Ice Shape Research Articles

Sea ice and atmospheric circulation shape the high-latitude lapse rate feedback

Arctic amplification of anthropogenic climate change is widely attributed to the sea-ice albedo feedback, with its attendant increase in absorbed solar radiation, and to the effect of the vertical structure of atmospheric warming on Earth’s outgoing longwave radiation. The latter lapse rate feedback is subject, at high latitudes, to a myriad of local and remote influences whose relative contributions remain unquantified. The distinct controls on the high-latitude lapse rate feedback are here partitioned into “upper” and “lower” contributions originating above and below a characteristic climatological isentropic surface that separates the high-latitude lower troposphere from the rest of the atmosphere. This decomposition clarifies how the positive high-latitude lapse rate feedback over polar oceans arises primarily as an atmospheric response to local sea ice loss and is reduced in subpolar latitudes by an increase in poleward atmospheric energy transport. The separation of the locally driven component of the high-latitude lapse rate feedback further reveals how it and the sea-ice albedo feedback together dominate Arctic amplification as a coupled mechanism operating across the seasonal cycle.

Effect of pH on the activity of ice-binding protein from Marinomonas primoryensis.

The ability of an ice-binding protein (IBP) from Marinomonas primoryensis (MpIBP) to influence ice crystal growth and structure in nonphysiological pH environments was investigated in this work. The ability for MpIBP to retain ice interactivity under stressed environmental conditions was determined via (1) a modified splat assay to determine ice recrystallization inhibition (IRI) of polycrystalline ice and (2) nanoliter osmometry to evaluate the ability of MpIBP to dynamically shape the morphology of a single ice crystal. Circular dichroism (CD) was used to relate the IRI and DIS activity of MpIBP to secondary structure. The results illustrate that MpIBP secondary structure was stable between pH 6 and pH 10. It was found that MpIBP did not interact with ice at pH ≤ 4 or pH ≥ 13. At 6 ≤ pH ≥ 12 MpIBP exhibited a reduction in grain size of ice crystals as compared to control solutions and demonstrated dynamic ice shaping at 6 ≤ pH ≥ 10. The results substantiate that MpIBP retains some secondary structure and function in non-neutral pH environments; thereby, enabling its potential utility in nonphysiological materials science and engineering applications.

Experimental Investigation on Glaze Ice Accretion and Its Influence on Aerodynamic Characteristics of Pipeline Suspension Bridges

Pipeline suspension bridges may experience ice accretion under special atmospheric conditions, and the aerodynamic characteristics of the bridges may be modified by the ice accretion. Under some specific climatic conditions of freezing rain, the dependencies of the ice size and shape on the icing duration and some structural properties (including pipeline diameter, inclination angle of wind hanger, inclination angle and size of section steel, and girder geometry) were experimentally investigated in a refrigerated precipitation icing laboratory. Typical ice accretions on pipelines, wind hangers, section steels, and girders of pipeline suspension bridges are summarized. Then the effects of some selected ice accretions on aerodynamic force coefficients of a bridge girder were further investigated through wind tunnel tests. The ice size and shape on the pipeline were closely related to the pipeline diameter and icing duration. The engineering geometric models of ice accretion on pipelines were extracted. The ice shape and size on wind hangers and section steels changed with their inclination angles. The aerodynamic force coefficients of a girder with ice accretion were much higher than those of an ice-free one. The results can provide references for simulating the ice accretion and further evaluating the effect of ice accretion on the aerodynamics of pipeline suspension bridges.

Acoustic Characterization of Glaze and Rime Ice Structures on an Oscillating Airfoil via Fully Unsteady Simulations

The development of low-cost and simple technologies to improve pilot awareness of icing environments is crucial to improve the safety of rotorcraft, and especially those with limited icing clearance which are admittedly operating within icing environments without full icing clearance. An acoustic characterization of glaze and rime ice structures is hereby introduced to begin to quantify different ice shape noise signatures which directly transcend from the iced performance characteristics to develop acoustic ice detection technologies. The feasibility of the detection technique is assessed for fully unsteady simulations of ice accretion on an oscillating, two-dimensional airfoil. This work focuses on the computational modeling of the experimental database of a rotor airfoil with pitching motion during icing conditions from the NASA Glenn Icing Research Wind Tunnel and computing the resultant noise signals and analyzing their topology.

