Experimental Investigation of a Flexible Wing with a Variable Camber Continuous Trailing Edge Flap Design

Abstract

This paper presents experimental results of a flexible wing wind tunnel model with a variable camber continuous trailing edge flap (VCCTEF) design for drag minimization, tested at the University of Washington Aeronautical Laboratory (UWAL). The wind tunnel test was designed to explore the relative merit of the VCCTEF concept for improved cruise efficiency through the use of low-cost aeroelastic model test techniques. The flexible wing model is a 10%-scaled model of a typical transport wing and is constructed of woven fabric composites and foam core. The wing structural stiffness in bending is tailored to be half of the stiffness of a Boeing 757-era transport wing, while the torsional stiffness is about the same. This stiffness reduction results in a wing tip deflection of about 10% of the wing semi-span. The VCCTEF is a multi-segment flap design having three chordwise camber segments and five spanwise flap sections for a total of 15 individual flap elements. The three chordwise camber segments can be positioned appropriately to create a desired trailing edge camber. Elastomeric material is used to cover the gaps in between the spanwise flap sections, thereby creating a continuous trailing edge. Wind tunnel data indicate a high degree of data correlation and repeatability. The VCCTEF can achieve a drag reduction of up to 6.31% and an improvement in the lift-to-drag ratio (L/D) of up to 4.85%. The paper also presents two methods for estimating the lift coefficient of a rigid wing using a dynamic pressure correction and an aeroelastic deflection correction. Both methods provide good estimates of the rigid-wing lift coefficient.

Static Aeroelastic Modeling of a Sub-Scale Wind Tunnel Model with Novel Flap Concept

“…6 The wind tunnel test results showed a drag reduction of up to 6.31% and an improvement in lift-to-drag ratio (L/D) of up to 4.85% for the configurations tested. 7 A previous study constructed an aeroelastic model based on a computational fluid dynamic (CFD) Euler code called CART3D that showed agreement with wind tunnel results. 8 This paper outlines the development and validation of a static aeroelasticity model based upon the sub-scale model of the wing with VCCTEF tested at UWAL.…”

“…Collated information summarizing the wind tunnel test results are found in references. 6,7 Figure 6 is a photo of the model being tested in the UWAL wind tunnel. …”

Aeroelastic Analysis of Wind Tunnel Test Data of a Flexible Wing with a Variable Camber Continuous Trailing Edge Flap (VCCTEF)

“…The nominal dynamic pressure is 20 psf. The full report of the wind tunnel test data analysis is published by Nguyen et al 13 For summary, only test data for FLAP0 configuration is shown. The lift curve and drag polar for the baseline FLAP0 configuration are plotted in Figs.…”

“…13 The aeroelastic deflection correction method yields the highest estimated rigid-wing lift coefficient. Since there are some differences in the three estimated rigid wing lift coefficients, an average rigid wing lift coefficient is computed and is shown in Fig.…”

“…Figure 40 is the lift curve of the rigid baseline FLAP0 configuration. For comparison, the rigid wing lift curves of the baseline FLAP0 configuration computed by Euler CFD code Cart3D 10 and estimated from the UWAL wind tunnel test data by the dynamic pressure and the aeroelastic deflection correction methods 13 are also plotted. It can be seen that Vorlax under-predicts lift for the rigid wing UWAL wind tunnel model by some amount.…”