Abstract
This paper presents an unsteady flow analysis of a 3D wing with a morphing trailing edge flap (TEF) and a seamless side-edge transition between the morphed and static parts of a wing by introducing an unsteady parametrization method. First, a 3D steady Reynolds-averaged Navier–Stokes (RANS) analysis of a statically morphed TEF with seamless transition is performed and the results are compared with both a baseline clean wing and a wing with a traditional hinged flap configuration at a Reynolds number of 0.7 × 106 for a range of angles of attack (AoA), from 4° to 15°. This study extends some previous published work by examining the inherent unsteady 3D effects due to the presence of the seamless transition. It is found that in the pre-stall regime, the statically morphed wing produces a maximum of a 22% higher lift and a near constant drag reduction of 25% compared with the hinged flap wing, resulting in up to 40% enhancement in the aerodynamic efficiency (i.e., lift/drag ratio). Second, unsteady flow analysis of the dynamically morphing TEF with seamless flap side-edge transition is performed to provide further insights into the dynamic lift and drag forces during the flap motions at three pre-defined morphing frequencies of 4 Hz, 6 Hz, and 8 Hz, respectively. Results have shown that an initially large overshoot in the drag coefficient is observed due to unsteady flow effects induced by the dynamically morphing wing; the overshoot is proportional to the morphing frequency which indicates the need to account for dynamic morphing effects in the design phase of a morphing wing.
Highlights
The aircraft industry has been under increasing pressure to move towards “Greener and Quieter” aircraft design through various frameworks, such as FlightPath 2050 [1].modern aircrafts are reaching near peak levels of aerodynamic efficiency making any further improvement of current configuration a daunting task, if not impossible
All of the studies surveyed to date have simplified the wing morphing to be a statically morphed wing configuration, thereby overlooking the dynamic effects that deforming motion of the trailing-edge flap (TEF) might have on the flow field and its subsequent contribution to the airframe noise
The aerodynamic performance of a dynamically morphing TEF is investigated for three morphing frequencies of 4 Hz, 6 Hz and 8 Hz to understand their impacts on the aerodynamic performance
Summary
The aircraft industry has been under increasing pressure to move towards “Greener and Quieter” aircraft design through various frameworks, such as FlightPath 2050 [1].modern aircrafts are reaching near peak levels of aerodynamic efficiency (such as lift-to-drag ratio) making any further improvement of current configuration a daunting task, if not impossible. Designers have been striving to re-imagine the presentday aircraft by employing innovative technologies, such as adaptive morphing structures for flight optimisation and flow control [2,3,4]. The use of morphing lifting surfaces for in-flight flow control can result in considerable drag reduction during the cruise [15,16,17], given the fact that a morphing trailing-edge flap (TEF) will seal the flap side-edge gaps, eliminating small pockets that are known for their high vorticity and for being a significant source of airframe noise [18]. The enhancement in the wing efficiency arising from the possible reduction of drag would contribute directly to a reduction of specific fuel consumption [7,8] and to the sustainability of future aircraft, paving the way to zero carbon emission goals for aviation, and for applications in other fields, especially in renewable energy generation applications, such as wind energy (morphing wind turbines [19]) or tidal energy, where morphing blades could help to mitigate unsteady thrust while sustaining the mean harvested power [20]
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