WorldWideScience

Sample records for airfoil sand erosion

  1. Sand transport, erosion and granular electrification

    DEFF Research Database (Denmark)

    Merrison, J.P.

    2012-01-01

    The transport of granular materials by wind has a major impact on our environment through sand/soil erosion and the generation and transport of atmospheric dust aerosols. Terrestrially the transport of dust involves billions of tons of material every year, influencing the global climate...... can affect grain transport through the generation of intense electric fields and processes of electrostatic assembly. Importantly the transport of sand is characterized by saltation, which is known to be an active process for erosion and therefore a source for dust and sand formation. Using novel...... erosion simulation techniques the link between grain transport rates and erosion rates has been quantified. Furthermore this can be linked to production rates for dust and has been associated with chemical and mineral alteration through a process of mechanical activation of fractured surfaces. This work...

  2. Materials for Advanced Turbine Engines (MATE). Project 4: Erosion resistant compressor airfoil coating

    Science.gov (United States)

    Rashid, J. M.; Freling, M.; Friedrich, L. A.

    1987-01-01

    The ability of coatings to provide at least a 2X improvement in particulate erosion resistance for steel, nickel and titanium compressor airfoils was identified and demonstrated. Coating materials evaluated included plasma sprayed cobalt tungsten carbide, nickel carbide and diffusion applied chromium plus boron. Several processing parameters for plasma spray processing and diffusion coating were evaluated to identify coating systems having the most potential for providing airfoil erosion resistance. Based on laboratory results and analytical evaluations, selected coating systems were applied to gas turbine blades and evaluated for surface finish, burner rig erosion resistance and effect on high cycle fatigue strength. Based on these tests, the following coatings were recommended for engine testing: Gator-Gard plasma spray 88WC-12Co on titanium alloy airfoils, plasma spray 83WC-17Co on steel and nickel alloy airfoils, and Cr+B on nickel alloy airfoils.

  3. An Iterative Method for Estimating Airfoil Deformation due to Solid Particle Erosion

    Directory of Open Access Journals (Sweden)

    Valeriu DRAGAN

    2014-04-01

    Full Text Available Helicopter blades are currently constructed with composite materials enveloping honeycomb cores with only the leading and trailing edges made of metal alloys. In some cases, the erosive wear of the bound between the composite skin and metallic leading edge leads to full blade failure. It is therefore the goal of this paper to provide a method for simulating the way an airfoil is deformed through the erosion process. The method involves computational fluid dynamics simulations, scripts for automatic meshing and spreadsheet calculators for estimating the erosion and, ultimately, the airfoil deformation. Further work could include more complex meshing scripts allowing the use of similar methods for turbo-machineries.

  4. The Development of Erosion and Impact Resistant Turbine Airfoil Thermal Barrier Coatings

    Science.gov (United States)

    Zhu, Dongming; Miller, Robert A.

    2007-01-01

    Thermal barrier coatings are used in gas turbine engines to protect engine hot-section components in the harsh combustion environments and extend component lifetimes. For thermal barrier coatings designed for turbine airfoil applications, further improved erosion and impact resistance are crucial for engine performance and durability. Advanced erosion resistant thermal barrier coatings are being developed, with a current emphasis on the toughness improvements using a combined rare earth- and transition metal-oxide doping approach. The performance of the doped thermal barrier coatings has been evaluated in burner rig and laser heat-flux rig simulated engine erosion and thermal gradient environments. The results have shown that the coating composition optimizations can effectively improve the erosion and impact resistance of the coating systems, while maintaining low thermal conductivity and cyclic durability. The erosion and impact damage mechanisms of the thermal barrier coatings will also be discussed.

  5. Estimating Erosion in Oil and Gas Pipe Line Due to Sand Presence

    OpenAIRE

    Abdulla, Akar

    2011-01-01

    Transporting solid particles in oil and gas flow cause erosion damage to the pipeline and fittings. The aim of this thesis is to study the effect of impact velocity on the erosion damage in 90 degree long elbow by using two different erosion models namely, Oka model and E/CRC model. Those correlation applied at air-borne sand eroding, methane-borne sand eroding, mixed gas-borne sand eroding, and multiphase (gas- oil) borne sand eroding Inconel 625. The commercial computational fluid dynamics ...

  6. A Multiphase First Order Model for Non-Equilibrium Sand Erosion, Transport and Sedimentation

    CERN Document Server

    Preziosi, Luigi; Bruno, Luca

    2015-01-01

    Three phenomena are involved in sand movement: erosion, wind transport, and sedimentation. This paper presents a comprehensive easy-to-use multiphase model that include all three aspects with a particular attention to situations in which erosion due to wind shear and sedimentation due to gravity are not in equilibrium. The interest is related to the fact that these are the situations leading to a change of profile of the sand bed.

  7. Numerical Simulation of Sand Erosion Phenomena in Rotor/Stator Interaction of Compressor

    Institute of Scientific and Technical Information of China (English)

    Masaya Suzuki; Kazuaki Inaba; Makoto Yamamoto

    2008-01-01

    Sand erosion is a phenomenon where solid particles impinging to a wall cause serious mechanical damages to the wall surface. This phenomenon is a typical gas-particle two-phase turbulent flow and a multi-physics problem where the flow field, particle trajectory and wall deformation interact with each other. On the other hand, aircraft engines operating in a particulate environment are subjected to the performance and lifetime deterioration due to sand erosion. Especially, the compressor of the aircraft engines is severely damaged. The flow fields of the compressor have strongly three dimensional and unsteady natures. In order to estimate the deterioration due to sand erosion, the sand erosion simulation for a compressor is required under the consideration of the rotor-stator interaction. In the present study, we apply our three dimensional sand erosion prediction code to a single stage axial flow compressor. We numerically investigate the change of the flow field, the particle trajectories, and the eroded wall shape in the compressor, to clarify the effects of sand erosion in the compressor.

  8. Abrasive Erosion Study on S45C Carbon Steel Using Sand Blasting Technique

    Science.gov (United States)

    Naz, Muhammad Yasin; Ismail, Noor Ilyana; Sulaiman, Shaharin Anwar; Shukrullah, Shazia

    2016-05-01

    Hydrocarbon fluids recovered from the reservoir are inevitably polluted with sand particles. Sanding is a source of several flow assurance problems in oil and gas industry. This study was aimed at investigating the effect of sand size and impact angle on the mild steel erosion by using a laboratory built sand blasting technique. S45C mild steel coupons were eroded with 45 μm and 150μm sand particles for fixed exposure time of 1 h. Although in-depth analysis revealed an increase in surface erosion with the particle size, the fine sand also notably damaged the metal surface. Topographic scanning electron microscopy (SEM) and universal scanning electron microscopy (USPM) micrographs of the steel coupons showed significantly large difference between the peak and bottom of the eroded samples as compared to the blank coupon. The erosion rates calculated for 45 and 150 μm sand particles were found in the range of 6.47mm/year to 6.84 mm/year and 8.31 mm/year to 8.79 mm/year, respectively. Additionally, a good agreement was seen among the erosion rates calculated using USPM and weight loss methods. The erosion rates calculated for coarse sand at 45∘ and 90∘ were found in the range of 4.58 mm/year to 4.72 mm/year and 8.31 mm/year to 8.79 mm/year, respectively. A large difference between the angle dependent erosion rates revealed a strong influence of the impact angle on erosion of the flow-lines.

  9. Modelling sand production and erosion growth under combined axial and radial flows

    Energy Technology Data Exchange (ETDEWEB)

    Wan, R.G.; Wang, J. [Calgary Univ., AB (Canada)

    2002-07-01

    A newly developed coupled particle erosion-fluid transport stress model has been used to examine the phenomenon of sand production in axial and radial flow conditions. The modeling involved a close look at sand production and wormhole growth in a sand pack while heavy oil was being drawn from it through a small opening. Experimental data and numerical results were in close agreement. The calculated porosity field and its temporal evolution during wormhole propagation matched very well with CT scan images of the sand pack. The study also involved a hollow cylinder test to model sand production in order to see how sand is produced under combined axial and radial flow of light oil in a sandstone sample. The numerical model was used to examine sand flux and the evolution of porosity, as well as the propagation of erosion around the inner wall of the cylinder. It was concluded that erosion intensity is not uniform around the walls of the inner hole. Under axial and radial flow conditions, sand flux does not occur uniformly around the opening. The highest sand flux occurs at the corner point of the inner hole bottom. 15 refs., 1 tab., 10 figs.

  10. Simulating cold production by a coupled reservoir-geomechanics model with sand erosion

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Y.; Xue, S. [Petro-Geotech Inc., Calgary, AB (Canada)

    2002-06-01

    This paper presents a newly developed fully coupled reservoir-geomechanics model with sand erosion. Sand production occurs during aggressive production induced by the impact of viscous fluid flow and the in situ stress concentration near a wellbore, as well as by perforation tips in poorly consolidated formations. This compromises oil production, increases well completion costs, and reduces the life cycles of equipment down hole and on the surface. The proposed model can be used for sand production studies in conventional oil/gas reservoirs such as the North Sea as well as in heavy oil reservoirs such as in northwestern Canada. Instead of generating a high permeability network in reservoirs, the enhanced oil production is determined by the increase in the effective wellbore radius. This paper presents the general model. A detailed study on the capillary pressure and the impact of multiphase flow on sanding and erosion will be conducted at a later date. It appears that 2 phase flow can be important to elastoplasticity if no significant sand erosion has occurred. It was determined that high porosity is induced by erosion and capillary pressure. Two phase flow can be important when the built-up drag force carries sand-fluid slurry into the well. It is concluded that viscosity and flow velocity can help estimate the slurry transport, sand rate and enhanced oil production. 22 refs., 3 tabs., 11 figs.

  11. Investigating the Effect of Lignosulfonate on Erosion Rate of the Embankments Constructed with Clayey Sand

    Directory of Open Access Journals (Sweden)

    Hamid Reza Koohpeyma

    2013-01-01

    Full Text Available Internal erosion is known as the most important cause of dam failure after overtopping. It is important to improve the erosion resistance of the erodible soil by selecting an effective technique along with the reasonable costs. To prevent internal erosion of embankment dams the use of chemical stabilizers that reduce the soil erodibility potential is highly recommended. In the present study, a lignin-based chemical, known as lignosulfonate, is used to improve the erodibility of clayey sand specimen. The clayey sand was tested in various hydraulic heads in terms of internal erosion in its natural state as well as when it is mixed with the different percentages of lignosulfonate. The results show that erodibility of collected clayey sand is very high and is dramatically reduced by adding lignosulfonate. Adding 3% of lignosulfonate to clayey sand can reduce the coefficient of soil erosion from 0.01020 to 0.000017. It is also found that the qualitative erodibility of stabilized soil with 3% lignosulfonate is altered from the group of extremely rapid to the group of moderately slow.

  12. AN ALTERNATE METHOD TO PREVENT SAND ABRASIVE EROSION IN PIPELINES FOR TRANSPORTING HIGH-SPEED NATURAL GAS

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    This paper presents an alternate method to re-move the sand carried by natural gas in the upstream pipelinestherefore preventing sand abrasive erosion in pipelines used intransporting high-speed natural gas. Conventionally, most ex-perts pay much attention to improving the anti-erosion charac-teristics of the pipeline materials to solve the problem of seri-ous abrasive erosion, but without significant success. Basedon the theory of multiphase flow and analysis of the character-istics of sandy jets, a new equipment named "Sand Catcher" isintroduced in this article. Experimental results show that theSand Catcher effectively removes most of the sand in the natu-ral gas and significantly reduces the abrasive erosion of thepipelines. The Sand Catcher can be widely applied in practicein the near future.

  13. An experiment system for testing synergetic erosion caused by sand abrasion and cavitation

    International Nuclear Information System (INIS)

    An advanced comprehensive test system, designed for testing synergetic erosion due to cavitation and sand abrasion in hydraulic machinery, is presented in this paper. This system includes an integrated test rig, control platform, and state-of-the-art measurement etc. For the integrated test system, there are three test modes, Venturi-section water tunnel, rotating disc and rotating disc with jet nozzle. The maximum velocity is 45 m/s for Venturi-section water tunnel test mode, and 85 m/s for rotating disc test mode. The pressure range for those two test modes can be regulated within -0.09 MPa∼0.6 MPa. The highest flow relative velocity is 120 m/s for rotating disc with jet nozzle test mode. All key parameters measured from the test rig, such as flow discharge, pressure, sand concentration, temperature etc, can be displayed online and processed in the control platform. This new test system provides researchers with the possibility to measure cavitation erosion, sand abrasion and the synergetic damage in hydraulic machinery. Further, flow visualization analysis, weight loss measurements and erosion outline measurements are available using the system

  14. Experimental Evaluation of Erosion of Gunmetal under Asymmetrical Shaped Sand Particle

    Directory of Open Access Journals (Sweden)

    Mohammad Asaduzzaman Chowdhury

    2015-01-01

    Full Text Available The erosion characteristics of gunmetal have been evaluated practically at different operating conditions. Asymmetrical silica sand (SiO2 is taken into account as erodent within range of 300–600 μm. The impact velocity within 30–50 m/sec, impact angle 15–900, and stand off distance 15–25 mm are inspected as other relevant operating test conditions. The maximum level of erosion is obtained at impact angle 15° which indicates the ductile manner of the tested gunmetal. The higher the impact velocity, the higher the erosion rate as almost linear fashion is observed. Mass loss of gunmetal reduces with the increase of stand-off distance. A dimensional analysis, erosion efficiency (η, and relationship between friction and erosion indicate the prominent correlation. The test results are designated using Taguchi’s and ANOVA concept. S/N ratio indicates that there are 1.72% deviations that are estimated between predicted and experimental results. To elaborately analyze the results, ANN and GMDH methods are mentioned. After erosion process of tested composite, the damage propagation on surfaces is examined using SEM for the confirmation of possible nature of wear behavior. The elemental composition of eroded test samples at varying percentage of gunmetal is analyzed by EDX analysis.

  15. Parrotfish erosion underpins reef growth, sand talus development and island building in the Maldives

    Science.gov (United States)

    Morgan, Kyle M.; Kench, Paul S.

    2016-07-01

    Parrotfish play a key functional role on coral reefs as external bioerosion agents and produce large quantities of carbonate sediment as a by-product of grazing on reef surfaces. Parrotfish are therefore an important potential source of sediment for island construction and maintenance within atoll reef environments, particularly under future scenarios of sea level rise and island morphological change. Here, we present the first field-based estimates of excavating parrotfish erosion (Chlorurus sordidus and Chlorurus strongylocephalus) within the Indian Ocean and quantify the contribution of parrotfish to the carbonate and sediment budgets of an atoll interior reef platform in the Maldives. We note that parrotfish erosion rates are high (6.3 kg m- 2 y- 1), generating large amounts of new coral-based sediment (2.6 kg m- 2 y- 1) that has a comparable grain size distribution to island deposits. Mean erosion rates by individual C. strongylocephalus (405 kg individual y- 1) were higher than C. sordidus (55 kg individual y- 1), but their contribution to erosion per unit area of reef was less due to a lower relative biomass (C. strongylocephalus: 1.3 kg m- 2 y- 1; C. sordidus: 5.0 kg m- 2 y- 1). Parrotfish also facilitate sediment export from reefs (0.7 kg m- 2 y- 1), which contributes extensively to the development of the sand talus on the fore-reef slope and to the evolution of the wider atoll basin. Our results provide strong evidence that parrotfish erosion (and sediment generation) underpins island morphology on Maldivian reefs and highlight the importance of larger parrotfish as producers of island-grade sediment. Ecological processes must therefore be considered within future coastal management strategies for enhancing island stability.

  16. Measuring splash erosion potential under vegetation using sand-filled splash cups

    Science.gov (United States)

    Geißler, C.; Scholten, T.; Kühn, P.

    2009-04-01

    In soil erosion research it is widely accepted that vegetation is not only protecting the soil from the erosive power of rainfall. Under specific circumstances (like they occur e.g. in forests) vegetation can enhance the erosive power of rainfall by modifying its properties (esp. drop size distribution, kinetic energy). The adjacent processes are very complex and variable in time and space and depend on numerous variables (e.g. rainfall intensity, drop size distribution, drop fall velocity, height of the canopy, density of the canopy, crown and leaf traits, LAI). In the last decades a large number of studies focused this process-system using different methods and came to often different results (Brandt 1989; Calder 2001; Foot & Morgan 2005; Hall & Calder 1993; Mosley 1982; Nanko et al. 2006; Park & Cameron 2008; Vis 1986). The main objective of our field experiments in subtropical China is to quantify the modification of precipitation by its pass through the canopy layer for six different tree species, three different successional stages and three different biodiversity classes. For this, new splash cups were developed based on the archetype of Ellison (1947). In contrast to previous studies with splash cups (Vis 1986) or other forms of splash cups (Kinnell 1974; Morgan 1981) we measured the unit sand remaining inside the cup after single natural rainfall events. The new splash cups contain of a PE-flask to which a carrier system has been attached. In this carrier system a cup filled with unit sand of 125-200 µm particle size is inserted. At the bottom of the cup a silk cover is attached to avoid the loss of sand and to guarantee free drainage of water from the cup to the carrier and vice versa. Cup and PE-flask are hydraulically connected by a cotton wick to assure constant moisture content throughout the time of measuring. Additionally, vents in the carrier system ensure that the pressure arising from the insertion of the cup doesn't lead to a loss of sand. The

  17. Effect of Annealing Treatment on Erosion-Corrosion of Zr-Based Bulk Metallic Glass in Saline-Sand Slurry

    Science.gov (United States)

    Ji, Xiulin; Shan, Yiping; Chen, Yueyue; Wang, Hui

    2016-06-01

    Bulk metallic glass (BMG) may be a good candidate to solve the erosion-corrosion (E-C) problems of marine pumps in sand-containing seawater. Since annealing treatment is an effective way to improve plasticity of BMGs, the effect of annealing treatment on E-C wear of Zr-based BMG in saline-sand slurry was investigated. All of the annealed BMG samples were crystallized and the quantity of (Zr, Cu) phase increased but that of Al4Cu9 phase decreased with the increase of annealing temperature from 360 to 480 °C. Accordingly, annealing treatment enhances plasticity of the as-cast BMG at the cost of hardness and corrosion resistance. Moreover, 480 °C annealed BMG sample possesses the highest hardness and the lowest corrosion current density in all of the annealed BMG samples. Using a slurry pot erosion tester, the E-C wear of the as-cast and annealed BMG samples was studied under different impingement angles, impact velocities, and concentrations in saline-sand slurry. With the improvement of plasticity, 480 °C annealed BMG sample exhibits the best E-C wear resistance under high impingement angle, high impact velocity, and high sand concentration.

  18. Erosion-corrosion in carbon dioxide saturated systems in presence of sand, inhibitor, oil, and high concentration of salt

    Science.gov (United States)

    Hassani, Shokrollah

    Oil and gas production is usually accompanied by formation water which typically contains high levels of chloride. Some effects of chloride concentration on corrosion are not widely known in the literature, and this can result in misleading conclusions. One goal of this research was to contribute to a better understanding of the effects of chloride concentration in CO2 corrosion. Experimental and theoretical studies conducted in the present work have shown that increasing the NaCl concentration in solution has three important effects on corrosion results. First, standard pH meter readings in high NaCl concentration solutions require corrections. Second, increasing the NaCl concentration decreases the CO2 concentration in solution and therefore contributes to a decrease in the corrosion rate. Third, increasing the NaCl concentration increases the solubility of FeCO3 and therefore reduces the likelihood of forming an iron carbonate scale. High NaCl concentration also decreases the sand erosion rate of the metal slightly by increasing the density and viscosity of the liquid. There are two main contributions of this research. The first contribution is the experimental characterization of inhibited erosion-corrosion behavior of mild steel under CO2-saturated conditions with a high salt concentration. Chemical inhibition is one the most important techniques for controlling erosion-corrosion in offshore mild steel pipelines, tubing and pipe fittings in oil and gas industry. The second contribution is the introduction of a new approach for predicting inhibited erosion-corrosion in mild steel pipes including the effects of flow and environmental conditions, sand production, and an oil phase. Sand erosion can decrease the efficiency of corrosion protection systems including iron-carbonate scale formation and chemical inhibition. The need to be able to predict inhibitor performance under sand production conditions is particularly acute when the wells are deep or off

  19. Tillage techniques to reactivate aeolian erosion on inland drift-sand

    NARCIS (Netherlands)

    Riksen, M.J.P.M.; Goossens, D.

    2005-01-01

    The inland drift-sand areas in northern Europe are characterised by a rapid decline in both aeolian activity and areal size. Many former drift-sand surfaces have become immobilised by natural or man-induced processes, such as conversion into forest or other terrain for agricultural, economic or soci

  20. Laboratory rainfall experiments on raindrop impacted flow erosion of different sand mixtures.

    Science.gov (United States)

    Fister, Wolfgang; Mayer, Marius; Kinnell, Peter I. A.; Kuhn, Nikolaus J.

    2015-04-01

    Soil erosion is a globally occurring process that causes the loss of nutrient rich soil all over the world. Because of its global importance, many investigations in the last decades have sought to improve our understanding of the involved processes and to develop predictive tools or models to support farmers in reducing the threat of soil erosion. However, the mechanistic and physical understanding of the processes are still not well enough understood, so that predicting models often perform relative poorly outside of their test environment. One reason, why there is still a lack of knowledge, could be, that many investigations were performed under as natural as possible conditions, before the actual basics are properly understood. This resulted in highly complex systems with rather uncontrolled experimental conditions, so that the experimental data was a result of many different parameters. The main aim of this study was to improve the mechanistic understanding of raindrop impacted flow erosion, by using a bottom-up approach. Under highly controlled experimental conditions, most of the influencing parameters like flow velocity and depth, raindrop size, spatial rainfall distribution, and fall velocity were kept as constant as possible. By changing only the size distribution of the sandy substrate, specific relations between drop kinetic energy, force of flow and transport rate could be collected. This contribution shows the experimental design and presents preliminary, but promising results that indicate that this bottom-up approach could lead to a better understanding of the erosion process in raindrop impacted flows.

  1. Airfoils and method for designing airfoils

    DEFF Research Database (Denmark)

    2010-01-01

    The present invention relates to airfoils and design and design optimization of airfoils, in particular airfoils of rotor blades for wind turbines. One aspect of the invention relates to an airfoil with an external shape provided by an airfoil profile defined by a limited number of parameters, such...... as a set of parameters. Another aspect of the invention relates to a method for designing an airfoil by means of an analytical airfoil profile, said method comprising the step of applying a conformal mapping to a near circle in a near circle plane, wherein the near circle is at least partly expressed...... by means of an analytical function, said conformal mapping transforming the near circle in the near circle plane to the airfoil profile in an airfoil plane. L...

  2. 搭设障蔽控制樟子松风蚀沙埋危害的效果%Control Effect on Wind Erosion and Sand Cover by Building Sand-Barrier for Pinus sylvestris var.mongolica Plantation

    Institute of Scientific and Technical Information of China (English)

    屈升银; 叶竹林

    2011-01-01

    The control effect on wind erosion and sand cover by building sand-barrier was studied by taking Pinus sylvestris var. Mongolica as planting tree species. The results showed that building sand-barrier could promote the survival rate of the plantation up to 100% , which was significantly higher than that of the control. There were also significant differences in the growth rate of the Pinus sylvestris var. Mongolica plantation between building the sand-barrier and the control. The experiment showed that building the sand-barrier could promote the average sapling height, basal diameter and crown growth by 55.4% , 66. 6% and 60.1% respectively compared to the control. Sand-barrier building provided the morphology construction of the Pinus sylvestris var. Mongolica saplings with much better environment that significantly reduced the phenomena such as trunk bending, wind throw and drying up of the brnaches and turning yellow of the leaves due to the wind damage.%以樟子松为对象探讨搭设沙障控制风蚀沙埋危害的效果.结果表明:搭设与未搭设沙障的造林保存率存在显著差异,搭设沙障可使造林保存率高达100%;搭设与未搭设沙障的生长量也存在显著差异,搭设沙障可使树高、地径、树冠生长量分别提高55.4%、66.6%和60.7%;搭设沙障为樟子松的形态建成创造了良好的环境条件,树干弯曲、风倒及枯黄现象明显减少.

  3. Vertical distribution of soil moisture and surface sandy soil wind erosion for different types of sand dune on the southeastern margin of the Mu Us Sandy Land, China

    Institute of Scientific and Technical Information of China (English)

    ChaoFeng Fu; JingBo Zhao; FanMin Mei; TianJie Shao; Jun Zuo

    2015-01-01

    Soil moisture is a critical state affecting a variety of land surface and subsurface processes. We report investigation results of the factors controlling vertical variation of soil moisture and sand transport rate of three types of dunes on the south-eastern margin of the Mu Us Sandy Land. Samples were taken from holes drilled to a depth of 4 m at different topographic sites on the dunes, and were analyzed for soil moisture, grain-size distribution and surface sediment discharge. The results show that: (1) The average soil moisture varies in different types of dunes, with the following sequences ordered from highest to lowest: in the shrubs-covered dunes and the trees-covered dunes the sequence is from inter-dunes lowland to windward slope to leeward slope. The average moisture in the bare-migratory sand dunes is sequenced from inter-dunes lowland to leeward slope to windward slope. (2) Vegetation form and surface coverage affect the range of soil moisture of different types of dunes in the same topographic position. The coefficient of variation of soil moisture for shrubs-covered dunes is higher than that of other types of dune. (3) The effect of shrubs on dune soil moisture is explained in terms of the greater ability of shrubs to trap fine-grained atmospheric dust and hold moisture. (4) The estimated sand transport rates over sand dunes with sparse shrubs are less than those over bare-migratory dunes or sand dunes with sparse trees, indi-cating that shrubs are more effective in inhibiting wind erosion in the sandy land area.

  4. Evaluation of the Synergistic Effect of Erosion-Corrosion on AISI 4330 Steel in Saline-Sand Multiphase Flow by Electrochemical and Gravimetric Techniques

    Directory of Open Access Journals (Sweden)

    Dario Yesid Peña Ballesteros

    2016-01-01

    Full Text Available The synergistic effects of fluid flow, sand particles, and solution pH on erosion-corrosion of AISI 4330 steel alloy in saline-sand medium were studied through a rotating cylinder electrode (RCE system by weight-loss and electrochemical measurements. The worn surface was analyzed by X-ray diffraction (XRD and scanning electron microscopy (SEM. Results show that, under all the test conditions assessed, the passivity of the steel alloy could not be maintained; as a result, an activation mechanism dominates the corrosion process of steel alloy. Furthermore, the potentiodynamic curves show that, with the increasing of the electrode flow rate and particle size, the anodic current density increased, which is due to deterioration of the electrode by the impacting slurry. Although the increase of particle size affects the anodic current density, the effect of particle size does not cause a significant change in the polarization behavior of the steel electrode. The electrochemical impedance and potentiodynamic curves suggest that erosion-corrosion phenomenon of the ASISI 4330 steel is under mixed control of mass transport and charge transfer. The inductive loops formed in the impedance plots are representative of an increase in roughness of the electrode caused by the particles impacting at the surface. The change in the passivity of the steel alloy as the pH is altered plays an important role in the corrosion rate.

  5. Reinforced Airfoil Shaped Body

    DEFF Research Database (Denmark)

    2011-01-01

    The present invention relates to an airfoil shaped body with a leading edge and a trailing edge extending along the longitudinal extension of the body and defining a profile chord, the airfoil shaped body comprising an airfoil shaped facing that forms the outer surface of the airfoil shaped body...

  6. Supercritical Airfoil Coordinates

    Data.gov (United States)

    National Aeronautics and Space Administration — Rectangular Supercritical Wing (Ricketts) - design and measured locations are provided in an Excel file RSW_airfoil_coordinates_ricketts.xls . One sheet is with Non...

  7. Closed loop steam cooled airfoil

    Science.gov (United States)

    Widrig, Scott M.; Rudolph, Ronald J.; Wagner, Gregg P.

    2006-04-18

    An airfoil, a method of manufacturing an airfoil, and a system for cooling an airfoil is provided. The cooling system can be used with an airfoil located in the first stages of a combustion turbine within a combined cycle power generation plant and involves flowing closed loop steam through a pin array set within an airfoil. The airfoil can comprise a cavity having a cooling chamber bounded by an interior wall and an exterior wall so that steam can enter the cavity, pass through the pin array, and then return to the cavity to thereby cool the airfoil. The method of manufacturing an airfoil can include a type of lost wax investment casting process in which a pin array is cast into an airfoil to form a cooling chamber.

  8. Wind turbine airfoil catalogue

    Energy Technology Data Exchange (ETDEWEB)

    Bertagnolio, F.; Soerensen, N.; Johansen, J.; Fuglsang, P.

    2001-08-01

    The aim of this work is two-sided. Firstly, experimental results obtained for numerous sets of airfoil measurements (mainly intended for wind turbine applications) are collected and compared with computational results from the 2D Navier-Stokes solver EllipSys2D, as well as results from the panel method code XFOIL. Secondly, we are interested in validating the code EllipSys2D and finding out for which air-foils it does not perform well compared to the experiments, as well as why, when it does so. The airfoils are classified according to the agreement between the numerical results and experimental data. A study correlating the available data and this classification is performed. It is found that transition modelling is to a large extent responsible for the poor quality of the computational results for most of the considered airfoils. The transition model mechanism that leads to these discrepancies is identified. Some advices are given for elaborating future airfoil design processes that would involve the numerical code EllipSys2D in particular, and transition modelling in general. (au)

  9. Evaluation of Erosion Resistance of Advanced Turbine Thermal Barrier Coatings

    Science.gov (United States)

    Zhu, Dongming; Kuczmarski, Maria A.; Miller, Robert A.; Cuy, Michael D.

    2007-01-01

    The erosion resistant turbine thermal barrier coating system is critical to aircraft engine performance and durability. By demonstrating advanced turbine material testing capabilities, we will be able to facilitate the critical turbine coating and subcomponent development and help establish advanced erosion-resistant turbine airfoil thermal barrier coatings design tools. The objective of this work is to determine erosion resistance of advanced thermal barrier coating systems under simulated engine erosion and/or thermal gradient environments, validating advanced turbine airfoil thermal barrier coating systems based on nano-tetragonal phase toughening design approaches.

  10. Characteristics of Grain Size of Wind Erosion in Sand Flow Structure of Farmland%农田风沙流结构中风蚀物粒度特征的变化

    Institute of Scientific and Technical Information of China (English)

    要洁; 魏立涛; 常春平

    2012-01-01

    [ Objective] The research aimed to study the characteristics of grain size of wind erosion in Hebei Bashang Kangbao County farm* land in the vertical height and the level of the distance, [Method] In Kangbao County, field observation was conducted to determine the size of farmland wind erosion with Malvern laser particle size analyzer, [Method] The sand flow wind erosion content with > 0.01 mm size was given priority to, and the content were more than 80%. All kinds of cultivated land were concentrated in wind erosion particle size of 0, 05 - 0. 25 mm, and wind erosion was relatively serious in the range of particle size. In vertical height, the average particle size of the wind erosion declined exponentially. [ Conclusion] The research could provide the basis for the selection of the windbreak method and the prevention of the wind erosion in the farm.%[目的]了解河北坝上康保县农田风沙流中风蚀物的粒度在垂直高度和水平距离上的变化规律.[方法]在康保县选择农田进行野外观测,再对农田风蚀物用马尔文激光粒度仪进行粒度测定.[结果]风沙流中的风蚀物以>0.01 mm粒径为主,含量均在80%以上.各类耕地风蚀物粒径均集中在0.05~0.25 mm,且在这一粒径范围内风蚀较为严重.在垂直高度上,风蚀物的平均粒径随着垂直高度的增加呈指数递减.[结论]该研究可以为采取防风措施、防治农田风蚀提供依据.

  11. Runoff erosion

    OpenAIRE

    Evelpidou, Niki; Cordier, Stephane (Ed.); Merino, Agustin (Ed.); Figueiredo, Tomás de; Centeri, Csaba

    2013-01-01

    Table of Contents PART I – THEORY OF RUNOFF EROSION CHAPTER 1 - RUNOFF EROSION – THE MECHANISMS CHAPTER 2 - LARGE SCALE APPROACHES OF RUNOFF EROSION CHAPTER 3 - MEASURING PRESENT RUNOFF EROSION CHAPTER 4 - MODELLING RUNOFF EROSION CHAPTER 5 - RUNOFF EROSION AND HUMAN SOCIETIES: THE INFLUENCE OF LAND USE AND MANAGEMENT PRACTICES ON SOIL EROSION PART II - CASE STUDIES CASE STUDIES – INTRODUCTION: RUNOFF EROSION IN MEDITERRANEAN AREA CASE STUDY 1: Soil Erosion Risk...

  12. Design and Performance Optimizations of Advanced Erosion-Resistant Low Conductivity Thermal Barrier Coatings for Rotorcraft Engines

    Science.gov (United States)

    Zhu, Dongming; Miller, Robert A.; Kuczmarski, Maria A.

    2012-01-01

    Thermal barrier coatings will be more aggressively designed to protect gas turbine engine hot-section components in order to meet future rotorcraft engine higher fuel efficiency and lower emission goals. For thermal barrier coatings designed for rotorcraft turbine airfoil applications, further improved erosion and impact resistance are crucial for engine performance and durability, because the rotorcraft are often operated in the most severe sand erosive environments. Advanced low thermal conductivity and erosion-resistant thermal barrier coatings are being developed, with the current emphasis being placed on thermal barrier coating toughness improvements using multicomponent alloying and processing optimization approaches. The performance of the advanced thermal barrier coatings has been evaluated in a high temperature erosion burner rig and a laser heat-flux rig to simulate engine erosion and thermal gradient environments. The results have shown that the coating composition and architecture optimizations can effectively improve the erosion and impact resistance of the coating systems, while maintaining low thermal conductivity and cyclic oxidation durability

  13. Multi-Element Airfoil System

    Science.gov (United States)

    Turner, Travis L. (Inventor); Khorrami, Mehdi R. (Inventor); Lockard, David P. (Inventor); McKenney, Martin J. (Inventor); Atherley, Raymond D. (Inventor); Kidd, Reggie T. (Inventor)

    2014-01-01

    A multi-element airfoil system includes an airfoil element having a leading edge region and a skin element coupled to the airfoil element. A slat deployment system is coupled to the slat and the skin element, and is capable of deploying and retracting the slat and the skin element. The skin element substantially fills the lateral gap formed between the slat and the airfoil element when the slat is deployed. The system further includes an uncoupling device and a sensor to remove the skin element from the gap based on a critical angle-of-attack of the airfoil element. The system can alternatively comprise a trailing edge flap, where a skin element substantially fills the lateral gap between the flap and the trailing edge region of the airfoil element. In each case, the skin element fills a gap between the airfoil element and the deployed flap or slat to reduce airframe noise.

  14. Oscillatory blowing airfoil

    Science.gov (United States)

    1997-01-01

    10' NACA 0015 with 30% chord trailing edge flap deflected 20 degrees. Used in 0.3 Meter Transonic Cryogenic Tunnel, this airfoil has a 0.44 mm slot at 70% chord. Oscillatory blowing out of slot used for separation control. Howard Price appears in side view shot, in building 1145, Studio.

  15. Wind turbine airfoil catalogue

    DEFF Research Database (Denmark)

    Bertagnolio, F.; Sørensen, Niels N.; Johansen, Jeppe;

    2001-01-01

    The aim of this work is two-sided. Firstly, experimental results obtained for numerous sets of airfoil measurements (mainly intended for wind turbine applications) are collected and compared with computational results from the 2D Navier-Stokes solverEllipSys2D, as well as results from the panel...

  16. Vertical axis wind turbine airfoil

    Science.gov (United States)

    Krivcov, Vladimir; Krivospitski, Vladimir; Maksimov, Vasili; Halstead, Richard; Grahov, Jurij Vasiljevich

    2012-12-18

    A vertical axis wind turbine airfoil is described. The wind turbine airfoil can include a leading edge, a trailing edge, an upper curved surface, a lower curved surface, and a centerline running between the upper surface and the lower surface and from the leading edge to the trailing edge. The airfoil can be configured so that the distance between the centerline and the upper surface is the same as the distance between the centerline and the lower surface at all points along the length of the airfoil. A plurality of such airfoils can be included in a vertical axis wind turbine. These airfoils can be vertically disposed and can rotate about a vertical axis.

  17. Airfoils in Turbulent Inflow

    DEFF Research Database (Denmark)

    Gilling, Lasse

    Wind turbines operate in inflow turbulence whether it originates from the shear in the atmospheric boundary layer or from the wake of other wind turbines. Consequently, the airfoils of the wings experience turbulence in the inflow. The main topic of this thesis is to investigate the effect...... of resolved inflow turbulence on airfoil simulations in CFD. The detached-eddy simulation technique is used because it can resolve the inflow turbulence without becoming too computationally expensive due to its limited requirements for mesh resolution in the boundary layer. It cannot resolve the turbulence...... that is formed in attached boundary layers, but the freestream turbulence can penetrate the boundary layer. The idea is that the resolved turbulence from the freestream should mix high momentum flow into the boundary layer and thereby increase the resistance against separation and increase the maximum lift...

  18. Aerodynamic performance of transonic and subsonic airfoils: Effects of surface roughness, turbulence intensity, Mach number, and streamline curvature-airfoil shape

    Science.gov (United States)

    Zhang, Qiang

    The effects of surface roughness, turbulence intensity, Mach number, and streamline curvature-airfoil shape on the aerodynamic performance of turbine airfoils are investigated in compressible, high speed flows. The University of Utah Transonic Wind Tunnel is employed for the experimental part of the study. Two different test sections are designed to produce Mach numbers, Reynolds numbers, passage mass flow rates, and physical dimensions, which match values along turbine blades in operating engines: (i) a nonturning test section with a symmetric airfoil, and (ii) a cascade test section with a cambered turbine vane. The nonuniform, irregular, three-dimensional surface roughness is characterized using the equivalent sand grain roughness size. Changing the airfoil surface roughness condition has a substantial effect on wake profiles of total pressure loss coefficients, normalized Mach number, normalized kinetic energy, and on the normalized and dimensional magnitudes of Integrated Aerodynamic Losses produced by the airfoils. Comparisons with results for a symmetric airfoil and a cambered vane show that roughness has more substantial effects on losses produced by the symmetric airfoil than the cambered vane. Data are also provided that illustrate the larger loss magnitudes are generally present with flow turning and cambered airfoils, than with symmetric airfoils. Wake turbulence structure of symmetric airfoils and cambered vanes are also studied experimentally. The effects of surface roughness and freestream turbulence levels on wake distributions of mean velocity, turbulence intensity, and power spectral density profiles and vortex shedding frequencies are quantified one axial chord length downstream of the test airfoils. As the level of surface roughness increases, all wake profile quantities broaden significantly and nondimensional vortex shedding frequencies decrease. Wake profiles produced by the symmetric airfoil are more sensitive to variations of surface

  19. Turbine airfoil to shround attachment

    Science.gov (United States)

    Campbell, Christian X; Morrison, Jay A; James, Allister W; Snider, Raymond G; Eshak, Daniel M; Marra, John J; Wessell, Brian J

    2014-05-06

    A turbine airfoil (31) with an end portion (42) that tapers (44) toward the end (43) of the airfoil. A ridge (46) extends around the end portion. It has proximal (66) and distal (67) sides. A shroud platform (50) is bi-cast onto the end portion around the ridge without bonding. Cooling shrinks the platform into compression (62) on the end portion (42) of the airfoil. Gaps between the airfoil and platform are formed using a fugitive material (56) in the bi-casting stage. These gaps are designed in combination with the taper angle (44) to accommodate differential thermal expansion while maintaining a gas seal along the contact surfaces. The taper angle (44) may vary from lesser on the pressure side (36) to greater on the suction side (38) of the airfoil. A collar portion (52) of the platform provides sufficient contact area for connection stability.

  20. Erosion-Resistant Nanocoatings for Improved Energy Efficiency in Gas Turbine Engines

    Energy Technology Data Exchange (ETDEWEB)

    None

    2009-06-01

    This factsheet describes a research project whose goal is to test and substantiate erosion-resistant (ER) nanocoatings for application on compressor airfoils for gas turbine engines in both industrial gas turbines and commercial aviation.

  1. Unsteady flow about a circulation control airfoil

    Institute of Scientific and Technical Information of China (English)

    刘晶昌; 孙茂; 吴礼义

    1996-01-01

    The unsteady flow around a circulation control (CC) airfoil was investigated with Navier-Stokes method,which includes the flow around CC airfoil with pulsating jet,the flow around oscillating CC airfoil,and the flow around oscillating CC airfoil with pulsating jet.Dynamic properties of the flow and the aerodynamic forces were rewaled.

  2. Modeling aeolian erosion in presence of vegetation

    Science.gov (United States)

    Dupont, S.; Bergametti, G.; Simoëns, S.

    2014-02-01

    Semiarid landscapes are characterized by vegetated surfaces. Understanding the impact of vegetation on aeolian soil erosion is important for reducing soil erosion or limiting crop damage through abrasion or burial. In the present study, a saltation model fully coupled with a large-eddy simulation airflow model is extended to vegetated landscapes. From this model, the sensitivity of sand erosion to different arrangements and type of plants (shrub versus tree) representative of semiarid landscapes is investigated and the wind erosion reduction induced by plants is quantified. We show that saltation processes over vegetated surfaces have a limited impact on the mean wind statistics, the momentum extracted from the flow by saltating particles being negligible compared to that extracted by plants. Simulated sand erosion patterns resulting from plant distribution, i.e., accumulation and erosion areas, appear qualitatively consistent with previous observations. It is shown that sand erosion reduction depends not only on vegetation cover but also on plant morphology and plant distribution relative to the mean wind direction. A simple shear stress partitioning approach applied in shrub cases gives similar trends of sand erosion reduction as the present model following wind direction and vegetation cover. However, the magnitude of the reduction appears significantly different from one approach to another. Although shrubs trap saltating particles, trees appear more efficient than shrubs to reduce sand erosion. This is explained by the large-scale sheltering effect of trees compared to the local shrub one.

  3. Airfoil nozzle and shroud assembly

    Science.gov (United States)

    Shaffer, James E.; Norton, Paul F.

    1997-01-01

    An airfoil and nozzle assembly including an outer shroud having a plurality of vane members attached to an inner surface and having a cantilevered end. The assembly further includes a inner shroud being formed by a plurality of segments. Each of the segments having a first end and a second end and having a recess positioned in each of the ends. The cantilevered end of the vane member being positioned in the recess. The airfoil and nozzle assembly being made from a material having a lower rate of thermal expansion than that of the components to which the airfoil and nozzle assembly is attached.

  4. Flatback airfoil wind tunnel experiment.

    Energy Technology Data Exchange (ETDEWEB)

    Mayda, Edward A. (University of California, Davis, CA); van Dam, C.P. (University of California, Davis, CA); Chao, David D. (University of California, Davis, CA); Berg, Dale E.

    2008-04-01

    A computational fluid dynamics study of thick wind turbine section shapes in the test section of the UC Davis wind tunnel at a chord Reynolds number of one million is presented. The goals of this study are to validate standard wind tunnel wall corrections for high solid blockage conditions and to reaffirm the favorable effect of a blunt trailing edge or flatback on the performance characteristics of a representative thick airfoil shape prior to building the wind tunnel models and conducting the experiment. The numerical simulations prove the standard wind tunnel corrections to be largely valid for the proposed test of 40% maximum thickness to chord ratio airfoils at a solid blockage ratio of 10%. Comparison of the computed lift characteristics of a sharp trailing edge baseline airfoil and derived flatback airfoils reaffirms the earlier observed trend of reduced sensitivity to surface contamination with increasing trailing edge thickness.

  5. Airfoil characteristics for wind turbines

    DEFF Research Database (Denmark)

    Bak, C.; Fuglsang, P.; Sørensen, Niels N.;

    1999-01-01

    Airfoil characteristics for use in the Blade Element Momentum (BEM) method calculating the forces on Horizontal Axis Wind Turbines (HAWT) are derived by use of systematic methods. The investigation and derivation of the airfoil characteristics are basedon four different methods: 1) Inverse momentum...... theory, 2) Actuator disc theory, 3) Numerical optimisation and 4) Quasi-3D CFD computations. The two former methods are based on 3D CFD computations and wind tunnel measurements on a 41-m full-scale rotorwith LM 19.1 blades. The derived airfoil characteristics show that the lift coefficient in stall...... to a commonly used set of airfoil characteristics. The numerical optimisation is based on both the 3D CFDcomputations and measurements on a 41-m rotor with LM 19.1 and LM 19.0 blades, respectively. The method requires power and loads from a turbine and is promising since a set of lift and drag curves is derived...

  6. Boundary Layer Control on Airfoils.

    Science.gov (United States)

    Gerhab, George; Eastlake, Charles

    1991-01-01

    A phenomena, boundary layer control (BLC), produced when visualizing the fluidlike flow of air is described. The use of BLC in modifying aerodynamic characteristics of airfoils, race cars, and boats is discussed. (KR)

  7. Analysis of a theoretically optimized transonic airfoil

    Science.gov (United States)

    Lores, M. E.; Burdges, K. P.; Shrewsbury, G. D.

    1978-01-01

    Numerical optimization was used in conjunction with an inviscid, full potential equation, transonic flow analysis computer code to design an upper surface contour for a conventional airfoil to improve its supercritical performance. The modified airfoil was tested in a compressible flow wind tunnel. The modified airfoil's performance was evaluated by comparison with test data for the baseline airfoil and for an airfoil developed by optimization of leading edge of the baseline airfoil. While the leading edge modification performed as expected, the upper surface re-design did not produce all of the expected performance improvements. Theoretical solutions computed using a full potential, transonic airfoil code corrected for viscosity were compared to experimental data for the baseline airfoil and the upper surface modification. These correlations showed that the theory predicted the aerodynamics of the baseline airfoil fairly well, but failed to accurately compute drag characteristics for the upper surface modification.

  8. Nozzle airfoil having movable nozzle ribs

    Science.gov (United States)

    Yu, Yufeng Phillip; Itzel, Gary Michael

    2002-01-01

    A nozzle vane or airfoil structure is provided in which the nozzle ribs are connected to the side walls of the vane or airfoil in such a way that the ribs provide the requisite mechanical support between the concave side and convex side of the airfoil but are not locked in the radial direction of the assembly, longitudinally of the airfoil. The ribs may be bi-cast onto a preformed airfoil side wall structure or fastened to the airfoil by an interlocking slide connection and/or welding. By attaching the nozzle ribs to the nozzle airfoil metal in such a way that allows play longitudinally of the airfoil, the temperature difference induced radial thermal stresses at the nozzle airfoil/rib joint area are reduced while maintaining proper mechanical support of the nozzle side walls.

  9. Airfoil characteristics for wind turbines

    Energy Technology Data Exchange (ETDEWEB)

    Bak, C.; Fuglsang, P.; Soerensen, N.N.; Aagaard Madsen, H. [Risoe National Lab., Roskilde (Denmark); Wen Zhong Shen; Noerkaer Soerensen, J. [Technical Univ. of Denmark, Lyngby (Denmark)

    1999-03-01

    Airfoil characteristics for use in the Blade Element Momentum (BEM) method calculating the forces on Horizontal Axis Wind Turbines (HAWT) are derived by use of systematic methods. The investigation and derivation of the airfoil characteristics are based on four different methods: 1) Inverse momentum theory, 2) Actuator disc theory, 3) Numerical optimisation and 4) Quasi-3D CFD computations. The two former methods are based on 3D CFD computations and wind tunnel measurements on a 41-m full-scale rotor with LM 19.1 blades. The derived airfoil characteristics show that the lift coefficient in stall at the tip is low and that it is high at the root compared to 2D airfoil characteristics. The use of these characteristics in aeroelastic calculations shows a good agreement in power and flap moments with measurements. Furthermore, a fatigue analysis shows a reduction in the loads of up to 15 % compared to a commonly used set of airfoil characteristics. The numerical optimisation is based on both the 3D CFD computations and measurements on a 41-m rotor with LM 19.1 and LM 19.0 blades, respectively. The method requires power and loads from a turbine and is promising since a set of lift and drag curves is derived that can be used to calculate mean values of power and loads. The lift in stall at the tip is low and at the root it is high compared to 2D airfoil characteristics. In particular the power curves were well calculated by use of the optimised airfoil characteristics. In the quasi-3D CFD computations, the airfoil characteristics are derived directly. This Navier-Stokes model takes into account rotational and 3D effects. The model enables the study of the rotational effect of a rotor blade at computing costs similar to what is typical for 2D airfoil calculations. The depicted results show that the model is capable of determining the correct qualitative behaviour for airfoils subject to rotation. The method shows that lift is high at the root compared to 2D airfoil

  10. Robust design of NLF airfoils

    Institute of Scientific and Technical Information of China (English)

    Li Jing; Gao Zhenghong; Huang Jiangtao; Zhao Ke

    2013-01-01

    A robust optimization design approach of natural laminar airfoils is developed in this paper.First,the non-uniform rational B-splines (NURBS) free form deformation method based on NURBS basis function is introduced to the airfoil parameterization.Second,aerodynamic characteristics are evaluated by solving Navier Stokes equations,and the γ-Reθt transition model coupling with shear-stress transport (SST) turbulent model is introduced to simulate boundary layer transition.A numerical simulation of transition flow around NLF0416 airfoil is conducted to test the code.The comparison between numerical simulation results and wind tunnel test data approves the validity and applicability of the present transition model.Third,the optimization system is set up,which uses the separated particle swarm optimization (SPSO) as search algorithm and combines the Kriging models as surrogate model during optimization.The system is applied to carry out robust design about the uncertainty of lift coefficient and Mach number for NASA NLF-0115 airfoil.The data of optimized airfoil aerodynamic characteristics indicates that the optimized airfoil can maintain laminar flow stably in an uncertain range and has a wider range of low drag.

  11. Airfoil deposition model

    Science.gov (United States)

    Kohl, F. J.

    1982-01-01

    The methodology to predict deposit evolution (deposition rate and subsequent flow of liquid deposits) as a function of fuel and air impurity content and relevant aerodynamic parameters for turbine airfoils is developed in this research. The spectrum of deposition conditions encountered in gas turbine operations includes the mechanisms of vapor deposition, small particle deposition with thermophoresis, and larger particle deposition with inertial effects. The focus is on using a simplified version of the comprehensive multicomponent vapor diffusion formalism to make deposition predictions for: (1) simple geometry collectors; and (2) gas turbine blade shapes, including both developing laminar and turbulent boundary layers. For the gas turbine blade the insights developed in previous programs are being combined with heat and mass transfer coefficient calculations using the STAN 5 boundary layer code to predict vapor deposition rates and corresponding liquid layer thicknesses on turbine blades. A computer program is being written which utilizes the local values of the calculated deposition rate and skin friction to calculate the increment in liquid condensate layer growth along a collector surface.

  12. Hook nozzle arrangement for supporting airfoil vanes

    Science.gov (United States)

    Shaffer, James E.; Norton, Paul F.

    1996-01-01

    A gas turbine engine's nozzle structure includes a nozzle support ring, a plurality of shroud segments, and a plurality of airfoil vanes. The plurality of shroud segments are distributed around the nozzle support ring. Each airfoil vane is connected to a corresponding shroud segment so that the airfoil vanes are also distributed around the nozzle support ring. Each shroud segment has a hook engaging the nozzle support ring so that the shroud segments and corresponding airfoil vanes are supported by the nozzle support ring. The nozzle support ring, the shroud segments, and the airfoil vanes may be ceramic.

  13. Sanding process and permeability change

    Energy Technology Data Exchange (ETDEWEB)

    Xue, S. [Petroleum Univ., Beijing (China); Yuan, Y.

    2004-07-01

    Sand production is a major problem in the petroleum industry, particularly with operators aggressive production schedules. Sand production occurs when the well fluid under high pumping rate dislodges part of the formation solids causing a continuous flux of formation solids. It increases completion costs, plus it erodes casings, pipes and pumps. However, sand production can also effectively increase well productivity in heavy oil and light oil reservoirs.The challenge in understanding the sanding process lies in developing a mathematical model which can predict the amount of sand production. A quantitative model would allow engineers to understand the unique phenomena and evaluate the impact of sand production on reservoir enhancement. Measures could then be taken to reduce unnecessary costs during field operations. In order to develop such a model, the complicated sanding process equations was divided into a fluid flow and sand transport equation, and into a porous solid matrix deforming and stress concentration or failure function equation. The two types of sand production mechanisms that were presented in this paper were the production of coarse sands under mechanical failure and the production of fine sands under hydro-dynamical erosion. The behaviour of sandstone deformation was examined using the Drucker-Prager constitutive law with cap hardening criterion. The governing equation system was solved using the finite element method. The model was validated using field data for sand production and permeability change obtained from 10 wells in Gudong, China. It was shown that permeability can be modified at any time during the sanding process of a well. Permeability can be reduced by up to 60 per cent of the initial level under depletion production. It was determined that the best way to control permeability decline is to balance the pore pressure. 9 refs., 1 tab., 7 figs.

  14. OUT Success Stories: Advanced Airfoils for Wind Turbines

    Science.gov (United States)

    Jones, J.; Green, B.

    2000-08-01

    New airfoils have substantially increased the aerodynamic efficiency of wind turbines. It is clear that these new airfoils substantially increased energy output from wind turbines. Virtually all new blades built in this country today use these advanced airfoil designs.

  15. Design and optimization of tidal turbine airfoil

    Energy Technology Data Exchange (ETDEWEB)

    Grasso, F. [ECN Wind Energy, Petten (Netherlands)

    2012-03-15

    To increase the ratio of energy capture to the loading and, thereby, to reduce cost of energy, the use of specially tailored airfoils is needed. This work is focused on the design of an airfoil for marine application. Firstly, the requirements for this class of airfoils are illustrated and discussed with reference to the requirements for wind turbine airfoils. Then, the design approach is presented. This is a numerical optimization scheme in which a gradient-based algorithm is used, coupled with the RFOIL solver and a composite Bezier geometrical parameterization. A particularly sensitive point is the choice and implementation of constraints .A section of the present work is dedicated to address this point; particular importance is given to the cavitation phenomenon. Finally, a numerical example regarding the design of a high-efficiency hydrofoil is illustrated, and the results are compared with existing turbine airfoils, considering also the effect on turbine performance due to different airfoils.

  16. Effect of water temperature on cohesive soil erosion

    OpenAIRE

    Parks, Olivia Waverly

    2013-01-01

    In light of increased stream temperatures due to urbanization and climate change, theeffect of water temperature on cohesive soil erosion should be explored. The objectives of this study are to: determine the effect of water temperature on the erosion rates of clay; determine how erosion rates vary with clay mineralogy; and, explore the relationship between zeta potential and erosion rate. Samples of kaolinite- and montmorillonite-sand mixtures, and vermiculite-dominated soil were placed in t...

  17. Semi-Empirical Prediction of Airfoil Hysteresis

    Directory of Open Access Journals (Sweden)

    Lance W. Traub

    2016-03-01

    Full Text Available A semi-empirical method is presented to estimate the angular excursion and the lift loss associated with static hysteresis on an airfoil. Wind tunnel data of various airfoils is used to define and validate the methodology. The resulting equation provides a relationship between the size of the hysteresis loop and characteristics of the airfoil. Comparisons of the equation with experiment show encouraging agreement both in terms of the magnitude of the lift loss and the extent of the loop.

  18. Computation of airfoil buffet boundaries

    Science.gov (United States)

    Levy, L. L., Jr.; Bailey, H. E.

    1981-01-01

    The ILLIAC IV computer has been programmed with an implicit, finite-difference code for solving the thin layer compressible Navier-Stokes equation. Results presented for the case of the buffet boundaries of a conventional and a supercritical airfoil section at high Reynolds numbers are found to be in agreement with experimentally determined buffet boundaries, especially at the higher freestream Mach numbers and lower lift coefficients where the onset of unsteady flows is associated with shock wave-induced boundary layer separation.

  19. Wavy flow cooling concept for turbine airfoils

    Science.gov (United States)

    Liang, George

    2010-08-31

    An airfoil including an outer wall and a cooling cavity formed therein. The cooling cavity includes a leading edge flow channel located adjacent a leading edge of the airfoil and a trailing edge flow channel located adjacent a trailing edge of the airfoil. Each of the leading edge and trailing edge flow channels define respective first and second flow axes located between pressure and suction sides of the airfoil. A plurality of rib members are located within each of the flow channels, spaced along the flow axes, and alternately extending from opposing sides of the flow channels to define undulating flow paths through the flow channels.

  20. On the acoustic signature of tandem airfoils: The sound of an elastic airfoil in the wake of a vortex generator

    Science.gov (United States)

    Manela, A.

    2016-07-01

    The acoustic signature of an acoustically compact tandem airfoil setup in uniform high-Reynolds number flow is investigated. The upstream airfoil is considered rigid and is actuated at its leading edge with small-amplitude harmonic pitching motion. The downstream airfoil is taken passive and elastic, with its motion forced by the vortex-street excitation of the upstream airfoil. The non-linear near-field description is obtained via potential thin-airfoil theory. It is then applied as a source term into the Powell-Howe acoustic analogy to yield the far-field dipole radiation of the system. To assess the effect of downstream-airfoil elasticity, results are compared with counterpart calculations for a non-elastic setup, where the downstream airfoil is rigid and stationary. Depending on the separation distance between airfoils, airfoil-motion and airfoil-wake dynamics shift between in-phase (synchronized) and counter-phase behaviors. Consequently, downstream airfoil elasticity may act to amplify or suppress sound through the direct contribution of elastic-airfoil motion to the total signal. Resonance-type motion of the elastic airfoil is found when the upstream airfoil is actuated at the least stable eigenfrequency of the downstream structure. This, again, results in system sound amplification or suppression, depending on the separation distance between airfoils. With increasing actuation frequency, the acoustic signal becomes dominated by the direct contribution of the upstream airfoil motion, whereas the relative contribution of the elastic airfoil to the total signature turns negligible.

  1. Study of airfoil trailing edge bluntness noise

    DEFF Research Database (Denmark)

    Zhu, Wei Jun; Shen, Wen Zhong; Sørensen, Jens Nørkær

    2010-01-01

    -Stokes equations. It provides us possibilities to study details about noise generation mechanism. The formulation of the semi-empirical model is based on acoustic analogy and then curve-fitted with experimental data. Due to its high efficiency, such empirical relation is used for purpose of low noise airfoil......This paper deals with airfoil trailing edge noise with special focus on airfoils with blunt trailing edges. Two methods are employed to calculate airfoil noise: The flow/acoustic splitting method and the semi-empirical method. The flow/acoustic splitting method is derived from compressible Navier...... design or optimization. Calculations from both methods are compared with exist experiments. The airfoil blunt noise is found as a function of trailing edge bluntness, Reynolds number, angle of attack, etc....

  2. Hybrid Optimization for Wind Turbine Thick Airfoils

    Energy Technology Data Exchange (ETDEWEB)

    Grasso, F. [ECN Wind Energy, Petten (Netherlands)

    2012-06-15

    One important element in aerodynamic design of wind turbines is the use of specially tailored airfoils to increase the ratio of energy capture and reduce cost of energy. This work is focused on the design of thick airfoils for wind turbines by using numerical optimization. A hybrid scheme is proposed in which genetic and gradient based algorithms are combined together to improve the accuracy and the reliability of the design. Firstly, the requirements and the constraints for this class of airfoils are described; then, the hybrid approach is presented. The final part of this work is dedicated to illustrate a numerical example regarding the design of a new thick airfoil. The results are discussed and compared to existing airfoils.

  3. Trailing edge modifications for flatback airfoils.

    Energy Technology Data Exchange (ETDEWEB)

    Kahn, Daniel L. (University of California, Davis, CA); van Dam, C.P. (University of California, Davis, CA); Berg, Dale E.

