A Two-dimensional Splashing Model for Investigating Impingement Characteristics of Supercooled Large Droplets

This document is the Accepted Manuscript of the following article: C. Wang, S. Chang, M. Leng, H. Wu, and B. Yang, 'A two-dimensional splashing model for investigating impingement characteristics of supercooled large droplets', International Journal of Multiphase Flow, Vol. 80, April 2016, pp. 131-149. This manuscript version is made available under the terms of the Creative Commons CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/. The Version of Record is available online at doi: https://doi.org/10.1016/j.ijmultiphaseflow.2015.12.005. © 2015 Elsevier Ltd. All rights reserved.In this article, a two-dimensional (2D) splashing model is proposed to investigate the dynamics when supercooled large droplets (SLD) impinging on a wall surface in the aircraft-icing field. Energy conservation for droplet motion and impingement is used to capture the properties of the splashed droplets. A new statistical treatment of the droplet impinging energy and angle during the droplet-wall interaction is introduced in order to calculate the average dynamics of the SLD within a micro-control volume on wall surface. Based on the LEWICE predictions of droplet collection efficiencies and the available experimental ones, a new criterion for droplet splashing/deposition as well as a new formulation for the splashed mass is suggested. Lagrangian approach is adopted to describe the movement and impingement of SLD. The proposed model together with the previously developed droplet tracking method (DTM) for calculating droplet collection efficiency with the effect of droplet reimpingement constitute a relatively complete predicting approach of SLD impingement characteristics. Comparisons between the current predictions and the experimental observations, including SLD impingement over clean and contaminated airfoil surfaces as well as shapes of ice accretion in typical icing conditions, are carried out. Further, results obtained with the LEWICE splashing model are also plotted on the same graphs in order to assess the accuracy of the current splashing model in predicting SLD impingement. Results show that good agreement is achieved between the current predictions, including SLD impingement and ice accretion shapes, and the experimental ones. The predictions of the impingement distribution over contaminated surfaces obtained with the current splashing model show a much closer agreement with the experimental results than the ones obtained with LEWICE splashing model. For further investigation of SLD impingement, the properties of the droplet splashing and reimpingement during the ice accretion process are also addressed.Peer reviewe

An immersed boundary method using unstructured anisotropic mesh adaptation combined with level-sets and penalization techniques

The interest on embedded boundary methods increases in Computational Fluid Dynamics (CFD) because they simplify the mesh generation problem in the case of the Navier–Stokes equations. The same simplifications occur for the simulation of multi-physics flows, the coupling of fluid–solid interactions in situation of large motions or deformations, to give a few examples. Nevertheless an accurate treatment of the wall boundary conditions remains an issue of the method. In this work, the wall boundary conditions are easily taken into account through a penalization technique, and the accuracy of the method is recovered using mesh adaptation, thanks to the potential of unstructured meshes. Several classical examples are used to demonstrate that claim

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Construction of a p-adaptive continuous residual distribution scheme

A p-adaptive continuous residual distribution scheme is proposed in this paper. Under certain conditions, primarily the expression of the total residual on a given element K into residuals on the sub-elements of K and the use of a suitable combination of quadrature formulas, it is possible to change locally the degree of the polynomial approximation of the solution. The discrete solution can then be considered non continuous across the interface of elements of different orders, while the numerical scheme still verifies the hypothesis of the discrete Lax–Wendroff theorem which ensures its convergence to a correct weak solution. We detail the theoretical material and the construction of our p-adaptive method in the frame of a continuous residual distribution scheme. Different test cases for non-linear equations at different flow velocities demonstrate numerically the validity of the theoretical results. © 2017, Springer Science+Business Media New York

Immersed boundaries in hypersonic flows with considerations about high-fidelity and massive parallelism

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