Lagrangian Parcel Volume method applied to icing surfaces to predict impact efficiency

When trying to predict how and where ice will accrete on an aircraft, engineers first need to be able to track the path and concentration of water particles; this will allow for a better representation of water impingement and ice accretion. This tracking can be accomplished by using either a Lagrangian computational method, which tracks particle paths with no diffusion, or an Eulerian computational method, which uses a partial differential equation to calculate concentrations with high efficiency. The current study expands upon previous work which developed a new Lagrangian computational method, called the Lagrangian Parcel Volume (LPV) method. The LPV method uses Lagrangian particle trajectories which define a parcel’s volume to compute particle concentration. The change in particle concentration (particle volume per mixed-fluid volume) can be determined directly by comparing the final volume of a parcel to its initial value. Previous investigations with the LPV method found that it provides accurate and efficient results when compared with other computational techniques. A two-dimensional (2-D) unsteady potential cylinder flow was used for most predictions. In chapter I of this study, different aspects of the LPV method’s computational makeup were investigated for impact efficiency predictions. These studies included parcel shape definition, varying the number of parcels released in a given simulation, using a non-linear drag model for particle trajectory calculations, and also, varying the timestep used in simulations. Futher studies performed investigated the effects on impact efficiency due to unsteady flow oscillations and polydisperse particle distributions. LPV impact efficiency predictions on the clean two-dimensional four inch cylinder were found to agree well with experimental data. iii In chapter II of this study, the LPV method was further expanded by implementing a new type of flowfield into the code: Large Eddy Simulations (LES). LES flowfields are needed to describe upstream unsteadiness and flow separation for complex geometries. Two geometries were studied in these LES simulations: a clean four inch diameter cylinder and a large glaze ice model (mounted on a two inch diameter cylinder). Impact efficiency predictions for both geometries were found to agree well with experimental data. This research demonstrates the LPV method can be used for both potential and LES flowfields while displaying high accuracy and efficiency