Ice Accretion Process Research Articles

An experimental study on the dynamic ice accretion processes on bridge cables with different surface modifications

An experimental study was conducted to investigate the dynamic ice accretion processes on bridge cables with different surface modifications (i.e., 1. Standard plain, 2. Pattern-indented surface, and 3. Helical fillets). An Icing Research Tunnel available at Iowa State University (i.e., ISU-IRT) was used to generate two typical icing conditions (i.e., dry rime icing vs. wet glaze icing). During the experiments, while a high-speed imaging system was used to capture the transient behaviors of surface water transport and dynamic ice accretion processes over the surfaces of the cable models, a high-accuracy force measurement system was utilized to quantify the dynamic aerodynamic loadings acting on the cable models under different icing conditions. It was found that the addition of surface features (i.e., pattern-indented surface and helical fillets) could dramatically influence the dynamic ice accretion process and the final topology of the ice structures accreted on the cable surfaces. While the ice accretion on the standard plain cable and the cable with helical fillets was found to reduce the drag forces by about 25%, the ice accretion on the pattern-indented cable model would induce about 30% greater aerodynamic drag force acting on the cable model.

Study of ice accretion and icing effects on aerodynamic characteristics of DU96 wind turbine blade profile

In order to optimize the large wind turbines operation in ice prone cold regions, it is important to better understand the ice accretion physics and its effects on aerodynamic performance and power production losses. This paper describes a case study of ice accretion on DU96-W-180 airfoil, which has been used for large wind turbine blades such as NREL 5 MW. Analysis has been carried out for glaze and rime ice conditions using icing tunnel experimental data and multiphase Computational Fluid Dynamics (CFD) based numerical approach. Results show a difference in profile surface roughness and heat fluxes during rime and glaze ice accretion process, which leads to a significant change in rate and shape of ice accretion. More complex ice shapes are observed in case of glaze ice conditions that affects the aerodynamic performance differently from rime ice conditions. Numerical results are compared with the experimental data, where a good agreement is found. Results show higher aerodynamic performance degradation for glaze ice conditions particularly at higher angles of attack.

An experimental investigation of dynamic ice accretion process on a wind turbine airfoil model considering various icing conditions

In the present study, the dynamic ice accretion process over a typical wind turbine airfoil model (i.e., DU96-W-180 airfoil) was experimentally investigated under various icing conditions. The experimental study was conducted in the Icing Research Tunnel of Iowa State University (i.e., ISU-IRT). Different icing conditions (i.e., rime, mixed and glaze) that wind turbine may experience in winter were reproduced by manipulating the airflow temperature, velocity, and liquid water content (LWC) in ISU-IRT. While a high-speed imaging system was used to reveal the dynamic ice accretion process over the surface of the test model, an infrared (IR) thermal imaging system was used to map the corresponding temperature distributions over the ice accreting airfoil surface. Time variations of the ice thickness accreted along the leading edge (LE) of the test model were extracted based on the acquired high-resolution images of the ice accretion process under different test conditions. It was found that, due to the obvious runback of the impacted water (i.e., formation of water film and rivulets) over the airfoil surface, the growth rate of the ice layer accreted along the airfoil leading edge was much slower under the glaze icing condition, in comparison with those under the rime and mixed icing conditions. Such surface water transport behavior was also found to expand the ice influencing region. From the temperature evolutions during the dynamic icing processes, the transient processes of droplet impingement, water film/rivulets formation, and ice roughness growth were temporally resolved, providing comprehensive details of the unsteady heat transfer during the dynamic icing process. While the surface temperature increment due to the direct droplet impingement was found to decrease monotonously along the chord in rime case, a stream-wise ‘plateau’ region was observed in the glaze and mixed icing cases due to the complex multiphase mass/heat transfer associated with the surface water transport behaviors.

