A review of level ice and brash ice growth models

Brash ice forms in harbours and ship channels from frequent ship passages and the resulting freezing–breaking cycles create a unique ice formation. The brash ice accumulation over the winter season is a result of meteorological, thermodynamical and mechanical processes. A reliable brash ice growth model is an important asset when determining navigation routes through ice conditions and when establishing port ice management solutions. This review aims to describe the brash ice development and its modelling as well as the key parameters that influence the brash ice growth and its estimation. This paper summarises the brash ice growth models and the fundamental theories of level ice growth upon which these models are based, and outlines the main knowledge gaps. The results highlight the importance of porosity and piece size distribution and their effect on the consolidation process. The inclusion of the brash ice lateral movement and the side ridge formation would improve the accuracy of forecast models. Furthermore, the findings of the study identify the effect of omitting meteorological parameters such as snow and radiation, from the brash ice growth models. Their contribution to the level ice thickness suggests a significant influence on the brash ice consolidation process.

Icing Mitigation by MEMS-Fabricated Surface Dielectric Barrier Discharge

Avoiding ice accumulation on aerodynamic components is of enormous importance to flight safety. Novel approaches utilizing surface dielectric barrier discharges (SDBDs) are expected to be more efficient and effective than conventional solutions for preventing ice accretion on aerodynamic components. In this work, the realization of SDBDs based on thin-film substrates by means of micro-electro-mechanical-systems (MEMS) technology is presented. The anti-icing performance of the MEMS SDBDs is presented and compared to SDBDs manufactured by printed circuit board (PCB) technology. It was observed that the 35m thick electrodes of the PCB SDBDs favor surface icing with an initial accumulation of supercooled water droplets at the electrode impact edges. This effect was not observed for 0.3m thick MEMS-fabricated electrodes indicating a clear advantage for MEMS-technology SDBDs for anti-icing applications. Titanium was identified as the most suitable material for MEMS electrodes. In addition, an optimization of the MEMS-SDBDs with respect to the dielectric materials as well as SDBD design is discussed.

Study on Icing Environment Judgment Based on Radar Data

As a major threat to aviation flight safety, it is particularly important to make accurate judgments and forecasts of the ice accumulation environment. Radar is widely used in civil aviation and meteorology, and has the advantages of high timeliness and resolution. In this paper, a variety of machine learning methods are used to establish the relationship between radar data and icing index (Ic) to determine the ice accumulation environment. The research shows the following. (1) A linear model was established, based on the scattering rate factor (Zh), radial velocity (v), spectral width (w), velocity standard deviation (σ) detected by 94 GHz millimeter wave radar, and backward attenuation coefficient (β) detected by 905 nm lidar, so linear regression was carried out. After principal component analysis (PCA), the correction determination coefficient of the linear equation was increased from 0.7127 to 0.7240. (2) Ice accumulation was unlikely for samples that were significantly off-center. By clustering the data into three or four categories, the proportion of icing lattice points could be increased from 18.81% to 33.03%. If the clustering number was further increased, the ice accumulation ratio will not be further increased, and the increased classification is reflected in the classification of pairs of noises and the possibility of omission is also increased. (3) Considering the classification and nonlinear factors of ice accumulation risk, the neural network method was used to judge the ice accumulation environment. Two kinds of neural network structures were established for quantitative calculation: Structure 1 first distinguished whether there was ice accumulation, and further calculated the icing index for the points where there was ice accumulation; Structure 2 directly calculated the temperature and relative humidity, and calculated the icing index according to definition. The accuracy of the above two structures could reach nearly 60%, but the quantitative judgment of the ice accumulation index was not ideal. The reasons for this dissatisfaction may be the small number of variables and samples, the interval between time and space, the difference in instrument detection principle, and the representativeness of the ice accumulation index. Further research can be improved from the above four points. This study can provide a theoretical basis for the diagnosis and analysis of the aircraft ice accumulation environment.

A Superhydrophobic/Electrothermal/Photothermal Synergistically Anti-icing Strategy with Excellent Self-healable and Anti-abrasion Property

Unexpected ice accumulation tends to cause many problems or even disasters in our daily life. Based on the superior electrothermal and photothermal function of the carbon nanotubes, we introduced a superhydrophobic/electrothermal/photothermal synergistically anti-icing strategy. When a voltage of 15 V was applied to the superhydrophobic sample, the surface could rapidly melt the ice layer (~ 3 mm thickness) within 530 s at the environmental temperature of − 25 °C. When the near-infrared light (808 nm) irradiates on the superhydrophobic sample, the ice could be rapidly removed after 460 s. It was found that the superhydrophobicity helps the melted water to roll off immediately, and then solves the re-freeze problem the traditional surfaces facing. Moreover, the ice can be completely melted with 120 s when the superhydrophobic/electrothermal/photothermal synergistically anti-icing strategy was utilized. To improve the mechanical robustness for practical application, both nanoscale carbon nanotubes and microscale carbon powders were utilized to construct hierarchical structure. Then these dual-scale fillers were sprinkled onto the semi-cured elastomer substrate to prepare partially embedded structure. Both hierarchical structure and partially embedded structure were obtained after completely curing the substrate, which imparts excellent abrasion resistance (12.50 kPa, 16.00 m) to the prepared sample. Moreover, self-healable poly(urea–urethane) elastomer was introduced as the substrate. Thus, the cutted superhydrophobic sample can be mended by simply contacting at room temperature.

