 06034. http://dx.doi.org/10.1051/e3sconf/20184006034.
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In this work, we present a reverse flow routing procedure, which allows estimating discharge hydrographs at upstream ungauged stations by means of information available at downstream monitored sites. The reverse routing problem is solved adopting a Bayesian Geostatistical Approach (BGA). In order to capture the complex hydrodynamic field typical of many real cases of rivers including large floodable areas, meanwhile overcoming the computational time limitations, we adopted as forward model a selfdeveloped 2D-SWE parallel numerical model (PARFLOOD) that allows achieving ratio of physical to computational time of about 500-1000. To exploit the computational capabilities of modern GPU cluster, a parallel procedure to estimate the Jacobian matrix required by the BGA approach has been implemented. The inflow hydrograph in a river reach with several meanders and floodplains has been estimated in “only” 13 hours using a HPC cluster with 10 P100 Nvidia GPUs.
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de Kraker, Alex, Ron A. J. van Ostayen, A. van Beek, and Daniel J. Rixen. "A Multiscale Method Modeling Surface Texture Effects." Journal of Tribology 129, no. 2 (December 22, 2006): 221–30. http://dx.doi.org/10.1115/1.2540156.
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In this paper a multiscale method is presented that includes surface texture in a mixed lubrication journal bearing model. Recent publications have shown that the pressure generating effect of surface texture in bearings that operate in full film conditions may be the result of micro-cavitation and/or convective inertia. To include inertia effects, the Navier–Stokes equations have to be used instead of the Reynolds equation. It has been shown in earlier work (de Kraker et al., 2006, Tribol. Trans., in press) that the coupled two-dimensional (2D) Reynolds and 3D structure deformation problem with partial contact resulting from the soft EHL journal bearing model is not easy to solve due to the strong nonlinear coupling, especially for soft surfaces. Therefore, replacing the 2D Reynolds equation by the 3D Navier–Stokes equations in this coupled problem will need an enormous amount of computing power that is not readily available nowadays. In this paper, the development of a micro–macro multiscale method is described. The local (micro) flow effects for a single surface pocket are analyzed using the Navier–Stokes equations and compared to the Reynolds solution for a similar smooth piece of surface. It is shown how flow factors can be derived and added to the macroscopic smooth flow problem, that is modeled by the 2D Reynolds equation. The flow factors are a function of the operating conditions such as the ratio between the film height and the pocket dimensions, the surface velocity, and the pressure gradient over a surface texture unit cell. To account for an additional pressure buildup in the texture cell due to inertia effects, a pressure gain is introduced at macroscopic level. The method also allows for microcavitation. Microcavitation occurs when the pressure variation due to surface texture is larger than the average pressure level at that particular bearing location. In contrast with the work of Patir and Cheng (1978, J. Lubrication Technol., 78, pp. 1–10), where the microlevel is solved by the Reynolds equation, and the Navier–Stokes equations are used at the microlevel. Depending on the texture geometry and film height, the Reynolds equation may become invalid. A second pocket effect occurs when the pocket is located in the moving surface. In mixed lubrication, fluid can become trapped inside a pocket and squeezed out when the pocket is running into an area with higher contact load. To include this effect, an additional source term that represents the average fluid inflow due to the deformation of the surface around the pocket is added to the Reynolds equation at macrolevel. The additional inflow is computed at microlevel by numerical solution of the surface deformation for a single pocket that is subject to a contact load. The pocket volume is a function of the contact pressure. It must be emphasized that before ready-to-use results can be presented, a large number of simulations to determine the flow factors and pressure gain as a function of the texture parameters and operating conditions have yet to be done. Before conclusions can be drawn, regarding the dominanant mechanism(s), the flow factors and pressure gain have to be added to the macrobearing model. In this paper, only a limited number of preliminary illustrative simulation results, calculating the flow factors for a single 2D texture geometry, are shown to give insight into the method.
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Danileva, Natalia, Sergei Danilev, and Natalia Bolshakova. "Allocation of a deep-lying brine aquifer in the rocks of a chemogenic section based on the data of geophysical well logging and 2D seismic exploration." Записки Горного института 250 (September 29, 2021): 501–11. http://dx.doi.org/10.31897/pmi.2021.4.3.
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Advancement in the production of potassium fertilizers is an important strategic task of Russian agricultural industry. Given annually growing production rates, the reserves of discovered potassium-magnesium salt deposits are noticeably decreasing, which creates the need to ensure stable replenishment of the resource base through both the discovery of new deposits and the exploitation of deep-lying production horizons of the deposits that are already under development. In most cases, deposits of potassium-magnesium salts are developed by underground mining. The main problem for any salt deposit is water. Dry salt workings do not require any additional reinforcement and can easily withstand rock pressure, but with an inflow of water they begin to collapse intensively – hence, special attention is paid to mine waterproofing. Determination of spatial location, physical and mechanical properties of the aquifer and water-blocking stratum in the geological section represent an important stage in the exploration of a salt deposit. The results of these studies allow to validate an optimal system of deposit development that will minimize environmental and economic risks. On the territory of Russia, there is a deposit of potassium-magnesium salts with a unique geological structure – its production horizon lies at a considerable depth and is capped by a regional aquifer, which imposes significant limitations on the development process. To estimate parameters of the studied object, we analyzed the data from CDP seismic reflection survey and a suite of methods of radioactive and acoustic well logging, supplemented with high-frequency induction logging isoparametric sounding (VIKIZ) data. As a result of performed analysis, we identified location of the water-bearing stratum, estimated average thickness of the aquifers and possible water-blocking strata. Based on research results, we proposed methods for increasing operational reliability of the main shaft in the designed mine that will minimize the risks of water breakthrough into the mine shaft.