    2008-03-01

    The adoption of blunt trailing edge airfoils (also called flatback airfoils) for the inboard region of large wind turbine blades has been proposed. Blunt trailing edge airfoils would not only provide a number of structural benefits, such as increased structural volume and ease of fabrication and handling, but they have also been found to improve the lift characteristics of thick airfoils. Therefore, the incorporation of blunt trailing edge airfoils would allow blade designers to more freely address the structural demands without having to sacrifice aerodynamic performance. These airfoils do have the disadvantage of generating high levels of drag as a result of the low-pressure steady or periodic flow in the near-wake of the blunt trailing edge. Although for rotors, the drag penalty appears secondary to the lift enhancement produced by the blunt trailing edge, high drag levels are of concern in terms of the negative effect on the torque and power generated by the rotor. Hence, devices are sought that mitigate the drag of these airfoils. This report summarizes the literature on bluff body vortex shedding and bluff body drag reduction devices and proposes four devices for further study in the wind tunnel.

  4. Erosion resistance of bionic functional surfaces inspired from desert scorpions.

    Science.gov (United States)

    Zhiwu, Han; Junqiu, Zhang; Chao, Ge; Li, Wen; Ren, Luquan

    2012-02-01

    In this paper, a bionic method is presented to improve the erosion resistance of machine components. Desert scorpion (Androctonus australis) is a typical animal living in sandy deserts, and may face erosive action of blowing sand at a high speed. Based on the idea of bionics and biologic experimental techniques, the mechanisms of the sand erosion resistance of desert scorpion were investigated. Results showed that the desert scorpions used special microtextures such as bumps and grooves to construct the functional surfaces to achieve the erosion resistance. In order to understand the erosion resistance mechanisms of such functional surfaces, the combination of computational and experimental research were carried out in this paper. The Computational Fluid Dynamics (CFD) method was applied to predict the erosion performance of the bionic functional surfaces. The result demonstrated that the microtextured surfaces exhibited better erosion resistance than the smooth surfaces. The further erosion tests indicated that the groove surfaces exhibited better erosion performance at 30° injection angle. In order to determine the effect of the groove dimensions on the erosion resistance, regression analysis of orthogonal multinomials was also performed under a certain erosion condition, and the regression equation between the erosion rate and groove distance, width, and height was established.

  5. Sands at Gusev Crater, Mars

    Science.gov (United States)

    Cabrol, Nathalie A.; Herkenhoff, Kenneth E.; Knoll, Andrew H.; Farmer, Jack D.; Arvidson, Raymond E.; Grin, E.A.; Li, Ron; Fenton, Lori; Cohen, B.; Bell, J.F.; Yingst, R. Aileen

    2014-01-01

    Processes, environments, and the energy associated with the transport and deposition of sand at Gusev Crater are characterized at the microscopic scale through the comparison of statistical moments for particle size and shape distributions. Bivariate and factor analyses define distinct textural groups at 51 sites along the traverse completed by the Spirit rover as it crossed the plains and went into the Columbia Hills. Fine-to-medium sand is ubiquitous in ripples and wind drifts. Most distributions show excess fine material, consistent with a predominance of wind erosion over the last 3.8 billion years. Negative skewness at West Valley is explained by the removal of fine sand during active erosion, or alternatively, by excess accumulation of coarse sand from a local source. The coarse to very coarse sand particles of ripple armors in the basaltic plains have a unique combination of size and shape. Their distribution display significant changes in their statistical moments within the ~400 m that separate the Columbia Memorial Station from Bonneville Crater. Results are consistent with aeolian and/or impact deposition, while the elongated and rounded shape of the grains forming the ripples, as well as their direction of origin, could point to Ma'adim Vallis as a possible source. For smaller particles on the traverse, our findings confirm that aeolian processes have dominated over impact and other processes to produce sands with the observed size and shape patterns across a spectrum of geologic (e.g., ripples and plains soils) and aerographic settings (e.g., wind shadows).

  6. Erosion Pressure on the Danish Coasts

    DEFF Research Database (Denmark)

    Sørensen, Carlo Sass; Sørensen, Per; Kroon, Aart;

    by the ocean, coastal erosion issues become increasingly more important to the human values at risk. Along many Danish coastlines, hard structures already act as coastal protection in the form of groins, breakwaters, revetments etc. These eroding coasts however still lack sand and where the public, in general...

  7. Optimization design of performance test of cyclone separator sand sampler based on numerical simulation and wind erosion tunnel experiment%基于数值模拟与风洞试验的旋风分离式集沙仪优化设计

    Institute of Scientific and Technical Information of China (English)

    黄炎; 赵满全

    2015-01-01

    为了解风蚀风沙运动规律,提高旋风分离式集沙仪集沙效率。该文在Fluent 平台中建立了旋风分离式集沙仪有限元模型,基于RNG k-ε模型和雷诺应力模型对旋风分离式集沙仪进行数值分析,并对3种不同结构参数旋风分离式集沙仪进行风洞试验。通过有限元分析,得到了其内部气相运动规律,观察到集沙仪升气管附近气流强度较大,其内部有“短路流”存在。同时,通过对3种不同结构参数旋风分离式集沙仪进行数值模拟,得到结构参数为:筒体直径50 mm;锥体段高度125 mm 的旋风分离式集沙仪集沙盒底部具有较小的湍动能和向上轴向速度,其大小分别为0.99 m2/s2和1.48 m/s。另外,分别对3种不同结构参数旋风分离式集沙仪进行风洞试验,得到了改变筒体直径与锥体段高度引起集沙盒底部湍流强度的改变,从而对集沙效率有一定影响,相比较筒体直径而言,锥体段高度对集沙效率影响更明显;集沙盒底部湍动能和向上轴向速度较小的集沙仪,集沙效率较高,具有良好的分离性能。结合数值模拟和风洞试验确定了集沙盒底部湍动能、向上轴向速度为目标函数,根据目标函数,优化设计了集沙盒直管的长度,确定了集沙盒直管长16 mm的旋风分离式集沙仪可以降低集沙盒底部湍动能和向上轴向速度,理论上可以提高旋风分离式集沙仪集沙效率。该文研究结果可为进一步提高旋风分离式集沙仪性能提供依据。%For the purpose of knowing the motion law of sand erosion and improving the efficiency of cyclone separation sand sampler, the finite element model of cyclone separation sand sampler is built by using the software of Fluent. There is a two-phase movement inside the cyclone separation sand sampler, including air and soil particles. The cyclone separation sand sampler mainly separates the soil

  8. Investigation of Laminar Boundary Layer on Airfoil

    OpenAIRE

    林, 秀千人; 佐々木, 壮一; 児玉, 好雄; 清水, 光昭

    1999-01-01

    The development of the laminar boundary layer on the NACA symmetrical airfoils and the separation of it are simulated by using the boundary layer theory and discrete vortex method. The arrangement of the discrete vortices on the airfoil affects on the separation position very much because the separation is sensitive to the velocity gradient of the main flow. It needs the very small increment 1/500 in boundary layer simulation to get the exact position of the separation. The simulation of both...

  9. A 30000 yr record of erosion rates from cosmogenic 10Be in middle European river terraces

    NARCIS (Netherlands)

    Schaller, M.; Blanckenburg, von F.; Veldkamp, A.; Tebbens, L.A.; Hovius, N.; Kubik, P.W.

    2002-01-01

    Cosmogenic 10Be in river-borne quartz sand records a time-integrated erosion rate representative of an entire drainage basin. When sequestered in a terrace of known age, paleo-erosion rates may be recovered from the nuclide content of the terrace material. Paleo-erosion rates between 30 and 80 mm/ky

  10. Design and Validation of a Force Measurement System for the Analysis of Airfoil Lift and Drag Characteristics

    OpenAIRE

    Manning, Niall

    2010-01-01

    One of the aims of this research was to reduce the flow separation and therefore the pressure drag generated by a wing section, through the adding of surface modifications. The modifications consisted of roughening the surface of polystyrene airfoils using a sand blasting technique, which resulted in a dimpled surface. This idea originated from the design of a golf ball, as the dimples are known to delay flow separation which allows the ball to travel further. In relation to wing design, ther...

  11. The water erosion processes in the retreat erosive of cliff on soft rocks in the province of Cadiz (Spain); Los procesos de erosion hidrica en el retroceso erosivo de acantilados sobre rocas blandas en la provincia de Cadiz

    Energy Technology Data Exchange (ETDEWEB)

    Rendon Aragon, J. J.; Gracia Prieto, F. J.; Rio Rodriguez, L. del

    2009-07-01

    The littoral cliffs on soft materials of the Atlantic Cadiz coast show an important activity of the fresh water erosion processes, sometimes even more significant than the marine erosion processes. The connection of the lower cliffs with sandy beaches favours aeolian sand invasion, which fills previous rills and reduces the water erosion intensity by increasing infiltration. Cliff retreat and rill erosion measurement by using erosion sticks has shown very variables values, most of them higher than the estimated error of the employed methods. This indicates the existence of other factors influencing the distribution of water erosion processes along these cliffs, which have to be studied through different techniques. (Author) 5 refs.

  12. Effect Of Sand Blasting On Soda Lime Glass Properties

    OpenAIRE

    Bousbaa, C.; Madjoubi, M. A.; Hamidouche, Z; N. BOUAOUADJA

    2003-01-01

    The present work is based on a simulation in laboratory of the erosion of a soda lime glass caused by sand blasting during sandstorms. It deals with the effects of sand blasting duration (from 0 to 60 min) and impact angle (from 0 to 90°) on the material and its properties. The principal erosion characteristics and properties of the material studied are the mass loss, the erosion rate, the surface roughness, the optical transmission and the mechanical strength. The influence of the optical tr...

  13. AirfoilPrep.py Documentation: Release 0.1.0

    Energy Technology Data Exchange (ETDEWEB)

    Ning, S. A. [National Renewable Energy Lab. (NREL), Golden, CO (United States)

    2013-09-01

    AirfoilPrep.py provides functionality to preprocess aerodynamic airfoil data. Essentially, the module is an object oriented version of the AirfoilPrep spreadsheet with additional functionality and is written in the Python language. It allows the user to read in two-dimensional aerodynamic airfoil data, apply three-dimensional rotation corrections for wind turbine applications, and extend the datato very large angles of attack. This document discusses installation, usage, and documentation of the module.

  14. Analysis of non-symmetrical flapping airfoils

    Institute of Scientific and Technical Information of China (English)

    W.B.Tay; K.B.Lim

    2009-01-01

    Simulations have been done to assess the lift, thrust and propulsive efficiency of different types of nonsymmetrical airfoils under different flapping configurations. The variables involved are reduced frequency, Strouhal number, pitch amplitude and phase angle. In order to analyze the variables more efficiently, the design of experiments using the response surface methodology is applied. Results show that both the variables and shape of the airfoil have a profound effect on the lift, thrust, and efficiency. By using nonsymmetrical airfoils, average lift coefficient as high as 2.23 can be obtained. The average thrust coefficient and efficiency also reach high values of 2.53 and 0.6 I, respectively. The lift production is highly dependent on the airfoil's shape while thrust production is influenced more heavily by the variables. Efficiency falls somewhere in between. Two-factor interactions are found to exist among the variables. This shows that it is not sufficient to analyze each variable individually. Vorticity diagrams are analyzed to explain the results obtained. Overall, the S1020 airfoil is able to provide relatively good efficiency and at the same time generate high thrust and lift force. These results aid in the design of a better omithopter's wing.

  15. Turbine airfoil fabricated from tapered extrusions

    Science.gov (United States)

    Marra, John J

    2013-07-16

    An airfoil (30) and fabrication process for turbine blades with cooling channels (26). Tapered tubes (32A-32D) are bonded together in a parallel sequence, forming a leading edge (21), a trailing edge (22), and pressure and suction side walls (23, 24) connected by internal ribs (25). The tapered tubes may be extruded without camber to simplify the extrusion process, then bonded along matching surfaces (34), forming a non-cambered airfoil (28), which may be cambered in a hot forming process and cut (48) to length. The tubes may have tapered walls that are thinner at the blade tip (T1) than at the base (T2), reducing mass. A cap (50) may be attached to the blade tip. A mounting lug (58) may be forged (60) on the airfoil base and then machined, completing the blade for mounting in a turbine rotor disk.

  16. Transonic flow theory of airfoils and wings

    Energy Technology Data Exchange (ETDEWEB)

    Garabedian, P R

    1976-01-01

    Supercritical wing technology is expected to have a significant influence on the next generation of commercial aircraft. Computational fluid dynamics is playing a central role in the development of new supercritical wing sections. One of the principal tools is a fast and reliable code that simulates two-dimensional wind tunnel data for transonic flow at high Reynolds numbers. This is used widely by industry to assess drag creep and drag rise. Codes for the design of shockless airfoils by the hodograph method have not been so well received because they usually require a lot of trial and error. However, a more advanced mathematical approach makes it possible to assign the pressure as a function of the arc length and then obtain a shockless airfoil that nearly achieves the given distribution of pressure. This tool should enable engineers to design families of transonic airfoils more easily both for airplane wings and for compressor blades in cascade.

  17. Numerical simulation of the erosion in the 90° elbow

    Science.gov (United States)

    Deng, Yunzhong; Liu, Yinhe; Chen, Jianying; Zhang, Yongjian

    2013-07-01

    In the process of natural gas transportation, cement production and coal-fired power, the gas-solid two-phase flow exists widely in pipelines. The existence of solid particles may cause the erosion of the pipeline, especially in the elbow of the pipeline. Equations used to predict erosion rate are usually obtained from well-controlled experimental tests for solid particles carried in a gas or liquid flow. The particle impact speed and impact angle affect the erosion process and are two major parameters in most erosion equations. In this paper, the erosion of 90° elbow was studied by using Computational Fluid Dynamics (CFD), Discrete Particle Model (DPM) and erosion equations. The maximum erosion rate and the erosion position were reported. Particle size does not influence the erosion rate when particle size is bigger than a certain degree. When the mass ratio of sand loading to fluid is less than 1, erosion ratio is proportional to the loading mass. The erosion rate is lower for larger radius elbow, and the erosion rate is greatly declined by using the plugged tee instead of an elbow.

  18. Blowing Circulation Control on a Seaplane Airfoil

    Science.gov (United States)

    Guo, B. D.; Liu, P. Q.; Qu, Q. L.

    2011-09-01

    RANS simulations are presented for blowing circulation control on a seaplane airfoil. Realizable k-epsilon turbulent model and pressure-based coupled algorithm with second-order discretization were adopted to simulate the compressible flow. Both clear and simple flap configuration were simulated with blowing momentum coefficient Cμ = 0, 0.15 and 0.30. The results show that blowing near the airfoil trailing edge could enhance the Coanda effect, delay the flow separation, and increase the lift coefficient dramatically. The blowing circulation control is promising to apply to taking off and landing of an amphibious aircraft or seaplane.

  19. New airfoil sections for straight bladed turbine

    International Nuclear Information System (INIS)

    A theoretical investigation of aerodynamic performance for vertical axis Darrieus wind turbine with new airfoils sections is carried out. The blade section aerodynamics characteristics are determined from turbomachines cascade model. The model is also adapted to the vertical Darrieus turbine for the performance prediction of the machine. In order to choose appropriate value of zero-lift-drag coefficient in calculation, an analytical expression is introduced as function of chord-radius ratio and Reynolds numbers. New airfoils sections are proposed and analyzed for straight-bladed turbine

  20. Inviscid double wake model for stalled airfoils

    DEFF Research Database (Denmark)

    Marion, Lucas; Ramos García, Néstor; Sørensen, Jens Nørkær

    2014-01-01

    An inviscid double wake model based on a steady two-dimensional panel method has been developed to predict aerodynamic loads of wind turbine airfoils in the deep stall region. The separated flow is modelled using two constant vorticity sheets which are released at the trailing edge and at the sep......An inviscid double wake model based on a steady two-dimensional panel method has been developed to predict aerodynamic loads of wind turbine airfoils in the deep stall region. The separated flow is modelled using two constant vorticity sheets which are released at the trailing edge...

  1. Synthesis, characterization and application of a novel chemical sand-fixing agent-poly(aspartic acid) and its composites

    Energy Technology Data Exchange (ETDEWEB)

    Yang Jun [Beijing Key Laboratory of Bioprocess, Beijing University of Chemical Technology, Beijing 100029 (China); Wang Fang [Beijing Key Laboratory of Bioprocess, Beijing University of Chemical Technology, Beijing 100029 (China); Fang Li [Beijing Key Laboratory of Bioprocess, Beijing University of Chemical Technology, Beijing 100029 (China); Tan Tianwei [Beijing Key Laboratory of Bioprocess, Beijing University of Chemical Technology, Beijing 100029 (China)]. E-mail: twtan@mail.buct.edu.cn

    2007-09-15

    A novel sand-fixing agent-poly(aspartic acid) and its composites were synthesized to improve sand particles compressive strength and anti-wind erosion properties. The relationship between the concentration of sand-fixing agent and the sand-fixing properties was studied by three kinds of aging tests. Some composites were choose to improve the sand-fixing property and the composition of 40% xanthan gum and 60% ethyl cellulose were chosen to compare sand-fixing property with lignosulfonate. The results showed that the sand-fixing and water-retaining properties of xanthan gum and ethyl cellulose composites were better than that of lignosulfonate. The biodegradability experiment showed that the PASP and its composites were environment-friendly products and the field test showed that the PASP composites could improve wind erosion disturbance. - A novel biodegradability polymer significantly improved sand particles' compressive strength and anti-wind erosion properties.

  2. Synthesis, characterization and application of a novel chemical sand-fixing agent-poly(aspartic acid) and its composites

    International Nuclear Information System (INIS)

    A novel sand-fixing agent-poly(aspartic acid) and its composites were synthesized to improve sand particles compressive strength and anti-wind erosion properties. The relationship between the concentration of sand-fixing agent and the sand-fixing properties was studied by three kinds of aging tests. Some composites were choose to improve the sand-fixing property and the composition of 40% xanthan gum and 60% ethyl cellulose were chosen to compare sand-fixing property with lignosulfonate. The results showed that the sand-fixing and water-retaining properties of xanthan gum and ethyl cellulose composites were better than that of lignosulfonate. The biodegradability experiment showed that the PASP and its composites were environment-friendly products and the field test showed that the PASP composites could improve wind erosion disturbance. - A novel biodegradability polymer significantly improved sand particles' compressive strength and anti-wind erosion properties

  3. Integrated airfoil and blade design method for large wind turbines

    DEFF Research Database (Denmark)

    Zhu, Wei Jun; Shen, Wen Zhong; Sørensen, Jens Nørkær

    2014-01-01

    and a free-stream Mach number of 0.25 near the tip. Results show that the new airfoils achieve a high power coefficient in a wide range of angles of attack (AOA) and are extremely insensitive to surface roughness. Finally, a full blade analysis using computational fluid dynamics (CFD) and blade element......This paper presents an integrated method for designing airfoil families of large wind turbine blades. For a given rotor diameter and a tip speed ratio, optimal airfoils are designed based on the local speed ratios. To achieve a high power performance at low cost, the airfoils are designed...... with the objectives of high Cp and small chord length. When the airfoils are obtained, the optimum flow angle and rotor solidity are calculated which forms the basic input to the blade design. The new airfoils are designed based on a previous in-house designed airfoil family which was optimized at a Reynolds number...

  4. A Comparative Study on Sand Transport Modeling for Horizontal Multiphase Pipeline

    OpenAIRE

    Kan Wai Choong; Lim Pei Wen; Lim Lay Tiong; Francis Anosike; Mohd Amin Shoushtari; Ismail bin Mohd Saaid

    2014-01-01

    Presence of sand causes adverse effects on hydrocarbon production, pipeline erosion and problems at wellbore. If the problems persist, production may be stopped and delayed. This imposes workover cost. Hence, operating expenses increase and revenue reduces. There is no explicit calculation algorithm for sand transportation modeling readily available in flow simulators. Therefore, this study aims to develop an Excel-based spreadsheet on sand transportation to predict sand critical velocity and...

  5. Mapping erosion from space

    OpenAIRE

    Vrieling, A

    2007-01-01

    Soil erosion by water is the most important land degradation problem worldwide. Spatial information on erosion is required for defining effective soil and water conservation strategies. Satellite remote sensing can provide relevant input to regional erosion assessment. This thesis comprises a review on how satellite data have been used previously for evaluating water erosion. Options include erosion detection and the assessment of controlling factors such as topography, soil, and vegetation. ...

  6. Causal mechanisms in airfoil-circulation formation

    Science.gov (United States)

    Zhu, J. Y.; Liu, T. S.; Liu, L. Q.; Zou, S. F.; Wu, J. Z.

    2015-12-01

    In this paper, we trace the dynamic origin, rather than any kinematic interpretations, of lift in two-dimensional flow to the physical root of airfoil circulation. We show that the key causal process is the vorticity creation by tangent pressure gradient at the airfoil surface via no-slip condition, of which the theoretical basis has been given by Lighthill ["Introduction: Boundary layer theory," in Laminar Boundary Layers, edited by L. Rosenhead (Clarendon Press, 1963), pp. 46-113], which we further elaborate. This mechanism can be clearly revealed in terms of vorticity formulation but is hidden in conventional momentum formulation, and hence has long been missing in the history of one's efforts to understand lift. By a careful numerical simulation of the flow around a NACA-0012 airfoil, and using both Eulerian and Lagrangian descriptions, we illustrate the detailed transient process by which the airfoil gains its circulation and demonstrate the dominating role of relevant dynamical causal mechanisms at the boundary. In so doing, we find that the various statements for the establishment of Kutta condition in steady inviscid flow actually correspond to a sequence of events in unsteady viscous flow.

  7. Solution of internal erosion equations by asymptotic expansion

    Directory of Open Access Journals (Sweden)

    Dubujet P.

    2012-07-01

    Full Text Available One dimensional coupled soil internal erosion and consolidation equations are considered in this work for the special case of well determined sand and clay mixtures with a small proportion of clay phase. An enhanced modelling of the effect of erosion on elastic soil behavior was introduced through damage mechanics concepts. A modified erosion law was proposed. The erosion phenomenon taking place inside the soil was shown to act like a perturbation affecting the classical soil consolidation equation. This interpretation has enabled considering an asymptotic expansion of the coupled erosion consolidation equations in terms of a perturbation parameter linked to the maximum expected internal erosion. A robust analytical solution was obtained via direct integration of equations at order zero and an adequate finite difference scheme that was applied at order one.

  8. Optimization design of airfoil profiles based on the noise of wind turbines

    DEFF Research Database (Denmark)

    Chen, Jin; Cheng, Jiangtao; Shen, Wenzhong;

    2012-01-01

    Based on design theory of airfoil profiles and airfoil self-noise prediction model, a new method with the target of the airfoil average efficiency-noise ratio of design ranges for angle of attack had been developed for designing wind turbine airfoils. The airfoil design method was optimized for a...

  9. Industrial sand and gravel

    Science.gov (United States)

    Dolley, T.P.

    2013-01-01

    Domestic production of industrial sand and gravel in 2012 was about 49.5 Mt (55 million st), increasing 13 percent compared with that of 2011. Some important end uses for industrial sand and gravel include abrasives, filtration, foundry, glassmaking, hydraulic fracturing sand (frac sand) and silicon metal applications.

  10. Erosion and flow of hydrophobic granular materials

    Science.gov (United States)

    Utter, Brian; Benns, Thomas; Foltz, Benjamin; Mahler, Joseph

    2015-03-01

    We experimentally investigate submerged granular flows of hydrophobic and hydrophilic grains both in a rotating drum geometry and under erosion by a surface water flow. While slurry and suspension flows are common in nature and industry, effects of surface chemistry on flow behavior have received relatively little attention. In the rotating drum, we use varying concentrations of hydrophobic and hydrophilic grains of sand submerged in water rotated at a constant angular velocity. Sequential images of the resulting avalanches are taken and analyzed. High concentrations of hydrophobic grains result in an effectively cohesive interaction between the grains forming aggregates, with aggregate size and repose angle increasing with hydrophobic concentration. However, the formation and nature of the aggregates depends significantly on the presence of air in the system. We present results from a related experiment on erosion by a surface water flow designed to characterize the effects of heterogeneous granular surfaces on channelization and erosion.

  11. Reducing Erosion and Runoff

    OpenAIRE

    Relf, Diane

    2009-01-01

    By caring for and improving your soil, you will help it absorb water more readily, reducing runoff and erosion as well as improving plant health. This publication gives the homeowner tips to help prevent runoff and erosion on their property.

  12. New airfoils for small horizontal axis wind turbines

    Energy Technology Data Exchange (ETDEWEB)

    Giguere, P.; Selig, M.S. [Univ. of Illinois, Urbana, IL (United States)

    1997-12-31

    In a continuing effort to enhance the performance of small energy systems, one root airfoil and three primary airfoils were specifically designed for small horizontal axis wind turbines. These airfoils are intended primarily for 1-10 kW variable-speed wind turbines for both conventional (tapered/twisted) or pultruded blades. The four airfoils were wind-tunnel tested at Reynolds numbers between 100,000 and 500,000. Tests with simulated leading-edge roughness were also conducted. The results indicate that small variable-speed wind turbines should benefit from the use of the new airfoils which provide enhanced lift-to-drag ratio performance as compared with previously existing airfoils.

  13. Turbine airfoil with laterally extending snubber having internal cooling system

    Energy Technology Data Exchange (ETDEWEB)

    Scribner, Carmen Andrew; Messmann, Stephen John; Marsh, Jan H.

    2016-09-06

    A turbine airfoil usable in a turbine engine and having at least one snubber with a snubber cooling system positioned therein and in communication with an airfoil cooling system is disclosed. The snubber may extend from the outer housing of the airfoil toward an adjacent turbine airfoil positioned within a row of airfoils. The snubber cooling system may include an inner cooling channel separated from an outer cooling channel by an inner wall. The inner wall may include a plurality of impingement cooling orifices that direct impingement fluid against an outer wall defining the outer cooling channel. In one embodiment, the cooling fluids may be exhausted from the snubber, and in another embodiment, the cooling fluids may be returned to the airfoil cooling system. Flow guides may be positioned in the outer cooling channel, which may reduce cross-flow by the impingement orifices, thereby increasing effectiveness.

  14. The effect of a cavity on airfoil tones

    Science.gov (United States)

    Schumacher, Karn L.; Doolan, Con J.; Kelso, Richard M.

    2014-03-01

    The presence of a cavity in the pressure surface of an airfoil has been found via experiment to play a role in the production of airfoil tones, which was attributed to the presence of an acoustic feedback loop. The cavity length was sufficiently small that cavity oscillation modes did not occur for most of the investigated chord-based Reynolds number range of 70,000-320,000. The airfoil tonal noise frequencies varied as the position of the cavity was moved along a parallel section at the airfoil's maximum thickness: specifically, for a given velocity, the frequency spacing of the tones was inversely proportional to the geometric distance between the cavity and the trailing edge. The boundary layer instability waves considered responsible for the airfoil tones were only detected downstream of the cavity. This may be the first experimental verification of these aspects of the feedback loop model for airfoil tonal noise.

  15. Redistribution of soil biota by rainfall erosion

    Science.gov (United States)

    Baxter, Craig; Rowan, John; McKenzie, Blair; Neilson, Roy

    2013-04-01

    Soil is central to the provision of multiple ecosystem services that sustain life through a myriad of chemical, physical and biological processes. One of the greatest threats to soil is erosion, a natural process accelerated by human activities. Elevated erosion rates are common in agro-ecosystems causing both direct physical impacts (e.g. soil loss), and indirect biogeochemical consequences, which ultimately leads to impaired ecosystem functioning. The consequences of erosion on soil biota have hitherto been ignored, yet biota have fundamental roles in the provision of soil ecosystem services. To our knowledge few studies have addressed the gap between erosion and impacts on soil biota. Here we use soil nematodes as a model organism for assessing erosion impacts on soil (micro) fauna in temperate agro-ecosystems. Soil nematodes are ubiquitous, abundant, are represented at all levels in soil food webs and can be categorised into a range of trophic or functional groups. To quantify transport of nematodes and gain a better understanding of erosive mechanisms responsible, we measured their export from small erosion plots (0.0625m2) under a fixed-intensity design rainstorm (6mm min-1 duration: 3 min) over six slope angles (4° - 24°) and three soil texture classes (sandy silt, silty sand, silt). Runoff and eroded sediment were collected for each plot (four replicate runs), and a suite of biological and physico-chemical parameters measured. Results confirmed that, similar to soil particles, nematodes were exported at rates influenced by slope angle and soil texture. These experiments, linked with field and catchment-scale equivalents, are designed to elucidate the links between soil erosion and provision of ecosystem services and to inform biodiversity-sensitive soil and water conservation practices.

  16. Erosion-corrosion

    International Nuclear Information System (INIS)

    A literature study on erosion-corrosion of pipings in the nuclear industry was performed. Occurred incidents are reviewed, and the mechanism driving the erosion-corrosion is described. Factors that influence the effect in negative or positive direction are treated, as well as programs for control and inspection. Finally, examples of failures from databases on erosion-corrosion are given in an attachment

  17. Emergency wind erosion control

    Science.gov (United States)

    February through May is the critical time for wind erosion in Kansas, but wind erosion can happen any time when high winds occur on smooth, wide fields with low vegetation and poor soil structure. The most effective wind erosion control is to ensure a protective cover of residue or growing crop thro...

  18. BIFURCATIONS OF AIRFOIL IN INCOMPRESSIBLE FLOW

    Institute of Scientific and Technical Information of China (English)

    LiuFei; YangYiren

    2005-01-01

    Bifurcations of an airfoil with nonlinear pitching stiffness in incompressible flow are investigated. The pitching spring is regarded as a spring with cubic stiffness. The motion equations of the airfoil are written as the four dimensional one order differential equations. Taking air speed and the linear part of pitching stiffness as the parameters, the analytic solutions of the critical boundaries of pitchfork bifurcations and Hopf bifurcations are obtained in 2 dimensional parameter plane. The stabilities of the equilibrium points and the limit cycles in different regions of 2 dimensional parameter plane are analyzed. By means of harmonic balance method, the approximate critical boundaries of 2-multiple semi-stable limit cycle bifurcations are obtained, and the bifurcation points of supercritical or subcritical Hopf bifurcation are found. Some numerical simulation results are given.

  19. Turbine airfoil with ambient cooling system

    Energy Technology Data Exchange (ETDEWEB)

    Campbell, Jr, Christian X.; Marra, John J.; Marsh, Jan H.

    2016-06-07

    A turbine airfoil usable in a turbine engine and having at least one ambient air cooling system is disclosed. At least a portion of the cooling system may include one or more cooling channels configured to receive ambient air at about atmospheric pressure. The ambient air cooling system may have a tip static pressure to ambient pressure ratio of at least 0.5, and in at least one embodiment, may include a tip static pressure to ambient pressure ratio of between about 0.5 and about 3.0. The cooling system may also be configured such that an under root slot chamber in the root is large to minimize supply air velocity. One or more cooling channels of the ambient air cooling system may terminate at an outlet at the tip such that the outlet is aligned with inner surfaces forming the at least one cooling channel in the airfoil to facilitate high mass flow.

  20. EUDP Project: Low Noise Airfoil - Final Report

    DEFF Research Database (Denmark)

    This document summarizes the scientific results achieved during the EUDP-funded project `Low-Noise Airfoil'. The goals of this project are, on one side to develop a measurement technique that permits the evaluation of trailing edge noise in a classical aerodynamic wind tunnel, and on the other side....... In particular, the so-called TNO trailing edge noise model could be significantly improved by introducing turbulence anisotropy in its formulation, as well as the influence of the boundary layer mean pressure gradient. This two characteristics are inherent to airfoil flows but were neglected in the original......-mounted microphones in order to evaluate far-field noise emission using additional theoretical results has been validated. This technique presents the advantage that it can easily be used in a classical aerodynamic wind tunnel and does not require the use of an anechoic facility. It was developed as a substitute...

  1. Sand Dunes Fixation in Baiji District, Iraq

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    This study was carried out at Sand Dunes Stabilization Researches Station in Baiji district (230 ln north of Baghdad, Iraq) to evaluate the effects of local soil conditioners manufactured from oil derivatives and plant residuals on sand dunes fixation as the first step for sand dunes stabilization. The results indicate that the fuel oil has the first place in improving wind erosion parameters in the study area, such as increasing mean weight diameter, dry aggregates percentage, the needed time for complete disaggregation by dry sieving, and decreasing the disaggregation rates. Bitumen emulsion occupies the second place, while the plant residuals occupies the third place and has slight effects on the studied parameters. Effects of conditioners on natural vegetation cover are negative in oil derivatives treatments,while positive in plants residuals treatments.

  2. Transonic airfoil and axial flow rotary machine

    Energy Technology Data Exchange (ETDEWEB)

    Nagai, Naonori; Iwatani, Junji

    2015-09-01

    Sectional profiles close to a tip 124 and a part between a midportion 125 and a hub 123 are shifted to the upstream of an operating fluid flow in a sweep direction. Accordingly, an S shape is formed in which the tip 124 and the part between the midportion 125 and the hub 123 protrude. As a result, it is possible reduce various losses due to shook, waves, thereby forming a transonic airfoil having an excellent aerodynamic characteristic.

  3. Design of the LRP airfoil series using 2D CFD

    DEFF Research Database (Denmark)

    Zahle, Frederik; Bak, Christian; Sørensen, Niels N.;

    2014-01-01

    This paper describes the design and wind tunnel testing of a high-Reynolds number, high lift airfoil series designed for wind turbines. The airfoils were designed using direct gradient- based numerical multi-point optimization based on a Bezier parameterization of the shape, coupled to the 2D...... Navier-Stokes flow solver EllipSys2D. The resulting airfoils, the LRP2-30 and LRP2-36, achieve both higher operational lift coefficients and higher lift to drag ratios compared to the equivalent FFA-W3 airfoils....

  4. CFD study of thick flatback airfoils using OpenFOAM

    OpenAIRE

    Milián Sanz, José María

    2010-01-01

    New airfoil designs are created in order to improve both the structural and aerodynamic properties of a wind turbine blade, one example of these are flatback airfoils. Furthermore, a new CFD programme exists in order to study the behavior of the flow around an airfoil, OpenFOAM. The flow around these new airfoils using OpenFOAM is studied in the present thesis. It is used the turbulence model k-! SST for fully turbulent boundary layer and free transition at the boundary layer, modeled with th...

  5. Research on improved design of airfoil profiles based on the continuity of airfoil surface curvature of wind turbines

    DEFF Research Database (Denmark)

    Chen, Jin; Cheng, Jiangtao; Shen, Wenzhong;

    2013-01-01

    Aerodynamic of airfoil performance is closely related to the continuity of its surface curvature, and airfoil profiles with a better aerodynamic performance plays an important role in the design of wind turbine. The surface curvature distribution along the chord direction and pressure distribution...... of curvature distribution. And the performances of new airfoil are compared with the original one to validate, and results show an improvement, validated the advantage of the improved design method....

  6. Rainfall Erosivity in Europe

    DEFF Research Database (Denmark)

    Panagos, Panos; Ballabio, Cristiano; Borrelli, Pasquale;

    2015-01-01

    Rainfall is one the main drivers of soil erosion. The erosive force of rainfall is expressed as rainfall erosivity. Rainfall erosivity considers the rainfall amount and intensity, and is most commonly expressed as the Rfactor in the USLE model and its revised version, RUSLE. At national...... and continental levels, the scarce availability of data obliges soil erosion modellers to estimate this factor based on rainfall data with only low temporal resolution (daily, monthly, annual averages). The purpose of this study is to assess rainfall erosivity in Europe in the form of the RUSLE R-factor, based....... Gaussian Process Regression (GPR) has been used to interpolate the R-factor station values to a European rainfall erosivity map at 1 km resolution. The covariates used for the R-factor interpolation were climatic data (total precipitation, seasonal precipitation, precipitation of driest/wettest months...

  7. Wind erosion control of soils using polymeric materials

    Directory of Open Access Journals (Sweden)

    Mohammad Movahedan

    2012-07-01

    Full Text Available Wind erosion of soils is one of the most important problems in environment and agriculture which could affects several fields. Agricultural lands, water reservoires, irrigation canals, drains and etc. may be affected by wind erosion and suspended particles. As a result wind erosion control needs attention in arid and semi-arid regions. In recent years, some polymeric materials have been used for improvement of structural stability, increasing aggregate stability and soil stabilization, though kind of polymer, quantity of polymer, field efficiency and durability and environmental impacts are some important parameters which should be taken into consideration. In this study, a Polyvinil Acetate-based polymer was used to treat different soils. Then polymer-added soil samples were investigated experimentally in a wind tunnel to verify the effecte of polymer on wind erosion control of the soils and the results were compared with water treated soil samples. The results of wind tunnel experiments with a maximum 26 m/s wind velocity showed that there was a significat difference between the erosion of polymer treated and water treated soil samples. Application of 25g/m2 polymer to Aeolian sands reduced the erosion of Aeolian sands samples to zero related to water treated samples. For silty and calyey soils treated by polymer, the wind erosion reduced minimum 90% in relation to water treated samples.

  8. When erosion ruins the chronology

    Science.gov (United States)

    Wolters, Steffen; Enters, Dirk; Blume, Katharina; Lücke, Andreas

    2016-04-01

    Human land-use has considerably shaped the landscape of north-western Germany over the past millennia. Deforestation and agriculture created a predominantly open scenery preserved until today with only a few remnants of former landscape elements such as woodlands, peat bogs, heath lands and lakes. Here we present a multi-proxy approach including sedimentological and geochemical parameters (e. g. element concentrations and stable isotopes) as well as biological proxies (pollen, macro fossils and diatoms) combined with an archaeological site analysis to investigate the effects of prehistoric land-use on lake systems and their catchment areas with a special focus on changes of the water quality, e. g. eutrophication and acidification and its natural regeneration during phases of weaker land-use impact. The study reveals a millenia-long history of erosion processes caused by successive selective woodland clearances starting in Neolithic Times. The geochemical evidence of soil erosion is recorded by distinct peaks of the terrigenic elements K and Ti. However, due to (1) the low sensitivy of the XRF scanner for Si and (2) the prevalence of diatom related biogenic silicon XRF-scanning of highly organic lake sediments fails to reflect the actual sand input caused by erosion. Particularly single quartz grains are not detected in the organic sediment matrix. Therefore we make successful use of mineral grain analysis which previously has only been applied to record aeolian input in bogs. K and Ti concentrations are not correlated with the content of mineral grains which suggest two different erosion processes. Our efforts to construct robust age-depth relationships based on AMS 14C-dates of terrestrial plant macrofossils reveal a specific dating issue of northwest German lakes. Especially in younger sediments we observe 14C-dates which are on the one hand too old and on the other hand among themselves roughly contemporaneous. We explain this feature with the extensive bog

  9. Erosion due to high flow velocities: A description of relevant processes

    NARCIS (Netherlands)

    Bisschop, F.; Visser, P.J.; Van Rhee, C.; Verhagen, H.J.

    2010-01-01

    Convential models for the erosion of non-cohesive sediments overestimate the erosion rate induced by high flow velocities. These high flow velocities occur, for instance, in breaching of embankments or dunes (flow velocities up to 10 m/s) or in jetting sand with a trailing suction hopper dredger (30

  10. Erosion wear behaviour and mechanism of abradable seal coating

    Institute of Scientific and Technical Information of China (English)

    冉丽萍

    2002-01-01

    The erosion wear behaviour and mechanism of several middle temperature seal coatings were investigated by a CMS-100 self-made vacuum sand erosion machine. The results show that the relationship between the erosion mass loss and the erosion time is linear, the coatings hold a maximum erosion rate at 60° impact angle, and the relationship between the erosion rate and the impact speed is an exponential function. The speed exponent increases with the increase of the impact angle. At 90° impact, indentations and extruded lips were generated on the coating surface subjected to impact. With repetitive impact by the abrasive particles, the extruded lips were work-hardened and peeled off, while flattened metal phase grains were impacted repeatedly, loosed and debonded. At 30° impact, the erosion wear of the coating is characterized by micro-cutting, plowing and tunneling via pores and non-metal phase. The model of the erosion mechanism is advanced on the basis of the above-mentioned erosion wear behaviour.

  11. Lateral erosion in an experimental bedrock channel: The influence of bed roughness on erosion by bed load impacts

    Science.gov (United States)

    Fuller, Theodore K.; Gran, Karen B.; Sklar, Leonard S.; Paola, Chris

    2016-05-01

    Physical experiments were conducted to evaluate the efficacy of bed load particle impacts as a mechanism of lateral bedrock erosion. In addition, we explored how changes in channel bed roughness, as would occur during development of an alluvial cover, influence rates of lateral erosion. Experimental channels were constructed to have erodible walls and a nonerodible bed using different mixtures of sand and cement. Bed roughness was varied along the length of the channel by embedding sediment particles of different size in the channel bed mixture. Lateral wall erosion from clear-water flow was negligible. Lateral erosion during periods in which bed load was supplied to the channel removed as much as 3% of the initial wetted cross-sectional area. The vertical distribution of erosion was limited to the base of the channel wall, producing channels with undercut banks. The addition of roughness elements to an otherwise smooth bed caused rates of lateral erosion to increase by as much as a factor of 7 during periods of bed load supply. However, a minimum roughness element diameter of approximately half the median bed load particle diameter was required before a substantial increase in erosion was observed. Beyond this minimum threshold size, further increases in the relative size of roughness elements did not substantially change the rate of wall erosion despite changes in total boundary shear stress. The deflection of saltating bed load particles into the channel wall by fixed roughness elements is hypothesized to be the driver of the observed increase in lateral erosion rates.

  12. Identification of dynamic properties of radial air-foil bearings

    NARCIS (Netherlands)

    Arora, V.; Hoogt, van der P.J.M.; Aarts, R.G.K.M.; Boer, de A.

    2010-01-01

    Air-foil bearings (AFBs) are self acting hydrodynamic bearings made from sheet metal foils comprised of at least two layers. The innermost ‘‘top foil’’ layer traps a gas pressure film that supports a load while the layer or layers underneath provide an elastic foundation. Air-foil bearings are curre

  13. Investigations of the transonic flow around oscillating airfoils

    NARCIS (Netherlands)

    Tijdeman, H.

    1977-01-01

    Exploratory wind-tunnel experiments in high-subsonic and transonic flow on a conventional airfoil with oscillating flap and a supercritical airfoil oscillating in pitch are described. In the analysis of the experimental results, emphasis is placed upon the typical aspects of transonic flow, namely t

  14. Extraction of airfoil data using PIV and pressure measurements

    DEFF Research Database (Denmark)

    Yang, Hua; Shen, Wen Zhong; Sørensen, Jens Nørkær;

    2011-01-01

    airfoil data are compared to 2D data from wind tunnel experiments and XFOIL computations. The comparison suggests that the rotor is subject to severe 3D effects originating from the geometry of the rotor, and explains why the Blade Element Momentum technique with 2D airfoil data over‐predicts the loading...

  15. Airfoil family design for large offshore wind turbine blades

    Science.gov (United States)

    Méndez, B.; Munduate, X.; San Miguel, U.

    2014-06-01

    Wind turbine blades size has scaled-up during last years due to wind turbine platform increase especially for offshore applications. The EOLIA project 2007-2010 (Spanish Goverment funded project) was focused on the design of large offshore wind turbines for deep waters. The project was managed by ACCIONA Energia and the wind turbine technology was designed by ACCIONA Windpower. The project included the design of a wind turbine airfoil family especially conceived for large offshore wind turbine blades, in the order of 5MW machine. Large offshore wind turbines suffer high extreme loads due to their size, in addition the lack of noise restrictions allow higher tip speeds. Consequently, the airfoils presented in this work are designed for high Reynolds numbers with the main goal of reducing blade loads and mantainig power production. The new airfoil family was designed in collaboration with CENER (Spanish National Renewable Energy Centre). The airfoil family was designed using a evolutionary algorithm based optimization tool with different objectives, both aerodynamic and structural, coupled with an airfoil geometry generation tool. Force coefficients of the designed airfoil were obtained using the panel code XFOIL in which the boundary layer/inviscid flow coupling is ineracted via surface transpiration model. The desing methodology includes a novel technique to define the objective functions based on normalizing the functions using weight parameters created from data of airfoils used as reference. Four airfoils have been designed, here three of them will be presented, with relative thickness of 18%, 21%, 25%, which have been verified with the in-house CFD code, Wind Multi Block WMB, and later validated with wind tunnel experiments. Some of the objectives for the designed airfoils concern the aerodynamic behavior (high efficiency and lift, high tangential coefficient, insensitivity to rough conditions, etc.), others concern the geometry (good for structural design

  16. Erosion Testing of Coatings for V-22 Aircraft Applications

    Directory of Open Access Journals (Sweden)

    G. Y. Richardson

    2003-01-01

    Full Text Available High-velocity (183 m/sec sand erosion tests in a wind tunnel were conducted to evaluate developmental coatings from three separate companies under funding by the Navy's phase I small business innovative research program. The purpose of the coatings was to address a particular problem the V-22 tilt-rotor aircraft (Osprey was having with regard to ingestion of sand particles by a titanium impeller that was associated with the aircraft's environmental control system. The three coatings that were deposited on titanium substrates and erosion-tested included (1 SixCy/DLC multilayers deposited by chemical vapor deposition (CVD; (2 WC/TaC/TiC processed by electrospark deposition; and (3 polymer ceramic mixtures applied by means of an aqueous synthesis. The erosion test results are presented; they provided the basis for assessing the suitability of some of these coatings for the intended application.

  17. How long does precipitation inhibit wind erosion in the Sahel?

    Science.gov (United States)

    Bergametti, G.; Rajot, J. L.; Pierre, C.; Bouet, C.; Marticorena, B.

    2016-06-01

    Simultaneous measurements of saltation, wind speed, and rainfall performed in Niger before, during, and after 18 rain events are used to investigate how rain events affect wind erosion in the Sahel. The results show that the inhibition of saltation is rapid but progressive after the beginning of a rain event. The decrease of sand transport during the rain event is better linked to the time elapsed from the beginning of the rain event rather than to the cumulative rainfall. In the Sahel, after a rain event, less than 12 h is necessary to almost fully restore the sand transport potential. Our results suggest that assuming that no sand transport and dust emission occur during the 12 h following the end of a rain event could be a reasonable alternative to existing parameterizations of the influence of soil moisture on the wind erosion threshold, at least for the Sahelian conditions.

  18. Multiple element airfoils optimized for maximum lift coefficient.

    Science.gov (United States)

    Ormsbee, A. I.; Chen, A. W.

    1972-01-01

    Optimum airfoils in the sense of maximum lift coefficient are obtained for incompressible fluid flow at large Reynolds number. The maximum lift coefficient is achieved by requiring that the turbulent skin friction be zero in the pressure rise region on the airfoil upper surface. Under this constraint, the pressure distribution is optimized. The optimum pressure distribution is a function of Reynolds number and the trailing edge velocity. Geometries of those airfoils which will generate these optimum pressure distributions are obtained using a direct-iterative method which is developed in this study. This method can be used to design airfoils consisting of any number of elements. Numerical examples of one- and two-element airfoils are given. The maximum lift coefficients obtained range from 2 to 2.5.

  19. Dental erosion - literature update

    OpenAIRE

    PICOS, ALINA M.; Andrea M. Chisnoiu; Jean F. Lasserre; Aurelia Spinei; Radu M.Chisnoiu; Andrei Picos

    2013-01-01

    Tooth wear is a complex, pluri-factorial process that must be taken into account in clinical practice. The main mechanisms typically related to dental wear are: abrasion, attrition, erosion and wear by fatigue. The dramatic increase in the frequency of erosive lesions, especially in younger age groups determined us to give a synthesis of the most recent scientific literature on the specific problem of erosion. Attention is drawn to the excessive consumption of acidic beverages in chi...

  20. Modeling of Polymer Erosion

    OpenAIRE

    Göpferich, Achim; Langer, Robert S.

    1993-01-01

    The erosion of bioerodible polymers depends on many factors including the polymer chain length, bond cleavage velocity, swellability, crystallinity, and water diffusivity in the polymer matrix. This multitude of parameters makes modeling of erosion difficult. Only a few models exist that describe morphological changes of polymers during erosion qualitatively. In the present approach the polymer matrix was represented as the sum of small individual polymer matrix parts. The factors that determ...

  1. Saliva and dental erosion

    OpenAIRE

    Marília Afonso Rabelo Buzalaf; Angélicas Reis Hannas; Melissa Thiemi Kato

    2012-01-01

    Dental erosion is a multifactorial condition. The consideration of chemical, biological and behavioral factors is fundamental for its prevention and therapy. Among the biological factors, saliva is one of the most important parameters in the protection against erosive wear. Objective: This review discusses the role of salivary factors on the development of dental erosion. Material and Methods: A search was undertaken on MeDLINe website for papers from 1969 to 2010. The keywords used in the re...

  2. Fluoride in dental erosion

    OpenAIRE

    Magalhães, A C; Wiegand, A.; Rios, D.; Buzalaf, M.A.R.; Lussi, A.

    2011-01-01

    Dental erosion develops through chronic exposure to extrinsic/intrinsic acids with a low pH. Enamel erosion is characterized by a centripetal dissolution leaving a small demineralized zone behind. In contrast, erosive demineralization in dentin is more complex as the acid-induced mineral dissolution leads to the exposure of collagenous organic matrix, which hampers ion diffusion and, thus, reduces further progression of the lesion. Topical fluoridation inducing the formation of a protective l...

  3. Erosion-corrosion; Erosionkorrosion

    Energy Technology Data Exchange (ETDEWEB)

    Aghili, B

    1999-05-01

    A literature study on erosion-corrosion of pipings in the nuclear industry was performed. Occurred incidents are reviewed, and the mechanism driving the erosion-corrosion is described. Factors that influence the effect in negative or positive direction are treated, as well as programs for control and inspection. Finally, examples of failures from databases on erosion-corrosion are given in an attachment 32 refs, 16 figs, tabs

  4. Structure, organization and dynamics of a Sardinian sand dune plant community

    OpenAIRE

    Cusseddu, Valentina

    2016-01-01

    Coastal sand dunes have attracted the attention of plant ecologists for over a century, but have largely relied on correlations to explain striking dune plant community organization. We experimentally examined longstanding hypotheses that sand binding, interspecific interactions, abiotic factors and seedling recruitment are drivers of sand dune plant community structure in Sardinia, Italy. Removing foundation species from the fore, middle and back dune over 3 years led to erosion and habitat ...

  5. Tonal noise production from a wall-mounted finite airfoil

    Science.gov (United States)

    Moreau, Danielle J.; Doolan, Con J.

    2016-02-01

    This study is concerned with the flow-induced noise of a smooth wall-mounted finite airfoil with flat ended tip and natural boundary layer transition. Far-field noise measurements have been taken at a single observer location and with a microphone array in the Virginia Tech Stability Wind Tunnel for a wall-mounted finite airfoil with aspect ratios of L / C = 1 - 3, at a range of Reynolds numbers (ReC = 7.9 ×105 - 1.6 ×106, based on chord) and geometric angles of attack (α = 0 - 6 °). At these Reynolds numbers, the wall-mounted finite airfoil produces a broadband noise contribution with a number of discrete equispaced tones at non-zero angles of attack. Spectral data are also presented for the noise produced due to three-dimensional vortex flow near the airfoil tip and wall junction to show the contributions of these flow features to airfoil noise generation. Tonal noise production is linked to the presence of a transitional flow state to the trailing edge and an accompanying region of mildly separated flow on the pressure surface. The separated flow region and tonal noise source location shift along the airfoil trailing edge towards the free-end region with increasing geometric angle of attack due to the influence of the tip flow field over the airfoil span. Tonal envelopes defining the operating conditions for tonal noise production from a wall-mounted finite airfoil are derived and show that the domain of tonal noise production differs significantly from that of a two-dimensional airfoil. Tonal noise production shifts to lower Reynolds numbers and higher geometric angles of attack as airfoil aspect ratio is reduced.

  6. Experimental evidence for bedrock erosion by suspended sediment

    Science.gov (United States)

    Scheingross, J. S.; Brun, F.; Lo, D. Y.; Omerdin, K.; Lamb, M. P.

    2013-12-01

    Fluvial bedrock incision influences channel evolution and sets the pace of landscape lowering. Bedrock incision often occurs via abrasion, and existing theory is divided on the erosional efficiency of sediment transported in suspension versus bed load, due in part to a lack of data to test model predictions. This represents a major knowledge gap as suspended sediment can account for the majority of the total fluvial sediment load, and untested models make opposite predictions of bedrock erosion in steep channels and during large floods. We performed controlled abrasion mill experiments examining suspended and bed load erosion, making use of an erodible polyurethane foam substrate as a bedrock analog to overcome previous experimental limitations and allow for measureable suspension erosion. Our results show foam erodes similar to natural rock, where erodibility is a function of tensile strength and density. To explore the role of the mode of sediment transport on erosion, we varied sediment size from gravel (42 mm diameter) to medium sand (0.4 mm diameter), while holding fixed hydraulics, sediment load, and substrate strength. Under these conditions, volumetric erosion rates decreased across the bed load (~101 - 103 cm3/hr) to suspended load (~0.01 - 100 cm3/hr) transition due to lower near-bed sediment concentrations (~25 g/l vs. 115 g/l), slower settling velocity (0.09 m/s vs. 0.49 m/s), and viscous damping of impacts (for particle Stokes numbers less than ~75) for suspended particles. Our results provide direct experimental evidence of erosion by suspended load, and upscaling results to field scale shows suspension erosion can outpace bed load erosion by up to a factor ~4 during large floods which suspend coarse sand and gravel, and where suspended sediment dominates the total load. These results imply that suspension erosion may also dominate on very steep slopes where commonly used bedrock incision models (which ignore suspension erosion) predict zero erosion

  7. Momentum or kinetic energy - How do substrate properties influence the calculation of rainfall erosivity?

    Science.gov (United States)

    Goebes, Philipp; Seitz, Steffen; Geißler, Christian; Lassu, Tamás; Peters, Piet; Seeger, Manuel; Nadrowski, Karin; Scholten, Thomas

    2014-09-01

    Rainfall erosivity is a key component in soil erosion by water. While kinetic energy and momentum are used to describe the erosivity of rainfall, and both are derived from mass and velocity of raindrops, it is not clear how different substrates transform this energy. In our study we conducted rainfall simulation experiments to determine splash detachment amounts of five substrates (coarse sand, medium sand, fine sand, PE balls, silt) for seven different rainfall intensities (52-116 mm h-1). We used linear mixed-effect modeling (LME) to calculate erosivity predictors for each substrate. Additionally, we separated drop-size-velocity relationship into lower left and upper right quarter to investigate the effect of small and slow just as big and fast raindrops on splash detachment amounts. We suggest using momentum divided by drop diameter as a substrate-independent erosivity predictor. To consider different substrates specific erosivity parameters are needed. Heavier substrates like sand are best described by kinetic energy multiplied by diameter whereas lighter substrates like silt point to momentum divided by diameter to the power of 1.5. Furthermore, our results show that substrates are differently affected by the size and velocity of drops. While splash detachment of light substances can be reliably predicted by drop size and velocity for small and slow drops, drop size and velocity loses its predictive power in heavier substrates like sand.

  8. Saliva and dental erosion

    Directory of Open Access Journals (Sweden)

    Marília Afonso Rabelo Buzalaf

    2012-10-01

    Full Text Available Dental erosion is a multifactorial condition. The consideration of chemical, biological and behavioral factors is fundamental for its prevention and therapy. Among the biological factors, saliva is one of the most important parameters in the protection against erosive wear. Objective: This review discusses the role of salivary factors on the development of dental erosion. Material and Methods: A search was undertaken on MeDLINe website for papers from 1969 to 2010. The keywords used in the research were "saliva", "acquired pellicle", "salivary flow", "salivary buffering capacity" and "dental erosion". Inclusion of studies, data extraction and quality assessment were undertaken independently and in duplicate by two members of the review team. Disagreements were solved by discussion and consensus or by a third party. Results: Several characteristics and properties of saliva play an important role in dental erosion. Salivary clearance gradually eliminates the acids through swallowing and saliva presents buffering capacity causing neutralization and buffering of dietary acids. Salivary flow allows dilution of the acids. In addition, saliva is supersaturated with respect to tooth mineral, providing calcium, phosphate and fluoride necessary for remineralization after an erosive challenge. Furthermore, many proteins present in saliva and acquired pellicle play an important role in dental erosion. Conclusions: Saliva is the most important biological factor affecting the progression of dental erosion. Knowledge of its components and properties involved in this protective role can drive the development of preventive measures targeting to enhance its known beneficial effects.

  9. Erosion resistance testing of plastic pipes

    OpenAIRE

    H. Tomanek; M. Makselon; J. Stabik

    2007-01-01

    Purpose: The purpose of this paper was to present the results of a special abrasion test of poly(vinyl chloride) and polypropylene filled with calcium carbonate pipes. Abrasion test’s results for pipes were compared with results of standard abrasion test (Taber method) and hardness test.Design/methodology/approach: Short cuts of pipe were subjected to erosion caused by erodent, usually a mixture of special kind of sand and water. The changes of pipe’s wall thickness was a measure of resistan...

  10. Evaluation of Sand Dunes Stabilization Techniques in Baiji District, Iraq

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    This research was conducted at the sand dunes stabilization research station in Baiji district, Iraq. Three techniques for sand dunes stabilization are selected: the first method is stabilization by clayey block barriers; the second method is stabilization by dry planting of tamarix (tamarix articulata)cuttings and the third is stabilization by using cane branch barriers. Randomized samples were taken from the surface and subsurface layers of the stabilized and shifting sand dunes to evaluate the effect of the three techniques on wind erosion parameters. The results indicate high significant differences between the wind erosion parameters in the surface and subsurface layers in the stabilized sand dunes, while there are insignificant differences between the subsurface layer of the stabilized dunes and the surface and subsurface layers in the active sand dunes. The results clarify the fact that there is an increase in the percentage of clay, silt, organic matter, mean weight diameter and the percentage of the dry aggregates (>0. 84 mm). A decrease is found in the rate of disaggregation for the dry aggregates in the samples of the surface layer of stabilized dunes when compared with the subsurface layer of stabilized dunes and the surface layer of the shifting sand dunes. There is a positive high significant correlation among the aggregate stability parameters and the percentage of clay and silt, and the content of organic matter in the studied layers.

  11. PERMEABILITY AND CONSOLIDATION OF SEDIMENT MIXTURES AS FUNCTION OF SAND CONTENT AND CLAY MINERALOGY

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The current study is the first step in a systematic experimental research on the erosion behaviour of sand-mud mixtures. It concerns the effect of a varying sand content and clay mineralogy on the porosity, structure, strength and permeability of artificially generated sediment mixtures. The permeability of a sediment mixture is an especially significant parameter concerning the type of erosion that occurs. It determines ifthe erosion of the bed is either a drained or an undrained process,respectively indicating surface erosion or mass erosion. Measurements on various mixtures concerning the consolidation coefficient and the permeability have been executed. Results show a distinct transition of behaviour between a sand-silt dominated network structure and a clay-water matrix. The occurrence of these two types of structures appears to depend on the porosity of the volume fraction of sand related to silt, which is, therefore, an important parameter concerning the type of erosion. Finally, the study provides a valuable data set that can be used as a reference for following stages of this research on the erosion behaviour of natural cohesive sediments.

  12. Analysis of viscous transonic flow over airfoil sections

    Science.gov (United States)

    Huff, Dennis L.; Wu, Jiunn-Chi; Sankar, L. N.

    1987-01-01

    A full Navier-Stokes solver has been used to model transonic flow over three airfoil sections. The method uses a two-dimensional, implicit, conservative finite difference scheme for solving the compressible Navier-Stokes equations. Results are presented as prescribed for the Viscous Transonic Airfoil Workshop to be held at the AIAA 25th Aerospace Sciences Meeting. The NACA 0012, RAE 2822 and Jones airfoils have been investigated for both attached and separated transonic flows. Predictions for pressure distributions, loads, skin friction coefficients, boundary layer displacement thickness and velocity profiles are included and compared with experimental data when possible. Overall, the results are in good agreement with experimental data.

  13. Integrated airfoil and blade design method for large wind turbines

    DEFF Research Database (Denmark)

    Zhu, Wei Jun; Shen, Wen Zhong

    2013-01-01

    million. A novel shape perturbation function is introduced to optimize the geometry on the existing airfoils and thus simplify the design procedure. The viscos/inviscid code Xfoil is used as the aerodynamic tool for airfoil optimization where the Reynolds number is set at 16 million with a free......-stream Mach number of 0.25 at the blade tip. Results show that these new airfoils achieve high power coefficient in a wide range of angles of attack (AOA) and they are extremely insensitive to surface roughness....