Galloping Stability and Aerodynamic Characteristic of Iced Transmission Line Based on 3-DOF

A new calculation method of critical wind speed based on three degrees of freedom (3-DOF) is proposed for galloping problem of iced transmission line. Based on the quasistatic theory, the aerodynamic load of iced transmission line is obtained, which considers the influence of transverse and torsional motion on the relative wind angle of attack. Finally, the equivalent galloping model of 3-DOF iced transmission line is established. At the initial angle of attack, the aerodynamic load is expanded by Taylor, and the unsymmetrical linear aerodynamic coefficient matrix is obtained. The Routh–Hurwitz criterion is used to judge the stability of iced transmission line system, and then the critical wind speed is calculated. The in-plane and out-plane frequencies corresponding to the first-order mode of the transmission line are solved by the analytical method and numerical simulation method. The results obtained by the two methods are compared and verified. The influence of dimensionless transmission line parameterλon the in-plane and out-of-plane frequencies is discussed. The aerodynamic coefficients of the iced transmission line are measured by wind tunnel test and the aerodynamic characteristics are analyzed. According to the theoretical formula, the critical wind speed is calculated by MATLAB. The critical wind speed determined in this paper is compared with the critical wind speed determined by Den Hartog and Nigol theory. The influences of torsional vibration frequency, ice thickness, and ice shape on critical wind speed are analyzed. The research results of this paper have important theoretical significance for the stability judgment of iced transmission lines.

Aerodynamic force coefficients of an ice-accreted bridge cable in low and moderately turbulent wind

This study deals with the effects of wind turbulence on the mean aerodynamic drag, lift and moment coefficients of a stationary ice-accreted section model of a bridge cable for different wind angles of attack. The experiments were conducted in the Reynolds number range between 2.5·104 and 1.36·105. While the yawed/inclined cable model was experimentally iced in a climatic wind tunnel, the development of the ice shape was registered using photogrammetry. Later on, the ice-accreted model was reproduced on a smaller scale via three-dimensional printing. For the model in cross-flow, a series of wind tunnel tests were performed in low and moderately turbulent flow conditions with turbulence intensities of 3% and 12%, respectively. The obtained results were compared with those obtained experimentally for a circular smooth cylinder. The principal finding is that the flow turbulence significantly reduces the drag coefficient.

Effect of an elastic surface on snow and ice accumulation on vehicles

The ice on vehicles has increased the requirements of vehicular mobility, safety, and comfort, which attracts people's attention increasingly. Through analyzing the characteristics of snow and ice accumulation on vehicle mudguard, we found that the snow and ice gradually encircled the wheel, the front and rear mudguards, and the posterior side of the fender inner panel with the vehicle traveling, and its thickness decreased from bottom to top. Moreover, the splash and the initial shape of ice and snow were different on the front and rear wheels. Surprisingly, we found that the increase in wheel speed delayed the accumulation of snow and ice in general. Specifically, the rate of accumulation gradually decreased on the middle of mudguards and fender inner panels but increased the on their sides. Besides, because of elastic coatings reducing the freezing adhesive strength of a material, to reduce the negative effects of snow and ice accumulation, we proposed an anti-icing elastic surface on mudguards. The results of laboratory and field test show that the icing was delayed and more gradual after the mudguard had been completely coated with the elastic coating. This suggests that changing the surface elasticity of the mudguard could be used on anti-icing for vehicle chassis.

