Glaze Ice Conditions Research Articles

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).

Ice Accretion Effects on Helicopter Rotor Performance, via Multibody and CFD Approaches

A numerical approach for assessing the degraded aerodynamics and flight characteristics of ice-contaminated helicopter rotors is proposed. A hybrid two- and three-dimensional loose coupling strategy between multibody dynamics modeling and computational fluid dynamics icing is formulated that attempts to balance computational resources, model complexity, and accuracy for use during the early design phases. A quasi-3D formulation that considers the heat transfer and the motion of the water film due to centrifugal effects is introduced. The method is suited for the analysis of rime, glaze, and/or mixed ice conditions. Degraded aerodynamic and dynamic characteristics of the iced rotor and the changes in flight performance are assessed. The technique has been applied to the scenario of isolated helicopter rotors in hover and in forward flight. Deterioration of the figure of merit is also presented.

Electrical characteristics of an energised conductor under various weather conditions

When a transmission line is subjected to adverse weather conditions, rain drops or ice can be formed on its surface, leading to discharge phenomena known as corona. The corona discharge increases corona loss, leakage conductance, and capacitance, the latter two effects facilitating harmonic conditions and power quality degradation. This study investigates the electrical characteristics of an energised conductor under rain, rime, and glaze ice conditions. The experiments were carried out in a climate room using a corona cage. It was found that the leakage conductance of a corona-cage configuration was at its highest under glaze ice condition and at its lowest under rime condition for the same background surface electric field. With the presence of icicles, the change in capacitance under glaze ice accretion was complex. From the experimental results, it can be concluded that the corona-cage configuration is mainly characterised by its capacitive nature before the corona onset. When the corona discharge occurs, the corona cage exhibits a resistive–capacitive nature. With the increase of applied voltage, the configuration becomes more resistive.

Corona investigation of an energized conductor under various weather conditions

This paper deals with laboratory investigations of corona discharge from an energized conductor under various weather conditions. The adverse weather conditions which were considered in this study were rain, rime, and glaze ice. The experiments were carried out in a climate room using a corona cage. The experimental results showed that the corona loss was highest under glaze ice condition and lowest under rime icing. When the applied voltage was beyond corona onset voltage, the 3rd harmonic current was significant even if the 3rd harmonic voltage was low. The power factor can be negative at times depending on the energy transfer direction. It was found that corona loss is mainly contributed by the fundamental component and the contribution by the other harmonic components can be neglected. Moreover, it was found that the 3rd power factor can be used to determine whether the conductor is operating above its corona onset voltage.

Multi-Zone Ice Accretion and Roughness Models for Aircraft Icing Numerical Simulation

AbstractA mathematical multi-zone ice accretion model used in the numerical simulation of icing on airfoil surface based on three water states, namely, continuous film, rivulets and beads is studied in this paper. An improved multi-zone roughness model is proposed. According to the flow state of liquid water and film flow, rivulets flow governing equations are established to calculate film mass distribution, film velocity, rivulet wetness factor and rivulet mass distribution. Force equilibrium equations of droplet are used to establish the critical conditions of water film broken into rivulets and rivulets broken into beads. The temperature conduction inside the water layer and ice layer is considered. Using the proposed model ice accretion on a NACA0012 airfoil profile with a 4° angle of attack under different icing conditions is simulated. Different ice shapes like glaze ice, mixed ice and rime ice are obtained, and the results agree well with icing wind tunnel experiment data. It can be seen that, water films are formed on the surface, and heights of the films vary with icing time and locations. This results in spatially-temporally varying surface roughness and heat transfer process, ultimately affects the ice prediction. Model simulations indicate that the process of water film formation and evolution cannot be ignored, especially under glaze ice condition.

DC ice‐melting and temperature variation of optical fibre for ice‐covered overhead ground wire

To prevent atmospheric ice on optical fibre composite overhead ground wire (OPGW) from affecting the safe and stable operation of power system, applying the direct current (DC) ice-melting technology to remove ice from OPGW is a feasible option. If the selection of DC ice-melting current is unreasonable, the temperature of optical fibre can be extremely high which may shorten its operating life or even cause it to burn. Therefore, based on the finite element method, the ice-melting process of OPGW under glaze icing condition is simulated by COMSOL and MATLAB. The ice-melting time and temperature variations of optical fibre for ice-covered OPGW under different environmental conditions are obtained. Then, a series of ice-melting tests are carried out in an artificial climate chamber to verify the calculation results. Results show that the ice-melting and temperature increase of optical fibre gradually slow down during the entire DC ice-melting process. When ice sheds from the OPGW, the temperature of optical fibre reaches its maximum value. The ice-melting time is closely related to the ice-melting current, ambient temperature, wind speed, ice thickness and type of OPGW. The maximum temperature of optical fibre is significantly influenced by ice thickness and ice-melting current.

