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Croce G.,University of Udine | De Candido E.,University of Udine | Habashi W.G.,McGill University | Munzar J.,McGill University | And 4 more authors.
Journal of Aircraft | Year: 2010

Ice roughness, which has a major influence on in-flight icing heat transfer and, hence, ice shapes, is generally input from empirical correlations to numerical simulations. It is given as uniform in space, while sometimes being varied in time. In this paper, a predictive model for roughness evolution in both space and time during in-flight icing is presented. The distribution is determined mathematically via a Lagrangian model that accounts for the stochastic process of bead nucleation, growth, and coalescence into moving droplets and/or rivulets and/or water film. This general model matches well the spatial and temporal roughness distributions observed in icing tunnel experiments and is embedded in FENSAP-ICE, extending its applicability outside the range of airfoil types for which correlations exist. Thus, an additional important step has been taken toward removing another empirical aspect of in-flight icing simulation. Copyright © 2010 by W.G. Habashi.


Zhang Y.,McGill University | Zhang Y.,Computational Fluid Dynamics Laboratory | Habashi W.G.,McGill University | Habashi W.G.,Computational Fluid Dynamics Laboratory | And 3 more authors.
Journal of Aircraft | Year: 2016

This paper presentsamultiscale finite-element formulation for the second modeofzonal detached-eddy simulation. The multiscale formulation corrects the lack of stability of the standard Galerkin formulation by incorporating the effect of unresolved scales to the grid (resolved) scales. The stabilization terms arise naturally and are free of userdefined stability parameters. Validation of the method is accomplished via the turbulent flow over tandem cylinders. The boundary-layer separation, free shear-layer rollup, vortex shedding from the upstream cylinder, and interaction with the downstream cylinder are well reproduced. Good agreement with experimental measurements gives credence to the accuracy of zonal detached-eddy simulation in modeling turbulent separated flows. A comprehensive study is then conducted on the performance degradation of ice-contaminated airfoils. NACA 23012 airfoil with a spanwise ice ridge and Gates Learjet Corporation-305 airfoil with a leading-edge horn-shape glaze ice are selected for investigation. Appropriate spanwise domain size and sufficient grid density are determined to enhance the reliability of the simulations. A comparison of lift coefficient and flowfield variables demonstrates the added advantage that the zonal detached-eddy simulation model brings to the Spalart-Allmaras turbulence model. Spectral analysis and instantaneous visualization of turbulent structures are also highlighted via zonal detached-eddy simulation. Copyright © 2015 by the CFD Lab of McGill University. Published by the American Institute of Aeronautics and Astronautics, Inc.


Cinquegrana D.,Centro Italiano Ricerche Aerospaziali | Cinquegrana D.,Computational Fluid Dynamics Laboratory
Journal of Spacecraft and Rockets | Year: 2015

In the early stage of a reentry vehicle design are often necessary tools able to perform mission and trajectory trade studies. Many works in the literature present tools able to interpolate from a numerical database of high-fidelity simulations to a target free-stream condition. In this context, the work explores the capability of a reduced-order model in extending a limited database of computational fluid dynamics simulations to the full coverage of the design space. This results in a fast physic-based tool able to generate load history experienced on a vehicle's surface during the reentry flight. The reduced-order model is based on proper orthogonal decomposition coupled with a Gaussian process for interpolations. Main results are the history of the pressure and skin-friction coefficient of a reference trajectory related to a specific vehicle's control points. This output will be compared with a simple Gaussian metamodel based directly on the computational fluid dynamics data of such control points. A detailed cross-validation analysis of the model that provides a loss function map in the design space can be considered as a guide to in-fill the database with further computational fluid dynamics simulations, keeping the number of computational fluid dynamics runs at a minimum value to limit the computational budget. Copyright © 2015 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.


Nilamdeen S.,McGill University | Nilamdeen S.,Computational Fluid Dynamics Laboratory | Habashi W.G.,McGill University | Habashi W.G.,Computational Fluid Dynamics Laboratory
Journal of Propulsion and Power | Year: 2011

The presence of ice crystals at high altitudes has been hypothesized to be the cause of a recent series of sudden highaltitude turbofan engine malfunctions. Ice crystals do not accrete on external surfaces, but when entering the core flow, they experience higher temperatures as they move downstream. They may melt on a heated surface or stick on a wetted interface to locally reduce the temperature and initiate ice accretion on both static and rotating components that could result in compressor surge, vibrational instabilities, mechanical damage through shedding of ice fragments, or performance losses and an eventual flameout if ice enters the combustor. As a first step toward providing a comprehensive numerical tool to analyze such situations, this paper develops a model for mixed-phase flows that combines air, water, and ice crystals and the related ice accretion. Within the dearth of experimental results, the extended ice crystal impingement and ice accretion model has been validated against test data on a NACA0012 airfoil and an unheated nonrotating cylinder. Copyright © 2011 by the American Institute of Aeronautics and Astronautics, Inc.


