Boundary-Layer Stability of a Natural-Laminar-Flow Airfoil

2020 ◽  
Author(s):  
Koen J. Groot ◽  
Ethan S. Beyak ◽  
Daniel Heston ◽  
Helen L. Reed
Keyword(s):  
Boundary Layer ◽  
Laminar Flow ◽  
Boundary Layer Stability ◽  
Natural Laminar Flow

Boundary-Layer Stability of a Natural-Laminar-Flow Airfoil at Flight Conditions

2020 ◽  
Author(s):  
Koen J. Groot ◽  
Ethan S. Beyak ◽  
Daniel T. Heston ◽  
Helen L. Reed
Keyword(s):  
Boundary Layer ◽  
Laminar Flow ◽  
Boundary Layer Stability ◽  
Natural Laminar Flow

A 3D Shape Design and Optimization Method for Natural Laminar Flow Nacelle

2017 ◽  
Author(s):  
Yongjian Zhong ◽  
Songyang Li
Keyword(s):  
Boundary Layer ◽  
Simulated Annealing ◽  
Laminar Flow ◽  
Drag Coefficient ◽  
Frictional Drag ◽  
Initial Shape ◽  
Aerodynamic Shape ◽  
Profile Line ◽  
Adaptive Simulated Annealing ◽  
Natural Laminar Flow

With the rapid development of high bypass ratio turbofan engine, the proportion of the nacelle drag increases obviously in the total drag of the aircraft with the increase of nacelle surface area. And the frictional resistance is one of the major contributors of drag. Under the same Reynolds number, the friction resistance in turbulent boundary layer is about 10 times larger as that in laminar boundary layer. Therefore, a correctly profiled engine nacelle will delay the transition in the boundary layer and allow laminar flow to extend back, resulting in a substantial drag reduction. In the previous conference paper (9th reference), a 2D nacelle longitudinal profile-line geometry generator, which allows curvature and slope-of-curvature to be continuous was developed and presented. This established an optimization system to minimize nacelle frictional drag. One of the nacelle profile-line is optimized to achieve minimum drag coefficient, and then is stacked with the other original profile-lines to form the 3D isolated nacelle aerodynamic shape. Finally, a total 23% of nacelle outer surface maintains a laminar flow and its frictional drag coefficient is less than initial shape. This paper proposes a new 2D nacelle longitudinal profile-line design method, based on PARSEC parameterization, with can generate the profile-line rapidly and precisely. Conservation Full Potential Equation was used to calculate the aerodynamic distribution and obtain the transition location. Then adaptive simulated annealing genetic algorithm was adapted to search 2D profiles of low drag, which would be applied to narrow down design space in 3D nacelle optimization. Second, 2D profiles were stacked circumferentially, by NURBS surface generator, to form the 3D nacelle aerodynamic shape, and an optimization system was established, in combination with the 3D nacelle generator, γ–Reθ transition model, Kriging surrogate model and adaptive simulated annealing algorithm, for natural laminar flow nacelle design. Finally, a total 34% of nacelle surface maintains a laminar flow and its frictional drag coefficient is less than initial shape. The generated optimized loft was evaluated by CFD to determine if the low drag of this optimized nacelle shape can be maintained under different Mach numbers and angles of attack.

The Flight Testing of Natural and Hybrid Laminar Flow Nacelles

1994 ◽  
Author(s):  
Brian Barry ◽  
Simon J. Parke ◽  
Nicholas W. Bown ◽  
Hansgeorg Riedel ◽  
Martin Sitzmann
Keyword(s):  
Boundary Layer ◽  
Laminar Flow ◽  
Aircraft Engine ◽  
Flight Test ◽  
Boundary Layer Transition ◽  
Future Application ◽  
Flight Testing ◽  
Layer Transition ◽  
Suction System ◽  
Natural Laminar Flow

The achievement of large areas of laminar flow over aircraft engine nacelles offers significant savings in aircraft fuel consumption. Based upon current engine configurations nett sfc benefits of up to 2% are possible. In addition the engine nacelle is ideally suited to the early inclusion of laminar flow technology, being relatively self contained with the possibility of application to existing airframes. In September 1992 a European Consortium managed by Rolls-Royce including MTU and DLR began flight testing of a natural laminar flow nacelle. This programme was later extended by R-R and DLR to flight test a hybrid laminar flow nacelle featuring boundary layer suction and insect contamination protection. The tests evaluated the effects of flight and engine environment, boundary layer transition phenomena, suction system operation and insect contamination avoidance strategies. This paper describes the global conclusions from these flight tests which are a significant milestone leading to the future application of laminar flow technology to engine nacelles.

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