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Статті в журналах з теми "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.
Повний текст джерела
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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.
Повний текст джерелаАнотація:
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.
Повний текст джерелаАнотація:
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.
Повний текст джерелаАнотація:
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.
Повний текст джерелаАнотація:
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.
Повний текст джерелаАнотація:
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.
Повний текст джерелаАнотація:
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.
Повний текст джерелаАнотація:
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.
Повний текст джерелаАнотація:
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.
Дисертації з теми "2D inflow problem"
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Naik, Saurabh. "Analytical modelling of the water block phenomenon in oil and gas wells." Thesis, 2019. http://hdl.handle.net/2440/123509.
Повний текст джерелаАнотація:
In oil or gas production wells, water can become trapped by capillary forces in the reservoir rock near to the wellbore or hydraulic fracture face. The trapped water dramatically reduces the production rate of oil or gas. The general term for wells suffering from productivity loss due to capillary trapped water is “water block”. The severity of the water block is the result of the combined effects of wettability, capillary forces, viscous forces, fluid compressibility, hydraulic fracture length and various other reservoir and well properties. A numerical model can be used to evaluate all the effects for particular scenarios. However, for most oil or gas reservoirs, there is great uncertainty in many of the reservoir parameters. Evaluating enough scenarios numerically to account for all the uncertainty can be extremely time-consuming. Analysing the sensitivity to uncertain parameters is substantially faster and better served by analytical models. Historically, the impact of the end effects in production wells have been neglected in analytical models as the target reservoirs have generally had high permeability. Now, the development of petroleum fields involves targeting much lower permeability reservoirs. These reservoirs can exhibit high capillary pressures. Despite the significant capillary pressure effects, analytical models have yet to be developed for gas or oil well performance accounting for capillary end effects. The goal of this thesis is to develop analytical models to include the effects of capillary forces near to the wellbore or the hydraulic fracture and to analyse the impact of fluid compressibility, wettability, capillary forces, viscous forces, porous media network characteristics and hydraulic fracture half-length. This thesis includes five journal papers, four of which have been published; the last one finished with intention to submit later this year. The thesis develops new analytical models to calculate the productivity index of gas wells. The new models account for viscous forces, capillary forces, inertial forces, wettability, compressibility, non-uniform flow into hydraulic fractures and capillary end effects near to the wellbore or hydraulic fracture. The analytical models are validated through matching with experimental data or numerical simulators. The forms of the capillary pressure and relative permeability curves are extremely important properties of the reservoir which impact the magnitude of the capillary end effect. The shape of the curves is significantly impacted by the characteristics of the pore network. A sophisticated mixed percolation model coupled with effective medium theory is developed in the thesis. The novelty of the new percolation model is that it applies mixed bond-site percolation for the first time to the water-hydrocarbon drainage problem, while only bond or site percolation was applied in previous models. This thesis integrates the complex interaction between the viscous, capillary and inertial forces, water cut, hydraulic fracture length and the topology of the pore network. The study quantifies the impact of each of the aforementioned characteristics of two phase flow on the productivity of gas wells. The results of this thesis are critical in screening for economic well candidates for intervention.Thesis (Ph.D.) -- University of Adelaide, Australian School of Petroleum, 2020
Частини книг з теми "2D inflow problem"
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"Transthoracic examination." In Echocardiography, edited by Paul Leeson, Christiana Monteiro, Daniel Augustine, Harald Becher, Paul Leeson, Christiana Monteiro, Daniel Augustine, and Harald Becher, 71–126. Oxford University Press, 2020. http://dx.doi.org/10.1093/med/9780198804161.003.0002.
Повний текст джерелаАнотація:
This chapter covers all aspects of transthoracic examination, including patient information, preparing machine and probe, probe handling and image quality, 2D image acquisition, 3D image acquisition, multiplane image acquisition, data acquisition, parasternal long axis view, parasternal right ventricle inflow view, parasternal right ventricle outflow view, parasternal short axis (aortic) view, parasternal short axis (mitral) view, parasternal short axis (ventricle) views, parasternal 3D views, apical 4-chamber view, apical 5-chamber view, apical 2-chamber view, apical 3-chamber view, apical 3D views, subcostal views, inferior vena cava view, abdominal aorta view, suprasternal view, right parasternal view, and standard examination.
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Li, Guoyi, Jiahong Liu, and Weiwei Shao. "Operation Dispatching Feature Analysis Based on TELEMAC-2D." In Frontiers in Artificial Intelligence and Applications. IOS Press, 2022. http://dx.doi.org/10.3233/faia220407.
