Shock Bumps for Transonic Drag Reduction
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Solution Overview
Problem
Existing aerodynamic structures face challenges in maintaining optimal shock wave location at varying flight conditions, leading to increased wave drag, which is difficult to address without adding weight and complexity through variable camber systems.
Innovation Solution
The use of a series of shock bumps distributed along a line with a smaller mean angle of sweep than the unperturbed shock, which 'un-sweep' the shock and form a stepped plan-form shape with lambda-like wave patterns, reducing the angle of sweep and maintaining optimal operation across different flight conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If trailing edge variable camber is deployed to modify aerofoil shape and shock location, then shock wave position can be optimized, but weight and systems complexity increase
Solution Approach 1:
The wing surface is segmented into multiple discrete shock bumps distributed along a line with smaller mean angle of sweep. Each bump independently perturbs the shock wave, collectively achieving shock location control without requiring a complex variable camber system. This segmentation approach replaces a continuous complex mechanism with discrete, simpler elements.
Solution Approach 2:
Instead of modifying the entire aerofoil shape through variable camber, local quality is applied by placing shock bumps at specific locations along the wing surface. The bumps create localized perturbations that collectively control the shock wave position, allowing optimization without global structural changes or additional weight.
2Reliability
If shock bumps are distributed along the unperturbed shock line, then shock control is achieved, but the shock moves away from optimal location as flight conditions vary
Solution Approach 1:
Instead of placing shock bumps along the unperturbed shock line (traditional approach), the invention inverts the approach by distributing bumps along a line with a smaller mean angle of sweep. This unconventional arrangement causes the perturbed shock to maintain a more consistent relationship with the bumps across varying Mach numbers and lift coefficients, improving adaptability to different flight conditions.
3Device complexity
If fixed shock bump positions are used, then device complexity is reduced, but optimal shock location cannot be maintained across varying flight conditions
Solution Approach 1:
The invention changes the geometric parameters of the shock bump distribution - specifically using a line with smaller mean angle of sweep instead of the unperturbed shock line. This parameter change allows fixed-position bumps to effectively control the shock wave across a broader range of flight conditions, maintaining reliability without requiring variable geometry or complex control systems.
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 solution reduces wave drag by stabilizing the shock wave location independently of wing shape and span load distribution, eliminating the need for variable camber systems and maintaining optimal performance across varying flight conditions.
Implementation Method 1
At transonic speeds a swept shock forms normal to the upper surface of the wing
Implementation Method 2
Shock/boundary layer interaction control using 3D devices
Data Source
AI summary
An aerodynamic structure (1) comprising a series of shock bumps (3a, 3b, 3c) extending from its surface. The shock bumps are distributed along a line (7) with a smaller mean angle of sweep than an unperturbed shock (4) which would form adjacent to the surface during transonic movement of the structure in the absence of the shock bumps. Instead of being distributed along the line of the unperturbed shock, the shock bumps are distributed along a line which is less swept than the mean angle of sweep of the unperturbed shock. When the structure is moved at a transonic speed; a shock forms adjacent to its surface and the shock bumps perturb the shock (9) so as to reduce its angle of sweep.