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Viewing 1 to 30 of 726
2011-04-12
Technical Paper
2011-01-0272
David C. Viano, Chantal Parenteau, Roger Burnett
Objective: This study analyzed available rear impact sled tests with Starcraft-type seats that use a diagonal belt behind the seatback. The study focused on neck responses for out-of-position (OOP) and in-position seated dummies. Methods: Thirteen rear sled tests were identified with out-of-position and in-position 5 th , 50 th and 95 th Hybrid III dummies in up to 47.6 mph rear delta Vs involving Starcraft-type seats. The tests were conducted at Ford, Exponent and CSE. Seven KARCO rear sled tests were found with in-position 5 th and 50 th Hybrid III dummies in 21.1-29.5 mph rear delta Vs involving Starcraft-type seats. In all of the in-position and one of the out-of-position series, comparable tests were run with production seats. Biomechanical responses of the dummies and test videos were analyzed.
2004-04-20
Technical Paper
2004-01-1817
Scott Gilchrist, Daniel Ewing, Chan Ching, Joseph Brand, Michael Dowhan
A new aero-engine nose cone anti-icing system using a rotating heat pipe has been proposed to replace the current method of blowing hot compressor bleed air over the nose cone surface. Here, the heat is transferred from a hot source within the engine to the nose cone through a rotating heat pipe along the central fan shaft. A compact evaporator is used at the evaporator end due to space constraints in the engine. The system is modeled as a thermal resistance network where the thermo-fluid dynamics of each component determine the resistors. This paper reviews each of the component models and results, which show that the evaporator thermal resistance is one of the limiting factors for adequate transfer of heat for anti-icing.
2011-06-13
Technical Paper
2011-38-0001
Jie Xiao, Katherine E. Mackie, Joseph H. Osborne, Jill Seebergh, Santanu Chaudhuri
In-flight icing occurs when supercooled water droplets suspended in the atmosphere impinge on cold aircraft surfaces. Thin layers of accreted ice significantly increase aerodynamic drag while thick layers of ice severely alter the aerodynamics of control surfaces and lift. Chunks of ice can break away from the airframe and cowlings and be ingested into engines causing considerable damage. Developing durable surfaces that prevent the nucleation of supercooled water or reduce ice adhesion to a point where airstream shear forces can remove it would allow the design of a more robust, energy efficient deicing/anti-icing system for aircraft and other applications. In this work, a simulations based framework is developed to predict anti-icing performance of various nanocomposite coatings under the in-flight environment.
2011-06-13
Technical Paper
2011-38-0013
Marco Fossati, Wagdi G. Habashi, Guido Baruzzi
The high computational cost of 3-D viscous turbulent aero-icing simulations is one of the main limitations to address in order to more extensively use computational fluid dynamics to explore the wide variety of icing conditions to be tested before achieving aircraft airworthiness. In an attempt to overcome the computational burden of these simulations, a Reduced Order Modeling (ROM) approach, based on Proper Orthogonal Decomposition (POD) and Kriging interpolation techniques, is applied to the computation of the impingement pattern of supercooled large droplets (SLD) on aircraft. Relying on a suitable database of high fidelity full-order simulations, the ROM approach provides a lower-order approximation of the system in terms of a linear combination of appropriate functions. The accuracy of the resulting surrogate solution is successfully compared to experimental and CFD results for sample 2-D problems and then extended to a typical 3-D case.
2011-06-13
Technical Paper
2011-38-0015
Robert Narducci, Tonja Reinert
The desire to operate rotorcraft in icing conditions has renewed the interest in developing high-fidelity analysis methods to predict ice accumulation and the ensuing rotor performance degradation. A subset of providing solutions for rotorcraft icing problems is predicting two-dimensional ice accumulation on rotor airfoils. While much has been done to predict ice for fixed-wing airfoil sections, the rotorcraft problem has two additional challenges: first, rotor airfoils tend to experience flows in higher Mach number regimes, often creating glaze ice which is harder to predict; second, rotor airfoils oscillate in pitch to produce balance across the rotor disk. A methodology and validation test cases are presented to solve the rotor airfoil problem as an important step to solving the larger rotorcraft icing problem. The process couples Navier-Stokes CFD analysis with the ice accretion analysis code, LEWICE3D.
