T Junction Flow Obstacle Concavity Drag Reduction
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Solution Overview
Problem
The T junction of a flow obstacle on a wall bounding a flow, such as in an airplane, results in additional drag due to the formation of a horse shoe vortex, which increases the overall drag beyond the sum of the individual drags of the wing and flat-plate configurations.
Innovation Solution
A concavity in the wall neighboring the flow obstacle, starting upstream and terminating downstream of the obstacle, reduces the peak vorticity of the horse shoe vortex by creating a pocket for it to stabilize, thereby decreasing drag through increased boundary layer thickness and reduced viscous dissipation, and counter-rotating vortices that minimize shear and momentum loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a T junction configuration is used (wing attached to fuselage), then the airplane structure is formed, but additional interference drag is generated due to horse shoe vortex formation
Solution Approach 1:
The invention applies curvature by introducing a concavity (curved surface) in the fuselage wall at the T junction area. This concave shape modifies the flow pattern around the wing-fuselage intersection, reducing the intensity of the horse shoe vortex and thereby decreasing interference drag. The curved surface guides the boundary layer flow more smoothly around the junction.
Solution Approach 2:
The invention changes the geometric parameters of the fuselage surface by introducing a concavity with specific dimensions (depth, length, and position). By adjusting these parameters, the flow characteristics at the T junction are modified to reduce vortex strength and associated drag. The concavity creates a region that alters pressure distribution and boundary layer behavior.
2Object-generated harmful factors
If the concavity is extended further downstream, then the horse shoe vortex stabilization is improved, but the concavity length increases
Solution Approach 1:
The invention applies partial action by extending the concavity only to the extent necessary to achieve effective vortex stabilization. The concavity length is optimized to provide sufficient downstream extension to stabilize the horse shoe vortex without unnecessary elongation. This balances drag reduction benefits with the added geometric complexity and potential impact on other aerodynamic characteristics.
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 concavity design effectively reduces interference drag by stabilizing the horse shoe vortex and minimizing momentum loss, leading to lower drag and improved aerodynamic performance at the T junction.
Implementation Method 1
The flow along the wall forms a boundary layer. When the boundary layer encounters the flow obstacle large enough to stop a part of the flow on the leading edge of the obstacle, an adverse pressure gradient is caused which results in a reversal and a separation of the flow.
Implementation Method 2
The flow along the wall forms a boundary layer. When the boundary layer encounters the flow obstacle large enough to stop a part of the flow on the leading edge of the obstacle, an adverse pressure gradient is caused which results in a reversal and a separation of the flow. Due to the separation of the flow, the boundary layer rolls up and forms what is known as a horse shoe vortex.
Data Source
Figure 1~2
Figure 3~4
AI summary
A T junction (1) of a flow obstacle (6) on a wall (3) bounding a flow having a main flow direction (5) comprises a concavity (7) of the wall (3) neighboring the flow obstacle (6). The concavity (7) terminates at a first distance (11) downstream the flow obstacle (6) and starts at a second distance (9) upstream the flow obstacle (6).