  14. Potential flow analysis of glaze ice accretions on an airfoil

    Science.gov (United States)

    Zaguli, R. J.

    1984-01-01

    The results of an analytical/experimental study of the flow fields about an airfoil with leading edge glaze ice accretion shapes are presented. Tests were conducted in the Icing Research Tunnel to measure surface pressure distributions and boundary layer separation reattachment characteristics on a general aviation wing section to which was affixed wooden ice shapes which approximated typical glaze ice accretions. Comparisons were made with predicted pressure distributions using current airfoil analysis codes as well as the Bristow mixed analysis/design airfoil panel code. The Bristow code was also used to predict the separation reattachment dividing streamline by inputting the appropriate experimental surface pressure distribution.

  15. Geometrical effects on the airfoil flow separation and transition

    KAUST Repository

    Zhang, Wei

    2015-04-25

    We present results from direct numerical simulations (DNS) of incompressible flow over two airfoils, NACA-4412 and NACA-0012-64, to investigate the effects of the airfoil geometry on the flow separation and transition patterns at Re=104 and 10 degrees incidence. The two chosen airfoils are geometrically similar except for maximum camber (respectively 4%C and 0 with C the chord length), which results in a larger projection area with respect to the incoming flow for the NACA-4412 airfoil, and a larger leeward surface curvature at the leading edge for the NACA-0012-64 airfoil. The governing equations are discretized using an energy conservative fourth-order spatial discretization scheme. An assessment on the two-point correlation indicates that a spanwise domain size of 0.8C is sufficiently large for the present simulations. We discuss flow separation at the airfoil leading edge, transition of the separated shear layer to three-dimensional flow and subsequently to turbulence. Numerical results reveal a stronger adverse pressure gradient field in the leading edge region of the NACA-0012-64 airfoil due to the rapidly varying surface curvature. As a result, the flow experiences detachment at x/C=0.08, and the separated shear layer transition via Kelvin-Helmholtz mechanism occurs at x/C=0.29 with fully developed turbulent flow around x/C=0.80. These flow development phases are delayed to occur at much downstream positions, respectively, observed around x/C=0.25, 0.71 and 1.15 for the NACA-4412 airfoil. The turbulent intensity, measured by the turbulent fluctuations and turbulent Reynolds stresses, are much larger for NACA-0012-64 from the transition onset until the airfoil trailing edge, while turbulence develops significantly downstream of the trailing edge for the NACA-4412 airfoil. For both airfoils, our DNS results indicate that the mean Reynolds stress u\\'u\\'/U02 reaches its maximum value at a distance from the surface approximately equal to the displacement

  16. Active Anti-erosion Protection Strategy in Tamarisk (Tamarix aphylla)

    Science.gov (United States)

    Han, Zhiwu; Yin, Wei; Zhang, Junqiu; Niu, Shichao; Ren, Luquan

    2013-12-01

    Plants have numerous active protection strategies for adapting to complex and severe environments. These strategies provide endless inspiration for extending the service life of materials and machines. Tamarisk (Tamarix aphylla), a tree that thrives in raging sandstorm regions, has adapted to blustery conditions by evolving extremely effective and robust erosion resistant characteristics. However, the relationships among its surface cracks, internal histology and biomechanics, such as cracks, rings, cells, elasticity modulus and growth stress, which account for its erosion resistance, remain unclear. This present study reveals that the directionally eccentric growth rings of tamarisk, which are attributed to reduced stress and accelerated cell division, promote the formation of surface cracks. The windward rings are more extensive than the leeward side rings. The windward surfaces are more prone to cracks, which improves erosion resistance. Our data provide insight into the active protection strategy of the tamarisk against wind-sand erosion.

  17. The Geodiversity in Drift Sand Landscapes of The Netherlands

    Science.gov (United States)

    van den Ancker, Hanneke; Jungerius, Pieter Dirk; Riksen, Michel

    2015-04-01

    The authors carried out detailed field studies of more than twelve drift sand landscapes in The Netherlands. The objective of these studies was to restore Natura-2000 values by restoring the wind activity. Active drift sands occur almost exclusively in The Netherlands, Natura 2000 habitat 2330 'Inland dunes with open Corynephorus and Agrostis grasslands', for which reason our country is largely responsible for this European landscape. Active drift sands had almost disappeared for two reasons: first, the stabilization of the drift sands by air pollution, mainly nitrogen, which stimulates the growth of algae and grasses that initiate soil formation, and second, by the growth of forests surrounding the sands, which decreases the wind force. The restoration studies revealed differences in the geodiversity between and within the drift sand areas. Whereas the drift sands on geological and soil maps show as almost homogenous areas, they have in fact highly variable geo-conditions of which examples will be given. These geodiversity aspects concern differences in geomorphological structure, origin, sediments and age of the drift sands. Differences in wind and water erosion, trampling and soil formation add to the geodiversity within the drift sand areas. Especially in the primary stages of succession the differences in geodiversity are relevant for the Natura-2000 values. We discerned three main types of active sands. Firstly, the impressive drift sands with large parabolic dune structures, often consisting of series of interlocking parabolic dunes. They developed from the northeast towards the southwest, against the direction of the dominant wind, and must have taken centuries to develop. Small parts of these systems are still active, other parts show different degrees of soil formation. Their origin is still unclear but probably dates from medieval times (Heidinga, 1985, Jungerius & Riksen, 2008). Second are the drift sand areas with irregular hills from 0.5 to about 2

  18. Influence green sand system by core sand additions

    Directory of Open Access Journals (Sweden)

    N. Špirutová

    2012-01-01

    Full Text Available Today, about two thirds of iron alloys casting (especially for graphitizing alloys of iron are produced into green sand systems with usually organically bonded cores. Separation of core sands from the green sand mixture is very difficult, after pouring. The core sand concentration increase due to circulation of green sand mixture in a closed circulation system. Furthermore in some foundries, core sands have been adding to green sand systems as a replacement for new sands. The goal of this contribution is: “How the green sand systems are influenced by core sands?”This effect is considered by determination of selected technological properties and degree of green sand system re-bonding. From the studies, which have been published yet, there is not consistent opinion on influence of core sand dilution on green sand system properties. In order to simulation of the effect of core sands on the technological properties of green sands, there were applied the most common used technologies of cores production, which are based on bonding with phenolic resin. Core sand concentration added to green sand system, was up to 50 %. Influence of core sand dilution on basic properties of green sand systems was determined by evaluation of basic industrial properties: moisture, green compression strength and splitting strength, wet tensile strength, mixture stability against staling and physical-chemistry properties (pH, conductivity, and loss of ignition. Ratio of active betonite by Methylene blue test was also determined.

  19. Sets resilient to erosion

    CERN Document Server

    Pegden, Wesley

    2011-01-01

    The erosion of a set in Euclidean space by a radius r>0 is the subset of X consisting of points at distance >/-r from the complement of X. A set is resilient to erosion if it is similar to its erosion by some positive radius. We give a somewhat surprising characterization of resilient sets, consisting in one part of simple geometric constraints on convex resilient sets, and, in another, a correspondence between nonconvex resilient sets and scale-invariant (e.g., 'exact fractal') sets.

  20. Baskarp Sand No. 15

    DEFF Research Database (Denmark)

    Ibsen, Lars Bo; Bødker, Lars Bødker

    The Soil Mechanics Laboratory has started performing tests with a new sand, Baskarp No 15. Baskarp No 15 is a graded sand from Sweden. The shapes of the largest grains are round, while the small grains have sharp edges. The main part of of Baskarp No 15 is quarts, but it also contains feldspar...

  1. Baskarp Sand No. 15

    DEFF Research Database (Denmark)

    Borup, Marianne; Hedegaard, Jette

    The Soil Mechanics Laboratory has started performing tests with a new sand, Baskarp No 15. Baskarp No 15 is a graded sand from Sweden. The shapes of the largest grains are round, while the small grains have sharp edges. The main part of of Baskarp No 15 is quarts, but it also contains feldspar an...

  2. Trailing Edge Noise Model Validation and Application to Airfoil Optimization

    DEFF Research Database (Denmark)

    Bertagnolio, Franck; Aagaard Madsen, Helge; Bak, Christian

    2010-01-01

    The aim of this article is twofold. First, an existing trailing edge noise model is validated by comparing with airfoil surface pressure fluctuations and far field sound pressure levels measured in three different experiments. The agreement is satisfactory in one case but poor in two other cases....... Nevertheless, the model reproduces the main tendencies observed in the measurements with respect to varying flow conditions. Second, the model is implemented into an airfoil design code that is originally used for aerodynamic optimization. An existing wind turbine airfoil is optimized in order to reduce its...... noise emission, trying at the same time to preserve some of its aerodynamic and geometric characteristics. The new designs are characterized by less cambered airfoils and flatter suction sides. The resulting noise reductions seem to be mainly achieved by a reduction in the turbulent kinetic energy...

  3. Profile catalogue for airfoil sections based on 3D

    Energy Technology Data Exchange (ETDEWEB)

    Bertagnolio, F.; Soerensen, Niels N.; Johansen, Jeppe

    2006-12-15

    This report is a continuation of the Wind Turbine Airfoil Catalogue which objective was, firstly to provide a database of aerodynamic characteristics for a wide range of airfoil profiles aimed at wind turbine applications, and secondly to test the two-dimensional Navier-Stokes solver EllipSys2D by comparing its results with experimental data. In the present work, the original two-dimensional results are compared with three-dimensional calculations as it was surmised that the two-dimensional assumption might be in some cases responsible for discrepancies between the numerical flow solution and the actual fluid flow, and thereby the incorrect prediction of airfoil characteristics. In addition, other features of the flow solver, such as transition and turbulence modelling, and their influence onto the numerical results are investigated. Conclusions are drawn regarding the evaluation of airfoil aerodynamic characteristics, as well as the use of the Navier-Stokes solver for fluid flow calculations in general. (au)

  4. Computational design and analysis of flatback airfoil wind tunnel experiment.

    Energy Technology Data Exchange (ETDEWEB)

    Mayda, Edward A. (University of California, Davis, CA); van Dam, C.P. (University of California, Davis, CA); Chao, David D. (University of California, Davis, CA); Berg, Dale E.

    2008-03-01

    A computational fluid dynamics study of thick wind turbine section shapes in the test section of the UC Davis wind tunnel at a chord Reynolds number of one million is presented. The goals of this study are to validate standard wind tunnel wall corrections for high solid blockage conditions and to reaffirm the favorable effect of a blunt trailing edge or flatback on the performance characteristics of a representative thick airfoil shape prior to building the wind tunnel models and conducting the experiment. The numerical simulations prove the standard wind tunnel corrections to be largely valid for the proposed test of 40% maximum thickness to chord ratio airfoils at a solid blockage ratio of 10%. Comparison of the computed lift characteristics of a sharp trailing edge baseline airfoil and derived flatback airfoils reaffirms the earlier observed trend of reduced sensitivity to surface contamination with increasing trailing edge thickness.

  5. Unsteady transonic flow control around an airfoil in a channel

    Science.gov (United States)

    Hamid, Md. Abdul; Hasan, A. B. M. Toufique; Ali, Mohammad; Mitsutake, Yuichi; Setoguchi, Toshiaki; Yu, Shen

    2016-04-01

    Transonic internal flow around an airfoil is associated with self-excited unsteady shock wave oscillation. This unsteady phenomenon generates buffet, high speed impulsive noise, non-synchronous vibration, high cycle fatigue failure and so on. Present study investigates the effectiveness of perforated cavity to control this unsteady flow field. The cavity has been incorporated on the airfoil surface. The degree of perforation of the cavity is kept constant as 30%. However, the number of openings (perforation) at the cavity upper wall has been varied. Results showed that this passive control reduces the strength of shock wave compared to that of baseline airfoil. As a result, the intensity of shock wave/boundary layer interaction and the root mean square (RMS) of pressure oscillation around the airfoil have been reduced with the control method.

  6. Numerical simulation of airfoil trailing edge serration noise

    DEFF Research Database (Denmark)

    Zhu, Wei Jun; Shen, Wen Zhong

    In the present work, numerical simulations are carried out for a low noise airfoil with and without serrated Trailing Edge. The Ffowcs Williams-Hawkings acoustic analogy is implemented into the in-house incompressible flow solver EllipSys3D. The instantaneous hydrodynamic pressure and velocity...... field are obtained using Large Eddy Simulation. To obtain the time history data of sound pressure, the flow quantities are integrated around the airfoil surface through the FW-H approach. The extended length of the serration is about 16.7% of the airfoil chord and the geometric angle of the serration...... is 28 degrees. The chord based Reynolds number is around 1.5x106. Simulations are compared with existing wind tunnel experiments at various angles of attack. Even though the airfoil under investigation is already optimized for low noise emission, numerical simulations and wind tunnel experiments show...

  7. Study of the TRAC Airfoil Table Computational System

    Science.gov (United States)

    Hu, Hong

    1999-01-01

    The report documents the study of the application of the TRAC airfoil table computational package (TRACFOIL) to the prediction of 2D airfoil force and moment data over a wide range of angle of attack and Mach number. The TRACFOIL generates the standard C-81 airfoil table for input into rotorcraft comprehensive codes such as CAM- RAD. The existing TRACFOIL computer package is successfully modified to run on Digital alpha workstations and on Cray-C90 supercomputers. A step-by-step instruction for using the package on both computer platforms is provided. Application of the newer version of TRACFOIL is made for two airfoil sections. The C-81 data obtained using the TRACFOIL method are compared with those of wind-tunnel data and results are presented.

  8. Development of Variable Camber Morphing Airfoil Using Corrugated Structure

    OpenAIRE

    横関, 智弘; 杉浦, 綾; 平野, 義鎭; Yokozeki, Tomohiro; Sugiura, Aya; Hirano, Yoshiyasu

    2014-01-01

    This paper describes the development and the wind tunnel test of a variable geometry morphing airfoil using corrugated structures. Proof-of-concept study of a morphing wing with corrugated flexible seamless flap-like structure is verified by finite element analysis, and a prototype is manufactured using carbon fiber reinforced plastics. For the actuation system, two servomotors are installed inside the prototype wing to control the airfoil shape by the chordwise tension of the connected wires...

  9. An inverse design method for 2D airfoil

    Science.gov (United States)

    Liang, Zhi-Yong; Cui, Peng; Zhang, Gen-Bao

    2010-03-01

    The computational method for aerodynamic design of aircraft is applied more universally than before, in which the design of an airfoil is a hot problem. The forward problem is discussed by most relative papers, but inverse method is more useful in practical designs. In this paper, the inverse design of 2D airfoil was investigated. A finite element method based on the variational principle was used for carrying out. Through the simulation, it was shown that the method was fit for the design.

  10. Response of a Thin Airfoil Encountering a Strong Density Discontinuity

    OpenAIRE

    Marble, F. E.

    1993-01-01

    Airfoil theory for unsteady motion has been developed extensively assuming the undisturbed medium to be of uniform density, a restriction accurate for motion in the atmosphere, G/auert (1929), Burgers (1935), Theodorsen (1935), Kussner (1936), Karman and Sears (1938), Kinney and Sears (1975). In some instances, notably for airfoils comprising fan, compressor and turbine blade rows, the undisturbed medium may carry density variations or "spots," resulting from non-uniformaties ...

  11. Static aeroelastic response of chiral-core airfoils

    OpenAIRE

    Spadoni, Alessandro; Ruzzene, Massimo

    2007-01-01

    Extensive research is being devoted to the analysis and application of cellular solids for the design of innovative structural components. The chiral geometry in particular features a unique mechanical behavior which is here exploited for the design of 2D airfoils with morphing capabilities. A coupled-physics model, comprising computational fluid dynamics and structural analyses, investigates the influence of the chiral core on the aerodynamic behavior of the airfoil. Specifically, the model ...

  12. Actinides, accelerators and erosion

    OpenAIRE

    Fifield L. K.; Tims S.G.

    2012-01-01

    Fallout isotopes can be used as artificial tracers of soil erosion and sediment accumulation. The most commonly used isotope to date has been 137Cs. Concentrations of 137Cs are, however, significantly lower in the Southern Hemisphere, and furthermore have now declined to 35% of original values due to radioactive decay. As a consequence the future utility of 137Cs is limited in Australia, with many erosion applications becoming untenable within the next 20 years, and there is a need to replace...

  13. Release of Escherichia coli from Foreshore Sand and Pore Water during Intensified Wave Conditions at a Recreational Beach.

    Science.gov (United States)

    Vogel, Laura J; O'Carroll, Denis M; Edge, Thomas A; Robinson, Clare E

    2016-06-01

    Foreshore beach sands and pore water may act as a reservoir and nonpoint source of fecal indicator bacteria (FIB) to surface waters. This paper presents data collected at a fine sand beach on Lake Huron, Canada over three field events. The data show that foreshore sand erosion as wave height increases results in elevated Escherichia coli concentrations in surface water, as well as depletion of E. coli from the foreshore sand and pore water. E. coli initially attached to foreshore sand rather than initially residing in the pore water was found to be the main contributor to elevated surface water concentrations. Surface water E. coli concentrations were a function of not only wave height (and associated sand erosion) but also the time elapsed since a preceding period of high wave intensity. This finding is important for statistical regression models used to predict beach advisories. While calculations suggest that foreshore sand erosion may be the dominant mechanism for releasing E. coli to surface water during intensified wave conditions at a fine sand beach, comparative characterization of the E. coli distribution at a coarse sand-cobble beach suggests that interstitial pore water flow and discharge may be more important for coarser sand beaches. PMID:27120087

  14. Release of Escherichia coli from Foreshore Sand and Pore Water during Intensified Wave Conditions at a Recreational Beach.

    Science.gov (United States)

    Vogel, Laura J; O'Carroll, Denis M; Edge, Thomas A; Robinson, Clare E

    2016-06-01

    Foreshore beach sands and pore water may act as a reservoir and nonpoint source of fecal indicator bacteria (FIB) to surface waters. This paper presents data collected at a fine sand beach on Lake Huron, Canada over three field events. The data show that foreshore sand erosion as wave height increases results in elevated Escherichia coli concentrations in surface water, as well as depletion of E. coli from the foreshore sand and pore water. E. coli initially attached to foreshore sand rather than initially residing in the pore water was found to be the main contributor to elevated surface water concentrations. Surface water E. coli concentrations were a function of not only wave height (and associated sand erosion) but also the time elapsed since a preceding period of high wave intensity. This finding is important for statistical regression models used to predict beach advisories. While calculations suggest that foreshore sand erosion may be the dominant mechanism for releasing E. coli to surface water during intensified wave conditions at a fine sand beach, comparative characterization of the E. coli distribution at a coarse sand-cobble beach suggests that interstitial pore water flow and discharge may be more important for coarser sand beaches.

  15. Hierarchical organization of a Sardinian sand dune plant community

    Science.gov (United States)

    Ceccherelli, Giulia; Bertness, Mark

    2016-01-01

    Coastal sand dunes have attracted the attention of plant ecologists for over a century, but they have largely relied on correlations to explain dune plant community organization. We examined long-standing hypotheses experimentally that sand binding, inter-specific interactions, abiotic factors and seedling recruitment are drivers of sand dune plant community structure in Sardinia, Italy. Removing foundation species from the fore-, middle- and back-dune habitats over three years led to erosion and habitat loss on the fore-dune and limited plant recovery that increased with dune elevation. Reciprocal species removals in all zones suggested that inter-specific competition is common, but that dominance is transient, particularly due to sand burial disturbance in the middle-dune. A fully factorial 2-year manipulation of water, nutrient availability and substrate stability revealed no significant proximate response to these physical factors in any dune zone. In the fore- and middle-dune, plant seeds are trapped under adult plants during seed germination, and seedling survivorship and growth generally increase with dune height in spite of increased herbivory in the back-dune. Sand and seed erosion leads to limited seed recruitment on the fore-dune while high summer temperatures and preemption of space lead to competitive dominance of woody plants in the back-dune. Our results suggest that Sardinian sand dune plant communities are organized hierarchically, structured by sand binding foundation species on the fore-dune, sand burial in the middle-dune and increasingly successful seedling recruitment, growth and competitive dominance in the back-dune. PMID:27478701

  16. Hierarchical organization of a Sardinian sand dune plant community.

    Science.gov (United States)

    Cusseddu, Valentina; Ceccherelli, Giulia; Bertness, Mark

    2016-01-01

    Coastal sand dunes have attracted the attention of plant ecologists for over a century, but they have largely relied on correlations to explain dune plant community organization. We examined long-standing hypotheses experimentally that sand binding, inter-specific interactions, abiotic factors and seedling recruitment are drivers of sand dune plant community structure in Sardinia, Italy. Removing foundation species from the fore-, middle- and back-dune habitats over three years led to erosion and habitat loss on the fore-dune and limited plant recovery that increased with dune elevation. Reciprocal species removals in all zones suggested that inter-specific competition is common, but that dominance is transient, particularly due to sand burial disturbance in the middle-dune. A fully factorial 2-year manipulation of water, nutrient availability and substrate stability revealed no significant proximate response to these physical factors in any dune zone. In the fore- and middle-dune, plant seeds are trapped under adult plants during seed germination, and seedling survivorship and growth generally increase with dune height in spite of increased herbivory in the back-dune. Sand and seed erosion leads to limited seed recruitment on the fore-dune while high summer temperatures and preemption of space lead to competitive dominance of woody plants in the back-dune. Our results suggest that Sardinian sand dune plant communities are organized hierarchically, structured by sand binding foundation species on the fore-dune, sand burial in the middle-dune and increasingly successful seedling recruitment, growth and competitive dominance in the back-dune. PMID:27478701

  17. Erosion corrosion of ferrous materials in solids containing liquids

    International Nuclear Information System (INIS)

    A flow loop with a pipe and a pipe contraction is used for erosion corrosion on iron materials. The paper consists a) of a parameter study of a 13% chromium steel in sand containing formation water from oil and gas winning for evaluation of the effect of flow velocity, flow geometry, particle size and particle concentration and b) the investigation of pump, aramature and process equipment materials behaviour under standardized test conditions. The results are discussed from the point of view of materials technology, flow mechanics and erosion corrosion mechanisms. (orig.)

  18. Numerical modelling of concentrated leak erosion during Hole Erosion Tests

    OpenAIRE

    Mercier, F.; S. Bonelli; Golay, F.; Anselmet, F; Philippe, P.; Borghi, R.

    2015-01-01

    This study focuses on the numerical modelling of concentrated leak erosion of a cohesive soil by a turbulent flow in axisymmetrical geometry, with application to the Hole Erosion Test (HET). The numerical model is based on adaptive remeshing of the water/soil interface to ensure accurate description of the mechanical phenomena occurring near the soil/water interface. The erosion law governing the interface motion is based on two erosion parameters: the critical shear stress and the erosion co...

  19. A Comparative Study on Sand Transport Modeling for Horizontal Multiphase Pipeline

    Directory of Open Access Journals (Sweden)

    Kan Wai Choong

    2014-02-01

    Full Text Available Presence of sand causes adverse effects on hydrocarbon production, pipeline erosion and problems at wellbore. If the problems persist, production may be stopped and delayed. This imposes workover cost. Hence, operating expenses increase and revenue reduces. There is no explicit calculation algorithm for sand transportation modeling readily available in flow simulators. Therefore, this study aims to develop an Excel-based spreadsheet on sand transportation to predict sand critical velocity and onset of sand deposition based on published literature. The authors reviewed nine sand transportation models in pipelines and made comparisons on the selected models based on various criteria. Four of which were then developed into a sand modeling spreadsheet. The four models are the Turian et al. (1987, Oudeman (1993, Stevenson et al. (2002b Model and Danielson (2007. The spreadsheet presently focuses on sand production prediction in horizontal two-phase flow. The Danielson model can predict sand hold up while the other models estimate grain size transportable and critical velocity of sand. Flowing pipeline properties, sand properties and results of simulations like using OLGA (for flow rate, velocity and superficial velocity of different phases are necessary inputs of the spreadsheet. A user selects any model based on different operating conditions or user preference. The spreadsheet was validated by comparing data extracted from the research papers. Sensitivity analyses can also be performed with the spreadsheet by manipulating the parameters such as grain size and flow rate. This review is useful for flow simulators’ development to include sand transport modeling.

  20. Long-term cosmogenic 10Be catchment-wide erosion rates in the Kruger National Park

    Science.gov (United States)

    Glotzbach, Christoph; Paape, Alexander; Reinwarth, Bastian; Baade, Jussi; Miller, Jordan; Rowntree, Kate

    2015-04-01

    In this study we estimated long-term catchment-wide erosion rates in the central and southern Kruger National Park with cosmogenic 10Be analyses. Samples were collected in small catchments (2-100 km2) upstream of dams, which were used to determine short-term sediment yield rates. 10Be-derived erosion rates vary from 4-15 mm/kyr. Although there are significant site-specific differences in geomorphic parameters and precipitation we could not identify a single parameter controlling long-term erosion. Geomorphic fieldwork reveals that an unknown fraction of sampled sand-sized channel sediments derived from partly extensive and up to a few-meters deep gully erosion, which may lead to an overestimation of 10Be-derived erosion rates. Cosmogenic nuclide production is rapidly decreasing with depth and consequently the measured 10Be concentration of stream sediments is a mixture of (i) sand with high 10Be concentration from colluvial creep or sheet flow from hillslopes and (ii) sand with low 10Be concentration from gully erosion. To correct erosion rates, we quantify sediments derived from gullies using a combination of mapping gullies using remote sensing data and field work and geochemical characterisation of intact hillslopes and gully side walls.

  1. Predicting wear of hydrotransport pipelines in oil sand slurries

    Energy Technology Data Exchange (ETDEWEB)

    Been, J.; Lu, B.; Wolodko, J. [Alberta Research Council, Edmonton, AB (Canada); Kiel, D. [Coanda Research and Development Corp., Burnaby, BC (Canada)

    2008-07-01

    An overview of erosion and corrosion methods and techniques was presented. Wear to pipelines is influenced by slurry flow and chemistry; solids loading; and electrochemical interactions. While several experimental techniques have been developed to rank the performance of different pipeline materials, experiments do not currently provide accurate quantitative prediction of pipeline wear in the field. Rotating cylinder electrodes (RCE) and jet impingement methods are used to study the effect of flow velocity on corrosion rate. Slurry pot erosion-corrosion testers are used to rank materials for use in more dilute, less turbulent slurries. Coriolois slurry erosion testers are used to rank the erosion resistance of different pipeline materials. A pilot-scale flow loop is now being constructed by the Alberta Research Council (ARC) in order to replicate wet erosion phenomena in oil sands applications. The flow loop will be used to simulate the field conditions of oil sands pipelines and develop predictive wear data and models. Coulombic shear stress and characteristic wall velocities have been determined using a 2-layer model designed to represent flow as 2 distinct layers. To date, the flow loop pilot study has demonstrated that wear rates in smaller diameter flow loops are not significantly different than larger diameter field installations. Preliminary calculations have demonstrated that the flow loop can be used to accurately simulate the hydrodynamics and wear typically experienced in field slurry flows. 67 refs., 2 tabs., 7 figs.

  2. Sand and Gravel Operations

    Data.gov (United States)

    Department of Homeland Security — This map layer includes sand and gravel operations in the United States. These data were obtained from information reported voluntarily to the USGS by the aggregate...

  3. Solid Particle Erosion of Date Palm Leaf Fiber Reinforced Polyvinyl Alcohol Composites

    Directory of Open Access Journals (Sweden)

    Jyoti R. Mohanty

    2014-01-01

    Full Text Available Solid particle erosion behavior of short date palm leaf (DPL fiber reinforced polyvinyl alcohol (PVA composite has been studied using silica sand particles (200 ± 50 μm as an erodent at different impingement angles (15–90° and impact velocities (48–109 m/s. The influence of fiber content (wt% of DPL fiber on erosion rate of PVA/DPL composite has also been investigated. The neat PVA shows maximum erosion rate at 30° impingement angle whereas PVA/DPL composites exhibit maximum erosion rate at 45° impingement angle irrespective of fiber loading showing semiductile behavior. The erosion efficiency of PVA and its composites varies from 0.735 to 16.289% for different impact velocities studied. The eroded surfaces were observed under scanning electron microscope (SEM to understand the erosion mechanism.

  4. Hydraulic design of Francis turbine exposed to sediment erosion

    OpenAIRE

    Gogstad, Peter Joachim

    2012-01-01

    Sediment erosion is a large problem for turbines operated in sand laden water, especially in the Himalayas and the Andes Mountains, where the contents of hard minerals in the rivers are high. A program called RenewableNepal supports the development of a new design philosophy for hydraulic turbines. NTNU and Kathmandu University cooperate within this program, and this master thesis is part of that cooperation.The objective of this thesis is to carry out the hydraulic design...

  5. Influence of Thickness Variation on the Flapping Performance of Symmetric NACA Airfoils in Plunging Motion

    Directory of Open Access Journals (Sweden)

    Liangyu Zhao

    2010-01-01

    Full Text Available In order to investigate the impact of airfoil thickness on flapping performance, the unsteady flow fields of a family of airfoils from an NACA0002 airfoil to an NACA0020 airfoil in a pure plunging motion and a series of altered NACA0012 airfoils in a pure plunging motion were simulated using computational fluid dynamics techniques. The “class function/shape function transformation“ parametric method was employed to decide the coordinates of these altered NACA0012 airfoils. Under specified plunging kinematics, it is observed that the increase of an airfoil thickness can reduce the leading edge vortex (LEV in strength and delay the LEV shedding. The increase of the maximum thickness can enhance the time-averaged thrust coefficient and the propulsive efficiency without lift reduction. As the maximum thickness location moves towards the leading edge, the airfoil obtains a larger time-averaged thrust coefficient and a higher propulsive efficiency without changing the lift coefficient.

  6. Erosion-Resistant Nanocoatings for Improved Energy Efficiency in Gas Turbines

    Energy Technology Data Exchange (ETDEWEB)

    Alman, David; Marcio, Duffles

    2014-02-05

    The objective of this Stage Gate IV project was to test and substantiate the viability of an erosion-resistant nanocoating for application on compressor airfoils for gas turbines in both industrial power generation and commercial aviation applications. To effectively complete this project, the National Energy Technology Laboratory’s Office of Research & Development teamed with MDS Coating Technologies Inc. (MCT), Delta Air Lines - Technical Operations Division (Delta Tech Ops), and Calpine Corporation. The coating targeted for this application was MCT’s Next Generation Coating, version 4 (NGC-v4 - with the new registered trademark name of BlackGold®). The coating is an erosion and corrosion resistant composite nanostructured coating. This coating is comprised of a proprietary ceramic-metallic nano-composite construction which provides enhanced erosion resistance and also retains the aerodynamic geometry of the airfoils. The objective of the commercial aviation portion of the project was to substantiate the coating properties to allow certification from the FAA to apply an erosion-resistant coating in a commercial aviation engine. The goal of the series of tests was to demonstrate that the durability of the airfoils is not affected negatively with the application of the NGC v4 coating. Tests included erosion, corrosion, vibration and fatigue. The results of the testing demonstrated that the application of the coating did not negatively impact the properties of the blades, especially fatigue performance – which is of importance in acceptance for commercial aviation applications. The objective of the industrial gas turbine element of the project was to evaluate the coating as an enabling technology for inlet fogging during the operation of industrial gas turbines. Fluid erosion laboratory scale tests were conducted to simulate inlet fogging conditions. Results of these tests indicated that the application of the erosion resistant NGC-v4 nanocoating improved the

  7. Prediction of the aerodynamic performance of the Mexico rotor by using airfoil data extracted from CFD

    OpenAIRE

    Hua YANG; Shen, Wen Zhong; Xu, Haoran; Hong, Zedong; Liu, Chao

    2013-01-01

    Blade Element Momentum (BEM) theory is a widely used technique for prediction of wind turbine aerodynamics performance, but the reliability of airfoil data is an important factor to improve the prediction accuracy of aerodynamic loads and power using a BEM code. The airfoil characteristics used in BEM codes are mostly based on 2D wind tunnel measurements of airfoils with constant span. However, a BEM code using airfoil data obtained directly from 2D wind tunnel measurements will not yield the...

  8. Aero-elastic stability of airfoil flow using 2-D CFD

    Energy Technology Data Exchange (ETDEWEB)

    Johansen, J. [Risoe National Lab., Roskilde (Denmark)

    1999-03-01

    A three degrees-of-freedom structural dynamics model has been coupled to a two-dimensional incompressible CFD code. The numerical investigation considers aero-elastic stability for two different airfoils; the NACA0012 and the LM 2 18 % airfoils. Stable and unstable configurations and limit cycle oscillations are predicted in accordance with literature for the first airfoil. An attempt to predict stall induced edge-wise vibrations on a wind turbine airfoil fails using this two-dimensional approach. (au)

  9. Large Eddy simulation of Trailing Edge Acoustic Emissions of an Airfoil

    OpenAIRE

    Wu, Jinlong; Devenport, William; Paterson, Eric; Sun, Rui; Xiao, Heng

    2015-01-01

    The present investigation of trailing edge acoustic emission of an airfoil concerns the effects of the broadband noise generated by the interaction of turbulent boundary layer and airfoil trailing edge, and the tonal noise generated by the vortex shedding of trailing edge bluntness. Large eddy simulation (LES) is performed on an NACA0012 airfoil with blunt trailing edge at a Reynolds number Rec = 400; 000 based on the airfoil chord length for three different configurations with different angl...

  10. Reduction of airfoil trailing edge noise by trailing edge blowing

    Science.gov (United States)

    Gerhard, T.; Erbslöh, S.; Carolus, T.

    2014-06-01

    The paper deals with airfoil trailing edge noise and its reduction by trailing edge blowing. A Somers S834 airfoil section which originally was designed for small wind turbines is investigated. To mimic realistic Reynolds numbers the boundary layer is tripped on pressure and suction side. The chordwise position of the blowing slot is varied. The acoustic sources, i.e. the unsteady flow quantities in the turbulent boundary layer in the vicinity of the trailing edge, are quantified for the airfoil without and with trailing edge blowing by means of a large eddy simulation and complementary measurements. Eventually the far field airfoil noise is measured by a two-microphone filtering and correlation and a 40 microphone array technique. Both, LES-prediction and measurements showed that a suitable blowing jet on the airfoil suction side is able to reduce significantly the turbulence intensity and the induced surface pressure fluctuations in the trailing edge region. As a consequence, trailing edge noise associated with a spectral hump around 500 Hz could be reduced by 3 dB. For that a jet velocity of 50% of the free field velocity was sufficient. The most favourable slot position was at 90% chord length.

  11. Integration of Airfoil Design during the design of new blades

    Energy Technology Data Exchange (ETDEWEB)

    Sartori, L.; Bottasso, L.; Croce, A. [Politecnico di Milano, Milan (Italy); Grasso, F. [ECN Wind Power, Petten (Netherlands)

    2013-09-15

    Despite the fact that the design of a new blade is a multidisciplinary task, often the different disciplines are combined together at later stage. Looking at the aerodynamic design, it is common practice design/select the airfoils first and then design the blade in terms of chord and twist based on the initial selection of the airfoils. Although this approach is quite diffused, it limits the potentialities of obtaining optimal performance. The present work is focused on investigating the benefits of designing the external shape of the blade including the airfoil shapes together with chord and twist. To accomplish this, a design approach has been developed, where an advanced gradient based optimization algorithm is able to control the shape of the blade. The airfoils described in the work are the NACA 4 digits, while the chord distribution and the twist distribution are described through Bezier curves. In this way, the complexity of the problem is limited while a versatile geometrical description is kept. After the details of the optimization scheme are illustrated, several numerical examples are shown, demonstrating the advantages in terms of performance and development time of integrating the design of the airfoils during the optimization of the blade.

  12. Energy Harvesting of a Flapping Airfoil in a Vortical Wake

    Science.gov (United States)

    Zheng, Z. Charlie; Wei, Zhenglun

    2014-11-01

    We study the response of a two-dimensional flapping airfoil in the wake downstream of an oscillating D-shape cylinder. The airfoil has either heaving or pitching motions. The leading edge vortex (LEV) and trailing edge vortex (TEV) of the airfoil play important roles in energy harvesting. Two major interaction modes between the airfoil and incoming vortices, the suppressing mode and the reinforcing mode, are identified. However, distinctions exist between the heaving and pitching motion in terms of their contributions to the interaction modes and the efficiency of the energy extraction. A potential theory and the related fluid dynamics analysis are developed to analytically demonstrate that the topology of the incoming vortices corresponding to the airfoil is the primary factor that determines the interaction modes. Finally, the trade-off between the input and the output is discussed. It is found that appropriate operational parameters for the heaving motion are preferable in order to preserve acceptable input power for energy harvesters, while appropriate parameters for the pitching motion are essential to achieve decent output power.

  13. Turbine Airfoil Leading Edge Film Cooling Bibliography: 1972–1998

    Directory of Open Access Journals (Sweden)

    D. M. Kercher

    2000-01-01

    Full Text Available Film cooling for turbine airfoil leading edges has been a common practice for at least 35 years as turbine inlet gas temperatures and pressures have continually increased along with cooling air temperatures for higher engine cycle efficiency. With substantial engine cycle performance improvements from higher gas temperatures, it has become increasingly necessary to film cool nozzle and rotor blade leading edges since external heat transfer coefficients and thus heat load are the highest in this airfoil region. Optimum cooling air requirements in this harsh environment has prompted a significant number of film cooling investigations and analytical studies reported over the past 25 years from academia, industry and government agencies. Substantial progress has been made in understanding the complex nature of leading edge film cooling from airfoil cascades, simulated airfoil leading edges and environment. This bibliography is a report of the open-literature references available which provide information on the complex aero–thermo interaction of leading edge gaseous film cooling with mainstream flow. From much of this investigative information has come successful operational leading edge film cooling design systems capable of sustaining airfoil leading edge durability in very hostile turbine environments.

  14. Design analysis of vertical wind turbine with airfoil variation

    Science.gov (United States)

    Maulana, Muhammad Ilham; Qaedy, T. Masykur Al; Nawawi, Muhammad

    2016-03-01

    With an ever increasing electrical energy crisis occurring in the Banda Aceh City, it will be important to investigate alternative methods of generating power in ways different than fossil fuels. In fact, one of the biggest sources of energy in Aceh is wind energy. It can be harnessed not only by big corporations but also by individuals using Vertical Axis Wind Turbines (VAWT). This paper presents a three-dimensional CFD analysis of the influence of airfoil design on performance of a Darrieus-type vertical-axis wind turbine (VAWT). The main objective of this paper is to develop an airfoil design for NACA 63-series vertical axis wind turbine, for average wind velocity 2,5 m/s. To utilize both lift and drag force, some of designs of airfoil are analyzed using a commercial computational fluid dynamics solver such us Fluent. Simulation is performed for this airfoil at different angles of attach rearranging from -12°, -8°, -4°, 0°, 4°, 8°, and 12°. The analysis showed that the significant enhancement in value of lift coefficient for airfoil NACA 63-series is occurred for NACA 63-412.

  15. Interaction of two-dimensional impulsively started airfoils

    Institute of Scientific and Technical Information of China (English)

    WU Fu-bing; ZENG Nian-dong; ZHANG Liang; WU De-ming

    2004-01-01

    Continuous vorticity panels were used to model general unsteady inviscid, incompressible, two-dimensional flows. The geometry of thc airfoil was approximated by series of short straight segments having endpoints that lie on the actual surface. A piecewise linear, continuous distribution of vorticity over the airfoil surface was used to generate disturbance flow. The no-penetration condition was imposed at the midpoint of each segment and at discrete times. The wake was simulated by a system of point vortices, which moved at local fluid velocity. At each time step, a new wake panel with uniform vorticity distribution was attached to the trailing edge, and the condition of constant circulation around the airfoil and wake was imposed. A new expression for Kutta condition was developed to study the interference effect between two impulsively started NACA0012 airfoils. The tandem arrangement was found to be the most effective to enhance the lift of the rear airfoil. The interference effect between tidal turbine blades was shown clearly.

  16. Design and verification of the Risø-B1 airfoil family for wind turbines

    DEFF Research Database (Denmark)

    Fuglsang, P.; Bak, C.; Gaunaa, M.;

    2004-01-01

    This paper presents the design and experimental verification of the Risø-B1 airfoil family for MW-size wind turbines with variable speed and pitch control. Seven airfoils were designed with thickness-to-chord ratios between 15% and 53% to cover the entire span of a wind turbine blade. The airfoil...

  17. Bentonite erosion. Final report

    International Nuclear Information System (INIS)

    Low saline water may reach KBS-3 repository depth, e.g. during periods of glaciation. Under such aqueous conditions, the montmorillonite part of the bentonite buffer might transform into a sol and thereby be transported away with flowing water in fractures. The primary aim with this report is to improve the understanding of the basic principles for this possible montmorillonite particle release. The report includes experimental and theoretical work performed at Clay Technology. Natural bentonite and ion-exchanged purified montmorillonite from three different geographical origins, Wyoming (U.S.), Milos (Greece) and Kutch (India) have been studied. Experimental and/or theoretical investigations have been performed with respect to: - Free swelling ability; - Rheological properties; - Rate of bentonite loss into fractures; - Filtering; - Ion exchange; - Sol formation ability; - Ion diffusion; - Mass loss due to erosion. The performed erosion experiments show that erosion does not occur in a mixed calcium/sodium montmorillonite with at least 20% calcium in exchange positions, when the external solution contains above 4 mM charge equivalents. This result is in agreement with the presented conceptual view of sol formation and measured equilibrium properties in mixed calcium/sodium montmorillonite. The findings imply that the buffer will be stable for non-glacial conditions. However, erosion due to sol formation cannot be ruled out for glacial conditions.

  18. Bentonite erosion. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Birgersson, Martin; Boergesson, Lennart; Hedstroem, Magnus; Karnland, Ola; Nilsson, Ulf (Clay Technology AB, Lund (Sweden))

    2009-12-15

    Low saline water may reach KBS-3 repository depth, e.g. during periods of glaciation. Under such aqueous conditions, the montmorillonite part of the bentonite buffer might transform into a sol and thereby be transported away with flowing water in fractures. The primary aim with this report is to improve the understanding of the basic principles for this possible montmorillonite particle release. The report includes experimental and theoretical work performed at Clay Technology. Natural bentonite and ion-exchanged purified montmorillonite from three different geographical origins, Wyoming (U.S.), Milos (Greece) and Kutch (India) have been studied. Experimental and/or theoretical investigations have been performed with respect to: - Free swelling ability; - Rheological properties; - Rate of bentonite loss into fractures; - Filtering; - Ion exchange; - Sol formation ability; - Ion diffusion; - Mass loss due to erosion. The performed erosion experiments show that erosion does not occur in a mixed calcium/sodium montmorillonite with at least 20% calcium in exchange positions, when the external solution contains above 4 mM charge equivalents. This result is in agreement with the presented conceptual view of sol formation and measured equilibrium properties in mixed calcium/sodium montmorillonite. The findings imply that the buffer will be stable for non-glacial conditions. However, erosion due to sol formation cannot be ruled out for glacial conditions.

  19. SEDIMENTATION AND EROSION STUDIES

    Institute of Scientific and Technical Information of China (English)

    Chih Ted YANG

    2005-01-01

    @@ The river systems observed today is the cumulative result of surface, rill, and gully erosion, and sediment transport, scour, and deposition. The divisions of approach between these two related areas are man-made, and are not based on sound science. Most of the erosion studies are done by geologists and agricultural engineers who are concerned of the surface, rill, and gully erosion and the loss of agricultural land productivity. Hydraulic engineers are more interested in the study of sediment transport, scour, and deposition, and their impacts on river engineering and hydraulic structures in rivers and reservoirs. Erosion studies are often based on empirical relationships or field data to determinate the annual sediment yield from a watershed. On the other hand, hydraulic engineers focus their attention on solving equations based on assumed initial and boundary conditions with a time scale of days, hours, or seconds. Both approaches have their complementary strengths and weaknesses. It is important to provide a forum for specialists in both areas to communicate, exchange ideas, and learn from each other.

  20. Experimental study of surface texture and resonance mechanism of booming sand

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The sound-producing mechanism of booming sand has long been a pending problem in the blown sand physics. Based on the earlier researches, the authors collected some silent sand samples from Tengger Desert, Australian Desert, Kuwait Desert, beaches of Hainan Island and Japanese coast as well as the soundless booming sand samples from the Mingsha Mountain in Dunhuang to make washing experiments. In the meantime the chemical corrosion experiment of glass micro-spheres, surface coating experiment and SEM examination were also conducted. The experimental results show that the sound production of booming sand seems to have nothing to do with the presence of SiO2 gel on the surface of sand grains and unrelated to the surface chemical composition of sand grains but is related to the resonance cavities formed by porous (pit-like) physical structure resulting from a number of factors such as wind erosion, water erosion, chemical corrosion and SiO2 gel deposition, etc. Its resonance mechanism is similar to that of Hemholz resonance cavity. Under the action of external forces, numerous spherical and sand grains with smooth surface and porous surface are set in motion and rub with each other to produce extremely weak vibration sound and then become audible sound by human ears through the magnification of surface cavity resonance. However the booming sands may lose their resonance mechanism and become silent sand due to the damping action caused by the invasion of finer particles such as dust and clay into surface holes of sand grains. Therefore, clearing away fine pollutants on the quartz grain surface is an effective way to make silent sand emit audible sound.

  1. Oil sands tax expenditures

    International Nuclear Information System (INIS)

    The oil sands are a strategic Canadian resource for which federal and provincial governments provide financial incentives to develop and exploit. This report describes the Oil Sands Tax Expenditure Model (OSTEM) developed to estimate the size of the federal income tax expenditure attributed to the oil sands industry. Tax expenditures are tax concessions which are used as alternatives to direct government spending for achieving government policy objectives. The OSTEM was developed within the business Income Tax Division of Canada's Department of Finance. Data inputs for the model were obtained from oil sands developers and Natural Resources Canada. OSTEM calculates annual revenues, royalties and federal taxes at project levels using project-level projections of capital investment, operating expenses and production. OSTEM calculates tax expenditures by comparing taxes paid under different tax regimes. The model also estimates the foregone revenue as a percentage of capital investment. Total tax expenditures associated with investment in the oil sands are projected to total $820 million for the period from 1986 to 2030, representing 4.6 per cent of the total investment. 10 refs., 2 tabs., 7 figs

  2. Multi-objective optimization design of airfoil and wing

    Institute of Scientific and Technical Information of China (English)

    ZHU; Ziqiang; FU; Hongyan; YU; Rixin; LIU; Jie

    2004-01-01

    To extend available monoobjective optimization methods to multiobjective and multidisciplinary optimization, the construction of a suitable resultant objective function(in deterministic method-DM) or a fitness function(in genetic algorithm-GA) is important. An objective function combination method (OFCM) of constructing such a function for constrained optimization problems is suggested. How to use both deterministic and genetic algorithms to biobjective and bidisciplinary optimal design of high performance airfoils and wings is discussed. Numerical results in both 2D (airfoil) and 3D (wing) cases show that the present method can be used to optimaize different kinds of initial airfoils and wings. The performance of optimized shape is improved significantly. The method is successful and effective.

  3. Response of a thin airfoil encountering strong density discontinuity

    Energy Technology Data Exchange (ETDEWEB)

    Marble, F.E. [California Inst. of Tech., Pasadena, CA (United States). Karman Lab. of Fluid Mechanics

    1993-12-01

    Airfoil theory for unsteady motion has been developed extensively assuming the undisturbed medium to be of uniform density, a restriction accurate for motion in the atmosphere. In some instances, notably for airfoil comprising fan, compressor and turbine blade rows, the undisturbed medium may carry density variations or ``spots``, resulting from non-uniformities in temperature or composition, of a size comparable to the blade chord. This condition exists for turbine blades, immediately downstream of the main burner of a gas turbine engine where the density fluctuations of the order of 50 percent may occur. Disturbances of a somewhat smaller magnitude arise from the ingestion of hot boundary layers into fans, and exhaust into hovercraft. Because these regions of non-uniform density convect with the moving medium, the airfoil experiences a time varying load and moment which the authors calculate.

  4. Aerodynamic performance of an annular classical airfoil cascade

    Science.gov (United States)

    Bergsten, D. E.; Stauter, R. C.; Fleeter, S.

    1983-01-01

    Results are presented for a series of experiments that were performed in a large-scale subsonic annular cascade facility that was specifically designed to provide three-dimensional aerodynamic data for the verification of numerical-calculation codes. In particular, the detailed three-dimensional aerodynamic performance of a classical flat-plate airfoil cascade is determined for angles of incidence of 0, 5, and 10 deg. The resulting data are analyzed and are correlated with predictions obtained from NASA's MERIDL and TSONIC numerical programs. It is found that: (1) at 0 and 5 deg, the airfoil surface data show a good correlation with the predictions; (2) at 10 deg, the data are in fair agreement with the numerical predictions; and (3) the two-dimensional Gaussian similarity relationship is appropriate for the wake velocity profiles in the mid-span region of the airfoil.

  5. Severe Environmental Corrosion Erosion Facility

    Data.gov (United States)

    Federal Laboratory Consortium — NETL’s Severe Environment Corrosion Erosion Facility in Albany, OR, allows researchers to safely examine the performance of materials in highly corrosive or erosive...

  6. Soil erosion and agricultural sustainability

    OpenAIRE

    Montgomery, David R.

    2007-01-01

    Data drawn from a global compilation of studies quantitatively confirm the long-articulated contention that erosion rates from conventionally plowed agricultural fields average 1–2 orders of magnitude greater than rates of soil production, erosion under native vegetation, and long-term geological erosion. The general equivalence of the latter indicates that, considered globally, hillslope soil production and erosion evolve to balance geologic and climate forcing, whereas conventional plow-bas...

  7. Experimental Investigation of Temperature Effects on Microparticle Sand Rebound Characteristics at Gas Turbine Representative Conditions

    OpenAIRE

    Delimont, Jacob M

    2014-01-01

    When a gas turbine operates in a particle laden environment, such as a desert, small solid particles are ingested into the engine. The ingested sand particles can cause damage to engine components and reduce the service life of the engine. Particle ingestion causes the erosion of metal blades and vanes, and, if the firing temperature is hot enough, deposition of molten particles in the hot sections of the engine. Both deposition and erosion phenomena can severely reduce overall engine perfo...

  8. Lund Sand No 0

    DEFF Research Database (Denmark)

    Ibsen, Lars Bo; Jakobsen, Finn Rosendal

    During the last 15 years the Geotechnical Engineering Group (GEG) at Aalborg University has performed triaxial tests with a sand called Lund No 0. Lund No 0 is a graded sand from a gravel pit near Horsens in Denmark. For the classification of the sand the following tests have been performed: Sieve...... test, Grain density, ds, Maximum, emax, and minimum, emin, void ratio. The strength parameters of Lund No 0 are detennined by some drained and undrained triaxial tests in the Danish Triaxial Cell. The Danish Triaxial Cell prescribes smooth pressure heads and specimens with equal height and diameter....... Four series with Id equal to 0.92, 0.87 0.76 and 0.55 have been performed....

  9. Trailing edge noise model applied to wind turbine airfoils

    DEFF Research Database (Denmark)

    Bertagnolio, Franck

    The aim of this work is firstly to provide a quick introduction to the theory of noise generation that are relevant to wind turbine technology with focus on trailing edge noise. Secondly, the socalled TNO trailing edge noise model developed by Parchen [1] is described in more details. The model...... is tested and validated by comparing with other results from the literature. Finally, this model is used in the optimization process of two reference airfoils in order to reduce their noise signature: the RISØ-B1-18 and the S809 airfoils....

  10. Trailing edge noise model applied to wind turbine airfoils

    Energy Technology Data Exchange (ETDEWEB)

    Bertagnolio, F.

    2008-01-15

    The aim of this work is firstly to provide a quick introduction to the theory of noise generation that are relevant to wind turbine technology with focus on trailing edge noise. Secondly, the socalled TNO trailing edge noise model developed by Parchen [1] is described in more details. The model is tested and validated by comparing with other results from the literature. Finally, this model is used in the optimization process of two reference airfoils in order to reduce their noise signature: the RISOE-B1-18 and the S809 airfoils. (au)

  11. Aspects of Numerical Simulation of Circulation Control Airfoils

    Science.gov (United States)

    Swanson, R. C.; Rumsey, C. L.; Anders, S. G.

    2005-01-01

    The mass-averaged compressible Navier-Stokes equations are solved for circulation control airfoils. Numerical solutions are computed with a multigrid method that uses an implicit approximate factorization smoother. The effects of flow conditions (e.g., free-stream Mach number, angle of attack, momentum coefficient) and mesh on the prediction of circulation control airfoil flows are considered. In addition, the impact of turbulence modeling, including curvature effects and modifications to reduce eddy viscosity levels in the wall jet (i.e., Coanda flow), is discussed. Computed pressure distributions are compared with available experimental data.

  12. Design of wind turbine airfoils based on maximum power coefficient

    DEFF Research Database (Denmark)

    Chen, Jin; Cheng, Jiangtao; Shen, Wenzhong;

    2010-01-01

    noise prediction model, the previously developed integrated design technique is further developed. The new code takes into account different airfoil requirements according to their local positions on a blade, such as sensitivity to leading edge roughness, design lift at off-design condition, stall......Based on the blade element momentum (BEM) theory, the power coefficient of a wind turbine can be expressed in function of local tip speed ratio and lift-drag ratio. By taking the power coefficient in a predefined range of angle of attack as the final design objective and combining with an airfoil...

  13. UK Frac Sand Resources

    OpenAIRE

    Mitchell, C. J.

    2015-01-01

    Although still just a glimmer in the gas man’s eye, the prospect of shale hydrocarbon (oil and gas) development in the UK has many companies thinking about the industrial minerals it will require. Chief amongst these is silica sand which is used as a ‘proppant’ in the hydraulic fracturing, or ‘fracking’, of shales to help release the gas. The UK has large resources of sand and sandstone, of which only a small proportion have the necessary technical properties that classify them as ‘silica san...

  14. Design and validation of the high performance and low noise CQU-DTU-LN1 airfoils

    DEFF Research Database (Denmark)

    Cheng, Jiangtao; Zhu, Wei Jun; Fischer, Andreas;

    2014-01-01

    avoid the problem of curvature discontinuity. An airfoil profile with discontinuous curvature can produce a discontinuous pressure gradient (i.e., local flow acceleration or deceleration), which enhances flow separation and thus decreases the airfoil performance. By combining the design method....... To validate the airfoil design, CQU-DTU-LN118 airfoil has been tested experimentally in the acoustic wind tunnel located at the Virginia Polytechnic Institute and State University (Virginia Tech), USA. To show the superiority of the CQU-DTU-LN1 airfoils, comparisons on aerodynamic performance and noise...

  15. Simulation of flow over double-element airfoil and wind tunnel test for use in vertical axis wind turbine

    DEFF Research Database (Denmark)

    Chougule, Prasad; Nielsen, Søren R.K.

    2014-01-01

    that there is an increase in the lift coefficient by 26% for single-element airfoil at analysed conditions. The CFD simulation results were validated with wind tunnel tests. It is also observe that by selecting proper airfoil configuration and blade sizes an increase in lift coefficient can further be achieved....... been made to utilize high lift technology for vertical axis wind turbines in order to improve power efficiency. High lift is obtained by double-element airfoil mainly used in aeroplane wing design. In this current work a low Reynolds number airfoil is selected to design a double-element airfoil blade...... for use in vertical axis wind turbine to improve the power efficiency. Double-element airfoil blade design consists of a main airfoil and a slat airfoil. Orientation of slat airfoil is a parameter of investigation in this paper and air flow simulation over double-element airfoil. With primary wind tunnel...

  16. Aerodynamic shape optimization for alleviating dynamic stall characteristics of helicopter rotor airfoil

    Directory of Open Access Journals (Sweden)

    Wang Qing

    2015-04-01

    Full Text Available In order to alleviate the dynamic stall effects in helicopter rotor, the sequential quadratic programming (SQP method is employed to optimize the characteristics of airfoil under dynamic stall conditions based on the SC1095 airfoil. The geometry of airfoil is parameterized by the class-shape-transformation (CST method, and the C-topology body-fitted mesh is then automatically generated around the airfoil by solving the Poisson equations. Based on the grid generation technology, the unsteady Reynolds-averaged Navier-Stokes (RANS equations are chosen as the governing equations for predicting airfoil flow field and the highly-efficient implicit scheme of lower–upper symmetric Gauss–Seidel (LU-SGS is adopted for temporal discretization. To capture the dynamic stall phenomenon of the rotor more accurately, the Spalart–Allmaras turbulence model is employed to close the RANS equations. The optimized airfoil with a larger leading edge radius and camber is obtained. The leading edge vortex and trailing edge separation of the optimized airfoil under unsteady conditions are obviously weakened, and the dynamic stall characteristics of optimized airfoil at different Mach numbers, reduced frequencies and angles of attack are also obviously improved compared with the baseline SC1095 airfoil. It is demonstrated that the optimized method is effective and the optimized airfoil is suitable as the helicopter rotor airfoil.

  17. The cumulative effects of using fine particles and cyanobacteria for rehabilitation of disturbed active sand dunes

    Science.gov (United States)

    Zaady, Eli; Katra, Itzhak; Barkai, Daniel; Knoll, Yaakov; Sarig, Shlomo

    2016-04-01

    One of the main problems in desertified lands worldwide is active wind-borne sand dunes, which lead to covering of fertile soils and agricultural fields. In regions with more than 100 mm of annual rainfall, sand dunes may be naturally stabilized by biocrusts (biological soil crusts). One of the main restraints of biocrust development is the typical lack of fine particles in sand dunes. Our study investigated the combined application of fine particles [coal fly-ash <100 micrometer] and bio-inoculant of filamentous cyanobacteria, isolated from nearby natural stabilized sand dunes, on the soil surface of active sands for increasing resistance to wind erosion. Boundary-layer wind tunnel experiments were conducted in experimental plots within a greenhouse for examining the effects of adding coal fly-ash and bio-inoculant to active sands. The biocrust development was evaluated via several physical and bio-physiological variables. In all the physical measurements and the bio-physiological variables, the treatment of "sand+inoculum+coal fly-ash" showed significant differences from the "sand-control". The combination led to the best results of surface stabilization in boundary-layer wind tunnel experiments, with the lowest sand fluxes. The filamentous cyanobacteria use the fine particles of the coal fly-ash as bridges for growing toward and adhering to the large sand particles. The cumulative effects of biocrusts and coal fly-ash enhance soil surface stabilization and may allow long-term sustainability.

  18. Design of the new Risoe-A1 airfoil family for wind turbines

    Energy Technology Data Exchange (ETDEWEB)

    Fuglsang, P.; Dahl, K.S. [Risoe National Lab., Wind Energy and Atmospheric Physics Dept., Roskilde (Denmark)

    1999-03-01

    A new airfoil family for wind turbines was developed by use of a design method using numerical optimization and the flow solver, XFOIL. The results were evaluated with the Navier-Stokes solver EllipSys2D. The airfoil family constitutes 6 airfoils ranging in thickness from 15% to 30%. The airfoils were designed to have a maximum lift coefficient around 1.5 in natural conditions and high lift-drag ratios below maximum lift. Insensitivity to leading edge roughness was obtained by securing that transition from laminar to turbulent flow on the suction side occurred close to the leading edge just before stall. The airfoil family was designed for a 600 kW wind turbine and provides a basis for further enhancing the characteristics of airfoils for wind turbines and to tailor airfoils for specific rotor sizes and power regulation principles. (au) EFP-95; EFP-98. 16 refs.

  19. Prediction of the wind turbine performance by using BEM with airfoil data extracted from CFD

    DEFF Research Database (Denmark)

    Yang, Hua; Shen, Wen Zhong; Xu, Haoran;

    2014-01-01

    codes are mostly based on 2D wind tunnel measurements of airfoils with constant span. Due to 3D effects, a BEM code using airfoil data obtained directly from 2D wind tunnel measurements will not yield the correct loading and power. As a consequence, 2D airfoil characteristics have to be corrected before......Blade element momentum (BEM) theory with airfoil data is a widely used technique for prediction of wind turbine aerodynamic performance, but the reliability of the airfoil data is an important factor for the prediction accuracy of aerodynamic loads and power. The airfoil characteristics used in BEM...... and the coefficient of lift and drag is determined by the forces on the blade. The extracted airfoil data are put into a BEM code without further corrections, and the calculated axial and tangential forces are compared to both computations using BEM with Shen's tip loss correction model and experimental data...

