Ice growth may rapidly degrade the aerodynamic performance of an aircraft. It can also severely damage structures such as communication towers or power lines. Subsequently, de-icing and anti-icing systems have been developed and a number of codes designed to predict ice shapes. When ice accretion starts, two different types of ice can appear, depending on the temperature and conditions. All of the incoming fluid may freeze almost instantaneously and turn into rime ice. Alternatively, a fraction of the incoming fluid may freeze and turn into glaze ice while the other part remains liquid and may flow over the ice. Previous work on ice accretion has mainly targeted the ice shape and neglected the owing water layer. The present study focuses on this. A set of governing equations is derived for both rime ice growth and coupled ice growth and water flow. When rime ice accretes, a mass balance is used to calculate the shape. In the presence of both ice and water, the ice growth is governed by an energy balance and the water flow by a mass balance. These equations are solved numerically for the water flow alone and the coupled ice growth and water flow for two- and three-dimensional at inclined planes. The behaviour of both ice and water is studied. The model is then extended to deal with arbitrary substrates and solutions are sought for industrially important applications such as ice accretion on power lines or aerofoils. This research work forms part of the ICECREMO project. ICECREMO is a three-dimensional ice accretion and water flow code developed collaboratively by DERA, British Aerospace, Rolls Royce, GKN Westlands Helicopters and Cranfield University under the auspices of the UK department of Trade and Industry.

Computational investigations were carried out to evaluate the effectiveness and usability of hybrid RANS/LES techniques for predicting the unsteady separated flow over wings with ice accretion. RANS and hybrid RANS/LES computations were performed using the viscous flow solver CHEM with the SST turbulence model. Two configurations were considered during the study: an extruded wing with a glaze-ice shape and a swept wing with a simulated glaze-ice accretion. Hybrid RANS/LES results, in general, predict a less active shear layer ``roll up' than seen in the experimental data. Qualitative improvements are seen in the hybrid RANS/LES results over corresponding RANS results. The extruded wing results show that the CHEM hybrid RANS/LES results are similar to the AVUS DES results. The use of preconditioning and a different turbulent model in CHEM showed a slight improvement in results.

A computational model is developed to simulate the impact dynamics of a droplet on solid substrates with the purpose of predicting the droplet spreading characteristics over time. Previous studies focused on finding relations between the impact parameters and outcome dynamics. A modified approach like the one used in this project revolves around modeling the moving contact lines at the interface in a multiphase flow environment. Focusing on research from an aircraft de-icing point of view, this study is considered a prerequisite in understanding the physics of droplet impact. The primary focus is on extending the application to incorporate super-cooled environments. Development of the model involved the use of the Volume-of-Fluid function coupled with the High-Resolution Interface Capturing scheme to model the moving contact line. The evolution of the moving contact line is modeled with contact angles as their inputs to understand the effect of the surface tension forces. Contact angle modeling is based on the Blended-Kistler method, which captures the contact angle evolution based on the surface tension and capillary number. Preliminary validation performed on the model proves its effectiveness in accurately simulating the impact behavior when compared to the literature, where the spread diameter and height agree well with experiments. The validated model is also compared to the in-house experiments performed at the Cavitation and Multiphase flow laboratory using different substrate materials. The substrates each show unique behavior - Impact on Glass results in the droplet depositing on the surface. Aluminum results in a full rebound and PET-G, results in a drop ejection. Based on inputs from the experiments - contact angles, spread diameter, and the maximum spread $beta$, show good agreement in comparison to the literature. / Master of Science / Computational model developed to simulate the impact dynamics of the droplet on solid surfaces, which predicts the evolution of the droplet over time in order to analyze the effect of the surface and properties of the fluid on the behavior of the droplet on impact. Focusing on research from an aircraft de-icing point of view, this study is considered a pre-requisite in understanding the physics of droplet impact, with potential scope in extending the simulation to applications at temperatures lower than $0^{circ}$ C. A model developed with the help of basic governing equations in fluid mechanics helps capture the effect of interactions between different physical states. The angle at which the droplet interacts with the surface (Contact Angle) and the diameter evolution (d/D) help us understand the effectiveness of the model to simulate droplet impact. Preliminary validation of the model is performed with respect to the literature where the droplet diameter evolution and the height variation match well with the experiments, which was the major criterion in determining the accuracy of the model. This model is compared to the in-house experiments performed at the Cavitation and Multiphase flow laboratory on different surfaces such as Glass, Aluminum, and Plastic (PET-G). The surfaces each show unique behavior with impact on Glass having the droplet deposit on the surface, aluminum resulting in the droplet bouncing after hitting the surface, and PET-G resulting in a small droplet being ejected from the bigger droplet which eventually deposits on the surface. Conclusions from the comparison between the experiments and the numerical simulation show how the model is effective in capturing the impact behavior on surfaces like glass in comparison to surfaces like Aluminum in this case that repels water.