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Michal, Kriška, Němcová Miroslava, and Hyánková Eva. "The influence of ammonia on groundwater quality during wastewater irrigation." Soil and Water Research 13, No. 3 (July 2, 2018): 161–69. http://dx.doi.org/10.17221/124/2017-swr.
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Currently, agriculture in many countries including the Czech Republic is increasingly facing the problem of drought. The lack of precipitation results in a reduced harvest, which implies added irrigation and freshwater requirements. One of the ways to overcome the scarcity of fresh water is to search for alternative sources of irrigation water. The paper deals with a water source, which has not been preferred yet, but theoretically provides a wide application - treated municipal wastewater. Under a pilot plant, several selected soils were tested, placed in 2.0 m high filtration columns. Our observation was focused on ammonia nitrogen and its gradual decline during the flow through the soil profile. Samples from the filtration columns (inflow = irrigation; outflow = drainage water) were periodically taken, while the collected data were used for calibration of the numerical model. The model was calibrated in two successive separate steps, both were compiled in HYDRUS-2D. In the first step the model was calibrated according to the measured soil water content of materials. Subsequently, a second calibration was performed using the measured seepage concentrations of ammonia. Despite certain simplifications caused by the focus only on ammonia nitrogen, the model shows very favourable results. The hydraulic model’s goodness of fit (between observed vs. measured values of water content) is R<sup>2</sup> = 0.88 for sand, 0.76 for loam, 0.72 for sandy-loam with vegetation on surface and 0.74 for sandy-loam without vegetation. The calibrated hydraulic model for solute transport (between observed vs. measured values of NH<sub>4</sub><sup>+</sup>-N concentration) showed the value of R<sup>2</sup> = 0.89 for sand, 0.95 for loam, 0.95 for sandy-loam with vegetation on surface and 0.92 for sandy-loam without vegetation. The model provides significant information on the dependence of decrease of ammonia pollution by the depth. Inflow concentration of ammonia on surface 17 ± 1 mg/l is reduced to the value of 2.0 mg/l at a depth of 110 cm. It is crucial for real application to maintain the hydraulic criteria - the field capacity should not be exceeded in praxis. The value of field capacity was deliberately slightly exceeded because of understanding of the situation: how the pollution proceeds below if this rule is not followed. As a result, if wastewater is applied, the groundwater level should not be at a depth of less than 1.5 m.
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Niroshinie, M. A. C., Yasuo Nihei, Kazuaki Ohtsuki, and Shoji Okada. "Flood Inundation Analysis and Mitigation with a Coupled 1D-2D Hydraulic Model: A Case Study in Kochi, Japan." Journal of Disaster Research 10, no. 6 (December 1, 2015): 1099–109. http://dx.doi.org/10.20965/jdr.2015.p1099.
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Coupled one and two-dimensional (1D-2D) hydraulic models play a significant role in analyzing flooding problems to find possible solutions as they can reproduce the actual situations relatively accurately. This paper summarizes approaches to flood inundation analysis and mitigation with coupled 1D-2D hydraulic models of a small mountain watershed in Japan. A detailed flood inundation model including the effects of drainages, pumping, inflow from mountain sub-watersheds and flood gates is developed using coupled 1D-2D hydraulic models. The model is applied to the inundation in Kubokawa, a small town in Kochi Prefecture, Japan on August 9-10, 2014. Simulated and observed maximum water levels along the river and maximum inundations in the flood plain are compared and found to be consistent. Causes of the flooding and percentage of contribution are quantitatively identified, and countermeasures to reduce the effects of flooding are proposed.
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Yu, Juan, Keyao Liu, Anbin Li, Mingfei Yang, Xiaodong Gao, Xining Zhao, and Yaohui Cai. "The Effect of Plug Height and Inflow Rate on Water Flow Characteristics in Furrow Irrigation." Agronomy 12, no. 9 (September 18, 2022): 2225. http://dx.doi.org/10.3390/agronomy12092225.
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Despite its wide application across arid land types, furrow irrigation is often associated with numerous environmental problems related to deep percolation, runoff, and soil erosion. In this study, a straightforward approach was proposed to achieve higher uniformity and reduce erosion. Here, the impacts that a moveable “plug” has on the behavior of irrigation water in the furrow were simulated using FLOW-3D and HYDRUS-2D, where three plug heights and two flow rates were set. The effect of inflow rate and plug height on the water advance, water level, cumulative infiltration in the furrow, and uniformity coefficient was determined. Results indicate that the plug was able to slow water velocity by approximately 60% in the furrow and increase the furrow advance time by 3–4 times; the water level was increased by nearly 10 cm compared with no plug. Moreover, an irrigation uniformity range of 90.18–99.22% was associated with this plugging. The addition of a plug in the furrow irrigation practices for smallholder farmers in developing countries demonstrates great potential in reducing the probability of erosion under large slopes and can effectively improve irrigation uniformity.