New Method for Direct Numerical Simulation of Three-Dimensional Ice Accretion

A simple and reasonable mathematical model is developed to simulate ice accretions on three-dimensional bodies directly. Based on the extended heat-transfer model proposed by Myers, this paper brings forward the concept of critical ice thickness as a criterion for the existence of overflow in every icing control volume. Besides, the concept of inner time step is proposed. After each inner time step, the ice-layer thickness and associated icing properties including the ice accretion rate and overflow in all icing control volumes will be updated to make the model more close to the physical reality. Then, the method for deciding the outflow through boundaries of each icing control volume is given based on the contravariant air velocity components just above the icing surface. Ice accretions under typical glaze ice conditions on a GLC-305 swept-wing model are calculated, and the predicted sectional ice shapes are compared with the experimental data as well as LEWICE results. It indicates that the current results reflect some major characteristics of glaze ice and the spanwise overflow phenomenon. Despite some discrepancies between the numerical results and experimental data, the overall growth patterns are reproduced well.

Multi-Stepping Ice Prediction on Cylinders and Other Relevant Geometries

Predicted ice shapes obtained with a fully automated multi-stepping procedure implemented in the ice prediction code ICECREMO2 are discussed in this paper. Several multi-step algorithms are used to generate ice layers on cylinders in rime and glaze ice conditions. Although all multi-step algorithms produce acceptable rime ice results, a multi-step approach based on an ice height criterion appears as the most efficient method for glaze ice predictions. The outcome is compared with results obtained for a NACA0012 airfoil geometry. The influence of the un-iced substrate shape is investigated, general restart criteria for multi-step height-based icing codes are presented and discussed.

Capacitive probe for ice detection and accretion rate measurement: Proof of concept

Abstract We demonstrate a concept potentially suitable for detecting in-cloud ice and indication of ice accretion rate within a laboratory setting. The concept measures the change in capacitance and resistance due to ice accretion between two charged cylindrical probes. An ice sensor using this concept could be located on meteorological towers or nacelle of wind turbines for icing measurements. During the controlled icing experiments, ice builds up on the cylindrical probes: capacitance increases and resistance decreases. Capacitance correlates with the mass, thickness and the location of ice deposits; the type of icing—glaze versus rime—correlates well with resistance measurements. A 2-D electric field simulation around cylindrical probes demonstrates the sensitivity of this ice sensor as a function of the distance between the probes and the location of ice deposition around the probes. Capacitance measurements using different acrylic annuli machined to high tolerances and placed over each probe to simulate ice validates the electric field simulation. Experimental tests of the cylindrical probes in an icing wind tunnel facility under controlled rime and glaze ice conditions validate the concept.

Ice Shape Prediction Based on an Improved Thermodynamic Model

An improved model for heat transfer process is established to study the ice accretion on airfoil, which takes into consideration the influence of conduction through ice and water film compared with the classical Messinger model. Incorporating the calculation of collection efficiency by the Eulerian two-phase theory, ice accretion in specific condition on a NACA0012 airfoil is simulated with the classical model and the improved model respectively. It is shown that the simulation result with the improved model agrees well with experiment data, and the model is demonstrated to be valid in ice shape prediction and complement the shortage of the Messinger model in the estimation of freezing fraction in glaze ice condition, especially in the initial stage of ice accretion.

Quantitative analysis of a two-dimensional ice accretion on airfoils

This paper presents the development of a code that can determine the shape of accreted ice on a 2D airfoil, verification of the code via quantitative parameters, and the variation in ice accretion according to ambient conditions. First, the 2D panel method is used as the aerodynamic solver, and Messinger’s model is used as the thermodynamic model. Second, the code is quantitatively verified through comparison with existing ice accretion analysis codes under rime, mixture, and glaze ice conditions. The parameters for comparison are the cross-sectional area of the ice, maximum ice thickness, ice heading, and distribution of the ice thickness measured on the airfoil surface. The verification shows that the developed code yields results of similar accuracy to existing analysis codes. Finally, ice shapes, depending on variations in the ambient conditions, are determined and investigated based on these parameters for comparison. The selected ambient condition parameters are freestream velocity, LWC, and temperature. The investigation is carried out for rime and glaze conditions. Increasing the freestream velocity produces an ice horn that increases the area over which the ice encounters liquid water in the air. The ambient temperature is the factor that alters ice accretion behavior; increasing the ambient temperature turns rime ice into glaze ice. Ice accretion area is increased at higher LWC. The LWC and the ice cross-sectional area show a linear relationship.

