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Bakkar A.,McGill University | Habashi W.G.,McGill University | Fossati M.,McGill University | Baruzzi G.S.,Newmerical Technologies International
Computers and Fluids

A stabilized finite element formulation of the level set equation is proposed for the numerical simulation of water droplet dynamics for in-flight ice accretion problems. The variational multi-scale and Taylor-Galerkin approaches are coupled such that the temporal derivative in the weak Galerkin formulation is replaced with a Taylor series expansion improving the temporal accuracy of the scheme. The variational multi-scale approach is then applied to the semi-discrete equation, allowing the stabilization terms to appear naturally. Taylor series expansions up to the fourth order have been studied in terms of accuracy and convergence rates. A second order implicit expansion was found to provide a good trade-off between accuracy and computational cost when compared to a fourth order implicit expansion. Validation is done through a number of benchmark cases considering droplet stretching and high-speed advection. Results indicate good mass conservation characteristics compared to other methods available in the literature. © 2015 Elsevier Ltd. Source

Fouladi H.,McGill University | Fouladi H.,CFD Laboratory | Habashi W.G.,McGill University | Habashi W.G.,CFD Laboratory | Ozcer I.A.,Newmerical Technologies International
Journal of Aircraft

Computational modeling of ice accretion on a rotorcraft is an alternative and/or a complement for flight test in icing certification and ice protection system design. Although computational fluid dynamics solutions of helicopter flow have advanced in the last few years, icing simulations are rare and, to the best of the authors' knowledge, none has modeled helicopter icing completely. In this work, a three-dimensional simulation of long-term in-flight ice accretion, accounting for rotor-fuselage quasi-steady interaction, is performed. For flow solution, the three-dimensional compressible turbulent Navier-Stokes equations are solved, with the rotor modeled as an actuator disk that imparts radial and azimuthal distributions of pressure rise and swirl to the flow field. The authors' code FENSAP-ICE is used to solve the three-dimensional flow, impingement, and ice accretion. The flow solutions for a test case, at two forward speeds, are obtained and validated against published experimental results and then used to illustrate icing on the helicopter's fuselage. Also, in this work, the effects of different parameters (such as forward speed, ambient temperature, droplet diameter, and liquid water content) on droplet impact, ice accretion, and the aerodynamic degradation of helicopter fuselage, were studied. Copyright © 2013 byWagdi G. Habashi. Source

Veillard X.,McGill University | Veillard X.,Imperial College London | Habashi W.G.,McGill University | Habashi W.G.,CFD Laboratory | Baruzzi G.S.,Newmerical Technologies International
Journal of Propulsion and Power

The present paper develops the particular methodology required to simulate icing not only on the front of a jet engine, but inside multistage ones, to respond to recent safety and performance concerns. When flying in certain weather conditions, engines have been found to ingest a mix of iced and liquid particles that can result in a dangerous buildup onthe internal components of the compressor. The ice can then shed and may cause mechanical damage and performance losses to downstream components. To cost-effectively replicate such an environment, a threedimensional quasi-steady numerical approach is developed to model both rotating and static components and their interaction. An intercomponent mixing-plane approach, along with stagnation and radial equilibrium boundary conditions, has been implemented, allowing the treatment of multistage unequal-pitch blade rows via afinite element interpolation method and proper circumferential averaging. The approach is first validated for the well-documented Aachen turbine, and then used on a NASA compressor stage to highlight impingement locations of supercooled droplets and the corresponding ice shapes. Copyright © 2011 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. Source

Bilodeau D.R.,McGill University | Bilodeau D.R.,CFD Laboratory | Habashi W.G.,McGill University | Habashi W.G.,CFD Laboratory | And 3 more authors.
Journal of Aircraft

A conservative Eulerian numerical approach for modeling postimpact Supercooled Large Droplets undergoing splashing and bouncing on aircraft surfaces is presented. The approach introduces the effect of the postimpact droplets by successive solutions of the conservation equations. Two models have been selected to identify the droplet splashing and bouncing conditions, and to provide initial conditions for the reinjected water. The method has been applied to droplet impingement in Supercooled Large Droplet conditions on clean and iced NACA 23012 geometries, as well as the MS(1)-0317 airfoil, and the results have been compared to experimental data. Good agreement is observed for both impingement limits and collection efficiency. Additionally, the method has been applied to a threeelement high-lift configuration operating in one of the proposed Appendix O Supercooled Large Droplet environments to demonstrate the danger posed by the re-impingement of splashing and bouncing droplets on complex interacting aerodynamic components. © 2014 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. Source

Aube M.S.,Newmerical Technologies International | Habashi W.G.,Newmerical Technologies International | Habashi W.G.,McGill University | Wang H.,Newmerical Technologies International | Torok D.,Minneapolis
International Journal for Numerical Methods in Fluids

This paper addresses the critical issue of the accuracy of CFD predictions for wind engineering. Flows around the Silsoe Cube, a high-rise building (the Jin Mao Tower), and a low-rise large-span building (the Pudong International Airport) are computed with the Navier-Stokes solver FENSAP and compared with measurements. Computations are carried out for two wind directions, by solving the steady-state ensemble-averaged Navier-Stokes equations with the Spalart-Allmaras one-equation turbulence model. Pressure coefficients compare well with wind tunnel experiments and the accuracy of the flow solutions is further improved via an automatic mesh adaptation that dynamically places grid points where the flow physics require them, while keeping the number of unknowns and solution time substantially at the same level. Copyright © 2009 John Wiley & Sons, Ltd. Source

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