Study of Dry Ice Growth on Duplex Cylinders

A study of dry ice growth on bundled (duplex) cylinders has been performed using icing wind tunnel experiments and computational fluid dynamics (CFD) numerical simulations. The aim of this study is to "fill the gaps" in the works of Wagner (2010) and Qing et al. (2018). The numerical simulations cover a range of possible icing conditions by varying the operating wind speed, median volume diameter, and for some cases−the angle of incidence between the cylinders. The obtained results for the 0° AoA show that the accreted ice masses ratio between the leeward and windward cylinder varies from ~ 100% to ~ 30%. The accreted ice masses ratio decreases with the increase in the wind speed and/or median volume diameter. For the cases with non-zero AoA, the accreted ice masses become approximately equal, when the AoA is large enough to produce a vertical separation equal or greater to one cylinder diameter

Steady and Time Dependent Study of Laminar Separation Bubble (LSB) behavior along UAV Airfoil RG-15

The flow around the Unmanned Arial Vehicle (UAV) operating at a low Reynolds number regime of the O() is predominantly laminar and it leads to the formation of Laminar Separation Bubble (LSB). The pressure, shear stress, and heat flux distribution are considerably affected by LSB, which affects lift, drag, and pitching moment values. Most existing RANS (Reynolds-Averaged Navier-Stokes) turbulence models are built on the assumption of fully turbulent flow. Therefore, these models require additional transport equations or reformulations or specific transition information to predict the LSB observed in low Reynolds number transition flows. Steady and transient computational fluid dynamics simulations were done using the RANS based transition turbulence model to study the behavior of LSB on UAV airfoil RG-15. The transition turbulence model can predict the LSB with considerable accuracy. The steady state and time averaged simulation results are matching in the pre stall region but deviates after stalling. High amplitude velocity fluctuations were observed near regions of transition and separation

Cable Propelled Gondola System Operation in Icing Conditions

The scope of this study comprehends problems associated with modern urban vehicles known as cable propelled gondolas system operations in icing conditions. The aspects under consideration are problems related to the operations, safety, and maintenance of cable car systems in harsh climate conditions. The geographical location of the gondola cars makes them vulnerable to severe weather conditions especially in cold climates of the northern hemisphere, where icing on its components is an operational, maintenance, and safety concern. The harsh climate conditions can cause unadorned malfunctions posing a threat to the integrity the of system as well as a high risk to human safety. The study basis on the identification of these problems in operational, maintenance and safety domain including implications the industry faces in the form of severe accidents costing precious lives and lost capital. Furthermore, it incorporates the ice detection, anti/de-icing approaches as well as the safety strategies in use nowadays. The massive increase in operations and dynamic climate conditions gondola cars require serious attention. This study unsheathes serious underlying problems that severely affect the gondola operations, makes them prone to major maintenance shutdowns and poses high risk to structural and human safety. The identified problems in this study and severity of risks draw attention to need for practicable solutions incorporating de-icing and ice removal techniques for safe operation of gondolas in cold climates saving time, effort, inconvenience, and prodigious lost capital

Railway operations in icing conditions: a review of issues and mitigation methods

This article focuses on studying the current literature about railway operations in icing conditions, identifying icing effects on railway infrastructure, rolling stock, and operations, and summarizing the existing solutions for addressing these issues. Even though various studies have been conducted in the past on the impact of winter, climate change, and low temperatures on railway operations, not much work has been done on optimizing railway operations under icing conditions. This study demonstrates that further research is needed to better understand ice accretion and its effects on different parts of railways. It appears that railway infrastructure faces serious problems during icing conditions, and additional research in this field is required to precisely identify the problems and suggest solutions. Therefore, it is important to enhance the knowledge in this area and suitable optimal and cost-effective ice mitigation methods to minimize icing effects on railway operations and safety

Aerodynamic forces on iced cylinder for dry ice accretion – A numerical study

Within this paper the ISO 12494 assumption of standard of slowly rotating reference collector under ice accretion has been tested. This concept, introduced by (Makkonen, 1984), suggests that the power line cables, which are the basis of the “reference collector” in the ISO framework, are slowly rotating under ice load, due to limited torsional stiffness. For this purpose, several Computational Fluid Dynamics (CFD) simulations of the atmospheric ice accretion and transient airflow conditions over iced cylinder at different angles of attack were performed. In order to ascertain the similarity, several parameters were chosen, namely, drag, lift and moment coefficients, pressure and viscous force. The results suggest that the benchmark cases of rotating and uniced cylinder have “similar” aerodynamic loads when compared with the “averaged” results at different angles of attack (AoA), namely, the values of total pressure and viscous force. However, on individual and instantaneous basis the difference in the airflow regime between AoA cases and the benchmark cases can be noticeable. The results from the ice accretion simulation suggest that at long term the gravity force will be the dominating one, with rotating cylinder being a good approximation to the “averaged” angle of attack cases for the ice accretion