Droplet distribution spectrum effects on dry ice growth on cylinders

A detailed parametric analytical study along with a series of viscid multiphase numerical simulations of ice accretion were performed in comparison with experimental data of ice accretion on a 30 mm diameter cylinder. The study was performed for droplet distribution spectra, Langmuir (A-J), in addition to an experimental droplet distribution obtained in an icing tunnel. Analysis shows that droplet distribution spectrum has a pronounced effect on cloud impingement parameters, such as droplet overall collision efficiency (E), droplet local collision efficiency (β0), droplet maximum impingement angle (θ), droplet impact velocity (V0), accreted ice mass and density. The values of these parameters can significantly change at the same operating conditions and median volume diameter (MVD) with a change of droplet distribution spectrum. These differences are more pronounced at low values of droplet inertia parameter, (K). Further experimental, analytical and numerical investigations into those aspects at lower values of droplet inertia parameter are deemed necessary in order to expand the understanding of different cloud impingement parameters on the ice accretion process and performance of current icing theory in cases with low values of K. For the low values of K, which correspond to the values of E ≤ 0.10, the use of the full droplet spectrum is recommended in calculations instead of monodispersed. In addition, based on the results of this and previous works the Langmuir D distribution is recommended as standard or “first guess” distribution.

Three-Dimensional Modelling and Simulation of the Ice Accretion Process on Aircraft Wings

© 2018 Chang S, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Effects of thermal conductivity of airframe substrate on the dynamic ice accretion process pertinent to UAS inflight icing phenomena

An experimental investigation was conducted to quantify the dynamic ice accretion and the unsteady heat transfer process over the ice accreting surfaces of composite-based airframes widely used for light-weight, Unmanned-Aerial-Systems (UAS), in comparison to those over the surfaces of metal-based airframes used by conventional manned aircraft, in order to elucidate the underlying icing physics specifically pertinent to UAS inflight icing phenomena. Two airfoil/wing models with the same airfoil shape, but made of different materials (i.e., thermoplastic material with the thermal conductivity being only ∼0.2 W/m⋅K to represent typical UAS airframe substrates vs. Aluminum with the thermal conductivity being ∼200 W/m⋅K widely used for conventional manned aircraft). The two test models were mounted side-by-side inside an Icing Research Tunnel available at Iowa State University (i.e., ISU-IRT) under the same wet glaze or dry rime icing condition. During the icing experiment, while a high-speed imaging system was used to record the dynamic ice accretion process over the surfaces of the test models, an infrared thermal imaging system was also used to map the corresponding surface temperature distributions over the ice accreting airfoil surfaces. It was found that, upon the impacting of the airborne, super-cooled water droplets in ISU-IRT, ice would start to accrete rapidly on the surfaces of the test models with a significant amount of the latent heat of fusion being released associated with the phase changing of the impacted super-cooled water mass over the airfoil surfaces. The thermal conductivity of the airframe substrate was found to affect the dynamic ice accretion and unsteady heat transfer processes over the ice accreting surfaces significantly. With the two test models being exposed under the same icing conditions, the released latent heat of fusion was found to be dissipated much slower over the surface of the thermoplastic model, due to the much lower thermal conductivity of the thermoplastic substrate. In comparison with those on the surface of the Aluminum model, the slower dissipation of the released latent heat of fusion on the surface of the thermoplastic model was found to cause higher surface temperatures and greater “heated” regions near the airfoil leading edge, more obvious surface water runback over the airfoil surface, and formation of more complex rivulet-shaped ice structures at further downstream locations beyond the direct impinging zone of the super-cooled water droplets.

An experimental study on the aerodynamic performance degradation of a UAS propeller model induced by ice accretion process