Badcock K.J.,University of Liverpool | Badcock K.J.,Computational Fluid Dynamics Laboratory | Woodgate M.A.,University of Liverpool | Woodgate M.A.,Computational Fluid Dynamics Laboratory
AIAA Journal | Year: 2010

Computational aeroelasticity has become an active area of research in the past decade. Effort has been put into coupling between computational fluid dynamic and finite element solvers and into model reduction to make the resulting simulations more useful for practical analysis. This paper is the latest in a series that describe research toward making eigenvalue-based stability analysis routine for large-scale computational-fluid-dynamic-based semidiscrete systems. The particular contribution of this paper is to formulate the problem in a framework that exploits the Schur complement. This effectively allows the different parts of the system Jacobian to be treated in a decoupled way, with the final result being a small nonlinear eigenvalue problem for the stability analysis. The calculation of this small system can be done robustly in parallel. Results to illustrate the performance of the method are presented for model wings and full aircraft test cases.


Timme S.,University of Liverpool | Timme S.,Computational Fluid Dynamics Laboratory | Badcock K.J.,University of Liverpool | Badcock K.J.,Computational Fluid Dynamics Laboratory
AIAA Journal | Year: 2011

A hierarchy of flow models is exploited for transonic aeroelastic stability analysis using the kriging interpolation technique applied within the Schur complement eigenvalue framework. In the Schur framework, a modified structural eigenvalue problem describes the coupled aeroelastic system with a precomputed interaction term depending on the response frequency. The interaction term, representing the influence of the high-dimensional computational fluid dynamics system, is approximated by reconstruction based on samples that can be computed using a frequency or time domain solver. The computationally cheap approximation model is developed and discussed in this paper for two-degree-of-freedom aerofoil cases. The approximation model is used for both the parametric blind search of aeroelastic instability and for updating predictions based on aerodynamic models of different fidelities. © 2011.


Timme S.,University of Liverpool | Timme S.,Computational Fluid Dynamics Laboratory | Marques S.,University of Liverpool | Marques S.,Computational Fluid Dynamics Laboratory | And 2 more authors.
AIAA Journal | Year: 2011

A method is described to allow searches for transonic aeroelastic instability of realistically sized aircraft models in multidimensional parameter spaces when computational fluid dynamics are used to model the aerodynamics. Aeroelastic instability is predicted from a small nonlinear eigenvalue problem. The approximation of the computationally expensive interaction term modeling the fluid response is formulated to allow the automated and blind search for aeroelastic instability. The approximation uses a kriging interpolation of exact numerical samples covering the parameter space. The approach, demonstrated for the Goland wing and the multidisciplinary optimization transport wing, results in stability analyses over whole flight envelopes at an equivalent cost of several steady-state simulations. © 2011 by the authors.


Pellissier M.P.C.,McGill University | Pellissier M.P.C.,Computational Fluid Dynamics Laboratory | Habashi W.G.,McGill University | Habashi W.G.,Bombardier | Pueyo A.,Bombardier
Journal of Aircraft | Year: 2011

This paper presents a methodology for the optimization of hot-bleed-air anti-icing systems, known as Piccolo tubes. Such systems are widely used to anti-ice the wings of many commercial aircrafts, ranging from regional to wide-body jet aircrafts. Having identified the most critical in-flight icing conditions, as well as any anti-icing system constraints as inputs, the ideal aim is to achieve fully-evaporative conditions over the heated surfaces. To do so, an optimization method based on three-dimensional computational fluid dynamics, reduced-order models, and genetic algorithms was constructed to determine the optimal geometric configuration of the Piccolo tube (jet angles, spacing of jets, and distance from leading edge). The external and internal airflows are computed using the finite element Navier-Stokes applications package (FENSAP-ICE). The methodology leads to significantly-improved configurations for three- to five-dimensional design spaces. Copyright © 2010 byWagdi G. Habashi. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission.

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