Gustavo E. C. Fujiwara

A Hybrid Airfoil Design Method for Icing Wind Tunnel Tests

.Modern commercial aircraft wings are far too large to be tested full-scale in existing icing wind tunnels and ice accretion scaling methods are not practical for large scale factors. Thus the use of hybrid scaling techniques, maintaining full-scale leading-edges and redesigned aft sections, is an attractive option for generating full-scale leading-edge ice accretions. The advantage lies in utilizing reduced chord models that minimize blockage effects in the icing tunnels. The present work discusses the design of hybrid airfoils with large scale factors that match the ice shapes of the full-scale airfoils predicted by LEWICE. Assessments of the effects of scale factor, extent of the full-scale leading-edge, nose droop angle, zero-angle of attack pitching moment coefficient (Cm0), and droplet size are also presented. Hybrid or truncated airfoils are shown to produce ice shapes accurately, even at angles of attack different from the design angle of attack with the proper application of either flap, adjusted test angle of attack, or both. Further results suggest that hybrid circulation does not need to match full-scale circulation in order to match ice shapes, resulting in decreased loading for higher scale factor hybrid airfoils. Matching the flowfield around the hybrid airfoil to the full-scale flowfield provided a superior method for predicting ice shape agreement, stagnation point location being a first order and suction peak magnitude a second order parameter. This goal can be accomplished by varying the aft geometry, through Cm0 and nose droop angle.

3D Swept Hybrid Wing Design Method for Icing Wind Tunnel Tests

A 3D swept hybrid wing design method using hybrid airfoils is presented for the purpose of icing wind tunnel testing of large commercial aircraft. Hybrid airfoils are those that present the same leading-edge geometry of the full-scale aircraft wing with a redesigned truncated aft section, such that models can fit inside icing wind tunnels and still reproduce full-scale flowfield and ice accretion with reduced chord. The effects of tunnel sidewalls, model sweep angle, aspect ratio, and wind tunnel blockage are presented. Attachment line location is used as a first-order parameter for matching full-scale ice shapes, and methods for controlling its spanwise variation are assessed including the use of gap between model and tunnel wall, aerodynamic twist, and segmented flaps. Finally, model design tradeoffs are presented between competing performance parameters such as full-scale ice accretion agreement, wind tunnel load/speed limits, and model manufacturing/operational complexity.

Computational and Experimental Ice Accretions of Large Swept Wings in the Icing Research Tunnel

A comparison of computational and experimental ice accretions is presented for three full-scale leading edge swept-wing models spanning from floor to ceiling in the NASA Glenn Icing Research Tunnel (IRT) at three different spanwise stations of the 65%-scale Common Research Model. Experimental ice shapes were generated on the leading edge of each model for a set of icing conditions, and then digitized with a 3D laser scanner. Computational simulations were done for the same flow and icing conditions of the experiment, utilizing CFD (OVERFLOW 3D RANS) for the flowfield solutions, and LEWICE3D for the 3D ice accretion calculations. Results showed both good ice accretion agreement and the need to further explore and better understand the complex 3D flowfield and ice accretion modeling.

Large-Scale Swept-Wing Icing Simulations in the NASA Glenn Icing Research Tunnel Using LEWICE3D

Computational icing simulations of a hybrid, swept-wing model in the NASA IRT are presented. The results of these simulations are compared to those for the same icing conditions conducted on the full-scale reference wing. The effects of tunnel sidewalls, attachment line position, and altitude are considered. A discussion of icing scaling and the results of one scaling approach are given. The variation of impingement and ice shape with span in the tunnel for different angles of attack and flap deflection are presented.

Aerodynamic Modeling of Transonic Aircraft Using Vortex Lattice Coupled with Transonic Small Disturbance for Conceptual Design

The need to rapidly scan large design spaces during conceptual design calls for computationally inexpensive tools such as the vortex lattice method (VLM). Although some VLM tools, such as Vorview have been extended to model fully-supersonic flow, VLM solutions are typically limited to inviscid, subcritical flow regimes. Many transport aircraft operate at transonic speeds, which limits the applicability of VLM for such applications. This paper presents a novel approach to correct three-dimensional VLM through coupling of two-dimensional transonic small disturbance (TSD) solutions along the span of an aircraft wing in order to accurately predict transonic aerodynamic loading and wave drag for transport aircraft. The approach is extended to predict flow separation and capture the attenuation of aerodynamic forces due to boundary layer viscosity by coupling the TSD solver with an integral boundary layer (IBL) model. The modeling framework is applied to the NASA General Transport Model (GTM) integrated with a novel control surface known as the Variable Camber Continuous Trailing Edge Flap (VCCTEF).

Adaptive Aeroelastic Wing Shape Optimization for High-Lift Configurations

A rapid conceptual 3D aerostructural tool was developed for multidisciplinary optimization of flexible wings in high-lift configurations, such as takeoff and landing. In order to allow fast optimization while still capturing nonlinear aerodynamic phenomena such as the maximum lift near the stall, a hybrid 2D/3D aerodynamic approach was used by combining 3D linear vortex lattice method with known 2D airfoil viscous data. A two-variable ”decambering” method was employed to match the sectional lift and pitching moment coefficients along the wing span with that of the corresponding 2D viscous data, in a multivariable Newton-Raphson iterative scheme. Validation was done against experimental data of a straight wing with known both 3D and 2D experimental data, demonstrating successful prediction of lift, stall progression along the wing span, and decrease in pitching moment due to stall. The aerodynamic tool was coupled with a structural finite element method code to compute static aeroelastic deflections of a given wing, and subsequently integrated with an optimization routine. The resulting aeroelastic optimization framework was then applied to a low-Reynolds simplified version of the Generic Transport Model with variable camber continuous trailing-edge flaps, in high-lift configuration, to predict the optimal flap schedule for maximum lift. Results showed that for a rigid wing, the optimal flap deflection corresponded to a lift distribution similar to the chord distribution, while a flexible wing was dependent on its torsional and bending stiffness. For the wing stiffness and dynamic pressure utilized, the optimal flap deflection schedule showed to be similar to the rigid wing results, differing slightly by having a less loaded wing tip region, to avoid the observed outboard nose-up torsion tendency that would prematurely stall the wingtip.

Method for Designing Hybrid Airfoils for Icing Wind-Tunnel Tests

The certification of modern commercial aircraft requires manufacturers to demonstrate flight safety under various scenarios, including icing conditions. Although computational tools play a key role...