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Viewing 31 to 60 of 16146
2015-06-15
Technical Paper
2015-01-2136
Francisco José Redondo
Due to weight constraints, the engine air intake for the Airbus A400M Transport Airplane will be all made in aluminum, and by specification, the intake is protected against ice accretion by a hot air system. In order to assure a fatigue life of the element for the life of the airplane, the temperature of the air supplied must be controlled to a maximum value consistent with aluminum characteristics. A system has been designed wherein hot air is bled and cooled by coolant air from inside the nacelle with a jet pump.While maximum temperature was a constraint for the design of the system, several other constraints appeared during the detailed design of the system; - the tight space allocation inside the nacelle limited the length of the jet pump, - the low temperature provided by the engine bleed in flight idle limited the secondary flow used to cool the engine bleed, and - the complex air distribution needed to supply air to the intake areas. Two variants of the system were developed.
2015-06-15
Technical Paper
2015-01-2137
Daniel R. Adriaansen, Paul Prestopnik, George McCabe, Marcia Politovich
Advancements in numerical weather prediction (NWP) modeling continue to enhance the quality of in-flight icing forecasts and diagnoses. When performing a diagnosis of current in-flight icing conditions, observational datasets can be combined with NWP model output to form a more accurate representation. These diagnoses are traditionally tied to a three-dimensional grid, typically the grid of the NWP model data chosen for use. Surface observations are heavily relied upon when performing in-flight icing diagnoses to identify cloud coverage and cloud base height above observing stations. One of the major challenges of using these point-based or otherwise limited observations of cloud properties is extending the influence of the observation to nearby points on the grid. For example, we seek an improved solution to the problem of combining point-based METARs observations with NWP model grids over the current method.
2015-06-15
Technical Paper
2015-01-2152
Earle Williams, Michael Donovan, David J. Smalley, Robert G. Hallowell, Elaine P. Griffin, Kenta T. Hood, Betty J. Bennett
MIT Lincoln Laboratory is tasked by the U.S. Federal Aviation Administration to investigate the use of the NEXRAD polarimetric radars for the remote sensing of icing conditions hazardous to aircraft. A critical aspect of the investigation concerns validation that has relied upon commercial airline icing pilot reports and a dedicated campaign of in situ flights in winter storms. During the month of February in 2012 and 2013, the CONVAIR 580 aircraft operated by the National Research Council of Canada was used for in situ validation of snowstorm characteristics under simultaneous observation by NEXRAD radars in Cleveland, Ohio and Buffalo, New York. The most anisotropic and easily distinguished winter targets to dual pol radar are ice crystals.
2015-06-15
Technical Paper
2015-01-2144
James MacLeod, Michael Clarke, Doug Marsh
The GLACIER Icing Facility – Lessons Learnt in the first Five Years of Operation J.D. MacLeod M. Clarke National Research Council of Canada Rolls-Royce plc Gas Turbine Laboratory Civil Aerospace Ottawa, ON Derby, UK Abstract The Global Aerospace Centre for Icing and Environmental Research Inc. (GLACIER) facility is located in Thompson, Manitoba, Canada. This facility provides icing certification tests for large gas turbine engines, as well as performance, endurance and other gas turbine engine qualification testing. This globally unique outdoor engine test and certification facility was officially opened back in 2010. The prime purpose of this facility is for icing certification of aero gas turbines. The facility provides the aviation industry with the required environmental conditions (by virtue of its location), and the capability to meet the growing demands for icing certifications and other adverse cold weather conditions.
2015-06-15
Technical Paper
2015-01-2076
Caroline Laforte, Neal Wesley, Marc Mario Tremblay
In North America, about ten million kilograms of runway deicers are applied on airport runways to ensure safe takeoffs and landings of aircraft in adverse conditions. Although some of the chemicals are recovered, much of them are dispersed through aviation operations to airport’s surrounding environment. Little focus has been given into assessing and determining optimal quantities of deicers to be used on runways, that at the same time retain a high degree of safety, while reducing risks to the environment and improving airport efficiencies. Improved deicer performance tests would allow for the development of more environmentally sustainable deicers, through their improved performance. A better assessment of their deicing and anti-icing performance along with their degree of skid resistance on runway pavement, will help in the development of the next generation of runway de/anti-icing chemicals to ensure improved sustainable and safe aircraft takeoffs and landings.
