3D Woven Lattice Surfaces for Passive Bluff-Body Drag Reduction
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Solution Overview
Problem
Current technologies for reducing aerodynamic drag in vehicles are either inefficient, costly, or prone to performance degradation when damaged, and existing methods for drag reduction, such as active systems or permeable surfaces, have limitations in terms of adaptability and durability.
Innovation Solution
A three-dimensional woven lattice material is developed for passive and active flow control, which can be applied to various geometries, changing fluid flow boundary conditions from no-slip to partial slip, and optimizing permeability to reduce drag, turbulence, and noise through spatial distribution and directional control of wires or yarns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If active drag reduction technology such as plasma actuators or synthetic jet arrays is used, then drag reduction is achieved, but cost and complexity increase substantially
Solution Approach 1:
The patent employs passive permeable surfaces made from cost-effective materials such as porous foams, meshes, or fabrics that can be easily manufactured and replaced. These surfaces provide drag reduction through their inherent permeability structure without requiring complex active systems, electrical power, or sophisticated control mechanisms, thereby achieving drag reduction while minimizing cost and complexity
Solution Approach 2:
The invention utilizes permeable surfaces with controlled porosity to enable flow through the surface, which modifies boundary layer characteristics and reduces drag. The porous structure allows fluid penetration and flow redistribution, achieving drag reduction passively without complex mechanisms, thus resolving the contradiction between drag reduction performance and system complexity
2Object-affected harmful factors
If riblets or bumps, compliant walls, splitter plates, wavy or rough surfaces are used for drag reduction, then drag is reduced under design conditions, but efficiency significantly reduces if damaged or operated off-design
Solution Approach 1:
The patent employs permeable surfaces with adjustable permeability parameters that can adapt to different flow conditions. The permeable structure maintains its drag reduction function across a wide range of Reynolds numbers and flow regimes, and remains effective even when damaged, as the distributed porous structure continues to provide flow control benefits, thereby achieving both drag reduction and reliability
Solution Approach 2:
The permeable surface provides self-regulating flow control by allowing the fluid to naturally penetrate and flow through the porous structure according to pressure gradients. This passive mechanism requires no external control systems and automatically adapts to varying flow conditions, maintaining drag reduction performance reliably whether operated at design conditions or off-design, and continues to function even when damaged
3Object-affected harmful factors
If permeable surfaces are used to reduce drag, then flow regularization and drag reduction are achieved, but the mechanism and optimal configuration require further determination
Solution Approach 1:
The patent applies permeable surfaces with spatially varying permeability characteristics tailored to specific flow regions. By optimizing the local permeability, porosity, and thickness of the permeable surface in different locations, the design achieves enhanced drag reduction and flow regularization while providing clear manufacturing guidelines for creating optimized configurations
Solution Approach 2:
The permeable surface design serves multiple functions simultaneously: drag reduction, flow regularization, turbulence control, and protection against flow separation. This multi-functional approach simplifies the optimization process by providing a single versatile solution that addresses multiple flow control objectives, making the configuration easier to manufacture and implement across different applications
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 3D woven lattice material effectively reduces drag by up to 42% and turbulence intensity, while maintaining structural integrity and adaptability, making it suitable for diverse applications including vehicles and wind turbines, with potential for energy savings and reduced maintenance costs.
Implementation Method 1
Permeable sheath changes no-slip and zero tangential velocity boundary condition to a quasi-slip Fourier type boundary due to the Darcy-like flow inside the porous layer
Implementation Method 2
Porous sheath also enables internal flow from the high pressure (flow facing region) to the leeside of the body with lower pressure
Data Source
AI summary
The present invention is directed to three dimensional (3D) woven lattices for drag and turbulence reduction. 3D woven lattice material can serve as a surface layer that regularizes the flow around a bluff body with beneficial effects on: 1) drag reduction, 2) decrease in turbulence intensity, 3) attenuation of flow-induced vibrations, and 4) aerodynamic noise cancellation. 3-D woven lattice architectures allows for passive flow control (without the need for external energy supply) around bluff bodies with restricted geometry/shape due to their functional requirements such as wind turbine towers, cargo trucks, train cars, etc. The woven material can be easily shaped to fit on various geometries and incorporated in existing manufacturing processes (from composites to metallic plates). Metallic foam and randomly porous materials have been identified in the literature as a promising solution for passive flow control over bluff bodies.