2011-06-13
Technical Paper
2011-38-0014
Jason Wright, Roger J. Aubert
As part of icing certification flight test programs, artificial ice shapes are typically installed onto aircraft fixed leading edges in order to quantify changes to the handling qualities and performance characteristics of the aircraft in icing conditions. Artificial ice shapes allow a test team to evaluate what are generally the worst combinations of flight conditions for different ice protection system configurations. The goal of this paper is to discuss the details behind the design, development, construction, and installation of artificial ice shapes as they pertained to the evaluation of the need for horizontal stabilizer ice protection on the BA609 Tiltrotor with a focus on the extrapolation methods used to design the shapes.
2011-06-13
Technical Paper
2011-38-0005
Jason Mickey, Eric Loth, Colin Bidwell
A new technique is proposed for computing particle concentrations and fluxes with Lagrangian trajectories. This method calculates particle concentrations based on the volume of a parcel element, or cloud, at the flux plane compared against the initial volume and is referred to as the Lagrangian Parcel Volume (LPV) method. This method combines the steady-state accuracy of area-based methods with the unsteady capabilities of bin-based methods. The LPV method results for one-dimensional (1D) unsteady flows and linear two-dimensional (2D) steady flows show that a quadrilateral element shape composed of a single parcel (with four edge particles) is capable of accurately predicting particle concentrations. However, nonlinear 2D flows can lead to concave or crossed quadrilaterals which produce significant numerical errors.
2011-06-13
Technical Paper
2011-38-0004
Peng Ke, Xinxin Wang
Lagrangian approach has been widely adopted in the droplet impingement analysis for aircraft icing simulation. Some improvements were proposed, including: 1) The heat and mass transfer consideration in droplet dynamics; 2) More efficient droplet localization method, which could and facilitated to find the initial cell in Eulerian grid; 3) New computation method of impingement efficiency, which uses the cover ratio to transform the impingement efficiency of arbitrary impinged region to that of the cell element of body surface and avoids the iterative computation to find the trajectories reaching the corner of the panel or cell element. A numerical solver was built and integrated with the capabilities to deal with super-cooled large droplet (SLD) conditions by considering the splashing and bouncing of SLD. The computational results were validated with the experiment data, which shown good agreements in the impingement limitations and tendency.
2011-06-13
Technical Paper
2011-38-0006
Robert J. Flemming, Philip Alldridge
Sikorsky Aircraft certificated the Model S-92A™ helicopter for flight in icing conditions in 2005. Since that time, the aircraft has flown in icing conditions throughout the world and the approval to launch a flight when icing conditions are forecast or reported has been valuable to operators. However, when the rotor ice protection system was inoperative due to a system failure, use of the aircraft on days of forecast icing was prohibited. Sikorsky Aircraft, therefore, elected to obtain certification of the S-92A helicopter to an EASA limited icing Special Condition so that UK and Norwegian operators in the North Sea sector could complete a mission when icing conditions were forecast, should the RIPS be inoperative on that day. A review of previously available icing data indicated that the S-92A helicopter could meet the requirements of the EASA Special Condition, but that additional flights were required to demonstrate full compliance.
2011-06-13
Technical Paper
2011-38-0022
Marco Fossati, Rooh-ul-Amin Khurram, Wagdi G. Habashi
The irregular shapes that glaze ice may grow into while accreting over the surface of an aircraft represent a major difficulty in the numerical simulation of long periods of in-flight icing. In the framework of Arbitrary Lagrangian-Eulerian (ALE) formulations, a mesh movement scheme is presented, in which frame and elasticity analogies are loosely coupled. The resulting deformed mesh preserves the quality of elements, especially in the near-wall region, where accurate prediction of heat flux and shear stresses are required. The proposed scheme handles mesh movement in a computationally efficient manner by localizing the mesh deformation. Numerical results of ice shapes and the corresponding aerodynamic coefficients are compared with the experimental results.