2015-06-15
Technical Paper
2015-01-2108
Julien Cliquet, Christian Bartels, Carlos Bautista
SAE Aircraft , Engines, Structures Icing Conference, 22-25 June 2015, Prague A combined post-processing method for SLD modeling J. Cliquet, C. Bartels, C. Bautista-Infante, Airbus Operations Abstract Supercooled Large Droplets (SLD) have taken an increasingly important place in the airframe icing over the past 15 years. Awareness of the aircraft SLD icing hazard has focused particular attention following several aircraft accidents, especially that of the ATR-72 on 31 October 1994 (Ref. [1]). The actual certification envelope defined by 14 CFR Part 25 Appendix C: Atmospheric Icing Conditions for Aircraft Certification, accounts for an icing envelope characterized by water droplet diameters up to 50 μm. International airworthiness authorities have jointly developed an extension of Appendix "C", named "Appendix O", to account for SLD conditions in the aircraft certification process.
2015-06-15
Technical Paper
2015-01-2103
Christian Bartels, Julien Cliquet, Carlos Bautista
Icing is a phenomenon observed on aircraft airframes while flying through clouds of supercooled droplets. The phenomenon only occurs for ambient air temperatures below the freezing point. The droplets impinge on the aircraft surfaces and freeze, leading to ice accretion. The resulting change in aircraft geometry and surface roughness can modify the aircraft’s aerodynamic characteristics (lift loss, drag increase), it may affect air data probe measurements, and can even damage the engines by ice ingestion. In order to comply with certification regulations, airframers have to demonstrate safe operation of their aircraft in icing conditions. However, due to associated cost and time, it is prohibitive to cover the whole icing envelope by flight-testing or icing-tunnel testing. Therefore, aircraft manufacturers have developed, with support from research institutes, numerical prediction methods and tools to cover their prediction needs.
2015-06-15
Technical Paper
2015-01-2158
Tatsuma Hyugaji, Shigeo Kimura, Haruka Endo, Mitsugu Hasegawa, Hirotaka Sakaue, Katsuaki Morita, Yoichi Yamagishi, Nadine Rehfeld, Benoit Berton, Francesc Diaz, Tarou Tanaka
Recently coatings have been considered as promising preventive measures for in-cloud icing which may occur at the leading edge area of the lifting surface of aircraft in cold climate. In terms of the wettability, coating reveals hydrophobicity or hydrophilicity depending on its property. At the same time it has high or low values on the ice adhesion strength. It is then required that users should find out which of anti-icing or de-icing coating can apply to in order to make full use of the distinguished characteristics. For all that, coating cannot prevent ice accretion by itself unfortunately, which means that no perfect icephobic coatings have been developed up to the present. Thus, coatings apply to the surfaces with devices such as an electric heating system or a load-applying machine such that they can function with less energy and more effectiveness.
2015-06-15
Technical Paper
2015-01-2124
Amanda Gounou, Jean-Marc Moisselin, Frédéric Autones, Jean-Louis Brenguier, Dominique Levaillant, Eric Défer, Michael Faivre, Sandra Turner, Fabien Dezitter, Alice Grandin
Icing conditions are often encountered in the vicinity of deep convective clouds. Nowcasting of these conditions would be of a great help for flight safety and air traffic management but still remains challenging. In the framework of the HAIC (High Altitude Ice Crystals) project [1], the nowcasting of icing conditions due to ice particles is investigated. A major field campaign has been carried out in Darwin, Australia, from 16th January to 7th March 2014, during the rainy season to sample meteorological conditions potentially leading to icing [2]. There were 23 research flights with on-board in-situ and remote sensing instruments measuring or estimating ice water content within oceanic mature thunderstorms which offered a great opportunity to implement, test and cross-validate nowcasting tools to detect and track cloud regions of high ice water content.
2015-06-15
Technical Paper
2015-01-2084
Benedikt König, Ehab Fares, Andy P. Broeren
A new laser-scanning method was applied to capture the three-dimensional ice shapes created during ice-accretion test on a NACA 23012 airfoil conducted in the NASA Icing Research Tunnel. This facilitated the creation of high-fidelity digital surface representations of complex ice-shapes. Those digital shapes cannot only be used to create rapid-prototyping models for experimental simulations, but also serve as input for computational fluid dynamics (CFD) simulations. In the past, numerical simulations of iced airfoils and wings were typically based on simplified. But, independent of the complexity of the ice shape, current numerical methods often struggle with the complicated, highly unsteady separated flows occurring under iced conditions. In this work we present simulations based on the Lattice-Boltzmann methodology (LBM) and investigate it’s capability to simulate the flow around three-dimensional laser-scanned ice shapes.