A Wind Tunnel Experimental Study of Icing on NACA0012 Aircraft Airfoil with Silicon Compounds Modified Polyurethane Coatings

Ice formation on the aerodynamic surfaces of an aircraft is regarded as a major problem in the aerospace industry. Ice accumulation may damage parts, sensors and controllers and alter the aerodynamics of the airplane, leading to a range of undesired consequences, including flight delays, emergency landings, damaged parts and increased energy consumption. There are various approaches to reducing ice accretion, one of them being the application of icephobic coatings. In this work, commercially available polyurethane-based coatings were modified and deposited on NACA 0012 aircraft airfoils. A hybrid modification of polyurethane (PUR) topcoats was adopted by the addition of nanosilica and three-functional spherosilicates (a variety of silsesqioxane compound), which owe their unique properties to the presence of three different groups. The ice accretion on the manufactured nanocomposites was determined in an icing wind tunnel. The tests were performed under three different icing conditions: glaze ice, rime ice and mixed ice. Furthermore, the surface topography and wetting behavior (static contact angle and contact angle hysteresis) were investigated. It was found that the anti-icing properties of polyurethane nanocomposite coatings strongly depend on the icing conditions under which they are tested. Moreover, the addition of nanosilica and spherosilicates enabled the reduction of accreted ice by 65% in comparison to the neat topcoat.

Fabrication of Photothermal Film for Deicing Process Based on Gold Nano-Aggregate Encapsulated Yolk-Shell Structure

Ice accumulation on vessels, airplanes, or on the off-shore plants surfaces causes major accidents and difficulties in operation. Therefore, highly efficient and environmentally friendly materials for use as deicing surfaces are in continuous demand. Accordingly, photothermal materials have gained enormous attention owing to their outstanding performance in the removal of ice. Herein, a gold nano-aggregate yolk-shell structure (GNA-YS) was introduced as a deicing material. GNA-YS was homogeneously dispersed in photocurable polyurethane acrylate and used to fabricate a highly efficient and sunlight-responsive GNA-YS film. Upon irradiation with an 810 nm light-emitting diode (LED) (135 mW cm−2), the temperature of the GNA-YS film increased by approximately 70 °C within 2 min, which rapidly (within 6 min) melted the accumulated ice. Moreover, the GNA-YS film exhibited a temperature increase of 15 °C in a refrigerator under LED illumination for 1 min. Additionally excellent stability was confirmed through repeated experiments. The newly developed deicing GNA-YS film has prospective applicability in vessels or airplanes.

Performance Deterioration of Pitot Tubes Caused by In-Flight Ice Accretion: A Numerical Investigation

In-flight ice accretion on typical pitot-static systems is numerically investigated to reveal their performance deterioration under both rime and glaze icing. Coupled with the open source computational fluid dynamics (CFD) platform, OpenFOAM, the numerical strategy integrates the airflow determination by the Reynolds-averaged Navier-Stokes equations, droplet collection evaluation by Eulerian representation, and ice accumulation by mass and energy conservation. Under varying inflow conditions and wall temperatures, the calculated ice accretion performance indicates that the ambient temperature has the most significant effect on the icing-induced failure time, leading to an almost exponential growth. Meanwhile, the blocking time is found to be linearly proportional to the increase in wall temperature. With the increase in inflow velocity, the failure time follows a parabolic variation with glaze ice accretion while shows a monotonic reduction under rime icing conditions. In addition, when the angle of attack increases, failure accelerates under both the glaze and rime icing scenarios. These findings provide guidance for the protection design of pitot tubes. A nonlinear regression analysis is further conducted to estimate the failure performance. The predicated failure times show reliable consistency with numerical results, demonstrating the capability of the obtained empirical functions for convenient predictions of failure times within the applicable range.

Experimental Study of Water Transfer and Ice Accumulation in Freezing Soils under Different Conditions

A series of tests for water transfer and ice accumulation were conducted under different soil types and conditions of water supply method, temperature gradient, and initial water content; the influence of the above parameters on the efficiency of water and vapor transfer was investigated and discussed. The main conclusions drawn are as follows. First, due to the difference in permeability for different soil type, water (i.e., liquid water and vapor) transfers differently. The water (or ice) accumulated in the soils of calcareous sand, silty soil in Lanzhou (SSL), red clay in Changsha, and silty soil in Hohhot (SSH) under the top plate is 34.5%, 21.0%, 11.33%, and 26.7%, respectively. In addition, the water (or ice) accumulation is determined by the holding capacity of water. Second, the supply method of liquid water is more efficiently compared with that of vapor supply, with the water contents increasing to 60.5% and 57.3% for liquid water and vapor supply. Third, the larger the temperature gradient, the greater the water accumulation in the frozen area. The increased amount of water mass under different temperature boundary conditions is 227.9 g, 253.3 g, and 273.8 g, respectively. Finally, the initial water content in silty soil has a significant influence on water and vapor transfer. The increased amounts of water for the tests of the initial water content of 5%, 10%, and 15% are 282.6 g, 253.3 g, and 132.5 g, respectively. The smaller the initial water content, the greater the water transfer in the unfrozen zone and vapor transfer in the frozen zone.