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Alhuthali, Ahmed, Adedayo Oyerinde, and Akhil Datta-Gupta. "Optimal Waterflood Management Using Rate Control." SPE Reservoir Evaluation & Engineering 10, no. 05 (October 1, 2007): 539–51. http://dx.doi.org/10.2118/102478-pa.
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Summary Field-scale rate optimization problems often involve highly complex reservoir models, production-and-facilities related constraints, and a large number of unknowns. These factors make optimal reservoir management through rate- and flood-front control difficult without efficient optimization tools. Some aspects of the optimization problem have been studied before mainly using an optimal control theory. However, the applications to date have been rather limited to small problems because of the computation time and the complexities associated with the formulation and solution of adjoint equations. Field-scale rate optimization for maximizing waterflood sweep efficiency under realistic field conditions has remained largely unexplored. This paper proposes a practical and efficient approach for computing optimal injection and production rates, thereby managing the waterflood front to maximize sweep efficiency and delaying the arrival time to minimize water cycling. Our work relies on equalizing the arrival times of the waterflood front at all producers within selected subregions of a waterflood project. The arrival-time optimization has favorable quasilinear properties, and the optimization proceeds smoothly even if our initial conditions are far from the solution. Furthermore, the sensitivity of the arrival time with respect to injection and production rates can be calculated analytically using a single-flow simulation. This makes our approach computationally efficient and suitable for large-scale field applications. The arrival time optimization ensures appropriate rate allocation and flood-front management by delaying the water breakthrough at the producing wells. Several examples are presented to support the robustness and efficiency of the proposed optimization scheme. These include several 2D-synthetic examples for validation purposes and a 3D field application. In addition, we demonstrate the potential of the approach to optimize the flow profile along injection/production segments of horizontal-smart wells. Introduction Waterflooding is by far the most commonly used method to improve oil recovery after primary depletion. In spite of its many favorable characteristics, reservoir heterogeneity—particularly permeability contrast—can have an adverse impact on the performance of waterflooding. The presence of high-permeability streaks can severely reduce the sweep efficiency, leading to an early water arrival at the producers and bypassed oil. Also, an increased cost is associated with water recycling and handling. One approach to counteract the impact of heterogeneity and improve waterflood sweep efficiency is optimal rate allocation to the injectors and producers (Asheim 1988; Sudaryanto and Yortsos 2001; Brouwer et al. 2001; Brouwer and Jansen 2004; Grinestaff 1999; Grinestaff and Caffrey 2000). Through optimal rate control, we can manage the propagation of the flood front, delay water breakthrough at the producers, and also increase the recovery efficiency. Previous efforts to optimize waterflooding relied on optimal control theorem to allocate injection/production rates for fixed well configurations. Asheim (1988) investigated the optimization of waterflood based on maximizing net present value (NPV) for multiple vertical injectors and one producer where the rate profiles change throughout the optimization time. Sudaryanto and Yortsos (2001) used maximizing the displacement efficiency at water breakthrough as the objective for the optimization with two injectors and one producer. The optimal injection policy was found to be bang bang type. That is, the injectors were operated only at their extreme values—either at the maximum allowable injection rate or fully shut. The optimization then involved finding the switch time between the two injectors to ensure simultaneous water arrival at the producing well. Brouwer et al. (2001) studied the static optimization of waterflooding with two horizontal smart wells containing permanent downhole well-control valves and measurement equipment. The static optimization implies that the flow rates of the inflow-control valves (ICVs) along the well segments were kept constant during the waterflooding process until the water arrived at the producer. Various heuristic algorithms were utilized to minimize the impact of high-permeability streaks on the waterflood performance through rate control. The results indicated that the optimal rate allocation can be obtained by reducing the distribution of water-arrival times at various segments along the producer. Subsequently, Brouwer and Jansen (2004) extended their work to dynamic optimization of waterflooding with smart wells using the optimal control theory. The optimization was performed on one horizontal producer and one horizontal injector. Each well is equipped with 45 ICVs. The objective was to maximize the NPV, and it was achieved through changing the rate profile along the well segments throughout the optimization period. Both rate-constrained and bottomhole-pressure-constrained well conditions were studied.
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Fadl-Elmola, Salman A. M., Cristian Moisescu Ciocan, and Ioana Popescu. "Application of Smooth Particle Hydrodynamics to Particular Flow Cases Solved by Saint-Venant Equations." Water 13, no. 12 (June 16, 2021): 1671. http://dx.doi.org/10.3390/w13121671.