2015-06-15
Technical Paper
2015-01-2130
Melissa Bravin, J. Walter Strapp, Jeanne Mason
In response to the occurrence of jet engine powerloss and damage events associated with deep convective clouds containing high concentrations of ice crystals, several research efforts are underway. Several flight measurement programs devoted to the collection of in-situ and remote sensing of clouds have been conducted over the past few years. The most recent in Darwin, Australia, from January-March 2014, and its follow-up planned for Cayenne, French Guiana, in May 2015, involve the use of a highly instrumented research aircraft with instrumentation specially designed to make accurate in-situ total water content (TWC) and median mass diameter (MMD) measurements of the high concentration areas of deep convection. The data will be used for atmospheric research related to understanding the microphysics of deep convection, and improving the ability to predict, detect and avoid these clouds.
2015-06-15
Technical Paper
2015-01-2078
Alric Rothmayer, Hui Hu
A strong air/water interaction theory is used to develop a fast simplified model for the trapping of water in a film that flows over sub-grid surface roughness. The sub-grid model is used to compute correction factors that can alter mass transport within the film. This sub-grid model is integrated into a covariant film mass transport model for film flow past three-dimensional surfaces of a form suitable for aircraft icing codes. Sample calculations are presented to illustrate the application of the model. Aircraft icing codes usually consist of an aerodynamic solver, a droplet trajectory solver and a mechanism to grow the ice surface. Recently, icing codes have also made use of simple models for surface water transport, typically through a film lubrication model.
2015-06-15
Technical Paper
2015-01-2127
Andrea Munzing, Franck Hervy, Stephane Catris
A helicopter blade profile was tested in the DGA Aero-engine’s S1 icing wind tunnel in Saclay, France in winter 2013/2014. The 2D airfoil was a helicopter main rotor blade profile. Ice accretion tests have been performed to assess the profile’s time dependant aerodynamic behaviour during ice accretion. Real ice shapes were collected after each icing test. Moreover, iced profile polars were realized over a large range of angle of attack until stall. This paper presents the test set up, the test model and the test results. The test results presented in this paper are dry air and iced profile polars as well as ice shapes. The complete iced profile polars and the aerodynamic behaviour in time of the iced blade profile during ice accretion will be used for adjusting and validating prediction tools like Airbus Helicopter’s analytical iced rotor performance degradation model and they will aid to appraise the rotor loads evolution in icing conditions.
2015-06-15
Technical Paper
2015-01-2093
Maxime Henno
A numerical tool has been developed for predicting the unsteady behavior of the thermal wing ice protection systems (WIPS). The code was developed to account for a multi-layer composite structure. The performance predictions of a WIPS integrated into a metallic or into a composite structure can thus be achieved. The tool enables the simulation of unsteady anti-icing operations, for example, the WIPS may be activated with delay after entering into the icing conditions. In this case, ice starts to accrete on the leading edge before the WIPS heats up the skin. Another example is the ground activation of the WIPS for several seconds to check its functionality: low external cooling may cause high thermal constraints that must be estimated with accuracy to avoid adverse effects on the structure. The simulations give further opportunities compared to the current practice.
2015-06-15
Technical Paper
2015-01-2099
Mario Vargas, Charles Ruggeri, Peter Struk, Mike Pereira, Duane Revilock, Richard Kreeger
Ice Particle Impacts on a Flat Plate Mario Vargas, Peter M. Struk, Richard E. Kreeger, Charles Ruggeri, Mike Pereira, Duane Revilock National Aeronautics and Space Administration Glenn Research Center An experimental study was conducted at the Ballistic Laboratory of NASA Glenn Research Center to study the impact of ice particles on a stationary flat surface target set at 45 degrees with respect to the direction of motion of the impinging particle (Figure 1). The experiment is part of NASA efforts to study the physics involved in engine power-loss events due to ice-crystal ingestion and ice accretion formation inside engines. These events can occur when aircraft encounter high-altitude convective weather. The experiment was conducted to gain understanding of the physics involved when ice particles impact on a flat surface. Previous studies conducted by industry in the 1990s on the ingestion of ice particles in turbine engines were for hailstones.