Повний текст джерелаАнотація:
China is in the stage of rapid urbanization, resulting in more and more serious urban waterlogging problems. Based on the TELEMAC-2D hydrodynamic model, this paper conducted mathematical modeling of Swan Lake flood storage and detention area in Dongying City, and simulated the inflow and inundation process of Swan Lake flood storage and detention area under three rainfall scenarios of typhoon “Rumbia”, “Lekima” and 50-year return period. The simulation results show that when three water intakes are opened at the same time (Plan A), the total amount of water inflow under typhoon “Rumbia”, “Lekima” and 50-year return period rainfall scenario is not exceeding the storage capacity, respectively. When only one water intake was opened (Plan B), the total incoming flow is not exceeding the storage capacity of Swan Lake flood storage and detention area. In all setting plans and rainfall scenarios, the maximum water level before sluice is 3.42m. By operating and dispatching the intake sluice in the flood storage and detention area of Swan Lake, the water level of Guangli River can be effectively controlled below 3.5m, ensure that the urban drainage system is not supported by the top and maintain the normal drainage function. In all setting plans and rainfall scenarios, the maximum flow of 1#, 2# and 3# water intake is not exceeding the design flow of corresponding water intake, respectively. The simulation results can provide a scientific basis for the operation regulation and flood control operation of Swan Lake flood storage and detention area.
Тези доповідей конференцій з теми "2D inflow problem"
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Johannessen, Hestetraeet. "Numerical Study of Vortex Shedding behind a NACA 0009 Hydrofoil." In SNAME Maritime Convention. SNAME, 2021. http://dx.doi.org/10.5957/smc-2021-053.
Повний текст джерелаАнотація:
This paper addresses the propeller singing mitigation strategy of implementing an anti-singing edge so that the vortex shedding mechanism causing the excitation at the trailing edge of the propeller blade can be reduced. A Reynolds-Averaged Navier Stokes model with a k-ε turbulence formulation in 2D-flow was used to investigate the problem numerically. Simulations on a NACA 0009 hydrofoil with varying inflow velocity, angle of attack, and bevel angle were done. The content in this paper is a summary of the work done by the author during his MSc Individual Project at University College London (Johannessen, MSc thesis, 2020).
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Chuprakov, Dimitry, Ludmila Belyakova, Ivan Glaznev, and Aleksandra Peshcherenko. "High-Resolution and Multimaterial Fracture Productivity Calculator for the Successful Design of Channel Fracturing Jobs." In SPE Russian Petroleum Technology Conference. SPE, 2021. http://dx.doi.org/10.2118/206654-ms.
Повний текст джерелаАнотація:
Abstract We developed a high-resolution fracture productivity calculator to enable fast and accurate evaluation of hydraulic fractures modeled using a fine-scale 2D simulation of material placement. Using an example of channel fracturing treatments, we show how the productivity index, effective fracture conductivity, and skin factor are sensitive to variations in pumping schedule design and pulsing strategy. We perform fracturing simulations using an advanced high-resolution multiphysics model that includes coupled 2D hydrodynamics with geomechanics (pseudo-3D, or P3D, model), 2D transport of materials with tracking temperature exposure history, in-situ kinetics, and a hindered settling model, which includes the effect of fibers. For all simulated fracturing treatments, we accurately solve a problem of 3D planar fracture closure on heterogenous spatial distribution of solids, estimate 2D profiles of fracture width and stresses applied to proppants, and, as a result, obtain the complex and heterogenous shape of fracture conductivity with highly conductive cells owing to the presence of channels. Then, we also evaluate reservoir fluid inflows from a reservoir to fracture walls and further along a fracture to limited-size wellbore perforations. Solution of a productivity problem at the finest scale allows us to accurately evaluate key productivity characteristics: productivity index, dimensional and dimensionless effective conductivity, skin factor, and folds of increase, as well as the total production rate at any day and for any pressure drawdown in a well during well production life. We develop a workflow to understand how productivity of a fracture depends on variation of the pumping schedule and facilitate taking appropriate decisions about the best job design. The presented workflow gives insight into how new computationally efficient methods can enable fast, convenient, and accurate evaluation of the material placement design for maximum production with cost-saving channel fracturing technology.
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Vera, M., H. P. Hodson, and R. Vazquez. "The Effects of a Trip Wire and Unsteadiness on a High Speed Highly Loaded Low-Pressure Turbine Blade." In ASME Turbo Expo 2004: Power for Land, Sea, and Air. ASMEDC, 2004. http://dx.doi.org/10.1115/gt2004-53822.
Повний текст джерелаАнотація:
This paper presents the effect of a single spanwise 2D wire upon the downstream position of boundary layer transition under steady and unsteady inflow conditions. The study is carried out on a high turning, high-speed, low pressure turbine (LPT) profile designed to take account of the unsteady flow conditions. The experiments were carried out in a transonic cascade wind tunnel to which a rotating bar system had been added. The range of Reynolds and Mach numbers studied includes realistic LPT engine conditions and extends up to the transonic regime. Losses are measured to quantify the influence of the roughness with and without wake passing. Time resolved measurements such as hot wire boundary layer surveys and surface unsteady pressure are used to explain the state of the boundary layer. The results suggest that the effect of roughness on boundary layer transition is a stability governed phenomena, even at high Mach numbers. The combination of the effect of the roughness elements with the inviscid Kelvin-Helmholtz instability responsible for the rolling up of the separated shear layer (Stieger [1]) is also examined. Wake traverses using pneumatic probes downstream of the cascade reveal that the use of roughness elements reduces the profile losses up to exit Mach numbers of 0.8. This occurs with both steady and unsteady inflow conditions.