  20. Simulation of aerodynamic performance affected by vortex generators on blunt trailing-edge airfoils

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    An investigation was carried out by numerical simulation on a wind turbine airfoil and a blunt trailing-edge airfoil with and without vortex generators (VGs), and the performance of the airfoils was analyzed. By the simulation of airfoil DU 91-W2-250 it was verified that the numerical method and model were credible. Based on this airfoil, a new one with a blunt trailing edge of 6% chord was blended by symmetrically adding thickness, and its characteristics curves were obtained through computing at key angles of attack. Additionally, the pressure distribution on blended airfoil was analyzed by comparing to the airfoil without blend. The interaction of streamwise vortices induced by VGs with trailing vortex or separation vortex was considered, followed by the uncovery of how VGs can suppress the boundary layer separation.

  1. Actinides, accelerators and erosion

    Science.gov (United States)

    Tims, S. G.; Fifield, L. K.

    2012-10-01

    Fallout isotopes can be used as artificial tracers of soil erosion and sediment accumulation. The most commonly used isotope to date has been 137Cs. Concentrations of 137Cs are, however, significantly lower in the Southern Hemisphere, and furthermore have now declined to 35% of original values due to radioactive decay. As a consequence the future utility of 137Cs is limited in Australia, with many erosion applications becoming untenable within the next 20 years, and there is a need to replace it with another tracer. Plutonium could fill this role, and has the advantages that there were six times as many atoms of Pu as of 137Cs in fallout, and any loss to decay has been negligible due to the long half-lives of the plutonium isotopes. Uranium-236 is another long-lived fallout isotope with significant potential for exploitation as a tracer of soil and sediment movement. Uranium is expected to be more mobile in soils than plutonium (or caesium), and hence the 236U/Pu ratio will vary with soil depth, and so could provide an independent measure of the amount of soil loss. In this paper we discuss accelerator based ultra-sensitive measurements of plutonium and 236U isotopes and their advantages over 137Cs as tracers of soil erosion and sediment movement.

  2. Actinides, accelerators and erosion

    Directory of Open Access Journals (Sweden)

    Fifield L.K.

    2012-10-01

    Full Text Available Fallout isotopes can be used as artificial tracers of soil erosion and sediment accumulation. The most commonly used isotope to date has been 137Cs. Concentrations of 137Cs are, however, significantly lower in the Southern Hemisphere, and furthermore have now declined to 35% of original values due to radioactive decay. As a consequence the future utility of 137Cs is limited in Australia, with many erosion applications becoming untenable within the next 20 years, and there is a need to replace it with another tracer. Plutonium could fill this role, and has the advantages that there were six times as many atoms of Pu as of 137Cs in fallout, and any loss to decay has been negligible due to the long half-lives of the plutonium isotopes. Uranium-236 is another long-lived fallout isotope with significant potential for exploitation as a tracer of soil and sediment movement. Uranium is expected to be more mobile in soils than plutonium (or caesium, and hence the 236U/Pu ratio will vary with soil depth, and so could provide an independent measure of the amount of soil loss. In this paper we discuss accelerator based ultra-sensitive measurements of plutonium and 236U isotopes and their advantages over 137Cs as tracers of soil erosion and sediment movement.

  3. Particle erosion of infrared materials

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Erosion test of some infrared (IR) optical crystals (Ge,ZnS,MgF2,and quartz) was conducted with a number of different erodents (glass bead,and angular SiC,SiO2,Al2O3 by a homemade gas-blasting erosion tester.The influence of impact angle,impact velocity,erodent,and erosion time on the erosion rate and the effect of erosion on their IR transmittance were studied.The damaged surface morphology was characterized by scanning electron microscopy,and the erosion mechanism was explored.All of the materials show the maximum in wear versus impact angle at 90°,confirming their brittle failure behavior.It is found that the erosion rate is dependent on the erodent velocity by a power law,and it is highly correlated to the hardness of the erodent.The erosion rate-time curves do not show an incubation state,but an accelerated erosion period followed a maximum erosion (steady state).The decrease of IR transmittance is direct proportion to the erosion rate.Although the material loss occurs primarily by brittle process,ductile behavior is clearly an important feature,especially for MgF2 and ZnS.

  4. Extracting Oil From Tar Sands

    Science.gov (United States)

    Ford, L. B.; Daly, D.

    1984-01-01

    Recovery of oil from tar sands possible by batch process, using steam produced by solar heater. In extraction process, solar heater provides steam for heating solvent boiler. Boiling solvent removes oil from tar sands in Soxhlet extractor.

  5. Development and Life Prediction of Erosion Resistant Turbine Low Conductivity Thermal Barrier Coatings

    Science.gov (United States)

    Zhu, Dongming; Miller, Robert A.; Kuczmarski, Maria A.

    2010-01-01

    Future rotorcraft propulsion systems are required to operate under highly-loaded conditions and in harsh sand erosion environments, thereby imposing significant material design and durability issues. The incorporation of advanced thermal barrier coatings (TBC) in high pressure turbine systems enables engine designs with higher inlet temperatures, thus improving the engine efficiency, power density and reliability. The impact and erosion resistance of turbine thermal barrier coating systems are crucial to the turbine coating technology application, because a robust turbine blade TBC system is a prerequisite for fully utilizing the potential coating technology benefit in the rotorcraft propulsion. This paper describes the turbine blade TBC development in addressing the coating impact and erosion resistance. Advanced thermal barrier coating systems with improved performance have also been validated in laboratory simulated engine erosion and/or thermal gradient environments. A preliminary life prediction modeling approach to emphasize the turbine blade coating erosion is also presented.

  6. CFD code comparison for 2D airfoil flows

    DEFF Research Database (Denmark)

    Sørensen, Niels N.; Méndez, B.; Muñoz, A.;

    2016-01-01

    The current paper presents the effort, in the EU AVATAR project, to establish the necessary requirements to obtain consistent lift over drag ratios among seven CFD codes. The flow around a 2D airfoil case is studied, for both transitional and fully turbulent conditions at Reynolds numbers of 3 × ...

  7. Airfoil Trailing Edge Noise Generation and Its Surface Pressure Fluctuation

    DEFF Research Database (Denmark)

    Zhu, Wei Jun; Shen, Wen Zhong

    2015-01-01

    where the time history pressure data are recorded by the surface pressure microphones. After the flow-field is stabilized, the generated noise from the airfoil Trailing Edge (TE) is predicted using the acoustic analogy solver, where the results from LES are the input. It is found that there is a strong...

  8. Large Eddy Simulations of an Airfoil in Turbulent Inflow

    DEFF Research Database (Denmark)

    Gilling, Lasse; Sørensen, Niels

    2008-01-01

    Wind turbines operate in the turbulent boundary layer of the atmosphere and due to the rotational sampling effect the blades experience a high level of turbulence [1]. In this project the effect of turbulence is investigated by large eddy simulations of the turbulent flow past a NACA 0015 airfoil...

  9. The Ultimate Flow Controlled Wind Turbine Blade Airfoil

    Science.gov (United States)

    Seifert, Avraham; Dolgopyat, Danny; Friedland, Ori; Shig, Lior

    2015-11-01

    Active flow control is being studied as an enabling technology to enhance and maintain high efficiency of wind turbine blades also with contaminated surface and unsteady winds as well as at off-design operating conditions. The study is focused on a 25% thick airfoil (DU91-W2-250) suitable for the mid blade radius location. Initially a clean airfoil was fabricated and tested, as well as compared to XFoil predictions. From these experiments, the evolution of the separation location was identified. Five locations for installing active flow control actuators are available on this airfoil. It uses both Piezo fluidic (``Synthetic jets'') and the Suction and Oscillatory Blowing (SaOB) actuators. Then we evaluate both actuation concepts overall energy efficiency and efficacy in controlling boundary layer separation. Since efficient actuation is to be found at low amplitudes when placed close to separation location, distributed actuation is used. Following the completion of the baseline studies the study has focused on the airfoil instrumentation and extensive wind tunnel testing over a Reynolds number range of 0.2 to 1.5 Million. Sample results will be presented and outline for continued study will be discussed.

  10. Detached Eddy Simulations of an Airfoil in Turbulent Inflow

    DEFF Research Database (Denmark)

    Gilling, Lasse; Sørensen, Niels; Davidson, Lars

    2009-01-01

    The effect of resolving inflow turbulence in detached eddy simulations of airfoil flows is studied. Synthetic turbulence is used for inflow boundary condition. The generated turbulence fields are shown to decay according to experimental data as they are convected through the domain with the free ...

  11. A dynamic stall model for airfoils with deformable trailing edges

    DEFF Research Database (Denmark)

    Andersen, Peter Bjørn; Gaunaa, Mac; Bak, Christian;

    2009-01-01

    The present work contains an extension of the Beddoes-Leishman-type dynamic stall model. In this work, a deformable trailing-edge flap has been added to the dynamic stall model. The model predicts the unsteady aerodynamic forces and moments on an airfoil section undergoing arbitrary motion in heave...

  12. Unsteady Double Wake Model for the Simulation of Stalled Airfoils

    DEFF Research Database (Denmark)

    Ramos García, Néstor; Cayron, Antoine; Sørensen, Jens Nørkær

    2015-01-01

    separation and its dynamics. In this paper, the calculated integral forces have been successfully validated against wind tunnel measurements for the FFA-W3-211 airfoil. Furthermore, the computed highly unsteady flow field is analyzed in detail for a set of angles of attack ranging from light to deep stall...

  13. Modeling of Airfoil Trailing Edge Flap with Immersed Boundary Method

    DEFF Research Database (Denmark)

    Zhu, Wei Jun; Shen, Wen Zhong; Sørensen, Jens Nørkær

    2011-01-01

    to simulate the moving part of the trailing edge. Over the main fixed part of the airfoil the Navier-Stokes (NS) equations are solved using a standard body-fitted finite volume technique whereas the moving trailing edge flap is simulated with the immersed boundary method on a curvilinear mesh. The obtained...

  14. Flow characteristics over NACA4412 airfoil at low Reynolds number

    Directory of Open Access Journals (Sweden)

    Genç Mustafa Serdar

    2016-01-01

    Full Text Available In this study, the flow phenomena over NACA4412 were experimentally observed at various angle of attack and Reynolds number of 25000, 50000 and 75000, respectively. NACA4412 airfoil was manufactured at 3D printer and each tips of the wing were closed by using plexiglas to obtain two-dimensional airfoil. The experiments were conducted at low speed wind tunnel. The force measurement and hot-wire experiments were conducted to obtain data so that the flow phenomenon at the both top and bottom of the airfoil such as the flow separation and vortex shedding were observed. Also, smoke-wire experiment was carried out to visualize the surface flow pattern. After obtaining graphics from both force measurement experiment and hot-wire experiment compared with smoke wire experiment, it was noticed that there is a good coherence among the experiments. It was concluded that as Re number increased, the stall angle increased. And the separation bubble moved towards leading edge over the airfoil as the angle of attack increased.

  15. Mechanism of unconventional aerodynamic characteristics of an elliptic airfoil

    Directory of Open Access Journals (Sweden)

    Sun Wei

    2015-06-01

    Full Text Available The aerodynamic characteristics of elliptic airfoil are quite different from the case of conventional airfoil for Reynolds number varying from about 104 to 106. In order to reveal the fundamental mechanism, the unsteady flow around a stationary two-dimensional elliptic airfoil with 16% relative thickness has been simulated using unsteady Reynolds-averaged Navier–Stokes equations and the γ-Reθt‾ transition turbulence model at different angles of attack for flow Reynolds number of 5 × 105. The aerodynamic coefficients and the pressure distribution obtained by computation are in good agreement with experimental data, which indicates that the numerical method works well. Through this study, the mechanism of the unconventional aerodynamic characteristics of airfoil is analyzed and discussed based on the computational predictions coupled with the wind tunnel results. It is considered that the boundary layer transition at the leading edge and the unsteady flow separation vortices at the trailing edge are the causes of the case. Furthermore, a valuable insight into the physics of how the flow behavior affects the elliptic airfoil’s aerodynamics is provided.

  16. Stability investigation of an airfoil section with active flap control

    DEFF Research Database (Denmark)

    Bergami, Leonardo; Gaunaa, Mac

    2010-01-01

    fatigue load alleviation. The structural model of the 2-D airfoil section contains three degrees of freedom: heave translation, pitch rotation and flap deflection. A potential flow model provides the aerodynamic forces and their distribution. The unsteady aerodynamics are described using an indicial...

  17. An Extreme Event as a Game Changer in Coastal Erosion Management

    DEFF Research Database (Denmark)

    Sørensen, Carlo Sass; Drønen, Nils K.; Knudsen, Per;

    2016-01-01

    of cyclone Xaver in December 2013 with severe coastal erosion led to collaboration between the involved municipalities to work on a coherent solution for the entire coastline that involves sand nourishments, renovation and optimization of hard protection structures, and the restoration of recreational values...

  18. Adjoint-based airfoil shape optimization in transonic flow

    Science.gov (United States)

    Gramanzini, Joe-Ray

    The primary focus of this work is efficient aerodynamic shape optimization in transonic flow. Adjoint-based optimization techniques are employed on airfoil sections and evaluated in terms of computational accuracy as well as efficiency. This study examines two test cases proposed by the AIAA Aerodynamic Design Optimization Discussion Group. The first is a two-dimensional, transonic, inviscid, non-lifting optimization of a Modified-NACA 0012 airfoil. The second is a two-dimensional, transonic, viscous optimization problem using a RAE 2822 airfoil. The FUN3D CFD code of NASA Langley Research Center is used as the ow solver for the gradient-based optimization cases. Two shape parameterization techniques are employed to study their effect and the number of design variables on the final optimized shape: Multidisciplinary Aerodynamic-Structural Shape Optimization Using Deformation (MASSOUD) and the BandAids free-form deformation technique. For the two airfoil cases, angle of attack is treated as a global design variable. The thickness and camber distributions are the local design variables for MASSOUD, and selected airfoil surface grid points are the local design variables for BandAids. Using the MASSOUD technique, a drag reduction of 72.14% is achieved for the NACA 0012 case, reducing the total number of drag counts from 473.91 to 130.59. Employing the BandAids technique yields a 78.67% drag reduction, from 473.91 to 99.98. The RAE 2822 case exhibited a drag reduction from 217.79 to 132.79 counts, a 39.05% decrease using BandAids.

  19. Replacement of Natural Sand with Efficient Alternatives: Recent Advances in Concrete Technology

    Directory of Open Access Journals (Sweden)

    Anzar Hamid Mir

    2015-03-01

    Full Text Available Concrete is the most undisputable material being used in infrastructure development throughout the world. It is a globally accepted construction material in all types of Civil Engineering structures. Natural sand is a prime material used for the preparation of concrete and also plays an important role in Mix Design. Now a day‟s river erosion and other environmental issues have led to the scarcity of river sand. The reduction in the sources of natural sand and the requirement for reduction in the cost of concrete production has resulted in the increased need to find new alternative materials to replace river sand so that excess river erosion is prevented and high strength concrete is obtained at lower cost. Partial or full replacement of natural sand by the other alternative materials like quarry dust, foundry sand and others are being researched from past two decades, in view of conserving the ecological balance. This paper summarizes conclusions of experiments conducted for the properties like strength, durability etc. It was observed the results have shown positive changes and improvement in mechanical properties of the conventional concrete due to the addition or replacement of fine sand with efficient alternatives.

  20. A terminological matter: paragenesis, antigravitative erosion or antigravitational erosion ?

    Directory of Open Access Journals (Sweden)

    Pasini G.

    2009-07-01

    Full Text Available In the speleological literature three terms are utilized to designate the “ascending erosion”: paragenesis (= paragénésis, coined in1968, antigravitative erosion (= erosione antigravitativa, coined in 1966 and antigravitational erosion (wrong English translation ofthe Italian term erosione antigravitativa, utilized later on. The term paragenesis should be abandoned because of the priority of theterm erosione antigravitativa - on the ground of the “law of priority” – and because of its ambiguous etimology. On the other hand,the term antigravitational erosion should be forsaken in favour of the term antigravitative erosion, given the meaning that the termsgravitation and gravity have in Physics. Therefore, to designate the phenomenon of the “ascending erosion” there would be nothingleft but the term antigravitative erosion.The antigravitative erosion process and its recognizability are illustrated.Examples of caves with evident antigravitative erosion phenomena, developed in different karstifiable rocks and in several partsof the world, are given.It is recalled that the antigravitative erosion is a phenomenon well-known since 1942 and widely proven and supported, and that it isrelatively easy – in many cases - to recognize the antigravitative origin of karstic passages.It is stressed that the antigravitative erosion is an important phenomenon, exclusive of the karstic caves and unique in nature.

  1. Robust Airfoil Optimization with Multi-objective Estimation of Distribution Algorithm

    Institute of Scientific and Technical Information of China (English)

    Zhong Xiaoping; Ding Jifeng; Li Weiji; Zhang Yong

    2008-01-01

    A transonic airfoil designed by means of classical point-optimization may result in its dramatically inferior performance under off-design conditious. To overcome this shortcoming, robust design is proposed to fred out the optimal profile of an airfoil to maintain its performance in an uncertain environment. The robust airfoil optimization is aimed to minimize mean values and variances of drag coefficients while satisfying the lift and thickness constraints over a range of Maeb numbers. A multi-objective estimation of distribution algorithm is applied to the robust airfoil optimization on the base of the RAE2822 benchmark airfoil. The shape of the airfoil is obtained through superposing ten Hick-Heune shape functions upon the benchmark airfoil. A set of design points is selected according to a uniform design table for aerodynamic evaluation. A Kriging model of drag coefficient is coustrueted with those points to reduce eumputing costs. Over the Maeh range fi'om 0.7 to 0.8, the airfoil generated by the robust optimization has a configuration characterized by supercritical airfoil with low drag coefficients. The small fluctuation in its drag coefficients means that the performance of the robust airfoil is insensitive to variation of Mach number.

  2. Physical Characterizations of Sands and Their Influence in Fall Velocity

    Directory of Open Access Journals (Sweden)

    R. M. Gabriel

    2008-01-01

    Full Text Available Cancun beach is one of the most important tourist resorts on the Mexican coast, and is of prime importance to the local and national economies. As a result of the intense use of the beach and the unavailability of sand reserves, the extreme weather events that occur in the region (hurricanes have permanently damaged the beach. Over the last two decades several strong hurricanes severely weakened the system, but hurricane Wilma, October 2005, caused devastating erosion to the beach. After Wilma, an emergency nourishment project was implemented pumping a volume of 2.7 million m3 of sand onto the beach. Clearly, the sand used for the nourishment has a different shape factor, diameter distribution and density property compared to the native sand. The main goal of this paper is to characterize and compare the fall velocities of sand samples taken in and around Cancun. The settling velocities obtained for several samples were compared with the empirical formulations proposed by various authors. The influence of several parameters measured in the laboratory is discussed and a new formulation is presented.

  3. Simulation model of erosion and deposition on a barchan dune

    Science.gov (United States)

    Howard, A. D.; Morton, J. B.; Gal-El-hak, M.; Pierce, D. B.

    1977-01-01

    Erosion and deposition over a barchan dune near the Salton Sea, California, are modeled by bookkeeping the quantity of sand in saltation following streamlines of transport. Field observations of near surface wind velocity and direction plus supplemental measurements of the velocity distribution over a scale model of the dune are combined as input to Bagnold type sand transport formulas corrected for slope effects. A unidirectional wind is assumed. The resulting patterns of erosion and deposition compare closely with those observed in the field and those predicted by the assumption of equilibrium (downwind translation of the dune without change in size or geometry). Discrepancies between the simulated results and the observed or predicted erosional patterns appear to be largely due to natural fluctuations in the wind direction. The shape of barchan dunes is a function of grain size, velocity, degree of saturation of the oncoming flow, and the variability in the direction of the oncoming wind. The size of the barchans may be controlled by natural atmospheric scales, by the age of the dunes, or by the upwind roughness. The upwind roughness can be controlled by fixed elements or by sand in the saltation. In the latter case, dune scale is determined by grain size and wind velocity.

  4. Effect of compost on erodibility of loamy sand under simulated rainfall

    DEFF Research Database (Denmark)

    Arthur, Emmanuel; Cornelis, W.M.; Vermang, J.;

    2011-01-01

    Three types of composts [vegetable, fruit and yard waste compost (VFYW), garden waste compost (GW), and spent mushroom compost (SM)] were applied at a rate of 30 m3 ha−1 for 10 years to loamy sand, to determine its effect on the aggregate stability and susceptibility to water erosion. Aggregate s...

  5. Advancements in adaptive aerodynamic technologies for airfoils and wings

    Science.gov (United States)

    Jepson, Jeffrey Keith

    Although aircraft operate over a wide range of flight conditions, current fixed-geometry aircraft are optimized for only a few of these conditions. By altering the shape of the aircraft, adaptive aerodynamics can be used to increase the safety and performance of an aircraft by tailoring the aircraft for multiple flight conditions. Of the various shape adaptation concepts currently being studied, the use of multiple trailing-edge flaps along the span of a wing offers a relatively high possibility of being incorporated on aircraft in the near future. Multiple trailing-edge flaps allow for effective spanwise camber adaptation with resulting drag benefits over a large speed range and load alleviation at high-g conditions. The research presented in this dissertation focuses on the development of this concept of using trailing-edge flaps to tailor an aircraft for multiple flight conditions. One of the major tasks involved in implementing trailing-edge flaps is in designing the airfoil to incorporate the flap. The first part of this dissertation presents a design formulation that incorporates aircraft performance considerations in the inverse design of low-speed laminar-flow adaptive airfoils with trailing-edge cruise flaps. The benefit of using adaptive airfoils is that the size of the low-drag region of the drag polar can be effectively increased without increasing the maximum thickness of the airfoil. Two aircraft performance parameters are considered: level-flight maximum speed and maximum range. It is shown that the lift coefficients for the lower and upper corners of the airfoil low-drag range can be appropriately adjusted to tailor the airfoil for these two aircraft performance parameters. The design problem is posed as a part of a multidimensional Newton iteration in an existing conformal-mapping based inverse design code, PROFOIL. This formulation automatically adjusts the lift coefficients for the corners of the low-drag range for a given flap deflection as

  6. Multiperspective analysis of erosion tolerance

    Directory of Open Access Journals (Sweden)

    Sparovek Gerd

    2003-01-01

    Full Text Available Erosion tolerance is the most multidisciplinary field of soil erosion research. Scientists have shown lack in ability to adequately analyze the huge list of variables that influence soil loss tolerance definitions. For these the perspectives of erosion made by farmers, environmentalists, society and politicians have to be considered simultaneously. Partial and biased definitions of erosion tolerance may explain not only the polemic nature of the currently suggested values but also, in part, the nonadoption of the desired levels of erosion control. To move towards a solution, considerable changes would have to occur on how this topic is investigated, especially among scientists, who would have to change methods and strategies and extend the perspective of research out of the boundaries of the physical processes and the frontiers of the academy. A more effective integration and communication with the society and farmers, to learn about their perspective of erosion and a multidisciplinary approach, integrating soil, social, economic and environmental sciences are essential for improved erosion tolerance definitions. In the opinion of the authors, soil erosion research is not moving in this direction and a better understanding of erosion tolerance is not to be expected in the near future.

  7. Booming Sand Dunes

    Science.gov (United States)

    Vriend, Nathalie

    "Booming" sand dunes are able to produce low-frequency sound that resembles a pure note from a music instrument. The sound has a dominant audible frequency (70-105 Hz) and several higher harmonics and may be heard from far distances away. A natural or induced avalanche from a slip face of the booming dune triggers the emission that may last for several minutes. There are various references in travel literature to the phenomenon, but to date no scientific explanation covered all field observations. This thesis introduces a new physical model that describes the phenomenon of booming dunes. The waveguide model explains the selection of the booming frequency and the amplification of the sound in terms of constructive interference in a confined geometry. The frequency of the booming is a direct function of the dimensions and velocities in the waveguide. The higher harmonics are related to the higher modes of propagation in the waveguide. The experimental validation includes quantitative field research at the booming dunes of the Mojave Desert and Death Valley National Park. Microphone and geophone recordings of the acoustic and seismic emission show a variation of booming frequency in space and time. The analysis of the sensor data quantifies wave propagation characteristics such as speed, dispersion, and nonlinear effects and allows the distinction between the source mechanism of the booming and the booming itself. The migration of sand dunes results from a complicated interplay between dune building, wind regime, and precipitation. The morphological and morphodynamical characteristics of two field locations are analyzed with various geophysical techniques. Ground-penetrating radar images the subsurface structure of the dunes and reveal a natural, internal layering that is directly related to the history of dune migration. The seismic velocity increases abruptly with depth and gradually increases with downhill position due to compaction. Sand sampling shows local

  8. Erosion mechanism and erosion products in carbon-based materials

    Energy Technology Data Exchange (ETDEWEB)

    Arkhipov, N.; Bakhtin, V.; Barsuk, V.; Kurkin, S.; Mironova, E.; Piazza, G.; Safronov, V. E-mail: vsafr@rico.ttk.ru; Scaffidi-Argentina, F.; Toporkov, D.; Vasenin, S.; Wuerz, H.; Zhitlukhin, A

    2002-12-01

    Plasma/material interaction was studied in disruption simulation experiments at the plasma gun facility MK-200. Graphite and carbon-fibre composites were exposed to pulsed energetic plasma under heat loads typically expected for disruptions in future tokamaks. Erosion rates, erosion mechanisms and the properties of the eroded carbon have been studied.

  9. Sediment mathematical model for sand ridges and sand waves

    Institute of Scientific and Technical Information of China (English)

    LI Daming; WANG Xiao; WANG Xin; LI Yangyang

    2016-01-01

    A new theoretical model is formulated to describe internal movement mechanisms of the sand ridges and sand waves based on the momentum equation of a solid-liquid two-phase flow under a shear flow. Coupling this equation with two-dimensional shallow water equations and wave reflection-diffraction equation of mild slope, a two-dimensional coupling model is established and a validation is carried out by observed hydrogeology, tides, waves and sediment. The numerical results are compared with available observations. Satisfactory agreements are achieved. This coupling model is then applied to the Dongfang 1-1 Gas Field area to quantitatively predict the movement and evolution of submarine sand ridges and sand waves. As a result, it is found that the sand ridges and sand waves movement distance increases year by year, but the development trend is stable.

  10. Experimental verification of the new RISOe-A1 airfoil family for wind turbines

    Energy Technology Data Exchange (ETDEWEB)

    Dahl, K.S.; Fuglsang, P.; Antoniou, I. [Risoe National Lab., Roskilde (Denmark)

    1999-03-01

    This paper concerns the experimental verification of a new airfoil family for wind turbines. The family consist of airfoils in the relative thickness range from 15% to 30%. Three airfoils, Risoe-A1-18, Risoe-A1-21, and Risoe-A1-24 were tested in a wind tunnel. The verification consisted of both static and dynamic measurements. Here, the static results are presented for a Reynolds number of 1.6x10{sup 6} for the following airfoil configurations: smooth surface (all three airfoils) and Risoe-A1-24 mounted with leading edge roughness, vortex generators, and Gurney-flaps, respectively. All three airfoils have constant lift curve slope and almost constant drag coefficient until the maximum lift coefficient of about 1.4 is reached. The experimental results are compared with corresponding computational from the general purpose flow solver, EllipSys2D, showing good agreement. (au)

  11. Unsteady 2D potential-flow forces on a thin variable geometry airfoil undergoing arbitrary motion

    DEFF Research Database (Denmark)

    Gaunaa, M.

    2006-01-01

    In this report analytical expressions for the unsteady 2D force distribution on a variable geometry airfoil undergoing arbitrary motion are derived under the assumption of incompressible, irrotational, inviscid flow. The airfoil is represented by itscamberline as in classic thin-airfoil theory......, and the deflection of the airfoil is given by superposition of chordwise deflection mode shapes. It is shown from the expressions for the forces, that the influence from the shed vorticity in the wake isdescribed by the same time-lag for all chordwise positions on the airfoil. This time-lag term can be approximated...... of the present theory in problems employing the eigenvalue approach, such as stabilityanalysis. The analytical expressions for the forces simplify to all previously known steady and unsteady thin-airfoil solutions. Apart from the obvious applications within active load control/reduction, the current theory can...

  12. Friction surfacing for enhanced surface protection of marine engineering components: erosion-corrosion study

    Science.gov (United States)

    Rajakumar, S.; Balasubramanian, V.; Balakrishnan, M.

    2016-08-01

    Good mechanical properties combined with outstanding corrosion-resistance properties of cast nickel-aluminum bronze (NAB) alloy lead to be a specific material for many marine applications, including ship propellers. However, the erosion-corrosion resistance of cast-NAB alloy is not as good as wrought NAB alloy. Hence, in this investigation, an attempt has been made to improve the erosion-corrosion resistance of cast NAB alloy by depositing wrought (extruded) NAB alloy applying the friction surfacing (FS) technique. Erosion-corrosion tests were carried out in slurries composed of sand particles of 3.5% NaCl solution. Silica sand having a nominal size range of 250-355 μm is used as an erodent. Specimens were tested at 30° and 90° impingement angles. It is observed that the erosion and erosion-corrosion resistance of friction surfaced NAB alloy exhibited an improvement as compared to cast NAB alloy. Scanning electron microscope (SEM) analysis showed that the erosion tracks developed on the cast NAB alloy were wider and deeper than those formed on the friction surfaced extruded NAB alloy.

  13. A critical evaluation of the predictions of the NASA-Lockheed multielement airfoil computer program

    Science.gov (United States)

    Brune, G. W.; Manke, J. W.

    1978-01-01

    Theoretical predictions of several versions of the multielement airfoil computer program are evaluated. The computed results are compared with experimental high lift data of general aviation airfoils with a single trailing edge flap, and of airfoils with a leading edge flap and double slotted trailing edge flaps. Theoretical and experimental data include lift, pitching moment, profile drag and surface pressure distributions, boundary layer integral parameters, skin friction coefficients, and velocity profiles.

  14. S833, S834, and S835 Airfoils: November 2001--November 2002

    Energy Technology Data Exchange (ETDEWEB)

    Somers, D. M.

    2005-08-01

    A family of quiet, thick, natural-laminar-flow airfoils, the S833, S834, and S835, for 1 - 3-meter-diameter, variable-speed/variable-pitch, horizontal-axis wind turbines has been designed and analyzed theoretically. The two primary objectives of high maximum lift, relatively insensitive to roughness, and low profile drag have been achieved. The airfoils should exhibit docile stalls, which meet the design goal. The constraints on the pitching moment and the airfoils thicknesses have been satisfied.

  15. S830, S831, and S832 Airfoils: November 2001-November 2002

    Energy Technology Data Exchange (ETDEWEB)

    Somers, D. M.

    2005-08-01

    A family of quiet, thick, natural-laminar-flow airfoils, the S830, S831, and S832, for 40 - 50-meter-diameter, variable-speed/variable-pitch, horizontal-axis wind turbines has been designed and analyzed theoretically. The two primary objectives of high maximum lift, relatively insensitive to roughness, and low profile drag have been achieved. The airfoils should exhibit docile stalls, which meet the design goal. The constraints on the pitching moment and the airfoils thicknesses have been satisfied.

  16. Characteristics of Flow Field around NACA 0012 Airfoil with DBD plasma Actuator at Low Reynolds Number

    OpenAIRE

    簗瀬, 祐太; Yanase, Yuta; 大竹, 智久; Otake, Tomohisa; 村松, 旦典; Muramatsu, Akinori; 本橋, 龍郎; Motohashi, Tatsuo

    2012-01-01

    Aerodymamic performance of NACA0012 airfoil is enhanced with suppression of boundary layer separation due to operation of DBD plasma actuator at low Reynolds numbers. We carried out flow field measurements using hot-wire anemometer around the airfoil which applied to the actuator to investigate relationship between aerodynamics and flow field around the airfoil at Reymolds number of 10,000. Results of velocity profiles of the boundary layer show suppression of laminar separation on the airfoi...

  17. Investigation on Improved Correlation of CFD and EFD for Supercritical Airfoil

    OpenAIRE

    Xin Xu; Da-wei Liu; De-hua Chen; Zhi Wei; Yuan-jing Wang

    2014-01-01

    It is necessary to improve the correlation between CFD and EFD through the correction of EFD results and validation of CFD method, thus investigating the aerodynamic characteristics of supercritical airfoil perfectly. In this study, NASA SC (2) -0714 airfoil is numerically simulated and compared with NASA corrected experimental results to validate the CFD method. The Barnwell-Sewell method is applied to correct sidewall effects for experimental results of typical supercritical airfoil CH obta...

  18. Erosion--corrosion

    International Nuclear Information System (INIS)

    The deterioration of materials by corrosion or erosion by itself presents a formidable problem and for this reason investigators have studied these two phenomena independently. In fact, there are very few systematic studies on E-C and the majority of references mention it only in passing. In most real systems, however, the two destructive processes take place simultaneously, hence the purpose of this review is to present the various interactions between the chemical and mechanical agents leading to accelerated degradation of the material. The papers cited in the review are those that lead to a better understanding of the process involved in the accelerated rate of material loss under E-C conditions

  19. Documenting the global impacts of beach sand mining

    Science.gov (United States)

    Young, R.; Griffith, A.

    2009-04-01

    For centuries, beach sand has been mined for use as aggregate in concrete, for heavy minerals, and for construction fill. The global extent and impact of this phenomenon has gone relatively unnoticed by academics, NGOs, and major news sources. Most reports of sand mining activities are found at the very local scale (if the mining is ever documented at all). Yet, sand mining in many localities has resulted in the complete destruction of beach (and related) ecosystems along with severe impacts to coastal protection and tourism. The Program for the Study of Developed Shorelines at Western Carolina University and Beachcare.org have initiated the construction of a global database of beach sand mining activities. The database is being built through a combination of site visits and through the data mining of media resources, peer reviewed papers, and reports from private and governmental entities. Currently, we have documented sand mining in 35 countries on 6 continents representing the removal of millions of cubic meters of sand. Problems extend from Asia where critical infrastructure has been disrupted by sand mining to the Caribbean where policy reform has swiftly followed a highly publicized theft of sand. The Program for the Study of Developed Shorelines recently observed extensive sand mining in Morocco at the regional scale. Tens of kilometers of beach have been stripped of sand and the mining continues southward reducing hope of a thriving tourism-based economy. Problems caused by beach sand mining include: destruction of natural beaches and the ecosystems they protect (e.g. dunes, wetlands), habitat loss for globally important species (e.g. turtles, shorebirds), destruction of nearshore marine ecosystems, increased shoreline erosion rates, reduced protection from storms, tsunamis, and wave events, and economic losses through tourist abandonment and loss of coastal aesthetics. The threats posed by sand mining are made even more critical given the prospect of a

  20. Prediction of the Effect of Vortex Generators on Airfoil Performance

    DEFF Research Database (Denmark)

    Sørensen, Niels N.; Zahle, Frederik; Bak, Christian;

    2014-01-01

    different airfoils at a Reynolds number of 3 million, the FFA- W3-301 and FFA-W3-360, respectively. The computations are compared with wind tunnel measurements from the Stuttgart Laminar Wind Tunnel with respect to lift and drag variation as function of angle of attack. Even though the method does......Vortex Generators (VGs) are widely used by the wind turbine industry, to control the flow over blade sections. The present work describes a computational fluid dynamic procedure that can handle a geometrical resolved VG on an airfoil section. After describing the method, it is applied to two...... not exactly capture the measured performance, it can be used to compare different VG setups qualitatively with respect to chord- wise position, inter and intra-spacing and inclination of the VGs already in the design phase....

  1. Neural network analysis for erosion wear of nickel-aluminide coatings on steel by plasma spraying

    Science.gov (United States)

    Mishra, S. C.; Chaithanya, M.; Satapathy, Alok; Ananthapadmanabhan, P. V.; Sreekumar, K. P.

    2010-02-01

    In the present investigation plasma spray inter metallic coating of Nickel-aluminide was deposited on mild steel substrates. The response of plasma sprayed nickel-aluminide coatings to the impingement of such solid particles has been presented in this work. Nickel pre-mixed with alumina powder is deposited on mild steel substances by atmospheric plasma spraying at various operating power level. The coatings are subjected to erosion wear test. An erosion test setup developed in our laboratory is used to simulate real time erosive situations. Dry silica sand of average particle size 400 micron is used as the erodent. The erosion rate is calculated on the basis of 'coating mass losses. The erosion studies are made and different velocities and impingement angles. A computational technique (ANN analysis) is used to predict the rate of erosion wear under various operational conditions. This technique involves database training to predict property parameter evolutions in process having large number of interdependent variables. This paper presents the database construction, implementation protocol and also the set of predicted results related to the erosion wear rate of nickel-aluminide coating. It is shown that the erosion wear is strongly influenced by the angle of impact. The test is conducted at room temperature i.e.27°C and 60% RH. Ni3Al coatings deposited at different power levels (10, 12, 16, 20, 24 kW) are found to exhibit different wear rate under similar test conditions.

  2. Turbulent flow simulation of the NREL S809 airfoil

    Energy Technology Data Exchange (ETDEWEB)

    Guerri, Ouahiba; Bouhadef, Khadidja; Harhad, Ameziane

    2006-05-15

    Numerical computations are carried out for the NREL S809 airfoil. The flow is modelled using an unsteady incompressible Reynolds Averaged Navier-Stokes solver. Two turbulence models (SST {kappa}/{omega}of Menter and RNG {kappa}/{epsilon}) are applied to close the RANS equations. All computations are performed assuming fully turbulent flow. The flow field is analyzed at various angles of attack from 0 to 20 degrees. Lift and drag forces are obtained from the computations by integrating the pressure and shear stress over the blade surface. The performance of the two turbulence models is compared and the influence of the free stream turbulence intensity is checked. The results confirm the satisfactory performance of the SST {kappa}/{omega} model of Menter for modelling turbulent flow around airfoils. (author)

  3. Susceptibility of coarse-textured soils to soil erosion by water in the tropics

    International Nuclear Information System (INIS)

    The application of soil physics for the evaluation of factors of soil erosion in the tropics received considerable attention in the last four decades. In Nigeria, physical characteristics of rainfall such as drop size and drop-size distribution, rainfall intensity at short intervals and kinetic energy of rainfall were evaluated using different methods. Thus, compound erosivity indices were evaluated which showed a similar trend in annual rainfall erosivity with annual rainfall amounts. Attempts have also been made to use geostatistical tools and fractal theory to describe temporal variability in rainfall erosivity. High erosivity aggravates the vulnerability of coarse-textured soils to erosion. These soils, high in sand content were poorly aggregated and structurally weak. Thus, they were easily detached and transported by runoff. Long-term data are needed to describe factors of soil erosion in the tropics but quite often, equipment are not available or poorly maintained where available such that useful data are not collected. A greater cooperation of pure physicists, soil physicists and engineers in the developing nations is needed to improve or design equipment and methods for the characterization of factors of soil erosion in the tropics. (author)

  4. Airfoil for a turbine of a gas turbine engine

    Science.gov (United States)

    Liang, George

    2010-12-21

    An airfoil for a turbine of a gas turbine engine is provided. The airfoil comprises a main body comprising a wall structure defining an inner cavity adapted to receive a cooling air. The wall structure includes a first diffusion region and at least one first metering opening extending from the inner cavity to the first diffusion region. The wall structure further comprises at least one cooling circuit comprising a second diffusion region and at least one second metering opening extending from the first diffusion region to the second diffusion region. The at least one cooling circuit may further comprise at least one third metering opening, at least one third diffusion region and a fourth diffusion region.

  5. Oil sands development update

    International Nuclear Information System (INIS)

    A detailed review and update of oil sands development in Alberta are provided covering every aspect of the production and economic aspects of the industry. It is pointed out that at present oil sands account for 28 per cent of Canadian crude oil production, expected to reach 50 per cent by 2005. Based on recent announcements, a total of 26 billion dollars worth of projects are in progress or planned; 20 billion dollars worth of this development is in the Athabasca area, the remainder in Cold Lake and other areas. The current update envisages up to 1,800,000 barrels per day by 2008, creating 47,000 new jobs and total government revenues through direct and indirect taxes of 118 billion dollars. Provinces other than Alberta also benefit from these development, since 60 per cent of all employment and income created by oil sands production is in other parts of Canada. Up to 60 per cent of the expansion is for goods and services and of this, 50 to 55 per cent will be purchased from Canadian sources. The remaining 40 per cent of the new investment is for engineering and construction of which 95 per cent is Canadian content. Aboriginal workforce by common consent of existing operators matches regional representation (about 13 per cent), and new developers are expected to match these standards. Planned or ongoing development in environmental protection through improved technologies and optimization, energy efficiency and improved tailings management, and active support of flexibility mechanisms such as emission credits trading, joint implementation and carbon sinks are very high on the industry's agenda. The importance of offsets are discussed extensively along with key considerations for international negotiations, as well as further research of other options such as sequestration, environmentally benign disposal of waste, and enhanced voluntary action

  6. Dune erosion during storm surges

    NARCIS (Netherlands)

    Van Thiel de Vries, J.S.M.

    2009-01-01

    Large parts of The Netherlands are protected from flooding by a narrow strip of sandy beaches and dunes. The aim of this thesis is to extend the existing knowledge of dune erosion during storm surges as it occurs along the Dutch coast. The thesis discusses: • A large scale dune erosion experiment to

  7. Dune erosion under climate change

    NARCIS (Netherlands)

    de Winter, R.C.

    2014-01-01

    This PhD-thesis investigated the effect of future climate change on dune erosion in the Netherlands. At present, dune erosion occurs under a combination of large storm surge and high waves, which are both generated by a storm event. Therefore to investigate the affect of future climate change on dun

  8. Erosion of magnesium potassium phosphate ceramic waste forms.

    Energy Technology Data Exchange (ETDEWEB)

    Goretta, K. C.

    1998-11-20

    Phosphate-based chemically bonded ceramics were formed from magnesium potassium phosphate (MKP) binder and either industrial fly ash or steel slag. The resulting ceramics were subjected to solid-particle erosion by a stream of either angular Al{sub 2}O{sub 3} particles or rounded SiO{sub 2} sand. Particle impact angles were 30 or 90{degree} and the impact velocity was 50 m/s. Steady-state erosion rates, measured as mass lost from a specimen per mass of impacting particle, were dependent on impact angle and on erodent particle size and shape. Material was lost by a combination of fracture mechanisms. Evolution of H{sub 2}O from the MKP phase appeared to contribute significantly to the material loss.

  9. Sand Storms Trigger Alarm

    Institute of Scientific and Technical Information of China (English)

    LI LI

    2010-01-01

    @@ After an unusually humid winter with at least 10 snowfalls in Beijing, a severe andstorm blown by strong winds bringing with it thousands of tons of desert sand took many residents of the city by surprise.On the morning of March 20, Beijingers woke up to see clouds of yellow dust in the air and a sky that was an ominous orange in color.The loose soil and dust that had traveled htmdreds of miles from deserts in Mongolia and China's northwest blanketed Beijing's streets, covering parked vehicles, bikes, roofs and even plant life,as well as making its way into people's homes.

  10. Fortune Cookie Sand Dunes

    Science.gov (United States)

    2003-01-01

    MGS MOC Release No. MOC2-432, 25 July 2003This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a field of small barchan sand dunes in the north polar region near 71.7oN, 51.3oW. Some of them are shaped like fortune cookies. The message these dunes provide: winds blow through this region from the lower right toward the upper left. The steep slip face slopes of these dunes, which point toward the upper left, indicate the wind direction. The scene is illuminated by sunlight from the upper right. The image is 3 km (1.9 mi) wide.

  11. Design, Simulation, and Wind Tunnel Verication of a Morphing Airfoil

    OpenAIRE

    Gustafson, Eric Andrew

    2011-01-01

    The application of smart materials to control the flight dynamics of a Micro Air Vehicle (MAV) has numerous benefits over traditional servomechanisms. Under study is wing morphing achieved through the use of piezoelectric Macro Fiber Composites (MFCs). These devices exhibit low power draw but excellent bandwidth characteristics. This thesis provides a background in the 2D analytical and computer modeling tools and methods needed to design and characterize an MFC-actuated airfoil. A com...

  12. Characterization of the Flow Separation of a Variable Camber Airfoil

    Institute of Scientific and Technical Information of China (English)

    YANG Wen-Chao; WANG Hui; YANG Jian-Ting; YANG Ji-Ming

    2012-01-01

    An experimental investigation is carried out to study the How separation behaviors of a variable camber airfoil. The aerodynamic load measurements and related flow visualization show that there are two types of stalls caused by the deformation on the camber: the leading-edge stall and the trailing-edge stall. Static measurements of aerodynamic force show a drastic leading-edge stall, while the serial measurements on an airfoil with camber deformation illustrate a trailing-edge stall and gradual bending-over on the aerodynamic coefficient curve. Under flow separation circumstances, the Bow structure is related not only to current boundary conditions, but also the previous flow characteristics, so the quasi-steady aerodynamic characteristics are significantly distinct from those of the static measurements.%An experimental investigation is carried out to study the flow separation behaviors of a variable camber airfoil.The aerodynamic load measurements and related flow visualization show that there are two types of stalls caused by the deformation on the camber:the leading-edge stall and the trailing-edge stall.Static measurements of aerodynamic force show a drastic leading-edge stall,while the serial measurements on an airfoil with camber deformation illustrate a trailing-edge stall and gradual bending-over on the aerodynamic coefficient curve.Under flow separation circumstances,the flow structure is related not only to current boundary conditions,but also the previous flow characteristics,so the quasi-steady aerodynamic characteristics are significantly distinct from those of the static measurements.

  13. Turbine Airfoil Leading Edge Film Cooling Bibliography: 1972–1998

    OpenAIRE

    Kercher, D. M.

    2000-01-01

    Film cooling for turbine airfoil leading edges has been a common practice for at least 35 years as turbine inlet gas temperatures and pressures have continually increased along with cooling air temperatures for higher engine cycle efficiency. With substantial engine cycle performance improvements from higher gas temperatures, it has become increasingly necessary to film cool nozzle and rotor blade leading edges since external heat transfer coefficients and thus heat load are the highest in th...

  14. Turbine blade having a constant thickness airfoil skin

    Science.gov (United States)

    Marra, John J

    2012-10-23

    A turbine blade is provided for a gas turbine comprising: a support structure comprising a base defining a root of the blade and a framework extending radially outwardly from the base, and an outer skin coupled to the support structure framework. The skin has a generally constant thickness along substantially the entire radial extent thereof. The framework and the skin define an airfoil of the blade.

  15. Numerical Investigation of Flow Control by Suction and Injection on a Subsonic Airfoil

    OpenAIRE

    M. H. Shojaefard; A. R. Noorpoor; A. Avanesians; M. Ghaffarpour

    2005-01-01

    This study presents a numerical study concerning flow control by suction and injection. The case studied is the flow field over a subsonic airfoil with four suction and injection slots on the suction side of the airfoil. Five different angles of attack, 0, 5, 10, 13.3 and 20 with the Mach number of 0.15 are studied. Three cases are studied in each angle of attack. The three cases are airfoil with surface suction, surface injection and the base airfoil. A commercial CFD code, the FLUENT, is us...

  16. Design and Wind Tunnel Testing of a Thick, Multi-Element High-Lift Airfoil

    DEFF Research Database (Denmark)

    Zahle, Frederik; Gaunaa, Mac; Sørensen, Niels N.;

    2012-01-01

    In this work a 2D CFD solver has been used to optimize the shape of a leading edge slat with a chord length of 30% of the main airfoil which was 40% thick. The airfoil configuration was subsequently tested in a wind tunnel and compared to numerical predictions. The multi-element airfoil...... was predicted to achieve a Cl−max of 3.1 based on the main airfoil chord length, which was confirmed in the wind tunnel campaign. Using wake rake traversal and wool tuft flow visualization wall interference effects were investigated, which were found to be a source of considerable uncertainty when measuring...

  17. Some practical issues in the computational design of airfoils for the helicopter main rotor blades

    Directory of Open Access Journals (Sweden)

    Kostić Ivan

    2004-01-01

    Full Text Available Very important requirement for the helicopter rotor airfoils is zero, or nearly zero moment coefficient about the aerodynamic center. Unlike the old technologies used for metal blades, modern production involving application of plastic composites has imposed the necessity of adding a flat tab extension to the blade trailing edge, thus changing the original airfoil shape. Using computer program TRANPRO, the author has developed and verified an algorithm for numerical analysis in this design stage, applied it on asymmetrical reflex camber airfoils, determined the influence of angular tab positioning on the moment coefficient value and redesigned some existing airfoils to include properly positioned tabs that satisfy very low moment coefficient requirement. .

  18. Validation of the CQU-DTU-LN1 series of airfoils

    DEFF Research Database (Denmark)

    Shen, Wen Zhong; Zhu, Wei Jun; Fischer, Andreas;

    2014-01-01

    The CQU-DTU-LN1 series of airfoils were designed with an objective of high lift and low noise emission. In the design process, the aerodynamic performance is obtained using XFOIL while noise emission is obtained with the BPM model. In this paper we present some validations of the designed CQU......, the designed Cl and Cl/Cd agrees well with the experiment and are in general higher than those of the NACA airfoil. For the acoustic features, the noise emission of the LN118 airfoil is compared with the acoustic measurements and that of the NACA airfoil. Comparisons show that the BPM model can predict...

  19. Design of the wind turbine airfoil family RISOe-A-XX

    Energy Technology Data Exchange (ETDEWEB)

    Dahl, K.S.; Fuglsang, P.

    1998-12-01

    A method for design of wind turbine airfoils is presented. The design method is based on direct numerical optimization of a B-spline representation of the airfoil shape. For flexibility, the optimization algorithm relies on separate, stand alone tools for the analysis of aerodynamic and structural properties. The panel method based XFOIL is used during the optimization whereas the Navier-Stokes solver EllipSys2D is used in the evaluation of the results. The method is demonstrated by the design of an airfoil family composed of 7 airfoils ranging in thickness from 12% to 30%. The design is based on Reynolds and Mach numbers representative of a 600 kW wind turbine. The airfoils are designed to have maximum lift-drag ratio until just below stall, a design lift coefficient of about 1.55 at an angle of attack of 10 deg. and a maximum lift coefficient of 1.65. The airfoils are made insensitive to leading edge roughness by securing that transition from laminar to turbulent flow on the suction side occurs close to the leading edge for post stall angles of attack. The design method and the airfoil family provides a sound basis for further enhancing the characteristics of airfoils for wind turbines and to tailor airfoils for specific rotor sizes and power regulation principles. (au) EFP-95. 3 tabs., 24 ills., 31 refs.

  20. Compressive behavior of fine sand.

    Energy Technology Data Exchange (ETDEWEB)

    Martin, Bradley E. (Air Force Research Laboratory, Eglin, FL); Kabir, Md. E. (Purdue University, West Lafayette, IN); Song, Bo; Chen, Wayne (Purdue University, West Lafayette, IN)

    2010-04-01

    The compressive mechanical response of fine sand is experimentally investigated. The strain rate, initial density, stress state, and moisture level are systematically varied. A Kolsky bar was modified to obtain uniaxial and triaxial compressive response at high strain rates. A controlled loading pulse allows the specimen to acquire stress equilibrium and constant strain-rates. The results show that the compressive response of the fine sand is not sensitive to strain rate under the loading conditions in this study, but significantly dependent on the moisture content, initial density and lateral confinement. Partially saturated sand is more compliant than dry sand. Similar trends were reported in the quasi-static regime for experiments conducted at comparable specimen conditions. The sand becomes stiffer as initial density and/or confinement pressure increases. The sand particle size become smaller after hydrostatic pressure and further smaller after dynamic axial loading.

  1. Combat erosion prone conditions with biotic growth mediums

    Energy Technology Data Exchange (ETDEWEB)

    Anon.

    2009-10-01

    This article discussed methods of preserving soils in order to support remediation activities at 2 sites with sandy subsoil conditions and a lack of organic materials. An advanced hydroseeding technology was used to control erosion at the sites. Biotic Earth is a wheat straw-based hydromulch mixed with peat moss. The straw is used as an erosion control material, while the peat moss is used as an organic addition to the soil. Biotic Earth was applied at a site near James Bay where topsoil could not be salvaged. The aim of the project was to establish vegetation within a single season without the use of topsoil. The product was also used to combat the erosion challenges at a wastewater lagoon development in Manitoba that involved the protection of 70,000 m{sup 2} of eroded slopes and channels that threatened to undermine the lagoon structure. Vegetation was established on the sand beams surrounding the lagoon. Erosion control blankets were used to kick-start vegetation growth. The specialized hydroseeding proposal was selected as the lowest cost option among several alternatives. It was concluded that vegetation growth in the region was rapid and consistent through the planted areas. 12 figs.

  2. Negative feedback between stress and erosion: origin of sandstone landforms

    Science.gov (United States)

    Bruthans, Jiri; Soukup, Jan; Vaculikova, Jana; Filippi, Michal; Schweigstillova, Jana; Mayo, Alan; Masin, David; Kletetschka, Gunther; Rihosek, Jaroslav

    2015-04-01

    Weathering and erosion of sandstone produces spectacular landforms such as arches, alcoves, pedestal rocks and pillars. The effect of gravity loading stress has been overlooked or assumed to increase the landform's weathering rate. Here we show by physical and numerical modeling, and field observations of locked sands and sandstones that an increase in stress within the landform reduces weathering and erosion. Material with insufficient loading is rapidly removed by weathering process and the remaining load bearing landform structure is protected by the fabric interlocking mechanism. As the landform evolves the increased stress inhibits erosion from raindrop impact, flowing water and slaking, and retards surface retreat caused by salt and frost weathering. Planar discontinuities in sandstone and negative feedback between stress and weathering/erosion processes are sufficient conditions to create above-mentioned landforms. Our experiments are able to reproduce natural shapes including arches, alcoves, pedestal rocks and pillars using landform material and mimicking natural processes. The proposed negative feedback mechanism is supported by a numerical model of stress pattern in landforms. We conclude that stress field is the primary control of the shape evolution of sandstone landforms.

  3. Airfoil profile drag increase due to acoustic excitation

    Science.gov (United States)

    Shearin, John G.; Jones, Michael G.

    1989-04-01

    A two-dimensional airfoil (NACA-0009) is subjected to high intensity pure-tone sound over a 1-5 kHz frequency range while immersed in a flow with 240 ft/sec velocity in a quiet flow facility with a Reynolds number of 3 million. Wake dynamic pressures are determined, and the momentum deficit is used to calculate a two-dimensional drag coefficient. Significant increases in drag are observed when the airfoil is subjected to high-intensity sound at critical frequencies. The increased drag is accompanied by movement of the natural transition location. When the transition is fixed by roughness at 10 percent chord, no further transition movement is observed in response to an acoustic Tollmien-Schlichting disturbance. However, a 4 percent increase in the sectional drag coefficient is noted. It is believed to be due to the sound exciting the flow near the airfoil surface (shear layer), thus causing the existing turbulence to become more intense, possess a higher mixing rate (momentum), and increase the skin friction.

  4. Simulasi Numerik Dynamic Stall Pada Airfoil Yang Berosilasi

    Directory of Open Access Journals (Sweden)

    Galih S.T.A. Bangga

    2012-09-01

    Full Text Available Kebutuhan analisa pada sudu helikopter, kompresor, kincir angin dan struktur streamline lainya yang beroperasi pada angle of attack yang tinggi dan melibatkan instationary effects yang disebut dynamic stall menjadi semakin penting. Fenomena ini ditandai dengan naiknya dynamic lift melewati static lift maksimum pada critical static stall angle, vortex yang terbentuk pada leading edge mengakibatkan naiknya suction contribution yang kemudian terkonveksi sepanjang permukaan hingga mencapai trailling edge diikuti terbentuknya trailling edge vortex yang menunjukkan terjadinya lift stall. Fenomena ini sangat berbahaya terhadap struktur airfoil itu sendiri. Secara umum, beban fatique yang ditimbulkan oleh adanya efek histerisis karena fluktuasi gaya lift akibat induksi vibrasi lebih besar dibandingkan kondisi statis. Simulasi numerik dilakukan secara 2D dengan menggunakan profil Boeing-Vertol V23010-1.58 pada α0 = 14.92°. Standard-kω dan SST-kω digunakan sebagai URANS turbulence modelling. Model osilasi dari airfoil disusun dalam suatu user defined function (UDF. Gerakan meshing beserta airfoil diakomodasi dengan menggunakan dynamic mesh approach. Simulasi numerik menunjukkan bahwa, model SST-kω menunjukkan performa yang lebih baik dibandingkan dengan Standard-kω. Fenomena travelling vortex yang terjadi mampu ditangkap dengan baik, meski pada angle of attack yang tinggi URANS turbulence model gagal memprediksikan fenomena yang terjadi karena dominasi efek 3D.

  5. Flow control at low Reynolds numbers using periodic airfoil morphing

    Science.gov (United States)

    Jones, Gareth; Santer, Matthew; Papadakis, George; Bouremel, Yann; Debiasi, Marco; Imperial-NUS Joint PhD Collaboration

    2014-11-01

    The performance of airfoils operating at low Reynolds numbers is known to suffer from flow separation even at low angles of attack as a result of their boundary layers remaining laminar. The lack of mixing---a characteristic of turbulent boundary layers---leaves laminar boundary layers with insufficient energy to overcome the adverse pressure gradient that occurs in the pressure recovery region. This study looks at periodic surface morphing as an active flow control technique for airfoils in such a flight regime. It was discovered that at sufficiently high frequencies an oscillating surface is capable of not only reducing the size of the separated region---and consequently significantly reducing drag whilst simultaneously increasing lift---but it is also capable of delaying stall and as a result increasing CLmax. Furthermore, by bonding Macro Fiber Composite actuators (MFCs) to the underside of an airfoil skin and driving them with a sinusoidal frequency, it is shown that this control technique can be practically implemented in a lightweight, energy efficient way. Imperial-NUS Joint Ph.D. Programme.

  6. Dilatometric Characterization of Foundry Sands

    Directory of Open Access Journals (Sweden)

    M. Břuska

    2012-04-01

    Full Text Available The goal of this contribution is summary of physical – chemistry properties of usually used foundry silica and no – silica sands in Czech foundries. With the help of dilatometry analysis theoretical assumptions of influence of grain shape and size on dilatation value of sands were confirmed. Determined was the possibility of dilatometry analysis employment for preparing special (hybrid sands with lower and/or more linear character of dilatation.

  7. Impacts of sand and dust storms on agriculture and potential agricultural applications of a SDSWS

    Science.gov (United States)

    Stefanski, R.; Sivakumar, M. V. K.

    2009-03-01

    This paper will give an overview of the various impacts of sand and dust storms on agriculture and then address the potential applications of a Sand and Dust Storm Warning System (SDSWS) for agricultural users. Sand and dust storms have many negative impacts on the agricultural sector including: reducing crop yields by burial of seedlings under sand deposits, the loss of plant tissue and reduced photosynthetic activity as a result of sandblasting, delaying plant development, increasing end-of-season drought risk, causing injury and reduced productivity of livestock, increasing soil erosion and accelerating the process of land degradation and desertification, filling up irrigation canals with sediments, covering transportation routes, affecting water quality of rivers and streams, and affecting air quality. One positive impact is the fertilization of soil minerals to terrestrial ecosystems. There are several potential agricultural applications of a SDSWS. The first is to alert agricultural communities farmers to take preventive action in the near-term such as harvesting maturing crops (vegetables, grain), sheltering livestock, and strengthening infrastructure (houses, roads, grain storage) for the storm. Also, the products of a SDSWS could be used in for monitoring potential locust movement and post-storm crop damage assessments. An archive of SDSWS products (movement, amount of sand and dust) could be used in researching plant and animal pathogen movement and the relationship of sand and dust storms to disease outbreaks and in developing improved soil erosion and land degradation models.