An experimental study was performed to investigate the effects of ice accretion on the aerodynamic performances and wake characteristics of a propeller model used for Unmanned-Aerial-System (UAS) under different icing conditions (i.e., rime vs. glaze). The experimental study was conducted in the unique Icing Research Tunnel available at Iowa State University (ISU-IRT). In addition to acquiring the important features of ice accretion on the rotating propeller blade using a “phase-locked” imaging technique, the wake characteristics of the rotating UAS propeller under the different icing conditions were also resolved by using the Particle Imaging Velocimetry (PIV) technique along with the time-resolved measurements of aerodynamic forces and power consumption of the UAS propeller model. Both “free-run” and “phase-locked” PIV measurements were performed on the propeller model at the different stages of the icing experiments (i.e., before, during and after the dynamic icing processes) to provide both the instantaneous flow characteristics and the ensemble-averaged flow statistics (e.g., mean velocity, vorticity, and turbulence kinetic energy) in the wake of the rotating propeller model. To the best knowledge of the authors, this is the first work of its kind to provide detailed, temporally-resolved wake flow field measurements of UAS propeller under real icing conditions. It is found that while the rime ice accretion could closely follow the original profiles of the propeller blades, the glaze ice usually forms into very irregular structures that can significantly disturb the wake flow field of the rotating propeller model, generating the much larger and more complex vortices. Such complex large-scale vortices are found to enhance the turbulent mixing in the propeller wake and produce an evident velocity deficit channel around the outer board of the propeller blades, providing direct evidences in elucidating the dramatic decrease in thrust generation and the significant increase in power consumption of the rotating propeller model in icing conditions. The findings derived from this study are believed to be essential and very helpful to elucidate the underlying mechanisms of the aerodynamic performance degradation of ice accreting UAS propellers.

Landing Performance Prediction of Commuter Aircraft Due to Wings Ice Accretion on High Terrain Operation

Ice accretion on a wing is one of the aviation accident factors because it will interrupt the flow over an airfoil that will reduce its performance. The effect of wings leading edge ice accretion on the landing distance of commuter class aircraft in remote high terrain operation was obtained with the help of LEWICE code for ice shape predictions and XFLR5 for airfoil polar data prediction. The ice accretion process occurred within various icing atmospheric conditions based on Icing Design Envelopes 14 CFR part 25.1419, Appendix C. Two category of ice accretion, horn ice and streamwise ice, were obtained on the leading edge of the wing. The performance degradation caused by the ice accretion will increase aircraft landing speed that it will affect the landing distance.

An experimental study on the aerodynamic performance degradation of a wind turbine blade model induced by ice accretion process

Abstract An experimental study was conducted to characterize aerodynamic performance degradation of wind turbine blades induced by dynamic ice accretion process. The experimental study was performed in an Icing Research Tunnel with a turbine blade model under a typical glaze icing condition. Ice structures were found to accrete rapidly over both the upper and lower surfaces of the blade model after starting the ice accretion experiment. Irregular-shaped ice structures were found to disturb the airflow around the blade model greatly, resulting in large-scale flow separations and shedding of unsteady vortex structures from the ice accreting surface. The aerodynamic performance of the blade model was found to degrade significantly. The performance degradation induced by the ice accretion was found to be a strong function of the angle of attack of the blade model with more significant degradations at lower angles of attack. For the test case at the angle of attack of 5.0°, while the lift decreases to only ∼12% of its original value after 600 s of the ice accretion experiment, the drag was found to increase 4.5 times correspondingly. The detailed flow field measurements were correlated with the aerodynamic force data to elucidate the underlying physics.

Experimental study on the accretion and release of ice in aviation jet fuel

Ice formations in aircraft fuel systems pose a serious safety threat with potentially disastrous consequences, when restricting the fuel flow towards the engines. This is an ongoing challenge in the aerospace industry. In this work experimental studies have been performed to investigate the effects of temperature, flow rate and surface properties on the accretion and release of ice in flowing fuel. A test rig with a glass-windowed pipe has been employed to quantitatively measure the transient icing process under controlled conditions. The accreted ice exhibited soft and fluffy characteristics and was most likely the result of impinging solid ice particles that were entrained in the fuel flow. The ice particles were most sticky in a temperature range between −6°C and −20°C. The thickness of accreted ice decreased with roughness on aluminium surfaces and there was a significant reduction on polytetrafluoroethylene (PTFE) and polymethyl methacrylate (PMMA) in comparison to aluminium, copper or stainless steel surfaces. Comparison of the thickness of accreted ice with the ice adhesion strength reported in the literature showed a clear correlation. The experimental results will help to gain better understanding of the ice accretion process in flowing fuel and may serve as basis for design guidelines to minimize ice formation within an aircraft fuel system.