Numerical Simulation of the Anti-Icing Performance of Electric Heaters for Icing on the NACA 0012 Airfoil

Ice accretion is a phenomenon whereby super-cooled water droplets impinge and accrete on wall surfaces. It is well known that the icing may cause severe accidents via the deformation of airfoil shape and the shedding of the growing adhered ice. To prevent ice accretion, electro-thermal heaters have recently been implemented as a de- and anti-icing device for aircraft wings. In this study, an icing simulation method for a two-dimensional airfoil with a heating surface was developed by modifying the extended Messinger model. The main modification is the computation of heat transfer from the airfoil wall and the run-back water temperature achieved by the heater. A numerical simulation is conducted based on an Euler–Lagrange method: a flow field around the airfoil is computed by an Eulerian method and droplet trajectories are computed by a Lagrangian method. The wall temperature distribution was validated by experiment. The results of the numerical and practical experiments were in reasonable agreement. The ice shape and aerodynamic performance of a NACA 0012 airfoil with a heater on the leading-edge surface were computed. The heating area changed from 1% to 10% of the chord length with a four-degree angle of attack. The simulation results reveal that the lift coefficient varies significantly with the heating area: when the heating area was 1.0% of the chord length, the lift coefficient was improved by up to 15%, owing to the flow separation instigated by the ice edge; increasing the heating area, the lift coefficient deteriorated, because the suction peak on the suction surface was attenuated by the ice formed. When the heating area exceeded 4.0% of the chord length, the lift coefficient recovered by up to 4%, because the large ice near the heater vanished. In contrast, the drag coefficient gradually decreased as the heating area increased. The present simulation method using the modified extended Messinger model is more suitable for de-icing simulations of both rime and glaze ice conditions, because it reproduces the thin ice layer formed behind the heater due to the runback phenomenon.

Experimental Study on the Effect of Different Parameters on Rotor Blade Icing in a Cold Chamber

Icing phenomenon is an important problem in helicopter rotor design. Conducting experiments in a cold chamber is one of the main methods used to study the law of rotor icing. The purpose of this paper was to analyze the influence of different parameters on the ice shapes of rotor blade and to obtain the relationship between the ice shapes and the input parameters. The icing experimental platform of rotation blade in a cold chamber was set up, and the rotor icing experiments under various conditions were carried out. The ice shapes on the blade were obtained, and the influence of different icing temperatures, rotation speeds, liquid water content, icing times, number of blades on the rotor, and blade materials on the ice shapes were analyzed. The results showed that the ice thickness on the leading edge increased with the increase of liquid water content, rotation speed, and icing time, and the number and material of blades had little effect on icing. The conclusions of this paper can provide a reference for the rotor numerical simulation and future experimental research.

Effects of blunt trailing-edge optimization on aerodynamic characteristics of NREL phase VI wind turbine blade under rime ice conditions

To reduce the adverse effects of the ice on aerodynamic characteristics, a new NREL Phase VI wind turbine blade which is suitable to rime ice environments is developed through the blunt trailing-edge optimization. The parametric control equations of blunt trailing-edge airfoil are established by adopting the airfoil profile integration theory and B-spline curve, and the curve fitting of the airfoil’s rime ice from LEWICE software is carried out using the linear interpolation algorithm with equidistant and equiangular step lengths. The S809 airfoil under rime ice conditions is optimized to maximize the lift coefficient by the particle swarm optimization (PSO) coupled with GAMBIT and FLUENT, and a NREL Phase VI blade is formed with the optimized airfoil S809-BT (with BT the blunt trailing-edge). The blade’s rime ice is obtained through using the polynomial fitting to deal with projection point coordinates of airfoils’ ice shapes in lagging and flapping surfaces, and the pressure coefficient, flow characteristics, torque and output power of icy sharp and blunt trailing-edge blades are investigated. The results indicate that in rime ice conditions, compared with those of sharp trailing-edge blade, the pressure difference and vortex size of blunt trailing-edge blade become larger, and the torque and output power increase by 4.36 %, 1.55 % and 2.88 % at v= 7 m/s, 15 m/s and 20 m/s, respectively. The research provides significant guidance for improving the aerodynamic performance of wind turbine blade considering the icing effects.