  8. Soil physical properties affecting soil erosion in tropical soils

    International Nuclear Information System (INIS)

    detachment. Studies on necessary kinetic energy to detach one kilogram of sediments by raindrop impact have shown that the minimum energy is required for particles of 0.125 mm. Particles between 0.063 to 0.250 mm are the most vulnerable to detachment. This means that soils with high content of particles into vulnerable range, for example silty loam, loamy, fine sandy, and sandy loam are the most susceptible soils to detachment. Many aspects of soil behaviour in the field such as hydraulic conductivity water retention, soil crusting, soil compaction, and workability are influenced strongly by the primary particles. In tropical soils also a negative relation between structure stability and particles of silt, fine sand and very fine sand has been found, this is attributed to low cohesiveness of these particles. The ability of a structure to persist is known as its stability. There are two principal types of stability: the ability of the soil to retain its structure under the action of water, and the ability of the soil to retain its structure under the action of external mechanical stresses. (e.g. by wheels). Both types of stability are related with susceptibility to erosion

  9. Using REE Tracers to Measure Sheet Erosion Changing to Rill Erosion

    Institute of Scientific and Technical Information of China (English)

    宋炜; 刘普灵; 杨明义; 薛亚洲

    2003-01-01

    Rare earth element(REE) tracer method was used to study sheet erosion changing to rill erosion on slope land. By placing different REE on different soil depth across a slope in an indoor plot, two simulated rainfalls were applied to study the change of erosion type and the rill erosion process. The results indicate that the main erosion type is sheet erosion at the beginning of the rainfalls, and serious erosion happens after rill erosion appears. Accumulated sheet and rill erosion amount increases with the rainfalls time. The percentage of sheet erosion amount decreases and rill erosion percentage increases with time. At the end of the rainfalls, the total rill erosion amounts are 4.3 and 5 times more than sheet erosion. In this paper, a new REE tracer method was used to quantitatively distinguish sheet and rill erosion amount. The new REE tracer method should be useful to future studying of erosion processes on slope lands.

  10. Comparison of methods for calculating water erosion

    OpenAIRE

    Svobodová, Pavlína

    2011-01-01

    Bachelor thesis presents a comparison of methods for calculating water erosion. The aim is to summarize available evidence concerning the problems of water erosion. There are presented some methods how to calculate average annual erosion of soils, and selected models for calculating the erosion immediately. There are also listed possible erosion control measures through which we can at least slow the effects of erosion, rather than stop completely.

  11. Modeling soil erosion in a watershed

    OpenAIRE

    Lanuza, R.

    1999-01-01

    Most erosion models have been developed based on a plot scale and have limited application to a watershed due to the differences in aerial scale. In order to address this limitation, a GIS-assisted methodology for modeling soil erosion was developed using PCRaster to predict the rate of soil erosion at watershed level; identify the location of erosion prone areas; and analyze the impact of landuse changes on soil erosion. The general methodology of desktop modeling or soil erosion at watershe...

  12. Russian Laminar Flow Airfoils 3rd Part: Measurements on the Profile No. 2315 BIS with Ava-Nose Flap

    Science.gov (United States)

    Riegels, F.

    1947-01-01

    The tests on the Russian airfoil 2315 Bis were continued. This airfoil shows, according to Moscow tests, good laminar flow characteristics. Several tests were prepared in the large wind tunnel at Gottingen; partial results were obtained.

  13. Thick airfoil designs for the root of the 10MW INNWIND.EU wind turbine

    Science.gov (United States)

    Mu≁oz, A.; Méndez, B.; Munduate, X.

    2016-09-01

    The main objective of the “INNWIND.EU” project is to investigate and demonstrate innovative designs for 10-20MW offshore wind turbines and their key components, such as lightweight rotors. In this context, the present paper describes the development of two new airfoils for the blade root region. From the structural point of view, the root is the region in charge of transmitting all the loads of the blade to the hub. Thus, it is very important to include airfoils with adequate structural properties in this region. The present article makes use of high-thickness and blunt trailing edge airfoils to improve the structural characteristics of the airfoils used to build this blade region. CENER's (National Renewable Energy Center of Spain) airfoil design tool uses the airfoil software XFOIL to compute the aerodynamic characteristics of the designed airfoils. That software is based on panel methods which show some problems with the calculation of airfoils with thickness bigger than 35% and with blunt trailing edge. This drawback has been overcome with the development of an empirical correction for XFOIL lift and drag prediction based on airfoil experiments. From the aerodynamic point of view, thick airfoils are known to be very sensitive to surface contamination or turbulent inflow conditions. Consequently, the design optimization takes into account the aerodynamic torque in both clean and contaminated conditions. Two airfoils have been designed aiming to improve the structural and the aerodynamic behaviour of the blade in clean and contaminated conditions. This improvement has been corroborated with Blade Element Momentum (BEM) computations.

  14. Holocene sand shoals offshore of Mississippi River delta plain, Louisiana

    Energy Technology Data Exchange (ETDEWEB)

    Penland, S.; McBride, R.A. (Louisiana Geological Survey, Baton Rouge (USA)); Suter, J.R. (Exxon Production Research, Houston, TX (USA)); Williams, S.J. (Geological Survey, Reston, VA (USA)); Kindinger, J.L. (Geological Survey, St. Petersburg, FL (USA)); Boyd, R. (Dalhousie Univ., Halifax, Nova Scotia (Canada))

    1989-09-01

    Offshore of the Mississippi River delta plain lies a series of Holocene sand shoals marking the position of ancient submerged shorelines. These ancient shorelines represent stillstand positions during which the Holocene transgression drove sea level across the former lowstand subaerial erosion surface of the Mississippi River delta plain. Short periods of rapid sea level rise led to the transgressive submergence of these sandy shorelines. Two shoreline trends can be recognized at the {minus}10-m and {minus}20-m isobaths on the continental shelf.

  15. Rapid erosion of the coast of Sagar island, West Bengal - India

    Science.gov (United States)

    Gopinath, Girish; Seralathan, P.

    2005-10-01

    The coastal zone of the Sagar island has been studied. The island has been subjected to erosion by natural processes and to a little extent by anthropogenic activities over a long period. Major landforms identified in the coastal area of the Sagar island are the mud flats/salt marshes, sandy beaches/dunes and mangroves. The foreshore sediments are characterized by silty, slightly sandy mud, slightly silty sand and silty sand. Samples 500 m inland from high waterline are silty slightly sandy mud, and by clayey slightly sandy mud. The extent of coastline changes are made by comparing the topographic maps of 1967 and satellite imageries of 1996, 1998 and 1999. Between 1967 and 1999 about 29.8 km2 of the island has been eroded and the accreted area is only 6.03 km2. Between 1996 and 1998 the area underwent erosion of 13.64 km2 while accretion was 0.48 km2. From 1998 to 1999, 3.26 km2 additional area was eroded with meager accretion. Erosion from 1997 to 1999 was estimated at 0.74 km2 /year; however, from 1996 to 1999, the erosion rate was calculated as 5.47 km2/year. The areas severely affected by erosion are the northeastern, southwestern and southeastern faces of the island. As a consequence of coastal erosion, the mud flats/salt marshes, sandy beaches/dunes and mangroves have been eroded considerably. Deposition is experienced mainly on the western and southern part of the island. The island is built primarily by silt and clay, which can more easily be eroded by the waves, tides and cyclonic activities than a sandy coast. Historic sea level rises accompanied by land subsidence lead to differing rates of erosion at several pockets, thus periodically establishing new erosion planes.

  16. Coastal geology and recent origins for Sand Point, Lake Superior

    Science.gov (United States)

    Fisher, Timothy G.; Krantz, David E.; Castaneda, Mario R.; Loope, Walter L.; Jol, Harry M.; Goble, Ronald J.; Higley, Melinda C.; DeWald, Samantha; Hansen, Paul

    2014-01-01

    Sand Point is a small cuspate foreland located along the southeastern shore of Lake Superior within Pictured Rocks National Lakeshore near Munising, Michigan. Park managers’ concerns for the integrity of historic buildings at the northern periphery of the point during the rising lake levels in the mid-1980s greatly elevated the priority of research into the geomorphic history and age of Sand Point. To pursue this priority, we recovered sediment cores from four ponds on Sand Point, assessed subsurface stratigraphy onshore and offshore using geophysical techniques, and interpreted the chronology of events using radiocarbon and luminescence dating. Sand Point formed at the southwest edge of a subaqueous platform whose base is probably constructed of glacial diamicton and outwash. During the post-glacial Nipissing Transgression, the base was mantled with sand derived from erosion of adjacent sandstone cliffs. An aerial photograph time sequence, 1939–present, shows that the periphery of the platform has evolved considerably during historical time, infl uenced by transport of sediment into adjacent South Bay. Shallow seismic refl ections suggest slump blocks along the leading edge of the platform. Light detection and ranging (LiDAR) and shallow seismic refl ections to the northwest of the platform reveal large sand waves within a deep (12 m) channel produced by currents fl owing episodically to the northeast into Lake Superior. Ground-penetrating radar profi les show transport and deposition of sand across the upper surface of the platform. Basal radiocarbon dates from ponds between subaerial beach ridges range in age from 540 to 910 cal yr B.P., suggesting that Sand Point became emergent during the last ~1000 years, upon the separation of Lake Superior from Lakes Huron and Michigan. However, optically stimulated luminescence (OSL) ages from the beach ridges were two to three times as old as the radiocarbon ages, implying that emergence of Sand Point may have begun

  17. Buffer erosion in dilute groundwater

    International Nuclear Information System (INIS)

    One scenario of interest for repository safety assessment involves the loss of bentonite buffer material in contact with dilute groundwater flowing through a transmissive fracture interface. In order to examine the extrusion/erosion behavior of bentonite buffer material under such circumstances, a series of experiments were performed in a flow-through, 1 mm aperture, artificial fracture system. These experiments covered a range of solution chemistry (salt concentration and composition), material composition (sodium montmorillonite and admixtures with calcium montmorillonite), and flow velocity conditions. No erosion was observed for sodium montmorillonite against solution compositions from 0.5 g/L to 10 g/L NaCl. No erosion was observed for 50/50 calcium/sodium montmorillonite against 0.5 g/L NaCl. Erosion was observed for both sodium montmorillonite and 50/50 calcium/sodium montmorillonite against solution compositions ≤ 0.25 g/L NaCl. The calculated erosion rates for the tests with the highest levels of measured erosion, i.e., the tests run under the most dilute conditions (ionic strength (IS) < ∼1 mM), were well-correlated to flow velocity, whereas the calculated erosion rates for the tests with lower levels of measured erosion, i.e., the tests run under somewhat less dilute conditions (∼1 mM < IS < ∼4 mM), were not similarly correlated indicating that material and solution composition can significantly affect erosion rates. In every experiment, both erosive and non-erosive, emplaced buffer material extruded into the fracture and was observed to be impermeable to water flowing in the fracture effectively forming an extended diffusive barrier around the intersecting fracture/buffer interface. Additionally, a model which was developed previously to predict the rate of erosion of bentonite buffer material in low ionic strength water in rock fracture environments was applied to three different cases: sodium montmorillonite expansion in a vertical tube, a

  18. Cavitation erosion size scale effects

    Science.gov (United States)

    Rao, P. V.; Buckley, D. H.

    1984-01-01

    Size scaling in cavitation erosion is a major problem confronting the design engineers of modern high speed machinery. An overview and erosion data analysis presented in this paper indicate that the size scale exponent n in the erosion rate relationship as a function of the size or diameter can vary from 1.7 to 4.9 depending on the type of device used. There is, however, a general agreement as to the values of n if the correlations are made with constant cavitation number.

  19. The Influence of Ephemeral Beaches on Alongshore Variability of Hard-rock Cliff Erosion

    Science.gov (United States)

    Vann Jones, E. C.; Rosser, N. J.; Brain, M.; Varley, S. J.

    2015-12-01

    The role of abrasion of rock cliffs is typically considered in the long-term presence of a beach. During monthly monitoring of hard rock cliff erosion along the North Yorkshire coast, UK, we have observed a number of small ephemeral beaches of highly variable duration and extent. The erosive significance of the temporary presence of sediment at the cliffs is unknown and we set out to examine whether observed alongshore variability in erosion can be linked to the presence of ephemeral beaches. We explore the temporal and spatial variability in sediment deposition and transport along a low-sediment rock coast foreshore, the controlling marine conditions and the effects on cliff erosion. We focus on a 500 m wide embayment set into 70 m high hard rock cliffs consisting of horizontally bedded Jurassic mudstone, shale, siltstone and sandstone. The bay has a wide, shallow gradient foreshore up to 300 m wide with highly variable topography. With the exception of an ephemeral beach (of widths up to approximately 150 m alongshore and 10 m cross-shore) the rock foreshore is typically sand-free, with failed material from the cliffs quickly removed from the cliff toe by the sea leaving only boulders. The high tidal range (6 m) and storm wave environment of the North Sea result in variable marine conditions at the site. We use magnetic sand tracers and a grid of foreshore and cliff face magnets to examine the sand transport across the foreshore and to identify the vertical extent of cliff face impacted by sand. We monitor the driving marine conditions on the foreshore using a network of current meters and wave pressure sensors. Erosion of the cliff face across the whole bay is monitored at high-resolution using terrestrial laser scanning to examine the spatial distribution of abrasion and the influence of the ephemeral beach.

  20. Testing and prediction of erosion-corrosion for corrosion resistant alloys used in the oil and gas production industry

    Science.gov (United States)

    Rincon, Hernan E.

    The corrosion behavior of CRAs has been thoroughly investigated and documented in the public literature by many researchers; however, little work has been done to investigate erosion-corrosion of such alloys. When sand particles are entrained in the flow, the degradation mechanism is different from that observed for sand-free corrosive environment. There is a need in the oil and gas industry to define safe service limits for utilization of such materials. The effects of flow conditions, sand rate, pH and temperature on the erosion-corrosion of CRAs were widely studied. An extensive experimental work was conducted using scratch tests and flow loop tests using several experimental techniques. At high erosivity conditions, a synergistic effect between erosion and corrosion was observed. Under the high sand rate conditions tested, erosivity is severe enough to damage the passive layer protecting the CRA thereby enhancing the corrosion rate. In most cases there is likely a competition between the rates of protective film removal due to mechanical erosion and protective film healing. Synergism occurs for each of the three alloys examined (13Cr and Super13Cr and 22Cr); however, the degree of synergism is quite different for the three alloys and may not be significant for 22Cr for field conditions where erosivities are typically much lower that those occurring in the small bore loop used in this research. Predictions of the corrosion component of erosion-corrosion based on scratch test data compared reasonably well to test results from flow loops for the three CRAs at high erosivity conditions. Second order behavior appears to be an appropriate and useful model for representing the repassivation process of CRAs. A framework for a procedure to predict penetration rates for erosion-corrosion conditions was developed based on the second order model behavior observed for the re-healing process of the passive film of CRAs and on computational fluid dynamics (CFD) simulations

  1. Sand swimming lizard: sandfish

    CERN Document Server

    Maladen, Ryan D; Kamor, Adam; Goldman, Daniel I

    2009-01-01

    We use high-speed x-ray imaging to reveal how a small (~10cm) desert dwelling lizard, the sandfish (Scincus scincus), swims within a granular medium [1]. On the surface, the lizard uses a standard diagonal gait, but once below the surface, the organism no longer uses limbs for propulsion. Instead it propagates a large amplitude single period sinusoidal traveling wave down its body and tail to propel itself at speeds up to ~1.5 body-length/sec. Motivated by these experiments we study a numerical model of the sandfish as it swims within a validated soft sphere Molecular Dynamics granular media simulation. We use this model as a tool to understand dynamics like flow fields and forces generated as the animal swims within the granular media. [1] Maladen, R.D. and Ding, Y. and Li, C. and Goldman, D.I., Undulatory Swimming in Sand: Subsurface Locomotion of the Sandfish Lizard, Science, 325, 314, 2009

  2. Sand, jams and jets

    International Nuclear Information System (INIS)

    Granular media are offering new insights into problems in condensed-matter physics and materials science, as Heinrich Jaeger explains. The remarkable properties of granular materials are so familiar that most of us do not even notice them. It is clear, for example, that we cannot walk on water unless the temperature has dropped below freezing. However, we take it for granted that sand will support our weight as if it were a solid, even though it can also be poured like a liquid under the same ambient conditions. From breakfast cereal, sugar and flour to construction materials, mining products and pharmaceuticals, granular media are present everywhere in our daily lives. (U.K.)

  3. Atlas of Dutch drift sands

    Science.gov (United States)

    Riksen, Michel; Jungerius, Pieter

    2013-04-01

    The Netherlands is well known for its aeolian landscapes. Frequent storms during the High Middle Ages (1000-1300 AD) reactivated Pleistocene coversands and river dunes and are responsible for the formation of the Holocene drift sands at a scale which is unique for Europe. A hypothesized relationship with farmer practices for making plaggensoils has recently been refuted, because drift sand formation began centuries earlier. The coastal dune belt with their parabolic dunes dates from the same period as the drift sand. An estimate of the extent of drift sands can be made from soil maps: drift sands are too young to show much profile development (Regosols). With this method Koster estimated the maximum extent of Holocene drift sands in the Netherlands to be about 800 km2 (Koster 2005). Laser altimetry allows a more precise estimate of the total surface affected by wind from the characteristic relief patterns produced by the Holocene wind, which is different from the smooth surface of cover sand deposits. Laser altimetry has been used before to investigate the mechanism of drift sand formation (Jungerius & Riksen 2010). Most of the surface affected by wind is not active anymore, but the tell-tale rough surface survived ages of different landuse. The total affected surface amounts to 825 km2. It is noteworthy that both methods give comparable results. We recorded a total number of 367 of affected areas of varying shapes, ranging in size from 1.6 ha to a large complex of drif sands of 7,119.5 ha. As is to be expected from their mode of origin, most occurrences are associated with cover sands, and with river dunes along the river Meuse and smaller rivers in other parts of the country. Particularly the final phases of cover sand and river dunes that show more relief as parabolic dunes were affected. There are also small aeolian deposits at the lee side blown from fallow agricultural fields but they are (sub)recent. Most of the relief is irregular, but the larger

  4. 2010 oil sands performance report

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2011-07-01

    With the depletion of traditional energy resources and the rising demand for energy, oil sands have become an important energy resource for meeting energy needs. Oil sands are a mixture of water, sand, clay and bitumen which is recovered either through open pit mining or in situ drilling techniques. The bitumen is then converted into syncrude or sold to refineries for the production of gasoline, diesel or other products. Shell has oil sands operations in Alberta and the aim of this report is to present its 2010 performance in terms of CO2, water, tailings, land, and reclamation and engagement. This document covers several of Shell's operations in the Muskeg River and Jackpine mines, Scotford upgrader, Peace River, Orion, Seal, Cliffdale and Chipmunk. It provides useful information on Shell's oil sands performance to governments, environmental groups, First Nations, local communities and the public.

  5. Simulation of flow over double-element airfoil and wind tunnel test for use in vertical axis wind turbine

    Science.gov (United States)

    Chougule, Prasad; Nielsen, Søren R. K.

    2014-06-01

    Nowadays, small vertical axis wind turbines are receiving more attention due to their suitability in micro-electricity generation. There are few vertical axis wind turbine designs with good power curve. However, the efficiency of power extraction has not been improved. Therefore, an attempt has been made to utilize high lift technology for vertical axis wind turbines in order to improve power efficiency. High lift is obtained by double-element airfoil mainly used in aeroplane wing design. In this current work a low Reynolds number airfoil is selected to design a double-element airfoil blade for use in vertical axis wind turbine to improve the power efficiency. Double-element airfoil blade design consists of a main airfoil and a slat airfoil. Orientation of slat airfoil is a parameter of investigation in this paper and air flow simulation over double-element airfoil. With primary wind tunnel test an orientation parameter for the slat airfoil is initially obtained. Further a computational fluid dynamics (CFD) has been used to obtain the aerodynamic characteristics of double-element airfoil. The CFD simulations were carried out using ANSYS CFX software. It is observed that there is an increase in the lift coefficient by 26% for single-element airfoil at analysed conditions. The CFD simulation results were validated with wind tunnel tests. It is also observe that by selecting proper airfoil configuration and blade sizes an increase in lift coefficient can further be achieved.

  6. Numerical Solution of Compressible Steady Flows around the RAE 2822 Airfoil

    Science.gov (United States)

    Kryštůfek, P.; Kozel, K.

    2014-03-01

    The article presents results of a numerical solution of subsonic, transonic and supersonic flows described by the system of Navier-Stokes equations in 2D laminar compressible flows around the RAE 2822 airfoil. Authors used FVM multistage Runge-Kutta method to numerically solve the flows around the RAE 2822 airfoil.

  7. Research on design methods and aerodynamics performance of CQUDTU-B21 airfoil

    DEFF Research Database (Denmark)

    Chen, Jin; Cheng, Jiangtao; Wen, Zhong Shen

    2012-01-01

    This paper presents the design methods of CQU-DTU-B21 airfoil for wind turbine. Compared with the traditional method of inverse design, the new method is described directly by a compound objective function to balance several conflicting requirements for design wind turbine airfoils, which based o...

  8. Experimental benchmark and code validation for airfoils equipped with passive vortex generators

    DEFF Research Database (Denmark)

    Baldacchino, D.; Manolesos, M.; Ferreira, Célia Maria Dias;

    2016-01-01

    Experimental results and complimentary computations for airfoils with vortex generators are compared in this paper, as part of an effort within the AVATAR project to develop tools for wind turbine blade control devices. Measurements from two airfoils equipped with passive vortex generators, a 30%...

  9. Surface pressure and aerodynamic loads determination of a transonic airfoil based on particle image velocimetry

    NARCIS (Netherlands)

    Ragni, D.; Ashok, A.; van Oudheusden, B.W.; Scarano, F.

    2009-01-01

    The present investigation assesses a procedure to extract the aerodynamic loads and pressure distribution on an airfoil in the transonic flow regime from particle image velocimetry (PIV) measurements. The wind tunnel model is a two-dimensional NACA-0012 airfoil, and the PIV velocity data are used to

  10. Computational Analysis of Propulsion Performance of Modified Pitching Motion Airfoils in Laminar Flow

    Directory of Open Access Journals (Sweden)

    Yonghui Xie

    2014-01-01

    Full Text Available The thrust generation performance of airfoils with modified pitching motion was investigated by computational fluid dynamics (CFD modeling two-dimensional laminar flow at Reynolds number of 104. The effect of shift distance of the pitch axis outside the chord line (R, reduced frequency (k, pitching amplitude (θ, pitching profile, and airfoil shape (airfoil thickness and camber on the thrust generated and efficiency were studied. The results reveal that the increase in R and k leads to an enhancement in thrust generation and a decrease in propulsive efficiency. Besides, there exists an optimal range of θ for the maximum thrust and the increasing θ induces a rapid decrease in propulsive efficiency. Six adjustable parameters (K were employed to realize various nonsinusoidal pitching profiles. An increase in K results in more thrust generated at the cost of decreased propulsive efficiency. The investigation of the airfoil shape effect reveals that there exists an optimal range of airfoil thickness for the best propulsion performance and that the vortex structure is strongly influenced by the airfoil thickness, while varying the camber or camber location of airfoil sections offers no benefit in thrust generation over symmetric airfoil sections.

  11. Flow influence on a mode of flow choking in the airfoil cascade of the thin plates

    Directory of Open Access Journals (Sweden)

    Л.Г. Волянська

    2005-01-01

    Full Text Available  Flow of viscous compressible gas is considered in the airfoil cascade of the thin plates with great negative angle of attack. Influence of wall boundary layer upon a mode of  flow choking in the airfoil cascade is estimated in the article.

  12. Airfoil-shaped micro-mixers for reducing fouling on membrane surfaces

    Science.gov (United States)

    Ho, Clifford K; Altman, Susan J; Clem, Paul G; Hibbs, Michael; Cook, Adam W

    2012-10-23

    An array of airfoil-shaped micro-mixers that enhances fluid mixing within permeable membrane channels, such as used in reverse-osmosis filtration units, while minimizing additional pressure drop. The enhanced mixing reduces fouling of the membrane surfaces. The airfoil-shaped micro-mixer can also be coated with or comprised of biofouling-resistant (biocidal/germicidal) ingredients.

  13. Rime ice accretion and its effect on airfoil performance. Ph.D. Thesis. Final Report

    Science.gov (United States)

    Bragg, M. B.

    1982-01-01

    A methodology was developed to predict the growth of rime ice, and the resulting aerodynamic penalty on unprotected, subcritical, airfoil surfaces. The system of equations governing the trajectory of a water droplet in the airfoil flowfield is developed and a numerical solution is obtained to predict the mass flux of super cooled water droplets freezing on impact. A rime ice shape is predicted. The effect of time on the ice growth is modeled by a time-stepping procedure where the flowfield and droplet mass flux are updated periodically through the ice accretion process. Two similarity parameters, the trajectory similarity parameter and accumulation parameter, are found to govern the accretion of rime ice. In addition, an analytical solution is presented for Langmuir's classical modified inertia parameter. The aerodynamic evaluation of the effect of the ice accretion on airfoil performance is determined using an existing airfoil analysis code with empirical corrections. The change in maximum lift coefficient is found from an analysis of the new iced airfoil shape. The drag correction needed due to the severe surface roughness is formulated from existing iced airfoil and rough airfoil data. A small scale wind tunnel test was conducted to determine the change in airfoil performance due to a simulated rime ice shape.

  14. Modelling of unsteady airfoil aerodynamics for the prediction of blade standstill vibrations

    DEFF Research Database (Denmark)

    Skrzypinski, Witold Robert; Gaunaa, Mac; Sørensen, Niels N.;

    2012-01-01

    In the present work, CFD simulations of the DU96-W-180 airfoil at 26 and 24 deg. angles of attack were performed. 2D RANS and 3D DES computations with non-moving and prescribed motion airfoil suspensions were carried out. The openings of the lift coefficient loops predicted by CFD were different...

  15. Experimental investigation of a transonic potential flow around a symmetric airfoil

    Science.gov (United States)

    Hiller, W. J.; Meier, G. E. A.

    1981-01-01

    Experimental flow investigations on smooth airfoils were done using numerical solutions for transonic airfoil streaming with shockless supersonic range. The experimental flow reproduced essential sections of the theoretically computed frictionless solution. Agreement is better in the expansion part of the of the flow than in the compression part. The flow was nearly stationary in the entire velocity range investigated.

  16. Sand harm in taklimakan Desert highway and sand control

    Institute of Scientific and Technical Information of China (English)

    HANZhiwen; WANGTao; SUNQingwei; DONGZhibao; WANGXunming

    2003-01-01

    Reputed as a wonderful achievement of the world’s highway construction history,the Taklimakan Desert highway is nor facing serious sand drift encroachment problems due to its 447-km-long passage of sand sea consisting of crescent dunes,barchan chains,compound transverse dune ridges and complex megadunes.To solve some technical problems in the protection of the highway from sang drift encroachment,desert experts have been conducting the theoretical and applied studies on sand movement laws;causes,severities and time-space differentiation of sand drift damages;and control ways including mechanical,chemical and biological measures.In this paper the authors give an overall summry on the research contents and recent progress in the control of sand drift damages in China and hold that the theoretical researc results and practices in the prevention of sand drift encroachment on the cross-desert highway represnt a breakthrough and has an cpoch-making significance.Since the construction of protective forest along the cross-desert highway requires large amount of ground water,what will be its environmental consequence and whether it can effectively halt sand drift encroachment on the highway forever are the questions to be studied urgently.

  17. Coastal Erosion Along the West Coast of the Taiwan Strait and It's Influencing Factors

    Institute of Scientific and Technical Information of China (English)

    LIU Jianhui; CAI Feng; QI Hongshuai; LEI Gang; CAO Lihua

    2011-01-01

    Based on the field surveys and repeated cross-profile observations combined with the comparison of many years' topographic maps, this study shows the spatial variability and varying patterns of coastal erosion along the west coast of the Taiwan Strait. Regional differentiation in the Meso-Cenozoic coastal tectonics determined the irregular coastline and geological background for large-scale coastal erosion distribution. The intensity of coastal erosion on the west side of the Taiwan Strait is mild in the northern region, severe in the central region and modest in the southern region. The beaches along the coast are mainly backed by dunes, seawalls or cliffs. The dunes and beaches show periodic erosion and recovery along the coast adjacent to river mouths, while persistent retreat of frontal dunes and beaches tends to occur in other areas. The beach erosion occurs mainly in front of seawalls. Due to the low strength of the unconsolidated sediment the soft cliffs suffer the severest coastline recession. Sea level rise and river sediment discharge reduction are main causes of coastal erosion. Storm surge is common in the studied area and plays an important role in the progress of coastal erosion. Human activities including coastal constructions and sand mining also tend to interfere strongly with the balance of sediment budget in some coastal cells.

  18. Sediment Erosion in Hydro turbines

    OpenAIRE

    Neopane, Hari Prasad

    2010-01-01

    Sediment erosion is caused by the dynamic action of sediment flowing along with water impacting against a solid surface. Hydraulic turbine components operating in sediment-laden water are subject to abrasive and erosive wear. This wear not only reduces the efficiency and the life of the turbine but also causes problems in operation and maintenance, which ultimately leads to economic losses. This is a global operation and maintenance problem of hydropower plants. The high sediment concentratio...

  19. Effects of wheat starch on erosive wear of E-glass fibre reinforced epoxy resin composite materials

    Energy Technology Data Exchange (ETDEWEB)

    Srivastava, V.K. [Department of Mechanical Engineering, Institute of Technology, Banaras Hindu University, Varanasi 221005 (India)]. E-mail: vk_sa@yahoo.co.in

    2006-11-05

    Erosive wear tests were carried out to study the effects of particle, impingement angle and particle velocity on the solid particle erosion behaviour of E-glass fibre reinforced epoxy resin (GFRP) composites. The erosive wear of wheat flour powder filled composites is evaluated at different impingement angles from 30 deg. to 90 deg. and at three different velocities of 24, 35 and 52 m s{sup -1}. The erodent used is silica sand with the size range 150-250 {mu}m of irregular shapes. The result shows erosive wear rates of GFRP composite with 2 g wheat flour, as filler is the lowest. This restricts fiber-matrix debonding. Pure glass epoxy without any filler shows the highest erosion rate due to weak bonding strength. The morphologies of eroded surface were examined by the scanning electron microscope.

  20. The blown sand disaster to the Tarim Desert Highway in Xinjiang, China

    Institute of Scientific and Technical Information of China (English)

    LEI; Jiaqiang(雷加强); WANG; Xueqin(王雪芹); WANG; De(王德); ZHOU; Changhai(周长海); XIA; Xuncheng(夏训诚)

    2002-01-01

    The Tarim Desert Highway in Xinjiang, China, the longest one in the world, has a lengthof 562 km, about 80% of which runs across, from north to south, the Taklimakan Desert. Obviously,the main problem of the road maintenance is the blown sand disaster. The research resultsshowed: (1) the physical environment along thedesert highway is characterized by strong winds,fine and loose ground materials, different dunes and so on, which provides the dynamical conditionand material source for the formation of blown sand disaster to the road and its shelter system.Meanwhile, the trend and cross-section of the road and the structure of the shelter system, asdamage objects, play important roles in the formation process of blown sand disaster; (2) theblown sand disaster to the shelter system is original from the intrusion of the drift sands and mobiledunes outside the shelter system, and the wind erosion and sand deposit caused by the air streamchanges on the ground in the shelter system. The main damage object in the Tarim Desert High-way is the shelter system presently. The damage forms include wind erosion, sand burying anddune covering; and (3) the damaged length of the blocking sand fences is 83.7%, 88.4%, 72.4%,72.8% and 40.3% and the damaged area of the straw checkerboard belts is 73.1%, 58.2%, 44.5%,35.4% and 36.6%, in turn, in 5 different landform units from north to south, and, the disasters tofences and the straw checkerboard belts are 79.5% and 57.6% in the compound dunes while theyare 64.6% and 37.7% in the interdunes respectively.

  1. PIV MEASUREMENTS OF THE NEAR-WAKE FLOW OF AN AIRFOIL ABOVE A FREE SURFACE

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The near-wake flow of a NACA0012 airfoils mounted above a water surface were experimentally studied in a wind/wave tunnel. The main objective of this study is to investigate the influence of the free surface on the structure of the airfoil trailing wake. The flow structure was measured with different ride heights between the airfoil and free surface using a Particle Image Velocimetry (PIV) system. The Reynolds number based on the chord length of the airfoil was about 3.5×103. For each experimental condition, large amount of instantaneous velocity fields were captured and ensemble-averaged to get the spatial distributions of mean velocity and mean vorticity, as well as turbulence statistics. The results show that the flow structures of the airfoil wake varies remarkably with the change in the ride height.

  2. Corrections for attached sidewall boundary-layer effects in 2-dimensional airfoil testing

    Science.gov (United States)

    Murthy, A. V.

    1985-01-01

    The problems of sidewall boundary-layer effects in airfoil testing is treated by considering the changes in the flow area due to boundary-layer thinning under the influence of the airfoil flowfield. Using von Karman's momentum integral equation, it is shown that the sidewall boundary-layer thickness in the region of the airfoil can reduce to about half the undisturbed value under the conditions prevailing in testing of supercritical airfoils. A Mach number correction due to this increased width of the flow passage is proposed. Using the small disturbance approximation, the effect of the sidewall boundary-layers is shown to be equivalent to a change in the test Mach number and also in the airfoil thickness. Comparison of the results of this approach with other similarity rules and correlation of the experimental data demonstrate the applicability of the analysis presented from low speeds to transonic speeds.

  3. Influences of surface temperature on a low camber airfoil aerodynamic performances

    Directory of Open Access Journals (Sweden)

    Valeriu DRAGAN

    2016-03-01

    Full Text Available The current note refers to the comparison between a NACA 2510 airfoil with adiabatic walls and the same airfoil with heated patches. Both suction and pressure sides were divided into two regions covering the leading edge (L.E. and trailing edge (T.E.. A RANS method sensitivity test has been performed in the preliminary stage while for the extended 3D cases a DES-SST approach was used. Results indicate that surface temperature distribution influences the aerodynamics of the airfoil, in particular the viscous drag component but also the lift of the airfoil. Moreover, the influence depends not only on the surface temperature but also on the positioning of the heated surfaces, particularly in the case of pressure lift and drag. Further work will be needed to optimize the temperature distribution for airfoil with higher camber.

  4. Airfoil design: Finding the balance between design lift and structural stiffness

    DEFF Research Database (Denmark)

    Bak, Christian; Gaudern, Nicholas; Zahle, Frederik;

    2014-01-01

    , the design lift coefficient increases if the box length reduces and at the same time the relative thickness increases. Even though the conclusions are specific to the airfoil design approach used, the study indicated that an increased design lift required slightly higher relative thickness compared...... to airfoils with lower design lift to maintain the flapwise stiffness. Also, the study indicated that the lift-drag ratio as a function of flapwise stiffness was relatively independent of the airfoil design with a tendency that the lift-drag ratio decreased for large box lengths. The above conclusions were...... supported by an analysis of the three airfoil families Riso-C2, DU and FFA, where the lift-drag ratio as a function of flapwise stiffness was decreasing, but relatively independent of the airfoil design, and the design lift coefficient was varying depending on the design philosophy. To make the analysis...

  5. On the attenuating effect of permeability on the low frequency sound of an airfoil

    Science.gov (United States)

    Weidenfeld, M.; Manela, A.

    2016-08-01

    The effect of structure permeability on the far-field radiation of a thin airfoil is studied. Assuming low-Mach and high-Reynolds number flow, the near- and far-field descriptions are investigated at flapping-flight and unsteady flow conditions. Analysis is carried out using thin-airfoil theory and compact-body-based calculations for the hydrodynamic and acoustic fields, respectively. Airfoil porosity is modeled via Darcy's law, governed by prescribed distribution of surface intrinsic permeability. Discrete vortex model is applied to describe airfoil wake evolution. To assess the impact of penetrability, results are compared to counterpart predictions for the sound of an impermeable airfoil. Considering the finite-chord airfoil as "acoustically transparent", the leading-order contribution of surface porosity is obtained in terms of an acoustic dipole. It is shown that, at all flow conditions considered, porosity causes attenuation in outcome sound level. This is accompanied by a time-delay in the pressure signal, reflecting the mediating effect of permeability on the interaction of fluid flow with airfoil edge points. To the extent that thin-airfoil theory holds (requiring small normal-to-airfoil flow velocities), the results indicate on a decrease of ~ 10 percent and more in the total energy radiated by a permeable versus an impermeable airfoil. This amounts to a reduction in system sound pressure level of 3 dB and above at pitching flight conditions, where the sound-reducing effect of the seepage dipole pressure becomes dominant. The applicability of Darcy's law to model the effect of material porosity is discussed in light of existing literature.

  6. Preliminary Investigation of Certain Laminar-Flow Airfoils for Application at High Speeds and Reynolds Numbers

    Science.gov (United States)

    Jacobs, E.N.; Abbott, Ira H.; von Doenhoff, A.E.

    1939-01-01

    In order to extend the useful range of Reynolds numbers of airfoils designed to take advantage of the extensive laminar boundary layers possible in an air stream of low turbulence, tests were made of the NACA 2412-34 and 1412-34 sections in the NACA low-turbulence tunnel. Although the possible extent of the laminar boundary layer on these airfoils is not so great as for specially designed laminar-flow airfoils, it is greater than that for conventional airfoils, and is sufficiently extensive so that at Reynolds numbers above 11,000,000 the laminar region is expected to be limited by the permissible 'Reynolds number run' and not by laminar separation as is the case with conventional airfoils. Drag measurements by the wake-survey method and pressure-distribution measurements were made at several lift coefficients through a range of Reynolds numbers up to 11,400,000. The drag scale-effect curve for the NACA 1412-34 is extrapolated to a Reynolds number of 30,000,000 on the basis of theoretical calculations of the skin friction. Comparable skin-friction calculations were made for the NACA 23012. The results indicate that, for certain applications at moderate values of the Reynolds number, the NACA 1412-34 and 2412-34 airfoils offer some advantages over such conventional airfoils as the NACA 23012. The possibility of maintaining a more extensive laminar boundary layer on these airfoils should result in a small drag reduction, and the absence of pressure peaks allows higher speeds to be reached before the compressibility burble is encountered. At lower Reynold numbers, below about 10,000,000, these airfoils have higher drags than airfoils designed to operate with very extensive laminar boundary layers.

  7. Airfoil shape optimization using non-traditional optimization technique and its validation

    Directory of Open Access Journals (Sweden)

    R. Mukesh

    2014-07-01

    Full Text Available Computational fluid dynamics (CFD is one of the computer-based solution methods which is more widely employed in aerospace engineering. The computational power and time required to carry out the analysis increase as the fidelity of the analysis increases. Aerodynamic shape optimization has become a vital part of aircraft design in the recent years. Generally if we want to optimize an airfoil we have to describe the airfoil and for that, we need to have at least hundred points of x and y co-ordinates. It is really difficult to optimize airfoils with this large number of co-ordinates. Nowadays many different schemes of parameter sets are used to describe general airfoil such as B-spline, and PARSEC. The main goal of these parameterization schemes is to reduce the number of needed parameters as few as possible while controlling the important aerodynamic features effectively. Here the work has been done on the PARSEC geometry representation method. The objective of this work is to introduce the knowledge of describing general airfoil using twelve parameters by representing its shape as a polynomial function. And also we have introduced the concept of Genetic Algorithm to optimize the aerodynamic characteristics of a general airfoil for specific conditions. A MATLAB program has been developed to implement PARSEC, Panel Technique, and Genetic Algorithm. This program has been tested for a standard NACA 2411 airfoil and optimized to improve its coefficient of lift. Pressure distribution and co-efficient of lift for airfoil geometries have been calculated using the Panel method. The optimized airfoil has improved co-efficient of lift compared to the original one. The optimized airfoil is validated using wind tunnel data.

  8. Unsteady Thick Airfoil Aerodynamics: Experiments, Computation, and Theory

    Science.gov (United States)

    Strangfeld, C.; Rumsey, C. L.; Mueller-Vahl, H.; Greenblatt, D.; Nayeri, C. N.; Paschereit, C. O.

    2015-01-01

    An experimental, computational and theoretical investigation was carried out to study the aerodynamic loads acting on a relatively thick NACA 0018 airfoil when subjected to pitching and surging, individually and synchronously. Both pre-stall and post-stall angles of attack were considered. Experiments were carried out in a dedicated unsteady wind tunnel, with large surge amplitudes, and airfoil loads were estimated by means of unsteady surface mounted pressure measurements. Theoretical predictions were based on Theodorsen's and Isaacs' results as well as on the relatively recent generalizations of van der Wall. Both two- and three-dimensional computations were performed on structured grids employing unsteady Reynolds-averaged Navier-Stokes (URANS). For pure surging at pre-stall angles of attack, the correspondence between experiments and theory was satisfactory; this served as a validation of Isaacs theory. Discrepancies were traced to dynamic trailing-edge separation, even at low angles of attack. Excellent correspondence was found between experiments and theory for airfoil pitching as well as combined pitching and surging; the latter appears to be the first clear validation of van der Wall's theoretical results. Although qualitatively similar to experiment at low angles of attack, two-dimensional URANS computations yielded notable errors in the unsteady load effects of pitching, surging and their synchronous combination. The main reason is believed to be that the URANS equations do not resolve wake vorticity (explicitly modeled in the theory) or the resulting rolled-up un- steady flow structures because high values of eddy viscosity tend to \\smear" the wake. At post-stall angles, three-dimensional computations illustrated the importance of modeling the tunnel side walls.

  9. Unsteady airfoil flows with application to aeroelastic stability

    Energy Technology Data Exchange (ETDEWEB)

    Johansen, Jeppe

    1999-09-01

    The present report describes numerical investigation of two-dimensional unsteady airfoil flows with application to aeroelastic stability. The report is divided in two parts. Part A describes the purely aerodynamic part, while Part B includes the aeroelastic part. In Part A a transition prediction algorithm based on a simplified version of the e{sup n} method is proposed. Laminar Boundary Layer instability data are stored in a database from which stability characteristics can be extracted by interpolation. Input to the database are laminar integral boundary layer parameters. These are computed from an integral boundary layer formulation coupled to a Navier-Stokes flow solver. Five different airfoils are considered at fixed angle of attack, and the flow is computed assuming both fully turbulent and transitional flow and compared with experimental data. Results indicate that using a transition model the drag prediction is improved considerably. Also the lift is slightly improved. At high angles of attack transition will affect leading edge separation which again will affect the overall vortex shedding. If the transition point is not properly predicted this will affect the whole hysteresis curve. The transition model developed in the present work showed more stable predictions compared to the empirical transition model. In Part B a simple three degrees-of-freedom (DOF) structural dynamics model is developed and coupled to the aerodynamics models from Part A. A 2nd order accurate time integration scheme is used to solve the equations of motion. Two airfoils are investigated. The aeroelastic models predict stable conditions well at low angle of attack. But at high angles of attack, and where unstable behaviour is expected, only the Navier-Stokes solver predict correct aeroelastic response. The semi-empirical dynamic stall model does not predict vortex shedding and moment correctly leading to an erroneous aerodynamic damping. (au) 5 tabs.; 55 ills., 52 refs.

  10. Airfoil longitudinal gust response in separated vs. attached flows

    Science.gov (United States)

    Granlund, K.; Monnier, B.; Ol, M.; Williams, D.

    2014-02-01

    Airfoil aerodynamic loads are expected to have quasi-steady, linear dependence on the history of input disturbances, provided that small-amplitude bounds are observed. We explore this assertion for the problem of periodic sinusoidal streamwise gusts, by comparing experiments on nominally 2D airfoils in temporally sinusoidal modulation of freestream speed in a wind tunnel vs. sinusoidal displacement of the airfoil in constant freestream in a water tunnel. In the wind tunnel, there is a streamwise unsteady pressure gradient causing a buoyancy force, while in the water tunnel one must subtract the inertial load of the test article. Both experiments have an added-mass contribution to aerodynamic force. Within measurement resolution, lift and drag, fluctuating and mean, were in good agreement between the two facilities. For incidence angle below static stall, small-disturbance theory was found to be in good agreement with measured lift history, regardless of oscillation frequency. The circulatory component of fluctuating drag was found to be independent of oscillation frequency. For larger incidence angles, there is marked departure between the measured lift history and that predicted from Greenberg's formula. Flow visualization shows coupling between bluff-body shedding and motion-induced shedding, identifiable with lift cancellation or augmentation, depending on the reduced frequency. Isolating the buoyancy effect in the wind tunnel and dynamic tares in the water tunnel, and theoretical calculation of apparent-mass in both cases, we arrive at good agreement in measured circulatory contribution between the two experiments whether the flow is attached or separated substantiating the linear superposition of the various constituents to total lift and drag, and supporting the idea that aerodynamic gust response can legitimately be studied in a steady freestream by oscillating the test article.

  11. Alberta oil sands royalty regime

    International Nuclear Information System (INIS)

    The long term objective of the Oil Sands Business Unit of Alberta Energy is to pave the way for Alberta's bitumen production to reach 3 million barrels per day by 2020. This presentation described the national government's role in resource development. It was emphasized that since the Crown is the owner of the oil sands resource, it would benefit by providing strategic leadership and by generating a larger royalty base. The oil sands fiscal regime was described with reference to generic royalty, risk sharing, investment, and project economics. Business rule principles were also outlined along with criteria for project expansions. Both upstream and downstream challenges and opportunities were listed. 4 figs

  12. CAPILLARITY OF CONCRETE INCORPORATING FOUNDRY SAND AS REPLACEMENT OF SAND

    OpenAIRE

    Khatib, Jamal M.; HERKI, B A; Fırat, Seyhan; Menadi, B; S. Kenai

    2011-01-01

    The potential uses and the high cost of land-filling of used foundry sands have prompted research into their beneficial reuse. This paper presents the results of experimental research into concrete produced by replacing the natural aggregates with recycled aggregates coming from foundry industries. Little work has been done so far on the effect of used foundry sand on the durability of concrete especially water absorption. The main aim of this work was to determine capillary water absorption ...

  13. A multiphase flow approach to modelling sand production using finite elements

    Energy Technology Data Exchange (ETDEWEB)

    Wan, R.G.; Liu, Y. [Calgary Univ., AB (Canada); Wang, J. [Taurus Reservoir Solutions Ltd., Calgary, AB (Canada)

    2004-07-01

    One of the challenges facing heavy oil recovery operations is the production of sand in unconsolidated oil sands and weak sandstones. This study extends previous work on coupled erosion mechanics and hydrodynamics by considering the presence of a gas phase in a previously developed theoretical and numerical model. The extended model captures the physics associated with gas exsolution. The model is developed within the framework of mixture theory and multiphase flow in a component system which includes solids, fluidized solids, oil and gas. The model was recast into petroleum reservoir engineering, similar to the black oil model but with sand production capabilities. The effects of solution gas drive play an important role in the physics of sand production because gas flow increases the susceptibility of grain particle detachment from the sand matrix and subsequent fluid flow. This paper discussed the finite element method along with algorithmic implementations. It also demonstrated the role of a gas phase in sand production through a one-dimensional numerical example of sand production in an oil reservoir undergoing pressure drawdown. 13 refs., 1 tab., 11 figs.

  14. Tolerable soil erosion in Europe

    Science.gov (United States)

    Verheijen, Frank; Jones, Bob; Rickson, Jane; Smith, Celina

    2010-05-01

    Soil loss by erosion has been identified as an important threat to soils in Europe* and is recognised as a contributing process to soil degradation and associated deterioration, or loss, of soil functioning. From a policy perspective, it is imperative to establish well-defined baseline values to evaluate soil erosion monitoring data against. For this purpose, accurate baseline values - i.e. tolerable soil loss - need to be differentiated at appropriate scales for monitoring and, ideally, should take soil functions and even changing environmental conditions into account. The concept of tolerable soil erosion has been interpreted in the scientific literature in two ways: i) maintaining the dynamic equilibrium of soil quantity, and ii) maintaining biomass production, at a location. The first interpretation ignores soil quality by focusing only on soil quantity. The second approach ignores many soil functions by focusing only on the biomass (particularly crop) production function of soil. Considering recognised soil functions, tolerable soil erosion may be defined as 'any mean annual cumulative (all erosion types combined) soil erosion rate at which a deterioration or loss of one or more soil functions does not occur'. Assumptions and problems of this definition will be discussed. Soil functions can generally be judged not to deteriorate as long as soil erosion does not exceed soil formation. At present, this assumption remains largely untested, but applying the precautionary principle appears to be a reasonable starting point. Considering soil formation rates by both weathering and dust deposition, it is estimated that for the majority of soil forming factors in most European situations, soil formation rates probably range from ca. 0.3 - 1.4 t ha-1 yr-1. Although the current agreement on these values seems relatively strong, how the variation within the range is spatially distributed across Europe and how this may be affected by climate, land use and land management

  15. FORECAST THE SOIL EROSION THROUGH THE CARTOGRAMS

    OpenAIRE

    Mădălina - Cristina Marian

    2014-01-01

    Soil erosion in Arges County affects a high percentage of agricultural land. Most agricultural lands are located on slopes undergoing erosion, excess humidity temporarily or permanently, landslides. The importance lies in the need to know theme addressed erosion, the erosive potential of the land, the causes and factors that led to the onset of erosion and its deployment at a accelerated rate and now, because the based on this knowledge to determine the effective measures to prevent and c...

  16. Erosion of metals by pulsating water jet

    OpenAIRE

    Foldyna, J.; Klich, J. (Jiří); Hlaváček, P.; M. Zeleňák; Ščučka, J. (Jiří)

    2012-01-01

    The aim of the paper was to determine erosion effects of pulsating water jet impinging the surface of metal sample. The influence of repeated impacts of water pulses and impact velocity (operating pressure) on the erosion of metal surface was investigated. The development of erosion pattern with respect to number of impacts was analysed and discussed. It was found that erosion caused by repeated impacts of water pulses occurs in three stages. The stage of erosion of the surface can be determi...

  17. A Scenario of Rainfall Erosivity Index Research

    OpenAIRE

    D .V. Pandit1; R. K. Isaac2

    2015-01-01

    Rainfall erosivity index is an important index to evaluate the soil loss due to rainfall. Rainstorm plays a paramount role in surface sealing, runoff and erosion process. Research on rainfall erosivity index is important in understanding the mechanism of soil erosion processes. This paper gives a scenario on the important research work done by the scientists to evaluate the erosivity index by using various methods and approaches. The aim of this paper was also to highl...

  18. Study of Sand Dunes and Their Effect on Desertification of Cultivated Lands in Shaanxi Province, China Using Remote Sensing Techniques

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    About half of the arid and semi-arid lands in the world are deserts that comprise various types of aeolian sand dunes deposits. In Shaanxi Province, aeolian sand dunes cover considerable areas of the Yulin desert and northern Jinbian. Sand dunes are moving in the main wind direction and converting some agricultural area to wasteland. Remote sensing of sand dunes helps in the understanding of aeolian process and desertification. Remote sensing data combined with field studies are valuable in studying sand dunes, regional aeolian depositional history. In particular, active and inactive sand dunes of the north Shaanxi Province were studied using remote sensing and geographic information system. In this study, we describe the Landsat thematic mapper (TM) images, covering north Shaanxi Province, which were used to study the distribution, shape, size, trends, density and movement of sand dunes and their effect on desertification of cultivated lands. Estimation was made depending on soil erodibility factor (Ⅰ) and local climatic factor (C) during the period (June to September). The result indicates that soil erosion caused sand drift of 8.957 5, 7.03 ton for Yulin and Jinbian, respectively. The mean sand dunes movement rate were 4.37, 3.11 m, whereas, monthly sand dune advance rate were 1.092 5, 0.777 5 m, for the two locations, respectively. The study reveals that cultivated lands extended obliquely to the direction of sand dune movement are extremely affected, while other segments that extend parallel to the direction of the movement are not affected. Accordingly the north Shaanxi Province was divided into areas of different classes of potential risk. Moreover, blown sands and sand movement from neighboring highlands also affect the area of western desert.

  19. Erosion potential from Missoula floods in the Pasco Basin, Washington

    International Nuclear Information System (INIS)

    Localities within the Pasco Basin preserve evidence of Missoula floods. Deposits are 46% sand-sized, 36% gravel-sized, and 18% finer than sand-sized. Mean thickness is 39 meters. High water marks at Wallula Gap require a discharge of approximately 12.5 Mcms. At Sentinel Gap, the slope-area method shows that the high water marks require a discharge of 34.6 Mcms. Since this discharge greatly exceeds any estimated for Missoula floods, there must have been backwater ponding from Wallula Gap. Projecting the slope of the water surface at the upper end of Wallula Gap to the downstream cross section at Gable Mountain leads to a discharge of 9.5 Mcms at Sentinel Gap. The HEC-6 steady state code and four sediment transport equations were applied. Assuming sand-sized particles, DuBoys function estimated 4 to 9 meters of scour. Yang's equation estimated 3 to 4 meters of scour. These are a minimum. A hydrograph synthesized for the boundaries of the Pasco Basin shows the maxima of the flood would occur after 90 h at Sentinel Gap, and at 114 h at Wallula Gap. The 200 areas will remain inundated for four days and six hours. With a quasi-dynamic sediment transport computation, HEC-6 scour estimates range from 0.61 meters to 0.915 meters. This is a minimum amount and erosion is highly variable suggesting reworking of sediment. The Meyer-Peter Meuller equations show less than 1 meter of net scour in the 200 areas. More extensive erosion was achieved during particular time steps of this analysis suggesting that sediment re-working would occur

  20. Reclaimability of the spent sand mixture – sand with bentonite – sand with furfuryl resin

    Directory of Open Access Journals (Sweden)

    J. Dańko

    2011-04-01

    Full Text Available Introduction of new binding materials and new technologies of their hardening in casting moulds and cores production requires theapplication of reclamation methods adequate to their properties as well as special devices realizing tasks. The spent sands circulationsystem containing the same kind of moulding and core sands is optimal from the point of view of the expected reclamation results.However, in the face of a significant variability of applied technologies and related to them various reclamation methods, the need - of theobtained reclamation products assessment on the grounds of systematic criteria and uniform bases – arises, with a tendency of indicatingwhich criteria are the most important for the given sand system. The reclaimability results of the mixture of the spent moulding sand withGeko S bentonite and the spent core sand with the Kaltharz 404U resin hardened by acidic hardener 100 T3, are presented in the paper.Investigations were performed with regard to the estimation of an influence of core sands additions (10 –25% on the reclaimed materialquality. Dusts and clay content in the reclaim, its chemical reaction (pH and ignition loss were estimated. The verification of the reclaiminstrumental assessment was performed on the basis of the technological properties estimation of moulding sand with bentonite, where the reclaimed material was used as a matrix.

  1. Diurnal patterns of blowing sand

    Science.gov (United States)

    The diurnal pattern of blowing sand results from a complex process that involves an interaction between solar heating, thermal instability, atmospheric turbulence, wind strength, and surface threshold conditions. During the day, solar heating produces thermal instability, which enhances the convect...

  2. Management recommendations: Sand Lake Complex

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This document is a review of land management practices at the Sand Lake National Wildlife Refuge, by a land use specialist. Recommendations, time frame and...

  3. STUDY OF CREEP OF SAND

    Directory of Open Access Journals (Sweden)

    K. D. Chyong

    2012-07-01

    Full Text Available Statement of the problem. Subgrade has perceived rheological properties, most importantly, creep. As a result, the number subbase displacements and their irregularities grow constantly in re-cent years. But this fact is not taken into account in calculations, this is why additional studies of structural strength and creep of sand are essential.Results. Empirical relationships between displacements of models of sand subbase and loading conditions are obtained. It is shown that creep in sand subbase develops within a few months and years even. A degree of an increase in strength of sand with low moisture content with time result-ing from structural strength formation is examined. It is found that a deformation rate depends largely on a loading level.Conclusions. The data obtained allow us to develop more reliable methods to predict a defor-mation change with time.

  4. Non-aeolian sand ripples

    Science.gov (United States)

    Boudet, J. F.; Amarouchene, Y.; Bonnier, B.; Kellay, H.

    2005-02-01

    By examining the initial stages of the impact of a granular jet on a flat horizontal solid surface we evidenced the existence of oscillatory sand fronts. These oscillations give rise to a novel mechanism for the formation of ripples on sand surfaces. We here show that as the front advances, its slope changes periodically in time, leaving behind a succession of surface elevations and depressions. A key feature of these oscillations is the interplay between the deposition of mobile sand and the avalanching of the static parts giving rise to a remarkable self-regulating system. These features come out naturally from a simplified version of recently proposed models for the dynamics of sand piles.

  5. The costs of soil erosion

    Directory of Open Access Journals (Sweden)

    Tiago Santos Telles

    2011-04-01

    Full Text Available The aim of this study was a survey of the estimated costs of soil erosion, an issue of fundamental importance in view of the current worldwide discussions on sustainability. A list was drawn up of research papers on erosion (on-site and off-site effects and their respective costs. The estimates indicate the amount of resources spent in the process of soil degradation, raising a general awareness of the need for soil conservation. On-site costs affect the production units directly, while off-site costs create a burden borne by the environment, economy and society. In addition, estimating the costs of soil erosion should be effective to alert the agricultural producers, society and government for the need for measures that can be implemented to bring erosion under control. Among the various estimates of soil erosion costs between 1933 a 2010, the highest figure was 45.5 billion dollars a year for the European Union. In the United States, the highest figure was 44 billion dollars a year. In Brazil, estimates for the state of Paraná indicate a value of 242 million dollars a year, and for the state of São Paulo, 212 million dollars a year. These figures show, above all, that conservation measures must be implemented if crop and livestock farming production are to be sustainable.

  6. [Tooth erosion - a multidisciplinary approach].