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Smoothed particle hydrodynamics (SPH) is a Lagrangian mesh free particle method which has been developed and widely applied to different areas in engineering. Recently, the SPH method has also been used to solve the shallow water equations, resulting in (SPH-SWEs) formulations. With the significant developments made, SPH-SWEs provide an accurate computational tool for solving problems of wave propagation, flood inundation, and wet-dry interfaces. Capabilities of the SPH method to solve Saint-Venant equations have been tested using a SPH-SWE code to simulate different hydraulic test cases. Results were compared to other established and commercial hydraulic modelling packages that use Eulerian approaches. The test cases cover non-uniform steady state profiles, wave propagation, and flood inundation cases. The SPH-SWEs simulations provided results that compared well with other established and commercial hydraulic modeling packages. Nevertheless, SPH-SWEs simulations experienced some drawbacks such as loss of inflow water volume of up to 2%, for 2D flood propagation. Simulations were carried out using an open source solver, named SWE-SPHysics.
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Ngenzebuhoro, Pierre Claver, Alain Dassargues, Tarik Bahaj, Philippe Orban, Ilias Kacimi, and Louis Nahimana. "Groundwater Flow Modeling: A Case Study of the Lower Rusizi Alluvial Plain Aquifer, North-Western Burundi." Water 13, no. 23 (November 30, 2021): 3376. http://dx.doi.org/10.3390/w13233376.
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The study area, in northwestern Burundi, is an alluvial plain consisting of fine clayey sands and coarse sands with mixed lithology. The aquifer of the lower Rusizi plain could be considered as confined under a clay layer. A 2D horizontal groundwater flow model was developed under steady-state conditions using the Modflow software. The study aims to determine the most productive areas of this confined alluvial aquifer and the main aquifer inflow and outflow values together with the recharge and river–aquifer interactions. The groundwater potential is dependent on the spatial distribution of hydraulic conductivity and aquifer thickness values providing the local transmissivity values. The calibrated model made it possible to assess the spatial distribution of the hydraulic conductivity values at the regional scale, which ranged from 6 × 10−6 (contact between alluvial plain and Precambrian basement) to 7.5 × 10−3 m/s (coastal barriers). The results also provided the computed groundwater flow directions, and an estimation of the groundwater levels in areas not yet investigated by drilling. The results of the computed groundwater flow budget allowed us to deduce that recharge and river–aquifer interaction constitute the main inflow while the downwards boundaries (where piezometric heads could be prescribed) are the main zones where outflows occur. The results of this model can be used in the planning of pumping test programs, locating areas with high groundwater potential to plan water supply for different private and public users. This predictive tool will contribute to the resolution of problems related to the use and integrated management of the groundwater resource in this part of Burundi.
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el Abbassi, Mohamed, Domenico Lahaye, and Cornelis Vuik. "The Effect of Variable Air–Fuel Ratio on Thermal NOx Emissions and Numerical Flow Stability in Rotary Kilns Using Non-Premixed Combustion." Processes 9, no. 10 (September 26, 2021): 1723. http://dx.doi.org/10.3390/pr9101723.
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One of the quickest ways to influence both the wall temperature and thermal NOx emissions in rotary kilns is to change the air–fuel ratio (AFR). The normalized counterpart of the AFR, the equivalence ratio, is usually associated with premixed flames and studies of its influence on diffusion flames are inconsistent, depending on the application. In this paper, the influence of the AFR is investigated numerically for rotary kilns by conducting steady-state simulations. We first conduct three-dimensional simulations where we encounter statistically unstable flow at high inflow conditions, which may be caused by vortex stretching. As vortex stretching vanishes in two-dimensional flow, the 2D simulations no longer encounter convergence problems. The impact of this simplification is shown to be acceptable for the thermal behaviour. It is shown that both the wall temperature and thermal NOx emissions peak at the fuel-rich and fuel-lean side of the stoichiometric AFR, respectively. If the AFR continues to increase, the wall temperature decreases significantly and thermal NOx emissions drop dramatically. The NOx validation, however, shows different results and indicates that the simulation model is simplified too much, as the measured NOx formation peaks at significantly fuel-lean conditions.
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Fokker, Peter A., Francesca Verga, and Paul Egberts. "New Semi-Analytic Technique to Determine Horizontal Well PI in Fractured Reservoirs." SPE Reservoir Evaluation & Engineering 8, no. 02 (April 1, 2005): 123–31. http://dx.doi.org/10.2118/84597-pa.
