INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS Int. J. Numer. Meth. Fluids (2011) Published online in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/fld.2588 An ALE mesh movement scheme for long-term in-flight ice accretion M. Fossati, R. A. Khurram * ,† and W. G. Habashi CFD Lab, Department of Mechanical Engineering, McGill University, Montreal, QC H3A 2S6, Canada SUMMARY The rather irregular shapes that glaze ice may grow into while accreting over the surface of an aircraft repre- sent a major difficulty in the numerical simulation of long periods of in-flight icing. There is a constant need for remeshing: a wasteful procedure. In the framework of ALE formulations, a mesh movement scheme is presented, in which frame and elasticity analogies are loosely coupled. The resulting deformed mesh pre- serves the quality of elements, especially in the near-wall region, where accurate prediction of heat flux and shear stresses is required. The proposed scheme handles mesh deformation in a computationally efficient manner by localizing the mesh deformation. The 2D problem of ice accretion over single and multi-element airfoils is considered here as a numerical experiment. Experimentally measured glaze ice shapes were used to evaluate the performance of the present approach. Copyright © 2011 John Wiley & Sons, Ltd. Received 9 August 2010; Revised 24 February 2011; Accepted 26 March 2011 KEY WORDS: in-flight icing; ALE; mesh movement; elasticity; mesh quality; computational efficiency 1. INTRODUCTION The accurate simulation of ice accretion over the wings and other surfaces of an aircraft is a key issue in the growing acceptance of computational fluid dynamics as an aid to in-flight icing cer- tification. The credibility of any numerical simulation significantly depends on the quality of the mesh used to discretize the computational domain. A major challenge in ice accretion problems lies in the development of a mesh rezoning technique to adapt the mesh to the rapidly changing spatial domain. A complete remeshing [1] of the domain as ice modifies the shape of the body may result in increased computational time, loss of accuracy due to interpolation, and necessity of load redistribution in the case of parallel computations. Another possibility is the adoption of a standard ALE approach, together with an elasticity-based mesh movement technique [2]. In such a scheme, the original mesh, based on the clean surface, is gradually deformed according to the shape of the accreting ice. Although ALE-based interface tracking techniques work well for fluid–structure interaction (FSI) problems [2–6], ice shapes are often irregular. Mesh movement techniques may thus produce skewed elements or even degenerate ones. An alternative is to solve the fully cou- pled elasticity equation [7], but even that cannot enforce strict mesh orthogonality at the surface. A fourth-order bi-harmonic equation would be required to enforce surface orthogonality as a Dirichlet boundary condition. These alternatives are computationally expensive. The main goal of this work is to present a computationally efficient mesh motion scheme that borrows the superior properties of the above-mentioned approaches, while dispensing with the onerous ones. The present scheme is thus based on frame and elasticity analogies but in a loosely coupled way. *Correspondence to: R. A. Khurram, CFD Lab, Department of Mechanical Engineering, McGill University, Montreal, QC H3A 2S6, Canada. † E-mail: rkhurram@cfdlab.mcgill.ca Copyright © 2011 John Wiley & Sons, Ltd.