    Science.gov (United States)

    Strużycka, Izabela; Rusyan, Ewa; Bogusławska-Kapała, Agnieszka

    2016-02-01

    During the last decades, an increasingly greater interest in dental erosion has been observed in clinical dental practice, in dental public health and in dental research because prevalence of erosive tooth wear is still increasing especially in young age group of population. Erosive tooth wear is a multifactorial etiology process characterized by progressive loss of hard dental tissue. It is defined as the exogenous and/or endogenous acids dissolution of the dental tissue, without bacterial involvement. In the development of dental erosive wear, interactions are required which include chemical, biological, behavioral, diet, time, socioeconomic, knowledge, education, and general health factors. Examples of risk groups could be patients with eating disorders, like anorexia nervosa or bulimia nervosa, gastroesophageal reflux disease, chronic alcohol abuse or dependence. Special nutrition habits groups with high consumption of soft or sport drinks, special diets like vegetarian, vegan or raw food diet, the regular intake of drugs, medications and food supplements can also increase the risk for dental erosion. Comprehensive knowledge of the different risk and protective factors is a perquisite for initiating adequate preventive measures. PMID:27000809

  7. Bentonite erosion. Laboratory studies

    International Nuclear Information System (INIS)

    This report covers the laboratory studies that have been performed at Nuclear Chemistry, KTH in the project 'Bentonite Erosion'. Many of the experiments in this report were performed to support the work of the modelling group and were often relatively simple. One of the experiment series was performed to see the impact of gravity and concentration of mono- and di-valent cations. A clay suspension was prepared in a test tube. A net was placed in contact with the suspension, the test tube was filled with solutions of different concentrations and the system was left overnight to settle. The tube was then turned upside down and the behaviour was visually observed. Either the clay suspension fell through the net or stayed on top. By using this method surprisingly sharp determinations of the Critical Coagulation (Flocculation) Concentration (CCC/CFC) could be made. The CCC/CFC of Ca2+ was for sodium montmorillonite determined to be between 1 and 2 mM. An artificial fracture was manufactured in order to simulate the real case scenario. The set-up was two Plexiglas slabs separated by 1 mm thick spacers with a bentonite container at one side of the fracture. Water was pumped with a very low flow rate perpendicular to bentonite container and the water exiting the fracture was sampled and analyzed for colloid content. The bentonite used was treated in different ways. In the first experiment a relatively montmorillonite rich clay was used while in the second bentonite where only the readily soluble minerals had been removed was used. Since Plexiglas was used it was possible to visually observe the bentonite dispersing into the fracture. After the compacted bentonite (1,000 kg/m3) had been water saturated the clay had expanded some 12 mm out into the fracture. As the experiment progressed the clay expanded more out into the fracture and seemed to fractionate in two different phases with less material in the outmost phase. A dark rim which was later analyzed to contain mostly

  8. Bentonite erosion. Laboratory studies

    Energy Technology Data Exchange (ETDEWEB)

    Jansson, Mats (Div. of Nuclear Chemistry, Royal Inst. of Technology, Stockholm (Sweden), School of Chemical Science and Engineering)

    2009-11-15

    This report covers the laboratory studies that have been performed at Nuclear Chemistry, KTH in the project 'Bentonite Erosion'. Many of the experiments in this report were performed to support the work of the modelling group and were often relatively simple. One of the experiment series was performed to see the impact of gravity and concentration of mono- and di-valent cations. A clay suspension was prepared in a test tube. A net was placed in contact with the suspension, the test tube was filled with solutions of different concentrations and the system was left overnight to settle. The tube was then turned upside down and the behaviour was visually observed. Either the clay suspension fell through the net or stayed on top. By using this method surprisingly sharp determinations of the Critical Coagulation (Flocculation) Concentration (CCC/CFC) could be made. The CCC/CFC of Ca2+ was for sodium montmorillonite determined to be between 1 and 2 mM. An artificial fracture was manufactured in order to simulate the real case scenario. The set-up was two Plexiglas slabs separated by 1 mm thick spacers with a bentonite container at one side of the fracture. Water was pumped with a very low flow rate perpendicular to bentonite container and the water exiting the fracture was sampled and analyzed for colloid content. The bentonite used was treated in different ways. In the first experiment a relatively montmorillonite rich clay was used while in the second bentonite where only the readily soluble minerals had been removed was used. Since Plexiglas was used it was possible to visually observe the bentonite dispersing into the fracture. After the compacted bentonite (1,000 kg/m3) had been water saturated the clay had expanded some 12 mm out into the fracture. As the experiment progressed the clay expanded more out into the fracture and seemed to fractionate in two different phases with less material in the outmost phase. A dark rim which was later analyzed to contain

  9. Evaluation of Icing Scaling on Swept NACA 0012 Airfoil Models

    Science.gov (United States)

    Tsao, Jen-Ching; Lee, Sam

    2012-01-01

    Icing scaling tests in the NASA Glenn Icing Research Tunnel (IRT) were performed on swept wing models using existing recommended scaling methods that were originally developed for straight wing. Some needed modifications on the stagnation-point local collection efficiency (i.e., beta(sub 0) calculation and the corresponding convective heat transfer coefficient for swept NACA 0012 airfoil models have been studied and reported in 2009, and the correlations will be used in the current study. The reference tests used a 91.4-cm chord, 152.4-cm span, adjustable sweep airfoil model of NACA 0012 profile at velocities of 100 and 150 knot and MVD of 44 and 93 mm. Scale-to-reference model size ratio was 1:2.4. All tests were conducted at 0deg angle of attack (AoA) and 45deg sweep angle. Ice shape comparison results were presented for stagnation-point freezing fractions in the range of 0.4 to 1.0. Preliminary results showed that good scaling was achieved for the conditions test by using the modified scaling methods developed for swept wing icing.

  10. Application of Nontraditional Optimization Techniques for Airfoil Shape Optimization

    Directory of Open Access Journals (Sweden)

    R. Mukesh

    2012-01-01

    Full Text Available The method of optimization algorithms is one of the most important parameters which will strongly influence the fidelity of the solution during an aerodynamic shape optimization problem. Nowadays, various optimization methods, such as genetic algorithm (GA, simulated annealing (SA, and particle swarm optimization (PSO, are more widely employed to solve the aerodynamic shape optimization problems. In addition to the optimization method, the geometry parameterization becomes an important factor to be considered during the aerodynamic shape optimization process. The objective of this work is to introduce the knowledge of describing general airfoil geometry using twelve parameters by representing its shape as a polynomial function and coupling this approach with flow solution and optimization algorithms. An aerodynamic shape optimization problem is formulated for NACA 0012 airfoil and solved using the methods of simulated annealing and genetic algorithm for 5.0 deg angle of attack. The results show that the simulated annealing optimization scheme is more effective in finding the optimum solution among the various possible solutions. It is also found that the SA shows more exploitation characteristics as compared to the GA which is considered to be more effective explorer.

  11. APPROXIMATION OF FREE-FORM CURVE – AIRFOIL SHAPE

    Directory of Open Access Journals (Sweden)

    CHONG PERK LIN

    2013-12-01

    Full Text Available Approximation of free-form shape is essential in numerous engineering applications, particularly in automotive and aircraft industries. Commercial CAD software for the approximation of free-form shape is based almost exclusively on parametric polynomial and rational parametric polynomial. The parametric curve is defined by vector function of one independent variable R(u = (x(u, y(u, z(u, where 0≤u≤1. Bézier representation is one of the parametric functions, which is widely used in the approximating of free-form shape. Given a string of points with the assumption of sufficiently dense to characterise airfoil shape, it is desirable to approximate the shape with Bézier representation. The expectation is that the representation function is close to the shape within an acceptable working tolerance. In this paper, the aim is to explore the use of manual and automated methods for approximating section curve of airfoil with Bézier representation.

  12. Effects of internal Acoustic Excitation on the Improvementof Airfoil Performance

    Directory of Open Access Journals (Sweden)

    Ikhlase M.Fayed

    2007-01-01

    Full Text Available The effect of internal acoustic excitation on the leading-edge, separated boundary layers and the aerodynamic performance of NACA23015 cross section airfoil are examined as a function of excitation location with ranging frequency range (50-400 Hz of the introduced acoustic. Tests are separately conducted in two sections, open type wind tunnels at the Reynolds number of 3.3x105 for measurement at angle of attack (0, 3, 6, 9 &12 deg. and 3x104 for the visualization at angle of attack (12 deg. based on the airfoil chord. Results indicated that the excitation frequency and the excitation location are the key parameters to alter the flow properties and thus to improve the aerodynamic performance. The most effective excitation frequency is found to be equal to the shear layer instability frequency and on excitation location close to the separation point. Moreover, the lift is increased and drag reduced dramatically. The corresponding boundary layers are visualized to be reattached to the surface.

  13. Symbolic regression modeling of noise generation at porous airfoils

    Science.gov (United States)

    Sarradj, Ennes; Geyer, Thomas

    2014-07-01

    Based on data sets from previous experimental studies, the tool of symbolic regression is applied to find empirical models that describe the noise generation at porous airfoils. Both the self noise from the interaction of a turbulent boundary layer with the trailing edge of an porous airfoil and the noise generated at the leading edge due to turbulent inflow are considered. Following a dimensional analysis, models are built for trailing edge noise and leading edge noise in terms of four and six dimensionless quantities, respectively. Models of different accuracy and complexity are proposed and discussed. For the trailing edge noise case, a general dependency of the sound power on the fifth power of the flow velocity was found and the frequency spectrum is controlled by the flow resistivity of the porous material. Leading edge noise power is proportional to the square of the turbulence intensity and shows a dependency on the fifth to sixth power of the flow velocity, while the spectrum is governed by the flow resistivity and the integral length scale of the incoming turbulence.

  14. Flight tests of a supersonic natural laminar flow airfoil

    Science.gov (United States)

    Frederick, M. A.; Banks, D. W.; Garzon, G. A.; Matisheck, J. R.

    2015-06-01

    A flight test campaign of a supersonic natural laminar flow airfoil has been recently completed. The test surface was an 80 inch (203 cm) chord and 40 inch (102 cm) span article mounted on the centerline store location of an F-15B airplane. The test article was designed with a leading edge sweep of effectively 0° to minimize boundary layer crossflow. The test article surface was coated with an insulating material to avoid significant heat transfer to and from the test article structure to maintain a quasi-adiabatic wall. An aircraft-mounted infrared camera system was used to determine boundary layer transition and the extent of laminar flow. The tests were flown up to Mach 2.0 and chord Reynolds numbers in excess of 30 million. The objectives of the tests were to determine the extent of laminar flow at high Reynolds numbers and to determine the sensitivity of the flow to disturbances. Both discrete (trip dots) and 2D disturbances (forward-facing steps) were tested. A series of oblique shocks, of yet unknown origin, appeared on the surface, which generated sufficient crossflow to affect transition. Despite the unwanted crossflow, the airfoil performed well. The results indicate that the sensitivity of the flow to the disturbances, which can translate into manufacturing tolerances, was similar to that of subsonic natural laminar flow wings.

  15. Uncertainty Quantification for Airfoil Icing using Polynomial Chaos Expansions

    CERN Document Server

    DeGennaro, Anthony M; Martinelli, Luigi

    2014-01-01

    The formation and accretion of ice on the leading edge of a wing can be detrimental to airplane performance. Complicating this reality is the fact that even a small amount of uncertainty in the shape of the accreted ice may result in a large amount of uncertainty in aerodynamic performance metrics (e.g., stall angle of attack). The main focus of this work concerns using the techniques of Polynomial Chaos Expansions (PCE) to quantify icing uncertainty much more quickly than traditional methods (e.g., Monte Carlo). First, we present a brief survey of the literature concerning the physics of wing icing, with the intention of giving a certain amount of intuition for the physical process. Next, we give a brief overview of the background theory of PCE. Finally, we compare the results of Monte Carlo simulations to PCE-based uncertainty quantification for several different airfoil icing scenarios. The results are in good agreement and confirm that PCE methods are much more efficient for the canonical airfoil icing un...

  16. Improvement of airfoil trailing edge bluntness noise model

    Directory of Open Access Journals (Sweden)

    Wei Jun Zhu

    2016-02-01

    Full Text Available In this article, airfoil trailing edge bluntness noise is investigated using both computational aero-acoustic and semi-empirical approach. For engineering purposes, one of the most commonly used prediction tools for trailing edge noise are based on semi-empirical approaches, for example, the Brooks, Pope, and Marcolini airfoil noise prediction model developed by Brooks, Pope, and Marcolini (NASA Reference Publication 1218, 1989. It was found in previous study that the Brooks, Pope, and Marcolini model tends to over-predict noise at high frequencies. Furthermore, it was observed that this was caused by a lack in the model to predict accurately noise from blunt trailing edges. For more physical understanding of bluntness noise generation, in this study, we also use an advanced in-house developed high-order computational aero-acoustic technique to investigate the details associated with trailing edge bluntness noise. The results from the numerical model form the basis for an improved Brooks, Pope, and Marcolini trailing edge bluntness noise model.

  17. Flight tests of a supersonic natural laminar flow airfoil

    International Nuclear Information System (INIS)

    A flight test campaign of a supersonic natural laminar flow airfoil has been recently completed. The test surface was an 80 inch (203 cm) chord and 40 inch (102 cm) span article mounted on the centerline store location of an F-15B airplane. The test article was designed with a leading edge sweep of effectively 0° to minimize boundary layer crossflow. The test article surface was coated with an insulating material to avoid significant heat transfer to and from the test article structure to maintain a quasi-adiabatic wall. An aircraft-mounted infrared camera system was used to determine boundary layer transition and the extent of laminar flow. The tests were flown up to Mach 2.0 and chord Reynolds numbers in excess of 30 million. The objectives of the tests were to determine the extent of laminar flow at high Reynolds numbers and to determine the sensitivity of the flow to disturbances. Both discrete (trip dots) and 2D disturbances (forward-facing steps) were tested. A series of oblique shocks, of yet unknown origin, appeared on the surface, which generated sufficient crossflow to affect transition. Despite the unwanted crossflow, the airfoil performed well. The results indicate that the sensitivity of the flow to the disturbances, which can translate into manufacturing tolerances, was similar to that of subsonic natural laminar flow wings. (paper)

  18. Hybrid airfoil design methods for full-scale ice accretion simulation

    Science.gov (United States)

    Saeed, Farooq

    The objective of this thesis is to develop a design method together with a design philosophy that allows the design of "subscale" or "hybrid" airfoils that simulate fullscale ice accretions. These subscale or hybrid airfoils have full-scale leading edges and redesigned aft-sections. A preliminary study to help develop a design philosophy for the design of hybrid airfoils showed that hybrid airfoils could be designed to simulate full-scale airfoil droplet-impingement characteristics and, therefore, ice accretion. The study showed that the primary objective in such a design should be to determine the aft section profile that provides the circulation necessary for simulating full-scale airfoil droplet-impingement characteristics. The outcome of the study, therefore, reveals circulation control as the main design variable. To best utilize this fact, this thesis describes two innovative airfoil design methods for the design of hybrid airfoils. Of the two design methods, one uses a conventional flap system while the other only suggests the use of boundary-layer control through slot-suction on the airfoil upper surface as a possible alternative for circulation control. The formulation of each of the two design methods is described in detail, and the results from each method are validated using wind-tunnel test data. The thesis demonstrates the capabilities of each method with the help of specific design examples highlighting their application potential. In particular, the flap-system based hybrid airfoil design method is used to demonstrate the design of a half-scale hybrid model of a full-scale airfoil that simulates full-scale ice accretion at both the design and off-design conditions. The full-scale airfoil used is representative of a scaled modern business-jet main wing section. The study suggests some useful advantages of using hybrid airfoils as opposed to full-scale airfoils for a better understanding of the ice accretion process and the related issues. Results

  19. Parametric analyses for synthetic jet control on separation and stall over rotor airfoil

    Institute of Scientific and Technical Information of China (English)

    Zhao Guoqing; Zhao Qijun

    2014-01-01

    Numerical simulations are performed to investigate the effects of synthetic jet control on separation and stall over rotor airfoils. The preconditioned and unsteady Reynolds-averaged Navier-Stokes equations coupled with akxshear stream transport turbulence model are employed to accomplish the flowfield simulation of rotor airfoils under jet control. Additionally, a velocity boundary condition modeled by a sinusoidal function is developed to fulfill the perturba-tion effect of periodic jets. The validity of the present CFD procedure is evaluated by the simulated results of an isolated synthetic jet and the jet control case for airfoil NACA0015. Then, parametric analyses are conducted specifically for an OA213 rotor airfoil to investigate the effects of jet param-eters (forcing frequency, jet location and momentum coefficient, jet direction, and distribution of jet arrays) on the control effect of the aerodynamic characteristics of a rotor airfoil. Preliminary results indicate that the efficiency of jet control can be improved with specific frequencies (the best lift-drag ratio at F+=2.0) and jet angles (40? or 75?) when the jets are located near the separation point of the rotor airfoil. Furthermore, as a result of a suitable combination of jet arrays, the lift coefficient of the airfoil can be improved by nearly 100%, and the corresponding drag coefficient decreased by 26.5%in comparison with the single point control case.

  20. Experimental Study of Thin and Thick Airfoils at Low Reynolds Numbers

    Science.gov (United States)

    Durgesh, Vibhav; Garcia, Elifalet; Johari, Hamid

    2015-11-01

    A recent surge in applications of unmanned air vehicles in various fields has led to increased interest in understanding the characteristics of airfoils at Reynolds number regime ~104. At these low Re numbers, aerodynamics of an airfoil is influenced by laminar separation and its possible reattachment, which is in contrast to airfoil behavior at high Re numbers. This study focused on comparing the load characteristics of symmetric, thin (NACA-0009) and thick (NACA-0021) airfoils at low Re numbers ~2 - 4 × 104, and angles of attack between 2° to 12°, along with simultaneous flow visualization. The experiments were performed in a low speed flow visualization water tunnel facility, and two-component Laser Doppler Velocimetry was used to quantify the inflow conditions and turbulence intensity. A high precision force/torque transducer was used for the load measurements, while hydrogen bubble technique was used for flow visualization on the suction side of the airfoils. The presentation will discuss the correlation between observed flow structures and instantaneous load on the airfoils, as well as the aerodynamic load characteristics of thin and thick airfoils at low Re numbers.

  1. The acoustics and unsteady wall pressure of a circulation control airfoil

    Science.gov (United States)

    Silver, Jonathan C.

    A Circulation Control (CC) airfoil uses a wall jet exiting onto a rounded trailing edge to generate lift via the Coanda effect. The aerodynamics of the CC airfoil have been studied extensively. The acoustics of the airfoil are, however, much less understood. The primary goal of the present work was to study the radiated sound and unsteady surface pressures of a CC airfoil. The focus of this work can be divided up into three main categories: characterizing the unsteady surface pressures, characterizing the radiated sound, and understanding the acoustics from surface pressures. The present work is the first to present the unsteady surface pressures from the trailing edge cylinder of a circulation control airfoil. The auto-spectral density of the unsteady surface pressures at various locations around the trailing edge are presented over a wide range of the jets momentum coefficient. Coherence of pressure and length scales were computed and presented. Single microphone measurements were made at a range of angles for a fixed observer distance in the far field. Spectra are presented for select angles to show the directivity of the airfoil's radiated sound. Predictions of the acoustics were made from unsteady surface pressures via Howe's curvature noise model and a modified Curle's analogy. A summary of the current understanding of the acoustics from a CC airfoil is given along with suggestions for future work.

  2. Reynolds Number Effects Investigation of Supercritical Airfoil Based on EFD and CFD

    Directory of Open Access Journals (Sweden)

    Da-Wei Liu

    2013-12-01

    Full Text Available This study aimed to investigate the transonic Reynolds number effects of supercritical airfoil by EFD and CFD method. An experiment was conducted in NF-6 wind tunnel, to obtain the pressure distribution and aerodynamic coefficients of a typical supercritical airfoil through pressure measuring, with Reynolds numbers varied from 3.5×106 to 1.0×107 per airfoil chord, Mach numbers from 0.6 to 0.8, angles of attack from 0° to 8°. Also, flows over the supercritical airfoil were numerically studied; the two-dimensional Navier-Stokes equations were solved with structure grids by utilizing the Spalart-Allmaras (S-A turbulence model, with Reynolds numbers varied from 2.0×106 to 50×10 6 per airfoil chord and Mach numbers from 0.6 to 0.8. Computational results compared well with experimental results. It is shown that the upper surface pressure distribution of supercritical airfoil including the location and intensity of shock wave and trailing-edge pressure coefficient, changed apparently with variable Reynolds numbers, when shock-induced trailing-edge separation existed. It is also noticed that the lift coefficient increased, drag and pitching moment coefficient decreased as Reynolds number increasing. Results implied that Reynolds number effects should be considered during the early designing stage and optimization of large aircrafts applied supercritical airfoil.

  3. Parametric analyses for synthetic jet control on separation and stall over rotor airfoil

    Directory of Open Access Journals (Sweden)

    Zhao Guoqing

    2014-10-01

    Full Text Available Numerical simulations are performed to investigate the effects of synthetic jet control on separation and stall over rotor airfoils. The preconditioned and unsteady Reynolds-averaged Navier–Stokes equations coupled with a k − ω shear stream transport turbulence model are employed to accomplish the flowfield simulation of rotor airfoils under jet control. Additionally, a velocity boundary condition modeled by a sinusoidal function is developed to fulfill the perturbation effect of periodic jets. The validity of the present CFD procedure is evaluated by the simulated results of an isolated synthetic jet and the jet control case for airfoil NACA0015. Then, parametric analyses are conducted specifically for an OA213 rotor airfoil to investigate the effects of jet parameters (forcing frequency, jet location and momentum coefficient, jet direction, and distribution of jet arrays on the control effect of the aerodynamic characteristics of a rotor airfoil. Preliminary results indicate that the efficiency of jet control can be improved with specific frequencies (the best lift-drag ratio at F+ = 2.0 and jet angles (40° or 75° when the jets are located near the separation point of the rotor airfoil. Furthermore, as a result of a suitable combination of jet arrays, the lift coefficient of the airfoil can be improved by nearly 100%, and the corresponding drag coefficient decreased by 26.5% in comparison with the single point control case.

  4. Airfoil-Shaped Fluid Flow Tool for Use in Making Differential Measurements

    Science.gov (United States)

    England, John Dwight (Inventor); Kelley, Anthony R. (Inventor); Cronise, Raymond J. (Inventor)

    2014-01-01

    A fluid flow tool includes an airfoil structure and a support arm. The airfoil structure's high-pressure side and low-pressure side are positioned in a conduit by the support arm coupled to the conduit. The high-pressure and low-pressure sides substantially face opposing walls of the conduit. At least one measurement port is formed in the airfoil structure at each of its high-pressure side and low-pressure side. A first manifold, formed in the airfoil structure and in fluid communication with each measurement port so-formed at the high-pressure side, extends through the airfoil structure and support arm to terminate and be accessible at the exterior wall of the conduit. A second manifold, formed in the airfoil structure and in fluid communication with each measurement port so-formed at the low-pressure side, extends through the airfoil structure and support arm to terminate and be accessible at the exterior wall of the conduit.

  5. Unsteady 2D potential-flow forces and a thin variable geometry airfoil undergoing arbitrary motion

    Energy Technology Data Exchange (ETDEWEB)

    Gaunaa, M.

    2006-07-15

    In this report analytical expressions for the unsteady 2D force distribution on a variable geometry airfoil undergoing arbitrary motion are derived under the assumption of incompressible, irrotational, inviscid flow. The airfoil is represented by its camberline as in classic thin-airfoil theory, and the deflection of the airfoil is given by superposition of chordwise deflection mode shapes. It is shown from the expressions for the forces, that the influence from the shed vorticity in the wake is described by the same time-lag for all chordwise positions on the airfoil. This time-lag term can be approximated using an indicial function approach, making the practical calculation of the aerodynamic response numerically very efficient by use of Duhamel superposition. Furthermore, the indicial function expressions for the time-lag terms are formulated in their equivalent state-space form, allowing for use of the present theory in problems employing the eigenvalue approach, such as stability analysis. The analytical expressions for the forces simplify to all previously known steady and unsteady thin-airfoil solutions. Apart from the obvious applications within active load control/reduction, the current theory can be used for various applications which up to now have been possible only using much more computational costly methods. The propulsive performance of a soft heaving propulsor, and the influence of airfoil camberline elasticity on the flutter limit are two computational examples given in the report that highlight this feature. (au)

  6. SiC/SiC Leading Edge Turbine Airfoil Tested Under Simulated Gas Turbine Conditions

    Science.gov (United States)

    Robinson, R. Craig; Hatton, Kenneth S.

    1999-01-01

    Silicon-based ceramics have been proposed as component materials for use in gas turbine engine hot-sections. A high pressure burner rig was used to expose both a baseline metal airfoil and ceramic matrix composite leading edge airfoil to typical gas turbine conditions to comparatively evaluate the material response at high temperatures. To eliminate many of the concerns related to an entirely ceramic, rotating airfoil, this study has focused on equipping a stationary metal airfoil with a ceramic leading edge insert to demonstrate the feasibility and benefits of such a configuration. Here, the idea was to allow the SiC/SiC composite to be integrated as the airfoil's leading edge, operating in a "free-floating" or unrestrained manner. and provide temperature relief to the metal blade underneath. The test included cycling the airfoils between simulated idle, lift, and cruise flight conditions. In addition, the airfoils were air-cooled, uniquely instrumented, and exposed to the same internal and external conditions, which included gas temperatures in excess of 1370 C (2500 F). Results show the leading edge insert remained structurally intact after 200 simulated flight cycles with only a slightly oxidized surface. The instrumentation clearly suggested a significant reduction (approximately 600 F) in internal metal temperatures as a result of the ceramic leading edge. The object of this testing was to validate the design and analysis done by Materials Research and Design of Rosemont, PA and to determine the feasibility of this design for the intended application.

  7. A two element laminar flow airfoil optimized for cruise. M.S. Thesis

    Science.gov (United States)

    Steen, Gregory Glen

    1994-01-01

    Numerical and experimental results are presented for a new two-element, fixed-geometry natural laminar flow airfoil optimized for cruise Reynolds numbers on the order of three million. The airfoil design consists of a primary element and an independent secondary element with a primary to secondary chord ratio of three to one. The airfoil was designed to improve the cruise lift-to-drag ratio while maintaining an appropriate landing capability when compared to conventional airfoils. The airfoil was numerically developed utilizing the NASA Langley Multi-Component Airfoil Analysis computer code running on a personal computer. Numerical results show a nearly 11.75 percent decrease in overall wing drag with no increase in stall speed at sailplane cruise conditions when compared to a wing based on an efficient single element airfoil. Section surface pressure, wake survey, transition location, and flow visualization results were obtained in the Texas A&M University Low Speed Wind Tunnel. Comparisons between the numerical and experimental data, the effects of the relative position and angle of the two elements, and Reynolds number variations from 8 x 10(exp 5) to 3 x 10(exp 6) for the optimum geometry case are presented.

  8. Exploring the relationship between gully erosion and rainfall erosivity

    Science.gov (United States)

    Campo, Miguel; Casalí, Javier; Giménez, Rafael

    2016-04-01

    Rainfall erosivity plays and important role in gully erosion. However, there are few studies that explore this relationship. The main purpose of this work is to analyse the link between observed gully erosion rates and rainfall erosivity. However, in order to get a suitable and comparable set of daily rainfall erosivity data, we firstly evaluate the performance of several daily rainfall erosivity models to estimate the daily accumulated RUSLE EI30 index. One 300 ha watershed (El Cantalar) located in Navarre (Spain) was selected to carry out field studies. A meteorological station located 10 km appart from the experimental site provided daily precipitation records since 1930 to 2009 and also 10min records since 1991 to 2009. In this watershed a total of 35 gully headcuts developed in cohesive soil were monitored. Aerial photographic stereo-pairs covering the study area were used for the survey. These were taken in five different years and at different spatial scales each time: 1956 (1: 34,000), 1967 (1:17,500), 1982 (1:13,500), 2003 (1:20,000) and 2006 (1:2000). Manual restitution of photographs was carried out. 1m resolution DEMs were obtained by triangular interpolation (Triangular Irregular Network) and then used to characterize gully headcuts. Moreover, from the aerial photos and the DEMs, ortho-photographs with a final resolution of 0.40 m were created. The geocoding of the scenes had a Root Mean Square error of less than 0.5 m both in planimetry and altimetry. Furthermore, using the DEMs and the ortho-photographs, volumetric headcut retreat rates for each period were calculated as the product of the lineal retreat and a representative section of the headcut. Daily accumulated RUSLE EI30 index was calculated in a conventional way from records of precipitation every 10 minutes for the period 1991-2009; these results were used as reference data. In addition, for the same period, this index was estimated with daily precipitation records through several models

  9. Comparative Study on Rain Splash Erosion of Representative Soils in China

    Institute of Scientific and Technical Information of China (English)

    CHENG Qinjuan; CAI Qiangguo; MA Wenjun

    2008-01-01

    As the first event of soil erosion,rain splash erosion supplies materials for subsequent transportation and entrainment.The Loess Plateau,the southern hilly region and the Northeast China are subject to serious soil and water loss;however,the characteristics of rain splash erosion in those regions are still unclear.The objectives of the study are to analyze the characteristics of splash erosion on loess soil,red soil,purple soil and black soil,and to discuss the relationship between splash erosion and soil properties.Soil samples spatially distributed in the abovementioned regions were collected and underwent simulated rainfalls at a high intensity of 1.2mm/min,lasting for 5,10,15,and 20min,respectively.Rain splash and soil crust development were analyzed.It shows that black soil sample from Heilongjiang Province corresponds to the minimum splash erosion amount because it has high aggregate content,aggregate stability and organic matter content.Loess soil sample from Inner Mongolia corresponds to the maximum splash erosion amount because it has high content of sand particles.Loess soil sample from Shanxi Province has relatively lower splash erosion amount because it has high silt particle content and low aggregate stability easily to be disrupted under rainfalls with high intensity.Although aggregate contents of red soil and purple soil samples from Hubei and Guangdong provinces are high,the stability is weak and prone to be disrupted,so the splash erosion amount is medium.Splash rate which fluctuates over time is observed because soil crust development follows a cycling processes of formation and disruption.In addition,there are two locations of soil crust development,one appears at the surface,and the other occurs at the subsurface.

  10. Interfacial Instability during Granular Erosion

    Science.gov (United States)

    Lefebvre, Gautier; Merceron, Aymeric; Jop, Pierre

    2016-02-01

    The complex interplay between the topography and the erosion and deposition phenomena is a key feature to model granular flows such as landslides. Here, we investigated the instability that develops during the erosion of a wet granular pile by a dry dense granular flow. The morphology and the propagation of the generated steps are analyzed in relation to the specific erosion mechanism. The selected flowing angle of the confined flow on a dry heap appears to play an important role both in the final state of the experiment, and for the shape of the structures. We show that the development of the instability is governed by the inertia of the flow through the Froude number. We model this instability and predict growth rates that are in agreement with the experiment results.

  11. Soil erosion in Slovene Istria

    Directory of Open Access Journals (Sweden)

    Matjaž Mikoš

    2009-12-01

    Full Text Available From the end of nineties of the 20th century, intense hydrologic and geomorphologic research is taking place in the Slovene Istria. As a part of this research also studies on soil erosion were undertaken in the period from 2005 to 2008. The field measurements were under taken onclosed 1m2 large erosion plots under three different land uses (on bare soils in an olive grove, on an overgrown meadow, in a forest, placed south of the Marezige village in the Rokava River basin.We show weekly measurements of surface erosion (interrill erosion for the period of 13 months (the end of March 2005 – the end of April 2006, as well as monthly and seasonal averages together with selected linear statistical correlations between soil erosion and weather parameters.From May 2005 to April 2006 the interrill erosion on bare soils in an olive grove with an inclination of 5.5° amounted to 9013 g/m2 (90 t/ha that corresponds to surface lowering rate of 8.5 mm/yr; on an overgrown meadow with an inclination of 9.4° it amounted to 168 g/m2 (1,68 t/ha that corresponds to surface lowering rate of 0.16 mm//yr; and in a forest with an inclination of 7.8° it amounted to 391 g/m2 (3,91 t/ha and in a forest with an inclination of 21.4° it amounted to 415 g/m2 (4,15 t/ha, respectively, that corresponds to surface lowering rate of 0.4 mm/yr.

  12. Experiments and Numerical Simulations of Dike Erosion due to a Wave Impact

    Directory of Open Access Journals (Sweden)

    Stefania Evangelista

    2015-10-01

    Full Text Available Dike erosion is a crucial issue in coastal and fluvial flood risk management. These defense structures appear vulnerable to extreme hydrological events, whose potential occurrence risk seems to be recently increased due to climate change. Their design and reinforcement is, however, a complex task, and although numerical models are very powerful nowadays, real processes cannot be accurately predicted; therefore, physical models constitute a useful tool to investigate different features under controlled conditions. This paper presents some laboratory experimental results of erosion of a sand dike produced by the impact of a dam break wave. Experiments have been conducted in the Water Engineering Laboratory at the University of Cassino and Southern Lazio, Italy, in a rectangular channel: here, the sudden opening of a gate forming the reservoir generates the wave impacting the dike, made in turn of two different, almost uniform sands. The physical evidence proves that the erosion process is strongly unsteady and significantly different from a gradual overtopping and highlights the importance of apparent cohesion for the fine sand dike. The experimental results have also been compared against the ones obtained through the numerical integration of a two-phase model, which shows the reasonable predictive capability of the temporal free surface and dike profile evolution.

  13. Experimental Investigation on the Aerodynamic Performance of NLF-0414 Iced-Airfoil

    OpenAIRE

    abbas ebrahimi; majid hajipour; Hossein Hasheminasa

    2016-01-01

    Icing phenomenon on a natural laminar flow airfoil (NLF-0414) has been experimentally investigated. Double horn glaze ice geometry which was acquired during a 15 minutes spray time at-2.23℃ with liquid water content and a median volumetric diameter of 1.0 g/m3 and 20 μm, has been extracted from database of NASA Lewis Research Center. Pressure distribution over airfoil surfacewas evaluated at angles of attack between -2 to 6 degrees for both iced and clean airfoils. Aerodynamics performance de...

  14. The effect of acoustic forcing on an airfoil tonal noise mechanism.

    Science.gov (United States)

    Schumacher, Karn L; Doolan, Con J; Kelso, Richard M

    2014-08-01

    The response of the boundary layer over an airfoil with cavity to external acoustic forcing, across a sweep of frequencies, was measured. The boundary layer downstream of the cavity trailing edge was found to respond strongly and selectively at the natural airfoil tonal frequencies. This is considered to be due to enhanced feedback. However, the shear layer upstream of the cavity trailing edge did not respond at these frequencies. These findings confirm that an aeroacoustic feedback loop exists between the airfoil trailing edge and a location near the cavity trailing edge.

  15. Numerical Simulation of Airfoil Aerodynamic Penalties and Mechanisms in Heavy Rain

    OpenAIRE

    Zhenlong Wu; Yihua Cao; Ismail, M.

    2013-01-01

    Numerical simulations that are conducted on a transport-type airfoil, NACA 64-210, at a Reynolds number of 2.6×106 and LWC of 25 g/m3 explore the aerodynamic penalties and mechanisms that affect airfoil performance in heavy rain conditions. Our simulation results agree well with the experimental data and show significant aerodynamic penalties for the airfoil in heavy rain. The maximum percentage decrease in CL is reached by 13.2% and the maximum percentage increase in CD by 47.6%. Performance...

  16. Dynamic stall modeling and correlation with experimental data on airfoils and rotors

    Science.gov (United States)

    Carlson, R. G.; Blackwell, R. H.; Commerford, G. L.; Mirick, P. H.

    1974-01-01

    Two methods for modeling dynamic stall have been developed. The alpha, A, B method generates lift and pitching moments as functions of angle of attack and its first two time derivatives. The coefficients are derived from experimental data for oscillating airfoils. The Time Delay Method generates the coefficients from steady state airfoil characteristics and an associated time delay in stall beyond the steady state stall angle. Correlation with three types of test data shows that the alpha, A, B method is somewhat better for use in predicting helicopter rotor response in forward flight. Correlation with lift and moment hysteresis loops generated for oscillating airfoils was good for both models.

  17. Experimental Study of Tip Vortex Flow from a Periodically Pitched Airfoil Section

    Science.gov (United States)

    Zaman, Khairul; Fagan, Amy; Mankbadi, Mina

    2016-01-01

    An experimental investigation of tip vortex flow from a NACA0012 airfoil, pitched periodically at various frequencies, is conducted in a low-speed wind tunnel. Initially, data for stationary airfoil held fixed at various angles-of-attack are gathered. Flow visualization pictures as well as detailed cross-sectional properties areobtained at various streamwise locations using hot-wire anemometry. Data include mean velocity, streamwise vorticity as well as various turbulent stresses. Preliminary data are also acquired for periodically pitched airfoil. These results are briefly presented in this extended abstract.

  18. Potential flow around two-dimensional airfoils using a singular integral method

    Science.gov (United States)

    Nguyen, Yves; Wilson, Dennis

    1987-01-01

    The problem of potential flow around two-dimensional airfoils is solved by using a new singular integral method. The potential flow equations for incompressible potential flow are written in a singular integral equation. The equation is solved at N collocation points on the airfoil surface. A unique feature of this method is that the airfoil geometry is specified as an independent variable in the exact integral equation. Compared to other numerical methods, the present calculation procedure is much simpler and gives remarkable accuracy for many body shapes. An advantage of the present method is that it allows the inverse design calculation and the results are extremely accurate.

  19. Using the RBFN model and GIS technique to assess wind erosion hazards of Inner Mongolia, China

    Science.gov (United States)

    Shi, Huading; Liu, Jiyuan; Zhuang, Dafang; Hu, Yunfeng

    2006-08-01

    Soil wind erosion is the primary process and the main driving force for land desertification and sand-dust storms in arid and semi-arid areas of Northern China. Many researchers have paid more attention to this issue. This paper select Inner Mongolia autonomous region as the research area, quantify the various indicators affecting the soil wind erosion, using the GIS technology to extract the spatial data, and construct the RBFN (Radial Basis Function Network) model for assessment of wind erosion hazard. After training the sample data of the different levels of wind erosion hazard, we get the parameters of the model, and then assess the wind erosion hazard. The result shows that in the Southern parts of Inner Mongolia wind erosion hazard are very severe, counties in the middle regions of Inner Mongolia vary from moderate to severe, and in eastern are slight. The comparison of the result with other researches shows that the result is in conformity with actual conditions, proving the reasonability and applicability of the RBFN model.

  20. Soil Infiltration, Shear Strength, and Gully Erosion Measured Along the Colorado River- What is Responsible for the Erosion of Cultural Sites?

    Science.gov (United States)

    O'Brien, G. R.; Pederson, J.

    2008-12-01

    Geomorphic parameters were measured at six cultural sites in eastern and western Grand Canyon during 2006 and 2007 to continue building a dataset started in 2001 relating to the processes and causes of gully erosion. Forty-nine repeat total-station and RTK-GPS surveys were conducted of 13 gullies eroding fine sediments flanking the river corridor. Changes in channel geometry were detected along gully bottoms and thalwegs, and net erosion and aggradation of gully thalwegs was quantified. Soil hydraulic conductivity and shear strength were also measured within gully catchments. Finally, local rain gauge data were collected at a study site in eastern Grand Canyon and one in western Grand Canyon. Repeat ground surveys show that gully erosion is concentrated at knickpoints and that new knickpoints tend to form in relatively steep reaches. Despite recent decades of active erosion, results from 2006-2007 indicate that 7 of 13 gullies actually aggraded their channels, 4 of the 13 were unchanged, and only two gullies showed net erosion of their channels. Shear strength of sediments (n = 370) range 0.7-0.8 kg/cm2 for well- developed cryptobiotic crust, and is twice as resistant as simple rainsplash crust. Eighty-seven infiltration- rate measurements documented a range of 0.001-.003 cm/s for finer silt and clay and cryptobiotic soil and is 2-5 times higher for coarser sand and gravel. Values of Ic, which convert to 36-180 mm/hr, suggest only larger summer storm intensities cause Hortonian overland flow and gully erosion, based on the 2006-2007 storm events that ranged from 42-122 mm/hr. The overall rate of erosion for gullies is, strictly speaking, below the detection limit of the repeat surveys, but these sites saw significant erosion in previous study years with more intense rainfall events. In sum, the data indicate that gully erosion is strongly dependent on rainfall intensity and soil infiltration charateristics, and is moderately influenced by local soil strength. Over

  1. FAO's programme on soil erosion

    International Nuclear Information System (INIS)

    The present situation of land degradation in global basis and its negative impacts on soil fertility are presented. The activities undertaken by FAO on erosion control are described. Some recent trends in soil and water conservation are also included. (author). 11 refs, 1 fig., 1 tab

  2. Multi-objective robust airfoil optimization based on non-uniform rational B-spline (NURBS) representation

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    In order to improve airfoil performance under different flight conditions and to make the performance insensitive to off-design condition at the same time,a multi-objective optimization approach considering robust design has been developed and applied to airfoil design. Non-uniform rational B-spline (NURBS) representation is adopted in airfoil design process,control points and related weights around airfoil are used as design variables. Two airfoil representation cases show that the NURBS method can get airfoil geometry with max geometry error less than 0.0019. By using six-sigma robust approach in multi-objective airfoil design,each sub-objective function of the problem has robustness property. By adopting multi-objective genetic algorithm that is based on non-dominated sorting,a set of non-dominated airfoil solutions with robustness can be obtained in the design. The optimum robust airfoil can be traded off and selected in these non-dominated solutions by design tendency. By using the above methods,a multi-objective robust optimization was conducted for NASA SC0712 airfoil. After performing robust airfoil optimization,the mean value of drag coefficient at Ma0.7-0.8 and the mean value of lift coefficient at post stall regime (Ma0.3) have been improved by 12.2% and 25.4%. By comparing the aerodynamic force coefficients of optimization result,it shows that: different from single robust airfoil design which just improves the property of drag divergence at Ma0.7-0.8,multi-objective robust design can improve both the drag divergence property at Ma0.7-0.8 and stall property at low speed. The design cases show that the multi-objective robust design method makes the airfoil performance robust under different off-design conditions.

  3. Oil sands tailings management project

    International Nuclear Information System (INIS)

    The Oil sands leadership initiative (OSLI) works with the Government of Alberta on the development of the oil sands industry, considering environmental, economical and social aspects. Water management was identified as one of most important areas to focus on. Alberta WaterSMART was requested to support the development and the management of projects resulting from the work done or underway in this field. The development of a regional water management solution stood out as the most interesting solution to obtain significant results. In the Athabasca Region, oil sands producers work independently on their water sourcing and disposal with particular attention to fresh water conservation and economics. The Athabasca River represents a source for mines and distant saline aquifers are the target of steam assisted gravity drainage (SAGD) operators. As part of a four-phase project aiming to study the environmental and economic footprint (EEF) benefit of alternatives for Athabasca oil sands production water supply and disposal, the purpose of the tailings water management project was to identify tailings treatment technologies that are ready to be implemented, and to design and evaluate solutions in order to improve regional oil sands production water sourcing and disposal. Alternatives were evaluated based on their total EEF, applying a lifecycle assessment methodology with a particular attention on the quantification of important performance indicators. 25 refs., 8 tabs., 40 figs.

  4. Oil sands tailings management project

    Energy Technology Data Exchange (ETDEWEB)

    Godwalt, C. [Alberta WaterSMART, Calgary, AB (Canada); Kotecha, P. [Suncor Energy Inc, Calgary, AB (Canada); Aumann, C. [Alberta Innovates - Technology Futures, Alberta Governement, AB (Canada)

    2010-11-15

    The Oil sands leadership initiative (OSLI) works with the Government of Alberta on the development of the oil sands industry, considering environmental, economical and social aspects. Water management was identified as one of most important areas to focus on. Alberta WaterSMART was requested to support the development and the management of projects resulting from the work done or underway in this field. The development of a regional water management solution stood out as the most interesting solution to obtain significant results. In the Athabasca Region, oil sands producers work independently on their water sourcing and disposal with particular attention to fresh water conservation and economics. The Athabasca River represents a source for mines and distant saline aquifers are the target of steam assisted gravity drainage (SAGD) operators. As part of a four-phase project aiming to study the environmental and economic footprint (EEF) benefit of alternatives for Athabasca oil sands production water supply and disposal, the purpose of the tailings water management project was to identify tailings treatment technologies that are ready to be implemented, and to design and evaluate solutions in order to improve regional oil sands production water sourcing and disposal. Alternatives were evaluated based on their total EEF, applying a lifecycle assessment methodology with a particular attention on the quantification of important performance indicators. 25 refs., 8 tabs., 40 figs.

  5. The Effect of Air Density on Sand Transport Structures and the Adobe Abrasion Profile: A Field Wind-Tunnel Experiment Over a Wide Range of Altitude

    Science.gov (United States)

    Han, Qingjie; Qu, Jianjun; Dong, Zhibao; Zu, Ruiping; Zhang, Kecun; Wang, Hongtao; Xie, Shengbo

    2013-11-01

    Aeolian sand transport results from interactions between the surface and the airflow above. Air density strongly constrains airflow characteristics and the resulting flow of sand, and therefore should not be neglected in sand transport models. In the present study, we quantify the influence of air density on the sand flow structure, sand transport rate, adobe abrasion profiles, and abrasion rate using a portable wind-tunnel in the field. For a given wind speed, the flow's ability to transport sand decreases at low air density, so total sand transport decreases, but the saltation height increases. Thus, the damage to human structures increases compared with what occurs at lower altitudes. The adobe abrasion rate by the cloud of blowing sand decreases exponentially with increasing height above the surface, while the wind erosion and dust emission intensity both increase with increasing air density. Long-term feedback processes between air density and wind erosion suggest that the development of low-altitude areas due to long-term deflation plays a key role in dust emission, and will have a profound significance for surface Aeolian processes and geomorphology.

  6. Improvement of airfoil trailing edge bluntness noise model

    DEFF Research Database (Denmark)

    Zhu, Wei Jun; Shen, Wen Zhong; Sørensen, Jens Nørkær;

    2016-01-01

    , Pope, and Marcolini airfoil noise prediction model developed by Brooks, Pope, and Marcolini (NASA Reference Publication 1218, 1989). It was found in previous study that the Brooks, Pope, and Marcolini model tends to over-predict noise at high frequencies. Furthermore, it was observed...... that this was caused by a lack in the model to predict accurately noise from blunt trailing edges. For more physical understanding of bluntness noise generation, in this study, we also use an advanced in-house developed high-order computational aero-acoustic technique to investigate the details associated...... with trailing edge bluntness noise. The results from the numerical model form the basis for an improved Brooks, Pope, and Marcolini trailing edge bluntness noise model....

  7. An Improved Parallel Optimization Framework for Transonic Airfoil Design

    Directory of Open Access Journals (Sweden)

    Mohammad Kashif Zahir

    2013-05-01

    Full Text Available Variable Fidelity Optimization (VFO is used to obtain a minimum drag transonic airfoil, at constant lift, subject to thickness and pitching moment constraints using several low fidelity solvers. VFO has emerged as an attractive method of performing, both, high-speed and high-fidelity optimization. VFO uses computationally inexpensive low-fidelity models, complemented by a surrogate to account for the difference between the high- and low-fidelity models, to obtain the optimum of the function efficiently and accurately. The authors’ original Variable Fidelity (VF framework is modified for increased efficiency and accuracy by incorporating parallel evaluation and more constraints to the optimization problem. The method is found to be efficient and capable of finding the optimum that closely agrees with the results of high-fidelity optimization alone.

  8. Dynamic stall on a pitching and surging airfoil

    Science.gov (United States)

    Dunne, Reeve; McKeon, Beverley J.

    2015-08-01

    Vertical axis wind turbine blades undergo dynamic stall due to the large angle of attack variation they experience during a turbine rotation. The flow over a single blade was modeled using a sinusoidally pitching and surging airfoil in a non-rotating frame with a constant freestream flow at a mean chord Reynolds number of . Two-dimensional, time-resolved velocity fields were acquired using particle image velocimetry. Vorticity contours were used to visualize shear layer and vortex activity. A low-order model of dynamic stall was developed using dynamic mode decomposition, from which primary and secondary dynamic separation modes were identified. The interaction between these two modes was able to capture the physics of dynamic stall and as such can be extended to other turbine configurations and problems in unsteady aerodynamics. Results from the linear pitch/surge frame are extrapolated to the rotating VAWT frame to investigate the behavior of identified flow structures.

  9. High frequency microphone measurements for transition detection on airfoils

    DEFF Research Database (Denmark)

    Døssing, Mads

    Time series of pressure fluctuations has been obtained using high frequency microphones distributed over the surface of airfoils undergoing wind tunnel tests in the LM Windtunnel, owned by ’LM Glasfiber’, Denmark. The present report describes the dataanalysis, with special attention given...... to transition detection. It is argued that the transition point can be detected by observing the increase in the mean of the Fourier spectre and that thismethod is very stable froma numerical point of view. Other important issues are also discussed, e.g. the variation of pressure standard deviations (sound...... pressure) and Tollmien-Schlichting frequencies. The tests were made at Reynolds and Mach numbers corresponding to the operating conditions of a typical horizontal axis wind turbine (HAWT). The Risø B1-18, Risø C2-18 and NACA0015 profiles were tested and the measured transition points are reported....

  10. Compliance effects on dynamically pitching wind turbine airfoils

    Science.gov (United States)

    Magstadt, Andrew S.

    The effects of elastic compliance in dynamically pitching wind turbine blades have been investigated. A numerical model guided wind tunnel testing, which used unsteady surface pressure measurements and phase-locked Particle Imaging Velocimetry to gather aerodynamic information. Using a torsionally compliant member, aeroelastic effects on the unsteady aerodynamics were compared against the results from a corresponding rigidly pitching airfoil to isolate the effects of compliance. The novel experimental apparatus and data acquisition techniques developed at the University of Wyoming showed that the presence of compliance can alter flow-field structures and increase dynamic loading. The high sensitivity of this nonlinear system suggests the formation of fluid-structure instabilities in large-scale turbines and demonstrates the potential for aerodynamic control as a means to mitigate adverse loading effects and improve wind turbine efficiency.

  11. SPIV study of passive flow control on a WT airfoil

    DEFF Research Database (Denmark)

    Velte, Clara Marika; Hansen, Martin Otto Laver; Meyer, Knud Erik;

    2010-01-01

    to free stream velocity U=15 m/s. The objective was to investigate the flow structures induced by and separation controlling behavior of vortex generators on the airfoil. The experimental results show strong separation of the uncontrolled flow whereas an intermittent behavior appears for the controlled...... flow, where the appearance of vortex structures alternate with a slightly separated turbulent boundary layer. However, the controlled case is yielding less backflow than the uncontrolled one: On average, the controlled flow leaves a nicely attached flow as opposed to the incident one....... For the controlled flow, the observed vortex structures generated by the devices are similar to those found in studies at lower Reynolds numbers. Further, mixing close to the wall, transferring high momentum fluid into the near wall region, is seen. The hypothesis of intermittent fluctuations in the boundary layer...

  12. Nonlinear power flow feedback control for improved stability and performance of airfoil sections

    Science.gov (United States)

    Wilson, David G.; Robinett, III, Rush D.

    2013-09-03

    A computer-implemented method of determining the pitch stability of an airfoil system, comprising using a computer to numerically integrate a differential equation of motion that includes terms describing PID controller action. In one model, the differential equation characterizes the time-dependent response of the airfoil's pitch angle, .alpha.. The computer model calculates limit-cycles of the model, which represent the stability boundaries of the airfoil system. Once the stability boundary is known, feedback control can be implemented, by using, for example, a PID controller to control a feedback actuator. The method allows the PID controller gain constants, K.sub.I, K.sub.p, and K.sub.d, to be optimized. This permits operation closer to the stability boundaries, while preventing the physical apparatus from unintentionally crossing the stability boundaries. Operating closer to the stability boundaries permits greater power efficiencies to be extracted from the airfoil system.

  13. Effects of a ground vortex on the aerodynamics of an airfoil

    Science.gov (United States)

    Krothapalli, A.; Leopold, D.

    1988-01-01

    An experimental investigation was carried out to study the aerodynamics of an airfoil with a rectangular jet exiting from its lower surface at fifty percent of the chord. The airfoil was tested with and without the influence of a ground plane. Surface static pressures were measured on the airfoil at jet to free stream velocity ratios ranging from 0 to 9. From these pressures, the variation of C sub L with velocity ratio was easily determined. The measurements indicated significant positive and negative pressure regions on the lower surface of the airfoil ahead of and after the nozzle exit respectively. The presence of a ground plane enhanced these pressure regions at low velocity ratios, but at a particular ratio for each plane location, a recirculation zone or vortex formed ahead of the jet resulting in decreased pressures and a drop in C sub L.

  14. Numerical Investigation of Flow Control by Suction and Injection on a Subsonic Airfoil

    Directory of Open Access Journals (Sweden)

    M. H. Shojaefard

    2005-01-01

    Full Text Available This study presents a numerical study concerning flow control by suction and injection. The case studied is the flow field over a subsonic airfoil with four suction and injection slots on the suction side of the airfoil. Five different angles of attack, 0, 5, 10, 13.3 and 20 with the Mach number of 0.15 are studied. Three cases are studied in each angle of attack. The three cases are airfoil with surface suction, surface injection and the base airfoil. A commercial CFD code, the FLUENT, is used in this study. The effect of suction and injection on aerodynamic coefficients is investigated. The results show that the surface suction can significantly increase the lift coefficient. The injection decreases the skin friction.

  15. Impact of uncertainty in airfoil characteristics on wind turbine extreme loads

    DEFF Research Database (Denmark)

    Abdallah, Imad; Natarajan, Anand; Sørensen, John Dalsgaard

    2015-01-01

    Wind tunnel test measurements to characterize the static lift and drag coefficients of airfoils used in wind turbine blades are shown to possess large uncertainties, which leads to uncertainties in the aerodynamic loads on the rotor. In this paper a rational stochastic model is proposed to quantify...... the uncertainty in airfoil static lift and drag coefficients based on field and wind tunnel data, aero-servoelastic calculations and engineering judgment. The stochastic model is subsequently used to assess the effect of the uncertainty in airfoil static lift and drag coefficients on the prediction of extreme...... loads and structural reliability of large wind turbines. It is shown that the uncertainty in the static airfoil data has a significant impact on the prediction of extreme loads effects and structural reliability depending on the component, operating conditions (stand-still versus power production...

  16. Research on Aerodynamic Performance of an Wind Turbine Airfoil With Leading Edge Ice

    Directory of Open Access Journals (Sweden)

    Fu Jie

    2013-12-01

    Full Text Available The performance of wind turbine was influenced by the environment. Among them, airfoil with leading edge ice has a great effect on the changes of aerodynamic performance. This study calculated the performance of an wind tubine airfoil at two iced shape model by CFD simulation using LES. LES in various models has been developed to simulate turbulent flows, especially to separated flows. In this investigation, 2D LES has been used to simulate flow past a wind turbine airfoil with leading edge ice which is a classical separated flow. The results show that flow structure is more complex with abundant whirlpools signifying violent turbulence when airfoil with ice and leads to poorer performance of wind turbine.

  17. Parallel numerical simulation of oscillating airfoil NACA0015 in the channel due to flutter instability

    Directory of Open Access Journals (Sweden)

    Řidký Václav

    2014-03-01

    Full Text Available The work is devoted to 3D and 2D parallel numerical computation of pressure and velocity fields around an elastically supported airfoil self-oscillating due to interaction with the airflow. Numerical solution is computed in the OpenFOAM package, an open-source software package based on finite volume method. Movement of airfoil is described by translation and rotation, identified from experimental data. A new boundary condition for the 2DOF motion of the airfoil was implemented. The results of numerical simulations (velocity are compared with data measured in a wind tunnel, where a physical model of NACA0015 airfoil was mounted and tuned to exhibit the flutter instability. The experimental results were obtained previously in the Institute of Thermomechanics by interferographic measurements in a subsonic wind tunnel in Nový Knín.

  18. Modeling the Aerodynamic Lift Produced by Oscillating Airfoils at Low Reynolds Number

    CERN Document Server

    Khalid, Muhammad Saif Ullah

    2015-01-01

    For present study, setting Strouhal Number (St) as control parameter, numerical simulations for flow past oscillating NACA-0012 airfoil at 1,000 Reynolds Numbers (Re) are performed. Temporal profiles of unsteady forces; lift and thrust, and their spectral analysis clearly indicate the solution to be a period-1 attractor for low Strouhal numbers. This study reveals that aerodynamic forces produced by plunging airfoil are independent of initial kinematic conditions of airfoil that proves the existence of limit cycle. Frequencies present in the oscillating lift force are composed of fundamental (fs), even and odd harmonics (3fs) at higher Strouhal numbers. Using numerical simulations, shedding frequencies (f_s) were observed to be nearly equal to the excitation frequencies in all the cases. Unsteady lift force generated due to the plunging airfoil is modeled by modified van der Pol oscillator. Using method of multiple scales and spectral analysis of steady-state CFD solutions, frequencies and damping terms in th...

  19. Unsteady two-dimensional potential-flow model for thin variable geometry airfoils

    DEFF Research Database (Denmark)

    Gaunaa, Mac

    2010-01-01

    In the present work, analytical expressions for distributed and integral unsteady two-dimensional forces on a variable geometry airfoil undergoing arbitrary motion are derived under the assumption of incompressible, irrotational, inviscid flow. The airfoil is represented by its camber line...... on the airfoil. This time-lag term can be approximated using an indicial function approach, making the practical calculation of the aerodynamic response numerically very efficient by use of Duhamel superposition. Furthermore, the indicial function expressions for the time-lag terms are formulated...... in their equivalent state-space form, allowing for use of the present theory in problems employing the eigenvalue approach, such as stability analysis. The analytical expressions for the integral forces can be reduced to Munk's steady and Theodorsen's unsteady results for thin airfoils, and numerical evaluation shows...

  20. Airfoil Selection of MAV (Miniature Air Vehicle for Low Reynolds Number

    Directory of Open Access Journals (Sweden)

    Mayur S. Marathe

    2013-12-01

    Full Text Available This paper discusses issues and practical requirements of Airfoil for MAV. Here considering the MAV which travel with the speed range between 9-20 m/s. The Airfoil which is been selected on various criteria, i.e. - stable flight, cover maximum distance with minimum force. So here the NACA 2204 is been selected for MAV. The Fluent analysis is done on the airfoil for lift to drag ratio. These MAV are having some purpose i.e.:- they can be use as a spy in enemy area, inspection of hazardous area, where human resource can’t reach. Aerodynamic performance and stability should be considered in the context of the airfoil structural integrity. Particular attention should be paid to the unsteady nature of the flow.

  1. Tube erosion in bubbling fluidized beds

    Energy Technology Data Exchange (ETDEWEB)

    Levy, E.K. [Lehigh Univ., Bethlehem, PA (United States). Energy Research Center; Stallings, J.W. [Electric Power Research Inst., Palo Alto, CA (United States)

    1991-12-31

    This paper reports on experimental and theoretical studies that were preformed of the interaction between bubbles and tubes and tube erosion in fluidized beds. The results are applicable to the erosion of horizontal tubes in the bottom row of a tube bundle in a bubbling bed. Cold model experimental data show that erosion is caused by the impact of bubble wakes on the tubes, with the rate of erosion increasing with the velocity of wake impact with the particle size. Wake impacts resulting from the vertical coalescence of pairs of bubbles directly beneath the tube result in particularly high rates of erosion damage. Theoretical results from a computer simulation of bubbling and erosion show very strong effects of the bed geometry and bubbling conditions on computed rates of erosion. These results show, for example, that the rate of erosion can be very sensitive to the vertical location of the bottom row of tubes with respect to the distributor.

  2. The effect of wind erosion on toxic element content of soils based on wind tunnel trials

    Science.gov (United States)

    Tatárvári, Károly; Négyesi, Gábor

    2016-04-01

    Wind erosion causes enormous problems in many parts of the world. It damages the fertile layer of soils, and eventually wind erosion can transport materials, pathogens and these may cause medical problems in the respiratory system. Numerous international and Hungarian surveys have proved, that wind erosion not only affects loose textured soils. During droughts wind erosion may cause great damage in bound soils of clay in case these are over-cultivated and dusty. As an effect of climate change the duration and frequency of drought periods shall grow. In our investigation samples were taken from the upper 10 cms of soils of 5 various types of mechanical compounds (according to physical characteristics sand, clay, clay loam, loam, sandy loam) in Györ-Moson-Sopron County Hungary. According to the map of Hungary of the areas potentially affected by wind erosion the sand physical soil type is strongly endangered by wind erosion, other areas are moderatly endangered. According to most recent international classification areas belonging to the sand physical soil type are categorized as "endangered by wind erosion", and others belong to the category "not endangered by wind erosion", but these data were not based on local trials. When selecting the sampling areas it was taken to account that opencast sand and gravel mines are in operation in the area. Because of these recently significant wind erosion related phenomena were observed. The area is the most windy in the country. The mechanical composition, CaCO3 content, pH value (H2O,Kcl), humus content of the samples were defined. The wind erosion experiments were conducted in the wind tunnel of the University of Debrecen. The threshold velocities of the soils were measured, and the quantity of the soil transported by the wind was analyzed at four wind velocity value ranges. The transported material intercepted at different wind velocities at the height of 0-10 cm and 10-35 cm. The As, Ba, Cd, Co, Cr, Cu, Ni, Pb, and Zn

  3. FLOWS AROUND TWO AIRFOILS PERFORMING FLING AND SUBSEQUENT TRANSLATION AND TRANSLATION AND SUBSEQUENT CLAP

    Institute of Scientific and Technical Information of China (English)

    孙茂; 于鑫

    2003-01-01

    The aerodynamic forces and flow structures of two airfoils performing "fling and subsequent translation" and "translation and subsequent clap" are studied by numerically solving the Navier-Stokes equations in moving overset grids. These motions are relevant to the flight of very small insects. The Reynolds number, based on the airfoil chord length c and the translation velocity U, is 17. It is shown that: (1) For two airfoils performing fling and subsequent translation, a large lift is generated both in the fling phase and in the early part of the translation phase. During the fling phase,a pair of leading edge vortices of large strength is generated; the generation of the vortex pair in a short period results in a large time rate of change of fluid impulse, which explains the large lift in this period. During the early part of the translation, the two leading edge vortices move with the airfoils;the relative movement of the vortices also results in a large time rate of change of fluid impulse, which explains the large lift in this part of motion. (In the later part of the translation, the vorticity in the vortices is diffused and convected into the wake.) The time averaged lift coeffcient is approximately 2.4 times as large as that of a single airfoil performing a similar motion. (2) For two airfoils performing translation and subsequent clap, a large lift is generated in the clap phase. During the clap, a pair of trailing edge vortices of large strength are generated; again, the generation of the vortex pair in a short period (which results in a large timerate of change of fluid impulse) is responsible for the large lift in this period. The time averaged lift coefficient is approximately 1.6 times as large as that of a single airfoil performing a similar motion. (3) When the initial distance between the airfoils (in the case of clap, the final distance between the airfoils) varies from 0.1 to 0.2c, the lift on an airfoil decreases only slightly but the torque

  4. Latest Pleistocene Deposition and Erosion on the New Jersey Shelf

    Science.gov (United States)

    Christensen, B. A.; Alexander, C.; Stackhouse, S.; Turner, R.; Nordfjord, S.; Austin, J.; Goff, J.; Gulick, S.; Fulthorpe, C.