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Summary Simplified analytical relations derived for homogeneous formations are usually applied to the determination of the productivity of horizontal wells, regardless of the presence of heterogeneities in the reservoir. Furthermore, complex well architectures and the wealth of completion options currently available cannot be taken into account properly because the well trajectory can only be schematized as a single horizontal wellbore. However, the use of numerical reservoir simulators to reliably forecast the productivity of horizontal wells draining heterogeneous reservoirs may be time-prohibitive or not feasible because of a lack of sufficiently detailed information, especially during the appraisal phase or the early stages of production. A new semianalytic technique is proposed in this paper to solve the inflow equations in an approximate yet reliable manner. A solution to 3D problems of single-phase flow into a horizontal well, taking into account friction in the wellbore, is provided for both single-layer reservoirs and reservoirs comprising two interfering layers. The method also has been extended to describe the fluid flow when the well intercepts one or more fractures. The presented technique allows very fast calculation of the well productivity in oil and gas reservoirs, offering great flexibility in the placement and architecture of the wells. The method has been applied to two field cases for which the well productivity under pseudosteady-state conditions was measured. One of these is a 200-m-long horizontal well draining an isotropic carbonatic reservoir and intersected by a natural low-conductivity fracture. The other is a similar well, intercepting a natural high-conductivity fault, but the oil-bearing formation is anisotropic. Good correspondence was found between the actual productivity and the predictions obtained by application of the proposed semianalytic technique. Introduction Horizontal wells are common practice in the present hydrocarbon industry, and smart wells (including multilateral completions and wells with selective access of different zones) are becoming increasingly commonplace. The modeling of such wells is, in many cases, not ideal. Areas in which improvements are welcome are well testing, well models in reservoir simulators, and fast models for quick assessment of many field-development options. Further, the handling of natural or hydraulic fractures is often suboptimal. In reservoir simulation, fine grids need to be selected to properly capture the flow behavior close to the well. Moreover, most reservoir simulators are not equipped with extensive well models, which are required when friction in the well becomes important or when two-phase flow develops in the well. This situation has prompted the development of a number of analytical and semianalytical tools, some of which are intended for implementation in a reservoir simulator. Most of the first models, as well as many of the more recent models, assume either constant influx density along the well or infinite well conductivity in a single homogeneous layer. Dikken introduced the effect of well conductivity for a single horizontal well in a homogeneous formation. He started with the assumption that the flow is mainly perpendicular to the wellbore, which allowed him to reduce the reservoir to a 2D flow domain, coupled to a friction model in the well. Others followed this approach, but 3Dmodels were developed as well. A second kind of extension are the multilayer models. Lee and Milliken and Kuchuk and Habashy used a method of reflection and transmission, while Basquet et al. used a "quadrupole" method relating the pressures between the various layers. The multilayer models are also, however, still limited to constant-influx or infinite-conductivity wells.
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Raposo, Paulo. "Geovisualization of complex origin-destination flow maps using Discrete Global Grid Systems." Abstracts of the ICA 1 (July 15, 2019): 1–3. http://dx.doi.org/10.5194/ica-abs-1-308-2019.
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<p><strong>Abstract.</strong> Flow maps, where counts of people or things are shown travelling between origin-destination pairs with paths or arrows, are difficult to draw well, mostly because they rapidly get cluttered as more and more paths are added. Researchers in cartographic and information visualization fields have sought to mitigate these problems in various ways, including cluster detection and edge bundling (Buchin, Speckmann, & Verbeek, 2011; Guo, 2009), force-directed path placement (Holten & van Wijk, 2009; Jenny et al., 2017), use of network topological space instead of planimetric space (Xiao & Chun, 2009), interactive spatial filtering of flows (Vrotsou, Fuchs, Andrienko, & Andrienko, 2017), and by changing the drawing medium to accommodate flows that arc through 3D space (Raposo, 2017; Yang et al., 2019; Zhang, Zhang, Li, & Li, 2018). Other geovisualization techniques recently developed involve and use of matrixes or grids to store and visualize flows; Wood, Dykes, & Slingsby (2010) use spatial tessellation and a set of small multiples of the same tessellation representing origin and destination spaces, respectively, creating a sort of travel heat map when tiles are colored as a choropleth. A comparable approach is taken by Yang et al. (2017) in a system that combines an abstract matrix of flow records with inflow and outflow maps.</p><p>This early-stage project builds on previous matrix-based flow visualization methods while leveraging the power of Discrete Global Grid Systems (DGGS), which present a naturally Earth-oriented hierarchical tessellation upon which a matrix of origins and destinations can be stored and visualized. DGGS (Sahr, White, & Kimerling, 2003; Raposo, Robinson, & Brown, in press) partition the round Earth into nested tiles in a manner similar to quad-trees, and have the desirable properties of covering the whole spherical globe in equal-area (or near equal-area) tiles, and of being hierarchical to an arbitrary number of levels. The hierarchical quality allows flows in a DGGS to be naturally bundled by origin and destination points as a function of grid size; greater or lesser detail (i.e., more or less bundling) in the overall pattern of flows is effected by descending or ascending DGGS levels. As DGGS are becoming increasingly popular for geospatial data computation and collection in movement analysis (Brodsky, 2018), the present work provides a natural bridge to the visualization of such data when it pertains to movement phenomena.</p><p>The present research will develop a suite of flow visualization techniques upon an existing open-source DGGS rendering platform (Raposo, Robinson, & Brown, in press): 1) grid facet coloring in a choropleth scheme to indicate magnitudes of flow into or out of a particular facet; 2) vertical-space cubic spline flow arcs, and 3) tabular representation of the flow data. All three visualization techniques will function across multiple spatial resolutions, corresponding to each of the hierarchical levels of our chosen DGGS, so that users can interact both with each of the three visualizations of the data as well as the spatial granularity to which the data are displayed. All views will be interactive and linked.</p><p>We use Dutton’s (1999) quaternary triangular mesh (QTM), being a DGGS based on recursively subdividing the faces of an octahedron over the globe (Figure 1). Our method begins by finding, at many nested QTM levels, the facets of the QTM with which each origin and destination point intersects; in practice, we use up to 16 levels, as the triangles at that level in the QTM are small enough to address typical individual buildings. Importantly, point-in-polygon intersection is calculated geodetically, and not in 2D projected space, since failing to do this can cause topological errors (Raposo, Robinson, Brown, in press). At each QTM facet and at each level, we build two lists: one of all the other facets at that level that contain an origin point for a flow that arrives at this facet, and another of those that contain a destination point for flows originating in this facet. These lists are stored to each facet as polygon attributes. A flow path curving through vertical space via a cubic spline is also derived for each origin-destination pair and stored as a renderable 3D solid.</p><p>The QTM is then plotted in our software on a virtual globe using NASA’s World Wind application programming interface. As users select any one QTM facet, its attributes are read to find all the other facets either contributing or receiving flows to or from the selected facet; these are then colored according to a choropleth scheme to visualize magnitudes of flow (Figure 2). Coloration is controlled for various descriptive statistics on the flows (e.g., total, mean, maximum, etc.). Linear paths curving up and around the globe (Figure 3) will also be available to be toggled on or off, giving users multiple redundant symbolizations of travel paths.</p>
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Fragalà, Ilaria, Filippo Gazzola, and Gianmarco Sperone. "Solenoidal extensions in domains with obstacles: explicit bounds and applications to Navier–Stokes equations." Calculus of Variations and Partial Differential Equations 59, no. 6 (October 31, 2020). http://dx.doi.org/10.1007/s00526-020-01844-z.