2015-06-15
Technical Paper
2015-01-2094
William B. Wright, Peter Struk, Tadas Bartkus, Gene Addy
This paper will describe two recent modifications to the GlennICE software. First, a capability for modeling ice crystals and mixed phase icing has been modified based on recent experimental data. Modifications have been made to the ice particle bouncing and erosion model. This capability has been added as part of a larger effort to model ice crystal ingestion in aircraft engines. Comparisons have been made to ice crystal ice accretions performed in the NRC Research Altitude Test Facility (RATFac). Second, modifications were made to the runback model based on data and observations from thermal scaling tests performed in the NRC Altitude Icing Tunnel. Introduction Mason[1] describes a situation where an aircraft engine can encounter rollbacks and flameouts at high altitude conditions due to ice crystal ingestion. Numerous in-fight encounters had been observed. It was hypothesized that the cause of the incidents was the ingestion of a high volume of ice crystals into the engine.
2015-06-15
Technical Paper
2015-01-2080
Roger J. Aubert
While the industry is making consistent progress in predicting aerodynamic performance impact from ice accretion on rotor blade and ability to reliably design thermal anti-icing and/or deicing protection systems, ice shedding, natural or induced, is trailing behind both in terms of understanding the physics of impact ice adhesion and cohesion, mechanical fracture and energy dissipation upon impact on airframe or rotor systems. It is only recently that attention dedicated to the understanding of impact ice shedding on rotors has increased. Reference 1 summarizes the mechanical properties of ice. However, more recent test results (Reference 2 and 3) showed different results. It was therefore concluded that a data base more representative of helicopter operation was necessary. It is the intent of this paper to summarize the differences in test results and provide additional considerations for analytical modeling of the ice shedding process on a rotor blade.
2015-06-15
Technical Paper
2015-01-2132
David L. Rigby, Joseph Veres, Colin Bidwell
Three dimensional Navier-Stokes simulations of the Honeywell ALF502 low pressure compressor using the NASA Glenn code Glenn-HT have been carried out. A total of eight operating points were investigated. These operating points are at, or near, points where engine icing has been determined to be likely. The results of this study are expected to be used immediately, and in the future, for further analysis such as predicting collection efficiency of ice particles and ice growth rates at various locations in the compressor. A mixing plane boundary condition is used between each blade row, resulting in convergence to steady state within each blade row. Results for two levels of approximation are discussed. The first set of cases were run allowing all of the solid surfaces to slip (i.e. inviscid). That is, the velocity boundary layers are not resolved. This allows for much smaller grids and shorter run times.
2015-06-15
Technical Paper
2015-01-2131
Colin Bidwell, David Rigby
A flow and ice particle trajectory analysis was performed for the booster of the Honeywell ALF502 engine. The analysis focused on two closely related conditions one of which produced an icing event and another which did not during testing of the ALF502 engine in the Propulsion Systems Lab (PSL) at NASA Glenn Research Center. The flow analysis was generated using the NASA Glenn GlennHT flow solver and the particle analysis was generated using the NASA Glenn LEWICE3D v3.61 ice accretion software. The inflow conditions for the two conditions were similar with the main difference being that the condition that produced the icing event was 6.8 K colder than the non-icing event case. The particle analysis, which considered sublimation, evaporation and phase change, was generated for a 5 micron ice particle with a sticky impact model and for a 24 micron, 7 bin ice particle distribution with an SLD splash model used to simulate ice particle breakup.
2015-06-15
Technical Paper
2015-01-2133
Joseph P. Veres, Scott M. Jones, Philip C. E. Jorgenson
The Propulsion Systems Laboratory (PSL), an altitude test facility at NASA Glenn Research Center, has been used to test a full scale turbine engine at simulated altitude operating conditions. The PSL test facility has the capability to create a continuous cloud of ice crystals that are ingested by the engine during operation at simulated altitudes. The PSL tests successfully duplicated the icing events that were experienced by this engine during flight through ice crystal clouds. During testing at the PSL, after the ice cloud was turned on, key engine performance parameters responded immediately due to ingestion of the ice crystals. The points where the performance deteriorated with time have been attributed to ice accretion in the low pressure compressor. Eight data points were analyzed in order to gain understanding of key transient engine performance parameters. Examination of the test data showed two distinct responses in the engine once the ice cloud was initiated.