Experimental study of an anti-icing method over an airfoil based on pulsed dielectric barrier discharge plasma

Aircraft icing has long been a plague to aviation for its serious threat to flight safety. Even though lots of methods for anti-icing have been in use or studied for quite a long time, new methods are still in great demand for both civil and military aircraft. The current study in this paper uses widely used Dielectric Barrier Discharge (DBD) plasma actuation to anti-ice on a NACA0012 airfoil model with a chord length of 53.5 cm in a closed-circuit icing wind tunnel. An actuator was installed at the leading edge of the airfoil model, and actuated by a pulsed low-temperature plasma power source. The actuator has two types of layout, a striped electrode layout and a meshy electrode layout. The ice accretion process or anti-icing process was recorded by a CCD camera and an infrared camera. Instantaneous pictures and infrared contours show that both types of DBD plasma actuators have the ability for anti-ice under a freestream velocity of 90 m/s, a static temperature of −7 °C, an Median Volume droplet Diameter (MVD) of 20 μm, and an Liquid Water Content (LWC) of 0.5 g/m3. The detected variations of temperatures with time at specific locations reveal that the temperatures oscillate for some time after spraying at first, and then tend to be nearly constant values. This shows that the key point of the anti-icing mechanism with DBD plasma actuation is to achieve a thermal equilibrium on the model surface. Besides, the power consumption in the anti-icing process was estimated in this paper by Lissajous figures measured by an oscilloscope, and it is lower than those of existing anti-icing methods. The experimental results presented in this paper indicate that the DBD plasma anti-icing method is a promising technique in the future.

A comparison study on the thermal effects in DBD plasma actuation and electrical heating for aircraft icing mitigation

A comparison study of a novel method of utilizing thermal effects induced by Dielectric-Barrier-Discharge (DBD) plasma actuation (i.e., DBD plasma-based method) and a conventional electrical heating method for aircraft icing mitigation was performed in an Icing Research Tunnel available at Iowa State University (i.e., ISU-IRT). A NACA0012 airfoil/wing model embedded with an AC-DBD plasma actuator and a conventional electrical film heater over the airfoil surface was tested under a typical aircraft icing condition. While a high-speed imaging system was used to record the dynamic ice accretion and transient surface water transport processes over the airfoil surface, an infrared (IR) thermal imaging system was also utilized to map the corresponding surface temperature distributions over the airfoil surface simultaneously to quantify the unsteady heat transfer and phase changing process over the ice accreting airfoil surface. It was found that, with the same power input, the DBD plasma-based method showed at least equivalent effectiveness, if not better, in preventing ice accretion over the airfoil surface, in comparison to the conventional electrical heating method. Further optimization of the DBD plasma-based method with a duty-cycle modulation was found to have a much better anti-/de-icing performance, in comparison to the conventional electrical heating method. The findings derived from the present study demonstrated the potential of a new class of anti-/de-icing strategy by leveraging the thermal effects induced by DBD plasma actuation for aircraft in-flight icing mitigation.

An experimental study on soft PDMS materials for aircraft icing mitigation

A series of experiments were conducted to characterize the anti-/de-icing performances of soft PDMS materials with different shear modulus and to explore their potentials for aircraft icing mitigation. In the present study, a new class of soft PDMS materials with adjustable shear modulus were fabricated by adding different amounts and different molecular weights of non-reactive trimethyl-terminated PDMS (t-PDMS) into the hydrosilylation mixture of vinyl-terminated PDMS (v-PDMS) and hydride-terminated PDMS (h-PDMS). While the soft PDMS materials were found to be hydrophobic with the contact angle of water droplets over the PDMS surfaces being about 110°, the ice adhesion strength over the soft PDMS materials was found to be extremely low (i.e., being less than 10 kPa at −5 °C or two orders of magnitude smaller), in comparison to those of the conventional rigid surface (i.e., being greater than 1000 kPa for Aluminum or the hard plastic material used to make the airfoil/wing model used in the present study). Upon the dynamic impacting of water droplets at relatively high weber number levels pertinent to aircraft inflight icing phenomena (e.g., We = 4000), the soft PDMS surfaces were found to deform dynamically due to the elastic nature of the PDMS materials, which cause the soft PDMS materials acting as “trampolines” to bounce off most of the impinged water mass away from the impacted surfaces. By applying the soft PDMS materials to coat/cover the surface of a NACA 0012 airfoil/wing model, an explorative study was also performed in an Icing Research Tunnel available at Iowa State University (i.e., ISU-IRT) to demonstrate the feasibility of using the soft PDMS materials to mitigate the impact ice accretion process pertinent to aircraft inflight icing phenomena.

