Aircraft Active Flow Control Using Sequential Vortex Actuation
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Solution Overview
Problem
Current aircraft wing designs face challenges in maintaining attached flow at varying flight conditions, particularly during takeoff and landing when high-lift devices like slats and flaps are required, and existing active flow control methods using cooperative actuators can exhibit destructive behavior when vortices are introduced at different actuation sites.
Innovation Solution
A method for active flow control that generates a first vortex structure at a location and introduces a second vortex structure downstream, using flow control actuators to create local velocity fields, allowing the second vortex to be energized and remain stable over a long distance by introducing it into the high-velocity field of the first vortex, rather than the boundary layer, thereby preventing flow separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple vortex structures are introduced at different actuation sites to amplify vorticity and duration, then the flow control effectiveness is improved, but the vortices may exhibit destructive behavior and reduce reliability
Solution Approach 1:
The first vortex structure is introduced upstream before the second vortex structure is introduced downstream. This preliminary action ensures that the first vortex is already established and can serve as a stable high-velocity field for the second vortex, preventing destructive interference while amplifying the overall flow control effectiveness.
Solution Approach 2:
The first vortex structure acts as an intermediary between the actuation system and the boundary layer. By introducing the second vortex into the high-velocity field of the first vortex rather than directly into the boundary layer, the system achieves amplified vorticity without destructive behavior, effectively using the first vortex as a mediator.
2Reliability
If conventional high-lift devices like slats and flaps are used to prevent flow separation, then flow attachment is maintained, but the device complexity and weight increase
Solution Approach 1:
The invention extracts the flow separation prevention function from mechanical high-lift devices and implements it through fluidic actuators that introduce vortex structures. This removes the need for complex mechanical slats and flaps, reducing device complexity and weight while maintaining flow attachment through active flow control.
Solution Approach 2:
The patent replaces the mechanical system of slats and flaps with a fluid-based active flow control system. Instead of moving mechanical surfaces to control flow, vortex structures are introduced through fluidic actuators, substituting mechanical action with fluid dynamic effects to achieve flow attachment.
3Duration of action of moving object
If vortices are introduced directly into the boundary layer, then flow energization occurs, but the vortex stability and duration are limited
Solution Approach 1:
The first vortex structure is introduced upstream in advance, creating a stable high-velocity field before the second vortex is introduced downstream. This preliminary establishment of the first vortex provides a favorable environment that extends the duration and enhances the stability of the overall vortex system.
Solution Approach 2:
The first vortex structure serves as an intermediary high-velocity field that receives the second vortex. By introducing the second vortex into this pre-established high-velocity field rather than directly into the boundary layer, the vortex stability and duration are significantly enhanced, as the intermediary field provides additional energy and reduces dissipation.
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
This approach provides a robust and reliable solution for active flow control, reducing the need for high-lift devices like slats and enhancing the stability and energy of vortices to prevent flow separation over a longer distance, making it effective across varying flight conditions.
Implementation Method 1
controlling the first flow control actuators to generate a first vortex structure in a fluid flow
Implementation Method 2
energize the boundary layer of the flow to prevent flow separation
Implementation Method 3
a local velocity field is generated upstream of the head vortex which propagates downstream with the fluid flow
Implementation Method 4
introducing a second vortex structure into the first local velocity field, when a head vortex of the first vortex structure has propagated with the fluid flow downstream the row of second openings
Data Source
Figure 1~2
Figure 3(A)~3(F)
Figure 4(D)~5(C)
AI summary
A method for active flow control of a fluid flow that flows along a flow surface includes generating a first local velocity field in the fluid flow by introducing a first vortex structure into the fluid flow by means of a first flow control actuator coupled to a first actuation site of the flow surface, and introducing a second vortex structure into the first local velocity field by means of a second flow control actuator coupled to a second actuation site of the flow surface located downstream of the first actuation site, when a head vortex of the first vortex structure has propagated with the fluid flow downstream the second actuation site.