Proposal of Novel Icing Simulation Using a Hybrid Grid- and Particle-Based Method

ABSTRACTIcing on aircraft can drastically reduce aerodynamic performance and lead to serious accidents. Therefore, prediction of the accreted ice shape and area and its effects on aerodynamic performance is crucial during the design phase of an aircraft. However, numerical simulations based on conventional grid-based methods such as the finite volume method cannot accurately reproduce the complex ice shapes, which involve horn growth, feather growth, air voids, and severe surface roughness. In the present study, instead of the grid-based method, a hybrid grid- and particle-based method was newly proposed and applied to the icing problem on a NACA0012 airfoil. The explicit moving particle semi-implicit method was employed as the particle-based method due to its short computing time. The numerical simulations effectively reproduced feather-shaped ice, air voids, and surface roughness. Finally, by computing the flow around the iced airfoil, it was confirmed that flow separation around the leading edge occurred due to the ice layer, which resulted in a thicker boundary layer and wake and an increase in the drag coefficient of approximately 70% after a residence time of only 60 seconds.

Correction of Local Collection Efficiency Based on Roughness Element Concept for Glaze Ice Simulation

ABSTRACTIn glaze ice conditions, beads on the surface usually grow to form roughness elements through coalescence, finally resulting in enhancement of local collection efficiency. However, the effects of roughness elements due to freezing of beads are not reflected on the local collection efficiency in CFD icing simulations. This is problematic for predicting the resultant ice shape, which may lead to inaccurate aerodynamic performance and load distribution. The aim of this study is to propose a macroscopic icing model which can reflect bead microscopic phenomena using the Eulerian approach. To this end, a correction was made for collection efficiency by introducing a novel parameter - the effective impinging angle- which is the angle to calculate the local collection efficiency depending on the physical state of surface. It is assumed that the parameter related to the contact angle represents the state of beads. The computational icing analysis of airfoil was performed using the proposed model both in the rime condition and glaze conditions. The results show that the icing characteristics in the feather region is captured with enhanced accuracy in both conditions.

Ice crystal characterization in cirrus clouds II: radiometric characterization of HaloCam for the quantitative analysis of halo displays

Abstract. We present a procedure for geometric, spectral, and absolute radiometric characterization of the weather-proof RGB camera HaloCamRAW and demonstrate its application in a case study. This characterization procedure can be generalized to other RGB camera systems with similar field of view. HaloCamRAW is part of the automated halo observation system HaloCam and designed for the quantitative analysis of halo displays. The geometric calibration was performed using a chessboard pattern to estimate camera matrix and distortion coefficients. For the radiometric characterization of HaloCamRAW, the dark signal and vignetting effect were determined to correct the measured signal. Furthermore, the spectral response of the RGB sensor and the linearity of its radiometric response were characterized. The absolute radiometric response was estimated by cross calibrating HaloCamRAW against the completely characterized spectrometer of the Munich Aerosol Cloud Scanner (specMACS). For a typical measurement signal the relative (absolute) radiometric uncertainty amounts to 2.8 % (5.0 %), 2.4 % (5.8 %), and 3.3 % (11.8 %) for the red, green, and blue channel, respectively. The absolute radiometric uncertainty estimate is larger mainly due to the inhomogeneity of the scene used for cross calibration and the absolute radiometric uncertainty of specMACS. Geometric and radiometric characterization of HaloCamRAW were applied to a scene with a 22∘ halo observed on 21 April 2016. The observed radiance distribution and 22∘ halo ratio compared well with radiative transfer simulations assuming a range of ice crystal habits and surface roughness values. This application demonstrates the potential of developing a retrieval method for ice crystal properties, such as ice crystal size, shape, and surface roughness using calibrated HaloCamRAW observations together with radiative transfer simulations.