No description available.

The Diploma Thesis concerns investigation of icing effects at L 410 NG aircraft. The aircraft is certified under FAR/CS/AP-23 Commuter category. An analysis was performed for existing Pneumatic De-icing Boots System at the wing area according to three flight configurations and icing conditions referring to document Part 25 Appendix C and O. The analysis was done by CFD solver FENSAP-ICE for various runs with respect to the icing envelope. Cases were assigned as two 2D cross-sections situated at the aircraft’s wing aileron part. Cross-sectional Reynold’s number oscillate between 4.5–8.5×106. Automatic operation of Pneumatic De-icing Boots System was proposed. Attention was paid to the ice accretion aft to the Pneumatic De-icing Boots System. The Appendix (Příloha) P6 contains an English written Article concerning main Diploma Thesis sections.

No description available.

Approved for public release, distribution is unlimited / In this thesis, a fuzzy logic algorithm is developed for the detection of potential aircraft icing conditions using the Moderate-Resolution Imaging Spectroradiometer (MODIS). The fuzzy MODIS algorithm is developed in a manner similar to the cloud mask currently used to process MODIS imagery. The MODIS icing potential detection algorithm uses thresholds for 8 channels in a series of 12 tests to determine the probability of icing conditions being present within a cloud. The MODIS algorithm results were compared to results of the GOES icing potential detection algorithm run on MODIS imagery for 4 cases. When compared to positive and icing pilot reports for the cases, the MODIS algorithm identified regions where icing was encountered more effectively than the GOES algorithm. Furthermore, the use of fuzzy thresholds on MODIS rather than the hard thresholds of the GOES algorithm allowed for less restrictive coverage of potential icing conditions, making the MODIS algorithm more reasonable in assessing all cloud regions for icing potential. The results found here are preliminary, as further statistical analysis with a larger validation dataset would be more effective. Algorithm details are provided in the appendix for reference. / Captain, United States Air Force

Le travail réalisé dans cette thèse introduit le concept de l'utilisation de la méthode Level-Set pour simuler l'interface Glace/Air au cours du temps lors du processus de givrage en vol des aéronefs. Pour cela, un code de givrage tri-dimensionnel multi-blocs et parallélisé a été implémenté au sein du solveur NSMB (Navier-Stokes-Multi-Blocks). Il comprend notamment un module de calcul des trajectoires des gouttelettes par une approche Eulérienne compatible avec l'utilisation de grilles chimères et un module thermodynamique pour le calcul des masses de glace incluant deux modèles différents : un modèle algébrique itératif et un modèle à dérivées partielles. Une attention particulière a été portée sur la vérification du code de givrage implémenté en comparant systématiquement, si possible, les résultats obtenus avec les données expérimentales et numériques existantes dans la littérature. Pour cette raison, le module de déformation de maillage existant dans NSMB a été intégré au code implémenté afin de pouvoir simuler le givrage par une méthode traditionnelle. Enfin, un nouveau principe pour le suivi de l'interface glace/air est introduit via l'utilisation d'une méthode Level-Set. Puisque dans ce travail de thèse nous nous intéressons particulièrement au concept, la méthode Level-Set développée est d'ordre un et est résolue implicitement. On montrera cependant que des résultats valides sont obtenus avec une telle approximation. / This thesis introduces the concept of the Level-Set method for simulating the evolution through time of the ice/air interface during the process of in-flight aircraft icing. For that purpose, a three-dimensionnal multi-block and parallelized icing code have been implemented in the NSMB flow solver (Navier-Stokes-Multi-Blocks). It includes a module for calculating the droplet trajectories by an Eulerian approach compatible with the use of chimera grids and a thermodynamic module to calculate the ice masses including two different models : an iterative algebraic model and a PDE model. Particular attention was paid to the validation of the icing code irnplemented by comparing results with existing experimental and numerical data in the literature. For this reason, the existing mesh deformation algorithm in NSMB was integrated into the code to simulate icing by a traditional method. Finally a new principle to track the ice/air interface is introduced using the Level-Set method. Since we are particularly interested in the concept, the Level-Set method developped is first order and solved implicitly. However it will be shown that valid results are obtained with such an approximation.