2011-06-13
Technical Paper
2011-38-0021
Ben C. Bernstein, Frank Mcdonough, Cory Wolff
A large database is being created from icing flight programs completed by aircraft manufacturers for certification and by the NASA-Glenn Research Center for basic research. Although not yet complete, this database already provides an excellent opportunity to study aircraft icing conditions sampled in a wide variety of environments across eastern Canada and most of the United States, including Alaska. In this study, the focus is a comparison of conditions found within boundary-layer stratocumulus icing clouds over the Great Lakes, Pacific Northwest and Alaskan Interior. The clouds will be characterized in terms of temperature, liquid water content, median volumetric diameter, and drop concentration. Critical factors driving these parameters will be discussed.
2011-06-13
Technical Paper
2011-38-0024
Isik A. Ozcer, Guido S. Baruzzi, Thomas Reid, Wagdi G. Habashi, Marco Fossati, Giulio Croce
Numerically predicted roughness distributions obtained in in-flight icing simulations with a beading model are used in a quasi-steady manner to compute ice shapes. This approach, called "Multishot," uses a number of steady flow and droplet solutions for computing short intervals (shots) of the total ice accretion time. The iced geometry, the grid, and the surface roughness distribution are updated after each shot, producing a better match with the unsteady ice accretion phenomena. Comparisons to multishot results with uniform roughness show that the evolution of the surface roughness distribution has a strong influence on the final ice shape. The ice horns that form are longer and thinner compared to constant roughness results. The constant roughness approach usually fails to capture the formation of the pressure side horns and under-predicts the thickness of the ice in this region.
2011-06-13
Technical Paper
2011-38-0023
Guilherme Araujo Lima da Silva, Marcos Noboru Arima, Natashe Nicoli Branco, Marcos de Mattos Pimenta
This paper proposes wall function models to simulate the heat transfer around a cylinder in cross flow with an isothermal and rough surface. The selected case has similitudes with aircraft wing icing: the ice roughness shape, height and distribution. Moreover, the flow is somewhat similar to that found on iced airfoil; and the surface is isothermal like when icing. The Reynolds-Averaged Navier-Stokes, turbulence, energy and mass conservation 7-equation system is solved by two Computational Fluid Dynamics (CFD) codes. To represent accurately the effects of roughness on the heat transfer, the present authors had to modify both codes and to propose new thermal wall functions for them. In addition, it was implemented a momentum wall function that is not so common in CFD codes but it is a standard in aircraft icing simulation.
2011-06-13
Technical Paper
2011-38-0016
Tonja Reinert, Robert J. Flemming, Robert Narducci, Roger J. Aubert
A team from the USA rotorcraft industry, NASA, and academia was established to create a validated high-fidelity computational fluid dynamics (CFD) icing tool for rotorcraft. Previous work showed that an oscillating blade with a periodic variation in angle of attack causes changes in the accreted ice shape and this makes a significant change in the airfoil drag. Although there is extensive data for ice accumulation on a stationary airfoil section, high-quality icing-tunnel data on an oscillating airfoil is scarce for validating the rotorcraft icing problem. In response to this need, a two-dimensional (2D) oscillating airfoil icing test was recently performed in the Icing Research Tunnel at the NASA Glenn Research Center. Three leading-edge specimens for an existing 15-inch chord test apparatus were designed and instrumented to provide the necessary data for the CFD code validation.
2011-06-13
Technical Paper
2011-38-0020
Cory Wolff, Frank Mcdonough, Ben Bernstein
In the continental United States east of the Rocky Mountains cold fronts are quite common in wintertime due to the many cyclones moving through this region, and icing conditions in the vicinity of cold fronts are a major contributor to the overall occurrence of icing in the atmosphere. The conditions examined in this study will be those behind the cold front. Icing there is often found in stratocumulus clouds that form due to destabilization of the boundary layer through cold air advection and an inversion formed by subsidence aloft which caps their growth. Moist adiabatic lapse rates, small drop sizes, high drop concentrations, and moderate to high liquid water contents depending on the cloud depth often characterize these clouds.