Effect of Characteristic Phenomena and Temperature on Super-Cooled Large Droplet Icing on NACA0012 Airfoil and Axial Fan Blade

Icing simulations involving super-cooled large droplets (SLDs) on a NACA0012 airfoil and a commercial axial fan were performed considering the characteristic behavior of SLD icing (i.e., splash-bounce, deformation, and breakup). The simulations were performed considering weak coupling between flow field and droplet motion. The flow field was computed using the Eulerian method, wherein the droplet motion was simulated via the Lagrangian method. To represent the ice shape, an extended Messinger model was used for thermodynamic computation. The ice shape and collection efficiency of the NACA0012 airfoil derived using the icing simulation exhibited a reasonable agreement with the existing experimental data. The icing simulation results for the axial fan, in terms of distribution of ice on the blade and its influence on the flow field, indicated that flow separation occurred, and the mass flow rate of the flow passage decreased. Moreover, the splash and bounce phenomena considerably influenced the icing process; however, the effect of the deformation and breakup phenomena was negligibly small. In terms of the effect of the SLDs on the icing phenomena, it was noted that, with the decrease in the SLD temperature (from −5 °C to −15 °C), the number of adhering SLDs increased, whereas the number of splashing and bouncing SLDs decreased.

CFD 및 강체 동역학을 이용한 항공기의 결빙 궤적 예측

Ice shedding refers to the phenomenon that ice forms on the surface of an aircraft operating in icing conditions and then moves with the flow after break-up from the surface by aerodynamic forces. Collisions of shed ice fragments with aircraft components such as engine intake or control surface can cause serious threat to the safety of aircraft. The separated ice fragments show unpredictable and complex characteristics in their shape, size, orientation, formation position, and rotational speed. This study deals with the prediction of the trajectories of ice fragments using computational simulation methods. The trajectories of ice fragments of a fixed wing aircraft were calculated by the CFD code based on the overset grid method and the formulation of six degree of freedom. The method was first validated for the flat plate motion using the wind tunnel test results. Finally, the aerodynamic characteristics and trajectories of separated ices were investigated for various ice shapes and conditions.

Icing detection and evaluation of the electro-impulse de-icing system based on infrared images processing

The aircraft icing poses a significant hazard to aircraft safety and it is important to remove the ice in time. The electro-impulse de-icing (EIDI) system is a mechanical de-icing method, which prevents ice accumulation on that part of the aircraft where ice is more likely to form. Since its discovery research on the theory and application of the EIDI system continued to progress. In this paper, the formation of ice is detected using infrared thermography of the heat signal generated on the aircraft skin surface. Ice accretion specimen are produced to explore the effects of seven critical parameters. The performance of the EIDI system is evaluated using the infrared thermal wave test. The infrared thermography sequence of the ice accretion specimen is acquired by the infrared camera during de-icing operation. The ice detection of the EIDI system employs a method that achieves the original icing detection and icing damage detection based on infrared image processing, including principal component analysis (PCA) and Canny edge detection. The measurement of the original icing on center and radius is achieved by the three-point method, which may be further employed to evaluate the icing manufacturing error. An icing damage detection method is also designed and applied. An index based on the infrared thermal image processing results is introduced to evaluate the performance of the EIDI system under different experimental conditions. The quantitative behaviour of de-icing performance in terms of seven important parameters involved in manufacturing the ice has been verified and discussed. The results show that PCA and Canny edge detection may be effectively exploited to implement ice shape detection and, in turn, to improve the design of the EIDI system.