    2007-12-01

    The New Jersey margin is an ideal location for the study of sedimentary response to glacioeustatic forcing because this passive continental edge is both wide and stable. Although the region has been intensively imaged and mapped geophysically, it is still far from being understood stratigraphically because of a lack of samples to constrain timing and paleo-depositional environment. This study examines the timing and nature of latest Pleistocene erosion and deposition on the shelf, using grab samples and core recovered using the AHC-800 (Active Heave Compensation - 800 m) drilling system. The latest Pleistocene shelf is characterized by (1) downcutting and erosion by rivers associated with subaerial exposure during glacial retreat of sea level; (2) deposition at the shelf edge during sea level fall associated with formation of an outer shelf wedge; and (3) deposition in estuarine environments as sea level rose. Foraminiferal and sediment textural analyses of cores samples ground truth previous seismic reflection-based interpretations of incision and paleochannel formation. Grab samples analyzed for foraminiferal content and grain size identify environment of deposition within three main bathymetric features: sand ridges, sand ribbons, and glacial scours. Radiometric dating (14C) further constrains the timing of intervals of erosion and deposition. We relate our results to other studies and suggest a complex, spatially variable shelf response to glacial advance and retreat. K-Ar analyses of hornblende crystals provide constraints on sediment sources. Two assemblages exist: one consistent with ages of Proterozoic age plutons in the New Jersey area, and another, younger, indicating mixing. K-Ar dates show a clear difference between and Holocene (930- 970 +/- 20 Ma) sedimentary assemblages and sediments older than 30 k.y, (850-880 Ma +/- 20-30 Ma). Holocene hornblend crystal ages are consistent with Grenvillian aged plutons common to the source region (e

  5. Numerical Solution of Inviscid Compressible Steady Flows around the RAE 2822 Airfoil

    Science.gov (United States)

    Kryštůfek, P.; Kozel, K.

    2015-05-01

    The article presents results of a numerical solution of subsonic, transonic and supersonic flows described by the system of Euler equations in 2D compressible flows around the RAE 2822 airfoil. Authors used FVM multistage Runge-Kutta method to numerically solve the flows around the RAE 2822 airfoil. The results are compared with the solution using the software Ansys Fluent 15.0.7.

  6. Airfoil design using a coupled euler and integral boundary layer method with adjoint based sensitivities

    Science.gov (United States)

    Edwards, S.; Reuther, J.; Chattot, J. J.

    The objective of this paper is to present a control theory approach for the design of airfoils in the presence of viscous compressible flows. A coupled system of the integral boundary layer and the Euler equations is solved to provide rapid flow simulations. An adjoint approach consistent with the complete coupled state equations is employed to obtain the sensitivities needed to drive a numerical optimization algorithm. Design to a target pressure distribution is demonstrated on an RAE 2822 airfoil at transonic speeds.

  7. Predicting extreme loads effects on wind turbines considering uncertainty in airfoil data

    OpenAIRE

    Abdallah, Imad; Natarajan, Anand; Sørensen, John Dalsgaard

    2013-01-01

    The sources contributing to uncertainty in a wind turbine blade static airfoil data include wind tunnel testing, CFD calculations, 3D rotational corrections based on CFD or empirical models, surface roughness corrections, Reynolds number corrections, expansion to the full 360-degree angle of attack range, validation by full scale measurements, and geometric distortions of the blade during manufacturing and under loading. In this paper a stochastic model of the static airfoil data is proposed ...

  8. TOPFARM, HawtOpt, AirfoilOpt: Three FUSED-Wind based toolsets

    OpenAIRE

    Pierre-Elouan Réthoré; Frederik Zahle

    2015-01-01

    A presentation about 3 FUSED-Wind based tools developed at DTU Wind Energy. TOPFARM is a tool to optimize wind farm layout from the wind farm owner perspective. HawtOpt is a tool to perform a coupled aero-elastic-structural optimization of wind turbine rotors. AirfoilOpt is a tool to perform coupled aero-structrual optimization of wind turbine blade airfoils.

  9. A study of long separation bubble on thick airfoils and its consequent effects

    International Nuclear Information System (INIS)

    Highlights: • Effects of long separation bubbles on airfoil performance have been discussed. • The bubble is found to induce a camber-effect on the airfoil. • Effects of Re, TI and angle of attack on the bubble have been presented. • Appropriate modelling methodology of the separation-induced transition is presented. • Comparison of γ–Reθ and κ–κL–ω model for separation bubble in 2D is presented. - Abstract: A parametric study has been performed to analyse the flow around the thick-symmetric NACA 0021 airfoil in order to better understand the characteristics and effects of long separation bubbles (LoSBs) that exist on such airfoils at low Reynolds numbers and turbulence intensities. In the article, the prediction capabilities of two recently-developed transition models, the correlation-based γ–Reθ model and the laminar-kinetic-energy-based κ–κL–ω model are assessed. Two-dimensional steady-state simulations indicated that the κ–κL–ω model predicted the separation and reattachment process accurately when compared with published experimental work. The model was then used to study the attributes and the effects of LoSBs as a function of the angle of attack, freestream turbulence intensity and Reynolds number. It was observed that LoSBs considerably degrade the aerodynamic performance of airfoils and lead to abrupt stall behaviour. It is, furthermore, illustrated that the presence of the LoSB leads to an induced camber effect on the airfoil that increases as the airfoil angle of attack increases due to the upstream migration of the bubble. An increase in the Reynolds number or turbulence levels leads to a reduction in the bubble extent, considerably improving the airfoil performance and leading to a progressive trailing-edge stall

  10. "Ladder" structure in tonal noise generated by laminar flow around an airfoil

    OpenAIRE

    Chong, TP; Joseph, PF

    2012-01-01

    The presence of a “ladder” structure in the airfoil tonal noise was discovered in the 1970s, but its mechanism hitherto remains a subject of continual investigation in the research community. Based on the measured noise results and some numerical analysis presented in this letter, the variations of four types of airfoil tonal noise frequencies with the flow velocity were analyzed individually. The ladder structure is proposed to be caused by the acoustic/hydrodynamic frequency lag between the...

  11. Investigation of the Effects of Airfoil-probes on the Aerodynamic Performance of an Axial Compressor

    Institute of Scientific and Technical Information of China (English)

    HE Xiang; MA Hongwei; REN Minglin; XIANG Honghui

    2012-01-01

    In order to investigate the effects of the airfoil-probes on the aerodynamic performance of an axial compressor,a numerical simulation of 3D flow field is performed in a 1.5-stage axial compressor with airfoil-probes installed at the stator leading-edge (LE).The airfoil-probes have a negative influence on the compressor aerodynamic performance at all operating points.A streamwise vortex is induced by the airfoil-probe along both sides of the blade.At the mid-operating point,the vortex is notable along the pressure side and is relatively small along the suction side (SS).At the near-stall point,the vortex is slightly suppressed in the pressure surface (PS),but becomes remarkable in the suction side.A small local-separation is induced by the interactions between the vortex and the end-wall boundary layer in the corner region near the hub.That the positive pitch angle of the airfoil-probe at 6.5% span is about 15° plays an important role in the vortex evolution near the hub,which causes the fact that the airfoil-probe near the hub has the largest effects among the four airfoil-probes.In order to get a further understanding of the vortex evolution in the stator in the numerical simulation,a flow visualization experiment in a water tunnel is performed.The flow visualization results give a deep insight into the evolution of the vortex induced by the airfoil-probe.

  12. Parametric analyses for synthetic jet control on separation and stall over rotor airfoil

    OpenAIRE

    Zhao Guoqing; Zhao Qijun

    2014-01-01

    Numerical simulations are performed to investigate the effects of synthetic jet control on separation and stall over rotor airfoils. The preconditioned and unsteady Reynolds-averaged Navier–Stokes equations coupled with a k − ω shear stream transport turbulence model are employed to accomplish the flowfield simulation of rotor airfoils under jet control. Additionally, a velocity boundary condition modeled by a sinusoidal function is developed to fulfill the perturbation effect of periodic jet...

  13. Flow past a self-oscillating airfoil with two degrees of freedom: measurements and simulations

    OpenAIRE

    Šidlof Petr; Štěpán Martin; Vlček Václav; Řidký Václav; Šimurda David; Horáček Jaromír

    2014-01-01

    The paper focuses on investigation of the unsteady subsonic airflow past an elastically supported airfoil for subcritical flow velocities and during the onset of the flutter instability. A physical model of the NACA0015 airfoil has been designed and manufactured, allowing motion with two degrees of freedom: pitching (rotation about the elastic axis) and plunging (vertical motion). The structural mass and stiffness matrix can be tuned to certain extent, so that the natural frequencies of the t...

  14. The design of post-buckled spinal structures for airfoil shape control using optimization methods

    OpenAIRE

    Ursache, N.M.; Bressloff, N.W.; Keane, A.J.

    2004-01-01

    In this paper we examine the use of optimization methods and a variety of shape definition schemes to design spinal structures for the control of deformable shape airfoils. The aim is to find structures that, when suitably loaded, can be used to alter the aerodynamic performance of a cladding that forms the airfoil. Further, by using structures that are acting in the post buckling regime it is possible to obtain significant changes in shape with only modest changes in applied load.

  15. A Numerical Study of Aerodynamic Performance and Noise of a Bionic Airfoil Based on Owl Wing

    OpenAIRE

    Xiaomin Liu; Xiang Liu

    2014-01-01

    Noise reduction and efficiency enhancement are the two important directions in the development of the multiblade centrifugal fan. In this study, we attempt to develop a bionic airfoil based on the owl wing and investigate its aerodynamic performance and noise-reduction mechanism at the relatively low Reynolds number. Firstly, according to the geometric characteristics of the owl wing, a bionic airfoil is constructed as the object of study at Reynolds number of 12,300. Secondly, the large eddy...

  16. Surface pressure and aerodynamic loads determination of a transonic airfoil based on particle image velocimetry

    OpenAIRE

    Ragni, D.; Ashok, A; van Oudheusden, B.W.; Scarano, F.

    2009-01-01

    The present investigation assesses a procedure to extract the aerodynamic loads and pressure distribution on an airfoil in the transonic flow regime from particle image velocimetry (PIV) measurements. The wind tunnel model is a two-dimensional NACA-0012 airfoil, and the PIV velocity data are used to evaluate pressure fields, whereas lift and drag coefficients are inferred from the evaluation of momentum contour and wake integrals. The PIV-based results are compared to those derived from conve...

  17. Beneficiation of beach magnetite sand

    Directory of Open Access Journals (Sweden)

    Münevver TEL

    2016-06-01

    Full Text Available In this study, beneficiation of beach magnetite sand was investigated by applying high intensity dry magnetic separator. The effect of feed particle size, feed rate, roll rotation speed, induced magnetic field intensity, and separator knife angle on Fe grade and recovery of the magnetite concentrate were investigated. As a result of dry magnetic separation at about 750 Gauss magnetic field conducted with -0.212+0.106 mm size fraction under optimum conditions, a magnetite concentrate assaying 54.41% Fe was obtained with 63.46% recovery where the beach sand sample contained %48.41 Fe.

  18. Soil Erosion. LC Science Tracer Bullet.

    Science.gov (United States)

    Buydos, John F., Comp.

    Soil erosion is the detachment and movement of topsoil or soil material from the upper part of the soil profile. It may occur in the form of rill, gully, sheet, or wind erosion. Agents of erosion may be water, wind, glacial ice, agricultural implements, machinery, and animals. Soil conservation measures require a thorough understanding of the…

  19. Simultaneous Investigation of Flexibility and Plasma Actuation Effects on the Aerodynamic Characteristics of an Oscillating Airfoil

    Directory of Open Access Journals (Sweden)

    Arash Mahboubi Doust

    2016-01-01

    Full Text Available In this work, a numerical study of two dimensional laminar incompressible flow around the flexible oscillating NACA0012 airfoil is performed using the open source code OpenFOAM. Oscillatory motion types including pitching and flapping is considered. Reynolds number for these motions is assumed fixed at 12000. One of the important issues that must be considered in designing air structures, in particular the aircraft wing, is the interaction between the air and the elastic aircraft wings that is known as the Aeroelastic phenomenon. For this purpose, the effect of airfoil flexibility and flow induced vibration in these motion types is investigated and compared with the case of rigid airfoil. It is observed that the flexibility in both types of motions causes improvement of the thrust which is boosted with increasing the frequency. Contrary to thrust, the significant improvement of lift is only achievable in high frequencies. It was also found that the effect of flexibility on the flapping motion is higher than the pitching motion. For flow control on the airfoil, Dielectric Barrier Discharge plasma actuator is used in the trailing edge of a flexible airfoil, and its effect on the flexible airfoil is also investigated.

  20. Numerical Simulations of Subscale Wind Turbine Rotor Inboard Airfoils at Low Reynolds Number

    Energy Technology Data Exchange (ETDEWEB)

    Blaylock, Myra L. [Sandia National Lab. (SNL-CA), Livermore, CA (United States). Thermal/ Fluid Sciences & Engineering Dept.; Maniaci, David Charles [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Wind Energy Technologies Dept.; Resor, Brian R. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Wind Energy Technologies Dept.

    2015-04-01

    New blade designs are planned to support future research campaigns at the SWiFT facility in Lubbock, Texas. The sub-scale blades will reproduce specific aerodynamic characteristics of utility-scale rotors. Reynolds numbers for megawatt-, utility-scale rotors are generally above 2-8 million. The thickness of inboard airfoils for these large rotors are typically as high as 35-40%. The thickness and the proximity to three-dimensional flow of these airfoils present design and analysis challenges, even at the full scale. However, more than a decade of experience with the airfoils in numerical simulation, in the wind tunnel, and in the field has generated confidence in their performance. Reynolds number regimes for the sub-scale rotor are significantly lower for the inboard blade, ranging from 0.7 to 1 million. Performance of the thick airfoils in this regime is uncertain because of the lack of wind tunnel data and the inherent challenge associated with numerical simulations. This report documents efforts to determine the most capable analysis tools to support these simulations in an effort to improve understanding of the aerodynamic properties of thick airfoils in this Reynolds number regime. Numerical results from various codes of four airfoils are verified against previously published wind tunnel results where data at those Reynolds numbers are available. Results are then computed for other Reynolds numbers of interest.

  1. Design of a family of new advanced airfoils for low wind class turbines

    International Nuclear Information System (INIS)

    In order to maximize the ratio of energy capture and reduce the cost of energy, the selection of the airfoils to be used along the blade plays a crucial role. Despite the general usage of existing airfoils, more and more, families of airfoils specially tailored for specific applications are developed. The present research is focused on the design of a new family of airfoils to be used for the blade of one megawatt wind turbine working in low wind conditions. A hybrid optimization scheme has been implemented, combining together genetic and gradient based algorithms. Large part of the work is dedicated to present and discuss the requirements that needed to be satisfied in order to have a consistent family of geometries with high efficiency, high lift and good structural characteristics. For each airfoil, these characteristics are presented and compared to the ones of existing airfoils. Finally, the aerodynamic design of a new blade for low wind class turbine is illustrated and compared to a reference shape developed by using existing geometries. Due to higher lift performance, the results show a sensitive saving in chords, wetted area and so in loads in idling position

  2. Numerical solutions for a two-dimensional airfoil undergoing unsteady motion

    Institute of Scientific and Technical Information of China (English)

    WU Fu-bing; ZENG Nian-dong; ZHANG Liang; WU De-ming

    2004-01-01

    Continuous vorticity panels are used to model general unsteady inviscid, incompressible, and two-dimensional flows. The geometry of the airfoil is approximated by series of short straight segments having endpoints that lie on the actual surface. A piecewise linear, continuous distribution of vorticity over the airfoil surface is used to generate disturbance flow. The no-penetration condition is imposed at the midpoint of each segment and at discrete times. The wake is simulated by a system of point vortices, which move at local fluid velocity. At each time step, a new wake panel with uniform vorticity distribution is attached to the trailing edge, and the condition of eonstant circulation around the airfoil and wake is imposed. A new expression for Kutta condition is developed to study (i) the effect of thickness on the lift build-up of an impulsively started airfoil, (ii) the effects of reduced frequency and heave amplitude on the thrust production of flapping airfoils, and (iii) the vortex-airfoil interaction. This work presents some hydrodynamic results for tidalstreaim turbine.

  3. Numerical Simulation of Airfoil Aerodynamic Penalties and Mechanisms in Heavy Rain

    Directory of Open Access Journals (Sweden)

    Zhenlong Wu

    2013-01-01

    Full Text Available Numerical simulations that are conducted on a transport-type airfoil, NACA 64-210, at a Reynolds number of 2.6×106 and LWC of 25 g/m3 explore the aerodynamic penalties and mechanisms that affect airfoil performance in heavy rain conditions. Our simulation results agree well with the experimental data and show significant aerodynamic penalties for the airfoil in heavy rain. The maximum percentage decrease in CL is reached by 13.2% and the maximum percentage increase in CD by 47.6%. Performance degradation in heavy rain at low angles of attack is emulated by an originally creative boundary-layer-tripped technique near the leading edge. Numerical flow visualization technique is used to show premature boundary-layer separation at high angles of attack and the particulate trajectories at various angles of attack. A mathematic model is established to qualitatively study the water film effect on the airfoil geometric changes. All above efforts indicate that two primary mechanisms are accountable for the airfoil aerodynamic penalties. One is to cause premature boundary-layer transition at low AOA and separation at high AOA. The other occurs at times scales consistent with the water film layer, which is thought to alter the airfoil geometry and increase the mass effectively.

  4. Design of a family of new advanced airfoils for low wind class turbines

    Science.gov (United States)

    Grasso, Francesco

    2014-12-01

    In order to maximize the ratio of energy capture and reduce the cost of energy, the selection of the airfoils to be used along the blade plays a crucial role. Despite the general usage of existing airfoils, more and more, families of airfoils specially tailored for specific applications are developed. The present research is focused on the design of a new family of airfoils to be used for the blade of one megawatt wind turbine working in low wind conditions. A hybrid optimization scheme has been implemented, combining together genetic and gradient based algorithms. Large part of the work is dedicated to present and discuss the requirements that needed to be satisfied in order to have a consistent family of geometries with high efficiency, high lift and good structural characteristics. For each airfoil, these characteristics are presented and compared to the ones of existing airfoils. Finally, the aerodynamic design of a new blade for low wind class turbine is illustrated and compared to a reference shape developed by using existing geometries. Due to higher lift performance, the results show a sensitive saving in chords, wetted area and so in loads in idling position.

  5. Mechanism of Water Droplet Breakup Near the Leading Edge of an Airfoil

    Science.gov (United States)

    Vargas, Mario; Sor, Suthyvann; Magarino, Adelaida, Garcia

    2012-01-01

    This work presents results of an experimental study on droplet deformation and breakup near the leading edge of an airfoil. The experiment was conducted in the rotating rig test cell at the Instituto Nacional de Tecnica Aeroespacial (INTA) in Madrid, Spain. The airfoil model was placed at the end of the rotating arm and a monosize droplet generator produced droplets that fell from above, perpendicular to the path of the airfoil. The interaction between the droplets and the airfoil was captured with high speed imaging and allowed observation of droplet deformation and breakup as the droplet approached the airfoil near the stagnation line. Image processing software was used to measure the position of the droplet centroid, equivalent diameter, perimeter, area, and the major and minor axes of an ellipse superimposed over the deforming droplet. The horizontal and vertical displacement of each droplet against time was also measured, and the velocity, acceleration, Weber number, Bond number, Reynolds number, and the drag coefficients were calculated along the path of the droplet to the beginning of breakup. Droplet deformation is defined and studied against main parameters. The high speed imaging allowed observation of the actual mechanism of breakup and identification of the sequence of configurations from the initiation of the breakup to the disintegration of the droplet. Results and comparisons are presented for droplets of diameters in the range of 500 to 1800 microns, and airfoil velocities of 70 and 90 m/sec.

  6. Drag Coefficient of Water Droplets Approaching the Leading Edge of an Airfoil

    Science.gov (United States)

    Vargas, Mario; Sor, Suthyvann; Magarino, Adelaida Garcia

    2013-01-01

    This work presents results of an experimental study on droplet deformation and breakup near the leading edge of an airfoil. The experiment was conducted in the rotating rig test cell at the Instituto Nacional de Tecnica Aeroespacial (INTA) in Madrid, Spain. An airfoil model was placed at the end of the rotating arm and a monosize droplet generator produced droplets that fell from above, perpendicular to the path of the airfoil. The interaction between the droplets and the airfoil was captured with high speed imaging and allowed observation of droplet deformation and breakup as the droplet approached the airfoil near the stagnation line. Image processing software was used to measure the position of the droplet centroid, equivalent diameter, perimeter, area, and the major and minor axes of an ellipse superimposed over the deforming droplet. The horizontal and vertical displacement of each droplet against time was also measured, and the velocity, acceleration, Weber number, Bond number, Reynolds number, and the drag coefficients were calculated along the path of the droplet to the beginning of breakup. Results are presented and discussed for drag coefficients of droplets with diameters in the range of 300 to 1800 micrometers, and airfoil velocities of 50, 70 and 90 meters/second. The effect of droplet oscillation on the drag coefficient is discussed.

  7. Airfoil Aeroelastic Flutter Analysis Based on Modified Leishman-Beddoes Model at Low Mach Number

    Institute of Scientific and Technical Information of China (English)

    SHAO Song; ZHU Qinghua; ZHANG Chenglin; NI Xianping

    2011-01-01

    Based on modified Leishman-Beddoes(L-B)state space model at low Mach number(lower than 0.3),the airfoil aeroelastic system is presented in this paper.The main modifications for L-B model include a new dynamic stall criterion and revisions of normal force and pitching moment coefficient.The bifurcation diagrams,the limit cycle oscillation (LCO)phase plane plots and the time domain response figures are applied to investigating the stall flutter bifurcation behavior of airfoil aeroelastic systems with symmetry or asymmetry.It is shown that the symmetric periodical oscillation happens after subcritical bifurcation caused by dynamic stall,and the asymmetric periodical oscillation,which is caused by the interaction of dynamic stall and static divergence,only happens in the airfoil aeroelastic system with asymmetry.Validations of the modified L-B model and the airfoil aeroelastic system are presented with the experimental airload data of NACA0012 and OA207 and experimental stall flutter data of NACA0012 respectively.Results demonstrate that the airfoil aeroelastic system presented in this paper is effective and accurate,which can be applied to the investigation of airfoil stall flutter at low Mach number.

  8. Effect of cavity on shock oscillation in transonic flow over RAE2822 supercritical airfoil

    Science.gov (United States)

    Rahman, M. Rizwanur; Labib, Md. Itmam; Hasan, A. B. M. Toufique; Ali, M.; Mitsutake, Y.; Setoguchi, T.

    2016-07-01

    Transonic flow past a supercritical airfoil is strongly influenced by the interaction of shock wave with boundary layer. This interaction induces unsteady self-sustaining shock wave oscillation, flow instability, drag rise and buffet onset which limit the flight envelop. In the present study, a computational analysis has been carried out to investigate the flow past a supercritical RAE2822 airfoil in transonic speeds. To control the shock wave oscillation, a cavity is introduced on the airfoil surface where shock wave oscillates. Different geometric configurations have been investigated for finding optimum cavity geometry and dimension. Unsteady Reynolds averaged Navier-Stokes equations (RANS) are computed at Mach 0.729 with an angle of attack of 5°. Computed results are well validated with the available experimental data in case of baseline airfoil. However, in case of airfoil with control cavity; it has been observed that the introduction of cavity completely suppresses the unsteady shock wave oscillation. Further, significant drag reduction and successive improvement of aerodynamic performance have been observed in airfoil with shock control cavity.

  9. Aerodynamic data banks for Clark-Y, NACA 4-digit and NACA 16-series airfoil families

    Science.gov (United States)

    Korkan, K. D.; Camba, J., III; Morris, P. M.

    1986-01-01

    With the renewed interest in propellers as means of obtaining thrust and fuel efficiency in addition to the increased utilization of the computer, a significant amount of progress was made in the development of theoretical models to predict the performance of propeller systems. Inherent in the majority of the theoretical performance models to date is the need for airfoil data banks which provide lift, drag, and moment coefficient values as a function of Mach number, angle-of-attack, maximum thickness to chord ratio, and Reynolds number. Realizing the need for such data, a study was initiated to provide airfoil data banks for three commonly used airfoil families in propeller design and analysis. The families chosen consisted of the Clark-Y, NACA 16 series, and NACA 4 digit series airfoils. The various component of each computer code, the source of the data used to create the airfoil data bank, the limitations of each data bank, program listing, and a sample case with its associated input-output are described. Each airfoil data bank computer code was written to be used on the Amdahl Computer system, which is IBM compatible and uses Fortran.

  10. [Spatio-temporal change of sand-fixing function and its driving forces in desertification control ecological function area of Hunshandake, China].

    Science.gov (United States)

    Shen, Lu; Tian, Mei-rong; Gao, Ji-xi; Qian, Jin-ping

    2016-01-01

    Soil erosion is an important ecological and environmental problem in Hunshandake Desert, and the sand-fixing function determines the degree of ecological security in the entire region. In order to clarify the situation of windbreak and sand fixation in Hunshandake area, and to guide the prevention and treatment of desertification on regional scale, based on the meteorological and remote sensing data, this paper quantitatively analyzed the temporal and spatial pattern of windbreak and sand fixation ability between 2000-2010 by the revised wind erosion equation (RWEQ) model, meanwhile, the driving forces for each county ( or banner) in the functional zone were analyzed with the method of principal component analysis. The results showed that there was a fluctuation of the sand fixing capacity in Hunshandake over time, generally rendering a decline trend. The coniferous forest and grassland had strong windbreak and sand fixation capacity in unit area among the various land categories. In terms of spatial distribution, the windbreak and sand fixation function in western and southeastern region was weak and needed to be strengthened with ecological restoration efforts. Through the study of the social driving forces of each administrative region in the function zone, there were 3 main social driving forces of soil erosion in the administrative functions: the intensity of input-output, the level of economic development and the level of agriculture-husbandry development.

  11. WIND TUNNEL RESEARCH ON THE INFLUENCE OF ACTIVE AIRFLOW ON THE LIFT FORCE GENERATED BY THE AIRFOIL

    Directory of Open Access Journals (Sweden)

    Paweł Magryta

    2013-09-01

    Full Text Available The paper discusses the results of wind tunnel tests of airfoils with additional active airflow applied to their upper surfaces. These studies were carried out for a range of velocities up to 28 m/s in an open wind tunnel. Several types of airfoils selected for the examination feature different geometries and are widely applied in today’s aviation industry. The changes in the lift and drag force generated by these airfoils were recorded during the study. The test bench for the tests was equipped with a compressor and a vacuum pump to enable airflow through some holes on the airfoil upper surface. A rapid prototyping method and a 3D printer based on a powder printing technique were applied to print the airfoils. All of their surfaces were subject to surface grinding to smooth their external surfaces. The wind tunnel tests with and without active airflow applied to airfoils are summarised in the paper.

  12. Derivation of airfoil characteristics for the LM 19.1 blade based on 3D CFD rotor calculations

    Energy Technology Data Exchange (ETDEWEB)

    Bak, C.; Soerensen, N.N.; Madsen, H.A. [Risoe National Lab., Roskilde (Denmark)

    1999-03-01

    Airfoil characteristics for the LM 19.1 blade are derived from 3D CFD computations on a full-scale 41-m rotor. Based on 3D CFD the force distributions on the blades are determined, from which airfoil characteristics are derived using the momentum theory. The final airfoil characteristics are constructed using both wind tunnel measurements and 3D CFD. Compared to 2D wind tunnel measurements they show a low lift in stall for the airfoil sections at the tip. At the airfoil sections at the inner part of the blade, they show a high lift in stall. At about 60% radius the lift agrees well to 2D wind tunnel measurements. Aero-elastic calculations using the final airfoil characteristics show good agreement to measured power and flap moments. Furthermore, a fatigue load analysis shows a reduction of up to 15% of the load compared to commonly used data. (au)

  13. Modeling the fluid/soil interface erosion in the Hole Erosion Test

    Directory of Open Access Journals (Sweden)

    Kissi B.

    2012-07-01

    Full Text Available Soil erosion is a complex phenomenon which yields at its final stage to insidious fluid leakages under the hydraulic infrastructures known as piping and which are the main cause of their rupture. The Hole Erosion Test is commonly used to quantify the rate of piping erosion. In this work, The Hole Erosion Test is modelled by using Fluent software package. The aim is to predict the erosion rate of soil during the hole erosion test. The renormalization group theory – based k–ε turbulence model equations are used. This modelling makes it possible describing the effect of the clay concentration in flowing water on erosion. Unlike the usual one dimensional models, the proposed modelling shows that erosion is not uniform erosion along the hole length. In particular, the concentration of clay is found to increase noticeably the erosion rate.

  14. Optimization of Wind Turbine Airfoils/Blades and Wind Farm Layouts

    Science.gov (United States)

    Chen, Xiaomin

    Shape optimization is widely used in the design of wind turbine blades. In this dissertation, a numerical optimization method called Genetic Algorithm (GA) is applied to address the shape optimization of wind turbine airfoils and blades. In recent years, the airfoil sections with blunt trailing edge (called flatback airfoils) have been proposed for the inboard regions of large wind-turbine blades because they provide several structural and aerodynamic performance advantages. The FX, DU and NACA 64 series airfoils are thick airfoils widely used for wind turbine blade application. They have several advantages in meeting the intrinsic requirements for wind turbines in terms of design point, off-design capabilities and structural properties. This research employ both single- and multi-objective genetic algorithms (SOGA and MOGA) for shape optimization of Flatback, FX, DU and NACA 64 series airfoils to achieve maximum lift and/or maximum lift to drag ratio. The commercially available software FLUENT is employed for calculation of the flow field using the Reynolds-Averaged Navier-Stokes (RANS) equations in conjunction with a two-equation Shear Stress Transport (SST) turbulence model and a three equation k-kl-o turbulence model. The optimization methodology is validated by an optimization study of subsonic and transonic airfoils (NACA0012 and RAE 2822 airfoils). In this dissertation, we employ DU 91-W2-250, FX 66-S196-V1, NACA 64421, and Flat-back series of airfoils (FB-3500-0050, FB-3500-0875, and FB-3500-1750) and compare their performance with S809 airfoil used in NREL Phase II and III wind turbines; the lift and drag coefficient data for these airfoils sections are available. The output power of the turbine is calculated using these airfoil section blades for a given B and lambda and is compared with the original NREL Phase II and Phase III turbines using S809 airfoil section. It is shown that by a suitable choice of airfoil section of HAWT blade, the power generated

  15. Splash erosion. A bibliometric Review

    Science.gov (United States)

    Fernández Raga, M. B.

    2012-04-01

    Ellison (1944) developed the splash board as a system for measuring splash erosion that was both cheap and reliable. Bollinne (1975), Morgan (1978, 1981). Mutchler (1967) described another different type of splash detectors according to whether they were passive or could register data. In the study mentioned above these authors included bottles, funnels, glasses, photography, markers. After that several devices has been made up like the splash sampler (Leguedois et al., 2005), soil tray (Van Dijk et al., 2002), splash funnel (Terry, 1989) and several rain cups (Fernandez-Raga et al., 2010; Molina and Llinares, 1996; Torri et al., 1987). Splash erosion research has materialized in the form of a number of papers published in international journals. The database of bibliographic references employed has been one of the most prestigious ones: theWeb of Science (ISI). The search was carried out on January 27th 2012. Among the 3x10^8 scholarly documents included in the Science Citation Index Expanded (SCI-EXPANDED) 1899 to present , the searching engine located 439 containing the word "splash erosion*", where the asterisk acts as a wildcard for any letter or group of letters. Of these, 383 were classified as articles, 87 as proceeding papers, 5 as editorial material, 2 as notes and 1 as correction. These documents have been published in 163 different journals, although four are particularly recurrent: Earth surface processes and Landforms, Catena, Soil Science Society of America Journal and Hydrological processes, with 41, 35, 35 and 26 published documents respectively. A geographic analysis of these articles has been carried out in an attempt to determine in what parts of the world research projects were making use of splash erosion. The results are that anglo-saxon countries, as USA, England and Australia dominate, particularly USA, with 130 articles. China and Japan are large communities of researches too, and some Central European countries as Belgium, France Germany

  16. Soil Erosion Threatens Food Production

    Directory of Open Access Journals (Sweden)

    Michael Burgess

    2013-08-01

    Full Text Available Since humans worldwide obtain more than 99.7% of their food (calories from the land and less than 0.3% from the oceans and aquatic ecosystems, preserving cropland and maintaining soil fertility should be of the highest importance to human welfare. Soil erosion is one of the most serious threats facing world food production. Each year about 10 million ha of cropland are lost due to soil erosion, thus reducing the cropland available for world food production. The loss of cropland is a serious problem because the World Health Organization and the Food and Agricultural Organization report that two-thirds of the world population is malnourished. Overall, soil is being lost from agricultural areas 10 to 40 times faster than the rate of soil formation imperiling humanity’s food security.

  17. MHYDAS-Erosion : a distributed single-storm water erosion model for agricultural catchments

    OpenAIRE

    Gumière, S.J.; Raclot, Damien; Cheviron, B.; Davy, G.; Louchart, X.; Fabre, J.C.; Moussa, R.; Le Bissonnais, Y.

    2011-01-01

    In this paper, we present MHYDAS-Erosion, a dynamic and distributed single-storm water erosion model developed as a module of the existing hydrological MHYDAS model. As with many catchment erosion models, MHYDAS-Erosion is able to simulate sediment transport, erosion and deposition by rill and interrill processes. Its originality stems from its capacity to integrate the impact of land management practices (LMP) as key elements controlling the sedimentological connectivity in agricultural catc...

  18. Dry reusing and wet reclaiming of used sodium silicate sand

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Based on the characteristics of used sodium silicate sand and the different use requirements for recycled sand, "dry reusing and wet reclaiming of used sodium silicate sand" is considered as the most suitable technique for the used sand. When the recycled sand is used as support sand, the used sand is only reused by dry process including breaking, screening, dust-removal, etc., and it is not necessary that the used sand is reclaimed with strongly rubbing and scraping method, but when the recycled sand is used as facing sand (or single sand), the used sand must be reclaimed by wet method for higher removal rate of the residual binders. The characteristics and the properties of the dry reused sand are compared with the wet reclaimed sand after combining the different use requirements of support sand and facing sand (or single sand), and above the most adaptive scheme has also been validated.

  19. Erosive burning of solid propellants

    Science.gov (United States)

    King, Merrill K.

    1993-01-01

    Presented here is a review of the experimental and modeling work concerning erosive burning of solid propellants (augmentation of burning rate by flow of product gases across a burning surface). A brief introduction describes the motor design problems caused by this phenomenon, particularly for low port/throat area ratio motors and nozzleless motors. Various experimental techniques for measuring crossflow sensitivity of solid propellant burning rates are described, with the conclusion that accurate simulation of the flow, including upstream flow development, in actual motors is important since the degree of erosive burning depends not only on local mean crossflow velocity and propellant nature, but also upon this upstream development. In the modeling area, a brief review of simplified models and correlating equations is presented, followed by a description of more complex numerical analysis models. Both composite and double-base propellant models are reviewed. A second generation composite model is shown to give good agreement with data obtained in a series of tests in which composite propellant composition and heterogeneity (particle size distribution) were systematically varied. Finally, the use of numerical models for the development of erosive burning correlations is described, and a brief discussion of scaling is presented.

  20. Hydrodynamic Performance Analysis on Different Airfoils of Straight Blade H Type of Vertical Axis Tidal Current Energy Turbine

    Directory of Open Access Journals (Sweden)

    Kan Kan

    2016-01-01

    Full Text Available Airfoil is a key factor that influences the hydrodynamic performance of vertical axis tidal current energy turbine. In order to explore the influences from the runner’s blade airfoil towards its hydrodynamic performance, three-dimensional unsteady flow numerical simulation on four airfoils of straight blade H type of tidal current energy turbines was carried out, under the precondition of same turbine compactness. Through investigating the influences from the four different airfoils of H blade towards the runner in terms of its dynamic torque feature and hydropower utilization coefficient, this research has analyzed the hydrodynamic performance of the tidal current energy turbine. As the research result indicates, the maximum dynamic torque value of the single-blade turbine with NACA0015 airfoil is significantly higher than that of the other three airfoils; while the maximum value of the overall runner torque is determined by the operating conditions such as different stream speed etc. As a whole, hydropower utilization coefficient of the turbine with asymmetric airfoil NACA4415 is better than that of the other three airfoils. This research has provided references for the design and airfoil selection for the new type of tidal current energy turbine.

  1. Wind characteristics and the associated risk of erosion in Seribu Islands patch reef complexes, Java Sea, Indonesia

    Science.gov (United States)

    Poerbandono

    2016-05-01

    This paper explores design event and entrainment of cay beach sands due to wave shear stresses from winds. Univariate frequency analysis is used to predict recurrence intervals of extreme winds from 30-year (1984-2013) global assimilated data set. Two primary clusters of wind directions representing East and West monsoons are examined. This identifies the equivalence of characteristics of regime among the two clusters. Taking into account the threshold of bottom shear stress of cay beach sands, conceptual relationship between height of wind-generated waves (forecasted from predefined fetch length and wind speed) and erosion of cay beach sand is prescribed. The results indicate that East monsoon is the predominant occurrence of wind and facilitates persistent north-westward shift of cay beach sands, while West monsoon provides extreme events in shorter time span. It is suspiciously thought that due to these, net north-westward drift of sand is indicated. These imply that many of cays in the domain being investigated is at risk of erosion due to unequal balance forcing of winds.

  2. UK silica sand resources for fracking

    OpenAIRE

    Mitchell, Clive

    2013-01-01

    UK silica sand resources for fracking Clive Mitchell, Industrial Minerals Specialist, British Geological Survey, Keyworth, Nottingham, NG12 5GG Email: Silica sand is high purity quartz sand that is mainly used for glass production, as foundry sand, in horticulture, leisure and other industrial uses. One specialist use is as a ‘proppant’ to enhance oil and gas recovery. This presentation will focus on this application, particularly for shale gas recovery where it is mo...

  3. Wind tunnel simulation of the effects of freeze-thaw cycles on soil erosion in the Qinghai-Tibet Plateau

    Institute of Scientific and Technical Information of China (English)

    ShengBo Xie; JianJun Qu; Tao Wang

    2016-01-01

    Intense freezing and thawing actions occur in the Qinghai–Tibet Plateau because of its high elevation and cold temperature. The plateau's unique environment makes it easy to generate wind erosion under dry, windy weather conditions, resulting in the emergence of desertification. As a major form of freeze–thaw erosion, freeze–thaw and wind erosion is displayed prominently on the Qinghai–Tibet Plateau. Therefore, in this study, soil samples were collected from the surface of the plateau to undergo freeze–thaw and wind erosion simulation experiments. Results show that wind erosion strength increases with an increasing number of freeze–thaw cycles, water content in the freezing–thawing process, and the difference in freeze–thaw temperatures. Therefore, in the conditions of water participation, the main reason for the freeze–thaw and wind erosion in the Qinghai–Tibet Plateau is the damage to the soil structure by repeated, fierce freeze–thaw actions, and the sand-bearing wind is the main driving force for this process. The research results have theoretical significance for exploring the formation mechanism of freeze–thaw and wind erosion in the Qinghai–Tibet Plateau, and provide a scientific basis for freeze–thaw desertification control in the plateau.

  4. Human impact on erosion patterns and sediment transport in the Yangtze River

    Science.gov (United States)

    Sun, Xilin; Li, Chang'an; Kuiper, K. F.; Zhang, Zengjie; Gao, Jianhua; Wijbrans, J. R.

    2016-08-01

    Sediment load in rivers is an indicator of erosional processes in the upstream river catchments. Understanding the origin and composition of the sediment load can help to assess the influence of natural processes and human activities on erosion. Tectonic uplift, precipitation and run-off, hill slopes and vegetation can influence erosion in natural systems. Agriculture and deforestation are expected to increase the sediment yield, but dams and reservoirs can trap much of this sediment before it reaches the ocean. Here, we use major element composition and 40Ar/39Ar ages of detrital muscovites to constrain the sediment contribution of various tributaries to sedimentation in the Yangtze delta. The sediment contribution calculated from muscovite data was compared with that estimated from current sediment load data from gauging stations. Muscovite data show that the main contributor to the Yangtze delta sands is the Min River, while the current sediment load suggests that the Jinsha and Jialing rivers are the most important current contributors to delta sediments. We suggest that this difference reflects an "old" and "young" erosion pattern, respectively as medium grained muscovite could be transported much slower than suspended sediment load in the complex river-lake systems of the Yangtze River basin. These two different erosion patterns likely reflect enhanced human activity (deforestation, cultivation, and mining) that increasingly overwhelmed long-time natural factors controls on erosion since ~ 1900 cal years B.P.

  5. Particle Erosion Resistance of Bionic Samples Inspired from Skin Structure of Desert Lizard, Laudakin stoliczkana

    Institute of Scientific and Technical Information of China (English)

    He Huang; Yan Zhang; Luquan Ren

    2012-01-01

    In order to improve the particle erosion resistance of engineering surfaces,this paper proposed a bionic sample which is inspired from the skin structure of desert lizard,Laudakin stoliczkana.The bionic sample consists of a hard shell (aluminum) and a soft core (silicone rubber) which form a two-layer composite structure.The sand blast tests indicated that the bionic sample has better particle erosion resistance.In steady erosion period,the weight loss per unit time of the bionic sample is about 10% smaller than the contrast sample.The anti-erosion mechanism of the bionic sample was studied by single particle impact test.The results show that,after the impact,the kinetic energy of the particle is reduced by 56.5% on the bionic sample which is higher than that on the contrast sample (31.2%).That means the bionic sample can partly convert the kinetic energy of the particle into the deformation energy of the silicone rubber layer,thus the erosion is reduced.

  6. Treating tar sands formations with karsted zones

    Energy Technology Data Exchange (ETDEWEB)

    Vinegar, Harold J. (Bellaire, TX); Karanikas, John Michael (Houston, TX)

    2010-03-09

    Methods for treating a tar sands formation are described herein. The tar sands formation may have one or more karsted zones. Methods may include providing heat from one or more heaters to one or more karsted zones of the tar sands formation to mobilize fluids in the formation. At least some of the mobilized fluids may be produced from the formation.

  7. Localisation of flow separation and transition over a pitching NACA0012 airfoil at transitional Reynolds number

    Science.gov (United States)

    Rudmin, Daniel

    Previous research at RMC has cataloged the occurrence of limit cycle oscillations at low-to-moderate Reynolds numbers for an elastically mounted aeroelastic airfoil. These oscillations were attributed to boundary layer separation and the formation of a laminar separation bubble. For this thesis, an instrumented and motor-driven oscillating airfoil rig was designed and fabricated for the purpose of investigating the boundary layer of a NACA-0012 airfoil. The oscillating airfoil was driven by a servo motor to mimic the observed aeroelastic pitching with a sinusoid of matched amplitude and frequency. Hot-wire anemometry was used to investigate the near wake of the new motor-driven airfoil and compare it with the aeroelastic experiment. A chord-wise array of hot-film sensors captured the boundary layer state during the airfoil pitching oscillation. A novel analysis technique is introduced; A sliding window (in time) cross-correlation of adjacent sensors was used to detect dynamic laminar separation. Wind tunnel tests were performed at static angles-of-attack, for quasi-static very low frequency sweeps to verify the technique, and for selected cases of oscillations obtained with the aeroelastic rig. The new detection method was verified against the existing static techniques of phase reversal signature detection and signal cross-correlation by comparing quasi-static and static results. A map of the laminar separation bubble was produced for fixed angles of attack as well as for the pitching airfoil. The presence of a laminar separation was linked to the occurrence and characteristics of the limit cycle oscillations. Keywords: laminar separation, NACA0012, hot-film, hot-wire, anemometry, transitional flow, aeroelasticity.

  8. SOIL EROSION PROCESS RESEARCH AND ITS POTENTIAL IMPACT ON EROSION PREDICTION MODEL DEVELOPMENT

    Institute of Scientific and Technical Information of China (English)

    Chi-hua HUANG; Fenli ZHENG

    2005-01-01

    This paper highlights past efforts in developing erosion process concepts that lead to the development of the current process-based erosion prediction model, i.e., WEPP. Recent progress includes the development of a multiple-box system that can simulate hillslope hydrologic conditions. Laboratory procedures enable the quantification of near-surface hydrologic effects, i.e.,artesian seepage vs. drainage, on the soil erosion process and sediment regime, flow hydraulics, and sediment transport and deposition processes. These recent findings improve soil erosion science and provide new erosion control strategies that may have additional environmental benefits relative to the traditional erosion control practices. The paper also discusses the potential impacts of the erosion process on erosion model development and future research directions of soil erosion process research and model development.

  9. Sediment Analysis Network for Decision Support (SANDS)

    Science.gov (United States)

    Hardin, D. M.; Keiser, K.; Graves, S. J.; Conover, H.; Ebersole, S.

    2009-12-01

    Since the year 2000, Eastern Louisiana, coastal Mississippi, Alabama, and the western Florida panhandle have been affected by 28 tropical storms, seven of which were hurricanes. These tropical cyclones have significantly altered normal coastal processes and characteristics in the Gulf region through sediment disturbance. Although tides, seasonality, and agricultural development influence suspended sediment and sediment deposition over periods of time, tropical storm activity has the capability of moving the largest sediment loads in the shortest periods of time for coastal areas. The importance of sediments upon water quality, coastal erosion, habitats and nutrients has made their study and monitoring vital to decision makers in the region. Currently agencies such as United States Army Corps of Engineers (USACE), NASA, and Geological Survey of Alabama (GSA) are employing a variety of in-situ and airborne based measurements to assess and monitor sediment loading and deposition. These methods provide highly accurate information but are limited in geographic range, are not continuous over a region and, in the case of airborne LIDAR are expensive and do not recur on a regular basis. Multi-temporal and multi-spectral satellite imagery that shows tropical-storm-induced suspended sediment and storm-surge sediment deposits can provide decision makers with immediate and long-term information about the impacts of tropical storms and hurricanes. It can also be valuable for those conducting research and for projects related to coastal issues such as recovery, planning, management, and mitigation. The recently awarded Sediment Analysis Network for Decision Support will generate decision support products using NASA satellite observations from MODIS, Landsat and SeaWiFS instruments to support resource management, planning, and decision making activities in the Gulf of Mexico. Specifically, SANDS will generate decision support products that address the impacts of tropical storms

  10. Decomposition and humification of soil organic carbon after land use change on erosion prone slopes

    Science.gov (United States)

    Häring, Volker; Fischer, Holger; Cadisch, Georg; Stahr, Karl

    2014-05-01

    Soil organic carbon decline after land use change from forest to maize usually lead to soil degradation and elevated CO2 emissions. However, limited knowledge is available on the interactions between rates of SOC change and soil erosion and how SOC dynamics vary with soil depth and clay contents. The 13C isotope based CIDE approach (Carbon Input, Decomposition and Erosion) was developed to determine SOC dynamics on erosion prone slopes. The aims of the present study were: (1) to test the applicability of the CIDE approach to determine rates of decomposition and SOC input under particular considerations of concurrent erosion events on three soil types (Alisol, Luvisol, Vertisol), (2) to adapt the CIDE approach to deeper soil layers (10-20 and 20-30 cm) and (3) to determine the variation of decomposition and SOC input with soil depth and soil texture. SOC dynamics were determined for bulk soil and physically separated SOC fractions along three chronosequences after land use change from forest to maize (up to 21 years) in northwestern Vietnam. Consideration of the effects of soil erosion on SOC dynamics by the CIDE approach yielded a higher total SOC loss (6 to 32%), a lower decomposition (13 to 40%) and a lower SOC input (14 to 31%) relative to the values derived from a commonly applied 13C isotope based mass balance approach. Comparison of decomposition between depth layers revealed that tillage accelerated decomposition in the plough layer (0-10 cm), accounting for 3 to 34% of total decomposition. With increasing clay contents SOC input increased. In addition, decomposition increased with increasing clay contents, too, being attributed to decomposition of exposed labile SOC which was attached to clay particles in the sand sized stable aggregate fraction. This study suggests that in situ SOC dynamics on erosion prone slopes are commonly misrepresented by erosion unadjusted approaches.

  11. Point resistance of piles in sand

    OpenAIRE

    Miura, Norihiko

    1983-01-01

    Mechanism of point resistance of pile in sand was investigated mainly from the viewpoint of the particle-crushing of sand at the pile tip. It is shown that the work dissipated in the particle-crushing of sand is as large as 66 percent of the total work done by the external force, hence the point resistance of a pile in sand greatly depends on the particle-crushing property of the sand. It is also shown that the relationship between point resistance and vertical pressure of a pile can be predi...

  12. Piping flow erosion in water retaining structures: inferring erosion rates from hole erosion tests and quantifying the failure time

    OpenAIRE

    S. Bonelli; Benahmed, N.

    2010-01-01

    The piping flow erosion process, involving the enlargement of a continuous tunnel between upstream and downstream, is a major cause of water retaining structures. Such a pipe can be imputed to roots or burrows. The coefficient of erosion must be known in order to estimate the remaining time to failure and to downstream flood. The Hole Erosion test is a laboratory experiment especially suited to estimate a priori this geotechnical parameter. We propose therefore simplified expressions for the ...

  13. Modeling the fluid/soil interface erosion in the Hole Erosion Test

    OpenAIRE

    Kissi B.; Parron Vera M. Angel; Rubio Cintas M. D.; Khamlichi A.

    2012-01-01

    Soil erosion is a complex phenomenon which yields at its final stage to insidious fluid leakages under the hydraulic infrastructures known as piping and which are the main cause of their rupture. The Hole Erosion Test is commonly used to quantify the rate of piping erosion. In this work, The Hole Erosion Test is modelled by using Fluent software package. The aim is to predict the erosion rate of soil during the hole erosion test. The renormalization group theory – based k–ε turbulence model e...

  14. Morphological characteristics and sand volumes of different coastal dune types in Essaouira Province, Atlantic Morocco

    Science.gov (United States)

    Flor-Blanco, Germán; Flor, Germán; Lharti, Saadia; Pando, Luis

    2013-04-01

    Altogether three coastal dune fields, one located north and two south of the city of Essaouira, Atlantic Morocco, have been investigated to establish the distribution and overall sand volumes of various dune types. The purpose of the study was to characterize and classify the aeolian landforms of the coastal dune belt, to estimate their sand volumes and to assess the effectiveness of coastal dune stabilization measures. The northern dune field is 9 km long and lined by a wide artificial foredune complex fixed by vegetation, fences and branches forming a rectangular grid. Active and ephemeral aklé dunes border the inner backshore, while some intrusive dunes have crossed the foredune belt and are migrating farther inland. The total sand volume of the northern dune belt amounts 13,910,255 m3. The central coastal sector comprises a much smaller dune field located just south of the city. It is only 1.2 km long and, with the exception of intrusive dunes, shows all other dune types. The overall sand volume of the central dune field amounts to about 172,463 m3. The southern dune field is characterized by a narrower foredune belt and overall lower dunes that, in addition, become progressively smaller towards the south. In this sector, embryonic dunes (coppice, shadow dunes), tongue-like and tabular dunes, and sand sheets intrude from the beach, the profile of which has a stepped appearance controlled by irregular outcrops of old aeolianite and beach rock. The total volume of the southern dune field amounts 1,446,389 m3. For the whole study area, i.e. for all three dune fields combined, a sand volume of about 15,529,389 m3 has been estimated. The sand of the dune fields is derived from coastal erosion and especially the Tensift River, which enters the sea at Souira Qedima some 70 km north of Essaouira. After entering the sea, the sand is transported southwards by littoral drift driven by the mainly north-westerly swell climate and the Trade Winds blowing from the NNE. This

  15. Sensitivity of growth characteristics of tidal sand ridges and long bed waves to formulations of bed shear stress, sand transport and tidal forcing: A numerical model study

    Science.gov (United States)

    Yuan, Bing; de Swart, Huib E.; Panadès, Carles

    2016-09-01

    Tidal sand ridges and long bed waves are large-scale bedforms that are observed on continental shelves. They differ in their wavelength and in their orientation with respect to the principal direction of tidal currents. Previous studies indicate that tidal sand ridges appear in areas where tidal currents are above 0.5 m s-1, while long bed waves occur in regions where the maximum tidal current velocity is slightly above the critical velocity for sand erosion and the current is elliptical. An idealized nonlinear numerical model was developed to improve the understanding of the initial formation of these bedforms. The model governs the feedbacks between tidally forced depth-averaged currents and the sandy bed on the outer shelf. The effects of different formulations of bed shear stress and sand transport, tidal ellipticity and different tidal constituents on the characteristics of these bedforms (growth rate, wavelength, orientation of the preferred bedforms) during their initial formation were examined systematically. The results show that the formulations for bed shear stress and slope-induced sand transport are not critical for the initial formation of these bedforms. For tidal sand ridges, under rectilinear tidal currents, increasing the critical bed shear stress for sand erosion decreases the growth rate and the wavelength of the preferred bedforms significantly, while the orientation angle slightly decreases. The dependence of the growth rate, wavelength and the orientation of the preferred bedforms on the tidal ellipticity is non-monotonic. A decrease in tidal frequency results in preferred bedforms with larger wavelength and smaller orientation angle, while their growth rate hardly changes. In the case of joint diurnal and semidiurnal tides, or spring-neap tides, the characteristics of the bedforms are determined by the dominant tidal constituent. For long bed waves, the number of anticyclonically/cyclonically oriented bedforms with respect to the principal

  16. Formation of Craters in Sand

    Directory of Open Access Journals (Sweden)

    Vanissra Boonyaleepun

    2007-06-01

    Full Text Available The diameter of craters formed by spheres of varying mass dropped into sand at low speed was studied. The relationship between the diameter of the crater formed and the kinetic energy of the projectile at impact was found to be of the same general form as that for planetary meteor craters. The relationship is shown to be a power law with exponent 0.17.

  17. Formation of Craters in Sand

    OpenAIRE

    Vanissra Boonyaleepun; Se-Won Jang

    2007-01-01

    The diameter of craters formed by spheres of varying mass dropped into sand at low speed was studied. The relationship between the diameter of the crater formed and the kinetic energy of the projectile at impact was found to be of the same general form as that for planetary meteor craters. The relationship is shown to be a power law with exponent 0.17

  18. Formation of Craters in Sand

    Directory of Open Access Journals (Sweden)

    Vanissra Boonyaleepun

    2007-06-01

    Full Text Available The diameter of craters formed by spheres of varying mass dropped into sand at low speed was studied. The relationship between the diameter of the crater formed and the kinetic energy of the projectile at impact was found to be of the same general form as that for planetary meteor craters. The relationship is shown to be a power law with exponent 0.17

  19. Modular turbine airfoil and platform assembly with independent root teeth

    Science.gov (United States)

    Campbell, Christian X; Davies, Daniel O; Eng, Darryl

    2013-07-30

    A turbine airfoil (22E-H) extends from a shank (23E-H). A platform (30E-H) brackets or surrounds a first portion of the shank (23E-H). Opposed teeth (33, 35) extend laterally from the platform (30E-H) to engage respective slots (50) in a disk. Opposed teeth (25, 27) extend laterally from a second portion of the shank (29) that extends below the platform (30E-H) to engage other slots (52) in the disk. Thus the platform (30E-H) and the shank (23E-H) independently support their own centrifugal loads via their respective teeth. The platform may be formed in two portions (32E-H, 34E-H), that are bonded to each other at matching end-walls (37) and/or via pins (36G) passing through the shank (23E-H). Coolant channels (41, 43) may pass through the shank beside the pins (36G).

  20. Parametric Evaluation of Thin, Transonic Circulation-Control Airfoils

    Science.gov (United States)

    Schlecht, Robin; Anders, Scott

    2007-01-01

    Wind-tunnel tests were conducted in the NASA Langley Transonic Dynamics Tunnel on a 6 percent-thick, elliptical circulation-control airfoil with upper-surface and lower-surface blowing capability. Results for elliptical Coanda trailing-edge geometries, biconvex Coanda trailing-edge geometries, and leading-edge geometries are reported. Results are presented at subsonic and transonic Mach numbers of 0.3 and 0.8, respectively. When considering one fixed trailing-edge geometry, for both the subsonic and transonic conditions it was found that the [3.0:1] ratio elliptical Coanda surface with the most rounded leading-edge [03] performed favorably and was determined to be the best compromise between comparable configurations that took advantage of the Coanda effect. This configuration generated a maximum. (Delta)C(sub 1) = 0.625 at a C(sub mu) = 0.06 at M = 0.3, alpha = 6deg. This same configuration generated a maximum (Delta)C(sub 1) = 0.275 at a C(sub mu) = 0.0085 at M = 0.8, alpha = 3deg.

  1. Nature-Inspired Airfoils for Environmental Noise Reduction

    Science.gov (United States)

    Han, Suyeong; Kyung, Richard

    2013-11-01

    Recently, study on the insects' flapping flight became one of the challenging research subjects in the field of environmental engineering and aeronautics because of its potential applicability to intelligent micro-robots capable of autonomous flight and the next generation aerial-vehicles. In order to uncover its curious unsteady characteristics, many researchers have conducted experimental and computational studies on the unsteady aerodynamics of insects' flapping flight. In the present work, the unsteady flow physics around insect wings are conducted by utilizing numerical and computational simulation. The e-AIRS [6] (e-Science Aerospace Integrated Research System) gives a balanced service between computational and experimental aerodynamics, along with integrated research process of these two research activities. This paper presents the wing motions and their aerodynamics with a two dimensional approach to reduce environmental noise during the airflight. Also this paper shows an optimal phase angle, where the thrust is maximized at the position of minimized drag, which occurs when noise is minimized. Aside from the two-dimensional approach, stroke angles and phase angles of the airfoils are set as parameters, to determine which motion yields the best aerodynamic characteristics.

  2. Numerical analysis and optimization of boundary layer suction on airfoils

    Directory of Open Access Journals (Sweden)

    Shi Yayun

    2015-04-01

    Full Text Available Numerical approach of hybrid laminar flow control (HLFC is investigated for the suction hole with a width between 0.5 mm and 7 mm. The accuracy of Menter and Langtry’s transition model applied for simulating the flow with boundary layer suction is validated. The experiment data are compared with the computational results. The solutions show that this transition model can predict the transition position with suction control accurately. A well designed laminar airfoil is selected in the present research. For suction control with a single hole, the physical mechanism of suction control, including the impact of suction coefficient and the width and position of the suction hole on control results, is analyzed. The single hole simulation results indicate that it is favorable for transition delay and drag reduction to increase the suction coefficient and set the hole position closer to the trailing edge properly. The modified radial basis function (RBF neural network and the modified differential evolution algorithm are used to optimize the design for suction control with three holes. The design variables are suction coefficient, hole width, hole position and hole spacing. The optimization target is to obtain the minimum drag coefficient. After optimization, the transition delay can be up to 17% and the aerodynamic drag coefficient can decrease by 12.1%.