2011-06-13
Technical Paper
2011-38-0067
Nathalie Alegre, David Hammond
This study reports aerodynamic properties of two runback ice shapes molded from a mid-span full scale B737 aerofoil leading edge together with a series of simplistic ice shapes of the type sometimes used by aircraft manufacturers to mimic performance loss due to runback ice. The runback ice shapes were taken from a study of runback ice growth which had produced flexible silicone rubber moulds. These moulds were used to produce ice shapes without curvature which, together with the “simplistic” shapes were mounted on flat plates and installed into the Cranfield University 8 by 6 foot wind tunnel. A boundary layer suction system was used to match the wall conditions more closely to what would be anticipated on a real aerofoil. The icing conditions approximate to a hold case with the two shapes representing a 4 and a 10 mm thick runback shape. The aerodynamic tests have been performed with a tunnel speed of 45 m/s.
2011-06-13
Technical Paper
2011-38-0068
Jakob Tendel, Cory Wolff
This study presents an evaluation of in-flight icing severity forecasts produced for the eastern United States for the winter 09/10 using the German ADWICE icing forecasting system. An instance of the underlying COSMO-EU 7km model was run over the eastern CONUS to produce four months worth of NWP data for the ADWICE algorithm. The generated icing fields were then verified using pilot reports (PIREPS) as “truth” data. In order to be able to characterize ADWICE performance over this non-native domain against a known quantity for this part of the world, a comparative verification was performed with the American FIP icing product over 1.5 months of data, using a unified set of observation PIREPS and forecast times. Subsequently, ADWICE forecasts were verified over the whole time period and analyzed with respect to seasonal, regional or altitude variations.
2011-06-13
Technical Paper
2011-38-0069
Daniel R. Adriaansen, Cory Wolff, Frank Mcdonough
The Current Icing Product (CIP) provides an hourly diagnosis of the severity of icing occurring based on multiple data sources. Pilot reports (PIREPs) and surface observations (METARs), as well as satellite, numerical weather prediction (NWP) model, radar, and lightning data are all utilized within the algorithm. The accurate identification of cloud base is a large factor in the algorithm's determination of icing severity. Current methods employ the METAR observation of ceiling to identify the cloud base over a specified area within the CIP domain. The temperature from the Rapid Update Cycle (RUC) NWP model at the height of the observed METAR ceiling can be utilized as a proxy for the amount of condensate in the cloud. The likelihood of a large amount of condensate in the identified cloud increases with increasing cloud base temperature. As the amount of liquid water diagnosed by CIP severity increases, so does the estimated icing severity.
2011-06-13
Technical Paper
2011-38-0070
Ben C. Bernstein, Erik Gregow, Ian Wittmeyer, Jarkko Hirvonen
Concepts from algorithms that use observations and numerical model output to diagnose icing conditions aloft also apply well in the near-surface environment, where icing can affect wind turbines, power lines, communications towers and more. The LOWICE system is being developed to leverage proven in-flight icing knowledge to create real-time assessments of the near-surface icing environment.
2011-06-13
Technical Paper
2011-38-0064
Jafar Alzaili, David Hammond
The objective of this work is to investigate the thin water film characteristics by performing a range of experiments for different icing conditions. Our focus is on the SLD conditions where the droplets are larger and other effects like splashing and re-impingement could occur. Three features for the thin water film have been studied experimentally: the water film velocity, wave celerity and its wavelength. The experiments are performed in the icing facilities at Cranfiled University. The stability of the water film for the different conditions has been studied to find a threshold for transient from continues water film to non-continues form. A new semi-empirical method is introduced to estimate the water film thickness based on the experimental data of water film velocity in combination of theoretical analysis of water film dynamics. The outcome of this work could be implemented in SLD icing simulation but more analysis is needed.
