Ice Accretion Research Articles

On the conditions for self-catapulting of freezing water droplets

Despite the remarkable progress of anti-icing and deicing technologies in the past decades, it remains a grand challenge to dislodge freezing water from a solid surface without consuming external energy. Herein, we propose a strategy to dislodge freezing water from solid surfaces just by leveraging its volume expansion resulting from the phase change from water to ice. The implementation of this energy-saving strategy relies on a simple micropillar-based gadget on the surface, termed freezing-empowered droplet catapult (FEDC), whereby the work done by the volume expansion of a freezing droplet accreted on it can be harvested and stored as elastic energy, and subsequently released in due course to catapult the freezing droplet away from the surface. Mechanics-based modelling is carried out to reveal the necessary conditions of occurrence for the self-catapulting of freezing water droplets on an FEDC, yielding a phase map that manifests the necessary synergy among the characteristic dimensions and stiffness of the FEDC as well as the volume of the droplet in triggering its self-catapulting. Our study not only demonstrates the feasibility of an energy-saving strategy for shedding off freezing droplets from solid surfaces but also provides a quantitive guideline for the design of the gadget for implementation, paving the way to a new technology for controlling ice accretion on solid surfaces with zero consumption of external energy.

Towards optimizing power-supplying strategy of versatile composites for energy-efficient and robust anti-icing/deicing

Fiber-reinforced polymer-based composites have been used widely in engineering structural components but suffer from ice accretion issues. Assembling a straightforward electrothermal anti-icing/deicing system that combines passive superhydrophobic and photothermal effects to alleviate energy shortages is considered the most practical strategy. However, the instability of superhydrophobicity often causes compromising anti-icing performances. In addition, little is known about how to evaluate the effectiveness of these passive technologies and optimize active power supply strategies. In this study, a versatile fiber-reinforced polymer-based composite was fabricated by integral molding with superhydrophobic and electro/photothermal film. Based on the tailorability of surface temperature, a quantitative method was developed to evaluate the passive anti-icing technology. The superhydrophobic and photothermal effects were proven to reduce electrical energy consumption by 73.6%, which was further declined to 96% after optimizing the anti-icing/deicing power supply strategy. Additionally, the textures and porosity of the spraying substrate were highlighted to enhance the superhydrophobic durability. The fabricated robust and versatile fiber-reinforced polymer-based composite shows promise for use in controllable anti-icing/deicing of engineering components, such as unmanned aerial vehicles and wind turbine blades.

Reliability-based calibration of companion load combination factors by considering concurrent wind and ice loading for structural design

Transmission towers and overhead transmission lines are designed and constructed by considering the combined ice load and wind-on-ice load if the ice accretion hazard is not negligible. The structural design codes provide clauses with a range of values to evaluate such a combined load. However, it is unclear which of the values suggested in the codes one should use for specified regions, and the reliability-based calibration of such a combination is unavailable. To fill this gap, in the present study, we carried out the reliability-based calibration of the companion load combination factors by using statistics of the ice accretion thickness and concurrent wind speed available from more than 250 meteorological stations in Canada. For the calibration, a nonlinear combination problem needs to be considered since the wind-on-ice load depends on the accreted ice thickness, making this calibration task differ from those commonly reported in the literature, which is focused on the linear load combination problem. A parametric investigation was also carried out to assess the effect of using different return periods and the correlation between ice accretion and concurrent wind speed on the companion load combination factors. The calibration results were used to recommend the load combination format, the companion load combination factors, and the ratio of the square equivalent concurrent wind speed to the return period value of the annual maximum wind speed, which is commonly implemented in design codes.