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AbstractWe introduce a new method for constructing solenoidal extensions of fairly general boundary data in (2d or 3d) cubes that contain an obstacle. This method allows us to provide explicit bounds for the Dirichlet norm of the extensions. It runs as follows: by inverting the trace operator, we first determine suitable extensions, not necessarily solenoidal, of the data; then we analyze the Bogovskii problem with the resulting divergence to obtain a solenoidal extension; finally, by solving a variational problem involving the infinity-Laplacian and using ad hoc cutoff functions, we find explicit bounds in terms of the geometric parameters of the obstacle. The natural applications of our results lie in the analysis of inflow–outflow problems, in which an explicit bound on the inflow velocity is needed to estimate the threshold for uniqueness in the stationary Navier–Stokes equations and, in case of symmetry, the stability of the obstacle immersed in the fluid flow.
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Macák, Marek, Róbert Čunderlík, Karol Mikula, and Zuzana Minarechová. "An upwind-based scheme for solving the oblique derivative boundary-value problem related to physical geodesy." Journal of Geodetic Science 5, no. 1 (December 31, 2015). http://dx.doi.org/10.1515/jogs-2015-0018.
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AbstractThe paper presents a novel original upwindbased approach for solving the oblique derivative boundary value problem by the finite volume method. In this approach, the oblique derivative boundary condition is interpreted as a stationary advection equation for the unknown disturbing potential. Its approximation is then performed by using the first order upwind scheme taking into account information from inflow parts of the finite volume boundary only. When the numerical scheme is derived, numerical simulations in 2D and 3D domains are performed and the experimental order of convergence of the proposed algorithm is studied. Moreover a comparison with a solution by the central scheme previously used for this kind of problem is performed. Finally we present numerical experiments dealing with the global and local gravity field modelling.
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Abouelsaad, Omnia, Elena Matta, and Reinhard Hinkelmann. "Evaluating the eutrophication risk of artificial lagoons–case study El Gouna, Egypt." Environmental Monitoring and Assessment 195, no. 1 (December 3, 2022). http://dx.doi.org/10.1007/s10661-022-10767-5.
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Abstract Eutrophication problem in El Gouna shallow artificial coastal lagoons in Egypt was investigated using 2D TELEMAC-EUTRO-WAQTEL module. Eight reactive components were presented, among them dissolved oxygen (DO), phosphorus, nitrogen, and phytoplankton biomass (PHY). The effect of warmer surface water on the eutrophication problem was investigated. Also, the spatial and temporal variability of the eutrophication was analyzed considering different weather conditions: tide wave, different wind speeds and directions. Moreover, effect of pollution from a nearby desalination plant was discussed considering different pollution degrees of brine discharge, different discharge quantities and different weather conditions. Finally, new precautions for better water quality were discussed. The results show that tide wave created fluctuations in DO concentrations, while other water quality components were not highly influenced by tide’s fluctuations. Also, it was found that high water temperatures and low wind speeds highly decreased water quality producing low DO concentrations and high nutrients rates. High water quality was produced beside inflow boundaries when compared to outflow boundaries in case of mean wind. Moreover, the results show that the average water quality was not highly deteriorated by the nearby desalination operation, while the area just beside the desalination inflow showed relatively strong effects. Different weather conditions controlled the brine’s propagation inside the lagoons. Moreover, increasing the width of the inflow boundaries and injecting tracer during tide and mean wind condition are new precautions which may help to preserve the water quality in a future warmer world. This study is one of the first simulations for eutrophication in manmade lagoons.