2011-06-13
Technical Paper
2011-38-0065
Andy P. Broeren, Sam Lee, Gautam H. Shah, Patrick C. Murphy
An experimental research effort was begun to develop a database of airplane aerodynamic characteristics with simulated ice accretion over a large range of incidence and sideslip angles. Wind-tunnel testing was performed at the NASA Langley 12-ft Low-Speed Wind Tunnel using a 3.5% scale model of the NASA Langley Generic Transport Model. Aerodynamic data were acquired from a six-component force and moment balance in static-model sweeps from α = -5 to 85 deg. and β = -45 to 45 deg. at a Reynolds number of 0.24x10⁶ and Mach number of 0.06. The 3.5% scale GTM was tested in both the clean configuration and with full-span artificial ice shapes attached to the leading edges of the wing, horizontal and vertical tail. Aerodynamic results for the clean airplane configuration compared favorably with similar experiments carried out on a 5.5% scale GTM.
2011-06-13
Technical Paper
2011-38-0066
Phillip J. Ansell, Michael B. Bragg, Michael F. Kerho
A stall prediction method based on unsteady hinge moment measurements was previously developed from experimental hinge moment measurements on a NACA 3415 airfoil model under a clean configuration and four iced configurations. The stall prediction algorithm was based on three separate detector functions. Additional hinge moment measurements have been obtained experimentally for a NACA 23012 airfoil model, using these same clean and iced configurations. Tests were also conducted with boundary-layer trips on the model upper and lower surfaces. The addition of simulated icing degraded the performance of the NACA 23012. Upon application of the hinge moment stall prediction method, two of the six configurations provided detector function outputs that were inconsistent with the other four configurations. Further investigation revealed differences in the hinge moment signal between contamination configurations due to the presence of different types and extents of primary stall mechanisms.
2011-06-13
Technical Paper
2011-38-0054
Daniel Martins Silva, Luis Gustavo Trapp
In order to correctly predict an aircraft ice accretion, the ice prediction tool shall be capable of predicting the aerodynamic characteristics of both clean and iced airfoil and be able to predict the shape of the ice accreted on both wind tunnel and actual aircraft geometries. This requires the analysis tool to be able to correctly predict the local airflow on aerodynamic surfaces that have large separation regions, as well as local water impingement, freezing, convective cooling and evaporation rates. The capability of different RANS models to predict the aerodynamic degradation of an iced airfoil is evaluated.
2011-06-13
Technical Paper
2011-38-0055
Richard Moser, Roger Gent
The European Union (EU) ‘Clean Sky’ [1] Joint Technology Initiative (JTI) is a research programme aimed at developing breakthrough technologies which will minimise the impact of aviation on the environment. Within this, the System for Green Operations (SGO) Integrated Technology Demonstrator (ITD) looks to improve aircraft operation through management of energy and mission trajectory. As part of the SGO ITD, a series of environmental icing tests have been conducted on an ice protected, acoustically protected, electrically powered, scoop intake and channel. The range of conditions tested included in-flight icing (CS-25 Appendix C, same as 14 CFR 25), super-cooled large droplets (proposed 14 CFR 25 Appendix O, [2]), snow and ice crystal conditions as well as ground icing in freezing fog conditions.
2011-06-13
Technical Paper
2011-38-0051
Jamie Braid, Patrick Van Wie, Jeffrey Rex
Aircraft icing continues to be a challenge for the aviation community. Icing is predominantly reported by pilots based on subjective visual observations of relatively small ice thicknesses at distances greater than such estimates can consistently be made. While some technologies exist to sense the presence of aircraft icing, there is a need to objectively sense the presence of ice, determine the rate of ice accumulation, and concurrently measure weather conditions to support, validate, and report the icing indication. AirDat LLC has developed an airborne atmospheric sensing device that includes a built-in ice detector which transmits icing information directly to the ground in real time. These data can be received directly by the aircraft operator or provided to any number of aviation entities to improve the safety of the National Air Space (NAS).
