Ice accretion on aircraft sensors is a signicant concern for manufacturers,pilots, and passengers alike. A substantial amount of non-fatal and fatalincidents are attributed to the icing of sensory equipment on commercialaircraft. The most prominent and recent incident involving Air France flightAF 447 with 228 fatalities and caused by ice crystals that had built up on theaircraft’s pitot tubes displaying an incorrect airspeed to the cockpit.The build-up of ice on flight surfaces is usually countered by implementingelectrical or mechanical methods that will either heat or remove the ice.Mechanical means generally use hydraulic systems to break the ice onceformed.
Electrical methods typically involve heating the surface directly,preventing ice from forming. This is the only method that is viable for sensoryequipment. Bleed air from the engines was previously used to heat thewings of the aircraft along with providing air for the pneumatic systems.However, with recent desires to improve the efficiency of jet engines, it isno longer feasible to use bleed air to heat these areas. As such, it is importantto understand where ice will form on the aircraft so that preventativemeasures can be positioned effectively.
Previous research has been conducted into the prediction of ice formationon aerofoils and simple geometric bodies such as spheres and cylinders byNACA, DERA, ONERA, and the MoD. The results the programmes developedare accurate in predicting how ice will form on an airfoil and can beobserved in reference 1 and 5. Alongside computational research, therehave been many physical experiments conducted in this area.
With reference8 having an aerofoil travel in a circular path collide with singledroplets, while reference 1 used a rotating multicylinder attached to anaircraft to obtain data for various ranges of parameters.1.2 Aims and objectivesThe aim of this experiment is to begin the process of mitigating ice accretionthrough a calculated prediction of where rain drops are likely to collide withan aircraft’s external instrumentation and how much water is caught. Thiswill be simulated in MatLab by focusing calculations on a Rankine halfbodyand cylinder. The aims to be completed following the objectives setare:Plotting the body shapes and streamlines in MatLabCalculating the droplet trajectories and superimposing results overbody plotsVerifying the results found with known published results1.3 Report Outline and ScopeThis report will outline the main factors of the project, demonstrating theapplication of predicting droplet trajectories and the factors that influencethem.
The research conducted within this paper will compare the results ofdroplets colliding with a cylinder produced through MatLab against resultsgiven through previous experiments using privately developed software.The project goal is to successfully implement and better understand potential flow theory, laplacian flow, and droplet characteristics and combinethese by superimposing the components into MatLab. The MatLab plotwill contain: The body, the potential stream flow around the body, and thedroplet trajectories. The results of this code include the overall catch efficiency, local catch efficiency, and the comparison of these catch efficienciesover the set range.This project will only encompass the initial steps in predicting ice accretionon a pitot tube. This means that it will be determined by calculating thecatch efficiency of a Rankine half-body in a Laplacian flow colliding withspherical water droplets at a given inertia parameter K.