Aircraft Junction Fairing Vortex Drag Reduction

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Subsonic low-wing aircrafts experience increased drag due to shock waves and induced vortices at the airfoil-fuselage junction fairing, particularly when flying at speeds close to the speed of sound.

Innovation Solution

The integration of at least two vortex generating devices under the junction fairing, which generate attenuating vortices that counteract the induced vortices caused by airflow, thereby reducing drag.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If the aircraft flies at speeds close to the speed of sound, then the air flow around the wings moves into a transonic state generating shock waves, but the drag of the aircraft increases by generating wave drag

Engineering Contradiction:

Improveflight speedVSAvoidwave drag

Core Design Contradiction:

SpeedVSObject-affected harmful factors

Solution Approach 1:

The patent converts the harmful induced vortices into beneficial attenuating vortices by introducing vortex generating devices that create counter-rotating vortices. These attenuating vortices neutralize the harmful effects of the induced vortices, reducing viscous drag. Similarly, the fairing geometry is designed to manage shock waves by creating specific flow patterns that reduce wave drag, effectively converting the harmful transonic flow conditions into more favorable aerodynamic characteristics.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent changes the geometric parameters of the junction fairing, specifically designing the horizontal profile with a concave intermediate segment and convex front and rear segments. This geometric parameter change modifies the flow field characteristics, reducing the intensity of induced vortices and managing shock wave formation. The specific curvature and positioning of these segments are optimized to attenuate vortices while maintaining structural integrity and aerodynamic efficiency.

Inventive Principle:

Principle #35Parameter changes

2Shape

If the air flow around the junction fairing generates induced vortices, then the air flow follows the fairing shape, but the viscous drag of the aircraft increases

Engineering Contradiction:

Improveair flow patternVSAvoidviscous drag

Core Design Contradiction:

ShapeVSObject-affected harmful factors

Solution Approach 1:

The patent converts the harmful induced vortices into beneficial attenuating vortices by introducing vortex generating devices that create counter-rotating vortices. These attenuating vortices neutralize the harmful effects of the induced vortices, reducing viscous drag. The fairing geometry is designed to manage shock waves by creating specific flow patterns that reduce wave drag, effectively converting the harmful transonic flow conditions into more favorable aerodynamic characteristics.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

Instead of trying to eliminate the induced vortices directly, the patent introduces vortex generating devices that create vortices with opposite rotation direction. This inverted approach uses counter-rotating vortices to cancel out the harmful induced vortices, effectively reducing viscous drag through rotational inversion rather than direct suppression.

Inventive Principle:

Principle #13The other way round (Inversion)

3Ease of manufacture

If the outer surface of the junction fairing is designed to minimize aerodynamic interactions with the airfoil, then the junction line profile is slightly convex and nearly straight, but the drag reduction potential is limited

Engineering Contradiction:

Improvefairing design simplicityVSAvoidaerodynamic drag

Core Design Contradiction:

Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs curved surfaces instead of straight lines in the fairing design. The horizontal profile features convex and concave segments with specific curvatures that guide the airflow smoothly and reduce vortex intensity. This curvilinear geometry optimizes aerodynamic performance by creating favorable flow patterns that reduce drag while maintaining ease of manufacture through standardized curvature profiles.

Inventive Principle:

Principle #14Spheroidality (Curvature)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The solution effectively reduces the drag of the aircraft by attenuating induced vortices, leading to improved aerodynamic performance and reduced fuel consumption.

Implementation Method 1

at least two vortex generating devices extending from the lower portion of the outer surface of the junction fairing on both sides, respectively of the median longitudinal plane. The vortex generating devices situated under the junction fairing generate an attenuating vortex which attenuates the intensity of the induced vortices

Methodology Applied

Scientific EffectVortex generation: Vortex Generator

Implementation Method 2

The air flow around the junction fairing during the movement of the aircraft generating at least two induced vortices induced on both sides, respectively, of the median longitudinal plane

Methodology Applied

Scientific EffectInduced vortices: Kármán Vortex Street

Implementation Method 3

the airflow around the junction fairing gives rise to induced vortices also increasing the viscous drag of the aircraft

Methodology Applied

Scientific EffectViscous drag: Drag

Implementation Method 4

the air flow around the wings of the aircraft moves into a transonic state, generating shock waves on the convex side or even, in some cases, on the concave side, which increase the drag of the aircraft by generating what is commonly called a 'wave drag'

Methodology Applied

Scientific EffectShock waves: Shock Wave

Data Source

PatentUS12214864B2Aircraft portion with a reduced drag

Publication Date: 2025.02.04 DASSAULT AVIATION SA

AI summary

An aircraft portion with reduced drag includes a wing-fuselage junction fairing at the interface between the wing and the fuselage. The junction fairing has an outer surface including two lateral portions each covering the root of a respective wing, and a lower portion connecting the side portions to each other and extending under the fuselage. The flow of air around the junction fairing during the movement of the aircraft generates at least two vortices induced on both sides, respectively, of a median longitudinal plane. The aircraft portion also includes at least two vortex generating devices extending from the lower portion of the outer surface of the junction fairing on both sides, respectively, of the median longitudinal plane.