Ice Accretion on Fixed-Wing Unmanned Aerial Vehicle—A Review Study

Ice accretion on commercial aircraft operating at high Reynolds numbers has been extensively studied in the literature, but a direct transformation of these results to an Unmanned Aerial Vehicle (UAV) operating at low Reynolds numbers is not straightforward. Changes in Reynolds number have a significant impact on the ice accretion physics. Previously, only a few researchers worked in this area, but it is now gaining more attention due to the increasing applications of UAVs in the modern world. As a result, an attempt is made to review existing scientific knowledge and identify the knowledge gaps in this field of research. Ice accretion can deteriorate the aerodynamic performance, structural integrity, and aircraft stability, necessitating optimal ice mitigation techniques. This paper provides a comprehensive review of ice accretion on fixed-wing UAVs. It includes various methodologies for studying and comprehending the physics of ice accretion on UAVs. The impact of various environmental and geometric factors on ice accretion physics is reviewed, and knowledge gaps are identified. The pros and cons of various ice detection and mitigation techniques developed for UAVs are also discussed

Ice Accretion on Rotary-Wing Unmanned Aerial Vehicles—A Review Study

Ice accretion on rotary-wing unmanned aerial vehicles (RWUAVs) needs to be studied separately from the fixed-wing UAVs because of the additional flow complexities induced by the propeller rotation. The aerodynamics of rotatory wings are extremely challenging compared to the fixed-wing configuration. Atmospheric icing can be considered a hazard that can plague the operation of UAVs, especially in the Arctic region, as it can impose severe aerodynamic penalties on the performance of propellers. Rotary-wing structures are more prone to ice accretion and ice shedding because of the centrifugal force due to rotational motion, whereby the shedding of the ice can lead to mass imbalance and vibration. The nature of ice accretion on rotatory wings and associated performance degradation need to be understood in detail to aid in the optimum design of rotary-wing UAVs, as well as to develop adequate ice mitigation techniques. Limited research studies are available about icing on rotary wings, and no mature ice mitigation technique exists. Currently, there is an increasing interest in research on these topics. This paper provides a comprehensive review of studies related to icing on RWUAVs, and potential knowledge gaps are also identified

Study of Airflow Behavior for Duplex Circular Cylinders

The modeling of atmospheric ice accretion on duplex cylinders received a limited attention, with modeling carried by Wagner and Qing et al. The publicly available experimental data about the ice accretion on the duplex cylinders is limited to experiments of Qing et al. and Veerakumar et al. When comparing the data of Wagner and Qing et al. with the results of Veerakumar et al., the major difference is the airflow behavior in the wake of the windward cylinder, the extent of the wake and recirculation bubble, and the velocity distribution in the wake. Thus, its needed to study the effect of the turbulence model on the airflow behavior of duplex cylinders, with focus being the behavior of the wake of the windward cylinder. This study reports the simulation results of the complex airflow behavior of duplex circular cylinder bundle obtained using several turbulence models employed by commercial CFD code

Study of Wind Flow Angle and Velocity on Ice Accretion of Transmission Line Composite Insulators

Ice accretion on insulators in cold regions is a serious and inevitable problem for power transmission lines, which may cause over-load and icing flashover accidents and can lead to wide power outage. In this research work, multiphase numerical simulations are carried out to investigate the effect of wind flow angle & velocity on the ice accretion of transmission line composite insulators. To verify the simulation results, lab-based icing tests are carried out in artificial climate chamber of Chongqing University. Results show that the change of wind flow angle has an obvious effect on both accreted ice shape and ice mass of insulators. When wind flow angle changes from 0° to 90° or -90°, the ice mass increases before dropping sharply. Meanwhile, ice mass accretion on insulators with wind flow angle is more sensitive to the change of wind velocity. For V-shape insulator strings, the ice mass increased 47.22% in average compared to ordinary suspension insulators. The findings of this research can provide significant engineering reference for the design of transmission line in icing prone areas