Simulation Of Ice Accretion Research Articles

Experimental and computational simulation of in-flight icing phenomena

This paper reviews experimental and computational methods used for simulation of ice accretion on aircraft flying through icing conditions. Such methods were recently reviewed by the AGARD FDP Working Group 20 and the present paper represents a revised and updated version of parts of the Working Group report. To provide essential background, it begins with a brief physical description of the ice accretion process. Experimental simulations must respect certain similarity requirements or scaling laws if they are to be valid; these requirements are discussed in some detail and in the framework of this discussion, physical phenomena are considered in more detail as well. Techniques and ground-based facilities for experimental simulation of ice-accretion phenomena are then reviewed, followed by a review of techniques and facilities used for flight testing in support of aircraft design and certification for flight in icing conditions. Available instruments for required measurements such as droplet size distribution and liquid water content and for inflight ice detection are briefly described. Computational simulation is becoming increasingly important in aircraft icing work; computational methods are used to simulate ice accretion both with and without iceprotection systems in operation. Computational approaches are outlined and current capabilities are evaluated. Conclusions emerging from the review include the following: rime icing is reasonably well understood and can be adequately simulated for most practical purposes using either experimental or computational methods; some of the physical phenomena known to be important in glaze icing are only poorly understood and there is considerable uncertainty regarding whether or not certain other phenomena are important; consequently, much additional research is required before reduced-scale experimental simulations or computational simulations of glaze icing will be sufficiently accurate and reliable for most practical purposes. Research recommendations are put forward.

Simulation of ice accretion on a cylinder due to freezing rain

AbstractA hybrid analytical and random-walk model has been developed to predict the shape of ice accreted on a horizontal cylindrical insulator due to freezing rain. The freezing rain occurs with the temperature of the vertically falling raindrops above the freezing point and the air temperature below freezing. The analytical model calculates the angular distribution of the water-film temperature and the location where freezing begins. The random-walk model predicts the accretion shape. The two random-walk model parameters, the freezing probability and the shedding parameter, are expressed as functions of the atmospheric conditions. The model predicts a variety of realistic accretion shapes from cylindrical to icicle-like. Model verification based on comparisons with other models and with experimental results demonstrates quantitatively and qualitatively the credibility of this new modelling approach.

Simulation of ice accretion on a cylinder due to freezing rain

AbstractA hybrid analytical and random-walk model has been developed to predict the shape of ice accreted on a horizontal cylindrical insulator due to freezing rain. The freezing rain occurs with the temperature of the vertically falling raindrops above the freezing point and the air temperature below freezing. The analytical model calculates the angular distribution of the water-film temperature and the location where freezing begins. The random-walk model predicts the accretion shape. The two random-walk model parameters, the freezing probability and the shedding parameter, are expressed as functions of the atmospheric conditions. The model predicts a variety of realistic accretion shapes from cylindrical to icicle-like. Model verification based on comparisons with other models and with experimental results demonstrates quantitatively and qualitatively the credibility of this new modelling approach.

Measurements in a leading-edge separation bubble due to a simulated airfoil ice accretion

The separation bubble formed on an airfoil at low Reynolds number behind a simulated leading-edge glaze ice accretion is studied experimentally. Surface pressure and split hot-film measurements as well as flow visualization studies of the bubble reattachment point are reported. The simulated ice generates an adverse pressure gradient that causes a laminar separation bubble of the long bubble type to form. The boundary layer separates at a location on the ice accretion that is independent of angle of attack and reattaches at a downstream location 5-40 percent chord behind the leading edge, depending on the angle of attack. Velocity profiles show a large region of reverse flow that extends up from the airfoil surface as much as 2.5 percent chord. After reattachment, a thick distorted turbulent boundary layer exists. The separation bubble growth and reattachment are clearly seen in the plots of boundary-layer momentum thickness vs surface distance. Local minima and maxima in the boundary-layer momentum thickness development compare well with the shear layer transition point as indicated by the surface pressures and the reattachment point as measured from surface oil flow, respectively.