2011-06-13
Technical Paper
2011-38-0053
John Hallett
An operational definition of a mixed phase environment, as ice and water, from the viewpoint of its role in aircraft icing is approached from a consideration that the physical properties of any accreted mix are necessarily dependent, through the aircraft penetration velocity, on the spatial distribution of such a mix. Aircraft measurement of such an environment depends on a high response (0.1seconds, some10m of flight path) instrument (the T probe) capable of independent measurement of ice and water and thus capable of distinguishing between all water and all ice environments. The physical properties of such a mix are ill understood, yet are critical to their surface flow and ultimate freezing behavior. Such highly resolved measurements are necessary, since although the frequency occurrence of such mixes may be less than ice and water alone, their consequences may be enduring should the aircraft trajectory happen to lie along a frontal or developing hurricane weather system.
2011-06-13
Technical Paper
2011-38-0044
Michael P. Kinzel, Ralph W. Noack, Christian M. Sarofeen, David Boger, Richard Eric Kreeger
In this work, a newly developed iced-aircraft modeling tool is applied to wings, engine inlets, and helicopter rotors. The tool is based on a multiscale-physics, unstructured finite-volume CFD approach and is applicable to general purpose aircraft icing applications. The present approach combines an Eulerian-based droplet-trajectory solver that is loosely coupled, in a time-accurate manner, to a surface-film and ice-evolution model. The goal of the model is to improve the fidelity of ice accretion modeling on dynamic geometries and for three-dimensional ice shapes typical of helicopter rotors. The numerical formulation is discussed and presented alongside 2D and 3D static validation cases, and dynamic helicopter rotors. The present results display good validation for predicting ice shape on a variety of geometries, and a strong initial capability of modeling ice forming on helicopters in forward flight.
2011-06-13
Technical Paper
2011-38-0043
Chao Wang, Shi-nan Chang, Xin-ming Su
Euler method was used in calculating the gas-liquid two-phase flow field. With the help of the user defined function (UDF) in FLUENT software, the water local collection efficiency and ice accretion on three dimensional wings were solved. The flow motion of runback water was divided along the chordwise and spanwise direction respectively during the computation procedure and the classical Messinger model was modified to be applicable to simulate three dimensional ice accretion. The analysis about three dimensional mass and heat transfer was also performed according to the modified Messinger model. Based on the traditional method of calculating heat transfer coefficient on two dimensional surfaces, an improved method was applied to compute the heat transfer coefficient on three dimensional wings. The direction of ice accretion was defined to be normal to the wing surface. The comparative results showed that the three dimensional ice accretion code developed in this paper was effective.
2011-06-13
Technical Paper
2011-38-0034
Michael Papadakis, Alonso O. Zamora Rodriguez, Rodrigo Hoffmann Domingos
Results from a two-dimensional computer model developed at Wichita State University (WSU) for bleed air system analysis are compared with experimental data from icing tunnel tests performed with a wing model equipped with a hot air ice protection system. The computer model combines a commercial Navier-Stokes flow solver with a steady-state thermodynamic analysis model that applies internal flow heat transfer correlations to compute wing leading edge skin temperatures and the location and extent of the runback ice. The icing tunnel data used in the validation of the computer model were obtained at the NASA Icing Research Tunnel using representative in-flight icing conditions and a range of bleed air system mass flows and hot air temperatures. Correlation between experiment and analysis was good for most of the test cases used to assess the performance of the simulation model.
2011-06-13
Technical Paper
2011-38-0041
Douglas Spangenberg, Patrick Minnis, William Smith, Fu-Lung Chang
Cloud properties retrieved from satellite data are used to diagnose aircraft icing threat in single layer and multilayered ice-over-liquid clouds. The algorithms are being applied in real time to the Geostationary Operational Environmental Satellite (GOES) data over the CONUS with multilayer data available over the eastern CONUS. METEOSAT data are also used to retrieve icing conditions over western Europe. The icing algorithm's methodology and validation are discussed along with future enhancements and plans. The icing risk product is available in image and digital formats on NASA Langley ‘s Cloud and Radiation Products web site, http://www-angler.larc.nasa.gov.
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