Experimental Investigation on the Dynamic Icing Process over a Rotating Propeller Model

An experimental study was conducted to investigate the dynamic ice accretion process over the blade surfaces of a rotating propeller model for unmanned-aerial-system (UAS) applications. In addition to revealing the transient ice accretion process over the rotating propeller surfaces, the dynamic thrust force generated by the propeller model was also measured simultaneously along with the required power inputs to drive the propeller model. Because of the combined effects of aerodynamics forces and the centrifugal force associated with the rotation motion, the ice accretion process over the rotating propeller surfaces was found to become very complicated. The ice accretion over the rotating propeller surfaces was found to become more preferable along the radial direction with the formation of lobster-tail-like ice structures extruding out from the propeller blade surfaces. The aerodynamic performance of the propeller model was also found to degrade tremendously due to the ice accretion, causing a significant reduction (i.e., up to 70% reduction) in mean thrust generation and a dramatic increase in force fluctuation amplitude (i.e., up to 250% increase). Despite of different types of ice accretion, the propeller model was always found to consume more power operating under icing conditions (i.e., up to 250% more power consumption under glaze icing conditions).

An experimental investigation on the unsteady heat transfer process over an ice accreting airfoil surface

In the present study, an experimental investigation was performed in an Icing Research Tunnel available at Iowa State University (i.e., ISU-IRT) to quantify the unsteady heat transfer and dynamic ice accretion process over an airfoil/wing surface under different icing conditions (i.e., dry rime ice accretion vs. wet glaze ice accretion). A theoretic model was developed at first to evaluate the unsteady heat transfer process over the ice accreting airfoil/wing surface in the term of convective heat transfer coefficient. During the experiments, a high-speed infrared (IR) thermal imaging system was used to achieve temporally-resolved measurements of the surface temperature distribution over the ice accreting airfoil/wing surface. The transient behaviors of droplets impingement, surface water runback and dynamic phase changing processes over the airfoil/wing surface were characterized quantitatively based on the quantitative surface temperature measurements. Based on the time evolution of the measured surface temperature distributions over the airfoil/wing surface for the rime ice accretion case, the water collection efficiency distribution around the airfoil surface was determined quantitatively, which was then imported into the theoretic heat transfer model to estimate the convective heat transfer coefficients over the ice accreting airfoil/wing surface. The convective heat transfer coefficient was found to reach its maximum value at the airfoil stagnation point, and decrease gradually at the downstream locations. The formation of the ice roughness near the airfoil leading edge was found to be able to enhance the convective heat transfer process over the airfoil surface, which would further promote the ice formation and accretion over the roughed airfoil surface.

A modified spongy icing model considering the effect of droplets retention on the ice accretion process

Icing models have been widely used for the prediction of ice accretion process on an aircraft surface. This paper proposes a modified spongy icing model considering the influence of droplets retention on the ice accretion process. In theoretical derivation, the Euler-Lagrange method is employed to calculate the air flow field and droplets motion around the airfoil. The modified model combined with the preceding solutions is then applied to compute the critical size of the water film and droplets on the ice surface to finally obtain the ice accretion morphology. In numerical simulation, a NACA0012 airfoil is taken as an example for verification of the modified model via comparing the results with those based on other models as well as experiments. The results indicate that the modified model has a better agreement with the experiment on the ice accretion morphology distribution than the existing icing models when there is liquid water in ice at not much low air temperature, demonstrating the necessary consideration of droplets retention on the ice surface when numerically simulating glaze ice accretion. The modified spongy icing model would contribute to a better prediction of the ice accretion morphology distribution on an airfoil.