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Pavlioglou, S. K., M. E. Mastrokalos, C. I. Papadopoulos, and L. Kaiktsis. "Tribological Optimization of Thrust Bearings Operated With Lubricants of Spatially Varying Viscosity." Journal of Engineering for Gas Turbines and Power 137, no. 2 (September 10, 2014). http://dx.doi.org/10.1115/1.4028371.
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In the present work, a computational optimization study of thrust bearings lubricated with spatially varying viscosity lubricants is presented, with the main goal of minimizing friction coefficient. In practice, spatial variation of viscosity could be achieved by utilizing electrorheological or magnetorheological fluids. The bearings are modeled as two-dimensional (2D) channels, consisting of a smooth moving wall (rotor) and a parallel or inclined stationary wall (stator), which can be (i) smooth, (ii) partially textured with rectangular dimples, and (iii) smooth and partially hydrophobic. The bearings are considered to be operated with an ideal lubricant that exhibits different values of viscosity in two distinct regions of the fluid domain: a high viscosity area is considered at the channel inflow, with the viscosity acquiring a reference (low) value farther downstream. The flow field is calculated from the numerical solution of the Navier–Stokes equations for 2D incompressible isothermal flow. The bearing geometry is defined parametrically. Three optimization problems are formulated, corresponding to: (I) a conventional smooth converging slider, (II) a parallel slider with artificial surface texturing at part of the stator surface, and (III) a parallel or converging slider with hydrophobic properties at part of the stator surface. Here, the geometry parameters, as well as the increased viscosity value and the corresponding application regime, form the problem design variables. Bearings are optimized for maximum load capacity and minimum friction coefficient. Optimal solutions are compared against corresponding ones for operation with constant viscosity. It is demonstrated that, by using spatially varying viscosity, a substantial reduction of friction coefficient can be achieved, for all optimization problems considered. This decrease is shown to be a consequence of a sharp pressure rise in the high viscosity regime, resulting in a corresponding rise in load capacity, accompanied by a less pronounced increase in wall shear stress, and thus in total friction force.
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Chen, Huang, Yuanchao Li, Subhra Shankha Koley, and Joseph Katz. "Effects of Axial Casing Grooves on the Structure of Turbulence in the Tip Region of an Axial Turbomachine Rotor." Journal of Turbomachinery 143, no. 9 (May 11, 2021). http://dx.doi.org/10.1115/1.4050605.
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Abstract Challenges in turbulence modeling in the tip region of turbomachines include anisotropy, inhomogeneity, and non-equilibrium conditions, resulting in poor correlations between Reynolds stresses and the corresponding mean strain-rate components. The geometric complexity introduced by casing grooves exacerbates this problem. Taking advantage of a large database collected in the refractive index-matched liquid facility at Johns Hopkins University (JHU), this paper examines the effect of axial casing grooves on the distributions of turbulent kinetic energy (TKE), Reynolds stresses, anisotropy tensor, and TKE production rate in the tip region of an axial turbomachine. The comparisons are performed at flowrates corresponding to prestall and best efficiency points of the untreated machine. Common features include high TKE near the tip leakage vortex center and in the shear layer connecting it to the blade suction side tip corner. The turbulence is highly anisotropic and inhomogeneous, with the anisotropy tensor shifting from one-dimensional (1D) to 2D and 3D structures over small distances. With the grooves, the flow structure, hence the distribution of Reynolds stresses, becomes more complex. Additional sites with elevated turbulence include the corner vortex that develops at the entrance to the grooves, and in the flow jetting out of the grooves into the passage. Consistent with trends of the production rates of normal Reynolds stress components, the grooves increase the axial but reduce the radial velocity fluctuations as the inflow and outflow from the groove interact with the passage flow. These findings might assist the development of Reynolds stress models suitable for tip flows.
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Hazlett, Randy D., Umer Farooq, and Desarazu K. Babu. "A Complement to Decline Curve Analysis." SPE Journal, April 1, 2021, 1–11. http://dx.doi.org/10.2118/205390-pa.
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Summary Decline curve analysis (DCA) has been the mainstay in unconventional reservoir evaluation. Because of the extremely low matrix permeability, each well is evaluated economically for ultimate recovery as if it were its own reservoir. Classification and normalization of well potential is difficult because of ever-changing stimulation total contact area and a hyperbolic curve fit parameter that is disconnected from any traditional reservoir characterization descriptor. A new discrete fracture model approach allows direct modeling of inflow performance in terms of fracture geometry, drainage volume shape, and matrix permeability. Running such a model with variable geometrical input to match the data in lieu of standard regression techniques allows extraction of a meaningful parameter set for reservoir characterization, an expected outcome from all conventional well testing. Because the entirety of unconventional well operation is in transient mode, the discrete fractured well solution to the diffusivity equation is used to model temporal well performance. The analytical solution to the diffusivity equation for a line source or a 2D fracture operating under constrained bottomhole pressure consists of a sum of terms, each with exponential damping with time. Each of these terms has a relationship with the constant rate, semisteady-state solution for inflow, although the well is not operated with constant rate, nor will this flow regime ever be realized. The new model is compared with known literature models, and sensitivity analyses are presented for variable geometry to illustrate the depiction of different time regimes naturally falling out of the unified diffusivity equation solution for discrete fractures. We demonstrate that apparent hyperbolic character transitioning to exponential decline can be modeled directly with this new methodology without the need to define any crossover point. The mathematical solution to the physical problem captures the rate transient functionality and any and all transitions. Each exponential term in the model is related to the various possible interferences that may develop, each occurring at a different time, thus yielding geometrical information about the drainage pattern or development of fracture interference within the context of ultralow matrix permeability. Previous results analyzed by traditional DCA can be reinterpreted with this model to yield an alternate set of descriptors. The approach can be used to characterize the efficacy of evolving stimulation practices in terms of geometry within the same field and thus contribute to the current type curve analyses subject to binning. It enables the possibility of intermixing of vertical and horizontal well performance information as simply gathering systems of different geometry operating in the same reservoir. The new method will assist in reservoir characterization and evaluation of evolving stimulation technologies in the same field and allow classification of new type curves.
