Numerical Study On Water Shedding Model And Ice Accretion

When the aircraft flies in the atmosphere or the clouds containing super-cooled water droplets,ice accretion may occur on the exposed surface such as airfoil and engine-inlet because of the im-pingement of the super-cooled water droplets.It will cause aerodynamics performance decrease,poor maneuverability and flying security hazard.It is crucial to study the ice accretion on aircraft in engineering.Glaze ice,with a thin water film on the ice surface,is the most common and dangerous ice state.Water film flows downstream,continues freezing and even sheds from the surface due to ex-ternal force like air drag force.So freezing phase change and water film flow during ice accretion is tightly coupled,and simulation precision of water film has direct effect on simulation precision of ice accretion.The study on ice accretion at present rarely considers water film flow and shedding from the ice surface.The current coupled icing model between water film and ice accretion thought water film which exceeded 10^-4m was blew away.The approach based on the fixed value was simple and deviated largely from real physical process.Based on current coupled icing model between water film and ice accretion,the research focus of this thesis was to analyze the water film flow during ice accretion,establish a mathematic model of water film shedding,and perfect current icing model.Meanwhile numerical study for ice accretion on the airfoil and rotating spinner was presented.With the method of work balance analysis,a mathematic model of water film shedding on the horn ice surface was established in this thesis.The related calculation method was also developed.The coupled icing program between water film and ice accretion was supplemented with water shed-ding model.Ice shape of non-rotating cylinder agreed better with experimental result than ice shape of the approach based on the fixed value,indicating the current model is reasonable.The results of sim-ulation on NACA0012 airfoil showed that,the horn ice grows with the increase of ice accretion time,the proportion of water film shedding increases with the intensification of air backflow and water film accumulation.The ice shape of horn ice area was obviously less than ice shape of the ap-proach based on the fixed value.A mathematic model of water film shedding on the rotating component was also established with the method of work balance analysis in this thesis.The related calculation method was also de-veloped.The coupled icing program between water film and ice accretion was refined.The agreement between ice shape achieved from simulation on rotating spinner and experimental result validated the model.Numerical study on rotating spinner in different rotating speed and different air speed was also carried out.The results showed that,the proportion of water film shedding increases with a larger rotating speed in the other same condition.The impingement limit and ice range reduce with larger rotating speed.In the other same condition,the proportion of water film shedding increases with a larger air speed.The impingement limit and ice range reduce with a smaller air speed.The water film shedding model on the ice surface in this thesis may improve simulation accuracy of thin water film and ice accretion,provide better technical means for anti-icing system on aircraft.