Motor Vehicle Mirror Jet Flow Control for Drag Reduction
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Solution Overview
Problem
External side view mirrors on motor vehicles create significant aerodynamic drag and noise due to their shape, leading to increased fuel consumption and reduced fuel efficiency, particularly in smaller vehicles, as they protrude into the oncoming airflow and cause vortex shedding and turbulent pressure fluctuations.
Innovation Solution
The implementation of a low drag low noise device that uses passive jet flow control to create directed jets of air around the rear of the mirror, mimicking a virtual trailing edge or 'boat-tail' to counteract base flow and reduce vortex shedding, thereby minimizing drag and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external side view mirrors are used for vehicle operation, then the driver can observe side and rear traffic conditions, but the mirror creates significant aerodynamic drag and noise that reduces fuel efficiency
Solution Approach 1:
The patent changes the geometric parameters of the mirror by adding a tapered rear section that transitions from the mirror housing to a smaller diameter end. This parameter change creates a more aerodynamic shape that reduces drag while maintaining the mirror's observational function
Solution Approach 2:
The patent applies curvature by designing the mirror with a tapered, rounded rear section instead of flat or sharp edges. This spheroidal transition reduces flow separation and vortex shedding, thereby reducing drag and noise while preserving the mirror's utility
2Ease of manufacture
If traditional flat-backed mirror shapes are used, then manufacturing is simple, but vortex shedding and turbulent pressure fluctuations create high drag and noise
Solution Approach 1:
The patent replaces the flat back surface with a tapered, curved surface that smoothly transitions to a rounded end. This curvature eliminates sharp edges that cause flow separation and vortex shedding, reducing harmful aerodynamic effects while remaining manufacturable
Solution Approach 2:
Instead of adding complex active flow control systems to reduce drag, the patent inverts the approach by modifying the passive geometry of the mirror itself. The tapered shape inherently reduces vortex shedding without requiring additional active components, simplifying the overall system
3Device complexity
If the mirror has a streamlined front surface but abruptly terminates in a flat back, then the mirror structure is simple, but base flow conditions create high drag forces
Solution Approach 1:
The patent segments the mirror structure into distinct zones: a streamlined front section for observational function and a tapered rear section for aerodynamic performance. This segmentation allows each zone to be optimized for its specific function while maintaining overall structural simplicity
Solution Approach 2:
The tapered rear section uses curved, spheroidal geometry to smoothly guide flow around the mirror and reduce base flow effects. This curvature eliminates abrupt terminations that cause flow separation and high drag, while adding minimal complexity to the overall structure
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 effectively reduces both drag and noise by altering the airflow around the mirror, enhancing fuel efficiency and reducing the deceleration of smaller vehicles, while also increasing base pressure and minimizing vortex shedding.
Implementation Method 1
uses passive jet flow control to create directed jets of air around the rear of the mirror
Implementation Method 2
reduce vortex shedding, thereby minimizing drag and noise
Implementation Method 3
high turbulent pressure fluctuations and vortex shedding create drag, noise
Data Source
AI summary
Low drag low noise devices are described herein that use passive jet flow control to reduce the drag and noise created by devices (e.g., motor vehicle side view mirrors) while the devices travel through fluid. The low drag low noise devices described herein comprise a lengthwise axis, an outer body, and an inner body. The outer body and the inner body cooperatively define a channel through which fluid can pass during use.