Study on the Anti-Icing of Conical Rotating Spinners with Different Cone Angles

This paper presents an experimental study on the anti-icing performance of full-scale rotating spinners with different cone angles. The experiments were conducted in a 3 m×2 m ice wind tunnel (IWT), and the spinners were equipped with hot-air anti-icing systems. Three different cone angles (80°, 70°, and 60°) were examined. The surface temperature of the spinners was measured using an infrared (IR) camera, and ice accretion and water film flow were recorded using high-speed cameras. Numerical simulations were also performed to analyze the water collection coefficients and anti-icing heat energy. The results showed that a larger cone-angle spinner has a larger water collection coefficient but a smaller heat-transfer coefficient and total surface area, resulting in better anti-icing performance for the same conditions. Additionally, the results showed that the residual ice on the spinner exhibited small, white, discretely distributed icicles. Furthermore, the surface temperature in the icing region of the 60° spinner was found to be almost equal to the total temperature of the incoming flow, indicating rime-ice accretion even under glaze-ice conditions. This observation can be attributed to the low water collection coefficient in this region.

Ice Shape Convergence in Multistep Ice Accretion Simulations

Local errors in the geometrical description of the ice front are amplified in multistep simulations over conformal meshes due to the coupling of aerodynamics, water impingement, ice accretion, and grid deformation. Small perturbations in the initial phase of ice formation possibly result in dramatically different ice shapes, which can hinder the stability of the multistep procedure. This problem is analyzed by investigating the combined effects of space and time discretization on the ice growth over airfoils and three-dimensional wings. We propose an automatic procedure for selecting the time interval for the update of the aerodynamics and particle impingement. A local growth limiter λ is introduced here to bound the local ice thickness growth to be comparable to the local grid spacing on the surface, resulting in an automatic adaptive time step to be used in the multistep simulation. Examples are provided for three-dimensional cases under both rime and glaze conditions over straight and swept wings. These examples highlight the different accretion mechanisms of the two ice regimes and preliminarily indicate that ice-shape convergence can be achieved for low values of λ.

Towards a Model of Snow Accretion for Autonomous Vehicles

Snow accumulation on surfaces exposed to adverse weather conditions has been studied over the years due to a variety of problems observed in different industry sectors, such as aeronautics and wind and civil engineering. With the growing interest in autonomous vehicles (AVs), this concern extends to advanced driver-assistance systems (ADAS). Weather stressors, such as snow and icing, negatively influence the sensor functionality of AVs, and their autonomy is not guaranteed by manufacturers during episodes of intense weather precipitation. As a basis for mitigating the negative effects caused by heavy snowfall, models need to be developed to predict snow accumulation over critical surfaces of AVs. The present work proposes a framework for the study of snow accumulation on road vehicles. Existing icing and snow accretion models are reviewed, and adaptations for automotive applications are discussed. Based on the new capabilities developed by the Weather on Wheels (WoW) program at Ontario Tech University, a model architecture is proposed in order to progress toward adequate snow accretion predictions for autonomous vehicle operating conditions, and preliminary results are presented.

An Ice Protection System Based on Phased Piezoelectric Transducers

This study focuses on a system constituted of two piezoelectric transducers installed on a slat representative element, with ice protection purposes. The waves generated by these actuators can cause, in fact, shear actions between the slat panel and the ice accretion, with the final effect of breaking and detaching it. A property of the system is, however, the possibility of regulating the phase between the excitation signals of the two transducers. This capability can be exploited to produce local advantageous wave interference with a consequent amplification of the shear actions. Benefits can be obtained in terms of: (1) reduction of needed power; (2) recovery of signal intensity losses due to distance, geometric, and mechanic discontinuities; (3) recovery of non-optimal functionality due to off-design conditions. The work starts with an overview of the impact of the ice on the aeronautic and other sectors. Then, attention is paid to the systems currently used to protect aircraft, with a specific focus on ultrasounds generated by piezoelectric transducers. The concept proposed in this work is then presented, illustrating the main components and the working modality. On this basis and considering the specific nature of the physical phenomenon, the modeling approach was defined and implemented. At first, the impact of some critical parameters, such as the temperature and the thickness of the ice, was investigated. Then, the impact of the phase delay parameter was considered, estimating the increase of magnitude potentially reachable by means of optimal tuning. Finally, a preliminary experimental campaign was organized and a comparison with the numerical predictions was performed.