2015-06-15
Technical Paper
2015-01-2139
E.J. Grift, E. Norde, E. Van der Weide, H.W.M. Hoeijmakers
In this study the characteristics of ice crystals on their trajectory in a single stage of a turbofan engine compressor will be determined. The particle trajectories are calculated with a Lagrangian method employing a classical fourth-order Runge-Kutta time integration scheme. The air flow field is provided as input and is a steady flow field solution governed by the Euler equations. The single compressor stage is represented using a cascaded grid. The grid consists of three parts of which the first and the last part are stator parts and the centre part is a rotor. This grid is linearly cascaded, i.e. repeated infinitely above and below the shown grid, to represent the other blades of this stator-rotor-stator stage. The rotor movement is accomplished by prescribing a relative velocity of the rotor part relative to the stator parts and the interface between rotor and stator is modelled by using a mixing plane assumption allowing a steady-state analysis.
2015-06-15
Technical Paper
2015-01-2143
Christian Mendig
In the project SuLaDI (Super Large Droplet Icing) research about the icing of airfoils through super large and super cooled droplets is done at the Institute of Composite Structures and Adaptive Systems (German Aerospace Center) and at the institute of Adaptronics and Function Integration (Technische Universität Braunschweig). In the framework of the project a deicing facility was built. It consists of a cooling chamber and a wind tunnel of the Eiffel-type therein. The icing of specimen takes place in the test chamber of the wind tunnel at temperatures below 0 °C. Between the flow straightener and the contraction section a spray system is built in, which sprays water droplets into the wind tunnel. The droplets are accelerated by the airstream and supercool on the way to the specimen. That means they cool down below the freezing point temperature, but they stay fluid. When hitting the specimen they freeze on it to rime ice, clear ice or mixed ice.
2015-06-15
Technical Paper
2015-01-2107
Tom Currie, Craig Davison, Dan Fuleki
There is significant recent evidence that ice crystals ingested by a jet engine at high altitude can partially melt and then accrete within the forward stages of the compressor, potentially producing a loss of performance, rollback, combustor flameout, compressor damage, etc. Several studies of this ice crystal icing (ICI) phenomenon have been conducted in the past 5 years using the RATFac (Research Altitude Test Facility) altitude chamber at the National Research Council of Canada (NRCC), which includes an icing wind tunnel capable at operating at Mach numbers (M), total pressures (po) and temperatures (To) pertinent to ICI. Humidity can also be controlled and ice particles are generated with a grinder. The ice particles are entrained in a jet of sub-freezing air blowing into the tunnel inlet. Warm air from the altitude cell also enters the tunnel, where it mixes with the cold ice-laden jet, increasing the wet-bulb temperature (Twb) and inducing particle melting.
2015-06-15
Technical Paper
2015-01-2119
Shinan Chang, Chao Wang, Mengyao Leng
Drop deformation and breakup is an important issue that involved in the aircraft and engine icing field especially in the case of the supercooled large droplets (SLD). In this paper, the breakup modes of SLD are discussed in detail based upon the classical theories of the drop breakup and typical icing conditions. It is found that the breakup modes of SLD are mainly vibration breakup, bag-type breakup, multimode breakup and shear breakup. As the vibration breakup mode is rare, focuses are put on the bag-type breakup, multimode breakup and shear breakup. Because the drop Weber number is increasing gradually when the drops are approaching the leading edge of the airfoil and the drop Weber number differs in different locations of the airfoil surface, two or three breakup modes may appear simultaneously in a given environmental condition.
2015-06-15
Technical Paper
2015-01-2118
Sergey Alekseyenko, Michael Sinapius, Martin Schulz, Oleksandr Prykhodko
In spite of wide theoretical and experimental studies of icing problem that have been held up to recent times, nevertheless, the most dangerous flights regimes as in the presence of supercooled large droplets or in supercooled rain remain studied not enough. Also the range of parameters that corresponds to the exploitation modes of aircrafts with relatively small heights and speeds of flight like airplanes of small aviation, helicopters, UAV etc. because of the complexity of the icing processes are still not covered. The aim of this work is to answer the next question: which an actual process of interaction of supercooled large water droplets with growing ice surface at small speeds of flight and which physics of falling moisture freezing process on the icing surface is. Thus, the work presents the results of experiments conducted in order to obtain the photographic data on how the interaction between the supercooled water droplets and the icing aerodynamic surface occurs.