Flow distortion in an S-duct inlet with simulated icing effect and heat transfer

AbstractA diffusing S-duct aircraft intake system is computationally studied for the effects of inlet icing and wall heat transfer on engine face distortion. A Reynolds-Averaged Navier-Stokes (RANS) code with k -ω SST turbulence model is used to simulate the compressible viscous flow in the duct. The glaze ice accretion on the inlet lip is simulated as a fixed protrusion from NASA LEWICE3D code. The shape and size of the ice on the inlet lip are assumed to remain constant even in the case of the heated wall. The case of zero external heat transfer is modeled by the adiabatic wall boundary condition, and constant-wall temperature is used to simulate the heated wall effect. The freestream Mach number of 0·85 and glaze ice condition on the inlet lip produce massive flow separation at the lip and internal shock cell structure in the S-duct. The heated wall creates additional vorticity and thus increases the engine face distortion level. The area-averaged total pressure distortion at the engine face in a freestream Mach number of 0·85 is increased by ~7% in the heated wall case as compared to the adiabatic flow.

Relation between Angle of Attack and Atmospheric Ice Accretion on Large Wind Turbine's Blade

A numerical study of wind turbine blade profile's angle of attack variation on atmospheric ice accretion near the blade tip section was performed. Three dimensional computational fluid dynamics (CFD) based numerical analyses were carried out using NACA 64618 blade profile at five different angles of attack ranging from −5 to +7.5 degrees. Based upon the flow field calculations and the super cooled water droplet collision efficiency, the rate and shape of accreted ice was simulated for both rime and glaze ice conditions. The results show that atmospheric icing is less severe at lower angles of attack, both in terms of local ice mass and relative ice thickness.

Multistep Results in ICECREMO2

Multistep versions of the aircraft icing code ICECREM02 are investigated. Several multistep algorithms are presented and tested on a NACA0012 wing in rime and glaze ice conditions. The resulting ice layers are compared with experimental results and the efficiency of each algorithm is discussed. The step-by-step algorithm with an ice height criterion provided the most time-efficient solution in glaze ice conditions.

Ice accretion simulation on multi-element airfoils using extended Messinger model

In the current article, the problem of in-flight ice accumulation on multi-element airfoils is studied numerically. The analysis starts with flow field computation using the Hess-Smith panel method. The second step is the calculation of droplet trajectories and droplet collection efficiencies. In the next step, convective heat transfer coefficient distributions around the airfoil elements are calculated using the Integral Boundary-Layer Method. The formulation accounts for the surface roughness due to ice accretion. The fourth step consists of establishing the thermodynamic balance and computing ice accretion rates using the Extended Messinger Model. At low temperatures and low liquid water contents, rime ice occurs for which the ice shape is determined by a simple mass balance. At warmer temperatures and high liquid water contents, glaze ice forms for which the energy and mass conservation equations are combined to yield a single first order ordinary differential equation, solved numerically. Predicted ice shapes are compared with experimental shapes reported in the literature and good agreement is observed both for rime and glaze ice. Ice shapes and masses are also computed for realistic flight scenarios. The results indicate that the smaller elements in multielement configurations accumulate comparable and often greater amount of ice compared to larger elements. The results also indicate that the multi-layer approach yields more accurate results compared to the one-layer approach, especially for glaze ice conditions.

Reduced Flow of a Metastable Layer at a Two-Phase Limit

A solution procedure is outlined for predicting stable and metastable thermodynamic states, simultaneously, within a flowing supercooled surface film along an ice surface. This procedure involves a derived freezing fraction of incoming droplets in three-phase conditions, together with volume averaging to accommodate the momentum balance of the flowing surface layer. This approach yields the proper trends when the flow temperatures are lowered sufficiently toward a two-phase limit. In this way, it provides a single parameter over the range between two-phase (rime ice) and three-phase (glaze ice) conditions. Also, it permits film flow calculations below and/or above the phase change temperature. As a result, an Eulerian volume averaging approach can be successfully applied to problems involving impinging droplets and glaze ice, which have generally been solved previously by Lagrangian methods. The numerical analysis is based on a control-volume-based finite element method. The predicted results are successfully validated through comparisons with analytical solutions and measured data

Application of triple-deck theory to the prediction of glaze ice roughness formation on an airfoil leading edge

A viscous–inviscid interaction triple-deck structure is developed to describe the thermomechanical interaction of an air boundary layer with ice sheets and liquid films. Linear stability results are compared with nonlinear triple-deck computations, and a number of nonlinear simulations of air–water–ice interactions are presented. An icing instability is encountered in regimes with simultaneous wall and air cooling that is believed to admit small scale and highly irregular surface roughness. The stabilization of the smallest scale icing disturbances is obtained through the Gibbs–Thomson relation. This local thermodynamic condition relates the freezing temperature of a pure substance to the surface tension and the mean curvature of the interface and provides a short scale stabilizing mechanism for icing instability modes. Comparison with available experimental data on glaze ice roughness diameters, accreted on NACA 0012 airfoil leading edges under glaze icing conditions, is provided. It is also found in all cases computed in this study that water beads can be formed on a wetted ice surface once the water film is locally ruptured by ice roughness elements.