Synthetic aperture radar backscatter is influenced by bubbles at the ice/water interface of an Antarctic lake

Synthetic aperture radar is an invaluable tool for monitoring lake ice. This study utilizes synthetic aperture radar to analyze the 2019-2023 backscatter time series of perennially ice-covered Lake Untersee in East Antarctica. We observed stark seasonal backscatter variations, averaging –9.6 dB from December to March and –3.7 dB from May to November. These fluctuations correspond to the abundance of sub-centimeter bubbles at the ice/water interface. Notably, the backscatter increase in April-May aligns closely with variations in ice thickness across the lake. Our findings suggest that ice cover thickness influences the timing and duration of ice accretion at the bottom, the accumulation of dissolved gases and bubbles, and the resultant changes in surface roughness at the ice/water interface. These factors collectively impact the backscatter response. This study enhances our understanding of the interactions between subsurface processes and synthetic aperture radar backscatter, shedding light on the seasonal dynamics of perennially ice-covered lakes.

Polymer coating for antiicing and deicing

Ice accretion may cause serious safety risk and huge economic loss for outdoor facilities. Herein, we report a waterborne polymeric coating based on a copolymer network of methacrylic acid (MAA), acrylamide (AM), N-2-hydroxyethyl acrylamide (HEAA), and methoxypolyethylene glycol (MPEG) with free polyethylene glycol (PEG) dispersed in it. Owing to the good compatibility of free PEG chains and the PEG side chains of the copolymer, the hydrogen bonding between acrylic copolymer and PEG, the free PEG chains can well be trapped in the network with some segments out of the mesh as short PEG chains are grafted on the coating surface, so that the surface has liquid-like properties. Water droplets can readily slip off on the coating surface with a small sliding angle (<30°). Particularly, the surface can hold the properties for a long duration upon water flushing, cycle of wetting-drying, and salt spraying tests. The polymer coating can find application in icing prevention and removal.

Surrogate modelling for ice accretion prediction on wind turbine blades based on support vector regression

AbstractIce accretion poses a significant challenge, threatening the safety and operational stability of wind turbines in extreme cold weather. Accurate estimation of ice accretion is essential in minimizing this concern. Data‐driven techniques typically rely on extensive historical datasets, and simulation‐based methods may be time‐consuming. To address these challenges, surrogate modelling for ice accretion prediction is proposed, utilizing support vector regression. This surrogate model undergoes rigorous evaluation to ensure reliability. The surrogate model reduces time consumption by four orders of magnitude compared to simulation, with only a 2.5% decrease in accuracy. The analysis reveals that real‐time pitch angle adjustments, informed by both the surrogate model and meteorological data, can effectively reduce ice accretion on wind turbine blades in cold climates.

Reducing Ice Adhesion to Polyelectrolyte Surfaces by Counterion-Mediated Nonfrozen Hydration Water.

Hydrophilic anti-icing coatings can be energy-effective passive solutions for combating ice accretion and reducing ice adhesion. However, their underlying mechanisms of action remain inferential and are ill-defined from a molecular perspective. Here, we systematically investigate the influence of the counterion identity on the shear ice adhesion strength to cationic polymer coatings having quaternary alkyl ammonium moieties as chargeable groups. Temperature-dependent molecular information on the hydrated polymer films is obtained using total internal reflection (TIR) Raman spectroscopy, complemented with differential scanning calorimetry (DSC) and ellipsometry. Ice adhesion measurements show a pronounced counterion-specific behavior with a sharp increase in adhesion at temperatures that depend on the anion identity, following the order Cl- < F- < SCN- < Br- < I-. Linked to the freezing of hydration water, the specific ordering results from differences in ion pairing and the amount of water present within the polymer film. Moreover, similar effects can be promoted by varying the cross-linking density in the coating while keeping the anion identity fixed. These findings shed new light on low ice adhesion mechanisms and may inspire novel approaches for improved anti-icing coatings.