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Gbenro, S. O., and J. N. Nchejane. "Numerical Simulation of the Dispersion of Pollutant in a Canal." Asian Research Journal of Mathematics, April 16, 2022, 25–40. http://dx.doi.org/10.9734/arjom/2022/v18i430371.
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This work proposes a numerical approach to model 2D pollutant dispersion in a canal using the famous advection-reaction diffusion equations. The advection-dispersion equation model describes transport and diffusion problems as seen in mixing conservative, nonbuoyant pollutants deposited into a stream or canal. The canal consisted of a narrow channel that allows water inflow through an entry opening and outflow through an exit opening. We obtain stability conditions for finite difference schemes and show the existence and uniqueness of solutions for the finite element method. The simulations show that the concentration of pollutants in the canal is controlled by the divergence term and increases in the direction of fluid flow.
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Liu, Yang, Kenji Takizawa, Tayfun E. Tezduyar, Takashi Kuraishi, and Yufei Zhang. "Carrier-Domain Method for high-resolution computation of time-periodic long-wake flows." Computational Mechanics, October 6, 2022. http://dx.doi.org/10.1007/s00466-022-02230-6.
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AbstractWe are introducing the Carrier-Domain Method (CDM) for high-resolution computation of time-periodic long-wake flows, with cost-effectives that makes the computations practical. The CDM is closely related to the Multidomain Method, which was introduced 24 years ago, originally intended also for cost-effective computation of long-wake flows and later extended in scope to cover additional classes of flow problems. In the CDM, the computational domain moves in the free-stream direction, with a velocity that preserves the outflow nature of the downstream computational boundary. As the computational domain is moving, the velocity at the inflow plane is extracted from the velocity computed earlier when the plane’s current position was covered by the moving domain. The inflow data needed at an instant is extracted from one or more instants going back in time as many periods. Computing the long-wake flow with a high-resolution moving mesh that has a reasonable length would certainly be far more cost-effective than computing it with a fixed mesh that covers the entire length of the wake. We are also introducing a CDM version where the computational domain moves in a discrete fashion rather than a continuous fashion. To demonstrate how the CDM works, we compute, with the version where the computational domain moves in a continuous fashion, the 2D flow past a circular cylinder at Reynolds number 100. At this Reynolds number, the flow has an easily discernible vortex shedding frequency and widely published lift and drag coefficients and Strouhal number. The wake flow is computed up to 350 diameters downstream of the cylinder, far enough to see the secondary vortex street. The computations are performed with the Space–Time Variational Multiscale method and isogeometric discretization; the basis functions are quadratic NURBS in space and linear in time. The results show the power of the CDM in high-resolution computation of time-periodic long-wake flows.
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Li, Tingyu, and Gregory B. Pasternack. "Water Transfer Redistributes Sediment in Small Mountain Reservoirs." Water Resources Management, August 15, 2022. http://dx.doi.org/10.1007/s11269-022-03290-2.
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AbstractReservoir sedimentation management has become an important topic for large dams in the United States due to their historical design, current age, and increased environmental regulation. Less attention has been paid to small dams (hydraulic size < 0.01) in remote mountains with urgent sedimentation problems. In drier climates, such reservoirs may be frequently drained and trans-catchment flows routed over their sediment deposits heading from one mountain tunnel to another. This study asked an unexplored scientific question focusing on this special setting: how do different amounts of water transfers interact with different reservoir stages to affect sediment erosion and its redistribution in the backwater zone? Mindful timing and magnitude adjustment of water transfer, involving water diverted across watersheds by tunnels, through a reservoir were hypothesized to strategically redistribute sediment erosion for sites with water transfer/diversion facilities in the main channel. For a study site in the north-central Sierra Mountains of California, 2D hydrodynamic modeling revealed that sediment erosion within the backwater zone increased by > 100% when water transfer was maximized, involving a flow 12 times higher than mean annual discharge. With reservoir stage drawdown, the increment of sediment erosion was further increased by > 50% compared with water-transfer-only scenarios. The natural upstream inflow with daily flow occurrence of 5–25% was the optimal water transfer to avoid disturbing sediment. These results indicated that water transfer and stage drawdown optimization is a promising strategy to promote or abate redistribution of deposited sediment through a smaller reservoir.