Vehicle Mirror Shell Aero-Acoustic Edge Design
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Solution Overview
Problem
Side mirrors with narrow aerodynamic zones often induce whistling at certain vehicle speeds due to self-sustaining vortices in the aerodynamic constricted zone, and existing solutions like foam insertion are ineffective or costly.
Innovation Solution
A shell design with a non-rectilinear rear reattachment line and an 'aero-acoustic edge' that disrupts the regularity of turbulent flow, distributing energy over a wide frequency band to prevent audible whistling, eliminating the need for foam and maintaining a high aerodynamic coefficient.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a narrow aerodynamic zone is used in the side mirror design, then the aerodynamic coefficient SCx is reduced, but whistling occurs due to self-sustaining vortices in the aerodynamic constricted zone
Solution Approach 1:
The invention introduces an asymmetric discontinuity in the rear reattachment line of the aerodynamic constricted zone. This asymmetry disrupts the regular vortex formation that causes whistling, while preserving the overall narrow aerodynamic zone configuration that achieves low SCx values.
Solution Approach 2:
The invention converts the harmful regular vortex flow into beneficial irregular flow patterns by introducing controlled discontinuities. The discontinuities scatter the vortex energy across different frequencies and locations, transforming the concentrated whistling noise into distributed turbulence that is inaudible.
2Object-generated harmful factors
If foam is inserted to block the free space between shell and frame, then whistling may be reduced, but the solution is ineffective when foam is incorrectly positioned and expensive to implement
Solution Approach 1:
The invention extracts the noise control function from the foam material and implements it directly into the shell's geometric structure. The discontinuity in the rear reattachment line is built into the shell design itself, eliminating the need for separate foam insertion steps and associated positioning challenges.
Solution Approach 2:
The shell structure itself provides the noise control function through its inherent geometric discontinuity. The design is self-contained and does not require additional materials or components, making it self-sufficient for both aerodynamic performance and noise reduction.
3Object-generated harmful factors
If foam is used to eliminate whistling, then noise may be reduced, but the effectiveness varies with weather conditions and foam positioning is critical
Solution Approach 1:
Instead of using foam to block and absorb sound waves, the invention inverts the approach by using geometric discontinuities to actively disrupt vortex formation at its source. This structural approach is inherently more reliable as it does not depend on material placement precision or environmental conditions affecting foam properties.
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 eliminates whistling in side mirrors without significantly reducing the aerodynamic coefficient, reducing costs by eliminating the need for foam and ensuring a quieter driving experience.
Implementation Method 1
the non-rectilinear character of the rear reattachment line L2 advantageously destroys the regularity of the turbulent flow which is located under the boundary layer in the aerodynamic constricted zone
Implementation Method 2
the non-rectilinear character of the rear reattachment line L2 advantageously destroys the regularity of the turbulent flow which is located under the boundary layer
Implementation Method 3
the top edge serves to take off the air which comes from the front of the vehicle so that it falls back into the aerodynamic tight zone, so as to allow a notable reduction in the aerodynamic coefficient SCx
Data Source
Figure 1~2
Figure 3~4
AI summary
A shell (CO) of a vehicle lateral rear-view mirror (R) comprises a capital ridge (AS), on the one hand, extended rearward by a terminal part (PT) secured to, and extended rearward by, a frame (CD) to which a mirror is secured and, on the other hand, able to cause the air to detach from it so that it drops back into a region known as the aerodynamic narrowing region (ZR) situated on the terminal part (PT) and the frame (CD). This shell (CO) comprises, upstream of the capital ridge (AS), an upward discontinuity (DC) which has a shape capable of causing the air to detach so that it drops back substantially upstream of the capital ridge (AS) along a non-rectilinear intermediate reattachment line (L1) so that this air is then detached by the capital ridge (AS) and drops back along a non-rectilinear rear reattachment line (L2) situated in the aerodynamic narrowing region (ZR) so that it does not produce any audible whistle.