On the Fidelity of RANS-Based Turbulence Models in Modeling the Laminar Separation Bubble and Ice-Induced Separation Bubble at Low Reynolds Numbers on Unmanned Aerial Vehicle Airfoil

The operational regime of Unmanned Aerial Vehicles (UAVs) is distinguished by the dominance of laminar flow and the flow field is characterized by the appearance of Laminar Separation Bubbles (LSBs). Ice accretion on the leading side of the airfoil leads to the formation of an Ice-induced Separation Bubble (ISB). These separation bubbles have a considerable influence on the pressure, heat flux, and shear stress distribution on the surface of airfoils and can affect the prediction of aerodynamic coefficients. Therefore, it is necessary to capture these separation bubbles in the numerical simulations. Previous studies have shown that these bubbles can be modeled successfully using the Large Eddy Simulation (LES) and Direct Numerical Simulation (DNS) but are computationally costly. Also, for numerical modeling of ice accretion, the flow field needs to be recomputed at specific intervals, thus making LES and DNS unsuitable for ice accretion simulations. Thus, it is necessary to come up with a Reynolds-Averaged Navier–Stokes (RANS) equation-based model that can predict the LSBs and ISBs as accurately as possible. Numerical studies were performed to assess the fidelity of various RANS turbulence models in predicting LSBs and ISBs. The findings are compared with the experimental and LES data available in the literature. The structure of these bubbles is only studied from a pressure coefficient perspective, so an attempt is made in these studies to explain it using the skin friction coefficient distribution. The results indicate the importance of the use of transition-based models when dealing with low-Reynolds-number applications that involve LSB. ISB can be predicted by conventional RANS models but are subjected to high levels of uncertainty. Possible recommendations were made with respect to turbulence models when dealing with flows involving LSBs and ISBs, especially for ice accretion simulations.

A Dual-Mode Surface Acoustic Wave Delay Line for the Detection of Ice on 64°-Rotated Y-Cut Lithium Niobate.

Ice accumulation on infrastructure poses severe safety risks and economic losses, necessitating effective detection and monitoring solutions. This study introduces a novel approach employing surface acoustic wave (SAW) sensors, known for their small size, wireless operation, energy self-sufficiency, and retrofit capability. Utilizing a SAW dual-mode delay line device on a 64°-rotated Y-cut lithium niobate substrate, we demonstrate a solution for combined ice detection and temperature measurement. In addition to the shear-horizontal polarized leaky SAW, our findings reveal an electrically excitable Rayleigh-type wave in the X+90° direction on the same cut. Experimental results in a temperature chamber confirm capability for reliable differentiation between liquid water and ice loading and simultaneous temperature measurements. This research presents a promising advancement in addressing safety concerns and economic losses associated with ice accretion.

Ice accretion simulation incorporating roughness effects and separation correction through a transition model

In the simulations of ice accretion, accurately modeling the impact of surface roughness and calculating the separated flow are crucial aspects. A modified laminar–turbulent transition model that incorporates both separation and roughness-induced transition correction is employed for icing simulations. An iced airfoil was selected to validate the modified model's predictive capability for large separation, and a rough airfoil was utilized to assess the modified model's capability in simulating roughness effects. Icing simulations under different conditions are conducted for an airfoil. The results indicate that roughness induces an earlier laminar–turbulent transition, thereby influencing the heat transfer coefficients. The effects of separation and roughness correction on rime icing simulation are minimal, but they are significant for glaze icing simulation, resulting in more accurate predictions of maximum ice thickness and ice horn orientation. The simulated glaze ice causes more pronounced separation and more substantial reductions in lift compared to simulated rime ice. The modified model can accurately predict the separation bubble and reduce the prediction error of lift over 60%.