2015-06-15
Technical Paper
2015-01-2146
Matthew Feulner, Shengfang Liao, Becky Rose, Xuejun Liu
Matt Feulner, Shengfang Liao, Becky Rose and Xuejun Liu Pratt & Whitney, United Technologies Corporation A through-flow based Monte Carlo particle trajectory simulation is used to calculate the ice crystal paths in the low pressure compressor of a high bypass ratio turbofan engine. The trajectory model includes a statistical ice particle breakup model due to impact on the engine surfaces. Stage-by-stage ice water content, particle size and particle velocity distributions are generated at multiple flight conditions and engine power conditions. The simulation results prompt the need to properly set up boundary conditions for component or cascade testing.
2015-06-15
Technical Paper
2015-01-2147
Sandra Turner, Jean-Marc Gaubert, Remy Gallois, Thibault Dacla, Ingrid Mullie, Aurelien Bourdon, Fabien Dezitter, Alice Grandin, Alain Protat, Rodney Potts, Alfons Schwarzenboeck, J. Walter Strapp
The PLANET (PLAne-NETwork) System was used for real-time satellite data transmission during the HAIC/HIWC Darwin field Campaign (January to March 2014). The basic system was initially providing aircraft tracking, chat and weather text messages (METAR, TAF, NOTAM, etc.) in a standalone application. In the frame of the HAIC (High Altitude Ice Crystals) project, many improvements were made in order to fulfill requirements of the on-board and ground science teams. The aim of this paper is to present the main improvements of the PLANET System that were implemented for the Darwin field campaign. The goal of the flight tests for high IWC characterization were to collect cloud data in deep convective clouds, provide 99th percentile total water content statistics and other relevant parameters of such clouds as a function of distance scale to industry and regulators.
2015-06-15
Technical Paper
2015-01-2155
Tadas P. Bartkus, Peter Struk, Jen-Ching Tsao
This paper describes a numerical model that simulates the thermal interaction between ice particles, water droplets, and the flowing air applicable during icing wind tunnel tests where there is significant phase-change of the cloud. The model is compared to measurements taken during wind tunnel tests simulating ice-crystal and mixed-phase icing that relate to ice accretions within turbofan engines. This model, written in MATLAB, is based on fundamental conservation laws and empirical correlations. Due to numerous power-loss events in aircraft engines, potential ice accretion within the engine due to the ingestion of ice crystals is being investigated. To better understand this phenomenon and determining the physical mechanism of engine ice accretion, fundamental tests have been collaboratively conducted by NASA Glenn Research Center and the National Research Council of Canada (NRC).
2015-06-15
Technical Paper
2015-01-2156
Michael Oliver
The National Aeronautics and Space Administration conducted a full scale ice crystal icing turbofan engine test in the NASA Glenn Research Center’s Propulsion Systems Laboratory (PSL) Facility in February 2013. Honeywell Engines supplied the test article, an obsolete, unmodified Lycoming ALF502-R5 turbofan engine serial number LF01 that experienced an uncommanded loss of thrust event while operating at certain high altitude ice crystal icing conditions. These known conditions were duplicated in PSL for this testing. The data generated during this testing contained three subsets: known event conditions, altitude scaling conditions and a design of experiment (DOE) data set. The key roll back indicating parameter was found to be the reduction of the measured load parameter, the average of two measured load cells mounted on the thrust stand.
2015-06-15
Technical Paper
2015-01-2115
Antonio Criscione, Suad Jakirlic, Zeljko Tukovic, Ilia Roisman, Cameron Tropea
Atmospheric icing occurs when supercooled large drops (SLD) of water come in contact with the surface of exposed structures. Excessive accumulation on structures and equipment is well known for causing serious problems in cold-climate regions which lead to material damage and high costs in various sectors of the economy. Hereby, SLD impact with the exposed structure results consequently in an ice layer growth covering the surface of the substrate. The present study enables, among other things, modeling of both stages of the solidification process of a supercooled large water drop on a cold substrate - the first rapid, recalescent stage and the second slower, quasi-isothermal stage. The different mechanisms underlying both freezing stages can be explained as follows: in the first stage the initial planar solidification front becomes morphologically unstable due to a high degree of supercooling. Small bumps/instabilities evolving at the interface propagate further into the liquid.
Viewing 31 to 60 of 16146

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