Cruise Slotted Wing Design with Natural Laminar Flow for Transonic Commercial Transport Aircraft

LANGLEY RESEARCH CENTER

Cruise Slotted Wing Design with Natural Laminar Flow

for Transonic Commercial Transport Aircraft

Brett Hiller, Richard Campbell, and Michelle Banchy NASA Langley Research Center AIAA SciTech Forum, January 2025 Copyright 2025 United States Government as represented by the Administrator of the National Aeronautics and Space Administration. No copyright is claimed in the United States under Title 17, U.S. Code. All Other Rights Reserved. Published by the American Institute of Aeronautics and Astronautics, Inc. with permission.

LANGLEY RESEARCH CENTER

Outline

• Introduction • Geometry and Design Conditions • Computational Tools and Design Constraints • Design Results • Concluding Remarks 2025 AIAA SciTech 2

LANGLEY RESEARCH CENTER

Cruise Slotted Wing Technology

Concept The Cruise Slotted Wing (CSW) is a transonic multielement wing concept with a forward main element and an aft flap element, separated to form an intermediate slot.

Design Advantage Flow-through slot permits stronger pressure recovery without separation, enables greater aft loading to help reduce shock strength and pressure drag 2025 AIAA SciTech 3

LANGLEY RESEARCH CENTER

Research History

Objective

Quantify the potential vehicle performance benefits of CSW technology

in application to next-generation, single-aisle transonic commercial transports

with cruise speeds near Mach 0.8

2D Airfoil Design 3D ALMA Wing Design 3D NLF Wing Design

Slotted Wing with Slotted Wing with Aft Laminar Multielement Airfoil (ALMA) Natural Laminar Flow (NLF) flap NLF flap and wing upper surface 2.7% profile drag reduction comparable drag as conventional comparing to conventional relative to supercritical airfoil supercritical wing supercritical and NLF wing NLF Flap Laminar Flow Laminar Flow AIAA Paper 2021-2525 AIAA Paper 2024-0677 Current Paper 2025 AIAA SciTech 4

LANGLEY RESEARCH CENTER

Geometry and Design Conditions

Baseline Conventional Wing Mach-0.8 variant of the Common Research Model (CRM-M8) created for a representative single-aisle, transonic transport aircraft model CRM-M8 Conventional Wing Baseline Cruise Slotted Wing MAKESLOT code creates partial-span, slotted wing geometry from conventional wing Features common fuselage and inboard wing, outboard slotted wing with main element and flap CRM-M8 Cruise Slotted Wing 2025 AIAA SciTech 5

LANGLEY RESEARCH CENTER

Computational Tools

Design Station 2025 AIAA SciTech 6

LANGLEY RESEARCH CENTER

CDISC Target Pressures

Reduced shock strength C * P

Design

Station

Increased aft loading

2025 AIAA SciTech 7

LANGLEY RESEARCH CENTER

Cruise Performance: Laminar Flow Extents

M = 0.8, Re = 21.1 million, C = 0.543

cref L NLF Area – Upper Surface = 53% NLF Area – Upper Surface = 61% NLF Area – Lower Surface = 0% NLF Area – Lower Surface = 10% Total NLF Area = 27% Total NLF Area = 35% NLF Conventional Wing NLF Cruise Slotted Wing Turbulent Conventional Wing

Slotted wing architecture enables increased extents (+8%) of

NLF surface area due to laminarization of aft flap element

2025 AIAA SciTech 8

LANGLEY RESEARCH CENTER

Cruise Performance: Drag Decomposition

M = 0.8, Re = 21.1 million, C = 0.543 cref L • Relative to turbulent conventional wing , the NLF conventional wing reduces the total drag by 18.4 ct • The NLF slotted wing achieves additional 1.4-ct drag reduction relative to the NLF conventional wing • ~0.8 ct viscous drag reduction • ~0.6 ct pressure drag reduction 2025 AIAA SciTech 9

LANGLEY RESEARCH CENTER

Off-design Performance: Drag Polar

M = 0.8, Re = 21.1 million 𝛂𝛂 = 3.5˚, C ≈ 0.73 cref L NLF CSW reduces shock-induced separation at higher 𝛂𝛂 +15% in L/D compared to conventional turbulent wing near buffet criterion (1.3*C ) L,cruise +5% in L/D compared to conventional NLF wing near buffet criterion 2025 AIAA SciTech 10

LANGLEY RESEARCH CENTER

Off-design Performance: Drag Rise

C = 0.543, Re = 21.1 million M = 0.85 L cref NLF CSW reduces shock-induced separation at higher Mach numbers +20% in L/D compared to conventional turbulent wing at M = 0.85 +9% in L/D compared to conventional NLF wing at M = 0.85 2025 AIAA SciTech 11

LANGLEY RESEARCH CENTER

Concluding Remarks

• Cruise Slotted Wing with Natural Laminar Flow designed for Mach-0.8 variant of the CRM – Achieved 8% increase in NLF surface area compared to conventional NLF wing • 19.8 drag count reduction rel. to conventional turbulent wing • 1.4 drag count reduction rel. to conventional NLF wing – Limits shock-induced separation at off-design conditions Cruise Slotted Wing with Natural Laminar Flow for Mach-0.8 variant of the CRM • Future Research Opportunities – Design trade space exploration • Increased speed  reduced travel time • Increased wing thickness  lighter wing – Continued industry interest, potential to examine performance benefits for alternative configurations • Transonic truss-braced wing NASA/Boeing SUGAR • Transonic business jet Transonic Truss-braced Wing (TTBW ) Photo: NASA 2025 AIAA SciTech 12

Contact: Brett Hiller <brett.hiller@nasa.gov>