Angled Duct Fairing Assembly for Drag Reduction
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Solution Overview
Problem
Aircraft fluid duct outlet ports often face design compromises that prevent them from being oriented parallel to the surface, leading to increased drag and noise due to recirculation of fluid flows, especially at high angles, and existing solutions like Coanda fairings and vortex generators either fail to effectively turn high-velocity flows or induce significant drag and noise.
Innovation Solution
An angled duct outlet fairing assembly comprising a vane fairing with a sloped ramp, a Coanda fairing, and a pair of vortex generators positioned on opposing lateral sides, which together direct and organize the fluid flow to minimize recirculation and drag by aligning it with the surface flow, effectively reducing turbulence and drag.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the duct outlet is oriented at a higher angle with respect to the surface flow, then the mechanical simplicity of the duct design is improved, but drag and noise increase due to recirculation of fluid flows
Solution Approach 1:
A fairing assembly is introduced as an intermediary component between the angled duct outlet and the surface flow. The fairing includes a Coanda surface and vortex generators that mediate the interaction between the high-velocity duct flow and the surface flow, organizing the mixing process to reduce recirculation, drag, and noise while allowing the duct to maintain its mechanically simple angled orientation
Solution Approach 2:
The invention uses fluid dynamic principles including the Coanda effect and vortex generation to control and organize the fluid flow. The fairing leverages pneumatic/hydraulic mechanisms where the duct flow itself is used to generate vortices and attach to the Coanda surface, converting the harmful high-velocity jet into organized flow that reduces drag and noise
2Stability of the object's composition
If a Coanda fairing is used to turn the angled duct flow, then the flow attachment to the surface is improved, but the device complexity and length requirements increase significantly
Solution Approach 1:
The invention merges multiple functions into a single integrated fairing assembly that combines a Coanda surface, vortex generators, and flow organizing structures. This unified approach achieves flow attachment and drag reduction in a compact configuration that is less than three duct diameters in length, avoiding the need for separate, lengthy components
Solution Approach 2:
The fairing incorporates a Coanda surface with specific curvature that allows the high-velocity duct flow to attach and follow the surface smoothly. The curved geometry of the Coanda surface is optimized to promote flow attachment while maintaining a compact overall structure that does not require excessive length
3Stability of the object's composition
If vortex generators are used to organize the recirculating flow, then the flow organization is improved, but drag and noise increase significantly
Solution Approach 1:
Vortex generators are placed only in specific localized regions where they are most effective - at the leading edge of the fairing and at strategic positions to generate vortices that promote flow attachment. This localized placement avoids the need for extensive vortex generator coverage that would otherwise create excessive drag and noise
Solution Approach 2:
The vortex generators are designed with specific geometric parameters (size, angle, spacing) that are optimized to generate appropriate vortex strength for organizing the flow. By carefully controlling these parameters, the vortex generators effectively organize recirculating flow while minimizing their own drag and noise contribution
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 fairing assembly significantly reduces turbulence and drag by organizing the fluid flow, improving thrust and reducing noise, while maintaining mechanical simplicity and efficiency across varying duct relative velocities.
Implementation Method 1
The use of the Coanda effect to turn airflow has been in wide use for many years. The Coanda effect allows a fluid flow to follow a curved surface, such as on the flaps of a wing
Implementation Method 2
The use of vortex generators to circulate organized flow to reduce or eliminate areas of recirculation is also well-known in the art for controlling a flow of a fluid
Data Source
AI summary
A fairing assembly is provided about a duct outlet port, which is not parallel to an exterior surface of a vehicle, so as to turn fluid flow exiting the duct outlet port in a direction of surface fluid flow. The fairing assembly includes an upstream vane fairing to orient the surface flow with the angled duct flow, a downstream Coanda fairing to turn transverse duct flow in the direction of the surface flow, and a pair of vortex generators each of which is positioned at an opposing lateral side of the Coanda fairing and angled towards each other to organize the combined fluid flow downstream of the duct outlet port to thereby minimize recirculation. This fairing assembly about the duct outlet port enhances organized mixing of the duct and surface flows, and thereby reduces duct and surface recirculation, duct restriction, and overall vehicle drag.