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A computational study was conducted to evaluate the effectiveness of using a viscous flow solution in an ice accretion code and the resulting accuracy of aerodynamic performance prediction. Ice shapes were obtained for one single-element and one multi-element airfoil using both potential flow and Navier-Stokes flowfields in the LEWICE ice accretion...
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... This suite of tools is used to prepare two-dimensional cross sections of iced airfoils for computational fluid dynamics (CFD) analysis. SmaggIce is designed to help researchers and engineers study the effects of ice accretion on airfoil performance, which is difficult to do with other software packages because of the complexity of ice shapes 3 . CFD tools are used primarily for certification studies and analysis, to evaluate safety of flight with unprotected surfaces and to determine the need for ice protection. ...
In the present work, LEWICE-based ice-shape prediction results are presented when coupled to a computational fluid dynamics (CFD) model using a discrete-element roughness method (DERM) prediction of heat transfer. The DERM is a subgrid-scale model for CFD that accounts for the momentum and heat transfer aspects of large-scale roughness that displays an improvement of the heat transfer predictions beyond those of traditional sand-grain-roughness (SGR) models. The CFD-DERM approach is used to replace the built-in heat transfer prediction module of LEWICE for a multistep ice-shape prediction. Comparisons of ice-shape predictions and aerodynamics are made between the experiment, SGR-LEWICE, and DERM-LEWICE to evaluate the benefit of an improved heat transfer prediction methodology. The results indicate that the DERM model provides an improved prediction of heat transfer relevant to ice roughness. Additionally, ice-shape predictions in the glaze-icing regime are shown to be sensitive to the convective heat transfer prediction method. However, the improved heat transfer prediction does not necessarily correlate to an improved ice-shape prediction.
The paper presents the developments of novel mesh generation algorithms over complex glaze-ice shapes containing multicurvature ice-accretion geometries, such as single/double ice horns. The twofold approaches tackle surface geometry discretization as well as field mesh generation. First, an adaptive curvilinear curvature control algorithm is constructed, solving a one-dimensional elliptic partial differential equation with periodic source terms. This method controls the arc length grid spacing, so that high convex and concave curvature regions around ice horns are appropriately captured, and is shown to effectively treat the grid shock problem. Second, a novel blended method is developed by defining combinations of source terms with two-dimensional elliptic equations. The source terms include two common control functions, Sorenson and Spekreijse, and an additional third source term to improve orthogonality. This blended method is shown to be very effective for improving grid quality metrics for complex glazeice meshes with Reynolds-averaged Navier-Stokes resolution. The performance in terms of residual reduction per nonlinear iteration of several solution algorithms (point-Jacobi, Gauss-Seidel, alternating direction implicit, point, and line Successive Over-Relaxation) are discussed within the context of a full multigrid operator. Details are given on the various formulations used in the linearization process. It is shown that this performance of the solution algorithm depends on the type of control function used. Finally, the algorithms are validated on standard complex experimental ice shapes, demonstrating the applicability of the methods. © Copyright 2015 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.
In order to study the influence of ice accretion, in this paper, the equations of motion of water droplets are established by Lagrange method. The mass and energy balance equations are solved by Messinger model. The predicted curves are compared with the experiment curves, and the results are consistent. The influence of flight parameters and atmospheric parameters on the results of icing on the surface, indicate that the ice-type changes are caused by flight speed. Other parameters such as icing time and LWC affect the amount of icing, but little effect on the ice type. Icing on the surface makes the roughness of the lifting surface increase and the characteristics of lift and drag of airfoil deteriorate significantly. By studying the aerodynamic characteristics of the airfoil after icing, the results show that the lift coefficient significantly decreases and the drag coefficient increases with the icing time increasing. Under the same conditions, increasing the flight speed can significantly improve the aerodynamic characteristics of the aircraft.
In-flight ice accretion, even though driven by a steady flow airstream, is an inherently unsteady phenomenon. It is, however, completely ignored in icing simulation codes (one-shot) or, at best approximated via quasi-steady modeling (multishot). The final ice shapes thus depend on the length of the total accretion time (one-shot), or of the arbitrarily prescribed time intervals (multishot), during which the impact of ice growth on both airflow and water impingement is ignored. Such a longstanding heuristic approximation is removed in this paper by coupling in time the dilute two-phase flow (air and water droplets flow) with ice accretion, and is implemented in a new code, FENSAP-ICE-Unsteady. The two-phase flow is solved using the coupled Navier-Stokes and water concentration equations, and the water film characteristics and ice shapes are obtained from laws of conservation of mass and energy within the thin film layer. To continually update the geometry of the iced surface in time, arbitrary Lagrangian-Eulerian terms are added to all governing equations to account for mesh movement in the case of stationary components. In the case of rotating/stationary interacting components, a dynamically stitched grid is used. The numerical results clearly show that unsteady modeling improves the accuracy of both rime and glaze ice shape prediction, compared with the traditional quasi-steady approach with frozen solutions. The unsteady model is shown to open the door for a unified approach to icing on fixed wings, on helicopters with blades/rotors/fuselage systems. Problems of current concern in the icing community such as the ingestion of ice crystals at high altitude become tractable with the new formulation.
The present study assesses a multi-step procedure to perform quasi-3D ice accretion simulations for a 22.5 min failed ice protection system condition. This procedure is based on a 2D ice accretion code (Lewice 2D - LEWINT) to predict the ice growth along a two-dimensional section of a three-dimensional body. The solution of gaseous phase of the external flow is obtained through a commercial RANS solver using the SA turbulence model. The water collection efficiency is obtained using an Eulerian scheme and, for each new time increment on the ice accretion simulation process, the computational mesh is re-generated and the external flow updated using patched mesh concept. The results of the simulated ice shapes for a 3D swept wing for an icing exposure time of 22.5 min (divided in 5 time steps of 270 seconds) are compared to the experimental ice shapes. In addition, results obtained using different numerical approaches are presented as well. These approaches are: Lewice 2D stand alone (potential flow solution for the external flow) for 5 times steps, Lewice 2D stand alone using automatic time step and Aeroicing 2D using a single step. The results achieved for the failed ice protection system case showed good overall agreement in terms of horn's vertical extent, angle and location, however, ice shape horizontal extent related to the wing leading edge showed to be poorly predicted. Copyright © 2012 American Institute of Aeronautics and Astronautics, Inc.