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Giebmanns, A., R. Schnell, W. Steinert, A. Hergt, E. Nicke, and C. Werner-Spatz. "Analyzing and Optimizing Geometrically Degraded Transonic Fan Blades by Means of 2D and 3D Simulations and Cascade Measurements." In ASME Turbo Expo 2012: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/gt2012-69064.
Повний текст джерелаАнотація:
The present study deals with the influence of geometrically degraded transonic engine fan blades on the fan’s aerodynamic behavior. The study is composed of three phases; the first consists of 3D simulations to point out changes in the performance parameters caused by blade degradations. In the second phase, 2D optimizations are carried out to determine the potential of redesigning the blade and in the third phase, measurements on a transonic cascade are used to experimentally verify the numeric results. During engine operation as well as maintenance processes, geometric variations of the fan blades, and especially of the blades’ leading edges, are observed. They mainly originate from the ambient conditions under which the engine is operated. Though the deformations of the blade differ widely, several typical degradation types can be identified. In advance of the study, these degradation types have been systematized and simplified models representing different degrees of degradation have been built. In the first phase, the models are aerodynamically analyzed by means of 3D simulations. A high influence on the performance parameters is found for a fan blade exposed to long-term erosion. The model’s characteristics are a blunt leading edge and a reduced chord length. In contrast, the performance parameters of a model representing a re-contoured blade (reduced chord length but reshaped leading edge) are shown to be similar to those of a new fan blade. This leads to the conclusion that an eroded blade may offer almost the initial performance parameters as long as the leading edge is well reshaped. Since the model of the long-term eroded blade shows great changes in the fan’s performance and the best optimization potential, this has been chosen for the further analysis in the following phases. In the second phase, 2D optimizations are applied to three airfoil sections at different heights of the blade. The parameterization used is limited to a small area of the leading edge; the shape of the rest of the blade is kept constant. The optimizations lead to loss reduction and demonstrate the potential of the optimization process. The third phase is carried out in the Transonic Cascade Wind Tunnel of the Institute of Propulsion Technology in Cologne. As the transonic part of the fan blade is the most sensitive to geometric changes, a transonic airfoil with long-term erosion has been chosen. During the tests, the following measurement techniques are applied: Static pressure probes to determine the Mach number distribution, a 3-hole probe to detect exit angle and loss distribution, Schlieren photographs and PIV-measurements to locate the shock system, the L2F method to measure the cascade inflow angle and to resolve the boundary layer distribution and Liquid crystal measurements to observe transition activities. The full analysis of the measurements with PIV, L2F and Liquid Crystals are still in progress, but the evaluation of the loss polar and the Schlieren photographs show increased losses for the degraded blade and a good match with the numeric results.
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Bacci, T., R. Becchi, A. Picchi, and B. Facchini. "Adiabatic Effectiveness on High Pressure Turbine Nozzle Guide Vanes Under Realistic Swirling Conditions." In ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/gt2018-76637.
Повний текст джерелаАнотація:
In modern lean burn aero-engine combustors, highly swirling flow structures are adopted to control the fuel-air mixing and to provide the correct flame stabilization mechanisms. Aggressive swirl fields and high turbulence intensities are hence expected in the combustor-turbine interface. Moreover, to maximize the engine cycle efficiency, an accurate design of the high pressure nozzle cooling system must be pursued: in a film cooled nozzle the air taken from last compressor stages is ejected through discrete holes drilled on vane surfaces to provide a cold layer between hot gases and turbine components. In this context, the interactions between the swirling combustor outflow and the vane film cooling flows play a major role in the definition of a well performing cooling scheme, demanding for experimental campaigns at representative flow conditions. An annular three-sector combustor simulator with fully cooled high pressure vanes has been designed and installed at THT Lab of University of Florence. The test rig is equipped with three axial swirlers, effusion cooled liners and six film cooled high pressure vanes passages, for a vortex-to-vane count ratio of 1:2. The relative clocking position between swirlers and vanes has been chosen in order to have the leading edge of the central airfoil aligned with the central swirler. In this experimental work, adiabatic film effectiveness measurements have been carried out in the central sector vanes, in order to characterize the film-cooling performance under swirling inflow conditions. The Pressure Sensitive Paint technique, based on heat and mass transfer analogy, has been exploited to catch highly detailed 2D distributions. Carbon dioxide has been used as coolant in order to reach a coolant-to-mainstream density ratio of 1.5. Turbulence and five hole probe measurements at inlet/outlet of the cascade have been carried out as well, in order to highlight the characteristics of the flow field passing through the cascade and to provide precise boundary conditions. Results have shown a relevant effect of the swirling mainflow on the film cooling behaviour. Differences have been found between the central airfoil and the adjacent ones, both in terms of leading edge stagnation point position and of pressure and suction side film coverage characteristics.