Interplay of unsteady aerodynamics and flight dynamics of transport aircraft in icing conditions

Airframe icing causes significant degradation of aerodynamic characteristics and influences the flight safety. Wind tunnel study of longitudinal steady and unsteady aerodynamic characteristics of a transport aircraft in icing conditions is carried out in order to develop mathematical model of aerodynamics in the extended flight envelope. The wind tunnel results are validated through flight tests conducted for the real aircraft. Large, glaze-horn ice shapes, corresponding to holding flight phase, are considered. Influence of an ice protection system as well as its failure is examined. Effect of icing on the unsteady aerodynamics characteristics is studied not only through wind tunnel tests but also via analysis of subsequent influence on the flight dynamics of the aircraft. The conducted study shows that the ice shapes of the holding phase lead to reduced stall angle of attack (AoA), maximum lift, and longitudinal damping. Flight dynamics analysis demonstrates that dangerous aircraft behaviour in the form of high AoA departure and limit cycle oscillations (LCO) can be observed at smaller elevator deflections for the iced aircraft. The account for icing influence on the unsteady aerodynamics in the flight dynamics simulations revealed degradation of the dynamic response and deterioration of phase portraits of the system. Even for small AoA and elevator deflection, the aircraft might be trapped into the basin of attraction of high-AoA LCO. In addition, incorporating icing effects in unsteady aerodynamics manifest larger amplitude of LCO.

Detailed atmospheric ice accretion surface measurement using micro‐computed tomography

AbstractSurfaces exposed to atmospheric cold temperature and humid environments are prone to ice accretion. Airplanes, electrical power transmission cables, and wind turbines are typical examples for which icing has to be considered. The measurement of the resulting ice shapes is a challenging process. While macroscopic characteristics of the ice geometry can be observed using photography and optical scanning techniques, microscopic measurements are difficult to conduct because grooved surface partially occludes the geometry of chasms. To overcome this optical inaccessibility, we propose a method to carry out detailed high‐resolution measurements of the accretion surface with micro‐computed tomography. This approach provides a unique visualization of the empty spaces in the feather region. The information obtained by this technique can improve the understanding of ice accretion physics and its computational modeling.

Aerodynamic Prediction of Iced Airfoils Based on Modified Three-Equation Turbulence Model

Ice formation on a wing poses a threat to aircraft safety because it changes the effective shape of the wing and considerably deteriorates the aerodynamic performance. The performance prediction of an iced airfoil requires an accurate turbulence model. In this Paper, a three-equation turbulence model for the Reynolds-averaged Navier–Stokes equation is developed to determine the stall behavior of iced airfoils. The model is implemented using a linear eddy viscosity transition model as a baseline and is modified to appropriately simulate complex flow phenomena such as laminar separation, shear layer transition, and turbulent reattachment. The model also takes the nonequilibrium characteristics of turbulence into account. Different airfoils, including clean airfoils and three types of iced airfoils (horn ice, streamwise ice, and spanwise-ridge ice), are numerically tested. The results indicate that the present model demonstrates engineering accuracy in terms of the stall behavior prediction and can be adapted in a wide range of ice shapes. The relative errors of the predicted maximum lift coefficients of the iced airfoils are about 5% of the experimental values.

Inhibiting Freeze-Thaw Damage in Cement Paste and Concrete by Mimicking Nature’s Antifreeze

Since the 1930s, surfactant-based air-entraining admixtures (AEAs) have been used to mitigate freeze-thaw damage in cementitious materials. While effective, entrained air voids weaken concrete and increase its permeability, thereby increasing susceptibility to multiple other forms of in situ degradation. Inspired by nature, we report that a soluble biomimetic antifreeze polymer that displays ice recrystallization inhibition (IRI) and dynamic ice shaping (DIS) activities can prevent damage from ice crystal growth in cement paste and concrete. We first report that polyethylene glycol-graft-polyvinyl alcohol (PEG-PVA) mimics the explicit IRI and DIS activity of native ice-binding proteins in high-pH media characteristic of concrete pore solution. Second, we report that addition of PEG-PVA to cement paste and concrete prevents freeze-thaw damage without entraining air. Taken together, the findings demonstrate an alternative mechanistic approach to AEAs that can be leveraged to prevent damage from ice crystal growth in cementitious materials.