Regional features of glaze ice events frequency in the north of the European territory of Russia in the current changing climate

Recently, the interest in society in observing and forecasting dangerous meteorological phenomena in the cold period of the year has noticeably grown. In this work, we study the phenomenon of glaze ice in the north of the European territory of Russia in the North-Western Federal District. Here glaze ice (icing) is less frequent than other forms of ice accretion, but its characteristics most often exceed the criteria of dangerous meteorological phenomena. It is a great danger for various areas of the economy, ship navigation, causing an increase in traumatism of the population and damage to infrastructure. In accordance with the aim of the work, the spatial and temporal variability of the frequency of glaze ice accretion on the territory of the North-Western Federal District in the period 1986–2022 is investigated. The results are obtained on the basis of instrumental observations of meteorological stations. Using statistical analysis, the features of mean yearly frequency at each meteorological station were studied. To assess the direction of annual changes in the glaze ice frequency, the linear trend coefficient was calculated for each meteorological station. The least squares method was used for this purpose. It is shown that the maximum number of days with glaze ice occurs in the central part of the North-Western Federal District. This can be attributed to the more frequent movement of Atlantic and southern cyclones to high latitudes and their precipitation, especially at the atmospheric fronts and in the warm sectors of the cyclones, at air temperatures near zero and below. What makes the spatial distribution of glaze ice frequency even more uneven is the presence of uplands in the European territory of Russia. More precipitation falls on their windward slopes, and the temperature decreases with altitude. The findings show that in recent decades there has been an increase in the frequency of the glaze ice phenomenon in the region. At the same time, the interannual variability remains relatively constant. Taking into account the positive trend in the number of glaze ice events and increasing air temperature and precipitation, it is necessary to develop measures to deal with this hazardous phenomenon and minimize damage from it.

Noncontact estimation of the onset of ice accretion in turbofan stators

AbstractThe problem of crystal ice formation inside aircraft turbine engines is well‐documented, and poses a significant risk to safety. The problem is not only one of power loss in flight, but the very real possibility that a flame‐out event could occur due to ice accretion on compressor stators, with potentially catastrophic outcomes. Although many instrumentation systems have been developed for wing ice detection, incipient formation of crystal ice is somewhat more difficult to detect. This is compounded by the need for a noncontact sensor which is robust to in‐flight conditions. This paper proposes an approach to the detection of ice formation based on microwave transmission characteristics across the first and possibly the second stage of the compressor stator. It is shown that noncontact detection is feasible under realistic conditions. The contribution of this paper is twofold. First, the microwave transmission approach is motivated using wind tunnel measurements, and appropriate frequency bands are determined. Next, a signal processing approach involving higher‐order analysis of time‐frequency distribution characteristics is then put forward. Experimental results are presented to support the hypothesis that multiband detection offers a workable approach to the incipient crystal‐ice detection problem.

Multi-Scale Superhydrophobic Surface with Excellent Stability and Solar-Thermal Performance for Highly Efficient Anti-Icing and Deicing.

Ice accretion can significantly impact the efficiency and safety of outdoor equipment. Solar-thermal superhydrophobic surface is an effective strategy for anti-icing and deicing. However, droplets easily turn to the Wenzel state during the icing and melting cycle processes, significantly increasing the adhesion and making the droplets difficult to remove from the surface. In this work, a triple-scale solar-thermal superhydrophobic surface is prepared on stainless steel 304 by etching, in situ oxidation, and spin-coating TiN nanoparticles for highly efficient deicing and anti-icing. The multi-scale structure enabled the droplets to recover the Cassie state completely after melting. The contact angle decreased from 162.5° to 136.7° during the icing process and gradually increased to 162.1° during the melting process. In addition, metal oxides and TiN nanoparticles enabled the superhydrophobic surface to exhibit a high solar absorptivity ( = 0.925). The synergistic effect of the superhydrophobicity and the solar-thermal performance endowed the designed multi-scale surface with excellent anti-icing and deicing performance. This work contributed to the practical development of anti-icing and deicing applications based on solar-thermal superhydrophobic surfaces.