Utilization of Thermal Effect Induced by Plasma Generation for Aircraft Icing Mitigation

An explorative investigation was performed to demonstrate the feasibility of using a thermal effect induced by dielectric-barrier-discharge plasma generation for aircraft icing mitigation. The experimental study was performed in an icing research tunnel available at Iowa State University. A NACA 0012 airfoil/wing model embedded with dielectric-barrier-discharge plasma actuators was installed in the icing research tunnel under typical glaze-/rime-icing conditions pertinent to aircraft inflight icing phenomena. While a high-speed imaging system was used to record the dynamic ice-accretion process over the airfoil surface for the test cases with and without plasma generation, an infrared thermal imaging system was used to map the corresponding temperature distributions to quantify the unsteady heat transfer and phase changing process over the airfoil surface. For the typical glaze-ice condition, the thermal effect induced by dielectric-barrier-discharge plasma generation was demonstrated to be able to prevent ice accretion over the airfoil surface during the entire ice-accretion experiment. The measured quantitative surface temperature distributions were correlated with the acquired images of the dynamic ice-accretion and water runback processes to elucidate the underlying physics.

An experimental study of surface wettability effects on dynamic ice accretion process over an UAS propeller model

An experimental study was conducted to evaluate the effects of surface wettability on the dynamic ice accretion process over the surface of a rotating Unmanned-Aerial-System (UAS) propeller model and the resultant aerodynamic performance degradation due to the ice accretion. A propeller model was installed in an Icing Research Tunnel at Iowa State University (i.e., ISU-IRT) with its surface wettability changed significantly (i.e., hydrophilic surface versus superhydrophobic surface). In addition to acquiring “phase-locked” images to reveal the dynamic ice accretion process over the rotating propeller surface, the thrust generation and the required power input to drive the propeller model to operate at a constant rotation speed were also measured during the ice accretion process. The dynamic ice accretion process over the rotating propeller surface was found to vary remarkably with changes to the propeller surface wettability. By making the propeller surface superhydrophobic, the detrimental effects of the ice accretion on the aerodynamic performance of the propeller model were found to be mitigated greatly with much less ice accretion over the propeller surface, significant reduction of the thrust loss and less demand for extra power consumption due to the ice accretion, in comparison with the case with the propeller surface being hydrophilic.

Model for ice wet growth on composite insulator and its experimental validation

The indigenous and foreign scholars have conducted considerable research on the electrical characteristics of ice-covered insulators, but there is a lack of research on the growth process of ice accretion on insulators. On the basis of the heat and mass balance during icing, a complete wet-growth icing model, including the ice accretion on the insulator surface and the growth of icicles is established. In this model, the loss of water film on the insulator surface and the water supply for icicles are taken into account, and rebuild the icicle growing equations according to the water mass balance. The effect of flow-field change due to the growth of icicles is considered and analysed. The simulation results indicate that the growth of icicles and ice thickness are affected by climate parameters and the flow-field change. Low temperature and high wind speed can increase the growing rate of icicles and the ice thickness and decrease the time of icicle bridging. The change of flow field leads to changes in water mass balance and slows the progress of icing on the insulator surface. Through a series of icing tests on insulator FXBW-110/100, it is found that the experimental results are in good agreement with those obtained by the numerical simulation method.

Snow thickness estimation on first-year sea ice using microwave and optical remote sensing with melt modelling

The snow cover on first-year sea ice plays a paramount role in thermodynamics by modulating sea ice ablation and accretion processes. However, meteoric accumulation and redistribution of snow on first-year sea ice is highly stochastic over space and time, which makes it a poorly understood parameter. In this study, a region of late-winter snow thickness on first-year sea ice in the Canadian Arctic Archipelago is estimated using time series spaceborne C-band microwave scatterometer and optical MODIS data and a simple snow melt model. Results show good correspondence between the modeled snow thickness and remotely sensed dates of melt onset and pond onset. The mean snowmelt duration for 20 study sites is 24.6±1.2days, and the estimated mean snow thickness is 14.7±3.0cm. The overall performance of the model reveals a RMSE of 4.0cm and a mean bias of 0.3cm. The methodology shows promise; particularly because it can easily be scaled up in order to estimate snow thickness on seasonal sea ice on a regional basis.