  3. Receptivity to thermal noise in real airfoil configurations

    Science.gov (United States)

    Luchini, Paolo

    2014-11-01

    Thermal noise, the macroscopic manifestation of microscopic particle agitation, is present in fluid flow just as in electron flow in conductors or in other physical transport phenomena. When the flow acts as an amplifier, typically during transition to turbulence, the transition position can be influenced by the amplitude of external disturbances through the so called receptivity of the flow instabilities; internally generated thermal noise represents a thermodynamically enforced lower bound to how much disturbances can be reduced. In a previous paper (Seventh IUTAM Symposium on Laminar-Turbulent Transition, IUTAM Bookseries Volume 18, Springer, 2010, pp. 11-18), the present author showed that the maximum transition distance in a Blasius boundary layer corresponds to a Reynolds number little above 6 .106 and to an N-factor of the order of 13. Results to be exhibited at this conference show that in a real airfoil configuration the maximum transition Reynolds number imposed by thermal noise is even lower than on a flat wall, and not far from the actually observed transition position. It follows that thermal noise might actually have a role in natural transition; and that even a perfectly silenced laboratory environment cannot push the transition position much farther. Work supported by the European Community through the RECEPT grant.

  4. Nonlinear aeroelastic analysis of airfoils: bifurcation and chaos

    Science.gov (United States)

    Lee, B. H. K.; Price, S. J.; Wong, Y. S.

    1999-04-01

    Different types of structural and aerodynamic nonlinearities commonly encountered in aeronautical engineering are discussed. The equations of motion of a two-dimensional airfoil oscillating in pitch and plunge are derived for a structural nonlinearity using subsonic aerodynamics theory. Three classical nonlinearities, namely, cubic, freeplay and hysteresis are investigated in some detail. The governing equations are reduced to a set of ordinary differential equations suitable for numerical simulations and analytical investigation of the system stability. The onset of Hopf-bifurcation, and amplitudes and frequencies of limit cycle oscillations are investigated, with examples given for a cubic hardening spring. For various geometries of the freeplay, bifurcations and chaos are discussed via the phase plane, Poincaré maps, and Lyapunov spectrum. The route to chaos is investigated from bifurcation diagrams, and for the freeplay nonlinearity it is shown that frequency doubling is the most commonly observed route. Examples of aerodynamic nonlinearities arising from transonic flow and dynamic stall are discussed, and special attention is paid to numerical simulation results for dynamic stall using a time-synthesized method for the unsteady aerodynamics. The assumption of uniform flow is usually not met in practice since perturbations in velocities are encountered in flight. Longitudinal atmospheric turbulence is introduced to show its effect on both the flutter boundary and the onset of Hopf-bifurcation for a cubic restoring force.

  5. Structural response of a fiber composite compressor fan blade airfoil

    Science.gov (United States)

    Chamis, C. C.; Minich, M. D.

    1975-01-01

    A theoretical investigation was performed to determine the structural response of a fiber composite airfoil typical of those encountered in high-tip speed compressor fan blades when subjected to load conditions anticipated in such applications. The analysis method consisted of composite mechanics embedded in pre- and post-processors coupled with NASTRAN. The load conditions examined include thermal due to aerodynamic heating, pressure due to aerodynamic forces, and centrifugal. Root reactions due to various load conditions, average composite and ply stresses, ply delaminations, and the fundamental modes and the corresponding reactions were investigated. The results show that the thermal and pressure stresses are negligible compared to those caused by the centrifugal forces. The core-shell concept for composite blades is an inefficient design and is sensitive to interply delaminations. The results are presented in graphical and tabular forms to illustrate the types and amount of data required for the analysis, and to provide quantitative data associated with the various responses which can be helpful in designing composite blades.

  6. Is splash erosion potential species specific? Measuring of splash erosion potential under forest in different succession stages along a biodiversity gradient in the humid subtropics

    Science.gov (United States)

    Geißler, C.; Kühn, P.; Scholten, T.

    2009-04-01

    It is widely accepted that (forest) vegetation is a key control for the type and intensity of soil erosion. The current paradigm is that natural or quasi-natural vegetation protects the soil from erosion and that agricultural vegetation or land use generally enhances erosion. The latter was in focus of most research during the last decades and less interest was paid on natural systems, which are more difficult to study. Nevertheless, afforestation is widely used as a measure of soil protection against soil erosion. Rainfall can be highly erosive particularly in the humid subtropics. Regarding climate change, also precipitation regime may change in direction to even more severe storms and higher rainfall intensities; it is a research field of growing importance. Key mechanisms of a vegetation cover in reducing or enhancing erosion are modifications of drop-size distribution, retention of raindrop impact on the soil and changes in amount and spatial distribution of rainfall at the ground surface. Controlling determinants are rainfall intensity, drop size distribution, drop fall velocity, height of the canopy as well as density of the canopy, crown and leaf traits, LAI and coverage by a litter layer. Large drops are supposed to be significant sources of splash detachment in forests (Brandt 1989; Vis 1986). However, the mechanisms of reducing (or enhancing?) splash detachment under forest in relation to species richness and species composition are not well understood. Some studies indicate that raindrop impact is species specific (Calder 2001; Nanko et al. 2006) and some neglect the effects of species specific impacts (Foot & Morgan 2005). Our research uses different methods of rainfall characterization (splash cups, tipping-bucket rain gauge, laser distrometer) to reveal the described mechanisms from the canopy through different vegetation layers to the ground. First results of splash cup measurements (revised after Ellison 1947) show that sand loss under vegetation

  7. Controls on Quaternary Sediment Erosion and Provenance in the Himalayan Rain Shadow, Zanskar River, Northwest India

    Science.gov (United States)

    Jonell, T. N.; Clift, P. D.; Carter, A.

    2015-12-01

    The Asian Summer Monsoon exerts strong control over erosion in the frontal Himalaya and possibly farther onto the periphery of the Tibetan Plateau in the Himalayan rain shadow. This study evaluates the Zanskar River, a large rain shadow tributary to the Indus River system, to establish how monsoonal precipitation controls erosion patterns, sediment yield, and sediment composition in the Himalayan rain shadow. Bulk sediment petrography and U-Pb detrital zircon ages demonstrate that Zanskar River sands are overwhelmingly dominated by 600-850 Ma zircon, which is consistent with material eroding from Greater Himalayan lithologies. In particular, modern sediment production appears to be heavily concentrated in the wettest and most glaciated subcatchment. River terrace sands indicate that no significant change in the area of sediment production and basin-wide provenance signal has occurred since ~11.5 ka, despite changes in monsoon strength. Variability in subcatchment provenance signals, however, do shift locally with enhanced precipitation around the time of the Monsoon Maximum (10-8 ka). Detrital apatite fission track ages suggest rates of erosion typical for the northwest Indian Himalaya for the last 6.4 M.y. in Zanskar, in spite of the changing monsoonal climate. Together these data indicate most sediment in the Zanskar River is freshly-eroded and transmitted immediately downstream into the Indus River with only modest buffering in terraces.

  8. Pelton turbine Needle erosion prediction based on 3D three- phase flow simulation

    International Nuclear Information System (INIS)

    Pelton turbine, which applied to the high water head and small flow rate, is widely used in the mountainous area. During the operation period the sediment contained in the water does not only induce the abrasion of the buckets, but also leads to the erosion at the nozzle which may damage the needle structure. The nozzle and needle structure are mainly used to form high quality cylindrical jet and increase the efficiency of energy exchange in the runner to the most. Thus the needle erosion will lead to the deformation of jet, and then may cause the efficiency loss and cavitation. The favourable prediction of abrasion characteristic of needle can effectively guide the optimization design and maintenance of needle structure. This paper simulated the unsteady three-dimensional multi-phase flow in the nozzle and injected jet flow. As the jet containing water and sediment is injected into the free atmosphere air with high velocity, the VOF model was adopted to predict the water and air flow. The sediment is simplified into round solid particle and the discrete particle model (DPM) was employed to predict the needle abrasion characteristic. The sand particle tracks were analyzed to interpret the mechanism of sand erosion on the needle surface. And the numerical result of needle abrasion was obtained and compared with the abrasion field observation. The similarity of abrasion pattern between the numerical results and field observation illustrated the validity of the 3D multi-phase flow simulation method

  9. A parametric study of thrust and efficiency of an oscillating airfoil

    Science.gov (United States)

    Mackowski, A. W.; Williamson, C. H. K.

    2012-11-01

    An oscillating airfoil serves as a classic test case for a variety of unsteady phenomena in fluid mechanics. In nature, fish, birds, and insects oscillate their fins and wings to produce thrust and maneuvering forces, often studied by approximating the appendages as airfoils. On the other hand, the unsteady fluid mechanics of an oscillating airfoil involve vortex shedding and vortex advection, which are essential to understanding unsteady thrust, and worth studying in their own right. This information is useful in areas such as flow control, fluid-structure interaction, and undersea robotics. In this work, we examine the thrust and efficiency of a heaving (or pitching) foil as a function of variables such as the reduced frequency and amplitude (noting previous related studies such as Koochesfahani 1989; Anderson et al. 1998). Further, our novel experimental ``cyber-physical'' technique [Mackowski & Williamson, 2011] allows the airfoil to propel itself under its own thrust. Our experimental apparatus constantly monitors the fluid forces acting on the foil, and commands velocity to a carriage system in accordance with these forces. With this capability, we are able to measure the terminal velocity of a self-propelled airfoil, as well as its stationary thrust and efficiency.

  10. Usage of advanced thick airfoils for the outer part of very large offshore turbines

    Science.gov (United States)

    Grasso, F.; Ceyhan, O.

    2014-06-01

    Nowadays one of the big challenges in wind energy is connected to the development of very large wind turbines with 100 m blades and 8-10MW power production. The European project INNWIND.EU plays an important role in this challenge because it is focused on exploring and exploiting technical innovations to make these machines not only feasible but also cost effective. In this context, the present work investigates the benefits of adopting thick airfoils also at the outer part of the blade. In fact, if these airfoils are comparable to the existing thinner ones in terms of aerodynamics, the extra thickness would lead to a save in weight. Lightweight blades would visibly contribute to reduce the cost of energy of the turbines and make them cost effective. The reference turbine defined in INNWIND.EU project has been adjusted to use the new airfoils. The results show that the rotor performance is not sacrificed when the 24% airfoils are replaced by the ECN 30% thick airfoils, while 24% extra thickness can be obtained.

  11. Experimental measurement of the aerodynamic charateristics of two-dimensional airfoils for an unmanned aerial vehicle

    Directory of Open Access Journals (Sweden)

    Nožička Jiří

    2012-04-01

    Full Text Available This paper is part of the development of an airfoil for an unmanned aerial vehicle (UAV with internal propulsion system; the investigation involves the analysis of the aerodynamic performance for the gliding condition of two-dimensional airfoil models which have been tested. This development is based on the modification of a selected airfoil from the NACA four digits family. The modification of this base airfoil was made in order to create a blowing outlet with the shape of a step on the suction surface since the UAV will have an internal propulsion system. This analysis involved obtaining the lift, drag and pitching moment coefficients experimentally for the situation where there is not flow through the blowing outlet, called the no blowing condition by means of wind tunnel tests. The methodology to obtain the forces experimentally was through an aerodynamic wire balance. Obtained results were compared with numerical results by means of computational fluid dynamics (CFD from references and found in very good agreement. Finally, a selection of the airfoil with the best aerodynamic performance is done and proposed for further analysis including the blowing condition.

  12. Thrust generation and wake structure for flow across a pitching airfoil at low Reynolds number

    Indian Academy of Sciences (India)

    Intesaaf Ashraf; Amit Agrawal; Majid Hassan Khan; Sooraj P; Atul Srivastava; Atul Sharma

    2015-12-01

    In this work, we present detailed particle image velocimetry (PIV) based investigation of wake structure of a pitching airfoil. PIV measurements have been carried out for NACA0015 airfoil at Re = 2900 with reduced frequency range of 1.82–10.92 and pitching angle of 5°. Two different wake structures (reverse Kármán shedding and deflected vortex shedding) are observed over this parameter range. The vorticity decreases substantially over a distance of two chord-lengths. The velocity profile indicates a jet-like flow downstream of the airfoil. It is shown that the jet-like flow downstream of the airfoil is however not a sufficient condition for the generation of thrust. The vortex strength is found to be invariant of the pitching frequency. Certain differences from the reported results are noted, which may be because of difference in the airfoil shape. These results can help improve understanding of the flow behavior as the low Reynolds number range is not well studied.

  13. Wind-Tunnel Tests on Airfoil Boundary Layer Control Using a Backward-Opening Slot

    Science.gov (United States)

    Bamber, Millard J

    1932-01-01

    This report presents the results of an investigation to determine the effect of boundary layer control on the lift and drag of an airfoil. Boundary layer control was accomplished by means of a backward-opening slot in the upper surface of the hollow airfoil. Air was caused to flow through this slot by a pressure which was maintained inside the airfoil by a blower. Various slot locations, slot openings, and wing pressures were used. The tests were conducted in the 5-foot atmospheric wind tunnel of the Langley Memorial Aeronautical Laboratory. Under the test conditions, the maximum lift coefficient was increased about 96 per cent for one slot arrangement, and the minimum drag coefficient was decreased about 27 per cent for another, both being compared with the results obtained with the unslotted airfoil. It is believed from this investigation that the above effects may be increased by the use of larger slot openings, better slot locations, multiple slots, improved airfoil profiles, and trailing edge flaps.

  14. Studi Karakteristik Aliran Tiga Dimensi Dan Perpindahan Panas Pada Cascade Airfoil Dengan Pengaruh Clearance

    Directory of Open Access Journals (Sweden)

    Yusuf Wibisono

    2013-03-01

    Full Text Available Dalam dunia teknik khususunya mekanika fluida, aliran tiga dimensi merupakan hal yang sangat penting guna untuk mengetahui fenomena aliran dan perpindahan panas yang terjadi pada bluffbody cascade airfoil. Error atau loses yang terjadi pada cascade airfoil disebabkan oleh adanya aliran sekunder. Error atau loses tersebut menurut penilitian yang terlah dilakukan dapat dikurang dengan aspek clearance. Tujuan dari penilitian ini adalah untuk menganalisa karaktersistik aliran tiga dimensi serta perpindahan panas akibat adanya perubahan jarak antara leading edge antara cascade dan sudut serang serta bentuk geometri. hasil dari simulasi divisualisasikan dalam bentuk velocity dan pressure coefficient. Pada cascade airfoil dengan sudut serang 20° terjadi fenomena pada dinding clearance yaitu tip clearance flow di mana ketika aliran udara melewati dinding akan mengalami up stream yang mengakibatkan arah aliran menuju ke atas, sedangkan pada dinding airfoil ditemukan aliran sekunder berupa curl flow yang akhirnya membentuk spiral point pada trailing edge. Perubahan sudut serang menjadi -20° membuat perbedaan tekanan antara lower side dan upper side semakin lemah, begitu juga tip clearance flow yang terjadi pada wall clearance mengalami perubahan arah menjadi down stream yang mengakibatkan arah aliran menjuu kebawah. Perubahan sudut juga berpengaruh terhadap pressure coeficient pada boundary layer airfoil dan mengakibatkan blockage effect serta terjadinya vortex yang berbeda.

  15. Airfoil data sensitivity analysis for actuator disc simulations used in wind turbine applications

    Science.gov (United States)

    Nilsson, Karl; Breton, Simon-Philippe; Sørensen, Jens N.; Ivanell, Stefan

    2014-06-01

    To analyse the sensitivity of blade geometry and airfoil characteristics on the prediction of performance characteristics of wind farms, large-eddy simulations using an actuator disc (ACD) method are performed for three different blade/airfoil configurations. The aim of the study is to determine how the mean characteristics of wake flow, mean power production and thrust depend on the choice of airfoil data and blade geometry. In order to simulate realistic conditions, pre-generated turbulence and wind shear are imposed in the computational domain. Using three different turbulence intensities and varying the spacing between the turbines, the flow around 4-8 aligned turbines is simulated. The analysis is based on normalized mean streamwise velocity, turbulence intensity, relative mean power production and thrust. From the computations it can be concluded that the actual airfoil characteristics and blade geometry only are of importance at very low inflow turbulence. At realistic turbulence conditions for an atmospheric boundary layer the specific blade characteristics play an minor role on power performance and the resulting wake characteristics. The results therefore give a hint that the choice of airfoil data in ACD simulations is not crucial if the intention of the simulations is to compute mean wake characteristics using a turbulent inflow.

  16. Computations of unsteady transonic flow over airfoil at low Reynolds number

    Institute of Scientific and Technical Information of China (English)

    ZHU Hai-tao; SHAN Peng

    2013-01-01

    Transonic flow over a thin airfoil at low Reynolds number was studied numerically by directly solving two-dimensional full Navier-Stokes equations through 5th order weighted essentially non-oscillatory (WENO) scheme without using any turbulence model.A series of distinguished unsteady phenomena for a thin 2-D transonic airfoil flow were presented.Due to continuous adverse pressure gradient in the subsonic flow downstream of the sonic line,the unsteady separated boundary layer with main vortex and secondary vortex was developed at the rear of the airfoil.At the trailing edge,the vortex-shedding was characterized by periodical connection of the main vortex and secondary vortex on the other side of the airfoil.The unsteady separation and vortex-shedding occurred with the same period.On the airfoil surface,the average pulse pressure related to the unsteady supersonic region was obviously smaller than that related to the vortex-shedding at the trailing edge.With the attack angle increasing from 0° to 2°,the frequency of vortex-shedding decreases about 4.2 %.At last,the turbulence intensity and many second-order statistics in the wake region were investigated.

  17. Flow past a self-oscillating airfoil with two degrees of freedom: measurements and simulations

    Science.gov (United States)

    Šidlof, Petr; Štěpán, Martin; Vlček, Václav; Řidký, Václav; Šimurda, David; Horáček, Jaromír

    2014-03-01

    The paper focuses on investigation of the unsteady subsonic airflow past an elastically supported airfoil for subcritical flow velocities and during the onset of the flutter instability. A physical model of the NACA0015 airfoil has been designed and manufactured, allowing motion with two degrees of freedom: pitching (rotation about the elastic axis) and plunging (vertical motion). The structural mass and stiffness matrix can be tuned to certain extent, so that the natural frequencies of the two modes approach as needed. The model was placed in the measuring section of the wind tunnel in the aerodynamic laboratory of the Institute of Thermomechanics in Nový Knín, and subjected to low Mach number airflow up to the flow velocities when self-oscillation reach amplitudes dangerous for the structural integrity of the model. The motion of the airfoil was registered by a high-speed camera, with synchronous measurement of the mechanic vibration and discrete pressure sensors on the surface of the airfoil. The results of the measurements are presented together with numerical simulation results, based on a finite volume CFD model of airflow past a vibrating airfoil.

  18. 2D CFD Analysis of an Airfoil with Active Continuous Trailing Edge Flap

    Science.gov (United States)

    Jaksich, Dylan; Shen, Jinwei

    2014-11-01

    Efficient and quieter helicopter rotors can be achieved through on-blade control devices, such as active Continuous Trailing-Edge Flaps driven by embedded piezoelectric material. This project aims to develop a CFD simulation tool to predict the aerodynamic characteristics of an airfoil with CTEF using open source code: OpenFOAM. Airfoil meshes used by OpenFOAM are obtained with MATLAB scripts. Once created it is possible to rotate the airfoil to various angles of attack. When the airfoil is properly set up various OpenFOAM properties, such as kinematic viscosity and flow velocity, are altered to achieve the desired testing conditions. Upon completion of a simulation, the program gives the lift, drag, and moment coefficients as well as the pressure and velocity around the airfoil. The simulation is then repeated across multiple angles of attack to give full lift and drag curves. The results are then compared to previous test data and other CFD predictions. This research will lead to further work involving quasi-steady 2D simulations incorporating NASTRAN to model aeroelastic deformation and eventually to 3D aeroelastic simulations. NSF ECE Grant #1358991 supported the first author as an REU student.

  19. Tests and numerical simulation of aerodynamic characteristics of airfoils for general aviation applications

    Institute of Scientific and Technical Information of China (English)

    Zhang Lizhen; Wang Xiaoming; Miguel A.González Hernández; Wang Jun

    2008-01-01

    This paper was to validate the effects of airfoil thickness ratio on the characteristics of a family of airfoils.Re-search was carried out in different ways.First,tests were conducted in the wind tunnel.And numerical simulation was performed on the basis of tests.Results from calculation were consistent with tests,indicating that numerical method could help evaluate characteristics of airfoils.Then the results were confirmed by compared with empirical data.The study also showed that the determining factor of lift is not only the thickness ratio,but the angle of attack,the relative camber and the camber line.The thickness ratio appears to have little effect on lift coefficient at zero angle of attack,since the angle of zero llft is largely determined by the airfoil camber.According to the research,numerical simulation can be used to determine the aerodynamic characteristics of airfoils in different environment such as in the dusty or hu-mid air.

  20. On the unsteady motion and stability of a heaving airfoil in ground effect

    Institute of Scientific and Technical Information of China (English)

    Juan Molina; Xin Zhang; David Angland

    2011-01-01

    This study explores the fluid mechanics and force generation capabilities of an inverted heaving airfoil placed close to a moving ground using a URANS solver with the Spalart-Allmaras turbulence model. By varying the mean ground clearance and motion frequency of the airfoil, it was possible to construct a frequency-height diagram of the various forces acting on the airfoil. The ground was found to enhance the downforce and reduce the drag with respect to freestream. The unsteady motion induces hysteresis in the forces' behaviour. At moderate ground clearance, the hysteresis increases with frequency and the airfoil loses energy to the flow, resulting in a stabilizing motion. By analogy with a pitching motion, the airfoil stalls in close proximity to the ground. At low frequencies, the motion is unstable and could lead to stall flutter. A stall flutter analysis was undertaken. At higher frequencies, inviscid effects overcome the large separation and the motion becomes stable. Forced trailing edge vortex shedding appears at high frequencies. The shedding mechanism seems to be independent of ground proximity.However, the wake is altered at low heights as a result of an interaction between the vortices and the ground.

  1. Experimental measurement of the aerodynamic charateristics of two-dimensional airfoils for an unmanned aerial vehicle

    Science.gov (United States)

    Velazquez, Luis; Nožička, Jiří; Vavřín, Jan

    2012-04-01

    This paper is part of the development of an airfoil for an unmanned aerial vehicle (UAV) with internal propulsion system; the investigation involves the analysis of the aerodynamic performance for the gliding condition of two-dimensional airfoil models which have been tested. This development is based on the modification of a selected airfoil from the NACA four digits family. The modification of this base airfoil was made in order to create a blowing outlet with the shape of a step on the suction surface since the UAV will have an internal propulsion system. This analysis involved obtaining the lift, drag and pitching moment coefficients experimentally for the situation where there is not flow through the blowing outlet, called the no blowing condition by means of wind tunnel tests. The methodology to obtain the forces experimentally was through an aerodynamic wire balance. Obtained results were compared with numerical results by means of computational fluid dynamics (CFD) from references and found in very good agreement. Finally, a selection of the airfoil with the best aerodynamic performance is done and proposed for further analysis including the blowing condition.

  2. Usage of advanced thick airfoils for the outer part of very large offshore turbines

    International Nuclear Information System (INIS)

    Nowadays one of the big challenges in wind energy is connected to the development of very large wind turbines with 100 m blades and 8-10MW power production. The European project INNWIND.EU plays an important role in this challenge because it is focused on exploring and exploiting technical innovations to make these machines not only feasible but also cost effective. In this context, the present work investigates the benefits of adopting thick airfoils also at the outer part of the blade. In fact, if these airfoils are comparable to the existing thinner ones in terms of aerodynamics, the extra thickness would lead to a save in weight. Lightweight blades would visibly contribute to reduce the cost of energy of the turbines and make them cost effective. The reference turbine defined in INNWIND.EU project has been adjusted to use the new airfoils. The results show that the rotor performance is not sacrificed when the 24% airfoils are replaced by the ECN 30% thick airfoils, while 24% extra thickness can be obtained

  3. Numerical simulation of the interaction of a vortex with stationary airfoil in transonic flow

    Science.gov (United States)

    Srinivasan, G. R.; Mccroskey, W. J.; Kutler, P.

    1984-01-01

    A perturbation form of an implicit conservative, noniterative numerical algorithm for the two-dimensional thin layer Navier-Stokes and Euler equations is used to compute the interaction flow-field of a vortex with stationary airfoil. A Lamb-like analytical vortex having a finite core is chosen to interact with a thick (NACA 0012) and a thin (NACA 64A006) airfoil independently in transonic flow. Two different configurations of vortex interaction are studied, viz., (1) when the vortex is fixed at one location in the flowfield, and (2) when the vortex is convecting past the airfoil at freestream velocity. Parallel computations of this interacting flowfield are also done using a version of the Transonic Small Disturbance Code (ATRAN2). A special treatment of the leading edge region for thin airfoils is included in this code. With this, the three methods gave qualitatively similar results for the weaker interactions considered in this study. However, the strongest interactions considered proved to be beyond the capabilities of the small disturbance code. The results also show a far greater influence of the vortex on the airfoil flowfield when the vortex is stationary than when it is convecting with the flow.

  4. Experimental study of ice accretion effects on aerodynamic performance of an NACA 23012 airfoil

    Directory of Open Access Journals (Sweden)

    Sohrab Gholamhosein Pouryoussefi

    2016-06-01

    Full Text Available In this paper, the effects of icing on an NACA 23012 airfoil have been studied. Experiments were applied on the clean airfoil, runback ice, horn ice, and spanwise ridge ice at a Reynolds number of 0.6 × 106 over angles of attack from −8° to 20°, and then results are compared. Generally, it is found that ice accretion on the airfoil can contribute to formation of a flow separation bubble on the upper surface downstream from the leading edge. In addition, it is made clear that spanwise ridge ice provides the greatest negative effect on the aerodynamic performance of the airfoil. In this case, the stall angle drops about 10° and the maximum lift coefficient reduces about 50% which is hazardous for an airplane. While horn ice leads to a stall angle drop of about 4° and a maximum lift coefficient reduction to 21%, runback ice has the least effect on the flow pattern around the airfoil and the aerodynamic coefficients so as the stall angle decreases 2° and the maximum lift reduces about 8%.

  5. Experimental study of ice accretion effects on aerodynamic performance of an NACA 23012 airfoil

    Institute of Scientific and Technical Information of China (English)

    Masoud Mirzaei; Mohammad-Mahdi Nazemi; Mojtaba Fouladi; Alireza Doostmahmoudi

    2016-01-01

    In this paper, the effects of icing on an NACA 23012 airfoil have been studied. Exper-iments were applied on the clean airfoil, runback ice, horn ice, and spanwise ridge ice at a Reynolds number of 0.6 ? 106 over angles of attack from ? 8? to 20?, and then results are compared. Gener-ally, it is found that ice accretion on the airfoil can contribute to formation of a flow separation bubble on the upper surface downstream from the leading edge. In addition, it is made clear that spanwise ridge ice provides the greatest negative effect on the aerodynamic performance of the airfoil. In this case, the stall angle drops about 10? and the maximum lift coefficient reduces about 50%which is hazardous for an airplane. While horn ice leads to a stall angle drop of about 4? and a maximum lift coefficient reduction to 21%, runback ice has the least effect on the flow pattern around the airfoil and the aerodynamic coefficients so as the stall angle decreases 2? and the maximum lift reduces about 8%.

  6. Flow past a self-oscillating airfoil with two degrees of freedom: measurements and simulations

    Directory of Open Access Journals (Sweden)

    Šidlof Petr

    2014-03-01

    Full Text Available The paper focuses on investigation of the unsteady subsonic airflow past an elastically supported airfoil for subcritical flow velocities and during the onset of the flutter instability. A physical model of the NACA0015 airfoil has been designed and manufactured, allowing motion with two degrees of freedom: pitching (rotation about the elastic axis and plunging (vertical motion. The structural mass and stiffness matrix can be tuned to certain extent, so that the natural frequencies of the two modes approach as needed. The model was placed in the measuring section of the wind tunnel in the aerodynamic laboratory of the Institute of Thermomechanics in Nový Knín, and subjected to low Mach number airflow up to the flow velocities when self-oscillation reach amplitudes dangerous for the structural integrity of the model. The motion of the airfoil was registered by a high-speed camera, with synchronous measurement of the mechanic vibration and discrete pressure sensors on the surface of the airfoil. The results of the measurements are presented together with numerical simulation results, based on a finite volume CFD model of airflow past a vibrating airfoil.

  7. Influence of sand movement in the Sahara on the erosion of pipeline network

    Directory of Open Access Journals (Sweden)

    Azari Z.

    2010-06-01

    Full Text Available The influence of sandblasting on a surface notched of pipeline with API 5L X52 steel is studied. The purpose of this study is to determine the evolution of static characteristics and lifetime of material in both directions of pipeline (Longitudinal (L and Transverse (T. Specimens were taken from a pipeline and the material damage was made by projecting corundum particles (aluminium oxide. In order to justify the evolution of mechanical properties of material, residual stress analysis was realized by the technique of X-ray diffraction. The observation of damage mode and distribution of residual stress under the notch tip show that the material hardening, the notch radius and the compressive stress, play together an important role in stabilizing the material mechanical properties.

  8. Erosion and sedimentation caused by watercourse regulation

    International Nuclear Information System (INIS)

    This report describes the observations made by SINTEF NHL in 1993 - 1994 on the development of erosion in three regulated lakes in Norway: Devdesjavri, Store Maalvatn and Gjevilvatnet. Surveys, profile levelling, water sample analyses, aerial photography etc were all used. Erosion was dramatic in all three magazines the first year of regulation and then slowed down. It has since remained relatively stable. However, there is a risk of further strong erosion connected with flooding tributaries, notably at low water such as usually occurs in spring. This is true in particular of the main river discharging into Devdesjavri, which is subject to landslides, wave and river erosion. In addition, ground water erosion may occur if the magazine is drained too fast. The report is lavishly illustrated with colour pictures of the effects of erosion. 21 refs., 15 figs., 13 tabs

  9. Sand control completion options for horizontal wells in soft formations

    Energy Technology Data Exchange (ETDEWEB)

    Penberthy, W. [Baker Oil Tools, Houston, TX (United States). Sand Control Systems Div.

    1999-02-01

    Sand control is required in most soft formations. So far, stand-alone screens have been the primary method. From completion, productivity and longevity perspectives, a high percentage of horizontal oil wells have not achieved the desired result: a sand-free, high sustained-productivity producer. Gas wells seem to have fared better. Disappointments have prompted some companies to reassess procedures and strategies involved with horizontal wells in these reservoirs. Gravel packing offers another option for completing horizontal wells, with the advantage of enhancing productivity. Gravel packing provides a means of filling and stabilizing the wellbore with high-permeability gravel, thereby avoiding the plugging and erosion noted with stand-alone screens. Recently, several operators have performed horizontal gravel packs after experiencing unacceptable performance with stand-alone screens. While each completion option has advantages and disadvantages, all have applications. Some are best suited to particular reservoirs, and as a consequence, the applicability of each completion technique must be assessed in light of particular reservoir conditions and reserves. This discussion will review various applications of soft rock completion technology in horizontal service, along with benefits and shortfalls.

  10. An Experimental Study on Aerodynamic Sound Generated from Wake Interaction of Circular Cylinder and Airfoil with Attack Angle in Tandem

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    In our previous study, the effects of the interval between the cylinder and the airfoil on the aerodynamic sound were investigated and compared with the cases of single circular and single airfoil. In this study, the effects of the attack angle of the airfoil located downstream on the characteristics of aerodynamic sound and the wake structure are investigated at a given interval between the cylinder and the airfoil. It is found that the sound pressure level of DFN and the peak frequency decrease with increasing attack angle of airfoil because of the diffusive wake structure due to the increased back pressure of circular cylinder, which is caused by the blocking effect of airfoil. It is shown that the sound sources are corresponded to the attack points of shedding vortex form the upstream circular cylinder to the downstream airfoil. We conclude that the pressure fluctuation at the airfoil surface effects on the sound pressure level, from the flow visualizations and the exploration test of sound source.

  11. Lagrangian and Eulerian pressure field evaluation of rod-airfoil flow from time-resolved tomographic PIV

    NARCIS (Netherlands)

    Violato, D.; Moore, P.; Scarano, F.

    2010-01-01

    This work investigates the rod-airfoil air flow by time-resolved Tomographic Particle Image Velocimetry (TR-TOMO PIV) in thin-light volume configuration. Experiments are performed at the region close to the leading edge of a NACA0012 airfoil embedded in the von Karman wake of a cylindrical rod. The

  12. Simulation of cold heavy oil production using an integrated modular approach with emphasis on foamy oil flow and sand production effects

    Energy Technology Data Exchange (ETDEWEB)

    Wang, J.; Walters, D.A. [Taurus Reservoir Solutions Ltd., Calgary, AB (Canada); Settari, A.; Wan, R.G. [Calgary Univ., AB (Canada)

    2006-07-01

    Cold heavy oil production with sand (CHOPS) is now a widely-used non-thermal oil recovery process. The process operates by producing sand to create wormholes and foamy oil drive. This paper presented a model that used an integrated modular approach to predict volumetric sand production. The model was based on a mixture theory with erosion mechanics in which multiphase hydrodynamics and geomechanics were coupled to determine saturation, pressure, porosity and formation displacements. Foamy oil was modelled as a dispersion of gas bubbles trapped in the oil. A modular approach was adopted in order to integrate stress-strain codes. The model was then integrated within erosion, reservoir, and geomechanics modules. Stress, flow, and erosion equations were solved within different time increments. Coupling terms were iterated until convergence was achieved on a time step basis. Typical vertical and horizontal wells in northeast Alberta were used to test the coupled model. Results showed that enhanced oil recovery (EOR) and sand production can be predicted by accounting for the effects of sand production and foamy oil flow. It was concluded that the model can be used for wellbore stability analyses and in the design of pumping strategies. 18 refs., 1 tab., 17 figs.

  13. Erosion products in disruption simulation experiments

    Energy Technology Data Exchange (ETDEWEB)

    Safronov, V.; Arkhipov, N.; Bakhtin, V.; Barsuk, V.; Kurkin, S.; Mironova, E.; Toporkov, D.; Vasenin, S.; Zhitlukhin, A. [Troitsk Inst. for Innovation and Fusion Research, Troisk, Moscow region (Russian Federation); Arkhipov, I. [Inst. of Physical Chemistry, Russian Academy of Science, Moscow (Russian Federation); Werle, H.; Wuerz, H. [Forschungszentrum Karlsruhe (Germany)

    1998-07-01

    Erosion of divertor materials under tokamak disruption event presents a serious problem of ITER technology. Erosion restricts the divertor lifetime and leads to production of redeposited layers of the material retaining large amount of tritium, which is a major safety issue for future fusion reactor. Since ITER disruptive heatloads are not achievable in existing tokamaks, material erosion is studied in special simulation experiments. Till now the simulation experiments have focused mainly on investigation of shielding effect and measurement of erosion rate. In the present work the properties of eroded and redeposited graphite are studied under condition typical for hard ITER disruption. (author)

  14. Erosion behavior and mechanism of boronised steels

    Institute of Scientific and Technical Information of China (English)

    刘立; 凌国平; 刘涛; 郦剑

    2002-01-01

    Boronising of steels is a hardening process to get high surface hardness. The erosion resistance of boronised steels was researched with the use of four kinds of erodent, i.e. glass, alumina, quartz and silicon carbide. The erosion rate increases rapidly with erodent hardness and severe erosion occurs with high impacting angle range of hard particles. SEM analysis indicated that chipping is caused by repetitive impacting of glass and quartz, whereas by alumina and silicon carbide impacting, chipping, and that plastic flow take place simultaneously and the erosion rate reaches the peak value when the impacting angle is above 60°.

  15. Erosion behavior and mechanism of boronised steels

    Institute of Scientific and Technical Information of China (English)

    刘立; 凌国平; 刘涛; 郦剑

    2002-01-01

    Boronising of steels is a hardening process to get high surfaoe hardness. The erosion resis-tance of boronised steels was researched with the use of four kinds of erodent, i.e. glass, alumina,quartz and silicon carbide. The erosion rate increases rapidly with erodent hardness and severe erosion occurs with high impacting angle range of hard particles. SEM analysis indicated that chipping is caused by repetitive impacting of glass and quartz, whereas b.y alumina and silicon carbide impacting, chipping,and that plastic flow .take place simultaneously and the erosion rate reaches the peak value when the impacting angle is above 60°.

  16. Robotic weld overlay coatings for erosion control

    Science.gov (United States)

    The erosion of materials by the impact of solid particles has received increasing attention during the past twenty years. Recently, research has been initiated with the event of advanced coal conversion processes in which erosion plays an important role. The resulting damage, termed Solid Particle Erosion (SPE), is of concern primarily because of the significantly increased operating costs which result in material failures. Reduced power plant efficiency due to solid particle erosion of boiler tubes and waterfalls has led to various methods to combat SPE. One method is to apply coatings to the components subjected to erosive environments. Protective weld overlay coatings are particularly advantageous in terms of coating quality. The weld overlay coatings are essentially immune to spallation due to a strong metallurgical bond with the substrate material. By using powder mixtures, multiple alloys can be mixed in order to achieve the best performance in an erosive environment. However, a review of the literature revealed a lack of information on weld overlay coating performance in erosive environments which makes the selection of weld overlay alloys a difficult task. The objective of this project is to determine the effects of weld overlay coating composition and microstructure on erosion resistance. These results will lead to a better understanding of erosion mitigation in CFB's.

  17. INFLUENCES OF SLOPE GRADIENT ON SOIL EROSION

    Institute of Scientific and Technical Information of China (English)

    刘青泉; 陈力; 李家春

    2001-01-01

    The main factors influencing soil erosion include the net rain excess, the water depth, the velocity, the shear stress of overland flows , and the erosion-resisting capacity of soil. The laws of these factors varying with the slope gradient were investigated by using the kinematic wave theory. Furthermore, the critical slope gradient of erosion was driven. The analysis shows that the critical slope gradient of soil erosion is dependent on grain size , soil bulk density , surface roughness, runoff length, net rain excess, and the friction coefficient of soil, etc. The critical slope gradient has been estimated theoretically with its range between 41. 5 °~ 50°.

  18. Pond 1 : closure of the first oil sands tailings pond

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, H.B.; Wells, P.S.; Cox, L [Suncor Energy, Fort McMurray, AB (Canada)

    2010-10-01

    This article discussed the closure and reclamation of the first oilsands tailings pond in the Athabasca Oil Sands region. Pond 1 began construction in 1966, received tailings until 1995, and was released for reclamation in 2007. Infilling was completed in 2009, and surface land forming and revegetation were finished in the fall of 2010. The challenges associated with closing a tailings pond were unknown. Environmental goals evolved over the life of the pond, from initial absence to grass cover to prevent wind erosion, tree plantings for wildlife habitat, and finally to reclamation to viable ecosystems compatible with pre-development. The final stage involved infilling and reclamation of the pond interior. The Mature Fine Tailings were removed to a different location for storage and treatment. Infilling with course tailings sand established a trafficable surface on which to perform reclamation activities. The landform design involved a sand pile that had become bird habitat; a small marsh wetland; swales to collect and control surface runoff water; and hummocks for topographical diversity and increased biodiversity. The reclamation soil cover was a peat/mineral mix. Micro-topographical enhancements created locally diverse conditions for wildlife habitat. An excavated area was lined with a geosynthetic material for water retention, amended with peat/mineral mix, and planted with wetland species to create the marsh. The revegetation involved 33 different species of trees, shrubs, grasses, and aquatic plants. The pond closure is taking place in a highly regulated environment with a substantial knowledge base of reclamation techniques and clearly defined reclamation goals. 8 figs.

  19. Preliminary Investigation on Boundary Layer Control by Means of Suction and Pressure with the U.S.A. 27 Airfoil

    Science.gov (United States)

    Reid, E G; Bamber, M J

    1928-01-01

    The tests described in this report constitute a preliminary investigation of airfoil boundary layer control, as carried out in the atmospheric wind tunnel of the Langley Memorial Aeronautical Laboratory, from February to August, 1927. Tests were made on a U.S.A. 27 airfoil section with various slot shapes and combinations, and at various amounts of pressure or suction on the slots. The lift of airfoils can be increased by removing or by accelerating the boundary layer. Removing the boundary layer by suction is more economical than to accelerate it by jet action. Gauze-covered suction slots apparently give the best results. When not in operation, all suction slots tested had a detrimental effect upon the aerodynamic characteristics of the airfoil which was not apparent with the backward-opening pressure slots. Thick, blunt-nose airfoils would seem to give best results with boundary layer control.

  20. Calculated Low-Speed Steady and Time-Dependent Aerodynamic Derivatives for Some Airfoils Using a Discrete Vortex Method

    Science.gov (United States)

    Riley, Donald C.

    2015-01-01

    This paper contains a collection of some results of four individual studies presenting calculated numerical values for airfoil aerodynamic stability derivatives in unseparated inviscid incompressible flow due separately to angle-of-attack, pitch rate, flap deflection, and airfoil camber using a discrete vortex method. Both steady conditions and oscillatory motion were considered. Variables include the number of vortices representing the airfoil, the pitch axis / moment center chordwise location, flap chord to airfoil chord ratio, and circular or parabolic arc camber. Comparisons with some experimental and other theoretical information are included. The calculated aerodynamic numerical results obtained using a limited number of vortices provided in each study compared favorably with thin airfoil theory predictions. Of particular interest are those aerodynamic results calculated herein (such as induced drag) that are not readily available elsewhere.

  1. The leading-edge stall of airfoils with various nose shapes

    Science.gov (United States)

    Kraljic, Matthew; Rusak, Zvi; Wang, Shixiao

    2015-11-01

    We study the inception of leading-edge stall on stationary, smooth thin airfoils with various nose shapes of the form xa (where 0 nose, that asymptotically match each other. The flow in the outer region is dominated by the classical thin airfoil theory. Scaled (magnified) coordinates and a modified (smaller) Reynolds number ReM are used to correctly account for the nonlinear behavior and extreme velocity changes in the inner region, where both the near-stagnation and high suction areas occur. The inner region problem is solved numerically to determine the inception of leading-edge stall on the nose. It is found that stall is delayed to higher angles of attack with the decrease of nose parameter a. Specifically, new airfoil shapes are proposed with increased stall angle at subsonic speeds and higher critical Mach numbers at transonic speeds.

  2. Limit cycle oscillation suppression of 2-DOF airfoil using nonlinear energy sink

    Institute of Scientific and Technical Information of China (English)

    郭虎伦; 陈予怒; 扬天智

    2013-01-01

    This paper presents a novel mechanical attachment, i.e., nonlinear energy sink (NES), for suppressing the limit cycle oscillation (LCO) of an airfoil. The dynamic responses of a two-degree-of-freedom (2-DOF) airfoil coupled with an NES are studied with the harmonic balance method. Different structure parameters of the NES, i.e., mass ratio between the NES and airfoil, NES offset, NES damping, and nonlinear stiffness in the NES, are chosen for studying the effect of the LCO suppression on an aeroelastic system with a supercritical Hopf bifurcation or subcritical Hopf bifurcation, respectively. The results show that the structural parameters of the NES have different influence on the supercritical Hopf bifurcation system and the subcritical Hopf bifurcation system.

  3. Experimental characterization of airfoil boundary layers for improvement of aeroacoustic and aerodynamic modeling

    DEFF Research Database (Denmark)

    Fischer, Andreas

    2011-01-01

    blades makes a transition from laminar to turbulent. In the turbulent boundary layer eddies are created which are a potential noise sources. They are ineffective as noise source on the airfoil surface or in free flow, but when convecting past the trailing edge of the airfoil their efficiency is much......The present work aims at the characterization of aerodynamic noise from wind turbines. There is a consensus among scientists that the dominant aerodynamic noise mechanism is turbulent boundary trailing edge noise. In almost all operational conditions the boundary layer flow over the wind turbine...... increased and audible sound is radiated. We performed measurements of the boundary layer velocity fluctuations and the fluctuating surface pressure field in two different wind tunnels and on three different airfoils. The first wind tunnel is the one of LM Wind Power A/S following the classic concept...

  4. Effects of the impeller inlet tip clearance on the flow and performance of airfoil fans

    Energy Technology Data Exchange (ETDEWEB)

    Kang, S.H. [Seoul National University, Seoul (Korea); Kim, Y.J. [Seoul National University Graduate School, Seoul (Korea)

    1999-08-01

    Performance tests of an airfoil fan and measurement of flow fields at the impeller exit are carried out to investigate the effects of the tip clearance between the rotor and inlet casing on the impeller performance. The impeller is twelve bladed of NACA 65-810 airfoils and tested with 3 different size of gap; 1, 2, 4{sup mm}. The relative decrease of pressure rising performance of the fan is 15 percent for the design flow rate when the gap size is 1 percent of the impeller diameter. The reduction of performance becomes large as the flow rate increases. The leakage flow through the clearance affects the through flow of the impeller, which results in decrease of the slip factor as well as the impeller efficiency. The data base obtained in the present study can be used for the design and flow analysis of the airfoil fans. (author). 4 refs., 19 figs., 1 tab.

  5. A SIMPLIFIED THEORY FOR UNSTEADY AERODYNAMIC FORCES ACTING ON AN AIRFOIL FLYING ABOVE SEA-WAVES

    Institute of Scientific and Technical Information of China (English)

    SHENG Qi-hu; WU De-ming; ZHANG Liang

    2004-01-01

    A simplified theoretical method based on the quasi-steady wing theory was proposed to study the unsteady aerodynamic forces acting on an airfoil flying in non-uniform flow. Comparison between the theoretical results and the numerical results based on nonlinear theory was made. It shows that the simplified theory is a good approximation for the investigation of the aerodynamic characteristics of an airfoil flying above sea-waves. From on the simplified theory it is also found that an airfoil can get thrust from a wave-disturbed airflow and thus the total drag is reduced. And the relationship among the thrust, the flying altitude, the flying speed and the wave parameters was worked out and discussed.

  6. Aerodynamic Design of Airfoils Based on Variable-Domain Variational Finite Element Method

    Institute of Scientific and Technical Information of China (English)

    陈池; 刘高联

    2005-01-01

    Designing airfoils according to given pressure (or velocity) distribution is one kind of free boundary problems. Free boundary condition can be coupled with the flow governing equations by variable-domain variational calculus, which makes it possible to calculate simultaneously the flow field and the free boundary. An accurate deduction of the variable-domain variational principles is taken herein to design airfoils in compressible and incompressible flows. Furthermore, two grid types (H and O) are used in the calculation with better results for the O-type grid. It is shown that convergence is accelerated and good results can be obtained even if the initial guessed airfoil shape is a triangle, demonstrating the strong adaptability of this method.

  7. Comparison of two design methods of aerodynamic biobjectives for airfoil and wing shapes

    Institute of Scientific and Technical Information of China (English)

    ZHU; Ziqiang; FU; Hongyan; LIU; Hang; WANG; Xiaolu

    2004-01-01

    A simplified adaptive wing, which deflects its leading edge and trailing edge flaps to vary its shape, is calculated to investigate the potential aerodynamic gains and compared with a biobjective optimization (BO) wing in the present paper. In subsonic-transonic flights the deflection angle of a flap is determined through optimization using a deterministic method. In supersonic flight the flaps are not deflected due to the requirement of having a minimum drag. For comparison the aerodynamic characteristics of a BO airfoil and wing is calculated. A parallel genetic algorithm is used in BO. Euler equations served as governing equations in flow field calculation. Numerical results in both 2D (airfoil) and 3D (wing) cases show that aerodynamic performances of the two design airfoils and wings are much better than those of the original ones, with the adaptive design one the best.

  8. Shape Optimization of NREL S809 Airfoil for Wind Turbine Blades Using a Multiobjective Genetic Algorithm

    Directory of Open Access Journals (Sweden)

    Yilei He

    2014-01-01

    Full Text Available The goal of this paper is to employ a multiobjective genetic algorithm (MOGA to optimize the shape of a well-known wind turbine airfoil S809 to improve its lift and drag characteristics, in particular to achieve two objectives, that is, to increase its lift and its lift to drag ratio. The commercially available software FLUENT is employed to calculate the flow field on an adaptive structured mesh using the Reynolds-Averaged Navier-Stokes (RANS equations in conjunction with a two-equation k-ω SST turbulence model. The results show significant improvement in both lift coefficient and lift to drag ratio of the optimized airfoil compared to the original S809 airfoil. In addition, MOGA results are in close agreement with those obtained by the adjoint-based optimization technique.

  9. Wind Tunnel Tests of Wind Turbine Airfoils at High Reynolds Numbers

    Science.gov (United States)

    Llorente, E.; Gorostidi, A.; Jacobs, M.; Timmer, W. A.; Munduate, X.; Pires, O.

    2014-06-01

    Wind tunnel tests have been performed to measure the two-dimensional aerodynamic characteristics of two different airfoil families at high Reynolds numbers (from 3 to 12 millions) in the DNW High Pressure Wind Tunnel in Gottingen (HDG), Germany. Also, tests at a Reynolds number of 3 millions have been performed in the Low-Speed Low- Turbulence Wind Tunnel of Delft University, The Netherlands. The airfoils tested belong to two wind turbine dedicated families: the TU-Delft DU family and the ACCIONA Windpower AWA family that was designed in collaboration with CENER. Reynolds number effects on airfoil performance have been obtained in the range of 3 to 12 millions. The availability of data from two different wind tunnels has brought the opportunity to cross compare the results from the two facilities.

  10. Airfoil data sensitivity analysis for actuator disc simulations used in wind turbine applications

    DEFF Research Database (Denmark)

    Nilsson, Karl; Breton, Simon-Philippe; Sørensen, Jens Nørkær;

    2014-01-01

    and blade geometry only are of importance at very low inflow turbulence. At realistic turbulence conditions for an atmospheric boundary layer the specific blade characteristics play an minor role on power performance and the resulting wake characteristics. The results therefore give a hint that the choice......To analyse the sensitivity of blade geometry and airfoil characteristics on the prediction of performance characteristics of wind farms, large-eddy simulations using an actuator disc (ACD) method are performed for three different blade/airfoil configurations. The aim of the study is to determine...... how the mean characteristics of wake flow, mean power production and thrust depend on the choice of airfoil data and blade geometry. In order to simulate realistic conditions, pre-generated turbulence and wind shear are imposed in the computational domain. Using three different turbulence intensities...

  11. Experimental studies of the boundary layer on an airfoil at low Reynolds numbers

    Science.gov (United States)

    Jansen, B. J., Jr.; Mueller, T. J.

    1983-01-01

    An experimental wind tunnel investigation was carried out to study the effect of laminar separation bubbles on a NACA 66(3)-018 airfoil for Reynolds numbers less than 4.0 x 10 to the 5th. Leading edge laminar separation bubbles formed for angles of attack of approximately 7 to 12 deg. To study the leading edge separation bubble more closely, hotwire anemometer measurements were made in the airfoil a Reynolds number of 8.0 x 10 to the 4th. Velocity and turbulence intensity profiles were obtained and boundary layer parameters were calculated. Frequency spectra were also calculated at key points in the airfoil boundary layer for this case. Correlation of the anemometry data with static pressure distributions, and flow visualization data provided insight into laminar separation bubble behavior at low Reynolds numbers.

  12. CFD simulation of flow-induced vibration of an elastically supported airfoil

    Science.gov (United States)

    Šidlof, Petr

    2016-03-01

    Flow-induced vibration of lifting or control surfaces in aircraft may lead to catastrophic consequences. Under certain circumstances, the interaction between the airflow and the elastic structure may lead to instability with energy transferred from the airflow to the structure and with exponentially increasing amplitudes of the structure. In the current work, a CFD simulation of an elastically supported NACA0015 airfoil with two degrees of freedom (pitch and plunge) coupled with 2D incompressible airflow is presented. The geometry of the airfoil, mass, moment of inertia, location of the centroid, linear and torsional stiffness was matched to properties of a physical airfoil model used for wind-tunnel measurements. The simulations were run within the OpenFOAM computational package. The results of the CFD simulations were compared with the experimental data.

  13. Calculation of compressible boundary layer flow about airfoils by a finite element/finite difference method

    Science.gov (United States)

    Strong, Stuart L.; Meade, Andrew J., Jr.

    1992-01-01

    Preliminary results are presented of a finite element/finite difference method (semidiscrete Galerkin method) used to calculate compressible boundary layer flow about airfoils, in which the group finite element scheme is applied to the Dorodnitsyn formulation of the boundary layer equations. The semidiscrete Galerkin (SDG) method promises to be fast, accurate and computationally efficient. The SDG method can also be applied to any smoothly connected airfoil shape without modification and possesses the potential capability of calculating boundary layer solutions beyond flow separation. Results are presented for low speed laminar flow past a circular cylinder and past a NACA 0012 airfoil at zero angle of attack at a Mach number of 0.5. Also shown are results for compressible flow past a flat plate for a Mach number range of 0 to 10 and results for incompressible turbulent flow past a flat plate. All numerical solutions assume an attached boundary layer.

  14. Comparison of Evolutionary (Genetic) Algorithm and Adjoint Methods for Multi-Objective Viscous Airfoil Optimizations

    Science.gov (United States)

    Pulliam, T. H.; Nemec, M.; Holst, T.; Zingg, D. W.; Kwak, Dochan (Technical Monitor)

    2002-01-01

    A comparison between an Evolutionary Algorithm (EA) and an Adjoint-Gradient (AG) Method applied to a two-dimensional Navier-Stokes code for airfoil design is presented. Both approaches use a common function evaluation code, the steady-state explicit part of the code,ARC2D. The parameterization of the design space is a common B-spline approach for an airfoil surface, which together with a common griding approach, restricts the AG and EA to the same design space. Results are presented for a class of viscous transonic airfoils in which the optimization tradeoff between drag minimization as one objective and lift maximization as another, produces the multi-objective design space. Comparisons are made for efficiency, accuracy and design consistency.

  15. Compressible dynamic stall vorticity flux control using a dynamic camber airfoil

    Indian Academy of Sciences (India)

    M S Chandrasekhara

    2007-02-01

    This study reports control of compressible dynamic stall through management of its unsteady vorticity using a variable droop leading edge (VDLE) airfoil. Through dynamic adaptation of the airfoil edge incidence, the formation of a dynamic stall vortex was virtually eliminated for Mach numbers of up to 0·4. Consequently, the leading edge vorticity flux was redistributed enabling retention of the dynamic lift. Of even greater importance was the fact that the drag and pitching moment coefficients were reduced by nearly 50%. The camber variations introduced when the leading edge was drooped are explained to be the source of this benefit. Analysis of the peak vorticity flux levels allowed the determination of minimum necessary airfoil adaptation schedule.

  16. Investigation on Improved Correlation of CFD and EFD for Supercritical Airfoil

    Directory of Open Access Journals (Sweden)

    Xin Xu

    2014-02-01

    Full Text Available It is necessary to improve the correlation between CFD and EFD through the correction of EFD results and validation of CFD method, thus investigating the aerodynamic characteristics of supercritical airfoil perfectly. In this study, NASA SC (2 -0714 airfoil is numerically simulated and compared with NASA corrected experimental results to validate the CFD method. The Barnwell-Sewell method is applied to correct sidewall effects for experimental results of typical supercritical airfoil CH obtained in NF-6 wind tunnel. It is shown that there was large disparity between CFD and uncorrected EFD results, while CFD and EFD compared well after correction. The CFD method is validated and the Barnwell-Sewell method is feasible for sidewall effects correction. The correlation of EFD and CFD improved after the correction of EFD results and validation of CFD method.

  17. CFD simulation of flow-induced vibration of an elastically supported airfoil

    Directory of Open Access Journals (Sweden)

    Šidlof Petr

    2016-01-01

    Full Text Available Flow-induced vibration of lifting or control surfaces in aircraft may lead to catastrophic consequences. Under certain circumstances, the interaction between the airflow and the elastic structure may lead to instability with energy transferred from the airflow to the structure and with exponentially increasing amplitudes of the structure. In the current work, a CFD simulation of an elastically supported NACA0015 airfoil with two degrees of freedom (pitch and plunge coupled with 2D incompressible airflow is presented. The geometry of the airfoil, mass, moment of inertia, location of the centroid, linear and torsional stiffness was matched to properties of a physical airfoil model used for wind-tunnel measurements. The simulations were run within the OpenFOAM computational package. The results of the CFD simulations were compared with the experimental data.

  18. Probabilistic Design of Hollow Airfoil Composite Structure by Using Finite Element Method

    Directory of Open Access Journals (Sweden)

    Mr. Sachin M. Shinde

    2014-04-01

    Full Text Available This study represents simulation of Airfoil composite beam by using Monte Carlo method. A three dimensional static analysis of large displacement type has been carried out. Finite element analysis of NACA0012 airfoil composite structure has been carried out and uncertainty in bending stress is analyzed. Bending stress was objective function. Chord length , beam length ,elastic modulus in XY,YZ,XZ and shear modulus of epoxy graphite in XY,YZ,XZ, ply angle and ply thickness of airfoil section, force are varied within effective range and their effect on bending stress has been analyzed. In order to validate the results, one loop of simulation is benchmarked from results in literature. Ultimately, best set of probabilistic design variable is proposed to reduce bending stress under static loading condition.

  19. [Environmental toxicity of waste foundry sand].

    Science.gov (United States)

    Zhang, Hai-Feng; Wang, Yu-Jue; Wang, Jin-Lin; Huang, Tian-You; Xiong, Ying

    2013-03-01

    The metal leaching characteristics and volatile organic compounds (VOCs) of five different types of waste foundry sands were analyzed with the toxicity characteristic leaching procedure (TCLP) and head space-gas chromatography (HS-GC). Microtox and soil dehydrogenase activity (DHA) tests were then used to evaluate the bio-effects of these waste sands. The results showed that due to the different metals poured and casting materials used to make the sand molds, there was significant difference among the five waste foundry sands in the compositions and concentrations of metal and organic pollutants. The concentrations of Fe in the leachates of iron and steel casting waste foundry sand exceeded the maximal allowable concentrations specified in the National Standard of Drinking Water Quality, whereas the As concentration in the leachate of aluminum casting waste foundry sand exceeded the standard. The five waste foundry sands had quite different compositions and levels of VOCs, which resulted in different levels of inhibition effects on the luminescent bacteria (30% and 95%). Additionally, the soil DHA tests suggested that metal pollutants in waste foundry sands may inhibit the soil microbial activity, whereas organics in the sands may slightly promote the microbial activity. The results of this study indicated that the waste foundry sands may pose considerable threat to the environment when improperly disposed. PMID:23745431

  20. Provenance control on chemical indices of weathering (Taiwan river sands)

    Science.gov (United States)

    Garzanti, Eduardo; Resentini, Alberto

    2016-05-01

    Geochemical parameters obtained from the analysis of sediments and sedimentary rocks are widely used to infer weathering and paleo-weathering conditions in source areas. Chemical indices of weathering, however, may not reflect weathering only, or even principally. The concentration of chemical elements in terrigenous sediments is constrained by the original mineralogy of source rocks, and is thus provenance-dependent. Moreover, the mineralogy and consequently the geochemistry of sediments may undergo substantial modifications by diverse physical processes during transport and deposition, including recycling and hydraulic sorting by size, density or shape, and/or by chemical dissolution and precipitation during diagenesis. Around the island of Taiwan, temperature and rainfall are consistently high and relatively homogeneous, and no significant correlation is observed between geochemical and climatic parameters. Physical erosion, fostered by landslides induced by frequent earthquakes and typhoons, prevails because of high relief and extreme rates of tectonic uplift. In such a dynamic orogenic setting, all chemical indices of weathering are controlled principally by the geology of source terranes. Sedimentaclastic and metasedimentaclastic sands carried by western Taiwan rivers draining the pro-wedge display the strongest depletion in Na, Ca, Mg and Sr relative to average upper continental crust, and no depletion or even enrichment in K, Rb and Ba. Low WIP indices reflect erosion of phyllosilicate-dominated rocks in the Slate Belt and extensive recycling of clastic rocks exposed in the Western Foothills. Instead, metamorphiclastic sands carried by eastern Taiwan rivers draining the retro-wedge show no depletion or even enrichment in Mg and Ca, and low CIA and PIA, reflecting contributions from the Tailuko Belt and Coastal Range. Volcaniclastic sands have the same CIA values of their andesitic source rocks (47 ± 1 versus 47 ± 7), indicating that weathering is