Numerical simulation of rime ice accretion on airfoil using rigid sphere model

A 2D/3D numerical model for rime ice shape prediction is developed by combining the rigid sphere model (RSM) and computational fluid dynamics (CFD), and its characteristics are investigated. In the RSM, the ice accretion is modeled based on first principles with little physical modeling. The ice particle on an airfoil is described as a rigid sphere, and the ice shape is represented as a collection of rigid spheres. We use a non-body-fitted hierarchical Cartesian grid-based CFD solver so that complex ice shape represented by RSM can be handled. The tree data of the hierarchical Cartesian grid is also used for fast search of droplet positions. In addition, multiple ice particles are modeled as one large particle to reduce the number of trajectory calculations. The sensitivity of several parameters in the calculation is studied in 2D. Subsequently, 3D ice accretion analysis on NACA0012 airfoil using the RSM is performed for the first time. The simulation results are compared with those of the wind-tunnel experiments conducted at NASA. Although the RSM is a simple ice accretion model, reliable results are obtained in both 2D and 3D calculations.

Numerical Icing Simulations of Cylindrical Geometry and Comparisons to Flight Test Results

There is growing interest in government and industry to use numerical simulations for the Certification by Analysis of aircraft ice protection systems as a cheaper and more sustainable alternative to wind-tunnel and flight testing. The ice accretion on a cylindrical test article mounted under the wing of the National Research Council of Canada’s Convair-580 research aircraft during a flight test in Appendix O icing conditions was simulated using Ansys FENSAP-ICE™. A multishot simulation with input parameters averaged over the full icing period led to an increased level of liquid catch and ice accretion (by mass), and a broader ice profile when compared to a simulation with shot-averaged input parameters. An additional simulation using Ansys’ proprietary “extended icing data with vapor solution” method for calculating heat fluxes at the icing surface resulted in a broader ice profile in comparison to the classical technique, which produced a similar amount of accretion by mass. No combination of simulation settings, input parameters, and multishot methods tested in this study generated the same level of surface detail observed during flight testing, however, the amount of ice accretion, general location of ice features, and formation processes were in good agreement with the experimental results.

Ice accretion characteristics on rotating aeroengine fan blades

An experimental study was conducted to characterize the dynamic ice accretion process on rotating aero-engine fan blades to evaluate the icing-induced detrimental effects on the fan rotor performance. A scaled spinner-fan model was installed in an Icing Research Tunnel and exposed to typical rime and glaze icing conditions. It was found that, while ice structures accreted on both the suction and pressure surfaces of the fan blades, more ice accumulated in the region near the blade roots than those near the blade tips. The ice structures accreted on the fan blades not only deteriorated the shapes of the deliberately designed blades greatly but also blocked the airflow passages through the fan rotor substantially, regardless of the icing type. More specifically, the thickness of the fan blades was found to increase up to 40 % after undergoing 480 s of the rime icing experiment, the airflow passages were blocked by up to 14 % due to the rime ice accretion near the blade roots, resulting in about 70 % reduction of the air pressure increment across the fan rotor. Due to the combined effects of the aerodynamic shear forces and centrifugal forces associated with the rotating motion, substantial water runback was observed over the rotating blade surfaces under the glaze icing condition, resulting in the rapid growth of more complex “needle-like” icicles along the blade leading edges. Glaze ice accretion was found to cause more serious and faster performance degradation to the fan rotor than the rime icing scenario. While the airflow passages between the neighbouring blades were blocked by up to 18 % after undergoing 120 s of the glaze icing experiment, the airflow was found to be depressurized, instead of pressurized, after passing the iced fan rotor.